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Pre-Launch Activities and the Crewman Change Journal Home Page Day 1, part 2: Earth Orbit and Translunar Injection

Apollo 13

Apollo 13 patch

Day 1, part 1: Launch and Reaching Earth Orbit


Corrected Transcript and Commentary Copyright ©2016-2020 by W. David Woods, Johannes Kemppanen, Alexander Turhanov and Lennox J. Waugh. All rights reserved.
Last updated 2020-04-21
Apollo 13 is the third attempt by the United States to perform a manned landing on the Moon. The mission's destination, in the highlands near the crater Fra Mauro, reflects the Apollo programme's increasing emphasis on science. Two of the crew, Commander Jim Lovell and Lunar Module Pilot Fred Haise, plan to bring their Lunar Module Aquarius down to a precision landing near a 370-metre crater called Cone. This crater acts like a drill hole, the physics of its formation allowing subsurface material to be sampled around its rim and, hopefully, giving insight into the Moon's geological history. One week before launch, the third crewmember, Command Module Pilot Jack Swigert, was on the backup crew when prime CMP Ken Mattingly was exposed to German measles. Mattingly did not have immunity to the disease so to avoid the possibility of him becoming sick during the mission, he was replaced by his backup only two days before launch.
The reconstituted crew of Apollo 13, photographed the day before the launch date of Friday, 11 April 1970.
The launch day is Saturday, 11 April 11 1970. The planned time of launch is 19:13:00 GMT which, at Kennedy Space Center (KSC), will be 14:13:00 EST. The launch azimuth, which is the heading that the vehicle's ground track will take away from the launch pad, is 72° or about east-northeast.
Apollo 13 will be launched in the April launch window to the Moon. The launch window for the chosen day, 11 April, opens at 14:13:00 EST which is exactly the planned moment of their launch. It will remain open until 17:37:00 EST. Should Apollo 13 fail to launch in April, backup dates are set in May, with three days from 9 to 11 May as launch opportunities.
A launch window is a time determined to be optimal for the launch of a space vehicle so that it can reach its destination, given certain constraints, of which Apollo has many. A daytime launch is preferred, since it would aid in crew recovery should they need to abort during the launch. The launch trajectory azimuth restriction from 72° to 108° dictates this time as well. It is desirable to perform the translunar injection burn over the Pacific Ocean for communication reasons. The landing should occur when sunlight conditions on the surface of the Moon are favourable for the crew to view their landing site. A very large antenna capable of tracking the lunar landing is located in Goldstone, California and it would be preferable to time the landing so that this antenna is pointing at the Moon at that time, which adds its own limitation. Finally, daytime conditions for the primary recovery area during their scheduled return are needed for safe recovery of the crew after they splash down.
Launch operations will be conducted in a standard manner, familiar from previous Apollo launches. However, special attention is being paid to weather conditions due to the lightning strike incident during the launch of Apollo 12. Great care has been taken to ensure that the launch will not take place should the weather suggest the possibility of thunder or triggering lightning by flying the Saturn V into it.
Saturn V vehicle illustration. Modification of original by JK.
The Apollo 13 space vehicle, consisting of the mighty Saturn V launch vehicle and the Apollo 13 spacecraft, has awaited launch at Pad 39A since December 15, 1969, when the Mobile Launcher carried it from the Vehicle Assembly Building (VAB) to the launch site.
As the transcript starts, the Saturn V is already fully fuelled. Only relatively small amounts are being pumped into the tanks to continue topping them off to compensate for the boil-off of extremely volatile cryogenic propellants. This ensures that the tanks contain the expected quantity of liquid at launch. The first stage, the S-IC, is loaded with 815,113 litres of RP-1 kerosene fuel, along with 1,318,621 litres of liquid oxygen (LOX) oxidizer. The thirst of the first stage engines is astonishing. The contents of the first stage liquid oxygen tank alone compose one half of the total mass of the Saturn V stack. In comparison, the propellant levels in the other two stages seem tiny. The S-II second stage carries 1,030,919 litres of liquid hydrogen (LH2) fuel and 333,930 litres of liquid oxygen. The similarly liquid hydrogen/liquid oxygen-fuelled third stage carries 242,815 litres and 76,571 litres respectively.
This fully fuelled Apollo/Saturn V, AS-508, is the heaviest space vehicle yet. Its mass stands at 2,949,136 kilograms, or 6,501,733 pounds. The first stage engines must overcome its weight to lift the Saturn V vehicle off the pad and head it to space. Only 1.5 per cent of all this mass consists of the crew and its two spacecraft stacked one on top of another - and even then, most of that remaining 1.5 per cent is the fuel loaded in the Service Module and the two-stage Lunar Module!
This is Apollo Saturn Launch Control; T minus 3 hours, 49 minutes, 57 seconds and counting. We've received word now from the crew quarters that Colonel Tom Stafford of the astronaut office is in fact [garble] the prime crew right as scheduled [garble] 58 AM. From there the crew proceeded to the area where they will receive their brief physicals this morning. There, Dr. John Teegan and Dr. Alan Harter from the Manned Spacecraft Center, Launch Site Medical Operations Branch will give them their brief physicals. From the physical they will - where they are right now, they'll report down for their breakfast. It will be the traditional breakfast of steak and eggs. In the meantime, the launch crew has completed the liquid hydrogen loading, which completes cryogenic loading. From now on we will be in the replenish mode with both, liquid oxygen and liquid hydrogen being replenished down to the final minutes of the countdown. Just a few moments ago we had an updated weather briefing. The weather appears to be satisfactory for launch. The chances of rain seem to be diminishing at this time. There is a stationary front over the Florida / Georgia coast which is bringing in a considerable amount of cloud cover. We'll be expecting temperatures of about 80 degrees Fahrenheit [27°C] at launch time, winds 12 knots from the southeast, and clouds - several cloud layers; one layer from 3,500 to 5,000 feet, another scattered layer at 8 to 9,000, a broken layer at 14,000, and still another cloud cover at 20 to 25,000. These clouds are acceptable for launch. At T-minus 3 hours, 48 minutes, 13 seconds; this is Kennedy Launch Control.
Cryogenic oxygen loading started at T minus 8 hours, 22 minutes and ended at T minus 5 hours, 41 minutes. Liquid hydrogen loading started at T minus 5 hours, 33 minutes and ended at T minus 4 hours, 4 minutes. From then on, both propellants were pumped slowly into the tanks to maintain them at desired levels and make up for any evaporation of the super-cold liquids.
This is Apollo Saturn Launch Control; now T minus 3 hour, 30 minutes and holding. This is a planned, built-in hold built into the count at this time, scheduled to last for 1 hour. Going into our hold, the launch team here in the Launch Control Center actually is running a little bit ahead of schedule. Cryogenic loading has been completed and the close-out crew is now on their way out to the spacecraft to make it ready for the arrival of Commander Jim Lovell, Command Module Pilot Jack Swigert, and Lunar Module Pilot Fred Haise. The three crewmen have just completed their physical examination - a brief physical examination this morning back at the crew quarters. Dr. Teegan reported, "All three men were in real fine shape in this morning's exam. They're in top shape for the mission." Now T-minus 3 hours, 30 minutes and holding; this is Kennedy Launch Control.
The crew underwent medical examinations daily leading up the launch. The one on the morning of 11 April is only a brief one to see any obvious issues that might have arisen overnight.
This is Apollo Saturn Launch Control; we're continuing in our hold at the T minus 3 hour and 30 minute mark. This is a planned hold at this time scheduled to last for 1 hour. The close-out crew has just recently arrived at the 320-foot level. They went across the swing arm to the White Room area and have now opened the hatch of the Command Module, which has been named Odyssey. The backup pilot, Vance Brand, has entered the spacecraft at this time. The close-out crew consists of 6 men. The pad leader, the backup pilot [Vance Brand], a NASA quality control man, two spacecraft technicians, and a suit technician - two suit technicians. The crew busily at work now preparing the Command Module to receive the crew when they're ready to come out. The crew sitting down for breakfast now, they're getting their traditional breakfast of steak and eggs. Actually, getting tenderloin steak, eggs, orange juice, coffee, jelly and toast for breakfast this morning. Continuing in our hold at 3 hours, 30 minutes and holding; this is Kennedy Launch Control.
Vance Brand (1931-) is a selection Group 5 astronaut and part of the support team for Apollo 13. Although identified as a Backup Command Module Pilot, he did not hold such a position officially during the mission. He will later serve as a CapCom throughout the mission.
Apollo 13 crew enjoys the traditional steak breakfast.
The astronauts' breakfast menu is chosen to have a low residue.
This is Apollo Saturn Launch Control; we're continuing in our planned hold at the 3 hour and 30 minutes at this time. The crew is finishing up their breakfast at this time. They had some guests for breakfast: Dr. Anthony England (an astronaut), Colonel Tom Stafford, and Donald K. Slayton. Prior to going to breakfast this morning, the crew had a short physical. Dr. John Teegan (and that's spelled T-e-e-g-a-n) reported, "All three men were in real fine shape in this morning's exam. They're in top shape for the mission." At this time, up at the spacecraft level at Launch Complex 39A, the close-out crew is busily at work with Backup Pilot Vance Brand in the spacecraft going through a varity of checks. He'll spend about 25 minutes in the spacecraft. Once he got into the craft, he turned on the Caution and Warning system, and then began to prepare the water system - this is the drinking water system aboard the spacecraft. He injected chlorine into the system, and operated the water gun. There are a variety of lights on the spacecraft panels which he is, at this time, turning off. He'll also be adjusting the oxygen - this is the breathing oxygen which the crew will use. Also, over some of the switches, above the couches are some safety locks so the switches can't be inadvertently turned on. He's taking off some of these safety switches, now and generally making the spacecraft ready for the arrival of the prime crew. Actually, prior to cryogenic loading, late yesterday, astronaut Brand accompanied by astronaut Tony England went into the spacecraft and went through a spacecraft checklist of checking the various switches and circuit breakers. Our countdown in a hold - in a planned hold, at the T-minus 3 hours, 30 minute mark; this is Kennedy Launch Control.
The backup crew of a mission traditionally would perform the duty of setting up the spacecraft ready for the launch on the night before by making sure that all the onboard control switches were properly configured. For 13, support team astronauts Anthony England and Vance Brand have taken up the duty. Although it is not certain, most probably this was done due to the quick reorganization of the prime and backup crews.
Vance Brand broke the key that opens the protective cover on the Pyro Arm switches, prompting a search for the spare key.
This is Apollo Saturn Launch Control; we're continuing to hold at the 3 hour and 30 minute mark as planned. We have approximately 20 more minutes remaining in this built-in hold. Stoney, which is the capsule communicator - which is the callsign for the capsule communicator here in the Launch Control Center, has just checked in. This is astronaut, Paul Weitz. Also checking in have been the Spacecraft Test Conductor and the Launch vehicle Test Conductor indicating that they're ready for the crew when the crew is ready to depart. Astronauts Haise, Lovell, and Swigert (in that order) entered the suit room just a few moments ago and began the suiting operation. If they stay on schedule, as they have been this morning, they'll be departing from the crew quarters at approximately 11:07 am for the trip out to the pad. Countdown continuing to go well at this time as we remain in our hold at the T-minus 3 hours, 30 minutes and holding, this is Kennedy Launch Control.
Paul J. Weitz (1932-2017), a Group 5 astronaut, works with the launch control crew. His duties include doing the actual countdown to launch the crew hears inside the spacecraft, and operating the elevator from pad level to the white room. Weitz would later fly on the first Skylab crew as a Command Module Pilot, and Command STS-6 space shuttle mission.
A7L Extravehicular Mobility Unit - EMU. Spacesuit.
After getting dressed in their Constant Wear Garment (CWG) underwear and medical sensors, the crewmembers moved into the suiting up area at the crew quarters to begin the cumbersome process of getting inside their handmade, made-to-fit A7L spacesuits; each officially known as an Extravehicular Mobility Unit (EMU). The A7L provides them with a pressurized environment and protection against extreme cold, heat and vacuum, as well as radiation and micrometeoroids.
Commander Jim Lovell suiting up.
Jim is all geared up in his lunar surface suit, topping off weight at 19.69 kilograms or 43.42 pounds. Pockets on his spacesuit are filled with equipment ranging from radiation dosimeters to pencils to checklists - to a sandwich for a post-launch snack.
Technicians wearing the logo of spacesuit maker ILC - International Latex Corporation - on their clean suits snap on the inflatable lifebelt for Command Module Pilot Jack Swigert. He is already hooked up into the oxygen feeds and the comm carrier attached to the port on his chest. Note that Jack is wearing the intravehicular, or IVA, version of the suit meant only for being worn inside the spacecraft, pressurized or not. The main visual difference is the lack of the left hand ports for the PLSS. The intravehicular suit weighs 15.48 kg or 34.13 pounds. The weight difference is mostly due to the lack of the heavier external micrometeroid protection layer.
Lunar Module Pilot Fred Haise is shown relaxing in one of the leather recliners provided for the crewmembers during the suiting up. The dark 'cap' on the left side of his helmet is a contingency feeding port - a vent through which a straw can be pushed in so that the astronaut can consume drinks even while wearing the suit, and in depressurized conditions. This feature was to ensure that the crew could be hydrated and fed in the case of the spacecraft losing cabin pressure and forcing them to make the return trip wearing their suits.
This is Apollo Saturn Launch Control; we're now about 5 minutes away from resuming our countdown at the T-minus 3 hour, 30-minute mark. At this time, the astronaut crew are in the suit room donning their spacesuits back at the Manned Spacecraft Operations Building on Kennedy Space Center. The closeout crew at the pad rapidly preparing the spacecraft and the White Room area to receive the crew. Cryogenic loading was completed before entering this built-in hold. We continue to top off these extremely cold liquid hydrogen and liquid oxygen at this time, and will continue to top off down to the final minutes of the countdown. Also going on at this time are some computer checks. These are check to ensure that the computers here on the ground are properly communicating with the computers aboard the space vehicle, and the proper reactions do take place to the signals being sent. Countdown going well at this time. We'll be standing by to resume the count in approximately 4 minutes from this time. T-minus 3 hours, 30 minutes and holding, this is Kennedy Launch Control.
[Garble] coming out to the pad at approximately 11:07 am EST. It's about an 8-mile ride out to the pad from the crew quarters, and that's expected to take some 15 to 20 minutes. Our weather for a 2:13 pm EST launch continues to be satisfactory. Although it looks quite sunny at the space center at this time, we do expect some clouds to move in and expect the cloud cover at approximately 25 - 2,500 to 5,000 feet. However, these cloud covers will not [garble] any type of deterrent to our launch. The winds are expected to be approximately 12 knots from the southeast; temperature will be a warm 80 degrees [F, 27°C]; and no rain is expected at launch time. Our countdown continuing to move nicely at this time. T-minus 3 hours, 18 minutes, 35 seconds and counting, this is Kennedy Launch Control.
The crew of Apollo 13 boards the Astro Van for transport to the launch pad. They are accompanied by a fireman and a technician carrying a spare oxygen system.
After suiting up, the crew is taken to the launch pad aboard a vehicle, usually dubbed the Astro Van. They are hooked up to suitcase-like portable oxygen supplies (known as ventilators) for the trip until their hoses are connected to the spacecraft's Environmental Control System feeds. This is part of the prebreathing sequence to condition the crew to a 100-per-cent oxygen atmosphere which they will be breathing throughout the mission. Breathing pure oxygen flushes out the nitrogen that is normally part of our breathing air. Should they still have nitrogen in their bloodstream as the pressure onboard the spacecraft drops during ascent, they could suffer from dysbarism - also known as the bends, where bubbles of nitrogen form and cause a painful, debilitating and potentially fatal condition in the human body.
