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Apollo 10

Day 1 part 1: Countdown, launch and climb to orbit

Corrected Transcript and Commentary Copyright © 2009 by David Woods, Robin Wheeler and Ian Roberts. All rights reserved.
Last updated: 2019-06-05

[Apollo 10 was classified as an 'F' type mission, to test all elements of the Apollo spacecraft, both the CSM and LM in the lunar environment. Demonstrate performance of LM and CSM in lunar gravitation field. Evaluate CSM and LM docked and undocked lunar navigation.The mission would follow the same basic flight plan as the first lunar landing, with the exception of the final descent and landing, the surface activities and the ascent from the lunar surface. Additionally visual observations and stereoscopic strip photography of Apollo Landing Site 2 (first planned lunar landing site) was untaken.]

[During seperate operations the CSM used the call sign "Charlie Brown" and the LM "Snoopy", after the characters of the popular comic strip Peanuts© by Charles M. Schulz.]

[The Saturn V launch vehicle designated AS-505 (the fifth launch of the Apollo Saturn V stack-third manned), launched CSM-106 and LM-4 from launch complex 39-B at the Kennedy Space Center on May 18th 1969. This represented the only use of Pad 39-B during the Apollo lunar missions. Apollo 10 was crewed by Thomas P. Stafford, Commander(CDR), John W. Young, Command Module Pilot (CMP), and Eugene A. Cernan, Lunar Module Pilot (LMP). This was the first of only two all veteran crews to fly during Apollo (the other being the first lunar landing mission Apollo 11).]

[For over two months, the space and launch vehicle was tested on the pad and its explosives systems (pyrotechnics) prepared for launch. Then, on May 2 1969, the huge propellant tanks of the S-IC first stage were filled with RP-1, a refined kerosene fuel for the first stage of flight. For five days, commencing on the 5 May 1969, KSC personnel performed the Count Down Demonstration Test (CDDT), essentially a complete rehearsal of the count, including the filling of the cryogenic tanks. This proved the readiness of the launch crew and all the ground support systems that prepare the Saturn V and the Apollo spacecraft for flight. Steps were taken to ensure that the range safety explosives could not be detonated and that the vehicle's engines could not be accidentally ignited, the launch teams brought the count all the way to the point where, in a real launch, the engines of the first stage would be ignited. On completion of the CDDT, the huge quantities of super-cold liquid hydrogen (LH2) and liquid oxygen (LOX) were drained from the launch vehicle. The final preparation of the vehicle for launch then commenced.]

[The terminal countdown was commenced at 01:00:00 GMT on 17 May 1969 and proceeded with no unscheduled holds. During the automatic replenish operations of the RP-1 propellant, at approximately T minus 12 hours, the fast fill valve "open" indication dropped out causing system shutdown. Replenish operations were reinitiated in the manual_ mode and were completed satisfactorily. The problem was subsequently traced to improperly adjusted fast fill valve limit switches. Although attempts at readjustment were unsuccessful, there was no significant impact on remaining RP-1 operations. The fast fill valve is not used during the countdown after replenish is completed. If unscheduled replenish had been required, it could have been accomplished, as before, in the manual mode.]

[At six predetermined points in the count, the countdown clock is put on hold to give the launch teams an opportunity to fix problems and to allow those tasks subsequently delayed to get back on track.]

[A failure occurred during fill line chilldown on the primary LOX replenish pump during its start up procedure at approximately T minus 8 hours due to a blown fuse in the pump motor starter circuit. Troubleshooting of the faulty pump resulted in the replacement of the fuse which delayed the beginning of LOX loading by 50 minutes. However it was completed by T minus 4 hours, 22 minutes. The built-in 1-hour hold at T minus 3 hours 30 minutes precluded a launch delay. The respective tanks are purged of contaminants with nitrogen gas, then precooled. Loading is done slowly at first to get the tank walls down to the -183°C temperature of the LOX. The tanks are filled in just over three hours and, prior to launch, only need to have their contents replenished. Heat, leaking in from the ambient surroundings, causes LOX to boil away, creating the distinctive plumes of white vapour seen drifting from a loaded Saturn V.]

[The two upper stages of the vehicle, the S-II and the S-IVB, use LH2 as their fuel. To make it liquid, LH2 has to be extremely cold, presenting particular difficulties both for the construction of the rocket and the loading of fuel. In the S-IVB, an internal insulation was used so that its adhesive wouldn't have to endure the temperatures of -253°C, only 20° above absolute zero. For Apollo 10's S-II, panels of insulation were affixed to the outer surface of its tank, as explained by journal contributer Mike Jetzer in his article on S-II insulation. Its designers wished to exploit a characteristic of a special aluminum alloy (2014-T6), which increased in strength at cryogenic temperatures. Later S-II stages, Apollo 13's onward, were built using insulation that was sprayed onto its exterior.]

[Before loading, the tanks must be conditioned as this supercold fuel will solidify almost any contaminant gas within. This process begins at T minus 7 hours, 42 minutes and takes 2 hours, 40 minutes. Helium, which will not freeze in the presence of LH2, is passed through the tank repeatedly to remove air (nitrogen and oxygen) and water vapour. Then, to begin cooling the tanks, cold gas is pumped through them. Also, grooves had to be provided next to the insulation's adhesive through which helium was pumped to purge any voids of air, lest the air liquifies and causes loosening of the panels.]

[At T minus 4 hours, 49 minutes, the final chilldown of the S-II stage began by filling the tank with fuel, slowly at first. Though already cold due to the presence of LOX on the underside of the two tanks' common bulkhead and the passage of cold gas, the structure is still very warm in comparison to the LH2, which furiously boils, taking heat away as it does. It takes 46 minutes to get all the fuel required for launch into the tank, after which the level is maintained until launch to compensate for continuing boil-off. Once the S-II is full, loading the S-IVB commences in a similar manner, and it reaches launch mass at T minus 3 hours, 30 minutes.]

[During the automatic RP-1 level adjust at about T minus 50 minutes, an anomaly occurred which caused the level adjust valve to close slightly late. As a result the RP-1 flight mass percentage (which can normally be adjusted to 100 ±0.02 percent) was adjusted to 99.81 percent, but was still within Launch Mission Rules requirements of 100 ±0.2 percent. The same problem occurred during Countdown Demonstration Test (CDDT), however post CDDT troubleshooting revealed no problems with the Propellant Tanking Control System (PTCS). Further postlaunch investigation has isolated the problem to a defective printed circuit card in the PTCS.]

[The backup CMP Donn Eisele and astronaut Joe Engle went onboard the CM early in the countdown to verify the lift-off configuration, checking each switch, circuit breaker, knob and talkback indicator to ensure they were all correctly set prior to the flight crews arrival and ingress. He remained inside the CM during the flight crew ingress to assist them connecting the environment umbilicals and communications links between the spacecraft and the astronauts' space suits.]

[The crew were all onboard the CM by T minus 2 hours, 33 minutes to perform their pre-launch checks.]

[Partial overcast obscured some of the ascent, with lift-off occuring at 12:49:00 p.m. EDT]

[The transcript begins at the 9-hour point in the countdown after a hold. The Apollo 10 spacecraft sits atop its Saturn V launch vehicle on Pad 39B. Statements on the progress of the countdown are made by the Public Affairs Officers (PAO) Chuck Hollinshead and Jack King, the 'Voice of Apollo'. In this transcript the record of communications between the crew and the Mission Control Center, through 'CapCom' (the Capsule Communicator, Charlie Duke at launch) starts just prior to lift-off, continues through the ascent, including both staging events of the Saturn V launch vehicle, and insertion into Earth orbit about 12 minutes later. This first section of the transcript concludes with the confirmation of orbital parameters.]

[The journal is indebted to Gary Matylewicz who acquired and transcribed the PAO commentary from T-9 hours to T-1:36.]

-009:00:00 PAO (Hollinshead): And we are counting. We have resumed our count, now T minus 9 hours and counting. As our countdown resumes, the pad crews are making final preparations to begin fueling the cryogenics; that’s the liquid oxygen and liquid hydrogen aboard the launch vehicle. Liquid oxygen is the oxidizer used in all three stages of the Saturn V. And the liquid hydrogen is the fuel for the second and third stages. RP-1, the fuel for the first stage, was loaded during the Countdown Demonstration Test on May 2. It’s a kerosene type fuel and unlike the cryogenics, it can remain the launch vehicle for some time. The prime crew for Apollo 10, astronauts Thomas Stafford, John Young, and Eugene Cernan, will be wakened this morning shortly after 7:30. Last night they had a roast beef dinner with Vice President Spiro Agnew, NASA Administrator Thomas Paine, and a number of officials from the aerospace industry. These officials were invited to dinner with the astronauts in the crew quarters at Kennedy Space Center. Our weather for a 12:49 launch continues to look satisfactory. Now at T minus 8 hours, 58 minutes and counting; this is Apollo Saturn Launch Control.

-008:17:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 8 hours, 17 minutes and counting. The pad area is now being cleared of non-essential personnel as the launch team makes final preparations for cryogenic loading. In the cryogenic loading sequence, liquid oxygen is brought aboard all three stages first, starting at the top of the launch vehicle, starting at the third stage and working down. At completion of liquid oxygen, or LOX as it’s known; at the completion of LOX loading, the liquid hydrogen is brought aboard the second stage and cryogenic loading is completed as we bring aboard liquid hydrogen in the third stage. The actual tanking is scheduled to be completed by the 3-hour, 30-minute mark in the countdown, although it will be necessary to top off or replenish the cryogenic fuels down through the final minutes of the count. This is necessary since small portions of the supercold liquids will boil off during the tanking operation. Vents on the launch vehicle allow the LOX to boil off and vented to the atmosphere and the liquid hydrogen is carried to a special burn pond where the highly flammable gas is burned off in controlled conditions. Tonight the hydrogen burn pond is very clearly visible although in the daylight the burning is so purely that it is almost impossible to detect with the naked eye. For their dinner tonight the crew in the crew quarters, the dinner actually last night, in the crew quarters the astronauts and their guests had shrimp cocktail, roast beef au jus, asparagus salad, fresh string beans, mashed potatoes, and for dessert they had fresh strawberries and ice cream. The astronauts now asleep in the quarters, will be awakened about 4 hours from now. Now at T minus 8 hours, 16 minutes and counting; this is Apollo Saturn Launch Control.

-007:49:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 7 hours, 49 minutes and counting. We’re now bringing - we’re now actually cooling down, chilling down the liquid oxygen lines in preparation for bringing the LOX aboard the third stage of the launch vehicle. LOX tanking actually scheduled to start at the T minus 7-hour and 43-minute mark in the count, just a few minutes from now. Prior to running the liquid oxygen into the system at a fast rate, it’s necessary to cool down or pre-condition the tank and transfer lines to accept the LOX which is transferred and stored at -297 degrees Fahrenheit [-183° Celsius]. The tank aboard the Saturn V is cooled down by bringing aboard the first 5 per cent of the LOX on the third stage at a slow fill or cool down rate of 500 gallons [1,900 litres] per minute. After the 5 per cent is aboard, this rate is doubled to a 1,000 gallons [3,800 litres] per minute. Over 20,000 gallons [76,000 litres] of liquid oxygen will be loaded on the third stage alone of the Saturn V in about 25 minutes if all goes as scheduled. The pump and transfer lines to the second stage will be chilled down during the fueling of the third stage in preparation for bringing aboard the LOX to the second stage just as we finish on the third stage. Now at T minus 7 hours, 48 minutes and counting; in our final preparations for cryogenic loading, this is Apollo Saturn Launch Control.

