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| Journal Home Page | Earth Orbit and Translunar Injection |
| F-1 ignition sequence begins | T-8.9 seconds |
| Lift-off | 000:00:00 |
| Pitch and roll maneuver | 000:00:13 |
| End roll maneuver | 000:00:34 |
| Abort mode I-B | 000:00:42 |
| Max-Q | 000:01:23 |
| Abort mode I-C | 000:01:57 |
| S-IC inboard cut-off | 000:02:15 |
| S-IC/S-II staging | 000:02:42 |
| Interstage separation | 000:03:12 |
| LET jettison & Abort mode II | 000:03:18 |
| S-IVB to COI (Abort mode III) | 000:05:27 |
| S-II inboard cut-off | 000:07:41 |
| Mixture ratio change | 000:08:18 |
| Abort mode IV | 000:09:00 |
| S-II/S-IVB staging | 000:09:09 |
| Parking orbit insertion | 000:11:49 |
[The transcript begins over two-and-a-half hours before launch. With the Apollo 11 spacecraft sitting atop its Saturn V launch vehicle on Pad 39A, announcements on the progress of the countdown are made by the Public Affairs Officer (PAO) Jack King, the 'Voice of Apollo'. The record of communications between the crew and the Mission Control Center, through 'CapCom' (the Capsule Communicator) commences soon after lift-off. This section of the journal will follow the flight through the launch and staging of the Saturn V launch vehicle, and insertion into Earth orbit about 12 minutes later. It concludes with the confirmation of orbital parameters and the safe check-out of the S-IVB third stage in orbit.]PAO (Public Affairs Officer): This is Apollo Saturn Launch Control; T minus 2 hours, 40 minutes, 40 seconds and counting. At this time, the prime crew for Apollo 11 has boarded the high-speed elevator from inside the A level of the mobile launcher which is the second level inside the launcher. This is the high-speed elevator; 600 feet per minute which will carry them to the 320-foot level, the spacecraft level. Shortly, we'll expect astronauts Neil Armstrong and Michael Collins to come across Swing Arm 9, the Apollo access arm, and proceed to the white room and stand by to board the spacecraft. The third member of the crew, astronaut Edwin Aldrin, will be the last one to board the spacecraft, will stand by in the elevator seated in a chair while his two comrades first board the spacecraft. Once Armstrong, who sits in the left-hand seat, and Collins, who will sit in the right-hand seat during lift-off are aboard, then Aldrin will be called and he will take his seat, the middle seat in the spacecraft, The spacecraft Commander Neil Armstrong and the Command Module Pilot Michael Collins now proceeding across the swing arm into the small white room that attaches at the spacecraft level. In the meantime, about 100 feet below, we have a technician – a team of technicians working on a leaking valve which is a part of the Ground Support Equipment, a part of the system that's used to replenish the fuel supply for the third stage of the Saturn V rocket. He is proceeding to tighten a series of bolts around this valve in the hope that this will correct the leak. Once the technicians do depart, the hydrogen will again be flowed through the system to assure that the leak has been corrected. The spacecraft Commander Neil Armstrong and CMP, the Command Module Pilot Mike Collins, now standing by in the white room. T minus 2 hours, 38 minutes, 45 seconds and counting; this is Launch Control.
[MP3 audio file. 1,024 kB.]PAO: This is Apollo Saturn Launch Control; T minus 2 hours, 34 minutes, 44 seconds and counting. The spacecraft Commander Neil Armstrong now aboard the Apollo 11 spacecraft at the 320-foot level at the pad. We had it logged having the commander go over the sill into the cabin at 6:54am Eastern Daylight. Since that time, the commander has now been tied into the system and has checked in over the communication lines. He was wished a 'Good morning' by the spacecraft test conductor Skip Chauvin and Armstrong in return said it looks like a good morning. In the meantime, 120 feet below him, the technicians continuing to work to tighten bolts around a leaking valve associated with the system that replenishes hydrogen fuel for the third stage. To repeat once again, this is not a problem on the launch vehicle itself, but on the ground support equipment associated with it. T minus 2 hours, 33 minutes, 45 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 1,031 kB.]PAO: This is Apollo Saturn Launch Control; T minus 2 hours, 30 minutes, 55 seconds and counting. Right on the hour, the Command Module Pilot, astronaut Michael Collins, who'll be sitting on the right-hand side of the spacecraft during lift-off, boarded the spacecraft. We had it logged at 7am Eastern Daylight Time. The third member of the crew, astronaut Buzz Aldrin, standing by in the elevator around the corner along the swing arm from the White Room and the spacecraft at the 320-foot level. 120 feet below, technicians still working on some bolts that surround a leaking valve that is associated with a system that replenishes the hydrogen fuel supply to the third stage of the Saturn V rocket. Our countdown proceeding at this time; coming up toward the 2 minute and 30 minute ma... 30 second... the 2 hour and 30 minute mark in the count. This is Kennedy Launch Control.
[MP3 audio file. 1,632 kB.]PAO: This is Apollo Saturn Launch Control; T minus 2 hours, 23 minutes, 46 seconds and counting. The third member of the Apollo 11 prime crew now aboard the spacecraft. We had it logged at 7:07am Eastern Daylight Time when astronaut Buzz Aldrin boarded the spacecraft. He'll sit in the middle seat during lift-off. As Lunar Module Pilot, his normal position would be on the right-hand side. However, due to crew preference, we have the Commander of course, Neil Armstrong, sitting on the left-hand side. The Lunar Module Pilot for the overall flight, Buzz Aldrin, sitting in the middle seat, and the Command Module Pilot Mike Collins sitting in the right-hand seat at lift-off. Down below, at the 200-foot level, our technicians still hard at work still tightening bolts around a valve associated with the system that replenishes the hydrogen fuel for the third stage of the Saturn V launch vehicle. This is ground support equipment located on the tower at the pad at the 200-foot level. He continues to work at the 200-foot level as the crew in the White Room does the same with the three astronauts aboard. We actually have a fourth astronaut still aboard the spacecraft at this time, astronaut Fred Haise, who is the back-up Command Module Pilot. He is in the Lower Equipment Bay of the spacecraft, giving a helping hand to the three prime crewmen as they start to perform some of their preliminary checks here as we head down over the final 2 hours – 2½ hours of the countdown. We're at T minus 2 hours, 22 minutes, 11 seconds and counting; this is Kennedy Launch Control.
[In fact, Fred Haise is the back-up Lunar Module Pilot. The other back-up crew members are Commander Jim Lovell and Command Module Pilot Bill Anders.]PAO: This is Apollo Saturn Launch Control. We've just passed the 2-hour, 21-minute mark in our countdown and we are proceeding at this time. At the 320-foot level, all three astronauts now aboard the spacecraft. Just a few minutes ago, astronaut Buzz Aldrin came in and took the center seat to join Neil Armstrong on the left and Mike Collins on the right. These are the positions they will fly at lift-off. During the process of getting the astronauts checked into the spacecraft, communication cables must be attached to their suits. They also have to hook into the suit circuit system of the spacecraft that brings oxygen into their suits. They are helped by a fourth astronaut on board, the back-up Command Module Pilot, astronaut Fred Haise, who is in the Lower Equipment Bay, and one of the suit technicians, who's located behind them to give a hand as they check in. We've heard from Neil Armstrong, and now we've also heard from Mike Collins on comm checks, and we're standing by for further reports as the checkout continues. 120 feet down, the work continues on a leaky valve at the 200-foot level. This is ground support equipment. The technicians still hard at work tightening bolts around that valve at this time. 2 hours, 19 minutes, 45 seconds and counting; this is Kennedy Launch Control.[When the crew arrived at the spacecraft they were already suited up and sealed off from Earth's natural atmosphere of nitrogen and oxygen. By the time they are ascending, they will have been breathing pure oxygen of around three hours and have flushed dissolved nitrogen from their blood. This is to guard against the possible formation of nitrogen bubbles in their blood as the spacecraft air pressure drops to its nominal value of about a third of sea-level pressure, and in case of an unintended decompression of the spacecraft. Between the suiting-up room and the spacecraft, each crewman carried his own oxygen supply in a suitcase-sized unit. Image KSC-69PC-399 shows Neil leading his crew across Swing Arm 9 carrying his supply.]