This is Apollo Saturn Launch Control; T-minus 3 hours, 7 minutes, 46 seconds and counting. And at this time the crew has left the suit room and is now entering the transfer van. Apollo 13 Commander Jim Lovell; Command Module Pilot Jack Swigert; and Lunar Module Pilot Fred Haise are now in the transfer van, and they'll start that 8-mile trip out to the launch pad. At the pad, we just heard from astronaut Vance Brand. He has completed all his functions inside the spacecraft and is now awaiting the arrival of the prime crew. The pad leader also reported back that he is ready - they're ready in the the White Room and in the spacecraft to receive the crew. Now T-minus 3 hours, 7 minutes, 9 seconds and counting; this is Kennedy Launch Control.
Apollo 13 crew about to embark their spacecraft in the White Room. They are assisted by Pad Leader Guenter Wendt.
The White Room sits on the end of the topmost service arm on the launch tower. It serves as a place for the crew to enter the spacecraft, and for technicians to perform any final necessary checks and maintenance.
Part of the ritual of boarding the spacecraft was the exchange of gag gifts to break the pre-flight tension. For Apollo 13, Pad Leader Guenther Wendt recalls giving Fred a baby doll and some diapers to practice changing, for his upcoming baby.
This is Apollo Saturn Launch Control; T-minus 2 hours, 44 minutes, 26 seconds and counting. Donald K. Slayton, now in the Firing Room, has indicated that when he was with the crew this morning they were in good spirits and appeared to be completely ready for their flight. The crew in the White Room - the close-out crew is now standing by waiting for the prime crew - the astronaut crew to arrive at the 320-foot level. Once they arrive - once the elevator arrives at that level, the two astronauts, Lovell and Haise will come across the swing arm. And they're coming across now. They arrived at the 320-foot level, and astronaut Lovell is the first one to come across. Lovell will be followed by Haise and one suit technician, the other suit technician will remain in the elevator with the Command Module Pilot Jack Swigert.
General internal arrangement of the Command Module, with crew couches visible.
The crew slips through the side hatch of the spacecraft and then onto the crew couches. The Commander, Jim Lovell, boards first and takes the left couch, followed by Lunar Module Pilot Fred Haise to the right hand one and Command Module Pilot Jack Swigert taking the middle seat. The Commander and the Command Module Pilot will later swap positions to give Jack better access to the controls and the windows for the upcoming docking maneuvers. Whoever sits on the middle seat is practically blind to what happens outside.
In the operations manual, the boarding of the crew into the Command Module is known as Crew Ingress. In the Saturn V manual for the launch operations, it is known as crew loading - an interesting difference in philosophy, but not entirely untrue. They are meant to be passengers for the duration of the activity of the Saturn V.
The two men, now are entering the White Room and they'll now prepare for the ingress. The first one to enter the spacecraft will be the spacecraft Commander Jim Lovell. He'll move into the center seat and over to the far left hand seat. The second one to go in will be the Lunar Module Pilot Fred Haise who will move into the center seat and then across into the right-hand seat. At that time the Command Module Pilot Jack Swigert and a suit technician will come across from their standby position in the elevator, and Swigert will move into the center seat. The crew now preparing for the ingress at T-minus 2 hours and 43 minutes and counting, this is Kennedy Launch Control.
This is Apollo Saturn Launch Control; T-minus 2 hours, 34 minutes, 57 seconds and counting. At this time the spacecraft Commander Jim Lovell is aboard the spacecraft, which they have decided to call Odyssey. Lovell made a communications check just moments ago, asked if he could hear he said, "I can read you loud and clear." He actually entered the spacecraft at 11:32. We have Haise just finishing entering the spacecraft. He moved into the spacecraft at 11:38 and will now be moving over into the right-hand seat. Before entering the spacecraft, the men removed their protective covers which are over their boots. They've been wearing those since they donned their spacesuits this morning. After they move into the couch they get a communications check and hook up to the oxygen, check that out, and then the portable oxygen ventilator is handed out of the spacecraft. As they entered, the Backup Pilot, Vance Brand is at the rear of the spacecraft, assisting them as they get in.
At this moment, Vance Brand remains inside the Command Module to assist the crew in getting onto their seats and also connects their O2 hoses to the Environmental Control System.
Fred Haise performed this duty twice himself, as a backup crewmember on both Apollo 8 and Apollo 11.
Suit oxygen hose system.
Once onboard the spacecraft, the crewmen are plugged into the communications system via cables, and have their oxygen hoses connected from the portable tanks into receptacles on the left hand side of the cabin. The Lunar Module Pilot needs longer hoses for them to reach the connectors on the other side of the cabin.
The spacesuits have their own internal ventilation ducting to move air throughout the suit. This aids cooling, moisture control and makes sure that the oxygen from the system is evenly distributed and flows to the crewmember's face.
This is Apollo Saturn Launch Control; T-minus 2 hours, 30 minutes, 58 seconds and counting. The pad leader indicated that he was now ready for the Command Module Pilot Jack Swigert to come aboard and in fact Swigert has now walked across the swing arm with a suit technician and is in the White Room area preparing to ingress the spacecraft. Now with Swigert and the suit technician there we have a total of 9 men, including the three astronauts and 6 of the close-out crew in the White Room area. This is the maximum that we'll have in there during this close-out period. Now T-minus 2 hours, 30 minutes, 26 seconds and counting; this is Kennedy Launch Control.
This is Apollo Saturn Launch Control; T-minus 2 hours, 28 minutes, 54 seconds and counting. And the last of the three astronauts, the Command Module Pilot Jack Swigert has now gone aboard the spacecraft. We logged him going over the sill at 11:44am EST. Communications check has been established now with both the spacecraft Commander Jim Lovell and the Lunar Module Pilot Fred Haise. Now T-Minus 2 hours, 28 minutes, 29 seconds and counting, this is Kennedy Launch Control.
This is Apollo Saturn Launch Control; T-minus 2 hours, 19 minutes, 57 seconds and counting. At this time, the Spacecraft Test Conductor is going over some switch check positions with the crew inside the spacecraft. Verifying that when they go into the spacecraft they didn't inadvertently trip some of these switches and get them into the wrong position. We have relatively clear skies at Kennedy Space Center at this time, however within the next couple of hours by our 2:13pm EST launch time we're expecting to have some clouds moving in but we do not expect them to be any kind of a problem for our launch today. Earlier worries about rain have disappeared at this time, we're not expecting any rain. The temperatures are expected to be about 80 degrees Fahrenheit [27°C], winds 12 knots from the southeast. Now T-Minus 2 hours, 19 minutes, 9 seconds and counting, this is Kennedy Launch Control.
This is Apollo Saturn Launch Control; T-minus 2 hours, 15 minutes, 30 seconds and counting. At this time, the Spacecraft Test Conductor Skip Chauvin just called to the pad leader indicating that the checkouts have been complete. Once they get Vance Brand, the backup pilot out - and he appears to be coming out at this time - they are cleared to begin closing the hatch - begin closing the hatch on the Command Module called Odyssey. Our countdown moving [garble] ahead of schedule at this time. At 2 hours, 15 minutes, 5 seconds and counting, this is Kennedy Launch Control.
This is Apollo Saturn Launch Control. We're T-minus 2 hours, 12 minutes, 23 seconds and counting. At this time, Vance Brand, the backup pilot is out and the pad leader has just received permission to begin closing the hatch. As they close the hatch they will begin to purge the cabin which has been - being fed with fresh air from a large hose in the White Room. They'll purge the cabin and bring aboard pressurization with a 60/40 mixture of oxygen and nitrogen. The crew inside will continue, of course, to breathe from their oxygen system aboard the spacecraft. Now T-minus 2 hours, 11 minutes, 49 seconds and counting, this is Kennedy Launch Control.
For the launch period, once the hatch is closed, the Command Module is pressurized with a mixture of 60 per cent oxygen and 40 per cent nitrogen. This is a safety measure against the likes of the fire that devastated Apollo 1 in the pad fire due to a spark that ignited the 100-per-cent oxygen atmosphere. The crew is isolated from this atmosphere within their space suits. During the ascent, the cabin will be allowed to vent as the outside pressure falls and a high flow of oxygen will be fed into the cabin to remove the remaining nitrogen and create the 100-per-cent atmosphere to be used for the remainder of the mission. By this time, the cabin pressure will have fallen to just over one third of sea-level pressure.
Although 100-per-cent oxygen carries the risk of increased fire hazard, it has some virtues that make it preferable for use on the Apollo system. Having a single gas atmospheric system reduces its complexity, hence makes it more reliable and lightweight by eliminating the need for multiple sets of pressure regulators and tankage, for example. Having five times the normal amount of oxygen in the breathable air also means that a much lower pressure is used, which puts less strain on the hull of the spacecraft.
Multiple recordings of the mission's audio are available. The most commonly available version is the Public Affairs Office (PAO) feed which carries the air-ground conversation punctuated by explanatory comments from a PAO announcer either at KSC or in Mission Control, Houston. A recording of the direct spacecraft communications for Apollo 13 includes a period of 91 minutes prior to launch when the crew were working with the Launch Vehicle Test Conductor Jack Baltar and the Spacecraft Test Conductor Skip Chauvin to ensure that the Command Service Module (CSM) is ready for the flight. Unfortunately, this latter recording only carries the spacecraft side of the conversation. With the available documentation, however, it is possible to reconstruct the crew activities during this period based on their comments.
Download MP3 audio file. Spacecraft communications.
We join the crew moments after they have entered the Command Module. It is an hour and a half to lift-off and the three-man crew is busy at work, performing their final checks of the onboard systems.
The final checkout sequence starts at approximately T-01:40:00 with the side hatch closing.
The unified Command Module hatch
The side hatch has a complicated locking mechanism that can be operated from the inside and the outside. It was one of the key components of the Apollo Command Module changed after the Apollo 1 pad fire. A nitrogen-powered counterbalance system helps the hatch be quickly opened in seconds, if needed.
T-001:30:46 S/C: Hello pad.
T-001:30:23 Lovell: CDR, Go.
T-001:30:08 Lovell: Roger. Will do.
Download MP3 audio file. 1,175 kB. PAO loop.
This is Apollo Saturn Launch Control; we're at T minus 1 hour, 29 minutes, 57 seconds and counting. Finishing up at this time is the checks of the Emergency Detection System. Skip Chauvin, the Test Supervisor, now also making some - he's Spacecraft Test Supervisor - making some checks with the various members of the team - launch crew inside the spacecraft. The Boost Protective Cover has now come closed. This is the cover which will protect the spacecraft hatch both from the jettison of the Launch Escape System and also as it develops some friction as it goes up through the heavy Earth's atmosphere. The (close-out) crew now, as they prepare the Boost Protective Cover, will also be going around the White Room doing what's called 'breaking up the White Room' or generally preparing it for retraction. Once the close-out crew departs the White Room area, that White Room will be retracted to a stand-by position. It will remain in that stand-by position down through the countdown to the T minus 5-minute mark, at which time it will come back to the fully retract position. Now T minus 1 hour, 28 minutes, 52 seconds and counting; this is Kennedy Launch Control.
Boost Protective Cover (BPC) diagram.
The Boost Protective Cover shields the Command Module during the initial phase of the launch, up until about 3 minutes into the flight, or when the Launch Escape System is jettisoned and the BPC along with it. The main purposes are to protect the Command Module windows as well as the primary thermal protective system composed of the forward heatshield and the Kapton plastic film that covers the entire skin of the Command Module and provides thermal control assistance while in open space. This saved weight on the actual spacecraft, by eliminating the need for a more heavy thermal protection system. The BPC is composed of a rigid top section made out of fibreglass and a cork-based ablative material, while the bottom part is composed of fibreglass cloth covered in the same cork ablative material. In this context, ablative means that as the material becomes charred, it transfers heat away instead of allowing the spacecraft underneath it suffer from the high temperatures.
Download MP3 audio file. Spacecraft communications.
T-001:27:49 S/C: Reset.
T-001:26:24 Lovell: You want me to regulate it down below 0.6?
T-001:26:18 Lovell: Okay, I'll give her a try.
T-001:25:59 Lovell: And we're looking at about point 4½ to 5
T-001:25:48 S/C: Okay.
T-001:24:56 Lovell: Ah, Roger. She's [garble]. We're good below 0.6.
They are likely checking the pressure difference between the oxygen circulating in their suits and in the cabin. The pressure is kept higher in the suit circuit to avoid the oxygen/nitrogen mixture in the cabin leaking into their suits.
T-001:22:56 Lovell: This is the CDR. I've checked all the breakers down below there. All three EDS and the two ELS circuit breakers are in.
These circuit breakers supply power to the EDS - Emergency Detection System, and the ELS, or Earth Landing System. Both need to be powered up for the ascent so that the first can detect excessive attitude changes during atmospheric flight, and in case of a catastrophic failure of the launch vehicle, so that the second system will ensure a safe splashdown of the Command Module in the Atlantic Ocean.
T-001:22:37 Swigert: Uptel IU, Block now.
The computer in the Instrument Unit can have some of its programming remotely updated via a radio link. This switch selection inhibits that for the moment.
Download MP3 audio file. 932 kB. PAO loop.
This is Apollo Saturn Launch Control; T minus 1 hour, 19 minutes, 58 seconds and counting. At this time, the close-out crew has reported from the White Room that they are in the last stages of clearing out the White Room and making it ready for its retract position. Also going on at this time are some computer checks with the launch vehicle. These computer checks will be run continuously throughout the final portion of the countdown to ensure that the ground computers are communicating properly with the computers aboard the space vehicle. The launch crew had been having some problems with a vent valve in the first stage of the liquid oxygen tank. As mentioned earlier, the liquid oxygen as it does boil off, is vented to the atmosphere. One of these vent valves appeared to be sticking; that problem now does appear to be solved as it has been brought closed. Now at T minus 1 hour, 19 minutes, 8 seconds and counting; this is Kennedy Launch Control.
The ascent of the Saturn V-Apollo stack is not controlled from the spacecraft but instead from within the booster. A 1-meter-tall segment sits on the top of the S-IVB third stage of the booster and contains its own independent guidance and control systems used for the first phase of the mission.

Saturn V Instrument Unit
The Instrument Unit, or IU, is built by IBM. At its core are the Launch Vehicle Digital Computer (LVDC) that will perform all the necessary control functions during ascent, and the ST-124 inertial platform capable of sensing changes in their attitude and acceleration.

Launch Vehicle Digital Computer (diagram)
The equipment installed into the Instrument Unit turns the Saturn V into what can be considered a third spacecraft in the Saturn-V-Apollo stack.
The Master Display Console.
Directly in front of the three-man crew is the Master Display Console. 419 switches, circuit breakers and dials are accompanied by dozens of gauges, talkbacks and other displays that provide the crew with information about the onboard systems and their status. Some of its switches they use constantly, others are turned into the On position before launch and never touched again. Knowing each of them and their required position is a must, however.
Download MP3 audio file. Spacecraft communications.
T-001:19:05 Lovell: CDR, Roger.
T-001:18:51 Lovell: Roger. I'm reading 8 0 on the Q-ball.