-007:19:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 7 hours, 19 minutes and counting. Liquid oxygen, the oxidizer used in all three stages of the Saturn V launch vehicle, is now flowing into the third stage from the supply tank on the perimeter of the pad area. The oxidizer supply is located on the west side of the pad and the fuels, both RP-1 for the first stage and liquid hydrogen fuel for the second and third stages are located on the east side of the pad. The flow to the vehicle is controlled remotely from the Launch Control Center which is about five miles away from Pad B. A recent update on the weather predictions for launch time shows very little change from earlier reports. There will be predicted scattered low clouds in the area, winds from the southeast about 15 knots. The temperature on Kennedy Space Center is expected to be about 81 degrees Fahrenheit [27° Celsius] at launch time, slightly higher on the mainland. The seas in the KSC offshore area will be approximately four feet [1.2 metres]. Weather predictions generally satisfactory for our 12:49 launch this morning. Now at T minus 7 hours, 17 minutes and counting; this is Apollo Saturn Launch Control.

-006:40:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 6 hours, 40 minute [sic] mark in our count – T minus 6 hours 49 minutes and counting. We’re continuing to bring the liquid oxygen aboard the Saturn V launch vehicle. We resumed our count at 2:49 AM this morning. This was following a 10-hour 49-minute built-in hold. We have one more built-in hold in our countdown, that will come at the 3-hour, 30-minute mark. At that time, the cryogenic fueling is scheduled to be completed and technicians will begin to prepare the spacecraft for the astronaut crew. Astronauts Stafford, Young, and Cernan are scheduled to enter their Apollo 10 Command Module at T minus 2 hours and 40 minutes in the countdown. Now at T minus 6 hours, 48 minutes and counting; this is Apollo Saturn Launch Control.

-006:15:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 6 hours, 15 minutes and counting, T minus 6 hours, 15 minutes and counting as we continue in the cryogenic loading. Now bringing liquid oxygen - liquid oxygen aboard the Saturn V launch vehicle. When the liquid oxygen is brought aboard all three stages, we’ll begin bringing aboard the liquid hydrogen. LO2, or LOX as it’s called, is brought aboard at -297 degrees Fahrenheit [-183° Celsius]. The liquid hydrogen is transferred at -423 degrees Fahrenheit [-253° Celsius]. RP-1 which is the fuel for the first stage is a kerosene type fuel. It’s brought aboard at ambient temperatures. RP-1 was loaded aboard the first stage during the Countdown Demonstration Test on May 2nd and has remained aboard since that time. Now continuing in our cryogenic fueling. At T minus 6 hours, 14 minutes and counting; this is Apollo Saturn Launch Control.

-005:37:00 PAO (Hollinshead): This is Apollo Saturn Launch Control. We’re now at T minus 5 hours, 37 minutes and counting. Our countdown proceeding at this time as we’re continuing to load liquid oxygen aboard the Saturn V launch vehicle. The liquid oxygen, over 20,000 gallons [76,000 litres], has been loaded aboard the S-IVB or third stage of the vehicle. We’re now in the midst of loading the liquid oxygen aboard the second stage. We move on down the vehicle. When we finish the second stage, liquid oxygen will be loaded aboard the first stage and then the liquid hydrogen fuel for the second and third stage will be loaded. Now continuing with our countdown at T minus 5 hours, 37 minutes and counting. We have one more built-in hold in our countdown. That will come at the T minus 3-hour and 30-minute mark and will last one hour. Now T minus 5 hours, 37 minutes and counting; this is Apollo Saturn Launch Control.

[The role of Public Affairs Officer is handed to Jack King.]

-005:09:00 PAO (King): This is Apollo Saturn Launch Control at T minus 5 hours, 9 minutes and counting; T minus 5 hours 9 minutes and counting. We are proceeding with the Apollo 10 countdown at this time. At this point we have about a 10 per cent load in our final phase of the liquid oxygen loading of the three stages of the Saturn V launch vehicle. We’re bringing the LOX aboard the first or the S-IC stage. This is the largest amount of the liquid oxygen of the 3 stages. We’ll be loading some 342,000 gallons [1.3 million litres] of liquid oxygen aboard the first stage. We’ve already completed the LOX load of the third stage and second stages. We brought some 20,000 gallons [76,000 litres] aboard the third stage and some 87,000 gallons [330,000 litres] aboard the second stage. The countdown proceeding at this time. We were a little late getting into the propellant loading. We picked up our countdown as planned at 2:49 AM EDT, however, because of several very minor ground support problems in the pad area, we were a little late starting our propellant loading. These problems were cases such as a blown out fuse at the liquid oxygen facility that had to be replaced. We’re probably about 45 minutes behind in the overall propellant loading. Of course, after we complete loading liquid oxygen aboard the first stage, we’ll be in a position to start the final phase of the overall propellant loading, that is bringing the liquid hydrogen fuel aboard the second and third stages of the Saturn V. One other anomaly that we are looking at this time, we have had a drop of pressure in a flex line that carries nitrogen into the Instrument Unit of the Saturn V. This is a line aboard the vehicle in the Instrument Unit and the nitrogen, of course, used to condition the Instrument Unit. This does not appear to be a constraint at this time, this drop in pressure. However, we are continuing to monitor this situation at this time as the countdown proceeds. The prime crew for Apollo 10; astronauts Tom Stafford, John Young, and Gene Cernan; are still should be asleep at time. They are due to be awakened at about 7:34 AM. That’s our present status now. At 5 hours, 6 minutes, 30 seconds and counting; this is Launch Control.

-004:45:00 PAO (King: This is Apollo Saturn Launch Control at T minus 4 hours, 45 minutes and counting. We’re proceeding with the Apollo 10 countdown and we now have some 35 per cent of the liquid oxygen aboard the first stage, the S-IC stage of the Saturn V. This is the final phase of the loading of the liquid oxygen since earlier in the count we did bring the LOX supply aboard the third and second stages of the vehicle. We’re now loading the liquid oxygen into the first stage at a rate of some 10,000 gallons [38,000 litres] per minute. We’ll continue to do this until we get to the 98 per cent level in the tank and then we’ll go slow fill to assure that we have a complete load aboard. When we complete our liquid oxygen loading, we’ll be ready to go into the final phase of the fuel loading, bringing the hydrogen supply, the liquid hydrogen supply, aboard first the S-II, the second stage, and then the S-IVB third stage. All aspects of the countdown are still going well at this time. This one anomaly is still with us which was referred to on previous announcements, that is a drop in pressure in a nitrogen flex line within the Instrument Unit, the guidance package of the Saturn V. The Instrument Unit, of course, located above the third stage of the vehicle. This flex line carries nitrogen gas and is used to condition a part of the Instrument Unit. It chills when applicable and also can provide heat when necessary. Of course we want to keep the Instrument Unit warmer when we have the liquid hydrogen aboard. Liquid hydrogen, of course, in the second and third stages must be maintained some 425 degrees below zero [Fahrenheit, -254° Celsius]. At other times this nitrogen is used to keep the Instrument Unit, or portions of the Instrument Unit, cool. However, this is one of a number of flex lines in the Instrument Unit and it is not a primary one in that manner. There are a number of flex lines in the Instrument Unit that carry this nitrogen for conditioning purposes. As we continue to monitor the status of the Instrument Unit, the temperatures are good and we are going to keep a close eye on this as the countdown proceeds. We’re now at T minus 4 hours, 42 minutes, 35 seconds and counting. The prime crew should be getting up at about 7:34, which is about a half an hour from this time. We’ll stand by for further reports. This is Launch Control.

-004:16:00 PAO (King): This is Apollo Saturn Launch Control at T minus 4 hours, 16 minutes and counting. We’ve completed our loading of the liquid oxygen aboard the three stages of the Saturn V launch vehicle. We’re standing by here in the Control Center before beginning the final phase of the overall propellant loading, that is to proceed with bringing the liquid hydrogen fuel aboard the second and then third stage of the vehicle. We’ll be loading some more than 267,000 gallons [1 million litres] of liquid hydrogen into the second stage. This will be followed by more than 73,000 gallons [276,000 litres] going into the S-IVB third stage. Liquid hydrogen, of course, one of the cryogenic fuels. That is, it must be maintained at extremely low temperatures. As a matter of fact, it comes aboard at a temperature of some 425 degrees below zero [Fahrenheit, -254° Celsius]. So we’ll be standing by to pick up our final phase of the propellant loading. In the meantime we have the latest report from the Manned Spaceflight Meteorology Group here at the Kennedy Space Center with a weather forecast for launch time as follows: The weather group reports the weather conditions will be satisfactory for the launch of Apollo 10. In the Kennedy Space Center area and particularly Pad B, Launch Complex 39, the forecast calls for partly cloudy skies, winds - surface winds from the southeast, 15 knots with gusts up to 22 knots. Temperature in the launch area about 82 degrees [28° Celsius] at launch time. The launch time of course, 12:49 PM EDT. The weatherman reports there are rather rough seas offshore off the Kennedy Space Center, sea state of about four feet [1.2 metres], however, this is acceptable for a launch attempt. To repeat, the seas are a little high off the Cape but acceptable for a launch attempt. The weatherman further states that the chance of thunderstorms are much lower today than usual. In the Atlantic Ocean we have 2 areas of rough seas, one in the west Atlantic and the other in the east and a shower path about 2/3 the way across the Atlantic Ocean. All other weather conditions in the around the world track, as far as the Pacific and the complete track are acceptable. So we are Go for weather at this time. At T minus 4 hours, 13 minutes, 38 seconds and counting; this is Launch Control.

-004:02:00 PAO (King): This is Apollo Saturn Launch Control, T minus 4 hours, 2 minutes and counting; T minus 4 hours, 2 minutes and counting and we are proceeding with the Apollo 10 mission countdown at this time. We have just been given the go ahead here in the Control Center to start the final phase of the propellant loading, bringing in that extremely cold liquid hydrogen into the second and then into the third stage. This is the final phase of the propellant loading. We are probably some 45 minutes behind in the overall propellant loading but this is not a major concern at this time. As planned, we do have a built-in hold of one hour’s duration that will come at the 3-hour and 30-minute mark in the countdown. We have information now from the crew quarters located some five miles from the Launch Control Center here at KSC, that the Apollo 10 astronaut crew all are up and taking their physical examinations at this time. Spacecraft Commander Tom Stafford and Command Module Pilot John Young were awakened at 7:34 AM EDT. The third member of the crew, astronaut Gene Cernan did arise a little earlier. He was awakened at 6:50 AM since he had a special guest this morning, Father Eugene Cargill, he spells his last name C-A-R-G-I-L-L. Father Cargill is from a church in Dickenson, Texas, which, of course, is close by the Space Center, the Manned Spacecraft Center in Houston. Astronauts now undergoing their medical examination. We are proceeding with the hydrogen load. We still have an abnormalty with the flex line in the Instrument Unit. This is a line that carries nitrogen, one of a number of lines that carry nitrogen to condition the Instrument Unit. We continue to monitor this system, however, there appears to be no constraint at this time. The temperatures are satisfactory in the Instrument Unit and we are proceeding. We’re now coming up on the 4 hour mark. MARK, T minus 4 hours and counting. This is Launch Control.