[MP3 audio file. 1,582 kB.]PAO: This is Apollo Saturn Launch Control; T minus 2 hours, 10 minutes, 35 seconds and counting. At the 320-foot level, the fourth astronaut aboard the spacecraft regretfully leaves at this time. Astronaut Fred Haise is about to come out after giving the three prime crewmen a hand in their preliminary checkouts aboard. Fred Haise will be coming out shortly. In the meantime, 120 feet below, where we have that problem with the leaking valve, the technicians have completed their work and they are in the process now of departing from the launch pad. In a short while, we'll start flowing hydrogen again back through the general replenishing system to continue the top-off – the supply of the hydrogen fuel to the third stage of the Saturn V launch vehicle. The spacecraft Commander Neil Armstrong has completed a series of checks called abort advisory system checks. This is where certain key crewmen on the ground, members of the launch team, can send signals to the commander in the spacecraft; light cues that would indicate a difficulty during the flight in which he could take abort action if he determined that such action was necessary. These checks have been completed and Neil Armstrong confirmed that the lights came on in the console in front of him, the panel in front of him as these lights were operated from the ground here in the Launch Control Center. All still going well with our count. We will stand by as we again bring hydrogen back to the third stage. We will see how that operates. We're now at T minus 2 hours, 9 minutes, 4 seconds and counting and this is Kennedy Launch Control.
[MP3 audio file. 1,220 kB.]PAO: This is Apollo Saturn Launch Control; T minus 2 hours, 7 minutes and counting. At this time we're just in the process of closing the hatch on the Apollo 11 spacecraft. Several of the close-out crew shook hands with the astronauts and then proceeded to close the hatch on direction from the Spacecraft Test Conductor Skip Chauvin. We had it logged as the hatch being closed and tightened – still being tightened right at this time which is 25 minutes past the hour. Once the hatch is closed, we will start a cabin purge to condition the cabin inside. The three astronauts, of course, are on pure oxygen in their space suits on the suit circuit. We will produce a cabin atmosphere in the spacecraft of a 60/40 combination; 60% oxygen and 40% nitrogen. This is the atmosphere used for lift-off. Once that is accomplished, the close-out crew will be ready to put the Boost Protective Cover on the hatch and continue with their close-out. The hatch being closed at this time. We are proceeding. We'll stand by to see how our hydrogen condition is, as far as replenishing the hydrogen fuel supply with the third stage of the Saturn V. 2 hours, 5 minutes, 50 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 1,411 kB.]PAO: This is Apollo Saturn Launch Control. We're at T minus 2 hours, 55 seconds and counting. We're approaching the 2-hour mark in our countdown and we appear to be proceeding satisfactorily at this time. The crew aboard the spacecraft, the 320-foot level, the hatch is closed and we're beginning to purge the cabin to bring it to the proper atmosphere for launch which is a combination of oxygen and nitrogen; 60% oxygen and 40% nitrogen atmosphere. Of course, the astronauts themselves are breathing pure oxygen through their space suits. Coming up shortly will be another key test in which both the launch crew for the – the launch vehicle crew and the spacecraft team combine together with the Commander Neil Armstrong to make a thorough check of the Emergency Detection System. This is the system that will signal the astronauts in the cabin if anything goes wrong below them. We used a ground-based computer to accomplish this test. It's rather lengthy as these tests go, using a computer. It will take some 30 minutes. Neil Armstrong will be doing most of the work in the spacecraft, responding as different cue lights, signifying different difficulties, are presented to him. The abort panel, of course, is across from the commander on the left-hand side, the left-front of the spacecraft. Our countdown continuing; T minus 1 hour, 59 minutes, 34 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 966 kB.]PAO: This is Apollo Saturn Launch Control; T minus 1 hour, 50 minutes, 55 seconds and counting. We're proceeding with the countdown with the Apollo 11 mission at this time and it's going satisfactorily. At this point, the spacecraft Commander Neil Armstrong in the process of working the Emergency Detection System test. This is a check of the Emergency Detection System working with the launch crew here in the firing room and also the spacecraft team in control rooms back at the Manned Spacecraft Operations building here at the Kennedy Space Center. All going well with these tests at the present time. We're flowing hydrogen back into the third stage of the Saturn V launch vehicle after having difficulty with that leaking valve. It appears that we are bypassing the use of the valve directly in loading the hydrogen aboard, but we are getting the hydrogen back in to replenish the supply. All appears to be going well at this time. Weather is Go. We're coming up on 1 hour and 50 minutes. This is Kennedy Launch Control.
[MP3 audio file. 1,205 kB.]PAO: This is Apollo Saturn Launch Control at T minus 1 hour, 40 minutes, 55 seconds and counting. The countdown still proceeding very satisfactory at this time as we lead up toward our planned lift-off time of 9:32am Eastern Daylight. The spacecraft Commander Neil Armstrong continuing this extensive series of checks of the Emergency Detection System, working with both the launch vehicle test crew and the spacecraft crew. This is a key test and a very thorough test to assure ourselves, before we commit to lift-off, that all the emergency detection techniques inside the launch vehicle are operating properly here on the ground, so if required in flight, the spacecraft commander and, of course, his two fellow astronauts could be signalled of a difficulty inside the rocket and could take proper abort action as required. Thus far, the three astronauts aboard the spacecraft have just been giving businesslike responses back to the directions and checks, working with the Spacecraft Conductor Skip Chauvin as he runs down his procedures as the countdown continues. T minus 1 hour, 39 minutes, 46 seconds and counting; this is Launch Control.
[MP3 audio file. 1,507 kB.]PAO (Public Affairs Officer): This is Apollo Saturn Launch Control; T minus 1 hour, 30 minutes, 55 seconds and counting. All elements are Go with the countdown at this time, the countdown aimed at landing two astronauts on the Moon. At this time the Spacecraft Test Conductor Skip Chauvin going through some checks with astronaut Mike Collins aboard the spacecraft. We're winding up this important Emergency Detection System test that Neil Armstrong has been participating in. Meanwhile, at the 320-foot level, the close-out crew now placing the Boost Protective Cover over the hatch now that we have completed the cabin purge and have the proper environment inside the cabin. We have also performed leak checks to assure ourselves that the cabin atmosphere is valid. This Boost Protective Cover is used during the early phases of the powered flight and it is jettisoned with the escape tower shortly after second stage ignition. Here in the firing room, the launch vehicle test team's still keeping a close eye on the status of the propellants aboard the Saturn V launch vehicle. We're back to 100 percent supply with the liquid hydrogen fuel in the third stage. This problem with the leaking valve is no problem at this time. We've actually bypassed the valve but we are maintaining our hydrogen supply aboard the vehicle. All aspects Go. The weather is very satisfactory for launch this morning. A thin cloud cover about 15,000 feet. Temperature at launch time expected to be about 85 degrees. T minus 1 hour, 29 minutes, 30 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 956 kB.]PAO: This is Apollo Saturn Launch Control; T minus 1 hour, 20 minutes, 55 seconds and counting. All still Go with the countdown for Apollo 11 at this time. At this point in the countdown, spacecraft Commander Neil Armstrong once again appears to be the busiest worker in the spacecraft as he is performing a series of alignment checks associated with the guidance system in the spacecraft. He's working these checks with the Spacecraft Test Conductor as the Spacecraft Test Conductor reads out the various procedures and Armstrong responds to them. The astronauts aboard the spacecraft also were informed by the spacecraft conductor a short while ago that the launch vehicle is Go at this time. The hydrogen problem that we did encounter earlier has been solved. "That's real good news," said Armstrong and then he went back to work shortly thereafter. We're now coming up on the 1 hour, 20 minute mark in the countdown; this is Kennedy Launch Control.