The Q-Ball, diagram view
The instrument known as the Q-ball is positioned on the very tip of the Launch Escape Tower sitting on top of the Command Module. Eight holes in the dome are used to gauge air pressure. During the ascent, they provide information about air resistance, as well as the angle of attack of the vehicle. In an abort situation, this will alarm the EDS to the booster going out of control.
T-001:18:26 Lovell: Roger. Caution and Warning going Normal
T-001:18:20 Lovell: That's affirm.
T-001:18:10 Lovell: FDAI GPI going to Off.
T-001:17:46 Lovell: That's affirmative. ECS Electronic Power is in GDC/ECA.
T-001:17:38 Lovell: Roger.
T-001:17:35 Lovell: 1 is On.
T-001:17:32 Lovell: 2 is On.
T-001:17:08 Lovell: FDAI GPI Power going to back to Both.
T-001:17:04 Lovell: In Both.
T-001:17:01 Lovell: Caution and Warning going to Acknowledge
T-001:16:39 Lovell: Roger.
T-001:16:34 Lovell: [Garble] is [garble].
T-001:16:28 Lovell: Roger. Verify 162.
T-001:16:24 Lovell: Pitch is 090.
T-001:16:22 Lovell: And zero on the Yaw.
These are attitude angles as read out from the Flight Director/Attitude Indicator (FDAI). 162° represents a heading of 72° east of north (90 + 72 = 162).
T-001:16:16 Lovell: Roger
T-001:16:03 Lovell: [Garble].
T-001:15:56 Lovell: Roger. Going 168.
T-001:15:49 Lovell: We're at 168.
T-001:15:41 Lovell: [Garble] one.
T-001:15:32 Lovell: 355 on the Yaw.
T-001:15:24 Lovell: Roll is Right.
T-001:15:22 Lovell: Pitch is Up.
T-001:15:19 Lovell: Yaw is full Right.
T-001:15:17 Lovell: Going ball 2.
T-001:15:11 Lovell: That's affirm. I verify that.
T-001:15:02 Lovell: Roger. Going GDC Align.
T-001:14:50 Lovell: Errors are nulled. [Garble].
T-001:14:43 Lovell: Roll going back to 162.
T-001:14:34 Lovell: 162.
T-001:14:28 Lovell: Pitch is 090.
T-001:14:19 Lovell: Zero on the Yaw.
T-001:14:14 Lovell: Roll is full left.
T-001:14:05 Lovell: Okay. I have Roll, 162; Pitch is 079.
T-001:13:57 Lovell: Okay, 090.
T-001:13:54 Lovell: That's Okay. I was kind of wondering where [garble], okay.
T-001:13:47 Lovell: Okay. Pitch is 090.
T-001:13:42 Lovell: And zero on the Yaw.
T-001:13:35 Lovell: Roll is full Left.
T-001:13:32 Lovell: Pitch is full Down.
T-001:13:30 Lovell: Yaw is full Left.
T-001:13:24 Lovell: Going ball 1.
T-001:13:19 Lovell: I verify that.
T-001:13:12 Lovell: Roger. GDC Align.
T-001:13:02 Lovell: Ball 1 has stabilized.
T-001:12:55 Lovell: Roll is 162.
T-001:12:51 Lovell: 090 on the Pitch.
T-001:12:49 Lovell: Zero on the Yaw.
T-001:12:17 Swigert: Okay. Standby.
T-001:12:10 Swigert: Okay, both Main Bus Ties are On.
T-001:12:05 Lovell: Roger. SCS TVC Pitch and Yaw are verified Rate Command.
T-001:11:52 Lovell: TVC Servo Power 1, AC1/Main A.
T-001:11:49 Lovell: 2 is AC2/Main B
T-001:11:42 Lovell: Verify GPI.
T-001:11:38 Lovell: Roger. Arming.
T-001:11:23 Lovell: Okay. Standby for Primary Gimbal Motors, On.
T-001:11:19 Lovell: Okay. Pitch 1.
T-001:11:15 Lovell: Yaw 1.
T-001:11:09 Lovell: Primes are On.
T-001:11:01 Lovell: I have Pitch and Yaw thumbwheel drive.
T-001:10:51 Lovell: Thumbwheels at zero.
T-001:10:48 Lovell: Checking MTVC.
T-001:10:41 Lovell: I have MTVC.
T-001:10:34 Lovell: SCS TVC Pitch and Yaw going to Auto.
T-001:10:29 Lovell: Roger.
T-001:10:21 Lovell: Secondaries are started.
T-001:10:17 Lovell: Clockwise and holding.
T-001:10:07 Lovell: I have thumbwheel drive.
T-001:10:04 Lovell: Thumbwheels are zero.
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This is Apollo Saturn Launch Control; T minus 1 hour, 9 minutes, 59 seconds and counting. At this time in the Command Module Odyssey, the three crewmen; spacecraft commander Jim Lovell, Command Module Pilot Jack Swigert, and Lunar Module Pilot Fred Haise; are very busy. The spacecraft commander and Command Module Pilot are configuring the Stabilization and Control System for lift-off and aligning that system with the guidance platform aboard the spacecraft. Also going on at this time is a check of the large propulsion system engine below the Service Module. This engine can be gimbaled in response to commands. This is done in two ways and these systems are being checked out at this time. There is a thumbwheel control which can set the engine to a preset position for certain maneuvers and also a Rotational Hand Controller which can be used for the actual flight of a maneuver. These checks are being made now, the engine being gimbaled with spacecraft commander Jim Lovell indicating the position that he is putting these to and readouts are being made to ensure that the engine is gimbaling a proper response. Also at this time a final checkout by the crew of the Entry Monitoring System, also a final setting of this system. Our countdown proceeding well at this time; T minus 1 hour, 8 minutes, 40 seconds; this is Kennedy Launch Control.
Although the SPS engine in the Service Module will normally only be used for the first time for a possible course correction after they've been propelled towards the Moon, in case of a high altitude launch abort it can also be used to push the Command Module away from the Saturn V booster and even continue on to achieve orbit.
T-001:09:57 Lovell: I have MTVC.
T-001:09:53 Lovell: Roger.
T-001:09:45 Lovell: Secondaries are Off.
T-001:09:35 Lovell: No response.
T-001:09:31 Lovell: THC is Neutral.
T-001:09:20 Lovell: Roger. 1.5.
T-001:09:14 Lovell: Roger. Pitch is set.
T-001:09:07 Lovell: Plus 1.32.
T-001:09:00 Lovell: And we're set.
T-001:08:52 Lovell: Okay.
T-001:08:52 Lovell: How's that on Pitch?
T-001:08:43 Lovell: How's that on Yaw?
T-001:08:39 Lovell: Okay.
T-001:08:36 Lovell: Primaries coming Off.
T-001:08:26 Lovell: Primaries are Off, Jim.
T-001:08:21 Lovell: And hand controllers locked.
T-001:08:52 Haise: Okay.
T-001:08:00 Haise: And they're both Auto.
T-001:07:53 Lovell: Roger. TVC Servo Powers 1 and 2 going Off.
T-001:07:45 Lovell: We're back to S-II/S-IVB.
T-001:07:40 Lovell: Roger. FDAI Select is one half.
T-001:07:35 Lovell: Source is CMC.
T-001:07:28 Lovell: Roll is 162.
T-001:07:25 Lovell: Pitch is 090.
T-001:07:22 Lovell: Zero on the Yaw.
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T-001:06:12 Lovell: Roger.
T-001:06:08 Lovell: Entry MS Roll coming On and Up.
T-001:06:02 Lovell: Pushing GDC Align.
T-001:05:52 Lovell: Roger. Standby.
T-001:05:05 Lovell: Okay. Completed, Skip.
T-001:05:01 Lovell: Yeah, it's good. I'm back on up. I went to 45 to the right, and then put it back.
T-001:04:54 Lovell: GDC Align has been released.
T-001:04:49 Lovell: Off. EMS roll back to Off.
T-001:04:41 Lovell: FDAI Select going to 1.
T-001:04:38 Lovell: [Garble].
T-001:04:36 Lovell: [Garble] IMU.
T-001:04:31 Lovell: Roger. Standby.
T-001:04:22 Lovell: They are nulled.
T-001:04:16 Lovell: SF [?] going to GDC.
T-001:04:10 Lovell: Rog. Standby.
T-001:04:06 Lovell: And GDC Alignment's complete.
T-001:04:00 Lovell: Source is CMC.
T-001:03:58 Lovell: [Garble] one half.
T-001:03:49 Lovell: EMS now going to Standby. It's in Standby.
T-001:03:40 Lovell: Ah, Roger. Going clockwise to Delta-V Set/VHF Range
T-001:03:31 Lovell: Roger. In work.
T-001:02:11 Lovell: This is CDR. I have 69999 set in the EMS and I'm back on Delta-V.
T-001:02:03 Lovell: That's affirm.
T-001:01:52 Haise: Caution and Warning Boost, now.
T-001:01:08 Haise: Okay. Except it's Jack's control head. You want mine on the PTT or you want to stick?
T-001:00:59 Haise: Okay. I'm holding.
T-001:00:25 Lovell: Sounds good.
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This is Apollo Saturn Launch Control. We're just passing the 1-hour mark in our countdown. Now in the final hour of the countdown toward the launch of Apollo 13. The close-out crew has now left the White Room area, and will be standing by for the retraction to the 12-degree position of swing arm number 9. We've received word from the distinguished guest site that the stands over there are near capacity with some 4,500 guests in the area. The Vice President of the United States, Spiro Agnew, and Chancellor Willie Brandt, his special guest, have arrived in the area although they are not at the stands yet. Out on the causeway, at a guest site, we have 7,000. This is the largest guest number that we have ever had on our causeway site. To recap our countdown, which has gone - proceeded very well today - we resumed the count after a 9-hour and 13-minute built-in hold at 4:13 am this morning. At that time the cryogenic loading began. This is loading aboard, the extremely cold liquid oxygen and liquid hydrogen. Liquid hydrogen is the fuel for the second and third stage. Liquid oxygen, the oxidizer used on all three stages. RP-1 or rocket propellant number 1 is the fuel used in the first stage. It is a kerosene-type fuel and was loaded before the countdown demonstration test back in mid-March. The cryogenic loading went well. There is over 800,000 gallons of cryogenics loaded aboard the Saturn V vehicle at this time. We entered a 1-hour built-in hold. This is a planned hold at the T-minus 3-hour and 30-minute mark. The crew was alerted this morning shortly before 9:00 am by Colonel Tom Stafford, Chief of the Astronaut Office. They then proceeded for a short but brief medical examination by Dr. John Teegen and Dr. Alan Harter. They were pronounced in good shape and ready for their flight. They then had the traditional breakfast of steak and eggs, tenderloin steak, eggs, orange juice, coffee, jelly and toast. After a brief mission briefing, they donned their space suits and took the 8-mile trip in a transfer van to the pad area. They have now been in the spacecraft going through a variety of tests and checks, going over all their switch lists and so on. Our weather at this time is better than had been predicted earlier. We're still looking for some clouds to move into the area and will be expecting a temperature of approximately 80 degrees at our launch time. We continue counting down toward a launch time of 2:13 pm EST. Now at T-minus 57 minutes, 15 seconds and counting; this is Kennedy Launch Control.
West German Chancellor Willy Brandt at the Launch Control Center's firing room, being presented a helmet by Kurt Debus, KSC director, and a German engineer who came to the USA with Wernher von Braun after WWII.
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T-000:58:52 Haise: Okay. Thought you'd forgot me for a minute. It's released.
T-000:58:28 Lovell: Roger.
T-000:57:49 Lovell: That's affirm, Skip. Nice and comfortable here this time.
Lovell, from 1970 Technical debrief: "In comparing this part of the flight preparation with Apollo 8, I can say that it was a lot more comfortable on Apollo 13. On Apollo 8, I was very cold during this period, and I suspect they've changed the Environmental Control System. It was very comfortable this time,"
T-000:56:54 Swigert: Okay.
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This is Apollo Saturn Launch Control; T minus 55 minutes and counting, T minus 55 minutes and counting and the countdown continues to go well here at the Kennedy Space Center. The close-out crew has now left the White Room. We're standing by for the retraction of the swing arm, swing arm number 9. That's actually scheduled to come at the 43-minute mark in the countdown. However, the close-out crew did leave somewhat early so that event could come a little bit earlier than scheduled. Now we'll go to the Manned Spacecraft Center in Houston, Texas for a status.
This is Mission Control, Houston. At the present time the flight controllers here in Mission Control are monitoring the countdown and the status of the crew, the launch vehicle, and the spacecraft. The world-wide manned space flight network is up and ready to support the launch. We do have a problem with the Vanguard tracking ship downrange in the mid-Atlantic. A tracking data processor, we understand, is down on the Vanguard and we will not get high speed radar tracking unless this problem is cleared up. The Vanguard is a desirable element of the tracking network, but is not essential, and we're Go to continue the launch with that problem. Just a few minutes ago, Ken Mattingly, who until a few days ago was the prime Command Module Pilot for Apollo 13, arrived in Mission Control, Ken will be assisting at the CapCom console and he's joined astronaut John Young and astronaut Joe Kerwin on the CapCom console. As he arrived in Mission Control, Flight Director Milton Windler greeted him and said, 'Sorry to see you here, Ken.' This is Mission Control, Houston at T minus 53 minutes and 20 seconds.
Ken Mattingly with CapCom Joe Kerwin in Mission Control during launch operations.
Mattingly was indeed in Houston at the time of the launch, not witnessing it from a beach near Cape as depicted in the popular Ron Howard movie.
Flight Director Milton Windler at his post in Mission Control. Flight Director Gerry Griffin behind him. NASA film caption.
Milton Windler is serving as the Lead Flight Director for the first time during Apollo 13. He will also superwise the launch along with his team of flight controllers in Mission Control.
The Flight Director holds immense power in the Apollo organization when he is on duty. The mission rules stipulate this very clearly. "The Flight Director may, after analysis of the flight, choose to take any necessary action required for the successful completion of the mission."
Flight Directors and their control teams work in shifts, each led by one of the Directors. Four teams were on duty for Apollo 13. They identified themselves with color terms. Milton Windler's Maroon Team was accompanied by Gene Kranz's White Team, Glynn Lunney's Black Team and Gerry Griffin's Gold Team.
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This is Apollo Saturn Launch Control; T minus 49 minutes, 58 seconds and counting. At this time we're making some preparations for range safety command system checks. These checks are the system aboard the launch vehicle which could be used by the range safety officers to destroy the vehicle should it stray off path - off its intended course. These destruct actions, of course, would not be taken until the astronaut crew had been advised and were safely away from the vehicle. We're also standing by to wait for swing arm 9 to retract. That should be happening within the next 5 or 10 minutes. The countdown continuing to move along nicely in the last hour. Now T minus 49 minutes, 20 seconds and counting; this is Kennedy Launch Control.
Range safety refers to the self-destruct system carried on every element of the Saturn V booster. If a catastrophic failure were to occur and the mission had to be aborted during the launch, then once the Command Module is separated by the automatic Emergency Detection System, a protected radio transmitter will be used to send the secret auto-destruct code into the launch vehicle. This will detonate shaped charges in the propellant tanks to rupture them and disperse their contents and hence prevent a potentially massive explosion upon impact.
Diagram of the S-II stage of the Saturn V with the shaped charge and the range safety electronics highlighted.
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T-000:47:01 Lovell: We're getting down there, Skip.
