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Apollo 8

Day 1: Launch and Ascent to Earth Orbit

Corrected Transcript and Commentary Copyright © 2002-2011 by W. David Woods and Frank O'Brien. All rights reserved.
Last updated 2011-08-24
[This pioneering mission of Apollo 8 is using a Saturn V launch vehicle known within the Manned Space Center (MSC, now the Johnson Space Center) as AS-503, signifying that it is the third flight of the Five series rocket. In a piece of inter-centre rivalry, the Marshall Space Flight Center (MSFC) insisted on designating it SA-503, giving prominence to the Saturn rocket they had been responsible for, and they kept this up right through the Apollo program.]

[Before adopting its final mission plan, this vehicle's fate went through a number of changes as NASA managers juggled their organisation's experience, resources and available time to keep the United States within John F. Kennedy's deadline of landing a man on the Moon within the decade of the nineteen sixties.]

[The necessary flights to lead up to the lunar landing were labelled each according to its objectives, from A to G. No mission would be attempted until the objectives of the previous had been accomplished. The A mission had been flown twice, Apollo 4 and 6, which tested the Command Service Module (CSM) unmanned in Earth orbit, and which showed that the Saturn V could also be trusted to carry humans. Apollo 5, an unmanned test of the Lunar Module (LM, pronounced "lem"), was a B mission. In October 1968, Wally Schirra's crew had performed a perfect C mission as Apollo 7, giving the CSM a full work-out in Earth orbit. The D mission would test the CSM/LM combination in low-Earth orbit, E would do the same in high-Earth orbit and F would take this scenario right out to the Moon, essentially as a dress rehearsal of the Moon landing. The landing itself would be the G mission.]

[A year prior to this flight, when the S-II second stage of the AS-503 rocket first arrived at Kennedy Space Centre, managers had intended it for a third unmanned test of the Saturn V carrying a crude (or boilerplate) version of the spacecraft. By the end of April 1968, managers felt they understood the Saturn V well enough after its two flights. A decision was made to fly a crew on CSM 103 using this vehicle along with the first flight-capable Lunar Module, LM-3. This would be the first test of the complete Apollo system in space and was the D mission. To support this decision, the S-II stage needed to be man-rated; in other words, managers wanted further assurance on the stage's structural integrity. The stages of the launch vehicle were taken down and the S-II sent to the Mississippi Test Facility for two months during the summer while further pressure testing of its tanks was carried out.]

[Towards late summer, it was becoming clear that LM-3 would not be ready for flight. In a drive to reduce the weight of the lander, Grumman Aerospace was resorting to some exotic manufacturing processes and one of them, chemical milling, was making certain structural components prone to stress corrosion. Also, the use of extremely fine gauge wiring made the spacecraft's electrical systems prone to breakage. These changes, so necessary to lighten the chronically overweight spacecraft, often resulted in time consuming repairs and additional testing. George Low, manager of the Apollo Spacecraft Program Office at the Manned Spacecraft Centre, came up with an audacious idea that would allow NASA to keep to its tight schedule despite the delayed lander.]

[A famously secret plan was hatched in August, spread amongst his management team before being presented to NASA Administrator Jim Webb. In it, Low suggested swapping the D and E missions. Hold D until the LM was ready and make E into a full lunar orbit mission, but without using a LM. This was redesignated the C-prime mission and there was much to learn from it; navigation, tracking, thermal conditions, lunar orbit operations; and it helped that there would be immense propaganda value as America strove to appear pre-eminent in the space race.]

[Once the idea was hatched (and before it was presented to Webb), flight planning for the mission was also kept quiet, although hardly as secret as would be liked. Trajectory planning and flight simulations were characterized as "exercises" until the formal announcement that Apollo 8's target would be the Moon.]