[MP3 audio file. 1,600 kB.]PAO: This is Apollo Saturn Launch Control; T minus 1 hour, 11 minutes, 55 seconds and counting. The countdown for Apollo 11 still going very satisfactorily at this time. In most cases, we're a matter of 5 or 10 minutes ahead of the countdown procedures. The crew in the white room at the 320-foot level who have been aiding the astronauts up to this time are just in the process of finishing up their work. They've been advised by the Spacecraft Test Conductor that they'll probably be able to move out in about 3 minutes or so. Once this is accomplished, once the close-out crew does depart, we'll be ready to move that swing-arm back, swing-arm 9. It will be moved 12 degrees away from the spacecraft hatch; this is about 5 feet away from the hatch. Once this is accomplished, we will arm the pyrotechnic systems in the spacecraft so in the event of a possible catastrophic condition below them with the launch vehicle, while still on the pad, the astronauts could fire that escape rocket and separate from the rocket in difficulty. The close-out crew about to depart at this time. That swing-arm remains about 12 degrees away from the spacecraft hatch as mentioned - 5 feet or so until the 5-minute mark in the count when it's fully retracted to its fall-back position. The obvious reason here is in the event we do have to get the astronauts out in a hurry, the swing-arm is in a stand-by position and could be moved rapidly back to the hatch... to the hatch level, so the astronauts could depart in the event of an emergency. We're coming up on T minus 1 hour, 10 minutes, and 20 seconds; this is Kennedy Launch Control.
[MP3 audio file. 1,581 kB.]PAO: This is Apollo Launch Control at 1 hour, 7 minutes, 25 seconds and counting; countdown still proceeding satisfactorily. For those people who would like to synchronize their watches in relation to the count, we'll synchronize on 26 minutes past the hour, which is now about 65 seconds away. We'll count down the last 5 seconds to 26 minutes past the hour. We're now one minute away from 26 minutes past the hour. In the meantime, we do have information from the Civil Defense Agency in the area. The estimate is more than a million persons are in the immediate area in Brevard County to watch the launch. Now 40 seconds away from 26 minutes past the hour. Civil Defense Agency reports further that there is extensive heavy traffic, a number of traffic jams, particularly in the area of Titusville and the US1 and Route 50. Countdown still progressing satisfactorily. 15 seconds away from 26 minutes. 5, 4, 3, 2, 1, Mark. 8:26 am Eastern Daylight Time. We're now 1 hour, 5 minutes 55 seconds and counting as it was announced at that point. This is Kennedy Launch Control.
[MP3 audio file. 1,185 kB.]PAO: This is Apollo Saturn Launch Control; T minus 61 minutes and counting - T minus 61 minutes on the Apollo 11 countdown, and all elements are Go at this time. Astronaut Neil Armstrong has just completed a series of checks on that big Service Propulsion System engine that sits below him in the stack. We want to assure ourselves before lift-off that that engine can respond to commands from inside the spacecraft. As Neil Armstrong moved his rotational hand controller we assured ourselves that the engine did respond by swivelling or gimballing. This is, of course, is important for maneuvers in space. The countdown is still proceeding very satisfactorily other than two minor problems since we picked up the count at 11pm Eastern Daylight Time last night, all has gone well. As we approach the one hour mark now, in the count of series of radio frequency and telemetry checks will be in progress with the launch vehicle. We'll also check out the tracking beacons in the Instrument Unit that travels as a guidance system for the Saturn V during the powered phase of flight. Now 59 minutes, 48 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 841 kB.]PAO: This is Apollo Saturn Launch Control. We've just passed the 56-minute mark in our countdown. We're still proceeding in an excellent manner at this time. All elements reporting in, that all systems continuing to look good at this point. We are still aiming toward our planned lift-off at the start of the lunar window, 9:32am Eastern Daylight. A short while ago, in fact the Spacecraft Test Conductor Skip [Chauvin... break in recordings and transcript] ...we were doing quite well, in fact some 15 minutes ahead on some aspects of the preparation spacecraft-wise. Armstrong replied that was fine so long as we don't launch 15 minutes early, obviously referring to the start of the window. The countdown, still going well. T minus 55 minutes, 10 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 1,853 kB.]PAO: This is Apollo Saturn Launch Control. We've passed the 51-minute mark in our countdown. We're now T minus 50 minutes, 51 seconds and counting. Apollo 11 countdown is still Go at this time. All elements reporting ready at this point in the countdown. The spacecraft - correction - the Test Supervisor Bill Schick has advised all hands here in the control center, and the spacecraft checkout people, that in about 30 seconds that big swing arm that has been attached to the spacecraft up to now will be moved back to a parked position some 5 feet away from the spacecraft. We alert the astronauts because there is a little jolt when the swing arm is moved away. It will remain in that position, some 5 feet away from the spacecraft, until the 5-minute mark in the count when it's completely pulled away to its retracted position. It's coming up now, in 5 seconds, the swing arm will come back. Mark. The swing arm now coming back from the spacecraft. The countdown proceeding satisfactorily. We've completed our telemetry checks with the launch vehicle and, at this point, with the swing arm back, we arm the pyrotechnics so that escape tower atop the astronauts, atop their spacecraft, could be used if a catastrophic condition was going to occur under them with the launch vehicle from this point on down in the countdown. We have the high speed elevator located at the 320-foot level in the event the astronauts have to get out in a hurry. This is a special precaution. One of the members of the support team for Apollo 11, Astronaut Bill Pogue, is here in the firing room. He acts as the Capsule Communicator during the countdown. His call sign is Stoney. He controls that elevator. He now has it locked at the 320-foot level. These are special precautions for safety purposes during the final phase of the count. Now coming up on the 49 minute in the countdown, this is Kennedy Launch Control.
[MP3 audio file. 1,607 kB.]PAO: This is Apollo Saturn Launch Control. We've passed the 46-minute mark in our countdown. T minus 45 minutes, 52 seconds and counting. All elements still Go in the countdown at this time. The hard worker in the spacecraft at this point in the countdown, Astronaut Buzz Aldrin in the middle seat. He's been working with the Spacecraft Test Conductor on setting up proper switch settings in preparation for pressurizing their Reaction Control System. These are these big thrusters on the side of the Service Module. There's actually 16 of them in 4 quadrants around the Service Module. They are used for maneuvers in space. We pressurize that system before lift-off. That particular operation will be coming up in some 5 minutes or so. In preparation for it, Buzz Aldrin, who has most of the switches in front of him, has been preparing for that particular event. The launch vehicle people keeping an eye on the status of the various propellants aboard the Saturn V launch vehicle. Just at lift-off, we will have a vehicle weighing close to 6 and a half million pounds on the launch pad. There's more than a million gallons of propellants aboard the three stages of the Saturn V. The reports here in the control center are the propellants are stable. We did take a look a little while ago at the RP-1, the high-grade kerosene fuel that's used in the first stage of the Saturn V, to make sure it was at its proper level. We keep an eye on these various aspects throughout the count, and use the aid of computers to keep an overall look on general status. So now at T minus 44 minutes, 21 seconds and counting; this is Kennedy Launch Control.