T-000:45:14 Swigert: And the Uptel Command is set to Normal.
T-000:45:07 Lovell: EDS Power coming On and Up.
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This is Apollo Saturn Launch Control; T minus 45 minutes and counting, T minus 45 minutes and counting. Steps are now underway for moving the swing arm back to the 12-degree or park position. Launch site recovery forces have called in at this point and have indicated they're on station and ready to support the launch of Apollo 13. The prime crew, inside the spacecraft at this time, left the Manned Spacecraft Operations Building at Kennedy Space Center at 11:07 am Eastern Standard Time this morning on their way out to the pad. They took the 8-mile trip in the transfer van, went up to the White Room level where spacecraft commander Jim Lovell was the first one to board the spacecraft at 11:32 am. He was followed by the Lunar Module Pilot who moved in; Fred Haise moved into the right-hand seat at 11:32. The Command Module Pilot, stood by in the elevator with a suit technician, was the last one to come aboard. He came aboard at 11:44 am Eastern Standard Time. We are now standing by for retraction of the White Room. That should occur in approximately 47 seconds. When it comes back, it will come back to a 12-degree or standby position. From this position, it can be quickly brought back to the Command Module if there is a need for the crew to egress or if we need to get a team in to the crew. At the T minus 5-minute mark in the countdown, the swing arm number 9 will come back to the fully retract position and it will then stay in the fully retract position throughout the launch. Once the White Room has been moved back to the 12-degree position, the Launch Escape Tower above the Command Module will be armed. Now standing by for the movement of the swing arm 9, some 5 seconds from this time. T minus 43 minutes and counting, and swing arm 9 should be coming back. Swing arm 9 moving back now to the 12-degree position, it's about some 10 feet now from the spacecraft. We now have word that the Vice-President Spiro Agnew, and the Chancellor of West Germany, Willy Brandt, have arrived at the distinguished guest site. Now at T minus 42 minutes, 31 seconds and counting; this is Kennedy Launch Control.
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T-000:43:00 Swigert: CMP can verify.
T-000:42:53 Swigert: Okay.
T-000:42:49 Swigert: Okay, the gearbox says set to LATCH.
The gear box is on the spacecraft main hatch, which will be latched shut.
T-000:42:33 Lovell: Roger. Command Module RCS Logic is On and Up.
T-000:41:25 Lovell: Logic A and B are Closed.
T-000:41:21 Lovell: Logic 1 and 2, going On and Up.
T-000:41:05 Lovell: Roger. Pyro Arms, A and B, going On and Up.
Pyro Arm switches, with the lockable guard shown.
The Pyro Arm switches are such critical controls in terms of safety that they have a locked guard over them up until just before the prime crew enters the cockpit. Turning them to the On position arms the abort system, which they do not want to activate accidentally. The cover is removed with the help of a physical key put into the lock.
T-000:40:42 Swigert: H2 fan 1, Off.
T-000:40:40 Swigert: H2 fan 2, Off.
T-000:40:37 Swigert: O2 1, Off. O2 2, Off.
T-000:40:14 Swigert: Okay. Verify the RCS Helium 1; A, On, Up; B, On, Up; C, On, Up; D, On, Up. Four gray.
T-000:40:01 Swigert: Helium 2; A, On, Up; B, On, Up; C, On, Up; D, On, Up. Four gray bar.
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This is Apollo Saturn Launch Control; T minus 39 minutes, 57 seconds and counting. At this time the command destruct system tests are now underway with the launch vehicle team. The Launch Escape System above the Command Module has now been armed and that escape system now would be capable of lifting the Command Module free of the launch vehicle should a problem arise. A correction to the last announcement - the Lunar Module Pilot Fred Haise entered the spacecraft at 11:38 am Eastern Standard Time this morning. Our countdown proceeding at this time; T minus 39 minutes, 24 seconds and counting; this is Kennedy Launch Control.
Launch Escape System, aka the launch escape tower.
Riding on the very top of the stack is the LES - Launch Escape System. It is a solid-fuelled rocket motor which, when activated by an abort command, will fire and pull the Command Module away from a possibly violently exploding Saturn V. Now activated, it can even be used while the stack is still on the launch pad, should there be an emergency where the crew has no time to evacuate the spacecraft.
The LES was tested several times under simulated abort conditions - and one real abort when an abort test suffered a booster failure and the EDS had to cope with a real emergency - thereby proving the concept.
T-000:39:47 Swigert: Secondary Fuel; A, Close; B, Close; C, Close; D, Close.
T-000:39:10 Lovell: Roger.
T-000:38:34 Swigert: Okay.
T-000:38:29 Swigert: Okay. Will do.
T-000:37:52 Lovell: 3950. Okay.
T-000:37:37 Lovell: And she's set.
T-000:35:10 Lovell: Apollo 13, Roger. [?]
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This is Apollo Saturn Launch Control at T-minus 34 minutes, 58 seconds and counting. At this time, the range safety command checks have just been completed. Preparations are now under way for the power transfer test. This is a critical test to ensure that the power can be transferred from the external source, which we have been using to conserve on batteries, to ensure that the power can be successfully transferred to the batteries aboard the space vehicle and that the systems are Go on those space vehicle batteries. Now at T-minus 34 minutes, 30 seconds and counting; this is Kennedy Launch Control.
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This is Apollo Saturn Launch Control, as we move into the final half hour of our countdown; T minus 29 minutes, 56 seconds and counting. The Brevard Sheriff's Department, Brevard County, Florida has reported that along route 1, the closest major highway to Kennedy Space Center, there are some 100,000 people and 25,000 cars parked watching for the launch of Apollo 13. Along the Indian and Banana Rivers it's reported that the - both rivers are literally filled with boats and spectators standing by to watch the launch. A private airport in Brevard County also reports some 500 private planes have landed and are parked at the airport. Our countdown continuing now - the power transfer test underway - T minus 29 minutes, 13 seconds and counting; this is Kennedy Launch Control.
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T-000:29:19 Lovell: Okay, understand this one. The LOX vent valve is being a bit of a problem, we’re just going to hold off arming the..uh..SM RCS.
T-000:28:54 Lovell: 29 minutes.
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T-000:25:05 Lovell: That sounds good.
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This is Apollo Saturn Launch Control; we're at T minus 25 minutes and counting, T minus 25 minutes and counting. And that critical launch vehicle power transfer test has been successfully completed. The Lunar Module will remain on internal power for approximately 10 minutes while the instrumentation aboard the Lunar Module is thoroughly checked out. It will then be deactivated and won't be reactivated again until the men enter the Lunar Module on their trip to the Moon. As the Apollo/Saturn V sits on the pad at this time, it's 214,369 nautical miles [397,011 km] from their destination - from their destination, the Moon. Now T minus 24 minutes, 20 seconds and counting; this is Kennedy Launch Control.
T-000:24:44 Swigert: Okay. A, On, Up now; B, On, Up now; C, On, Up now; D, On, Up now. I got four Primary Propellant gray bars and four Secondary Propellant gray bars.
This is where they start going down the Boost-Insertion checklist, found in their Launch Checklist. It will provide the crew with operational instructions up until the end of the Translunar Injection phase.
T-000:24:28 Swigert: Yep.
T-000:24:25 Swigert: I got eight altogether.
T-000:24:20 Swigert: Okay. Left to right; 80…
T-000:24:14 Swigert: Okay. Package Temp, 80. Helium pressure, 4150. Secondary fuel pressure, 200. Propellant quantity, pegged high.
T-000:23:53 Swigert: Yeah, standby. Helium Temp is 300.
T-000:23:48 Swigert: Negative, 75. 75.
T-000:23:40 Swigert: Okay. Package Temp, 80. Helium pressure, 4 - 4100. Secondary fuel pressure, 195. Propellant quantity, pegged high. Helium Temp, 73.
T-000:23:15 Swigert: Charlie Package Temp is 85. Helium pressure, 4100. Secondary fuel pressure, 200. Quantity, pegged high, and the tank temperature is 77.
T-000:22:49 Swigert: On Charlie, Secondary fuel was 200 – two zero zero.
T-000:22:42 Swigert: Okay. On Dog, Package Temp, 80. Helium pressure, 4150. Secondary fuel pressure, 190 and – and quantity pegged high, and the tank temperature is 75.
T-000:22:17 Swigert: Affirm.
T-000:21:33 Lovell: Okay. Standing by.
T-000:21:23 Lovell: Verify all four AC rolls are off.
T-000:21:18 Lovell: That's affirm. I did.
T-000:21:15 Lovell: B-1 is Main A.
T-000:21:07 Lovell: C-1, Main B.
T-000:21:04 Lovell: 2, Main A.
T-000:21:01 Lovell: C-2, Main B.
T-000:20:56 Lovell: A-3, Main B.
T-000:20:53 Lovell: C-3, Main A.
T-000:20:50 Lovell: C-3, Main A.
T-000:20:47 Lovell: A-4, Main A.
T-000:20:43 Lovell: C-4, Main B.
T-000:20:39 Lovell: B-3, Main A.
T-000:20:36 Lovell: C-3, Main B.
T-000:20:32 Lovell: C-4, Main B.
T-000:20:29 Lovell: D-4 is Main A.
Jim lists the RCS jets on the four quads around the Service Module, used for fine maneuvers while in space. Switches allow them to select the electric power source for each of them. Half of them are on Main Bus A, the other half on Main Bus B.
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This is Apollo Saturn Launch Control; T minus 19 minutes, 59 seconds and counting. Now at - passing the 20-minute mark in our countdown and the Spacecraft Test Supervisor has indicated that they are running just slightly ahead of that in their countdown. The Command Module Pilot Jack Swigert is now pressurizing the Service Module Reaction Control System. This is the system on the Service Module which consists of 4 quadrants with 4 engines each. Each one of these develops 100 pounds of thrust. He is arming these systems by letting the hypergolic fuels - these are monomethyl hydrazine and nitrogen tetroxide - flow down through the system, down to the final valves. Hypergolic fuels ignite on contact, so once those final valves are open they would ignite and the system would be activated. Swigert also reading out the temperatures and pressures of that system. The countdown moving along well at this time; T minus 19 minutes, 4 seconds and counting; this is Kennedy Launch Control.
Hypergolic fuels are an elegant solution to many issues rocket engines face, especially those designed to operate for long periods and repeatedly, such as the RCS jets. They ignite on contact with each other, which eliminates the need for a separate ignition system. A thruster merely requires the propellants to be injected into its combustion chamber and it will work. The fuels are also relatively stable in their liquid form, and do not need to be carefully conditioned, such as the very volatile cryogenic propellants used in the Saturn V. In space, the extremely toxic nature of the monomethyl hydrazine and nitrogen tetroxide is also not an issue.
Download MP3 audio file. Spacecraft communications.
T-000:16:56 Swigert: And do not Enter.
T-000:16:51 Swigert: Yeah.
T-000:16:45 Swigert: That would ruin all of our day, wouldn't it?
T-000:16:34 Swigert: About every time I do launches in the simulator.
T-000:15:51 Lovell: Skip, how's the weather?
T-000:15:44 Swigert: That's right, you don't have any windows, do you?
T-000:15:31 Swigert: I got one little hole up there, and it looks good here.
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This is Apollo Saturn Launch Control passing the 15-minute mark; T-minus 14 minutes, 57 seconds and counting. Chilldown of the second stage or S-II stage start tanks is in progress. This is necessary to prepare those start tanks for the flow of the liquid hydrogen and liquid oxygen. The S-II or second stage will ignite at some 2 minutes, 46 seconds into the mission if all goes as planned. The crew has been relatively quiet answering the Spacecraft Test Conductor Skip Chauvin in terse business-like manner as he questions them on certain switches and checks. In the distinguished guest site, the Vice President Spiro Agnew, the Chancellor of West Germany Willie Brandt and a Secretary of State Rogers, all with a large crowd over there awaiting the launch of Apollo 13. Our countdown continuing to go well at this time. The spacecraft is now going to full internal power. Up to this point it's been sharing its power load with the fuel cells aboard the spacecraft with an external power source. Also being carried out at this time is a astrocomm launch circuit check. This is the circuit that is used by the astronauts, the Spacecraft Test Conductor and Launch Operations Manager and the CapCom Stoney or Paul Weitz here during the launch phase of the mission. Now T-minus 13 minutes, 33 seconds and counting; this is Kennedy Launch Control.
View into the Launch Control Center and its dozens of controllers monitoring the Saturn V. NASA 16mm film. NARA.
A diagram showing the arrangement and the sheer scope of the firing room can be viewed from this link.
Download MP3 audio file. Spacecraft communications.
T-000:14:11 Haise: Bat[tery] Charlie is reading 36 volts.
T-000:14:00 Haise: Rog. I'm back to Main A.
T-000:13:33 Lovell: Roll is 162.
T-000:13:30 Lovell: Pitch is 090.
T-000:13:28 Lovell: Zero on the Yaw.
Jim reads the total attitude of the spacecraft, determined on the three axes of motion. Their roll is calculated at 90 degrees plus their launch azimuth - 72 degrees - resulting in the 162 degrees he reads at the moment. The pitch is 90 degrees, as appropriate - that indicates that they are 'standing' with their nose pointing directly above. Their yaw is zero.
T-000:13:24 Lovell: BMAGs; Roll, Pitch and Yaw are Rate 1.
T-000:13:19 Lovell: [Garble] is 55.
T-000:13:13 Lovell: Rate switch is High.
T-000:13:04 Lovell: CDR verified.
T-000:13:01 Swigert: CMP verifies.
T-000:12:54 Lovell: Roger. Direct Main A/Main B.
T-000:12:49 Lovell: CMC Mode is Free.
T-000:12:45 Lovell: Trans Controller Power is On and Up.
T-000:12:30 Lovell: This is CDR reading you loud and clear.
T-000:12:26 Lovell: This is CDR reading you loud and clear.
T-000:12:22 Lovell: This is CDR reading you loud and clear, STC.
T-000:12:12 Lovell: Stony, I'm reading you loud and clear. This is the CDR.
T-000:12:06 Lovell: [Garble], this is CDR reading you loud and clear.
T-000:12:02 Lovell: Yeah, I'm reading you loud and clear, Skip.
T-000:11:36 Lovell: VHF going off.
T-000:11:26 Lovell: Houston, this is CDR. I'm reading you loud and clear.
T-000:11:14 Haise: Ah, read you loud and clear, Joe.
They perform a series of radio checks, first with Launch Control Operations in Kennedy Space Center, then with the Mission Control Center located in Houston, Texas. Fred addresses Houston as 'Joe', referring to the CapCom, astronaut Joe Kerwin, who is manning that post in the Mission Control Operations Room.
T-000:10:47 Lovell: VHF A, I'm going to T/R.
T-000:10:44 Network: Launch Area stations, this is Network on Net 1 for final status check. MILA?
Network is the Mission Control station responsible for ensuring the working of the MSFN - Manned Spaceflight Network. They are now checking in with the stations covering the Atlantic Ocean, which is the launch path of the Saturn V.
T-000:10:41 Lovell: [Garble] Thrust switch...
T-000:10:39 MILA: Go.
MILA, or Merritt Island Launch Annex, is the local radio and tracking station at the space center at Cape.
T-000:10:38 Network: Bermuda?
T-000:10:37 Bermuda: Bermuda's Go.
The next tracking station going east is on the island of Bermuda.
T-000:10:36 Network: Vanguard?
T-000:10:35 Lovell: ...Off and guarded.