[On 19 August 1968, the decision was announced - Apollo 8 was going to the Moon. LM-3 would be left behind to fly on the new D mission, Apollo 9, and in its place, a cylinder of similar mass to the LM, euphemistically called a Lunar Test Article, would provide the Saturn V with a representative load. The crew assigned to the D mission, Jim McDivitt, Rusty Schweickart and Dave Scott, would stay with it while the E mission's crew of Frank Borman, Bill Anders and Jim Lovell would leap-frog to take their spacecraft all the way to Luna.]

[By October 9, 1968, the AS-503 vehicle had once again been stacked alongside LUT-1 (Launch Umbilical Tower) on its massive transportable platform and could be carried out to Pad A of Launch Complex 39 at Kennedy Space Center. NASA had the foresight to photographically document these occasions. Frame KSC-68PC-148 is taken from the roof of the Vehicle Assembly Building (VAB) looking down on AS-503 and the tower soon after it exited through one of the structure's massive doors. KSC-68PC-147 is from the same vantage point after the huge assemblage had progressed down the crawlerway.]

[For two months, the vehicle was tested on the pad and its explosives systems (pyrotechnics) prepared for launch. Then, on December 2, the lowest of the rocket's huge propellant tanks was filled with RP-1, a refined kerosene fuel for the first stage of flight. For five days, commencing on the 5th, staff at KSC put the vehicle through a 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. While 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 removed and the vehicle finally prepared for launch.]

[Now the actual launch countdown commences on December 15 at 19:00 Eastern Standard Time (EST) with the clock beginning at T minus 103 hours. At 48 hours prior to launch, oxygen and hydrogen are fed from tanks in the Service Module to the spacecraft's fuel cells so they can begin sharing the spacecraft's electrical load with the ground supply.]

[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. For example, at one point it is discovered that the current supplied by the fuel cells is dropping. The two tankfuls of LOX in the spacecraft's Service Module are contaminated with nitrogen and for proper function of the fuel cells, purity is important. The LOX is replaced before T minus 10 hours but the tasks in the time line that were delayed by this can use the 6-hour hold at the T minus 9-hour mark to get back into line with the rest of the count.]

[At T minus 8 hours, ground crews begin loading all three stages of the vehicle with LOX. 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 on TV coverage of the event. The boil-off is such that of the 2,120,000 litres of LOX used to fill the tanks, nearly a quarter is lost by the time of launch, leaving 1,630,000 litres onboard.]

[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 8'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 begins 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.]

[With the loading of the Saturn V's propellants complete, the crew can enter the spacecraft. The following two images are taken from Kipp Teague's Apollo Archive website. PAO image KSC-68P-614 shows the crew heading from the suiting-up room to catch a van that will take them to Pad A. Image KSC-68PC-338 is taken in the White Room next to the spacecraft and Bill Anders is getting a hug from a member of the pad team before entering the Command Module. In the background and to the left can be seen the outer hatch that is really part of the Boost Protective Cover.]

[For the unfamiliar, the internal geography of the Apollo Command Module at this point can be thought of as being like an aircraft stood on its tail. The hatch would be then thought of as being in the roof with the crew entering feet first and lying on their backs. Once in their couches the crew have a monster instrument panel laid out in front of them and tiny windows in their eye line and to the side.]

Main Display Console

Command Module Main Display Console from Apollo Operations Handbook Block II Spacecraft (October 15, 1969). This console comprises panels 1, 2 and 3, and is very similar to the console in the Apollo 8 Command Module. This and other diagrams of the Apollo spacecraft are available from the Diagram page of the NASA History Website

[As with all aircraft that have side by side seating, the Commander (CDR) has the left seat and he enters first. For Colonel Frank Borman, this will be his second space flight, having already commanded Gemini VII in December 1965. From this position, he can monitor the progress of the flight from instruments in front of him while using the flight controls. Most importantly during a launch, he will have one hand on the abort handle. The second man in the spacecraft goes to the right seat. This is Major William A. Anders' first, and ultimately his only space flight. His title is Lunar Module Pilot (LMP) but this is a flight without a Lunar Module so he will share the running of the spacecraft with his two crewmates. From this seat, he will monitor the spacecraft's environmental and electrical systems. Finally, into the centre couch goes the Command Module Pilot (CMP), Captain James A. Lovell. Prior to the flight of Apollo 8, Jim is America's most experienced astronaut, having shared the cramped space of Gemini VII with Frank for a fortnight, and being the Command Pilot for Gemini XII with Buzz Aldrin for four days in November 1966. During the ascent from Earth, he will be facing the light panel for the caution and warning system and be able to monitors the computer's changing displays on the DSKY (Display and Keyboard, pronounced 'disky').]