[The lowest of the Saturn's main tanks was filled with 810,000 litres of RP-1 three weeks earlier. RP stands for 'rocket propellant' which in this case has been highly refined to ensure consistent and predictable combustion properties. The level in the tank was checked again at T-13 hours and again at T-1 hour.]PAO: This is Apollo Saturn Launch Control. We've passed the 41-minute mark in our count. T minus 40 minutes, 53 seconds and counting. We are continuing, and we're continuing very excellently at this time. There are no problems that have been reported in as the countdown continues to click down. We are still aiming for the start of our window on this, the first flight to land men on the Moon. Our - we're aiming toward our planned lift-off time of 9:32 am Eastern Daylight Time. Coming up shortly will be a key test here in the firing room, as far as the launch vehicle people are concerned. It's a - some final checks of the destruct system aboard the three stages of the Saturn V launch vehicle. In the event, during powered flight, that the vehicle strayed rather violently off course, the Range Safety Officer could take action to destroy the vehicle which obviously would occur after the astronauts were separated by their escape tower from the faulty vehicle. We make a check of the destruct system to assure that if a signal is required to get through, that, in fact, it will. This is what is coming up here in the control center at this time. All aspects of the mission still Go. We're at T minus 39 minutes, 47 seconds and counting. This is Kennedy Launch Control.[All three stages use liquid oxygen as the oxidiser component in the burning process. It has been rendered liquid by being cooled to about -183°C, thereby allowing large quantities to be carried in large insulated tanks, At nine hours before launch, nitrogen gas is pumped through them to purge out air and water vapour contaminants. Six and a half hours before launch, the tanks are precooled to prepare them for the loading of LOX. The S-IC requires 1.3 million litres, that for the S-II takes 331,000 litres and the S-IVB's LOX tank requires 92,350 litres.]
[Filling these tanks with such cold contents requires a little finesse. Initially, the LOX is fed at a slow rate which furiously boils as it contacts the relatively warm tank structure. The vapourisation of the LOX takes heat away until a pool of liquid begins to form. When enough liquid has collected, filling steps up to a fast rate until the tanks are nearly full and the slow rate is reestablished to top them off. From then on, until three minutes before launch, the level is replenished as the volatile LOX continues to boil off from heat leaking into the tank.]
[The fuel for the S-II and S-IVB stages is liquid hydrogen (LH2). Like LOX, it must be cooled to render it liquid, this time to -253°C which is only 20K above absolute zero. Conditioning the LH2 tanks is more involved because only helium gas will not freeze in the presence of liquid hydrogen. Once clear of contaminants, the tanks are cooled to accept the propellants by first passing cold helium gas through the system then feeding propellant at a slow rate and allowing it to boil off, taking heat with it in a process similar to that for the LOX tanks. After filling at a fast rate, and to compensate for loss due to boil-off, both tanks are replenished until about three minutes before launch when the tanks are pressurised. Up to the launch, pressurising helium gas is supplied from the ground. After launch, the boil-off of the propellants is enough to maintain pressure. For the S-IVB, additional pressurising gas comes from a set of helium spheres mounted on the stage.]
[MP3 audio file. 1,256 kB.]PAO: This is Apollo Saturn Launch Control. We've passed the 36-minute mark in our countdown; T minus 35 minutes, 48 seconds and counting. We've completed those range safety command checks. All still going well with the countdown. A short while ago Spacecraft Test Conductor Skip Chauvin asked Neil Armstrong if the crew was comfortable up there, and Neil reported back. He said its - "We're very comfortable - it's very nice this morning." For a status report, we'll now switch to Mission Control, Houston.
[Range safety is concerned with ensuring that if the rocket were to go wayward, it would do so without threatening injury or death to those on the ground. The Saturn's propellant tanks have shaped explosive charges attached. In the event the launch vehicle cannot be controlled, these would be detonated to open the tanks and ensure their contents are dispersed while at altitude. The charges for the fuel tanks are placed on the opposite side of the vehicle from those for the oxidiser tanks so as to minimise the degree to which the propellants would mix as they are dispersing.]PAO: This is Apollo Mission Control. Flight Director Cliff Charlesworth's team is on station here in the Mission Operations Control Room, ready to assume the control of this flight at tower clearance. There is a possibility that Apollo 11 will check out the Command Module color TV camera during the first Earth revolution while in contact with the Goldstone station. If this checkout does occur, we acquire Goldstone at 1 hour, 29 minutes elapsed time. We have loss of signal at 1 hour, 33 minutes, 50 seconds elapsed time. This TV camera checkout is a possibility. This is Mission Control, Houston.[The next announcement comes from the PAO at Mission Control in Houston, rather than the Launch Control Center at Cape Kennedy, Florida.]
[The commentary now resumes with the PAO at Launch Control, Florida.]PAO: This is Apollo Saturn Launch Control. We've just passed the 31-minute mark in our count. At T minus 30 minutes, 52 seconds and counting; aiming toward our planned lift-off time of 32 minutes past the hour, the start of our launch window on this, the mission to land men on the Moon. The countdown still proceeding very satisfactorily at this time. We've just got by an important test with the launch vehicle checking out the various batteries in the three stages and Instrument Unit of the Saturn V. We remain on external power through most of the count to preserve those batteries which must be used during the powered flight. We've just taken a look at them by going internal and then switching back to external again. The batteries all look good. The next time we go internal will be at the 50-second mark with those batteries and they will remain, of course, on internal power during the flight. The Lunar Module, which has been rather inactive during these latter phases of the count also is going on internal power at this time on the 2 batteries on the ascent stage and the 4 batteries of the descent stage. For the next 20 minutes we'll take a look at some systems in the Lunar Module, then power down at about the 10-minute mark in the count, power down the telemetry to preserve the power of the LM. The Lunar Module on Apollo 11, of course, when it separates from the Command Module in lunar orbit, will have the call sign Eagle. The Command Module call sign, once the two vehicles separate, will be Columbia. Both Columbia and Eagle are Go at this time. At 29 minutes, 24 seconds and counting; this is Kennedy Launch Control.
[At the very top of the launch vehicle, between the S-IVB and the spacecraft, is a 1-metre-tall ring called the IU (Instrument Unit). The ring's diameter matches the rocket stage below it. It carries systems concerned with the guidance and control of the vehicle. These include a digital computer and an inertially stabilised platform. With help from a theodolite located directly south of the vehicle, the platform is orientated to be aligned with the bearing the rocket is to take, 72° or ENE. This orientation will be maintained until just a few seconds before launch so that the turning of Earth does not take it out of alignment.]PAO: This is Apollo Saturn Launch Control. We've just passed the 26-minute mark in the count; T minus 25 minutes, 53 seconds and counting; still proceeding very satisfactorily. At this time Spacecraft Test Conductor Skip Chauvin working with astronaut Buzz Aldrin in the middle seat covering the final pressurization of the Reaction Control System for the spacecraft. These are those big thrusters on the side of the Service Module that are used for maneuvers in space. Each one of these thrusters is capable of 100 pounds of thrust [445 Newtons]; there are 16 of them located in 4 quadrants around the Service Module. We pressurize the system with helium prior to launch to make sure that all will be in readiness for use in space.
PAO: The countdown still proceeding satisfactorily. It picked up at the T minus 9-hour mark at 11:00 pm Eastern Daylight Time last evening. We've just had two comparatively minor problems since that time. The major portion of the countdown during the early morning hour; some five hours of work was taken to load the various propellants aboard the stages of the Saturn V launch vehicle. As we came into the count this morning, we did already have the fuel aboard the first stage, but it was necessary to bring the liquid oxygen aboard all three stages and the liquid hydrogen fuel aboard the second and third stages. Close to three-quarters of a million gallons of propellants were loaded during these 5 hours. Following that, the astronauts, the prime crew, were awakened at 4:15 am Eastern Daylight as planned in their countdown, and proceeded to have a physical examination in which they were declared flight-ready. They sat down for the normal astronaut fare on launch day, as far as breakfast is concerned; orange juice, steaks, scrambled eggs, toast and coffee. The three pilots were joined by two of their colleagues at breakfast, Director of Flight Crew Operations Deke Slayton, and the backup Command Module Pilot Bill Anders, who has been named the Executive Secretary of the National Aeronautics and Space Council. The astronauts departed from their crew quarters - After checking out their suits, they departed from the crew quarters at 6:27 am and some 27 minutes later, 8 miles away from the crew quarters at the Kennedy Space Center atop the launch pad at complex 39, 6:54 am, the commander, astronaut Neil Armstrong, was the first to board the spacecraft. He was followed about 5 minutes later by Mike Collins, and finally Buzz Aldrin, the man who is sitting in the middle seat during lift-off, was the third astronaut to come aboard.