T-000:10:34 Vanguard: Go.
The tracking ship Vanguard is parked in the Atlantic, to provide radio coverage in an area with no land stations. Despite some earlier technical issues, they are ready to support the mission.
Tracking ship Vanguard.
T-000:10:33 Network: Canary?
T-000:10:32 Canary: Canary is Go.
Moving towards the continent, the next tracking station is at the Canaries Islands off the coast of West Africa.
T-000:10:31 Network: Roger.
Ground tracks of the launch trajectory, with communications and tracking site coverage.
T-000:10:31 Lovell: ...it's in Alpha.
T-000:10:23 Swigert: EDS Auto, verified, On, Up.
Jack has set the Emergency Detection System to Auto mode, which will enable an automatic abort under particular conditions. These would be a launch vehicle structural failure, a dangerous drop in the first stage thrust (usually indicating at least two engines failing) or rates in excess of 4 degrees/second in pitch or yaw and 20 degrees/second in roll. The two conditions besides the structural failure can be manually disabled with switches on the control console.
T-000:10:18 Swigert: Launch vehicle rates, verified Auto.
This allows the EDS to perform an automatic abort of the mission should the launch vehicle tumble out of control, based on the pre-programmed figures.
T-000:10:15 Swigert: Two engines out, verified Auto.
This switch selection allows the EDS to perform an automatic abort should two engines go out during the firing of the S-IC first stage.
T-000:10:04 Swigert: RCS Command, Off, released.
Download MP3 audio file. 661 kB. PAO loop.
This is Apollo Saturn Launch Control; T minus 9 minutes, 58 seconds and counting. The third stage start tanks are now beginning their chill down. Third stage scheduled to ignite at 9 minutes, 22 seconds into the mission. Also going on at this time is one of the computer checks which are carried out throughout the final portion of the launch. This particular one is a checkout of the Launch Vehicle Digital Computer to ensure that it is ready for launch. A final check of the weather indicates that earlier worries about the weather have come to naught. Weather looks good and is satisfactory; presents no constraint to our launch. Now at T minus 9 minutes, 25 seconds and counting; this is Kennedy Launch Control.
The PAO announcer mentions multiple start tanks in the third stage (the S-IVB). In fact, there is only one. Each J-2 engine has a start tank filled with hydrogen. At engine start, this hydrogen is released through the turbopumps to get them spinning. Since the third stage has only a single J-2, it has one start tank.
T-000:09:58 Lovell: TVC Servo Power 1, AC1, Main A.
T-000:09:54 Lovell: 2, AC2, Main B.
T-000:09:47 Haise: A Reacs Valve to Latch.
A remarkable operation takes place here. Fred has applied power to the fuel cell reactant valves to make sure that the magnetic solenoid valves are not accidentally shut off by the G forces during the launch.
T-000:09:34 Haise: Okay. Secondary Coolant Loop Pump is Off.
Download MP3 audio file. Spacecraft communications.
T-000:08:05 S/C: Go.
T-000:08:04 S/C: Go.
T-000:08:02 S/C: Go.
T-000:07:01 Lovell: 13, Roger.
T-000:06:33 Lovell: Understand.
T-000:06:02 Lovell: Six minutes, Roger.
Download MP3 audio file. 5,555 kB. PAO loop.
This is Apollo Saturn Launch Control; T minus 5 minutes, 27 seconds and counting. Now as we move in to the final phase of the countdown, we're receiving Go/No Go checks from various elements of the launch team. The Spacecraft Test Conductor Skip Chauvin gave the test supervisor a spacecraft ready. At that time, on our large status board here in the firing room, the green light came on behind the spacecraft. The green light now is also on behind the Emergency Detection System. Now standing by for more checks. The Mission Director Chet Lee from the Manned Spacecraft Center in Houston says we are Go for launch and the range indicates that the range is ready to support. Chilldown of the S-IVB stage - chilldown of the S-IVB stage being completed at this time. S-IVB will ignite into the mission at 9 minutes, 22 seconds. Swing arm number 9 now is retracting to the full retract position. Swing arm number 9 coming back to the full retract position. And the Director of Launch Operations Walt Kapryan has given Apollo 13 a Go for launch. We're now approaching the four-minute mark. At the T minus 4-minute mark, we'll be standing by for Jack Baltar, the Launch Vehicle Test Conductor, to say that his launch vehicle team is ready to carry out the final phase here of the countdown. At the T minus 3-minute, 7-second mark, we will get the ignition sequence start. This will put us on an automatic sequencer and the remainder of the count from that time will be on automatic. The sequencer can check out literally hundreds of items in the space vehicle. At the same time, the team here in the Launch Control Center will be monitoring redline values. These are such things as temperatures and pressures which we do not want to either go above or below. A final communications check now. The astronauts on the astrocomm circuit and Launch Operations Manager Paul Donnelly, during his final check said, 'Good luck, head for the hills.' He was referring to the Fra Mauro - hilly Fra Mauro region of the Moon. As we come up on the T minus 3-minute mark at 3 minutes, the capsule communicator Paul Weitz will begin reading out the minus times to the crew. Looking up at our status board now, we can see that the spacecraft - or the first stage preparations are now complete. The firing command has now been initiated. This is the automatic sequencer and we have a confirmation on our status board that the launch sequence has started.
T-000:04:58 Lovell: 13, Roger.
T-000:04:10 Lovell: Launch vehicle lights are on, STC.
Five lights go on in the Main Display Console, to indicate the five engines of the S-IC first stage of the Saturn V.
T-000:03:57 Lovell: This is 13, reading you loud and clear.
T-000:03:50 Lovell: Thank you very much. We'll do our best.
T-000:03:46 Lovell: I'm reading you loud and clear, Skip.
T-000:03:42 Swigert: That's verified.
The Command Module Computer DSKY (Display and Keyboard). Scan via heroicrelics.org
Jack is most likely talking about the onboard computer display, where the program indicator should be showing 02 - Program 2. This is a pre-launch program meant to orientate the onboard gyroscopic platform.
The computer Display and Keyboard (DSKY) holds a central location, positioned so that both the Commander and the Command Module Pilot can operate and observe it. The computer itself physically sits beyond their feet, secured in the lower compartment wall. The computer determines their position and their attitude, calculates trajectories and firings of their main engine or the maneuvering thrusters. The crew communicates with the computer through a numeric keyboard used to input commands in the form of Verbs and Nouns. These linguistic terms are not merely symbolic, but reflect the format of the user interface. The computer displays its information in the form of three five-digit lines, also known as registers.
T-000:03:31 Swigert: Verb 75. Do not Enter.
Jack is noting that the computer is displaying Verb 75. Verb 75 is a backup command to be used if the computer does not automatically receive the so-called lift-off discrete, a signal that means they have begun to rise from the pad and for the computer to proceed to Program 11, which it is to run during the ascent. Should they reach the end of the countdown and the computer fails to go to Program 11 automatically, only then will they press ENTER on their computer keyboard to start it up. Program 11's function is to shadow the guidance of the Saturn V. It does not control the vehicle, which is controlled from within the Saturn V's Instrument Unit.
T-000:03:24 Swigert: That's real fine work you did, Skip.
We're now in our final 3 minutes of the countdown. Two minutes, 56 seconds and Apollo 13 continues to be Go. The astronauts still reporting back from the spacecraft Odyssey. Spacecraft commander Jim Lovell says Odyssey is Go. He will be the last one to perform a function here during the countdown. At the T minus 45-second mark, the commander Jim Lovell will set the final alignment of the spacecraft guidance and that's the last crew action before the lift-off of Apollo 13. We continue to aim for a lift-off at 2:13 pm Eastern Standard Time.
T-000:02:52 Haise: Okay. Tape Recorder's Forward, and I got a gray flag.
A high tech tape recorder, utilizing a magnetic tape, will record onboard instrumentation data to be played back to Mission Control later on. It will also record the onboard conversations of the crew on a separate track, which is also similarly accessible.
Now T minus 2 minutes, 18 seconds and counting. And our count continues to look good. Our weather is no constraint to launch today. Earlier fears about the weather seem to have dissipated. A stationary front over the Florida-Georgia border has not sent down the predicted bad weather that we had feared. We just passed the two-minute mark - just passed the two-minute mark in the countdown and the pressurization now of the vehicle tanks is beginning.
High-presure helium is pumped into the tanks from the ground support equipment to begin initial pressurization of the fuel and oxidizer tanks. Once the external connections are sealed off, internal helium tanks will maintain the tank pressurization until engine start. After that, the engines generate gas pressure that is fed via piping into all tanks except the RP-1 tank to pressurize them. The RP-1 tank is pressurised from the onboard helium supply throughout the S-IC's flight.
The third stage liquid oxygen tank has now been pressurized and the second stage liquid oxygen tank has been pressurized. We'll be making our final transfer from external power source, that is from the external power source at the pad, to the launch vehicle batteries at the T minus 50-second mark. We'll be keeping an eye on that power transfer at T minus 50 seconds. The S-IVB propellants now all pressurized. S-IVB propellants, that's the third stage of the Saturn V, pressurized. One minute, 15 seconds and counting. The spacecraft equipment now is on its own internal cooling. It's been sharing its cooling from - getting its cooling from an external power source up to this time.
Cold gaseous nitrogen is blown into machinery spaces inside each of the three stages of the Saturn V, to condition them.
T-000:02:07 Lovell: Roger. Primary Glycol Coolant Valve, pull to Bypass.
Normally, a glycol-water mix is circulated in the cooling system and to radiator panels on the surface of the Service Module. For the launch, however, they take the radiators out of the circuit by pulling a manual lever. The friction between the skin of the spacecraft and the air around them will heat the skin as they ascend, which makes the radiators incapable of cooling.
The handle for bypassing the spacecraft's radiators is on the left of this image taken within Odyssey's cabin.
T-000:01:06 Haise: [Garble] are On.
Onboard the Command Module, Fred Haise has set the two Main Bus Tie switches to On position. This connects the three Command Module batteries into the Main Buses that are responsible for supplying all electric power to the spacecraft. While the spacecraft draws its power from the onboard fuel cells, the ascent is a high demand situation and the energy stored in the batteries can be used to balance the loads put on the power generation system.
The batteries will also act as a backup should any problems arise with the Electric Power System during the extremely crucial launch phase. This could be a failure of part of the power distribution system, or one of the fuel cells, for example. This redundancy offered by the batteries was demonstrated dramatically during the launch of Apollo 12 where a lightning strike disabled all the fuel cells, the guidance system and the onboard instrumentation. The batteries being on the line allowed them to troubleshoot their issues and continue onto an entirely successful lunar landing mission.
We're now approaching the T minus 1-minute mark. T minus 1 minute; T minus 1 minute and counting. Now in the final minute of our countdown. At the 36-second mark, swing arm number 1 will retract.
Swing arm 1 - or service arm 1 - has been used to top off the S-IC stage with liquid oxygen up until this point.
T-000:00:51 Lovell: [Garble] come Off. And it comes Off.
T minus 50 seconds as we pass the T minus 50-second mark, power transfer takes place. First stage, second stage, third stage and the Instrument Unit going to internal power. T minus 37 seconds and our count continues to go well. We'll be looking for an ignition of those five first stage engines at the T minus 8.9-second mark.
Up until this point, the launch vehicle has received external power through the support arms. This is to save battery powered inside the Saturn V to minimize the size of the batteries needed to carry on the rocket, of course.
T-000:00:43 Lovell: GDC Align.
T-000:00:34 Lovell: Align's complete.
The last prescribed action for the crew before the launch is for the Commander to press the GDC Align button on his console. It gives the backup guidance system the numbers that define the spacecraft's attitude as measured by the primary guidance system to ensure that both of them have an identical idea of the vehicle's attitude at launch.
Diagram of the Rocketdyne F-1 engine. 5 of them made up the S-IC first stage.
A certain amount of knowledge about the anatomy of the engine will help to understand its function. A large combustion chamber and bell have an injector plate at the top - not unlike a giant showerhead - through which RP-1 kerosene fuel and liquid oxygen (LOX) are injected at high pressure. Above the injector is the LOX dome which also transmits the force of the thrust from the engine to the rocket's structure. A single-shaft turbopump is mounted beside the combustion chamber. The turbine at the core of the turbopump is at the bottom and is driven by the exhaust gas from burning RP-1 and LOX in a fuel-rich mixture in a gas generator. This way, once started, the engine produces its own operating power. After passing through the turbine, the exhaust gas continues into a heat exchanger, then to a wrap-around exhaust manifold which feeds it into the periphery of the engine bell. The final task for these hot gases is to cool and protect the nozzle extension from the far hotter exhaust of the main engine itself. The nozzle is the visible cone-shaped part of the engine and what people looking at it will probably perceive as the 'real' engine, although the combustion happens above it. The purpose of the nozzle is to direct the extremely hot, energetic gas molecules in the opposite direction to the spacecraft's desired direction - hence generating the actual propulsion. Also above the gas-driven turbine on the same drive shaft is the fuel pump with two inlets from the fuel tank and two outlets going, via shut-off valves, to the injector plate. A line from one of these 'feeds' supplies the gas generator with fuel. Fuel is also used within the engine as a lubricant and as a hydraulic working fluid - This keeps the weight down. Before launch, RJ-1 ramjet fuel is supplied from the ground for this purpose. And then at the top of the turbopump shaft is the LOX pump with a single, large inlet in-line with the turboshaft axis. This pump also has two outlet lines, with valves, to feed the injector plate. One line also supplies LOX to the gas generator. The interior lining of the combustion chamber and engine bell consists of a myriad of pipework through which a large portion of the fuel supply is fed before it goes into the actual combustion chamber to be burnt. This cools the chamber and bell structure while also pre-warming the fuel.
The last important component to note is an igniter, containing a cartridge of hypergolic fluid with burst diaphragms at either end, and located in the high pressure fuel circuit. It has its own inject point in the combustion chamber. Upon ignition command a mixture of triethylboron with 10-15 per cent triethylaluminium is released into the combustion chamber.
The function of a hypergolic igniter is rather simple. A great deal of heat is needed to light the RP-1 and LOX propellant that is being pumped into the engine. The mixture of triethylboron and triethylaluminium is hypergolic with oxygen, meaning that once they come in contact with the LOX inside the combustion chamber, they will combust violently. This will provide the starting 'fire' to start the engine properly.
Every liquid fuel rocket engine on the Saturn V-Apollo stack, except for the F-1 and J-2 engines, employed hypergolic propellants. This was done for the ease of storage and the ensuing reliability of function.
Of the 110.6-metre height of the entire Apollo 15/Saturn V stack, 42.1 metres comprise the S-IC first stage. Five F-1 engines are clustered at the bottom of the stage to provide 34,025 kN (7,700,000 pounds) of thrust in total. The propellants used are RP-1 (Rocket Propellant-1 or highly refined kerosene) as the fuel and LOX as the oxidiser.
Diagram of the Saturn V's S-IC first stage.
We have passed T minus 30. T minus 25 seconds and counting and Apollo 13 is Go.
T minus 20 seconds. T minus 20 seconds and counting.
17 - Guidance Release -
Guidance Release means that the mechanically suspended inertial guidance unit in the Saturn V's IU Instrument Unit is no longer being held with respect to the rotation of Earth and is now free to begin to sense the spacecraft motion and acceleration.
Service arm 2 is retracted. It provides power and environmental control to the S-IC stage.
15, 14, 13, 12, 11, 10, 9, 8, ignition sequence has started.