-003:44:00 PAO (King): This is Apollo Saturn Launch Control at T minus 3 hours, 44 minutes and counting. We’re some 14 minutes away from our final planned built-in hold. It will be a built-in hold of some one hour’s duration and will come at the 3-hour, 30-minute mark in the count. Our countdown is still proceeding. At this time we are in the midst of liquid hydrogen fuel loading of the second stage of the Saturn vehicle. This will be followed by the final phase of the fuel loading bringing the hydrogen aboard the third stage. We’ve been a little bit behind our propellant loading for most of the count mainly because we got a late start because of some minor ground support problems at the pad. As a result of the hydrogen loading will continue into the built-in hold period. The Apollo 10 prime crew, astronauts Tom Stafford, John Young, and Gene Cernan are up at their crew quarters at the Manned Spacecraft Operations Building some five miles from the Launch Control Center here at Launch Complex 39. At this time they should be finishing up their medical exams down the hall from the crew quarters and we’ll stand by for further reports on their status. We’re now at 3 hours, 42 minutes, 50 seconds and counting. This is Launch Control.

-003:00:00 PAO (King): This is Apollo Saturn Launch Control. We’re in our built-in hold, our final built-in hold on the Apollo 10 countdown. T minus 3 hours, 30 minutes and holding. This hold was declared about three minutes ago, we have it logged at 8:19 AM EDT. The liquid hydrogen loading of the second stage, bringing the fuel aboard the second stage of the Saturn V launch vehicle, continuing at this time. We now have some 70 per cent of the liquid hydrogen aboard and we’re pouring the hydrogen in at a rate of some 10,000 gallons [38,000 litres] per minute. After we complete this we will be ready to proceed with the third stage fuel loading bringing liquid hydrogen there also. Report from the crew quarters some five miles down the road from Launch Complex 39. The astronauts, of course, are up. They have completed their medical examination. They were declared physically fit after examination by Doctors John Teegan and Allen Harter. Doctor Teagan spells his last name T-E-E-G-A-N, Doctor Allen Harter, H-A-R-T-E-R. Astronauts now are sitting down for breakfast. The traditional menu of orange juice, steak and eggs, toast, jelly, and coffee. They have some five or six guests for breakfast this morning. We understand that Mr. George Low, the Apollo Program Manager at the Manned Spacecraft Center is there. Also are his two prime deputies; the deputy for Command/Service Module operations, Mr. Ken Klenkneickt, and the deputy for Lunar Module operations, General Rick Bolender. Also present are Mr. George Scular, the local base manager for Grumman Aircraft, makers of the Lunar Module, and Mr. Buzz Hello, who is the base manager for North American Rockwell here at the Kennedy Space Center. North American, of course, are contractors for the Command and Service Module of the spacecraft as well as the second stage of the Saturn V launch Vehicle. We also understand that Father Eugene Cargill, a friend of Gene Cernan, who met Gene earlier this morning at the crew quarters, Father Cargill is from a church in Dickenson, Texas. Father Cargill also attending the breakfast according to the reports we have here at this time. That’s our present status. We’re in the hold at 3 hours, 30 minutes. Duration of the hold 60 minutes. We’ll be looking at resuming our countdown at 9:19 AM EDT. This is Launch Control.

-003:00:00 (continued) PAO (King): This is Apollo Saturn Launch Control. We’re in our built-in hold at T minus 3 hours, 30 minutes and holding. We’ll be resuming our countdown at 19 minutes past the hour, 9:19 AM EDT. The prime crew for the Apollo 10 mission, astronauts Tom Stafford, John Young, and Gene Cernan, still in their crew quarters some five miles from Launch Complex 39, enjoying breakfast at this time. The traditional menu of steak and eggs. We’re just completing the liquid hydrogen loading of the second stage. We’re up to 99 per cent according to the reports just received here in the Control Center and shortly will be proceeding into the final phase of the propellant loading, that is bringing the hydrogen aboard the third stage of the Saturn V launch vehicle. A primary portion of the final phase of the countdown is devoted to the propellant loading, takes some 5½ hours usually and it’s been in progress since we resumed our countdown shortly before 3 AM EDT this morning. Propellant loading still in progress at this time. We did fall behind a little bit at the start because of some minor ground support problems at the complex. We are still proceeding and loading during the built-in hold. We’ll be loading more than three quarter of a million gallons [2.8 million litres] of liquid oxygen and liquid hydrogen this morning. We’ll have a total load of propellants including the fuel in the first stage close to a million gallons [3.8 million litres]. We have had one anomaly in our countdown this has been a drop in pressure in a flex line within the Instrument Unit. This flex line carries nitrogen gas which helps to condition a certain section of the Instrument Unit, however, this particular line is used only during ground operations and is not required for launch. We’re continuing to monitor the status of the Instrument Unit, particularly as far as the temperatures are concerned. They are acceptable and the difficulty with this flex line appears not to be a constraint at this time. We are continuing our hold, all still going well with the propellant loading. This is Launch Control at T minus 3 hours, 30 minutes and holding.

-003:00:00 (continued) PAO (King): This is Apollo Saturn Launch Control. We’re still in our built-in hold, T minus 3 hours, 30 minutes and holding. We’ll be resuming our countdown 19 minutes past the hour. All still looking good with the Apollo 10 count at this time as we go into the final phase of the propellant loading. We now have a 10 per cent supply of the liquid hydrogen fuel aboard the third stage. This is the final phase of the loading. We’ll be bringing some 73,400 gallons [278,000 litres] of liquid hydrogen fuel aboard the S-IVB stage. It should take about 30 minutes or so to accomplish this task, probably a little less time than that. We’re now loading about 3,000 gallons [11,400 litres] a minute. The prime crew for Apollo 10, astronauts Tom Stafford, John Young, and Gene Cernan, are finishing up their breakfast at the crew quarters. The traditional menu of steak and eggs, orange juice, toast, jelly and coffee. They had a number of guests for breakfast. We did not have a complete list on a previous announcement and we will cover that list again at this time. The guests for breakfast included the Apollo Program Manager at the Manned Spacecraft Center, Mr. George Low, his 2 deputies, Mr. Ken Klenkneickt, who is deputy for Command and Service Modules, and Rick Bolenger, who is deputy for Lunar Module operations. Also at the breakfast was Mr. George Scular, the local base manager for Grumman Aircraft, here at the Kennedy Space Center, Mr. Buzz Hello, base manager for North American Rockwell at KSC, also Father Eugene Cargill, a priest from Dickenson, Texas, who is a friend of Gene Cernan. Four astronauts also joined their fellow crew members for breakfast. Scientist-astronaut Jack Schmitt, who has spend the past week briefing the crew on lunar topography was at the breakfast along with Donn Eisele, the backup Command Module Pilot for this mission, Ed Mitchell, a member of the support crew for the Apollo 10 mission, and finally astronaut Jack Lousma who is at the Stoney Console here in the Control Center, Stoney, of course, is the capsule communicator here in the Firing Room. His job is to talk to the astronauts over the final moments of the count. That’s our status. At the present time we’re still in the hold; T minus 3 hours, 30 minutes and holding. All looking good with the count, however, at this time. This is Launch Control.

003:00:00 (continued) PAO (King): This is Apollo Saturn Launch Control. We’re still in our built-in hold; we’re at T minus 3 hours, 30 minutes and holding. We expect to resume our count some 16 minutes from this time. All going well with the Apollo 10 countdown. We’re finishing up the hydrogen loading of the third stage of the Saturn V launch vehicle. Our crew continuing to monitor the status of the propellants in the various other stages and they appear to be stable as we continue to top off the liquid oxygen and liquid hydrogen supplies with the exception, of course, of the S-IVB third stage where we’re still filling the tanks at this time at a rate of about 3,000 gallons [11,400 litres] per minute. The Apollo 10 pilots; astronauts Tom Stafford, John Young, and Gene Cernan; now have finished their breakfast at the crew quarters. They had the steak and egg menu which is normal on astronaut flights. They had ten guests for breakfast. They have now completed breakfast and are walking down the hall, should now have arrived at the suit room where they will don their space suits and standby to be called to the pad. Under the normal countdown procedures, and it is expected if all continues to go well, the astronauts will follow it. They will depart from their crew quarters at 44 minutes past the hour, which is some 40 minutes from this time. All is still proceeding satisfactorily with the Apollo 10 count. We expect to resume our countdown in about 15 minutes now. We’re 3 hours, 30 minutes and holding. This is Launch Control.

003:00:00 (continued) PAO (King): This is Apollo Saturn Launch Control. We’re at T minus 3 hours, 30 minutes and holding but we’re standing by to resume the countdown at this time. MARK, we are now counting, T minus 3 hours, 30 minutes and counting. We’re proceeding with the Apollo 10 countdown. We resumed our countdown as planned at 19 minutes past the hour. This has been a planned built-in hold of 60 minutes duration. We did use most of that hold time, however, to complete our propellant loading of the Saturn V launch vehicle. A short while ago we did complete the loading of the hydrogen aboard the third stage which is the final phase and we are now topping off the liquid oxygen and liquid hydrogen supplies in the three stages of the Saturn V vehicle. The Apollo 10 crew; astronauts Tom Stafford, John Young, and Gene Cernan; in their suit room at the crew quarters, some five miles from the launch pad. They’re donning their suits and checking them out at this time. They are due to depart some 20 minutes from this time, check, make it 24 minutes from this time, 9:44 AM EDT. They’ll be leaving the quarters and take that nine-mile trip to the launch pad. A closeout crew now standing by to go up to the 320-foot level, open the hatch on the Apollo spacecraft, and make final preparations for the astronauts’ arrival. A member of the support team, astronaut Joe Engle, is with that closeout crew and he will board the Apollo spacecraft and make some final preparations in readiness for the astronaut team, the Apollo 10 team, to come aboard. We’re now 3 hours, 28 minutes, 29 seconds and counting. We are Go for launch at this time. This is Launch Control.