PAO: Two minor problems have been encountered during the count. Early in the count, a malfunction light came on here in the control center indicating that we might have a communication problem at the launch pad. Nothing to do with the spacecraft, but it indicated we possibly might not be able to talk to some key technicians we had at the pad. The problem turned out to be very minor; a simple adjustment of some equipment beneath the pad remedied the problem. There was no, in fact, no equipment problem involved. The second problem, we did encounter a leaky valve in part of the equipment that's used to replenish the hydrogen fuel supply on the third stage of the Saturn V launch vehicle. A team of technicians were sent out to the launch pad at about the time the astronauts were traveling to the pad. They tightened some bolts and we were able to bypass this valve and proceed with our countdown. The weather is certainly Go. It's a beautiful morning for a launch to the Moon. We expect a temperature of about 85 degrees in the Kennedy Space Center area. The wind's about 10 miles - 10 knots, rather, from the southeast, and the weather conditions in the round-the-world track, according to reports from the Manned Space Flight Meteorology Group, indicate all weather conditions are acceptable for launch. That's our general status. We've just passed the 22-minute mark in the count. 21 minutes, 55 seconds and counting; this is Kennedy Launch Control.
[MP3 audio file. 1,471 kB.]PAO: This is Apollo Saturn Launch Control. We're now less than 16 minutes away from the planned lift-off of the Apollo 11 space vehicle. All still going well with the countdown at this time. The astronauts aboard the spacecraft have had a little chance to rest over the last few minutes or so. At least they haven't been busy with procedures with the Spacecraft Test Conductor. In the meantime we have been performing final checks on the tracking beacons in the Instrument Unit which is used as the guidance system during the powered phase of flight. Once we get down to the 3-minute-and-10-second mark in the countdown, we'll go on an automatic sequence. As far as the launch vehicle is concerned, all aspects from there on down will be automatic, run by the ground master computer here in the firing room. This will lead up to the 8.9-minute [means 'second'] mark in the countdown when the ignition sequence will begin in those five engines of the first stage, the S-IC stage of the Saturn V. At the 2-second mark we'll get information and a signal that all engines are running, and at the zero mark in the countdown, once we get the commit signal, the signal that says that the thrust is proper and acceptable, we then will get a commit and lift-off as the hold-down arms release the vehicle. We have some 7.6 million pounds of thrust pushing the vehicle upward, a vehicle that weighs close to 6½ million pounds. We're now at 14 minutes, 30 seconds and counting, and this is Kennedy Launch Control.
[MP3 audio file. 1,098 kB.]PAO: This is Apollo Saturn Launch Control. We've passed the 11-minute mark. Now T minus 10 minutes, 54 seconds on our countdown for Apollo 11. All still Go at this time. The astronauts in the spacecraft busy again. The Commander Neil Armstrong has performed some final switch settings for the Stabilization and Control System of the spacecraft. The spacecraft also now is on full internal power. This came shortly after the 15-minute mark. Spacecraft now on the full power of its fuel cells. Up to this time, it had been sharing the load with an external power source. Both Armstrong and Buzz Aldrin have armed their rotational hand controllers - the controllers they use in flight - and we have now gone to automatic system with the Emergency Detection System. That system - it would cue the astronauts if there's trouble down below with the Saturn V rocket during the powered flight. We're now coming up on the 10-minute mark. Ten minutes away from our planned lift-off. Mark T minus 10 minutes and counting, T minus 10. We're aiming for our planned lift-off at 32 minutes past the hour. This is Kennedy Launch Control.
[MP3 audio file. 1,544 kB.]PAO: This is Apollo Saturn Launch Control. We've passed the 6 minute mark in our countdown for Apollo 11. Now 5 minutes, 52 seconds and counting. We're on time at the present time for our planned lift-off of 32 minutes past the hour. Spacecraft Test Conductor, Skip Chauvin, now has completed the status check of his personnel in the control room. All report they are Go for the mission, and this has been reported to the Test Supervisor, Bill Schick. The test supervisor now going through some status checks. Launch Operations Manager Paul Donnelly reports Go for launch. Launch Director Rocco Petrone now gives a Go. We're 5 minutes, 20 seconds and counting. Coming up shortly, that swing arm up at the spacecraft level will come back to its fully retracted position. This should occur at the 5-minute mark in the count. In the meantime the Lunar Module telemetry has been powered down. We took a good look at Eagle, and it looks good. The Spacecraft Test Conductor for the Lunar Module reported that Eagle was Go. The swing arm now coming back to its fully retracted position as our countdown continues. T minus 4 minutes, 50 seconds and counting. Skip Chauvin informing the astronauts that the swing arm now coming back. The astronauts will have a few more reports coming up in the countdown. The last business report will be from Neil Armstrong at the 45-second mark in the count when he gives the status on the final alignment of the Stabilization and Control System. We're now passing the 4 minute, 30 second mark in the countdown - still Go at this time.
[MP3 audio file. 2,539 kB.]PAO: Four minutes, 15 seconds - the Test Supervisor now has informed Launch Vehicle Test Conductor Norm Carlson, you are Go for launch. From this time down, Carlson handles the countdown as the launch vehicle begins to build up. We're now hitting the 4-minute mark. Four minutes and counting. We are Go for Apollo 11. We'll go on an automatic sequence as standing at 3 minutes and 7 seconds.
PAO: Three minutes, 45 seconds and counting. In the final abort checks between several key members of the crew here in the control center and the astronauts, Launch Operations Manager Paul Donnelly wished the crew, on the launch teams' behalf, "Good luck and Godspeed."
PAO: Three minutes, 25 seconds and counting; we're still Go at this time. We'll be coming up on the automatic sequence about 10 or 15 seconds from this time. All still Go at this time. Neil Armstrong reported back when he received the good wishes: "Thank you very much. We know it will be a good flight." Firing command coming in now. We are on the automatic sequence. We're approaching the 3 minute mark in the count. T minus 3 minutes and counting. T minus 3 - we are Go with all elements of the mission at this time. We're on an automatic sequence as the master computer supervises hundreds of events occurring over these last few minutes.
PAO: T minus 2 minutes, 45 seconds and counting. The members of the launch team here in the control center monitoring a number of what we call red-line values. These are tolerances we don't want to go above and below in temperatures and pressures. They're standing by to call out any deviations from our plans. Two minutes, 30 seconds and counting; we're still Go on Apollo 11 at this time. The vehicle starting to pressurize as far as the propellant tanks are concerned, and all is still Go as we monitor our status board. Two minutes, 10 seconds and counting. The target for the Apollo 11 astronauts, the Moon, at lift-off, will be at a distance of 218,096 miles away. We just passed the 2-minute mark in the countdown. T minus 1 minute, 54 seconds and counting. Our status board indicates that the oxidizer tanks in the second and third stages now have pressurized. We continue to build up pressure in all three stages here at the last minute to prepare it for lift-off.
[MP3 audio file. 1,861 kB.]PAO: T minus 1 minute, 35 seconds on the Apollo mission, the flight to land the first men on the Moon. All indications coming in to the control center at this time indicate we are Go. One minute, 25 seconds and counting. Our status board indicates the third stage completely pressurized. Eighty-second mark has now been passed. We'll go on full internal power at the 50-second mark in the countdown. Guidance system goes on internal at 17 seconds leading up to the ignition sequence at 8.9 seconds. We're approaching the 60-second mark on the Apollo 11 mission.