[The original reasoning behind having a three-man crew for Apollo lay in a perceived need to have one man on watch at all times, a regime that Apollo 8 will attempt to continue. However, Frank, Jim and Bill will demonstrate the futility of this approach as they struggle to get rest while their crewmates work around them. Later, as Apollo assumed its lunar landing role, the crew was divided between a two-man crew for the Lunar Module and a pilot dedicated to the Command Module and sleep was taken simultaneously.]

Public Affairs Officer - "This is Apollo Saturn Launch Control, T minus 1 hour, 30 minutes and counting. The Boost Protective Cover [BPC] was just placed atop the hatch on the Apollo 8 spacecraft just several minutes ago, and the crew in the White Room are now securing the White Room area. They've been alerted by the Spacecraft Test Conductor to secure the area in preparation for their departure. Once the crew does depart at a designated time the swing arm that is now attached to the spacecraft with the White Room at its tip will be moved some 3 feet, actually 12 degrees, from the spacecraft and it will remain in that standby position until the T minus 5-minute [point] in the countdown when the swing arm is retracted fully to the side of the umbilical tower at the pad. The purpose here is to have the White Room standing close by. In the event an emergency condition developed which would require the astronauts to depart the spacecraft, we could bring the White Room in just from 3 feet away. It is fully retracted at the 5-minute mark in the countdown. The astronauts aboard the spacecraft [are] now participating in this test of the stabilization and control system of the Apollo 8 spacecraft. As they move their hand controllers, which would provide maneuvers in space, we're checking the performance here on the ground. All aspects of the mission still are Go, weather is satisfactory, the various tracking elements all Go at this time. T minus 1 hour, 28 minutes, 20 seconds and counting, this is Launch Control."
[The BPC covers the entire Command Module to protect it from the frictional heat of ascent through the atmosphere and from the exhaust of the rocket motors of the launch escape tower, should it be used. The BPC will be discarded with the tower once the Saturn's second stage has begun its work. Part of the BPC covers the hatch and it is this that the PAO announcer is referring to as having been put in place. It is the BPC that gives the Command Module its white appearance prior to launch. Underneath, the CM has a metallic finish from strips of metallised Mylar that cover the spacecraft for the purposes of thermal control.]
Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 1 hour, 21 minutes, 7 seconds and counting, our countdown continuing and still aiming toward the planned lift-off time at 7:51 am Eastern Standard Time. In fact, it's been going very well and some functions are actually ahead of the countdown procedures at this time. The prime crew for the Apollo 8 mission, astronauts Frank Borman, Jim Lovell, and Bill Anders are aboard the spacecraft, the hatch has been closed, and the boost protective cover has been emplaced. The close-out crew at the 320-foot level at the pad above the launch base are now securing the White Room that's attached to the spacecraft. The White Room will later be removed in the countdown. Our countdown still going satisfactorily. At this point, Spacecraft Test Conductor Dick Proffitt, participating with the astronauts in some checks of the stabilization and control system of the spacecraft itself, During this test, the astronauts actually maneuver the hand controllers aboard the spacecraft. The hand controllers are used to maneuver the spacecraft in flight. This is Launch Control."
[Launch is scheduled to happen at 07:51 on December 21 but it can be delayed somewhat, providing certain variable factors remain within limits. First, they want to be at the Moon when the lighting at Mare Tranquillitatis is at a low angle from the east. The possible landing sites are in this area and part of the mission's brief is to comment upon lighting conditions. There are only a few days each month when this is suitable. Also, they wish to launch in daylight, then have the spacecraft over a particular part of the Earth when they boost to the Moon. This further constrains the launch window to a few hours each day. Today's launch window opens 38 seconds before the planned launch and lasts 4 hours, 39 minutes.]