-003:26:00 PAO (King): This is Apollo Saturn Launch Control at 3 hours, 26 minutes and counting. Count still going well at this time. Another check of the weather; the weather forecast still good for a launch to the Moon today. The forecast in the KSC area calls for partly cloudy skies at launch time, winds from the southeast at 15 knots with gusts up to about 22. We expect the temperature in the launch area of about 82 degrees [Fahrenheit, 28° Celsius]. The seas are a little rough off Cape Kennedy today but acceptable for a launch attempt. We have a sea state of about four feet. Across the Atlantic we have a little rough weather but once again, it is acceptable for launch. There is a shower path about two thirds the way across the Atlantic Ocean and there is two areas of rough seas, one in the west and one in the east Atlantic. Around the rest of the world track, the weather is acceptable. A check of altitude wind conditions indicate that they are also acceptable for launch and good enough that we will be able to use a launch window from azimuth of 72 degrees to 96 degrees. This means that our window in time will extend in EDT, will extend from 12:49 to 4:14 PM EDT. That’s our status at the present time. All aspects of the mission Go. 3 hours, 24 minutes, 25 seconds and counting. This is Launch Control.

[If Apollo 10 launches at the start of the launch window, then the appropriate azimuth, or heading from the launch pad is 72° in order to be in the plane of the Moon's orbit at TLI. If the launch is delayed to a later time, then the azimuth must be recalculated for that time. This is to keep the plane of the vehicle's orbit aligned with that of the Moon, compensating for the turning of Earth. The constraint at the end of the launch window is that beyond 96°, the vehicle's orbital path would go beyond the network of ground stations scattered across the globe.]

-003:16:00 PAO (King): This is Apollo Saturn Launch Control; 3 hours, 16 minutes and counting. We’re proceeding with Apollo 10 satisfactorily at this time. Astronaut Joe Engle, a member of the support team on the Apollo 10 team, is now aboard the Apollo 10 spacecraft at the 320-foot level at Pad B. Engle will checkout a number of systems in preparation for arrival of the prime crew of astronauts Tom Stafford, John Young, and Gene Cernan. These checkouts include activation of the caution and warning system aboard the spacecraft, adjusting the chlorine content of the astronauts’ drinking water, the oxygen system and also setting and adjusting the lights within the spacecraft. Engle will also give the three prime crewmen a hand in getting tied into the suit system once they’re aboard before he will depart the spacecraft. The prime crew due to leave their quarters some 10 minutes or so from this time. We’ll standby for their departure. All other aspects of the count going well. The propellants all aboard the Saturn V launch vehicle appear to be stable and we continue to top off the cryogenic supply, that is the liquid oxygen and liquid hydrogen. Now 3 hours, 14 minutes, 40 seconds and counting; this is Launch Control.

-003:10:25 PAO (King): This is Apollo Saturn Launch Control. We’re at 3 hours, 10 minutes, 25 seconds and counting. We have been advised by the Spacecraft Test Conductor that we expect the Apollo 10 crew to be coming out of their quarters shortly. When they come out they will board their transfer van for a trip of nine miles from the Manned Spacecraft Operations Building where their crew quarters are located here at the Kennedy Space Center to Launch Pad B at Complex 39 where the Saturn V, Apollo Saturn V space vehicle is going through the final portion of its countdown at this time. The Apollo 10 crew of astronauts Stafford, Young, and Cernan have been up two to two and a half hours at this time; actually Gene Cernan got up roughly a half hour before his comrades in order to greet a friend of his, a Catholic priest from Dickenson, Texas. Stafford and Cernan, correction, Stafford and Young were awakened at 7:34 AM EDT. The three crewmen then went down the hall from their crew quarters to take a physical examination. They were declared physically fit by Doctors Jack Teegan and Allen Harter, who performed the physical examinations this morning. The crew then sat down for breakfast, the normal astronaut fare of steak, eggs, orange juice, toast, jelly, and coffee was on the menu this morning. They had about ten guests for breakfast. They were eating breakfast during the built-in hold portion of the count while at the launch pad the crews were still completing the propellant loading of the Saturn V space vehicle. We are standing by for the Apollo 10 crew to come out of their quarters. This is Launch Control.

-003:08:00 PAO (King): This is Apollo Saturn Launch Control; 3 hours, 8 minutes and counting. The Apollo 10 crew; Tom Stafford, John Young, and Gene Cernan now have departed the crew quarters and they’re now boarding the transfer van for the trip to the pad. Director of Flight Crew Operations, Deke Slayton, also aboard the transfer van, he’ll drop off from the van and join the launch team here in Firing Room 3 at the Launch Control Center. The trip from the crew quarters to the launch pad is about nine miles and we give about 17 minutes in the countdown between the crew departure and arrival at the pad. Once the crew does arrive at Launch Pad B they will proceed by high speed elevator to the 320-foot level. The three astronauts will be accompanied by two suit technicians. After the elevator arrives at the 320-foot level, the capsule communicator here in the Firing Room, astronaut Jack Lousma, will lock that elevator at that point. The Commander Tom Stafford, and the Lunar Module Pilot Gene Cernan, the men who sit in the left hand and right hand seats, will depart from the elevator with one of the suit technicians. They will go cross the swing arm and then proceed to board the spacecraft. John Young, the man in the middle seat, will remain in the elevator until he is called a little later in the count. Young will remain in the seat in the elevator until his 2 comrades have gone aboard the spacecraft. We’ll give about ten minutes to each astronaut to come aboard during this period. In the meantime at this point, at the 320-foot level, astronaut Joe Engle is aboard the spacecraft performing final checks in preparation for the crew arrival. We are Go for Apollo 10 at this time, coming up on 3 hours, 6 minutes and counting. This is Launch Control.

-002:56:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours, 56 minutes and counting. The Apollo 10 crew still on their way to Launch Pad B here at Complex 39. Their transfer van just passed by the Launch Control Center and after a brief stop to drop off Flight Crew Director Deke Slayton, the truck now proceeding to the launch pad. All still going well as the closeout crew at the 320-foot level makes their final readiness checks in preparation for the crew’s arrival shortly at the pad. As reported, the crew will go up a high speed elevator to the 320-foot level. The Commander, Tom Stafford, and Lunar Module Pilot, Gene Cernan, will first go across the access arm, Swing Arm number 9, to the Command Module White Room and then will board the spacecraft. The Command Module Pilot, John Young, will remain in the elevator until he’s called some 10 or 15 minutes later. All still going well; 2 hours, 55 minutes and counting. This is Launch Control.

-002:46:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours 46 minutes and counting. Apollo 10 pilots; Tom Stafford, John young, and Gene Cernan now have arrived at Launch Pad B. We have them clocked at 1 minute past the hour when the transfer van came up to the elevator at the base of the pad. The three crewmen now have left one elevator and proceeded into the Mobile Launcher where they’ll catch the high speed elevator that will take them to the 320-foot level where their spacecraft is located. We expect they’ll be up there in just a matter of minutes. As reported, Stafford and Cernan will go across the swing arm first. John Young will wait until his two crewmates are aboard the spacecraft. Astronaut Joe Engle still aboard the spacecraft making some final checks. He’s checked the water gun, made sure the chlorine content is satisfactory, adjusting the lights in the cabin and will standby for the crew arrival. Engle will remain in the spacecraft for a certain time to aid the crew with certain switches that need to be depressed during some early checkouts before the hatch is closed. We’ve completed a few program tests with the computer here in the Control Center. All is still going well. T minus 2 hours, 44 minutes, 45 seconds and counting; this is Launch Control.

-002:42:46 PAO (King): This is Apollo Saturn Launch Control. T minus 2 hours, 42 minutes, 46 seconds and counting. Astronauts Tom Stafford, the Apollo 10 commander, and Gene Cernan have arrived in the White Room along with their suit technician. They shook hands with the pad leader and several of the technicians in the White Room and Tom Stafford, I believe, has gone aboard the spacecraft, I believe at 10:06, 6 minutes past the hour, 10:06 AM EDT. The commander is the first man aboard, he sits in the left hand seat in the spacecraft and the suit technician and astronaut Joe Engle will help to check him in. First tying him into the suit circuit system to assure that satisfactory oxygen is coming through the system. There will be various medical checks and communications checks. So the astronauts are now proceeding with ingress, ingress into the Command Module. We have Stafford and Young [means Cernan] in the White Room, Stafford aboard the spacecraft at this time and astronaut John Young in the elevator at the 320-foot level sitting comfortably in a chair with a suit technician awaiting a call to the White Room. He’ll be the final member of the crew to go aboard. All still going well with the count, our weather is Go, the tracking elements also Go at this time; 2 hours, 41 minutes, 27 seconds and counting; this is Launch Control.

-002:36:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours, 36 minutes and counting. The spacecraft commander Tom Stafford now aboard the Apollo 10 spacecraft. He has checked in with Test Conductor Skip Chauvin and has gone through some various communications checks. The suit technician behind him and astronaut Joe Engle in front of him in the spacecraft. Engle actually in the Lower Equipment Bay aiding the astronaut to strap in. The Lunar Module Pilot Gene Cernan has just come aboard and Skip Chauvin said welcome aboard the 12:49 special, referring to the launch time for the Apollo 10 count. We now have both the commander and Lunar Module Pilot aboard. John Young should be coming across the swing arm shortly as the third crew member to come in. Once the astronauts are strapped in, one of the first things that is accomplished is to check some switches on the panels nearby in the event the astronaut might have brushed them as he came aboard. This is accomplished with a switch list check, a check in which the Test Conductor reads off the various switch settings where the switches should be and the astronaut in each case verifies. We also do a quick medical check on each of the crewmen as they are aboard to assure we are receiving medical data from them here on the ground. The countdown still proceeding, all going well. The weather is Go at this time. We’re at T minus 2 hours, 34 minutes, 32 seconds and counting; this is Launch Control.

-002:26:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours, 26 minutes and counting. All three Apollo 10 crew members now aboard the spacecraft. The third member to come aboard, John Young, went over the sill; we have it logged at 10:16, 16 minutes past the hour. The astronauts are now tied into their suit circuit system starting to breath the pure oxygen supply within that system. During this period we sample the suit circuit system to assure ourselves we have at least 95 per cent O2, 95 per cent oxygen in that system. The astronauts will fly breathing the oxygen system. Of course, the cabin system, however, will be a combination of oxygen and nitrogen. We’re coming up shortly on some communications checks between the Flight Director Glynn Lunney at the Mission Control Center in Houston and the astronaut crew here at Pad B. The countdown is still proceeding satisfactory aimed toward our planned lift-off time for this lunar flight of 12:49 PM EDT. We’re now 2 hours, 25 minutes and counting; this is Launch Control.