PAO: T minus 60 seconds and counting. We have passed T minus 60. 55 seconds and counting. Neil Armstrong just reported back: "It's been a real smooth countdown". We've passed the 50-second mark. Power transfer is complete - we're on internal power with the launch vehicle at this time. 40 seconds away from the Apollo 11 lift-off. All the second stage tanks now pressurized. 35 seconds and counting. We are still Go with Apollo 11. 30 seconds and counting. Astronauts report, "It feels good". T minus 25 seconds.
PAO: Twenty seconds and counting. T minus 15 seconds, guidance is internal. Twelve, 11, 10, 9, ignition sequence starts...
[The F-1 engine has a complex ignition sequence which will be described here. First, a description of the engine.]PAO: ...6, 5, 4...
[ A large combustion chamber and bell have an injector plate at the top, through which RP-1 fuel and 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 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. After powering the turbine, the exhaust gases pass through 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. Above the turbine, on the same 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, though before launch, RJ-1 ramjet fuel is supplied from the ground for this purpose. 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. This cools the chamber and bell structure while also pre-warming the fuel. Lastly, an igniter, containing a cartridge of hypergolic fluid with burst diaphragms at either end, is in the high pressure fuel circuit and has its own inject point in the combustion chamber. This fluid is triethylboron with 10-15% triethylaluminium.]
[At T minus 8.9 seconds, a signal from the automatic sequencer fires four pyrotechnic devices. Two of them cause the fuel-rich turbine exhaust gas to ignite when it enters the engine bell. Another begins combustion within the gas generator while the fourth ignites the exhaust from the turbine. Links are burned away by these igniters to generate an electrical signal to move the start solenoid. The start solenoid directs hydraulic pressure 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. 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 a 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 port where it spontaneously ignites on contact with the LOX already in the chamber.]
[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. 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.]PAO: ...3...
[This diagram shows how the thrust rose during the start-up of each engine. It takes two seconds for full performance to be attained on all engines once the first has begun increasing. The engines are started in a staggered 1-2-2 sequence so that the rocket's structure would be spared a single large load increase, with the centre engine being the first to start. The outboard engines exhibit a hiccup in their build-up due to the ingestion of helium from the pogo suppression system installed in each one. The centre engine does not have this installed.]PAO: ...2, 1, zero, all engine running, LIFT-OFF![As the flow of fuel and LOX rises to maximum, the chamber pressure, and therefore thrust, is monitored to confirm that the required force has been achieved. With the turbopump 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.]
[Public Affairs Officer Jack King, whose coolness is legendary, finally succumbs to the tension and is clearly heard to say "all engine running" instead of "all engines running".]PAO: We have a lift-off, 32 minutes past the hour. Lift-off on Apollo 11.
[MP3 audio file. 2,899 kB.]000:00:04 Armstrong: Roger. Clock.[MP3 audio file (11,435 kB) of the entire air/ground audio during ascent to orbit, but without the PAO's commentary.]
PAO: Tower cleared.
[As planned, control of the flight now passes from the Launch Control Center at Cape Kennedy, Florida to the Mission Control Center in Houston, Texas. There, communication with the crew is handled by an astronaut sitting at the CapCom console; in this case, Bruce McCandless. The PAO also switches, and Jack King relinquishes the commentary to the Houston PAO, whose voice is heard from now on.]000:00:13 Armstrong: Roger. We got a roll program.
000:00:15 McCandless: Roger. Roll. [Long pause.]
PAO: Neil Armstrong reporting their roll and pitch program which puts Apollo 11 on a proper heading. Plus 30 seconds.
[When it sat on the launch pad, the space vehicle's coordinate system matched the cardinal points of Earth's geograpic system. Its X-axis pointed straight up and its Y-axis pointed to true north. The third component of this system, the Z-axis, therefore was pointed directly west. Before it begins to tilt over, the vehicle needs to roll 18° so that the minus X-axis, previously facing east, faces along the planned heading, in this case 72° east of north. Then the tilt motion will be a simple pitch motion around the Y-axis.]000:00:34 Armstrong: Roll's complete and the pitch is programming. [Pause.][Prior to the roll maneuver, the vehicle executed a small yaw maneuver to deliberately lean away from the launch tower during its first few seconds of ascent.]
[20.6 seconds after launch, the Saturn's guidance system aims the four outboard engines slightly away from the centreline of the vehicle. This is in case an outboard engine fails whereupon the resultant off-centre thrust vector would be nearer to acting through the centre-of-mass of the rocket.]
000:00:44 Armstrong: One Bravo. [Long pause.]
PAO: One Bravo is a abort control mode.
[Like the Space Shuttle that came after it, the flight of a Saturn V had defined times during which, the means by which the crew could escape from a failing vehicle were defined. Unlike the Shuttle with its solid rocket boosters which gave no escape option, the Saturn had so-called 'abort modes' throughout its ascent.]PAO: Altitude's 2 miles.[For the first two of these, one-alpha and one-bravo, rotation rates exceeding ±4° per second in pitch and yaw, ±20° per second in roll would will entail an abort.] [The first 42 seconds were flown in mode one-alpha. If things went wrong, the Launch Escape Tower (LET) would lift the Command Module away from the booster. The problem is that the CM needs to be taken away out to sea and the vehicle has not yet imparted much horizontal velocity. Therefore, a small 'pitch control' motor would additionally fire to send the CM away from the vicinity of the impending conflagration. The CM then goes through an automatic sequence to carry out a safe landing on Earth.]
[Mode one-bravo is similar except the pitch control motor is dispensed with since the vehicle would have tilted over enough to aim a CM out to sea. Instead, during an abort, a pair of canards at the tip of the LET would deploy to force the CM-tower combination to adopt a CM-first attitude. This was because hypersonic testing had shown that the stack had a stable tower-frst attitude. This mode extends to about 35.5 km altitude.]
000:01:02 McCandless: Apollo 11, Houston. You're good at 1 minute.
000:01:06 Armstrong: Roger. [Long pause.]
PAO: Down range 1 mile, altitude 3, 4 miles now. Velocity 2,195 feet per second.
PAO: We're through the region of maximum dynamic pressure now.
[As it flies through the air, the rocket must withstand an aerodynamic pressure imparted by its speed through the molecules of the atmosphere. This is like the pressure felt on a hand stuck out of the window of a fast-travelling car. In the rocketry situation, two things are happening to vary this pressure: the vehicle's rising speed makes it higher; the rapidly thinning atmosphere brings it down. The interaction of these two variables leads to a point in the ascent when the aerodynamic pressure, denoted by the letter 'Q', reaches a peak. This is known as Max-Q and is the point when weaknesses in the rocket's structure are most likely to be found out. It occurs at 1 minute and 23 seconds into the flight.]PAO: Eight miles down range, 12 miles high, velocity 4,000 feet per second.
000:01:54 McCandless: Stand by for Mode One Charlie.
000:01:58 McCandless: Mode One Charlie.
000:01:59 Armstrong: One Charlie.
PAO: Cliff Charlesworth taking a staging status.
[Mode one-charlie begins at an altitude of about 30.5 km. At this altitude and beyond, the air is too thin for the LET canards to be effective so control of the CM's attitude during an abort would initially go to the its maneuvering thrusters. The safe range for vehicle rotation changes to be ±9° per second in pitch and yaw, ±20° per second in roll.]000:02:03 McCandless: Apollo 11, this is Houston. You are Go for staging. [Pause.]
000:02:17 Armstrong: Inboard cut-off.
PAO: Inboard engines out.
000:02:19 McCandless: We confirm inboard cut-off. [Long pause.]
[The central or inboard engine of the Saturn V is shut down early to limit the vehicle's rapidly rising acceleration. There are two reasons for this rise. The first is that the mass of the vehicle as a whole is dropping by over 13 tonnes every second. As a result, the engines have a decreasing mass to push against. A lesser factor is the rising efficiency of the engines as they rise out of sea-level air pressure into the near vacuum of the upper atmosphere. At sea-level, the atmosphere acts as an inefficient cap on an engine's nozzle. In a vacuum, the exhaust gases can exit without hindrance. The result on the F-1 is a 20% rise in efficiency.]PAO: Down range 35 miles, 30 miles high. Standing by for the outboard engine cut-down [means "shutdown"] now.