While the PAO's countdown is heard on the public radio transmission, the crew receives their own countdown from astronaut Paul J. Weitz in Launch Control Center, where he has been monitoring the launch procedures as the 'Stoney' CapCom.
The ignition sequence of an F-1 engine is a complicated affair with many interrelated events happening almost simultaneously. At T minus 8.9 seconds, a signal from the automatic sequencer fires four pyrotechnic devices. Two initiate combustion within the gas generator while another two cause the fuel-rich turbine exhaust gas to ignite when it enters the engine bell. Electric wire links are deliberately burned away by these igniters to generate an electrical signal to move the start solenoid. The start solenoid directs hydraulic pressure still provided from the ground supply to open the main LOX valves. LOX begins to flow through the LOX pump, starting it to rotate, then into the combustion chamber. The opening of both LOX valves also causes a valve to allow fuel and LOX into the gas generator, where they ignite and accelerate the turbine connected to the gas generator's output. Fuel and LOX pressures rise as the turbine gains speed. The fuel-rich exhaust from the gas generator ignites in the engine bell to prevent backfiring and burping of the engine. The increasing pressure in the fuel lines opens another valve, the igniter fuel valve, letting fuel pressure reach the hypergol cartridge which promptly ruptures. Hypergolic fluid, followed by fuel, enters the chamber through its own ports where it spontaneously ignites on contact with the LOX already in the chamber.
6..."
Rising combustion-induced pressure on the injector plate actuates the ignition monitor valve, directing hydraulic fluid to open the main fuel valves. These are the valves in the fuel lines between the turbopump and the injector plate. The fuel flushes out ethylene glycol which had been preloaded into the cooling pipework around the combustion chamber and nozzle. The heavy load of ethylene glycol mixed with the first injection of fuel slows the build-up of thrust, giving a gentler start. Fluid pressure through calibrated orifices completes the opening of the fuel valves and fuel enters the combustion chamber where it burns in the already flaming gases ignited by the hypergol cartridge. The exact time that the main fuel valves open is sequenced across the five engines to spread the rise in applied force that the structure of the rocket must withstand.
5, 4, 3, 2, 1, zero.".
As fuel and LOX flow increase to maximum, the rise in chamber pressure, and therefore thrust, is monitored to confirm that the required force has been achieved. With the turbopump spinning at full speed, fuel pressure exceeds hydraulic pressure supplied from ground equipment. Check valves switch the engine's hydraulic supply to be fed from the rocket's fuel instead of from the ground.
0.3 seconds after range time start, the so-called first motion is detected when the Saturn V unseats from the launch pad. This starts the clock, and the mission officially begins.
Tail Service and Hold Down Arms
Tail Service Arm
Three tail service arms supply connections to the S-IC stage. They are retracted at lift-off.
Holddown Arm mechanism
Four holddown arms are located on the Mobile Launcher and hold the Saturn V stack in place during assembly, before launch and during lift-off. Each holddown arm can withstand 700,000 pounds of force. During launch, they keep the vehicle steady while the five first stage engines come up to full thrust. The holddown arms are also used to literally hold the launch vehicle back in the sense of not allowing it to simply lurch off the launch pad. A tapered pin system, with a bracket in the holddown arm and a die on the Saturn V, slows the lift-off process for the first six inches of travel, sufficient to maintain the dynamic loads generated by the massive engines within the structural limits of the Saturn V vehicle.
Five service arms remain connected to the booster up until the point of lift-off. The first motion of the spacecraft triggers the system to separate the service arms, which will then swing back and out of the way.
000:00:01 Weitz (LCC): Lift-off.
The lift off is announced by astronaut Paul Weitz from Launch Control.
Flight Plan page 3-1.
Flight Plan page 3-i.
Flight Plan page 3-ii.
Flight Plan page 3-iii.
Flight Plan page 3-iv.
The moment the clock starts, the mission will begin to follow a carefully arranged schedule known as the Flight Plan. This thick 366-page document is the basic 'script' of the mission.
The Flight Plan is divided into six sections. Section I has general notes on the mission and its profile, while Section II lists the mission objectives. Section III, which is of course the thickest one, consists of 192 pages. Most pages cover one hour of flight time, although a 2 hours per page format is used for some quiet periods such as when the crew is asleep. Section IV has various charts on the spacecraft's consumables. Section V is a quick reference to the whole mission timeline, and the small Section VI on the very back has information on backup flight plans should they fail to leave Earth orbit for example, and have to commit to performing a much less glamorous mission.
An annotated sample page of the Flight Plan can be viewed from this link.
The Flight Plan does not contain actual instructions on how to operate the spacecraft. While the Flight Plan might say something like "Perform Stage Separation", the actual operating procedures are usually held in the checklists carried onboard. For time critical phases and complex phases of the mission, cue cards have been made that contain the basic procedures. These can be Velcroed onto the Main Display Console for easy reference without having to look away from the instrumentation.
A diagram from Apollo 12 flight materials showing the various locations of the cue cards can be viewed here.
An example launch cue card from Apollo 12 - very similar to those flown onboard Apollo 13 considering their nearly identical launch vehicle and mission profiles - can be viewed here.
Download MP3 audio file. Spacecraft communications.
000:00:02 Lovell: The clock is running.
A digital clock is set to start at lift-off, as well as the Event Timer, which starts counting from a preset time whenever set by the crew. This tells them how long they are into powered flight, and what to expect when all goes according to the plan.
We have commit and we have lift-off - at 2:13.
'Commit' means that the launch will now happen, one way or another.
Apollo 13 lifts off at 14:13 local time - 13:13 Houston time.
With the liftoff, the all-important crew abort system assumes Mode IA. Should there be a catastrophic failure of the booster during the first 42 seconds of powered flight, this mode will activate either automatically or at a crew command. In a IA abort, the Launch Escape System solid rocket engine will fire while automatic pyrotechnics separate the Command Module from the Service Module. At the same time, a small solid rocket motor known as the Pitch Control Motor will fire sideways to push the Command Module in a downrange direction, away from the trajectory of the Saturn V launch vehicle. RCS propellants in the Command Module are rapidly dumped through vents in the heat shield to protect the parachutes from the toxic chemicals they are comprised of. A few seconds later, a pair of small wings known as canards will snap open on the Launch Escape Tower and are used to modify the airflow around them and turn the Command Module to a suitable attitude for beginning a normal landing sequence, which will lead to splashing down into the Atlantic somewhere off Florida.
000:00:03 Swigert: Okay. P11, Jim.
Recreated view into Program 11 as displayed on the DSKY. Values given are those nominal for T+3 minutes.
Program 11 is known as the Earth Orbit Insertion Monitor. The computer runs Verb 06, Noun 62, which displays their velocity (in ft/s), rate of climb (ft/s) and their current altitude in nautical miles. Note that the computer does not have display capacity for the units nor for the decimal point! The crew had to know what they were looking at, and mentally make such notes.
Boost Card (MPAD)
To make the Program 11 display useful to the crew, a card is provided that contains the expected values for their velocity (VI), the rate of climb (known as H-dot) and their current altitude. This allows them to compare the computer readout to the pre-calculates values on the card and monitor the progress of their ascent.
Notice that VI does not start to increment from zero, but instead starts from 1,341 ft/s. This is the velocity that is imparted on the vehicle by the rotation of the Earth itself.
000:00:05 Lovell: Yaw program.
Saturn V yaws to steer away from the launch tower, seconds after lift-off. NASA 16mm film capture. Via JSC.
The Saturn V building up to 7.6 million pounds of thrust and it has cleared the tower.
000:00:10 Weitz (LCC): Clear the tower.
000:00:11 Lovell (onboard): Clear the tower.
000:00:12 Swigert: Clear the tower.
Apollo 13 clears the tower at Pad 39A.
The above picture with the major components of the booster/spacecraft stack labelled can be viewed from this link.
000:00:14 Lovell: Yaw complete. Roll program.
This is Mission Control, Houston. We appear to have a good first stage at this point.
000:00:16 Kerwin: Houston, Roger. Roll. [Long pause.]
Now that the Saturn V has cleared the launch tower, responsibility for the mission, and the CapCom duty as well, transfers to Mission Control, Houston.
The stack now rolls around from the 90-degree launch azimuth to the 72-degree azimuth required for their trajectory.
000:00:19 Lovell (onboard): 2,000 feet.
Download MP3 audio file. 2,302 kB. PAO loop.
Flight Dynamics Officer says the trajectory looks good; we show a one half mile in altitude at this time.
000:00:30 Kerwin: 13, Houston. Go at 30 seconds.
000:00:32 Swigert (onboard): Okay, you're right on, Jim. You're right on trajectory.
000:00:34 Lovell: Roll complete, and we're pitching.
After rising almost vertically, and having rolled to their launch azimuth orientation, they will now begin to slowly pitch over according to a pre-calculated steering program in the Instrument Unit. This will try to minimize the crosswind stresses on the booster.
000:00:36 Kerwin: Roger that. Stand by for Mode I Bravo.
000:00:42 Kerwin: Mark.
000:00:43 Kerwin: I Bravo.
000:00:44 Lovell: I Bravo.
Mode IB is in place from approximately 42 seconds into the mission up until they reach an altitude of 16.5 nautical miles, or 30.48 kilometers. This is approximately 1 minute, 56 seconds into the mission.
000:00:45 Swigert: RCS command. [Long pause.]
Altitude, 1.2 miles; velocity, 1,500 feet per second.
They are at 2,222 metres and moving at 457 metres per second.
000:00:48 Lovell (onboard): One-and-a-half g's. Okay, high Q coming up.
000:00:55 Haise (onboard): Cabin's coming down.
As they get higher, the air is becoming thinner, hence the cabin is starting to vent to maintain a pressure difference of about 6 psi or 40kPa between the CM cockpit and the outside atmosphere.
000:00:57 Lovell (onboard): Alt is looking good.
000:01:02 Swigert (onboard): Okay, you're right on...
000:01:03 Kerwin: 13, Houston. Go at 1. We show the cabin relieving.
Ken Mattingly manages a small smile as he witnesses his crewmates' ascent.
000:01:05 Swigert (onboard): Yes.
000:01:07 Lovell: 13; Roger. [Long pause.]
000:01:07 Swigert (onboard): You're right on, Jim.
68.4 seconds into the ascent of Saturn V, they reach Mach 1 and break the sound barrier.
And at 1 minute, 10 seconds; we show an altitude of 4.1 nautical miles; downrange, 1 mile.
In the first 70 seconds, they have climbed 7,593 meters upwards and travelled 1.6 km eastwards onto the Atlantic.
000:01:17 Lovell (onboard): Two g's.
All sources continue to report that we are Go; the trajectory on our plot board is right on the preplanned line.
At 81.3 seconds, they reach Maximum Dynamic pressure, or Max Q. This is the moment where the atmospheric resistance of the still thick layer of air is at its highest, working against the ever faster moving launch vehicle-spacecraft stack. It will then start to drop dramatically, as the air gets thinner and hence offers less resistance.
A graph showing the curve of the air resistance vs. their speed while in the atmosphere can be viewed here.
000:01:26 Lovell (onboard): Alt is looking good.
000:01:31 Swigert (onboard): Okay, you're right on at 01:30. 10 4 ... a little bit high ... we're a little bit high, about 0.4 of a mile.
000:01:37 Lovell (onboard): Got to speak louder.
And the booster engineer reports we are now through the region of maximum dynamic pressure and we're Go.
000:01:39 Swigert (onboard): Okay.
000:01:40 Haise (onboard): Cabin's looking good.
000:01:43 Lovell (onboard): 2½ g's and we're looking good in alpha.
000:01:50 Lovell (onboard): 40,000.
Commander's crucial instruments during ascent, highlighted. Modification of original via heroicrelics.org
Besides the FDAI 8-ball and the computer display, several other instruments are used by the commander to monitor their ascent. Lovell just mentioned the readouts of two of them. A gauge to the upper left of the FDAI shows the present g force as experienced. To the right of the FDAI, the indicator lights will warn him of any problem with the launch vehicle or its engines. Below the FDAI, another series of gauges shows the propellant pressures in the Saturn V. Also down there is the LV alpha/SPS Pc indicator. This round dial tells him the current angle of attack - how steeply they are riding up into the air, an important piece of knowledge for any aviator. To have it veer off their predicted value might indicate catastrophic trouble in the launch vehicle.
000:01:55 Kerwin: 13, Houston. Stand by for Mode I Charlie.
000:01:57 Lovell (onboard): Roger.
000:01:58 Kerwin: Mark.
000:01:59 Kerwin: You're I Charlie.
000:02:00 Lovell: Mark.
000:02:01 Lovell: I Charlie.
Mode IC covers the altitude from 16.5 nautical miles (30.48 km) up until the point of Launch Escape Tower jettison. After that they will move on to non-LES aborts.
000:02:02 Kerwin: And, 13, you are Go for staging.
000:02:04 Lovell: Go for staging. Roger.
000:02:05 Swigert: We're EDS, manual.
000:02:07 Lovell (onboard): Okay.
From now on, the Emergency Detection System will only begin the abort sequence at crew command.
Altitude now 17 miles, coming up on staging.
Their current altitude is 31.4 kilometers and rising as they prepare to separate the almost spent first stage.
000:02:08 Kerwin: Copy that. [Pause.]
000:02:11 Lovell (onboard): 3½ g's.
000:02:16 Lovell: Inboard. [Pause.]
Jim Lovell reports that the inboard engine has shut down as scheduled.
The center engine has been shut down, to lessen the dynamic stresses on the spacecraft structure from all five enormous engines cutting off simultaneously.
000:02:27 Kerwin: We confirm inboard out, 13. You're looking good.
A joyful Joe Kerwin at CapCom station. A relaxed John W. Young leans back and enjoys the show in Mission Control. A 16mm film capture. NASA via NARA.
000:02:29 Lovell: Roger. [Long pause.]
Coming up on 30 miles altitude.
Their current altitude is 55.6 kilometers and rising.
000:02:42 Lovell (onboard): Coming up on 4 g.
Jim announces their approach to 4 g's around the time that they indeed reach the maximum acceleration experienced during the launch - 3.83 g's. For this to occur at the very end of the first stage burn is natural - it is at this point that the four still burning F-1 engines are pushing a vehicle whose first stage is now nearly empty. Moreover, the reduced atmospheric pressure has raised the efficiency of the engines by about 20 per cent, increasing the thrust of each. by that proportion.
A graph of the G forces experienced by the Saturn V during their launch. From the Saturn V flight evaluation report. Click image for larger view.
The actually flown acceleration curve deviates from the nominal values - as seen on the graph - due to the unforeseen engine shutdown that will soon happen.
A diagram that illustrates the dramatic curve of the launch vehicle weight during ascent can be viewed here.
Their maximum g comes only a second before the four remaining S-IC engines cut off at 163.60 seconds.
000:02:45 Swigert (onboard): Got a little flash out the window.
The engine cutoff command is almost immediately followed by other automatic commands being sent to the the various systems onboard the S-IC and S-II stages that are responsible for separating the two booster stages from one another. At 164.1 seconds, four solid-fueled ullage engines are fired in the hollow aluminium ring that joins the first and second stages together. 'Ullage' is a remarkable term that originally referred to winemaking, and the empty space in a barrel. In rocketry, however, it refers to empty space in the fuel tanks and the need to deal with that to ensure that the fuel is pumped properly into the rocket engines. To accomplish this, the S-II stage ullage motors burn for four seconds to force the propellants downwards, and towards the bottom end of the rocket. This way the fuel will reach the fuel pumping system properly.