-002:16:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours, 16 minutes and counting. T minus 2 hours, 16 minutes and counting. All is Go with the Apollo 10 countdown for the launch to the Moon at this time. Astronaut Joe Engle, a member of the support crew, now has departed from the spacecraft. From the conversation between the Test Supervisor, it appears he did depart reluctantly. As he did come out of the spacecraft, John Young remarked, he was sorry but there was just three round trip tickets for the flight. Engle had been in the spacecraft to give the three crewmen a hand on the final switches and to assure that they were satisfactorily in the spacecraft as far as the various connections and the integrity of their spacesuits and the oxygen system they’ll be breathing. The Spacecraft Test Conductor now has given a go ahead to the closeout crew at the 320-foot level to proceed with preparations for closing the Command Module hatch. Also coming up shortly will be a series of abort advisory system checks with the Spacecraft Commander Tom Stafford. Stafford has a number of cue lights in front of him in the spacecraft which can indicate difficulties on the flight. Coming up shortly we’ll make some checks of these lights in which the Test Conductor, the Launch Operations Manager here in the Firing Room and Houston Flight, the Flight Director in Houston, can send light cues to the spacecraft to inform the Commander that he is having trouble. We’re checking out that system, we will be checking it out shortly. All still going well. We have a flight azimuth in the computer of 72 degrees, that’s for a lift-off of 12:49 PM EDT. T minus 2 hours, 14 minutes, 15 seconds and counting; this is Launch Control.

[The intention is for Apollo 10 to head away from the launch pad at an azimuth of 72° in order to be in the plane of the Moon's orbit at TLI. The launch vehicle sits on the launch pad aligned with the cardinal points such that if it were to launch and perform a simple pitch-over, it would fly directly east, an azimuth of 90°. To achieve a 72° azimuth, the gimbal-mounted guidance platform within the Instrument Unit is rotated to point to this azimuth and it is held there by a servo system that uses a theodolite located 210 metres directly south of the pad. The IU and the platform housing include small windows to allow the light from this theodolite to reach the sensing apparatus within. The platform must be held at this 72° alignment because Earth is turning and the azimuth will only become relevant at the moment of lift-off. It is only 17 seconds before lift-off that the platform is released to hold an orientation in space. Upon lift-off, the Saturn V will roll around to align the vehicle with the platform and it will then begin to tilt in a simple pitch motion to achieve the desired flight path.]

-002:06:00 PAO (King): This is Apollo Saturn Launch Control at T minus 2 hours, 6 minutes and counting. We are still Go for Apollo 10 at this time. The hatch on the spacecraft has been closed. We have it logged at 35 minutes past the hour. Astronaut Tom Stafford, the spacecraft commander, has completed his series of abort advisory system checks. These are checks of the cue lights on his abort panel on the spacecraft and he’ll be gearing up shortly in preparations for a major test that occurs as far as the overall vehicle is concerned, the Emergency Detection System test, the EDS test. This is a test of some 30 minutes duration in which the launch vehicle and spacecraft participates. This is to assure that all the various detection systems aboard the vehicle to alert the astronauts of difficulty either on the ground or in flight actually will operate. This is the final check of that system and a major highlight of the final countdown. Shortly we will also be making preparations to bring the cabin atmosphere up now that the hatch is closed. From a ground source we will bring in a supply of an atmosphere of 60 per cent oxygen and 40 per cent nitrogen into the cabin. We will purge the cabin with a 60/40 atmosphere and then assure ourselves that there are no leaks. We’ll make some quick leak checks to make sure the spacecraft is secure. All going well; 2 hours, 4 minutes, 30 seconds and counting; this is Launch Control.

-001:56:00 PAO (King): This is Apollo Saturn Launch Control. T minus 1 hour, 56 minutes and counting. Countdown still proceeding toward our planned lift-off of this lunar flight of 12:49 PM EDT. The three crewmembers in the spacecraft quite busy at this time. Astronaut Tom Stafford, the commander, starting a rather extensive check of the Emergency Detection System, working with both members of the launch vehicle and spacecraft checkout crew. The ground based master computer here in the Firing Room plays a rather key role also in the Emergency Detection Test. This is the final check of the overall system that does alert the astronauts in flight of any problems below them during the mission. Also in progress, we’re establishing the atmosphere in the spacecraft cabin. This is from a ground source establishing an atmosphere of 60 per cent oxygen and 40 per cent nitrogen. The astronauts, however, of course, are breathing pure oxygen through the suit circuit coming through their suits. Our countdown still proceeding satisfactorily. Weather conditions also are Go for launch. The weather forecast is for partly cloudy skies in the Kennedy Space Center area. Surface winds from the southeast, 15 knots, gusts up to 22, temperature about 82 degrees [Fahrenheit, 28° Celsius]. The sea a little rough off of Cape Kennedy but acceptable for launch attempt. The same goes for several areas in the Atlantic Ocean in possible abort recovery areas but basically around the world track all is Go as far as weather. We’re 1 hour, 54 minutes, 25 seconds and counting; this is Launch Control.

-001:46:00 PAO (King): This is Apollo Saturn Launch Control at T minus 1 hour, 46 seconds and counting, or correction, 1 hour, 46 minutes and counting. All proceeding satisfactorily at this time. Astronaut Tom Stafford still busy in the Emergency Detection System checks working with the launch vehicle crew here in Firing Room 3 and the spacecraft crew in their control rooms in the Manned Spacecraft Operations Building, some five miles from the Launch Control Center. That crew also, the spacecraft checkout crew, has made a switchlist check of their own in their control room to assure all switches on all panels are in the proper positions. Our countdown still going very well. As far as the launch vehicle is concerned, the crew here still continuing to monitor the stability of the propellants aboard the vehicle and we continue to replenish the supply of the liquid oxygen and liquid hydrogen as it boils off. The boiling off occurs because both LOX and hydrogen must be maintained at such extremely low temperatures. All still is Go with the countdown at 1 hour, 44 minutes, 55 seconds and counting; this is Launch Control.

-001:36:00 PAO (King): This is Apollo Saturn Launch Control at T minus 1 hour, 36 minutes and counting. Still proceeding well with the countdown at this time aiming toward our planned lift-off of 12:49 PM EDT. The crew at the 320-foot level at Pad B now has completed 2 major functions; the Emergency Detection Test, a check of the Emergency Detection System, and we also have also purged the cabin. The cabin atmosphere now in an environment of 60 per cent oxygen, 40 per cent nitrogen. The closeout crew now has been given a go ahead by the Spacecraft Test Conductor to proceed with putting on the Boost Protect Cover, this is the cover that goes over the hatch on the spacecraft. Our countdown still proceeding satisfactorily. Here in the Launch Control Center all still looking well with the Saturn V launch vehicle as well as the spacecraft. That anomaly we had earlier concerned with a drop in pressure in a conditioning line in the Instrument Unit has created no problem whatsoever. The temperatures still read good in the IU, in the Instrument Unit, and we are proceeding with no constraints. This is Launch Control at 1 hour, 34 minutes, 47 seconds and counting.

-001:26:00 PAO (King): This is Apollo Saturn Launch Control; one hour, 26 minutes and counting. We are proceeding with the Apollo 10 countdown at this time. The closeout crew at the 320-foot level have now essentially completed their work and they are about to secure the White Room, the arm that attaches to the spacecraft hatch itself. They begin to break up the White Room in preparations for the departure, and also preparations a little later for retracting the complete swing arm, swing arm number 9, to a standby position. We are a good bit ahead in the countdown as far as these preparations are concerned, probably in the area of some 20 minutes ago or so. We anticipate that the closeout crew will be ready to depart in about 10 minutes from this time. Spacecraft Test Conducter made another check with Houston Flight, just on a contingency basis, at this time in the countdown, to check the flight since we are on the same launch time as planned. The flight azimuth of 72 degrees is already aboard the spacecraft computer and no changes are required. This is strictly for contingency purposes in case we - the window changed or we were launching a little later than the planned lift-off time. All still going well at this time; 1 hour, 24 minutes, 42 seconds and counting. This is Launch Control.

[Any delay in the launch time would require an amendment to the launch azimuth to compensate for the rotation of the Earth in the time beyond the original scheduled launch.]

-001:16:00 PAO (King): This is Apollo/Saturn Launch Control T minus 1 hour, 16 minutes and counting. We are Go on the countdown for the Apollo 10 lunar mission at this time. Astronaut Tom Stafford, the spacecraft commander, is in the spacecraft going through some checks with the Spacecraft Test Conductor of the stabilization and control system of this spacecraft, at this time. All the propellants are aboard the three-stage Saturn V launch vehicle, and all looks well at this time. We are G at T minus 1 hour, 15 minutes, 30 seconds and counting. This is Launch Control.

-001:06:00 PAO (King): This is Apollo/Saturn Launch Control at T minus 1 hour, 6 minutes and counting. Still aiming at our planned lift-off at 12:49 pm Eastern Daylight Time. All aspects of the countdown, both with the Saturn V launch vehicle, the Apollo spacecraft, and the Lunar Module, all are Go at this time. The close-out crew, which has been up to the 320-foot level at the end of the swing arms, swing arm number 9, working with the Apollo 10 crew in the spacecraft, now is departing the area. Once the crew has left, this will permit us to go into preparations to move the swing arm away from the spacecraft hatch. We move the swing arm 12 degrees from the hatch in a parked position, where it remains until the T - 5 minute mark in the count, when it comes all the way back to its full-back position of about 60 feet. The purpose of course, is in the event of an emergency, we could bring that swing arm on back in a hurry and the astronauts would egress. They have a high-speed elevator that's locked at the 320-foot level standing by, in case of such an emergency. This elevator is operated by Jack Lousma, the capsule communicator, the astronaut capsule communicator here in the firing room. We are still Go at 1 hour, 4 minutes, 42 seconds and counting. This is Launch Control.

LUT swing arm 9

Swing arm 9

-001:00:00 PAO (King): This is Apollo/Saturn Launch Control. We are coming up on 60 minutes and counting. Mark, T minus 60 minutes and counting, T minus 60 minutes; we are proceeding at this time. The 363-foot Apollo/Saturn V space vehicle is Go as are the tracking elements, weather, all conditions ready for a launch at 12:49 pm Eastern Daylight Time. At this point in the countdown we are beginning some final telemetry checks and we are bringing up the various radio frequencies concerned with the launch vehicle. These include 2 key tracking beacons located in the Instrument Unit which give us back tracking information during the powered phase of flight. All still well with the Apollo 10 astronauts; Tom Stafford, John Young and Gene Cernan aboard the spacecraft at the 320-foot level. This is Launch Control.

-000:56:00 PAO (King): This is Apollo/Saturn Launch Control at 56 minutes and counting. 56, and we're proceeding satisfactorily. Weather conditions still Go for a launch attempt at this time. All still well with the crew in the spacecraft. We're going through some telemetry checks with the launch vehicle. We've also taken a look at that RP-1 fuel in the first stage that's been in there for a little while. We've checked its status and the status is reported back as good. We're proceeding; 55 minutes, 33 seconds and counting. We'll be prepared within a matter of minutes to bring the swing arm back from the spacecraft at the 320-foot level. This is the top swing arm, Apollo access arm, identified as swing arm number 9. It will be retracted initially to a parked position some 12 degrees from the spacecraft. This is about 5 feet. It will remain in that position until a 5-minute mark in the count when it will be brought to its complete fallback position some 60 feet from the spacecraft. Coming up on 55 minutes, this is Launch Control.