Public Affairs Officer - "This is Apollo Saturn launch control at T minus 1 hour, 14 minutes and counting. The closeout crew at the 320 foot level - the spacecraft level at the launch pad now has departed from the White Room and countdown is still proceeding satisfactorily at this time. In progress here in the firing room are some major tracking checks in progress at this time. These are checks working with the Air Force Eastern Test Range checking out the tracking beacons and the instrument unit of the Saturn V launch vehicle. The crew here in the firing room are also performing some telemetry checks at this time and calibrations to ensure that the read-outs that we get from the launch vehicle in flight will actually be correct ones. Our countdown has been going very satisfactorily. Now at 1 hour, 13 minutes, 6 seconds and counting on the Apollo 8 mission. Still aiming for the planned lift-off at 7:51 a.m. Eastern Standard Time on a flight direction of 72 degrees. This is Launch Control."
[The guidance and control of the Saturn V is achieved independently from the spacecraft by the Instrument Unit (IU) a one-meter ring atop the S-IVB stage. This contains its own computer, the LVDC (Launch Vehicle Digital Computer), and a gyroscopically stabilised platform, the ST-124. The platform is aligned prior to launch by rotating its X stable member with respect to a theodolite, located some distance down the crawlerway. A small window in the side of the IU allows the theodolite to view the platform. For this launch, the precise azimuth will be 72.124°.]
Public Affairs Officer - "This is Apollo Saturn Launch Control. Our countdown for the Apollo 8 mission is proceeding satisfactorily at this time. At T minus 1 hour, 4 minutes, 52 seconds and counting. Just a matter of minutes ago the spacecraft commander Frank Borman asked spacecraft test conductor Dick Proffitt 'How's the weather out there?' and Proffitt reported that the weather looks real clear at this time. Our countdown is still proceeding satisfactorily. About 10 minutes from this time we expect we will pull back the swing arm that is still attached to the Apollo 8 spacecraft at this time. This is swing arm 9 and it's the top swing arm at the pad at this time at the 320-foot level, the White Room is attached to the tip of this swing arm. When the arm is pulled back it will first be taken back to a standby position some 3 feet from the spacecraft, actually 12 degrees from the spacecraft. The arm will be fully retracted at the T minus 5-minute mark in the count. In fact while we were making this announcement the spacecraft test conductor just advised Frank Borman that the arm, in fact, would come back about 10 minutes early in the count which would be at about the 55 minute mark. Check-outs of the various tracking systems in the Saturn V launch vehicle are continuing and coming up shortly will also be some command checks from the Mission Control Center in Houston. This is the system by which Mission Control Center, Houston can send real time commands to the launch vehicle during the powered phase of flight. We check out the systems to be sure that the signals can get through. We are now at T minus 1 hour, 3 minutes, 16 seconds and counting, still aiming toward our planned lift-off time at 7:51 a.m. Eastern Standard Time. This is Launch Control."

Public Affairs Officer - "This Apollo Saturn Launch Control, T-61 minutes and counting. Our countdown so far is proceeding satisfactorily. The Spacecraft Test Conductor has just been advised that area at Pad A is now cleared and we will be pulling back the spacecraft swing arm to its parked position about 5 minutes from this time. Tracking and telemetry checks still in progress in the Firing Room, and all is going well with the Apollo 8 countdown at this time, still aiming for our planned lift-off at 7:51 a.m. Eastern Standard Time on a flight azimuth, or direction, of 72 degrees. This is Launch Control."