0.2 seconds after the ullage command, another signal fires eight retro motors in the S-IC stage. The retro units are solid-fueled rockets installed onto the fairings at the very bottom of the stage. Their purpose is to generate a brief burst of thrust in the direction opposite to the rocket's trajectory, meaning that once the two stages separate, the S-IC stage decelerates while the S-II stage continues to move forward. This is done to clear the two stages from one another and to avoid them colliding.
Download MP3 audio file. 6,925 kB. PAO loop.
These two videos, kindly donated by Stephen Slater, show the separation of Apollo 4's S-IC stage from its S-II across both planes. They were taken using film cameras mounted on either side of the S-II thrust structure, upper and lower. The cameras were ejected and, having parachuted into the ocean, were located by radio.
Both videos are presented here at 23.976 frames per second, a standard film frame rate. However, they were shot at about 4 times this rate, probably 96 frames per second, to provide a slow motion film for a more useful technical analysis. Therefore, although in real time 30 seconds elapse between each plane separation, the same events in these versions are separated by two minutes.
If the footage looks familiar, you are not wrong. Due to the spectacular nature of this film - originally taken for the much less romantic purpose of evaluating the separation from an engineering point of view - they've made themselves into nearly every documentary on the Apollo program. They are often misattributed to Apollo 11, however, which did not carry such cameras.
An Apollo Flight Journal essay on the onboard cameras can be accessed here.
The first stage separation occurred at 36.7 nautical miles, or 68.0 km of altitude. The spent S-IC stage still has an enormous amount of kinetic energy left, and will continue to coast higher to reach an apex altitude of 63.1 nautical miles, or 116.9 km. It is only then that the stage will begin to fall back towards the Earth, into a crash to the Atlantic Ocean some 355 nautical miles (658 km) away from the launch site.
000:02:48 Lovell: S-II ignition.
Diagram of the J-2 engine. Five of these power the S-II stage. A single J-2 powers the S-IVB stage.
The second, or S-II, stage of Apollo 13's Saturn V vehicle is 24.9 metres tall and is powered by the combustion of LH2 (liquid hydrogen) and LOX in a cluster of five J-2 rocket motors which generate a total thrust of 5,115kN (1.15 million pounds). A million litres of LH2, cooled to -253°C to get it into a liquid state, is loaded into the large, upper tank of the stage while 331,000 litres of LOX is loaded into the smaller, squat tank below. These tanks share a single insulated structure with only an insulated, common bulkhead between them. This was an innovation to save tons of weight in the launch vehicle, enabling a greater payload.
A diagram of the Saturn V's S-II stage can be viewed here.
The S-II stage carries five J-2 uprated engines which burn LH2 and LOX to produce up to 1,041 kN (234,000 pounds) thrust each. They are capable of being restarted in flight but this feature is only implemented in the engine used in the S-IVB, having to perform two separate burns during the mission. The S-II stage only needs to be fired once.
The thrust chamber and bell of each engine is fabricated from stainless steel tubes brazed together into a single unit. Supercold LH2 is pumped through these tubes to cool the thrust chamber and simultaneously prewarm and vapourise the cryogenic fuel. The engine carries two separate turbopumps, both powered in turn by the exhaust from a gas generator which burns the LH2/LOX mixture from the propellant tanks. The hot gas exhaust is fed from the gas generator, first to the fuel turbopump, then to the LOX turbopump before being routed to a heat exchanger and finally into the engine bell. The LH2 fuel and LOX outputs of both turbopumps are fed, via main control valves, to the thrust chamber injector via the LOX dome. Unlike the solid steel and copper injector of the F-1, the J-2 injector is fabricated from layers of stainless steel mesh sintered into a single porous unit. A solid LOX injector behind this carries 614 posts which pass LOX through the injector and into the combustion chamber. Each post has a concentric fuel orifice around it and these orifices are attached to the porous injector. The fuel delivery is arranged to ensure that about 5 per cent of the gaseous hydrogen seeps through the injector face to cool it, the rest passing through the annular orifices and into the chamber.
The ASI (Augmented Spark Igniter), fed with propellant and mounted to the injector face, provides a flame to initiate full combustion. Valves are provided to bleed the cryogenic propellants through the supply system well before ignition to chill all components to their operating temperatures. Otherwise the relatively warmer components would cause gas to be formed which would interfere with the engine's use of propellant as a lubricant in the turbopump bearings.
Attached to the engine is a spherical tank of gaseous helium which is located inside a larger tank of gaseous hydrogen fuel. This is the Start Tank. The high-pressure helium from the tank provides pneumatic operating power for the engine's valves while the high pressure hydrogen spins up the turbopumps before the gas generator is ignited. A PU (Propellant Utilization) valve on the output of the LOX turbopump can open to reduce the LOX flowrate. This adjusts engine thrust down to 890 kN (200,000 pounds) during flight to optimise engine performance. Although this is technically a way to throttle the engine, it is not considered a truly throttleable system.
To start the J-2 engine, spark plugs in the ASI and gas generator are energised. The Helium Control and Ignition Phase valves are actuated electrically. Helium pressure closes the Propellant Bleed valves, it purges the LOX dome and other parts of the engine. The Main Fuel valve and the ASI Oxidiser valves are opened. Flame from the ASI enters the thrust chamber while fuel begins to circulate through its walls under pressure from the fuel tank. After a delay to allow the thrust chamber walls to become conditioned to the chill of the fuel, the Start Tank is discharged through the turbines to spin them up. This delay depends on the role of the engine. A one second delay is used for the S-II engines. Half a second later, the Mainstage Control Solenoid begins the major sequence of the engine start. It opens the control valve of the gas generator where combustion begins and the exhaust supplies power for the turbopumps. The Main Oxidiser valve is opened 14° allowing LOX to begin burning with the fuel which has been circulating through the chamber walls. A valve which has been allowing the gas generator exhaust to bypass the LOX turbopump is closed allowing its turbine to build up to full speed. Finally, the pressure holding the Main Fuel valve at 14° is allowed to bleed away and the valve gradually opens, building the engine up to its rated thrust.
000:02:50 Swigert (onboard): [Garble.]
000:02:51 Haise (onboard): Yes.
000:02:51 Kerwin: Roger. [Pause.]
000:02:52 Lovell (onboard): We have half a g; looks good.
000:02:57 Swigert (onboard): Okay, 3 min. That's the babe.
000:03:00 Kerwin: 13, Houston. Trajectory is good; thrust is good.
000:03:04 Lovell: Roger. [Pause.]
000:03:04 Swigert (onboard): She's right on, Jim.
000:03:06 Haise (onboard): Stand by for tower Jett.
CapCom Joe Kerwin confirming to the crew that the second stage looks good at this point; we are now 46 miles high, 70 miles - 78 miles downrange.
Their altitude is 85.2 kilometers, and they have flown 125.5 km downrange.
000:03:15 Lovell: Skirt Sep [garble] Tower Jett.
Some 30 seconds after the stage separation, another automatic command fires the shaped charge that cuts the interstage off the bottom of the S-II stage. The relatively long interval between staging and the final separation of the interstage is to ensure that it does not collide with the engine bells of the S-II engines.
Should the interstage fail to separate, the launch rules indicate that the mission should be aborted. The 11,450 pounds (5,200 kg) weight would be a prohibitive additional mass to haul along. It would also be possible for the interstage ring to come partially or completely lose while out of control, colliding with the engines and causing devastating damage.
000:03:17 Lovell (onboard): Roger.
000:03:18 LMP/CDR: Tower Jett.
000:03:19 Swigert (onboard): Beautiful.
000:03:21 Kerwin: We confirm skirt SEP. Roger. Tower Jett; mode II, Jim. Looking good.
Artist impression of the tower jettison sequence.
Upon Tower Jett command, a small rocket motor with two exhaust ports fires at the top of the Launch Escape Tower. Pyrotechnics sever the structural and electric connections between the combined tower and Boost Protective Cover structure and the Command Module, allowing the small motor to send it well clear of the vehicle. The discarded equipment will then tumble down into the Atlantic Ocean.
000:03:22 Haise (onboard): Look at that.
000:03:24 Lovell: Mode II. [Pause.]
With the Launch Escape Tower gone, Mode II aborts are performed with the Service Module RCS jets or the Service Propulsion System. After separation from the launch vehicle, the Command Module would detach from the Service Module and then begin a landing sequence into the Atlantic Ocean.
At this moment, the Instrument Unit performs a switch to IGM or Iterative Guidance Mode. From now on, the spacecraft guidance system will use the input from its sensors - mainly the inertial platform - to perform changes in trajectory by adjusting engine gimbal pointing to compensate for any errors in their trajectory. These could be caused by air resistance or differences in expected engine performance, for example.
000:03:28 Haise (onboard): Look at the horizon out there.
000:03:29 Swigert (onboard): Yes. There it comes.
000:03:32 Haise (onboard): That plume!
Launch vehicle ...
000:03:33 Lovell: Guidance initiate. [Pause.]
000:03:34 Haise (onboard): That plume! Boy, is she boiling. That really...
000:03:38 Swigert (onboard): Here.
000:03:39 Haise (onboard): ...points away, there. Window is not too bad.
And Lovell reports that the Guidance System is correcting the small errors.
000:03:43 Kerwin: 13, Houston. Guidance is good, and the CMC is Go.
000:03:47 Swigert: Okay. Thank you.
000:03:48 Lovell: 13; Roger. [Long pause.]
000:03:49 Swigert (onboard): Okay, we're Mode II; I'm set for staging.
000:03:52 Lovell (onboard): Mode II. Got them all Rate Command and hang on.
Coming up now on 4 minutes. We are now at an altitude of 63 miles.
Their altitude is now 101 kilometers. This puts them over the 'Kármán line', the imaginary border between the atmosphere and space as defined by an international convention, and the mark between being an aviator and a space-flown astronaut. The US Air Force definition would put this limit at 80 kilometers, meaning that depending on the definition of space (or your service status!) Fred and Jack could have also entered the exclusive club about 40 seconds earlier. From now on, there's no questioning it.
000:04:00 Lovell (onboard): Four minutes.
000:04:03 Swigert (onboard): Okay, Jim, we're right on.
000:04:04 Lovell (onboard): Okay.
000:04:05 Swigert (onboard): Trajectory's looking good.
000:04:06 Lovell (onboard): Want a little bit more light?
000:04:07 Swigert (onboard): No, no. That's it...
000:04:08 Lovell (onboard): How's this?
000:04:09 Swigert (onboard): Yes. That's fine.
000:04:12 Lovell (onboard): 04:11.
000:04:13 Haise (onboard): Cabin's settled out very nicely.
000:04:14 Swigert (onboard): Yes.
000:04:15 Lovell (onboard): Okay.
At 4 minutes, 15 seconds, the trajectory.
000:04:16 Kerwin: 13, Houston. You are Go at 4 minutes. The little red lines are right on the little white lines down here.
000:04:22 Lovell: Sounds good. [Long pause.]
Trajectory displays filmed during the launch at Mission Control. NASA 16mm capture. Via JSC.
000:04:30 Lovell (onboard): Coming up on one g.
The S-II stage is lightening rapidly as propellant is burnt, meaning that that engines will be able to propel them faster, with an increasing acceleration.
000:04:31 Swigert (onboard): Boy, we're right on. We're about a mile and two-tenths high, though, but we're right on Vi and right on H-dot.
The S-IC first stage performed slightly better than expected, which might be responsible to their somewhat higher altitude than expected at this point.
Velocity now up to 11,000 feet per second. That's about 36 percent of the amount needed for a minimum orbit. We're now 75 miles in altitude.
In 4½ minutes, they have accelerated to a velocity of 3,352.8 m/s and are now 138.9 kilometers above sea level.
000:04:36 Lovell (onboard): That's [garble] One g. You could walk around here.
000:04:51 Swigert (onboard): I bet I never had such a view. Freddo [garble]...
222 miles downrange now. The EECOM reports...
They are 357 kilometers away from the launch site.
000:04:55 Kerwin: 13, Houston. Coming up 5 minutes. You're looking perfect. Over.
000:04:59 Lovell: 13; Roger. [Long pause.]
And EECOM reports that cabin pressure is sealed at 6.1 pound, which is normal. We are now 250 miles downrange, altitude 81 nautical miles.
They have travelled 402.3 kilometers and climbed to 150 kilometers of altitude.
000:05:04 Swigert (onboard): Okay. Watching 8.
And at 5 minutes 30 seconds into the launch, we continue to look very good on the second stage.
000:05:32 Lovell: Inboard.
Jim Lovell just reported the inboard engine has shut down as scheduled.
The PAO is making the call reflexively here, not realizing that something unexpected has indeed happened.
000:05:32 Swigert (onboard): Inboard.
000:05:36 Kerwin: Rog. We confirm inboard out. [Pause.]
An intense Joe Kerwin (and pipe) photographed during the ascent of Apollo 13. Backup Commander John W. Young is the third person to the right. NASA 16mm film. Via NARA.
The launch vehicle monitoring lights. Photographed inside Command Module Odyssey.
The visual cue for the central engine cut-off is the number 5 light coming on. Readers may recall that in the Ron Howard movie, the light blinks to show this malfunction state. This is creative license taken by the moviemakers - the lights would either be on, to show an abnormal state, or off, to indicate normal operation.
Dave Scott - Apollo 15 CDR/Apollo 13 film technical advisor, from 1998 correspondence: "In Apollo 13, the movie, the light was purposely made to blink to get the viewers' attention - the movie-makers knew the actual operation, but chose to take this license for dramatic effect (actually a pretty good license, as otherwise, the viewer would have missed the point!"
000:05:38 Lovell (onboard): That shouldn't have happened.
000:05:40 Swigert (onboard): No. That's 7:42. That's 2 minutes early.
Throughout the program thus far, the S-II stages have been prone to the pogo phenomenon, where interactions between the thrust of the engines, the effectiveness of the pumps, and inherent resonances of the propellant ducts and the vehicle's structure lead to longitudinal vibrations that can build up to damaging levels. The problem tended to appear towards the end of the S-II's burn and as a result, from Apollo 10 onwards, the centre engine was shut down about 1½ minutes before the cut-off of the other four. This fix appeared to work until Apollo 13 when the centre engine (number 5) of its S-II began to shake so violently that it tripped a switch that was determining if the thrust was sufficient. As a result, the engine was commanded off. Just before it did, it was oscillating back and forth on its crossbeam supports with a fearsome acceleration of ±33.7g.
Pogo here is not a fearsome NASA acronym but instead is a reference to the spring-like toy hopper popular at the time. The pogo was determined to have been caused by the S-II's LOX tank pressure being slightly low. Even though it was within spec, the low supply pressure was enough to allow a slight degree of cavitation (tiny bubbles that form and collapse) to occur within the inducer/impeller of the LOX turbopump. The cavitation only happened at the low-pressure part of the pressure cycle of an otherwise acceptable pogo vibration. Yet, because it affected the pump's efficiency, it also affected the engine's thrust, and did so in a way that caused a vicious circle of vibration to quickly build up. By the time the engine was commanded off, the deflection of the crossbeams said to be 'inches'.
Diagram of the POGO vibration event as detected by onboard instrumentation. From the Saturn V Flight Experience Report.