-000:50:52 PAO (King): This is Apollo Saturn Launch Control; T minus 50 minutes, 52 seconds and counting. All still going well with the countdown at this time. Here in the firing room, the launch team gearing up for two key tests at this time. One, a check of the range safety command destruct system aboard the Saturn V launch vehicle. The other, some attitude command checks to assure that the engines will swivel in response to commands from the guidance system during flight. The astronauts in the spacecraft still busy with some of their final preparations at this time, and all is proceeding satisfactorily. T minus 50 minutes, 18 seconds and counting; this is Launch Control.

-000:46:00 PAO (King): This is Apollo/Saturn Launch Control at 46 minutes and counting; T minus 46 minutes and counting. All is still proceeding very satisfactorily for the countdown of the Saturn V Apollo space vehicle. The swing arm number 9 now has been retracted to the 12-degree position. This is a position some 5 feet away from the spacecraft. Once this was accomplished, we then proceeded to arm the pyrotechnics, the busses for the pyrotechnics aboard the spacecraft, particularly the Launch Escape Tower. From here on down during the count, if an emergency was so critical that it would be necessary, the astronauts could activate that escape tower now that the swing arm has been moved away from it. The range safety command checks are still continuing at this time. All is going well. Still aiming for that planned lift-off time of 12:49 pm Eastern Daylight Time. This is Launch Control.

-000:41:00 PAO (King): This is Apollo Saturn Launch Control, T minus 41 minutes and counting. T minus 41; all going well. Little quieter from the spacecraft now; the astronauts are still busy but they are not sending back as many reports as they had up to about 10 minutes ago. The countdown still proceeding very satisfactorily at this time. Coming up in about 5 minutes will be a key test of the launch vehicle power transfer, where we will switch from external power to the flight batteries aboard the three stages; and the Instrument Unit of the Saturn V to assure themselves that they will operate properly when called on during the flight. Over the final portion of the countdown, that swing arm number 9 will come back to its fully retracted position at 5 minutes in the count. We'll go on an automatic sequencer at 3 minutes and 6 seconds in the countdown; from that point on down, all activities during these final moments of the countdown will be automatic, run by the ground base master computer here in the control center. If anything does go wrong, the computer will automatically shut down and stop the count; would go into a Hold in those conditions. Once the automatic sequence does occur, we will begin to pressurize the various tanks in the three stages of the Saturn V. We'll go to transfer to internal power with the launch vehicle at the 50-second mark, the five engines in the first stage will ignite at 8.9 seconds; we'll have all engines running at 2 seconds in the count and should get lift-off at zero. Still aiming towards a final liftoff - 12:59; correction, 12:49 pm, Eastern Daylight Time. This is Launch Control.

-000:36:00 PAO (King): This is Apollo/Saturn Launch Control at T minus 36 minutes and counting. T minus 36. All still going well with the Command Module, Service Module, Lunar Module for the flight as well as the three stages of the Saturn V launch vehicle. We are Go for the mission at this time. The following are some of the highlights that have occurred since last evening. We went into a built-in hold at 4 pm Eastern Daylight Time yesterday afternoon. Following the start of the built-in hold we did move the 9.8 million pound [Mobile] Service Structure from the pad. The [Mobile] Service Structure was moved to its fallback position which is some 17,000 feet away from pad B. Astronauts Donn Eisele and Joe Engle boarded the Apollo 10 spacecraft last evening to go through some switch list checks to assure that all would be ready for the countdown when it was picked up today. We picked up our countdown at T minus 9 hours and counting at 2:49 am Eastern Daylight Time this morning. We were a little late starting our propellant loading because of some minor problems at the launch pad concerned with ground support equipment. However, we then did proceed into our propellant load and loaded a little more than three quarters of a million gallons of liquid oxygen and liquid hydrogen aboard the vehicle. We were then ready by the time we resumed our countdown at 3 hours and 30 minutes to have a full propellant supply aboard. The Apollo 10 astronauts Tom Stafford, John Young and Gene Cernan were awakened this morning with Stafford and Young being awakened at 7:34 AM. Their teammate Gene Cernan got up a little earlier. He was awakened at 6:50 AM. They had breakfast with some 10 of their colleagues, donned their suits, and then came to the pad. They were declared physically fit during their brief examination by Dr. John Teegen and Dr. Alan Harter before coming to the launch pad. The breakfast menu included the normal astronaut fare of steak and eggs, coffee, orange juice. The crew came aboard the spacecraft with the Commander first at 10:06 AM. He was followed by the Lunar Module Pilot Gene Cernan, who sits in the right-hand seat, at 10:11 am; and finally John Young, the man in the middle seat, the Command Module Pilot, at 10:16. Since the crew has come aboard we've really been ahead in the countdown. Since that time, all has gone well. We're proceeding at this time. We have just satisfactorily completed our power transfer with the launch vehicle. Tom Stafford aboard the spacecraft giving some readouts back to Test Conductor Skip Chauvin at this time. All aspects of the mission, including weather, Go as we approach the 33-minute mark in the count. Now 33 minutes, 10 seconds and counting; this is Launch Control.

-000:30:40 PAO (King): This is Apollo/Saturn Launch Control; T-30 minutes, 40 seconds and counting. We are proceeding at this time and aiming for a planned lift-off 49 minutes after the hour. Coming up shortly, the Apollo 10 Lunar Module will go on internal power. This is on power of 2 batteries in the ascent stage and 4 batteries in the descent stage. Most of the preparation work in the Lunar Module had been taken care of before we got into the final count, but it will go internal shortly. For a status report on operations at the Mission Control Center we will now switch to Houston.

PAO (King): This is Mission Control, Houston. The prime team of flight controllers, headed by Glynn Lunney, is on station prepared to support this mission. The Manned Space Flight Network reports it is green, ready to support the mission. One minor problem with the telemetry computer at Carnarvon, but it will not hold the mission up, there is a backup computer there. Recovery forces report all on station. Among those in the viewing room here in the Control Center are Senator and Mrs. Barry Goldwater. We have three astronauts at the CapCom console; Charlie Duke, Bruce McCandless, and the backup spacecraft Commander for Apollo 10, Gordon Cooper. Taped to the CapCom console are 2 dolls, one Charlie Brown, one Snoopy, replete with spacesuit. This is Mission Control, Houston.

-000:26:00 PAO (King): This is Apollo Saturn Launch Control; T minus 26 minutes and counting. All aspects of the countdown for the Apollo 10 lunar mission are Go at this time. At this point in the count, the astronauts in the spacecraft have completed the pressurization of the Reaction Control System for the Service Module. These are those four thrusters, those four quad thrusters around the Service Module, 100-pound thrust each, which they use for maneuvers once the astronauts have separated from the launch vehicle and are on their way to the Moon. In addition to this, Astronaut Tom Stafford is getting a new setting for his altimeter in the spacecraft; he uses this to change different abort modes during the powered phase of flight. The new settings given to him from Houston Flight by the Spacecraft Test Conducter here. Vice President Agnew has arrived at the control center; he has been here for some 25 minutes at this time, and he is viewing the operations from a room adjacent to firing room 3, from where the overall countdown is being handled. We are 24 minutes, 53 seconds and counting; this is Launch Control.

-000:21:00 PAO (King): This is Apollo/Saturn Launch Control at 21 minutes and counting. All still going well, aiming for our planned lift-off at 49 minutes past the hour. We are making some final checks of the second stage of the Saturn V launch vehicle. At this time starting a chill-down sequence in which we introduce cold helium into the engine chamber, the five engines in the second stage, to condition it for later, during the powered flight, when that extremely cold hydrogen and oxygen meet in the engine chamber. We condition them for these extremely low temperatures over the final portions of the countdown itself. As a matter of interest, the target of the Apollo astronauts, the moon, at launch time will be a distance of 218,528 miles, 218,528 nautical miles. We are coming up on T minus 20 minutes and counting. All aspects of the mission Go. This is Launch Control.

-000:16:00 PAO (King): This is Apollo/Saturn Launch Control; T minus 16 minutes and counting, T minus 16. We are proceeding satisfactorily. Astronaut Tom Stafford in the Apollo 10 spacecraft had completed some final checks of the spacecraft Stabilization and Control System. Coming up in the next minute will be a series of busy checks on the part of the astronauts aboard the spacecraft. They will update the spacecraft computer with some central timing feeds from Houston. The spacecraft will go on full internal power. Of course, the fuel cells for power for the spacecraft have been upped, but an external source has been sharing the load. This external source will be removed and will be on full fuel cell power at the 15-minute mark. The astronauts also will switch their Emergency Detection System equipment to the automatic mode for abort purposes during the flight. The rotational hand controllers both for Tom Stafford and John Young will be armed. 15 minutes and counting; this is Launch Control.

-000:11:00 PAO (King): This is Apollo/Saturn Launch Control; T minus 11 minutes and counting, T minus 11. All aspects are still going well at this time. The astronauts aboard the spacecraft have completed some special communication checks on what we call the astro-comm circuit. It's a special circuit which has the Launch Operations Manager, the Spacecraft Test Conductor, and Astronaut Jack Lousma who has the call sign Stoney, the capsule communicator here in the firing room. This is special communications which can be used particularly for abort contingencies. These are the only people on the circuit and they have performed their final communications checks. In about 5 minutes, we will go on the circuit and keep it up at that time. Mission Control Center in Houston also coming in shortly with some communications checks. All aspects going well, we are proceeding, all aspects of the mission Go. Coming up on the 10-minute mark in the count. This is Launch Control.

-000:06:43 PAO (King): This is Apollo/Saturn Launch Control at T minus 6 minutes, 43 seconds and counting. Spacecraft Test Conductor Skip Chauvin has just completed Apollo status check of all personnel involved in the spacecraft countdown. He received 'Go' from all participating. Three particularly strong ones from the three astronauts aboard the Apollo 10 spacecraft. The countdown still proceeding very satisfactorily at this time. We'll have final Go/No-Go checks from Launch Director, Houston Flight and Mission Director coming up in about a minute or so. The weather is Go and the complete Saturn V launch vehicle to include the spacecraft and Lunar Module appears to be ready for a launch 49 minutes after the hour for this, the Apollo 10 lunar mission. We've now hit the 6-minute mark. All aspects of the mission Go. This is Launch Control.

-000:04:30 PAO (King): This is Apollo Saturn Launch Control; T minus 4 minutes, 30 seconds and counting. The Apollo access swing arm number 9 now fully retracted to its fallback position, some 60 feet away from the spacecraft. At lift-off we will still have some five swing arms still attached; they will move back automatically at first motion, some three-quarters of an inch after the vehicle takes off. Astronaut Tom Stafford has completed his checks with the Spacecraft Conducter. The Mission Director George Hage and the Launch Director Rocco Petrone have given a Go for the flight as has the Range. We have now passed the 4-minute mark and proceeding satisfactorily; we are Go; this is Launch Control. We have just passed the 3 minute mark; we've had the firing command; that's the signal that the automatic sequence is now in, and the remainder of the count will he handled by the Master Computer here in the firing room as various events click off leading up to the ignition of the five engines in the first stage of the Saturn V at the - with lift-off at the zero mark in the count. The actual ignition of those five engines will come at 8.9 seconds in the count. We'll have a report of all engines running at the 2-second mark, and at that time, and over the next few seconds, those engines will be specially checked to assure that we have proper thrust. Once that occurs we will get Commit, meaning that the hold-down arms can release and we will get lift-off of the Saturn V launch vehicle atop 7½ million pounds of thrust. We are now coming up toward the 2-minute mark in the count; at this point the tanks in the vehicle pressurizing; 2 minutes and counting. Our status board indicates here in the control room that all aspects involved are ready. Tom Stafford has just reported back that they want to thank everybody for all the help. We are now at T minus 1 minute, 45 seconds and counting.