[Both of the launch pads at Complex 39, Kennedy Space Center, and the crawlerways that approach them, are aligned with true north. The main hatch of the spacecraft is facing due east and if the whole vehicle were to lift-off, pitch over and fly to the east, its flight azimuth would be 90°. However, the desired azimuth is 72° so after lift-off the vehicle will roll 18° to face the main hatch slightly north of east. It will then pitch over and fly along a bearing of 72°.]
Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 56 minutes, 23 seconds and counting. The spacecraft swing arm, arm number 9, now has been retracted from the Apollo 8 spacecraft. It is being placed in its standby, or park, position and will be located some 3 to 5 feet away from the spacecraft hatch. Once this is accomplished, within a matter of minutes, we will arm the 155 [thousand] pound thrust launch escape tower atop the Command Module. The swing arm has now been pulled to its standby position. It will be fully retracted at T minus 5 minutes in the count. The purpose, of course, is to have the White Room nearby in the event an emergency condition did occur that could require the astronauts to depart from the spacecraft. Once the arm is retracted, the escape tower is armed, in case of a catastrophic condition where an abort could be advised. Our countdown still proceeding satisfactorily at T minus 55 minutes, 18 seconds and counting. This is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 48 minutes and counting, T minus 48 and we have Go for the Apollo 8 countdown at this time. The crew on the spacecraft still performing some final checks. Astronaut Frank Borman, the spacecraft commander, just a few minutes ago gave a weather report of his own when he reported that the three-man crew could barely see what looked like some pink clouds out the window, Borman had earlier asked for the weather report from spacecraft test conductor Proffitt. Meanwhile here in the firing room at the Launch Control Center some three and one half miles from the launch pad, the countdown is still progressing satisfactorily here and the crew gearing up for some final checks of the range safety command destruct system. These are the destruct elements aboard the various stages of the vehicle that would destroy the vehicle in flight if required, if vehicle went off its trajectory. Of course the astronauts would be aborted from the vehicle if such an event did occur. During this period working with the Air Force Eastern Test Range tracking elements we do check out the command safety receivers to insure if such a condition were required the abort system and the destruct system would actually be able to receive the signals and accomplish the job. The countdown is still proceeding, we still aiming toward 7:51 a.m. Eastern Standard Time. This is Launch Control."

[One of the reasons America launches its space rockets from Cape Canaveral (known at the time of Apollo 8 as Cape Kennedy) is the availability of 9,000 kilometres of ocean to the east into which used stages (or the debris of a failed vehicle) could safely fall. Nevertheless, just in case a rocket should begin heading off towards populated areas, all vehicles that rise from here have explosives attached which, on command from the Range Safety Officer, would be detonated to destroy the vehicle and disperse its propellants. The three stages of the Saturn V are no exception. The signalling system for them is designed to be secure and tamper-proof. Each flight has a unique digital code which is kept secret and which must be received by the destruct electronics before they will fire. In the event they are used, they will not fire until the Command Module has been hauled clear by the Launch Escape System.]
Public Affairs Officer - "This is Apollo/Saturn Launch Control at T minus 39 minutes and counting, T minus 39, and we are Go for our countdown for the Apollo 8 mission to the Moon at this time. Just in progress, as this announcement came up, was another key milestone in our countdown preparations, the power transfer test. This is where we go from external power to the flight batteries aboard the Saturn V launch vehicle to assure that they are all working properly. Then in order to conserve these batteries we return again to external power. The final switch to internal power on the batteries occurs about the 50-second [mark] in the count. There are some 14 batteries in the Saturn V. The Apollo 8 crew of astronauts Frank Borman, Jim Lovell and Bill Anders standing by in the spacecraft as this test is in progress. T minus 38 minutes, 6 seconds and counting, this is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 31 minutes and counting, T minus 30 and our countdown proceeding satisfactorily, still aiming our planned lift-off time of 7:51 a.m. Eastern Standard Time. The Apollo 8 crew, astronauts Frank Borman, Jim Lovell, and Bill Anders standing by in their spacecraft, 320 feet above the launcher base at Pad A, Complex 39 here at the Kennedy Space Center. The astronauts are standing by for another major function that will be coming up shortly and that is pressurization of the propellant for the engines they will use in space. These are thrusters, so-called quad thrusters - there are 16 of them, located on the Service Module portion of the spacecraft. These are the thrusters that enable them to maneuver in space. We appear to have had a successful power transfer test with the launch vehicle, in which we went to internal power on the flight batteries, but then we returned to external power in order to conserve those batteries. Just a moment ago, astronaut Frank Borman asked his Spacecraft Test Conductor how the launch vehicle was doing and the report that came back was the launch vehicle is doing fine. The overall countdown doing fine at this time. We are Go for weather, all the tracking elements ready, as well as the launch vehicle and spacecraft, here at Pad 39. This is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 26 minutes and counting. We are proceeding at this time. In progress at this time, we are pressurizing the propellant for the spacecraft engine systems that would be used in a space environment. Astronaut Jim Lovell, the man who sits in the middle seat and who is the Command Module Pilot, is reporting back to spacecraft test conductor Dick Proffitt on the status of the propellants. We pressurize these propellants with helium."