[This graph is redrawn from the AS-506 Flight Evaluation Report. It shows how teh acceleration experienced by the crew varies over the course of the Saturn's ascent. The key events in the graph are:
[The 4g experienced at the end of the S-IC burn is the highest that will be reached during ascent. The only time a greater g-force will be experienced during the mission is upon re-entry at the end when over 6g will be imparted on the crew.]
- Lift-off under S-IC power. Note how the acceleration rises rapidly as the propellant tanks empty and the engines increase in efficiency.
- Cut-off of the central or inboard engine engine of the S-IC.
- Cut-off of the remaining four outboard engines of the S-IC at a peak of 4g.
- S-II stage ignition. Note the reduced angle of the graph. Although the mass of the first stage has been discarded, the thrust of the S-II stage is one ninth of the final S-IC thrust.
- Cut-off of the inboard engine of the S-II at a peak of approximately 1.8g.
- Change in mixture ratio caused by the operation of the PU valve. The richer mixture reduces the thrust slightly but also increases engine efficiency.
- Outboard engine cut-off of the S-II at approximately 1.7g.
- S-IVB stage ignition. Note again the reduced angle of the graph caused by the thrust being cut by a fifth.
- With the cut-off of the S-IVB's first burn, the vehicle is in orbit and the acceleration drops to zero.
[The Saturn's guidance computer then performs 'tilt arrest'. Throughout the S-IC burn (and for the start of the S-II), the vehicle has been flying a series of pre-programmed maneuvers called the tilt sequence. The yaw at launch and the roll to align the rocket with the launch azimuth were two of these. The major maneuver of the tilt sequence has been a slow tilt towards horizontal as the vehicle climbs. Note that this form of guidance is not trying to aim for a particular point. It takes no account of where it is or how the winds are affecting it and so it described as open-loop guidance. At the end of the S-IC burn, it is no longer desirable to have the vehicle rotating whioe staging takes place so the tilt maneuver is stopped or arrested.]
000:02:44 Armstrong: Staging.
[The sequence for separation is as follows: Half a second after shutdown of the first stage, four ullage motors mounted around the interstage ignite, followed a fifth of a second later by a command to fire the first separation explosive and ignition of the eight retro rockets mounted in the conical fairings near the base of the S-IC. The two sets of rockets fire in opposite directions to pull the two sections of the vehicle apart. Physical separation comes soon after and half a second later, the J-2 engines on the S-II stage are started. The S-II ullage rockets were eventually deleted from the later Saturn V's. Ullage is a brewer's term for the space in a barrel taken up by air rather than liquor. The rocket people modify its use to mean the establishment of that space at the opposite end of a tank from the outlet so that the liquid leaves the tank cleanly without gas and with a degree of pressure to help it flow to the engine. They usually achieve this by firing small rockets to settle the tank's contents to one end.]
[The thrust chamber and bell of each engine is fabricated from stainless steel tubes brazed together in a single unit. Supercold LH2 is pumped through these tubes to cool the thrust chamber and simultaneously prewarm the fuel. The engine carries two separate turbopumps, both powered in turn by the exhaust from a gas generator which burns the stage's main propellants. 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 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 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 percent seeps through the injector face to cool it, the rest passing through the annular orifices.]
[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 propellant through the supply system well before ignition to chill all components to their operating temperatures otherwise gas would be formed which would interfere with the engine's use of propellant as a lubricant in the turbopump bearings. A tank of gaseous helium is fabricated within a larger tank of gaseous hydrogen. This is the Start Tank. The helium provides control pressure for the engine's valves while the 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 during flight to optimise engine performance.]
[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. 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.]
[As the thrust of each second stage engine reaches 65%, it causes its indicator light on the Main Display Console to be extinguished.]
000:02:59 Armstrong: Ah, Roger. You're loud and clear, Houston. [Pause.]
PAO: At 3 minutes, downrange 70 miles, 43 miles high, velocity 9,300 feet per second.
000:03:13 Armstrong: We got skirt sep.
000:03:15 McCandless: Roger. We confirm skirt sep.
[During the test flights of the Saturn V, NASA mounted film cameras at strategic places around the vehicle to allow engineers to see the dual plane separation at work. The following film clip, kindly donated by www.footagevault.com, is from the flight of Apollo 4. Two cameras were mounted on either side of the S-II stage looking past its J-2 engines toward the departing S-IC.
000:03:19 McCandless: Roger, tower. [Pause.]
PAO: Neil Armstrong confirming both the engine skirt separation and the launch escape tower separation.
000:03:28 Collins: Houston, be advised the visual is Go today.
000:03:32 McCandless: This is Houston. Roger. Out.
000:03:36 Collins: Yeah, they finally gave me a window to look out. [Pause.]
[With the loss of the escape tower, the flight moves to abort mode two. Now if the vehicle goes awry, the CSM would separate from the Saturn and either the Service Module's main engine or its small thrusters would be used to gain distance before the CM continues to a normal landing in the sea.]
[Six seconds after the jettison of the escape tower, the guidance mode of the Saturn changes from dumb to smart, from open loop to closed loop. This is the Iterative Guidance Mode (IGM) whereby the guidance system is now actively plotting a course to the point in space and velocity where it will insert the vehicle into orbit. While the Saturn was in the thicker parts of the atmosphere, it was undesirable to allow it to make large attitude changes, hence the pre-programmed tilt sequence. Now that the vehicle is essentially in a vacuum, the computer can react to its actual position and velocity and issue steering commands to the engines as required to reach its goal.]
000:03:52 Armstrong: Roger. [Pause.]
PAO: Downrange 140 miles, altitude 62 miles, velocity 10,300 feet per second.
000:04:01 McCandless: 11, Houston. You are Go at 4 minutes.
000:04:04 Armstrong: Roger. [Long pause.]
PAO: Apollo 11 right on the ground track.
PAO: 190 miles down range now, 72 miles high, velocity 11,000 feet per second.
PAO: Booster says it's looking good at 5 minutes.
000:05:03 McCandless: 11, Houston. You are Go at 5 minutes.
000:05:06 Armstrong: Roger. It'll - Apollo 11. Go. [Pause.]
PAO: Down range 270 miles, altitude 82 miles, velocity 12,472 feet per second.
000:05:21 McCandless: Stand by for S-IVB to COI capability.
000:05:27 McCandless: Mark. S-IVB to COI capability.
000:05:30 Armstrong: Roger.
PAO: Apollo 11 could now get into orbit using the S-IVB if necessary.
000:05:35 Armstrong: You sure sound clear down there, Bruce. Sounds like you're sitting in your living room.
000:05:39 McCandless: Ah, thank you. You all are coming through beautifully, too. [Long pause.]
PAO: Everyone is reporting Go here in the Control Center.
000:06:00 Armstrong: We're Go at 6 minutes. Starting the gimbal motors.
000:06:20 McCandless: Apollo 11, this is Houston. Level sense arm at 8 plus 17; outboard cut-off at 9 plus 11. [Long pause.]
PAO: Level sense arm is the sequence that arranges the staging between the second stage and the third stage. The fuel uncovers a sensor starting that sequence. Predicting that will be uncovered at 8 minutes, 17 seconds with outboard engine cut-off 9 minutes, 11 seconds on the second stage.
000:07:01 Armstrong: Apollo 11's Go at 7 minutes.
000:07:04 McCandless: 11, this is Houston. Roger. You're Go from the ground at 7 minutes. Level sense arm at 8 plus 17; outboard cut-off at 9 plus 11.
000:07:09 Armstrong: Roger. [Long pause.]
PAO: Downrange 530 miles, altitude 95 miles, velocity 17,358 feet per second.