[MP3 Audio of PAO (with recording breaks).]

[MP3 Audio of air-ground, no PAO (and no recording breaks).]

PAO (King): We'll go on internal power with the launch vehicle at the 50-second mark. At 17 seconds in the count, the guidance system goes internal - this is guidance reference release.

[At T minus 17.3 seconds, the Saturn V's inertial guidance platform in the IU is released from the systems which have up to now been holding it in the correct orientation for the flight. This also represents the start of timebase 0.]

PAO (King): We already have the proper flight azimuth in, now 90 seconds and counting. Now 90 and counting. The astronauts have turned off their ground communication at this time however they are on VHF, and of course the S-band circuits, as well as the special astronaut communication circuit. One minute, 12 seconds and counting. The vehicle tanks beginning to pressurize at this time; our status board indicates the first stage tanks are now pressurized. We're coming up on the 60-second mark; 60 seconds and counting; we are Go for a mission to the Moon at this time. The second stage now pressurizing and we are coming up on power transfer. Fifty seconds and counting, we have now switched to internal power satisfactorily on the batteries of the first stage, all three stages of the Saturn V vehicle. Forty seconds and counting, Tom Stafford making a final check of his computer. The vehicle, all stages pressurized at this time. We are waiting for the swing arms to come back. One should be coming back at this time, the second one at 17 seconds. Tom Stafford reports they are Go. We are coming up on the 20-second mark. T minus 20 seconds and counting. Guidance internal. 15, 14, 13, 12, 11, 10, 9, we have ignition sequence start, engines on, 5, 4, 3, 2, all engines running, launch commit, lift-off. We have lift-off, 49 minutes past the hour.

[Photograph S69-35107HR shows the Apollo 10 space vehicle just after lift-off.]

000:00:00 CapCom: 10, 9, 8, 7, 6, 5, 4 - Ignition - 3, 2, 0.

[Start of timebase 1.]

000:00:01 CapCom: Lift-off.

000:00:02 Stafford: We have a lift-off.

000:00:03 CapCom: Roger. Lift-off.

000:00:05 Stafford: Yaw - yaw maneuver.

000:00:07 CapCom: Roger.

000:00:08 Stafford: Clock is started.

PAO: Stafford reports the clock has started. The tower is clear.

000:00:09 CapCom: Roger.

[Photograph KSC-69PC-170HR shows Apollo 10 just as it clears the LUT.]

000:00:11 Stafford: And the...

000:00:13 Duke: ...are off.

000:00:14 Stafford: Roger.

000:00:15 Cernan: We're going!

000:00:16 Stafford: And, roll program right on time.

[Stafford is reporting that the IU has commanded the intiation of the maneuver to roll the complete space vehicle onto the desired launch azimuth. Both launch pads at LC-39 are aligned with the flame trench running due north-south. This therefore means that at launch, the vehicle's frame of attitude reference is in an azimuth that is 90° east of north. The roll maneuver will adjust this to the desired azimuth of 72.028° east of north.]

000:00:17 Duke: Roger, Tom.

000:00:19 Stafford: She's looking good, Charlie.

000:00:20 Duke: Beautiful.

PAO: Tom Stafford acknowledges the roll and pitch program to put Apollo 10 on the proper course.

[The Public Affairs Officer commentary has now transferred to Houston.]

000:00:26 Stafford: Okay. Pitch is tracking. Looking good.

000:00:29 Duke: Roger.

000:00:34 Stafford: Roll complete. ELS Manual.

[ELS is the Earth Landing System, the system of parachutes and their deployment systems that bring the CM to a safe splashdown in the sea.]

000:00:36 Duke: Roger. Roll.

000:00:41 Duke: 10, Houston. Mark. Mode 1 Bravo.

[The initial 42 seconds, to an altitude of about 10,000 feet, are flown in abort Mode 1A (one alpha). If an abort situation occurs within this time period, the CM would rapidly separate from the SM using the Launch Escape Tower (LET), the solid-fuelled rocket mounted on top of the CM, which would carry it up from the malfunctioning launch vehicle. A small 'pitch control' motor at the top of the LET would pitch the LET/CM assembly east out over the Atlantic Ocean and away from the booster below which will likely be breaking up and possibly exploding. The tower stays attached for 14 seconds after the initiation of the abort. The highly dangerous hypergolic propellants of the Command Module's RCS would quickly and automatically be dumped overboard as they would be harmful to the recovery forces. The CM would then follow a standard descent on parachutes to a normal splashdown.]

[Abort Mode 1B (one bravo) extends from 42 seconds into the flight to an altitude of 16.5 nautical miles. With the space vehicle now being further downrange and tilted over, the pitch control motor on the LET, would not be required in the event of a 1B abort. A pair of canards would be deployed automatically to force the LET/CM combination into an attitude where the base of the CM is facing the direction of travel, ready for the safe deployment of the drogue and main parachutes. While the canards have little effect in a low altitude abort, they become increasingly important as the Saturn V gains speed through the 1B mode.]

000:00:44 Stafford: Roger. One Bravo.

PAO: One bravo is a - an abort mode dealing with altitude, function of altitude.

000:00:52 Stafford: Starting to rattle a little bit in here.

000:00:54 Duke: Roger.

000:00:55 PAO: Plus 55 seconds.

000:00:56 Stafford: Cabin is relieving.

000:00:58 Cernan: Cabin is relieving.

000:01:01 Duke: Roger. Copy.

PAO: Cabin pressure is relieving. Downrange 1 mile, 3.3 nautical miles high.

[Photograph KSC-69PC-188HR shows Apollo 10 during S-IC powered flight.]

000:01:05 Stafford: 2 gs, Charlie.

000:01:07 Duke: Roger. Looking good at 1 minute.

000:01:18 Cernan: What a ride, Babe, what a ride!

000:01:20 Duke: Roger. You're looking good, 10; you're looking real good.

PAO: That's Gene Stafford - Cernan reporting, "what a ride"

000:01:26 Stafford: Roger. Going through Max Q.

000:01:30 Duke: Roger.

000:01:35 Duke: 10, you're through the Max Q. You're looking good.

000:01:39 Stafford: Two and a quarter g's. She's looking beautiful.

000:01:44 PAO: One minute, 44 seconds downrange, 7, 12 miles high.

000:01:51 Stafford: Okay. Two and a half g's.

000:01:53 Duke: Roger. Copy, Tom.

000:01:58 Duke: Okay. And, Mark. Mode 1 Charlie. You're looking great.

[Mode 1C is used for aborts occurring between 16.5 nautical miles and the jettison of the tower. As the air is now very thin, the airflow over the pair of canards at the top of the tower would have little aerodynamic effect during an abort. Instead, the tower and Boost Protective Cover are jettisoned and the CM RCS used to control the orientation of the spacecraft]

000:02:01 Stafford: Roger. One Charlie and 3 gs; it feels great.

Ascent acceleration profile

Launch acceleration profile

000:02:06 Duke: You're Go for staging, 10.

000:02:08 Stafford: Roger. 10 is GO.

[John Young from the 1969 Technical Debrief: - mentioned that he had been warned that they may have trouble reaching the EDS switch whilst being subjected to 3 to 4 g. However no problem was encountered.]

000:02:16 Stafford: Inboard shutdown.

[Start of timebase 2.]

000:02:19 Duke: Roger. Inboard.

PAO: Inboard engines are out.

000:02:24 Stafford: They're a little Pogo. Pogo damps.

000:02:26 Duke: Roger. Copy, Tom. EDS Off, 10,

PAO: Charlie Duke asking the crew to turn off their Emergency Detection System.

000:02:47 Stafford: Got staging lights out.

[Tom Stafford from the 1969 Technical Debrief - mentioned that they thought they would encounter a single pulse of negative G at staging as the S-IC cutoff and the crew would be thrown forward in their straps, before the S-II ignited and recommenced the acceleration. However they actually encountered was a form of pogo which continued for 4 cycles, during which they were "slammed forward, back, forward, back, forward and back" (direct quotation) and the instrument panel appeared blurred during this time.]

[Start of timebase 3.]

000:02:51 Duke: Roger.

PAO: Good ignition on the second stage.

[MP3 Audio of PAO (with recording breaks).]

[MP3 Audio of air-ground, no PAO (and no recording breaks).]

000:02:54 Stafford: And it looks like we got a good S-II...

000:02:57 Duke: Roger [Garble] 10, on the S-II. It's looking good. Confirm EDS [Emergency Detection System] Off.

000:03:05 Stafford: EDS is Off [Garble.]

000:03:07 Duke: Roger.

000:03:16 Stafford: Plane Sep.

[The interstage ring or skirt has been jettisoned.]

[Staging of the S-IC and S-II is technically described as a "dual plane separation", as the vehicle is cut across two geometrical planes. The first plane is between the skirt and the S-IC, with the S-II engines starting 1.1 seconds later. The second plane separation, when the second stage loses the skirt, occurs at 3 minutes, 10.7 seconds; 30.0 seconds after the S-IC separation. This time allows the S-II's attitude to stabilise because if either part of the launch vehicle were to be yawing or pitching excessively, there would be a danger of the engine bells striking the S-IC and skirt as the two great metal cylinders coast along before ignition of the S-II. The skirt provides clearance above the first stage's LOX tank for the five J-2 engines of the S-II stage.]

000:03:16 Duke: Roger.

000:03:18 Stafford: There goes the tower.

[A single, small, solid-propellant motor near the top of the LET fires for one second, jettisoning the entire LES (Launch Escape System) and the checklist moves to abort mode II.]

[The LES consists of the tower, with all its rocket motors, instrumentation and canards; and the BPC (Boost Protective Cover), which is a shroud over the entire Command Module. The BPC protects the spacecraft from the heat generated by the friction of ascent, and from the exhaust of the Launch Escape Motor should the tower be used for an abort.]

LES

Click on above image to enlarge

[John Young from the 1969 Technical Debrief - "Just - prior to tower jett, I could see - the only way I can describe it is - aerodynamic heating smoke coming across the hatch window and also the right-hand window underneath the BPC before it was jettisoned. There was no question about it. It was coming between the window and the BPC and it was aerodynamic heating. I could see it on both my right window and on the hatch window".]

000:03:20 Duke: Roger, on the tower. And we confirm second plane Sep.