The four unaffected engines will be able to use all the remaining fuel. However, the early shutdown is not without cost as the S-II now has to accelerate the useless engine's dead weight for longer than it would otherwise have to. This will eat into the reserves of performance of the vehicle as a whole. Happily, it there will be sufficient margin to be able to continue Apollo 13's journey to the Moon.
The Emergency Detection System's rules do not suggest an immediate abort in the case of a single S-II engine lost. In fact, the vehicle is allowed to lose another of the S-II stage engines and still continue its ascent, unless it loses control.
000:05:44 Kerwin: 13, Houston. Stand by for S-IVB to COI capability.
000:05:48 Lovell: S-IVB to COI. Roger.
000:05:49 Kerwin: Roger. You've got it now, Jim.
000:05:52 Lovell: We've got S-IVB to COI. [Pause.]
In this abort mode, the spacecraft can make it to Earth orbit with the thrust provided by the S-IVB stage and the Service Module, but it will not have enough fuel left to attempt a lunar mission. A contingency Flight Plan for Earth orbital operations would then be exercised, should the spacecraft itself be sound still.
000:05:53 Swigert (onboard): Okay. Gim(bal) motors, Jim. Set 1.
000:05:55 Lovell (onboard): Okay. Pitch 1.
000:05:57 Swigert (onboard): Good.
000:05:58 Lovell (onboard): Yaw 1.
000:05:59 Swigert (onboard): Good. Pitch 2.
That booster reports that the inboard engine shutdown was a bit early. We are continuing to burn on the 4 outboard engines.
NASA bosses Chris C. Kraft (Deputy Director, MSC) Jim McDivitt (Manager, Apollo Spacecraft Program) and Robert Gilruth, (Director, MSC) observe the launch in Mission Control from the managers' station.
000:06:00 Lovell (onboard): Pitch 2.
000:06:01 Swigert (onboard): Good.
000:06:02 Lovell (onboard): Yaw 2 ...
000:06:03 Kerwin: You're Go at 6 minutes, 13.
000:06:06 Lovell/Swigert: Go at 6.
000:06:10 Lovell: And, Houston, what's the story on engine 5?
000:06:14 Kerwin: Jim, Houston. We don't have a story on why the inboard out was early, but the other engines are Go and you are Go. [Pause.]
000:06:21 Lovell: Roger. [Long pause.]
000:06:24 Haise (onboard): Okay. We're - we're a little bit low on H-dot, now, but that's to be expected.
The loss of the central engine has deprived them of one fifth of their thrust, which means that their climb rate (the H-dot) has been reduced, but not to an alarming rate. Now that they are above most of the atmosphere, they can simply burn longer to reach the altitude and speed they require.
000:06:28 Lovell (onboard): Okay. We're Mode II, gentlemen, Mode II.
At 6 minutes, 40 seconds...
000:06:41 Kerwin: 13, Houston. Still looking good. Your gimbals are good; trim is good.
000:06:45 Lovell: Roger. [Pause.]
000:06:46 Lovell (onboard): We just checked the trim. It doesn't fit.
000:06:53 Kerwin: 13, Houston. Level sense arm time, 8 plus 38 nominal; S-II cut-off time, 9 plus 48. Over. [Pause.]
000:07:02 Lovell: Roger. Nominal on the level sense arm, 9:48 on the S-II cut-off.
The level sense arm announcement informs the crew that the S-II stage automatic shutdown system has been enabled. There are five fuel level sensors and five oxidiser level sensors, and once two of them read either tank as empty, the engine cut-off sequence begins. Both the S-IC and S-II stages burn for as long as possible, to get the maximum amount of propulsion out of both. Their prolonged S-II stage burn due to the center engine cut-off is a good example of this. To drop it off with useful fuel onboard would not be economical.
000:07:06 Swigert (onboard): It's going to run...
000:07:08 Kerwin: That's affirmative, and stand by for S-IVB to orbit.
000:07:11 Kerwin: Mark.
000:07:12 Kerwin: You have S-IVB to orbit, Jim.
000:07:14 Lovell: Roger. We have S-IVB to orbit. [Long pause.]
They will now be able to make a nominal Earth orbit with the thrust of the S-IVB stage.
000:07:23 Lovell (onboard): Didn't like that inboard.
We still have four good engines on the Saturn second stage. We show an altitude of 96 nautical miles, 545 downrange.
In seven and a half minutes, they have travelled 877 kilometers and climbed to 177.8 kilometers of altitude. They are almost at their planned orbital altitude - now the important part is to keep thrusting horizontally to gain enough velocity to reach and then maintain orbit.
000:07:32 Swigert (onboard): Okay, we're 1,400 feet a second low on Vi. That's not too bad.
000:07:38 Lovell (onboard): Watch the trajectory closely, Jack.
000:07:41 Swigert (onboard): Yes, [garble].
And at 7 minutes, 45 seconds; booster reports we are Go. All four engines remaining are looking good.
000:07:48 Swigert (onboard): We're right at 8 [garble] - H-dot is a little bit low; Vi is low, but that's understandable.
000:07:53 Lovell (onboard): Okay.
000:07:56 Swigert (onboard): You're S-IVB to orbit capability now.
The early shutdown on the center engine would cause no problem. We would burn a little bit longer than normally scheduled...
000:08:02 Kerwin: 13, Houston. Looking good at 8 minutes. [Long pause.]
000:08:04 Lovell: 13; Roger.
000:08:05 Lovell (onboard): How's those systems, Fred? Are there any...
000:08:08 Haise (onboard): They're looking good.
000:08:13 Swigert (onboard): Okay, now, H-dot is low, Jim [garble]. S-IVB ought to pick you up.
And at 8 minutes, 17 seconds; we show a velocity of 18,000 feet per second. That's about 71 per cent of the amount needed for minimum orbit.
Their velocity is now 5,486.4 m/s.
000:08:19 Lovell (onboard): Yes. Hey, I got a - We got a funny vibration
000:08:27 Haise (onboard): Yes. Yes, there was a bit of noise, there. Yes.
000:08:31 Swigert (onboard): [Garble].
At 8 minutes, 35 seconds; continuing to burn on the second stage. All four remaining engines looking good at this point.
000:08:45 Kerwin: Apollo 13, Houston. Mark, level sense arm.
000:08:48 Lovell: Mark level sense arm. Roger. [Pause.]
At 08:57 they reach maximum acceleration generated by the S-II stage, 1.66g's.
000:08:58 Kerwin: Apollo 13, Houston. At 9 minutes, you're Go; the CMC is Go.
000:09:02 Swigert: Okay, Joe.
000:09:04 Lovell: 13; Roger. [Long pause.]
Our predicted shutdown time on the second stage is 9 minutes, 48 seconds. Flight Director Milton Windler getting a staging status now from his flight controller.
000:09:19 Kerwin: 13, Houston. You are Go for staging.
000:09:22 Lovell: 13; Roger. Go for staging. [Long pause.]
000:09:45 Kerwin: Apollo 13, Houston. Stand by for mode IV capability.
000:09:48 Kerwin: Mark.
000:09:49 Kerwin: You have mode IV, Jim.
000:09:50 Lovell: Mode IV. Roger. Staging. [Pause.]
At 09:52, the outboard engines on the S-II stage cut off. Less than a second later, two solid fuel ullage rockets fire on the S-IVB stage to settle its propellants, and nearly simultaneously explosive devices separate the S-II and S-IVB stages above the conical interstage. Four small retro motors fire in the interstage to push the spent S-II stage away from the S-IVB stage.
The single J-2 engine on the S-IVB stage is ignited as per the same procedure as during the S-II stage ignition. The biggest difference is that a three-second chilldown of the engine thrust chamber is enacted by having the liquid fuel flow through it, instead of just one second, as on the S-II stage.
In Mode IV aborts, the spacecraft is separated from the S-IVB stage and the SPS engine alone is used to insert them into an Earth orbit. A contingency Flight Plan could then be enacted to perform an Earth orbital mission instead of the lunar landing.
And Lovell reports staging.
000:09:57 Kerwin: Roger. Staging.
The J-2 engine starts and gears up to full power in approximately 2.5 seconds, reaching the mainstage of burn.
Download MP3 audio file. PAO loop.
000:10:00 Lovell: And S-IV ignition, Houston.
After separation, as with the first stage, the S-II will continue to coast on its own trajectory until it reaches an apex height of 103.0 nautical miles or 190.7 kilometers. In fact, the spent stage goes as high up as the nominal parking orbit for the remaining Saturn V stack, although of course lacking the speed to sustain an orbit. Its suborbital trajectory will then take it down to the Atlantic for impact some 2,452.6 nautical miles (4,542.3 km) from the launch site.
The third stage of the Saturn V, called the S-IVB for historical reasons, could be described as a smaller version of the S-II stage in that it also consists of a single tank structure with a common bulkhead between the LH2 and LOX compartments. These propellants, which are stored at the same supercold temperatures as for the S-II, are burned in a single J-2 engine which yields a thrust of 890 kN (a shade over 200,000 pounds). The engine's capability for restarting is utilised for the boost out of Earth orbit to the Moon. The construction of the S-IVB's propellant tank differs from the S-II stage by having the insulation on the inside of the tank's metal skin, a detail which made manufacture easier by not having to develop a bonding system which had to work at only 20 degrees above absolute zero. With the insulation between it and the propellant, it would be substantially warmer.
A diagram of the Saturn V S-IVB can be viewed here.
000:10:04 Kerwin: Roger that, Jim. Thrust looks good.
000:10:07 Lovell: Roger. [Pause.]
000:10:17 Kerwin: 13, Houston. You're looking good. Trajectory, guidance, CMC are all Go.
000:10:23 Lovell: Thank you, Joe. [Long pause.]
000:10:28 Haise (onboard): Right on 8; good on H-dot; 200 feet a second low on Visp.
And at 10 minutes, 30 seconds; we are now at an altitude of 1,080 miles down range.
The PAO means distance, not altitude, here. They are 1,738 kilometers away from the launch site.
000:10:32 Lovell (onboard): Remember, we're Mode IV now.
000:10:34 Haise (onboard): Yes, I got that. Mode IV.
000:10:46 Haise (onboard): Looks good...
000:10:49 Lovell (onboard): What?
000:10:51 Haise (onboard): Everything looks good.
000:10:54 Lovell (onboard): Everything looking good.
000:10:57 Haise (onboard): We're looking good, Jim; trajectory's looking good.
000:11:00 Lovell (onboard): Okay, [garble].
000:11:09 Kerwin: 13, Houston. At 11 minutes, you're Go. Predicted cut-off on the S-IVB is 12 plus 34. Over. [Long pause.]
000:11:15 Swigert (onboard): [Garble]
000:11:19 Lovell (onboard): What?
000:11:23 Haise (onboard): Okay, going to [garble] dead band now, guys. We're 102.5 - shutdown velocity...
000:11:32 Lovell (onboard): 25,562.
000:11:35 Kerwin: Apollo 13, Houston. You're Go at 11½, and predicted cut-off time is 12 plus 34. Over. [Pause.]
000:11:42 Lovell: Understand; 12 plus 34 predicted cut-off time.
000:11:45 Kerwin: That's affirm. [Long pause.]
000:11:46 Haise (onboard): 25,562 looks good.
Fred is most likely reading out their predicted velocity at the engine cut-off time, which is more than enough for maintaining orbit.
Coming up on 12 minutes. Still looking good.
000:11:58 Swigert (onboard): Okay - Do we shut down at - Freddo?
000:12:02 Haise (onboard): Yes.
000:12:03 Swigert (onboard): What's - Shutdown is when?
000:12:05 Haise (onboard): [Garble] you get the last page, Jack; you got the clean-up stuff.
000:12:14 Lovell (onboard): Stand by for SECO.
000:12:15 Haise (onboard): All the systems stuff. You got to [garble] SECO.
000:12:18 Swigert (onboard): Yes.
000:12:20 Haise (onboard): I'm going to just jump right in [garble].
We're standing by for a crew report on the third stage shutdown.
The S-IVB engine cuts off at 750 seconds; 12 minutes, 30 seconds into the flight. This is approximately 44 seconds late due to the prolonged S-II burn.
000:12:31 Lovell: SECO.
000:12:32 Kerwin: Copy SECO, Jim. We're looking at the DSKY.
000:12:36 Lovell: Roger. [Long pause.]
The launch vehicle determines that they have secured their orbit at 759 seconds, or 12 minutes, 39 seconds GET.
And the Flight Dynamics Officer says at first glance we look good on the orbit.
Stellar inertial vs. orbital rate orientation. Diagram by David Woods.
At 000:17:50 GET, the IU commands the stack into a local horizontal attitude, or orbital rate. In this orientation, they rotate slowly in pitch to maintain one side of the spacecraft always facing the Earth, coasting with the pointy end forward. This very slow motion of the stack reduces the cryogenic fuel sloshing inside the almost full tanks of the booster. It will also point the spacecraft optics towards space, to give Jack the chance to calibrate his optics and the guidance platform.
When the IU is in charge of maintaining their attitude during the orbit, it will do so with the Auxiliary Propulsion System, or APS.
S-IVB Auxiliary Propulsion System diagram
The two APS modules on the S-IVB have three 150-pound thrusters and one 70-pound ullage thruster each. These allow the Instrument Unit fine attitude control of the stack without use of the Service Module's RCS thrusters.
The two APS units can be used for three-axis control of the S-IVB/Apollo stack while in orbit. The ullage thrusters are used to settle the fuel before engine burns.
Each APS thruster uses hypergolic fuels that explode on contact, and helium for pressurization. The interior of the rocket engine is lined with an ablative material that cools the thruster via controlled burning off.
000:13:02 Kerwin: Apollo 13, Houston. You have a Go orbit all sources, and the booster is safe. Over.
000:13:07 Lovell: Go orbit and the booster is safe. Thank you, Joe.
At 000:13:09, a propulsive venting of the liquid H2 begins by opening a valve on the S-IVB stage. This both keeps the propellants settled in their tanks and prevents the tank from pressurizing too much due to the heat leak. The valve will be closed before the second S-IVB burn to build up pressure instead of relieving it.
000:13:10 Kerwin: Don't mention it. [Long pause.]
000:13:30 Kerwin: 13, Houston. We copy your Noun 44.
Onboard, Swigert has pressed the Verb button on the DSKY keyboard and then entered Verb 82 to display Noun 44. This gives them a display of their orbit in terms of HA and HP - or the highest and lowest points of their elliptical orbit around Earth. Mission Control can read their computer display over the telemetry radioed down to Earth.
000:13:34 Swigert: Okay, Joe.
The booster engineer reports at this time that the S-IVB third stage looks good. Being configured now for orbital operations. We're standing by for a confirmation from the Flights Dynamics Officer about our preliminary orbit."
Mission Control will now hurry to determine the newly launched spacecraft stack's orbit with the use of the onboard data as well as radio tracking information.
The S-IVB and its J-2 begin first preparations for their upcoming Translunar Injection burn as well. The engine's start tank is filled with liquid and gaseous hydrogen during the burn. It will slowly begin to gain the pressure needed for a restart of the engines by allowing the temperature inside the tank to increase through heat leak as the sunlight warms it, and hence causes the supercooled liquid to warm also, increasing its pressure. A minimum of 80 minutes is required for the pressure in the start tank to rise sufficiently for the restart. This minimum wait will also let the other components to cool down after the hardships of the first S-IVB burn.
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Pre-Launch Activities and the Crewman Change Journal Home Page Day 1, part 2: Earth Orbit and Translunar Injection