PAO: Apollo 11 is still right down the ground track. Still Go at 7 minutes, 41 seconds.
000:07:42 Armstrong: Inboard cut-off.
000:07:45 McCandless: Roger. We confirmed. [Long pause.]
PAO: Inboard engines are out, on the second stage as planned.
000:08:19 McCandless: Apollo 11, Houston. You are Go at 8 minutes.
000:08:22 Armstrong: Ah, just got the mixture ratio shift.
000:08:24 McCandless: Roger. We got PU shift down here, too. [Pause.]
[On the S-II, the strategy was for most of the burn to be made at a high MR of 1:5.5 which also yielded the stage's maximum thrust. Once a specific velocity had been reached, which occurred 5 minutes, 31.8 seconds after the engines were commanded to start, the MR for the remaining four engines was reduced to 1:4.34 for the rest of the burn. The effect of this was two-fold: it reduced the thrust from the stage by a quarter but it also increased the specific impulse and therefore the efficiency of the engines. If engineers had the timing of the MR change right, the intention was that the LH2 and LOX should both be as close as possible to depletion when sensors in the tanks indicated it would be prudent to shut down the stage.]
[On the very early Saturn V flights (Apollos 4, 6 and 9), the timing was based on a closed-loop decision. Level gauges within the tank monitored how the propellants were being consumed and the change made based on that data. Mathematical modelling had shown benefits to an open-loop decision, one based on the change in MR occurring when a specific velocity had been reached.]
000:08:52 McCandless: 11, this is Houston. You are Go for staging. Over.
000:08:56 Armstrong: Understand, Go for staging. And...
000:08:57 McCandless: Stand by for Mode IV capability.
000:08:59 Armstrong: Okay. Mode IV.
000:09:01 McCandless: Mode IV capability. [Long pause.]
PAO: Mode IV on Apollo 11 could get into orbit using the Service Propulsion System now. Altitude is 100 miles, downrange is 883 miles. Outboard engine cutoff.
000:09:15 Armstrong: Staging, and ignition.
000:09:19 McCandless: Ignition confirmed. Thrust is Go, 11. [Long pause.]
PAO: And we have a good third stage now.
[Although no close-up film exists of an S-IVB staging from an S-II, the following clip, kindly donated by www.footagevault.com, is often-used in documentaries, where it is often incorrectly used to portray the burn for the Moon.
000:10:01 McCandless: Apollo 11, this is Houston. At 10 minutes, you are Go.
000:10:06 Armstrong: Ah, roger. 11's Go. [Long pause.]
PAO: Capcom Bruce McCandless giving the reports here from the Control Center.
000:10:24 McCandless: Apollo 11, this is Houston. Predicted cut-off at 11 plus 42. Over.
000:10:29 Armstrong: 11:42. Rog. [Long pause.]
PAO: Downrange 1,175 miles, velocity 24,190 mile - feet per second, altitude 102 nautical miles.
PAO: Apollo 11 still Go on all sources.
000:11:03 McCandless: Apollo 11, this is Houston. You are Go at 11.
000:11:08 Armstrong: That's a Go. [Long pause.]
PAO: We're predicting third stage shutdown at 11 minutes, 42 seconds. Velocity 25,254 feet per second. Downrange 1,400 miles now. Altitude 102.8 nautical miles.
000:11:42 Armstrong: Shutdown.
PAO: Shutdown right on time.
000:11:45 Collins: SECO. We are showing 101.4 by 103.6.
000:11:51 McCandless: Roger. Shutdown. We copy 101.4 by 103.6.
000:12:06 McCandless: Apollo 11, this is Houston. You are confirmed Go for orbit.
000:12:12 Armstrong: Roger. [Long pause.]
PAO: We show insert...
000:12:24 McCandless: Apollo 11, this is Houston. The booster is safe.
000:12:29 Armstrong: Ah, roger. [Long pause.]
PAO: We show velocity at insertion, 25,568 feet per second.
000:13:27 McCandless: Apollo 11, this is Houston. The booster has been configured for orbital coast. Both spacecraft are looking good. Over.
000:13:35 Armstrong: Roger. [Long pause.]
000:14:33 McCandless: Apollo 11, this is Houston. Vanguard LOS at 15:35. AOS Canaries at 16:30. Over.
000:14:43 Armstrong: Okay. Thank you.
[The S-IC first stage has shut down and separated from the S-II second stage.]
000:02:46 Armstrong: And ignition. [Pause.]
[The S-II stage carries five J-2 uprated engines which burn LH2 and LOX to produce a total of 5,141 kN (1,155,859 pounds) thrust. The engine design allows for restarting in flight but this feature is only implemented in the engine used in the S-IVB.]
000:02:55 McCandless: 11, Houston. Thrust is Go, all engines. You're looking good.
[Between the first and second stages is a large ring, 10 metres in diameter to match the stages above and below, with a height of 5.5 metres. This ring, the interstage, is there to make room for the S-II's engines which protrude some distance below the bottom edge of the stage's wall. If, at staging, the interstage were to stay with the S-IC, there is a danger that any slight rotation of the massive first stage would cause contact between it and the engine bells on the S-II. Therefore a cut is made directly above the S-IC using a shaped explosive charge. This leaves the interstage attached to the S-II. However, the ring imposes a significant mass penalty on the second stage. So much so that it is considered a mandatory abort if the interstage doesn't separate. It too is dropped 30 seconds after the first separation. This gives time for the second stage engines to establish smooth acceleration with minimal rotation.]
000:03:17 Armstrong: Tower's gone.[Although Armstrong as Commander has his own window through the Boost Protection Cover attached to the Launch Escape Tower, and Aldrin in the center couch can see through the hatch window above his head, Collins in the right-hand couch has had his windows covered up to this point.]
000:03:44 McCandless: 11, Houston. Your guidance has converged; you're looking good.[COI is Contingency Orbit Insertion. It is essentially abort mode three and means that if the S-II were to fail, the S-IVB would have the capability to take the stack far enough towards orbit where the Service Module could ignite its large main engine to place the CSM in Earth orbit. Of course, the spacecraft would not be able to depart for the Moon as the S-IVB's power would have been consumed in reaching orbit. Instead, the spacecraft would embark on a planned for, but hopefully unrequired Earth orbit mission.]
000:05:25 Armstrong: Okay.[In case the Service Module's engine has to be used in the event of an abort, power is applied to four gimbal motors that will slightly rotate the engine in its mount so that its thrust is applied through the spacecraft's centre of mass.]
000:06:03 McCandless: Roger, 11. You're Go from the ground at 6 minutes. [Long pause.][Actually, it's just the one engine, the central engine in the cluster of J-2s. On early Saturn V flights, it was noted how severe vibrations would build towards the end of the S-II burn. The solution adopted from Apollo 10 onwards was to shut that engine down before the vibrations were expected.]
PAO: Apollo 11 Go on all sources.[The J-2 engine included a valve that allowed the mixture ratio (MR, the ratio of fuel to oxidiser) to be altered during the burn. This MR change was made to maximise propellant utilisation, hence the name PU shift.]
000:08:34 Collins: Well, it looks like a nice day for it. These thunderstorms down range is about all.[The sequence of events for the first ignition of the single J-2 engine in the third stage is essentially the same as for the engines in the S-II (see earlier description). The main change is that the supercold fuel is allowed to flow through the walls of the thrust chamber to condition it for three seconds, instead on one, before the Start Tank discharges through the turbines, spinning them up in preparation for operation.]
PAO: Velocity is 23,128 feet per second. Down range 1,000 miles, altitude 101 miles.[Comm break.]
PAO: This is Apollo Control. Based on a vector from the Instrument Unit of the third stage of the Saturn V, here on the ground we're showing an orbit of 102.5 by 99.7 nautical miles. The Flight Dynamics Officer Dave Reed wants to get some radar tracking to refine this orbit. He will report a refined orbit after more radar tracking.
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