000:03:22 Stafford: Okay

PAO: Flight Dynamics reports trajectory Go at 3 minutes, 9 seconds. Downrange, 81 miles. 46 miles high. Second plane separation, that is the skirt around the engines on the second stage. And the Launch Escape Tower has jettisoned.

000:03:25 Stafford: Man, that staging was quite a sequence!

000:03:27 Duke: Roger. Sounded like it.

000:03:30 Stafford: And we have guidance Initiate.

[Up to now, the IU has been steering the vehicle according to a predetermined trajectory which minimises sideways movements though the air while tilting it along its flight azimuth. It has not been using any information about its position and velocity to alter its flight path. The control is open loop. 'Guidance initiate' marks the point where the IU begins the IGM (Iterative Guidance Mode). The control loop is now closed as the IU begins using position and velocity data to help it guide the vehicle to where it wants to get to - an accurate Earth orbit.]

[Eugene Cernan from the 1969 Technical Debrief - "I saw the pitch guidance change about three times, where the horizon went on the bottom of my window and went to the top of my window. And then went to the bottom of my window and then went to the top of my window. It seem to me it was more than hunting, but Tom then verified that the guidance was good and what was happening. Then it had pitched back. It wasn't hunting as in Gemini where you could see the nose hunt. This was definitely a pitch change".]

000:03:31 Duke: We confirm that, 10.

000:03:33 Stafford: Roger.

000:03:35 Duke: The S-II is looking beautiful, Tom. Everything is copacetic.

000:03:37 Stafford: Roger. It looks good to be back up here, Charlie.

000:03:44 Duke: Yes, I bet.

PAO: That's Charlie Duke talking to Tom Stafford.

000:03:45 Young: Just like old times! It's beautiful out there!

000:03:46 Duke: Not bad.

000:03:51 Duke: You guys sound ecstatic.

000:03:55 Stafford: Man, this is the greatest, Charlie.

000:03:57 Cernan: Charlie, babe. It's fantastic, babe, really!

PAO: That's Gene Cernan with fantastic.

000:04:01 Stafford: Okay. Four minutes - -

000:04:01 Duke: Roger. Four minutes. You're Go. Your trajectory and guidance look good.

000:04:07 Stafford: Roger. We look on the line on board.

PAO: 171 miles downrange, 67 miles high at 4 minutes, 15 seconds. Still Go.

PAO: Glynn Lunney taking a status check. Everyone says Go. Four minutes, 50 seconds; 230 miles downrange, 67 miles high.

000:05:01 Duke: 10, Houston. At 5 minutes, you're all Go. All your systems are looking great.

000:05:05 Stafford: Roger. Five minutes, and 10 is GO.

000:05:07 Duke: Roger. You're right on the track.

000:05:09 Stafford: Roger, Charlie.

000:05:58 Duke: 10, Houston. Coming up on 6 minutes. You're looking beautiful.

PAO: We have an estimate of inboard engine cut-off on the second stage at 8 minutes, 15 seconds. Outboard engine cut-off; 9 minutes, 11 seconds. Five minutes, 30 seconds; 299 miles downrange, 83 miles high. All controllers reporting Go. 350 miles downrange, 87 miles high now.

[The SPS gimbal motors are powered up at this time to provide SPS control if needed in an abort. The crew select each of the four gimbal motors On, in the order Pitch 1, Yaw 1, Pitch 2, Yaw 2. Once this procedure is complete, they select the Launch Vehicle/SPS Gimbal Position Indicator (GPI) switch on Panel 1 to GPI which allows them to monitor the position of the SPS gimbals. Up until now, the GPI has been monitoring the Saturn V's propellant tank pressures - another dual use gauge. The GPI scales are in degrees, about a zero midpoint.]

Panel 1

SPS Gimbal motors P1

Click the above for full panel diagram.

[The SPS gimbal motors are each selected On at intervals of at least one second to avoid power surges.]

000:06:01 Stafford: Six minutes. Gimbal motors coming On. Pitch 1.

000:06:03 Cernan: That's Go.

000:06:04 Stafford: Yaw 1.

000:06:05 Cernan: That's Go.

000:06:06 Stafford: Pitch 2.

000:06:07 Cernan: That's Go.

000:06:08 Stafford: Yaw 2.

000:06:09 Cernan: You got them all, Tom.

000:06:11 Stafford: Looks good here.

000:06:25 Cernan: Charlie, are you sure we didn't lose Snoopy on that staging?

PAO: Guidance says it's looking real good. Ira's 6 minutes, 23 seconds.

000:06:28 Duke: No, I think Snoopy is still there with you. You're looking good. We copy your gimbal motors On and your trim looks good.

000:06:34 Stafford: ... tracking ... beautiful.

000:06:44 Duke: 10, Houston.

000:06:45 Duke: Mark.

000:06:46 Duke: S-IVB to orbit capability.

[The S-IVB is now capable of placing itself plus the CSM and LM into a safe low earth orbit if problems are encountered with the S-II that require immediate staging. If this abort mode had to be employed the S-IVB would not have sufficient propellant remaining to perform a TLI burn. An alternative mission profile would have to be adopted.]

PAO: Apollo 10 now has the capability to get into orbit on the S-IVB should the second stage malfunction.

000:06:47 Stafford: ...

000:06:55 Duke: 10, Houston. Coming up on 7 minutes. You are all Go. We have nominal level sense arm, 8 plus 15. S-II cut-off, 9 plus 11.

[One of the procedures devised to ensure the maximum amount of S-II propellant was consumed prior to the outboard engine cut-off was to use five sensors in each tank to detect when the propellant was nearing depletion. Engine shut down was commanded when at least two of these sensors had detected propellant depletion. To ensure that these sensors did not command a premature engine shut down they are not armed until another independent propellant gauging system had indicated that the tanks were getting close to depletion.]

000:07:03 Stafford: You have the level sense arm, and 9 plus 11 is the S-II.

000:07:07 Duke: Rog.

PAO: Seven minutes, 14 seconds. Downrange now 538 miles and 94½ nautical miles high. Coming up on inboard engine cut-off.

000:07:31 Stafford: 7:30. 10 is good.

000:07:33 Duke: Roger. Looking good here.

000:07:41 Stafford: Inboard's shut down.

[The inboard J-2 engine is shut down early to minimise its tendency to induce low frequency pogo oscillations. This inboard engine shutdown reduced total vehicle thrust by 234,714 lbf to a level of 922,553 lbf.]

000:07:43 Duke: Roger on the inboard's, Tom. We confirm it.

000:07:49 Duke: How's the ride?

000:08:00 Duke: 10, Houston. Eight minutes. You're looking good. How's the ride?

000:08:04 Stafford: Roger. Fantastic, Charlie, fantastic.

000:08:06 Duke: Roger.

000:08:26 Duke: 10, Houston -

000:08:27 Duke: MARK-

000:08:28 Duke: - the level sense arm - -

[Duke is informing the crew that the "level sense arm" signal has been sent to the IU. The engines will be shut down once two probes in one of the tanks have been uncovered by the dwindling propellant. They can expect shutdown shortly.]

000:08:29 Stafford: The level sense arm.

PAO: We are right down the ground track at 8 minutes, 30 seconds. 755 miles downrange, 98 miles high, velocity is 21,499 feet per second. Flight Director is taking a status for staging now.

000:09:01 Stafford: ... everything looks good.

000:09:04 Duke: Roger, Apollo 10. You are Go for staging.

000:09:09 Duke: Mark. Mode IV, Apollo 10. Mode IV.

[Mode IV is the abort mode where the crew have been given a Go decision to continue to orbit using the S-IVB, and should that stage deviate from its allowed limits, the CSM will separate from the Saturn and use the SPS (Service Propulsion System) to continue into Earth orbit.]

000:09:13 Stafford: Through mode Sep IV. Staging.

[Start of timebase 4.]

000:09:14 Duke: Roger.

000:09:17 Stafford: Separation.

000:09:18 Duke: Roger.

000:09:19 Stafford: Appears we got good ignition.

000:09:21 Duke: Roger.

000:09:24 Young (onboard): Yes, it did go out. I think 1 all the way out.

000:09:26 Duke: We confirm your guidance, and your S-IVB looks good, 10.

000:09:29 Stafford: Roger.

PAO: Thrust is good and guidance has initiated on the S-IVB stage, the third stage.

[Just as with the second stage, the third stage is operating the with the same 'Iterative Guidance Mode' where the vehicle is actively steering towards orbit insertion.]

000:09:32 Cernan: Charlie, lots of stuff out the window in staging. We're catching up and passing it now.

000:09:36 Duke: Okay.

000:09:39 Stafford: Okay. Guidance looks right on with the onboard jet, Charlie.

000:09:42 Duke: Roger. We confirm that. Looking great here. You're looking beautiful.

000:09:43 Stafford: Roger.

PAO: 1,037 miles downrange and 102 miles high, and the velocity is 23,400 feet per second.

000:09:46 Young (onboard): Okay. We've got an eighth of a g, old buddy.

000:09:47 Cernan (onboard): (Cough)

000:09:48 Stafford (onboard): An eighth of a g ...

000:09:50 Cernan (onboard): Look at how fast those clouds are.

000:09:53 Young (onboard): ... at 149 ...

000:10:02 Duke: 10, Houston. At 10 minutes you're GO.

000:10:04 Stafford: At 10 minutes, Go. Onboard's good.

000:10:06 Duke: Roger.

000:10:06 Cernan (onboard): Tom, we got everything here so far.

000:10:08 Young (onboard): ... in a 102 .... right on out.

PAO: Predicted cut-off for the Saturn S-IVB stage 11 minutes 47 seconds.

000:10:13 Stafford (onboard): I just can't get over the vibrations ...

000:10:17 Cernan (onboard): Yes, after that first-stage staging, man, it - -

000:10:21 Duke: Apollo 10, Houston. Predicted S-IVB cut-off, 11 plus 47.

000:10:26 Stafford: 11 plus 47.

000:10:28 Young (onboard): ... Come on, baby; keep going ... Right on the line.

PAO: Downrange 1,200 miles now at 10 minutes, 44 seconds, 102½ miles high. The velocity at 24,280 feet per second.

000:10:49 Stafford (onboard): ... and ready to go.

000:10:51 Young (onboard): ... Right on the line, now.

000:10:54 Stafford (onboard): ...

000:10:59 Cernan (onboard): Isn't that something?

000:11:01 Young (onboard): Now, ...

000:11:02 Stafford: 11 minutes, and ...

000:11:03 Duke: ... 10, you're looking ...

000:11:03 Stafford: ... 10 looks good.

000:11:05 Duke: Roger, 10.

000:11:06 Stafford: ...

000:11:08 Stafford (onboard): Sure is right on the line ...

000:11:10 Duke: 10, Houston. At 11:10, you're looking good.

000:11:13 Stafford: Roger, Charlie. The guidance is beautiful.

000:11:15 Duke: Roger.

PAO: Predicted cut-off now 11 minutes, 45 seconds.

000:11:24 Young (onboard): How'd you like that?

000:11:45 Stafford: SECO!

[Start of timebase 5.]

000:11:46 Duke: Roger. SECO.

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