[The Service Module's RCS (Reaction Control System) has 16 thrusters grouped into four clusters, mounted around the spacecraft's skin. Since each cluster carries four thrusters, it is known as a 'quad'. Feeding each quad are two sets of propellant tanks; a larger primary pair of fuel and oxidiser, and a smaller secondary pair. Though each tank is pressurised with helium, this gas does not mix with the propellant. Instead, the propellant is contained within a teflon bladder within the metal walls of the tank and the helium is introduced between the bladder and the walls, squeezing the bladder and expelling its contents without mixing with it. This technique is used because the RCS jets will operate when the spacecraft is weightless. Otherwise, the liquid within would tend to float around the tank and there would be no guarantee of it going to the tank's outlet.]
Public Affairs Officer - "The countdown has been going very well since it was picked up at 10:51 pm Eastern Standard Time last night. Shortly before we resumed the count, the 9.8-million-pound [4,450-tonne] Mobile Service Structure was moved to its park position some 7,000 feet [2,100 metres] from the pad. About an hour later we began the propellant loading of the Saturn V launch vehicle. In some 4 and a half hours we loaded close to a million gallons [over 3½ million litres] total of liquid oxygen and liquid hydrogen aboard the 3 stages of the Saturn V. We now have a vehicle standing 360 feet, 363 feet [110.6 metres] that is, and weighing 6.2 million pounds [2,800 tonnes] on the launch pad here at the Kennedy Space Center. We are continuing a top off [of] the liquid oxygen and liquid hydrogen supplies because they must be maintained under extremely cold temperatures. They will continue to boil off and we will continue to replenish the supply down to the final minutes of the count."
[Originally conceived as an arming tower to install and arm the many ordnance items on the launch vehicle, the Mobile Service Structure ended up as a facility primarily to protect the spacecraft from the elements and allow access to it while out at the pad. It is shown having been pulled back from the spacecraft in photo s68-55415. Like the mobile launcher that now supports the rocket, it is carried between the pad and its own parking space by the crawler/transporter, the massive tracked vehicle that continued to ferry the Space Shuttle to KSC's launch pads long after the Apollo era.]

[Also seen in s68-55415 at the top of the escape tower is the Q-ball cover. This covers and protects the Q-ball, eight openings at the top of the Launch Escape Tower. These openings lead to air data probes which gauge air pressure and temperature. As well as providing dynamic pressure (known as "Q") information during powered flight, they help determine the angle of attack of the tower during an abort event. The crew can monitor any off-axis pressure on a gauge on panel 1 normally used to monitor combustion pressure in the spacecraft's SPS engine. A switch will be thrown after the tower is jettisoned to effect this change. Dual use of instruments is common in the spacecraft as it saves weight and panel space.]

Public Affairs Officer - "Astronauts Frank Borman, Jim Lovell, and Bill Anders were awakened in their crew quarters this morning at 2.36 a.m. Eastern Standard Time. They went down the hall from the crew quarters here at the Kennedy Space Center and took a physical examination, a brief launch day examination, and were declared physically fit by the 3 examining physicians, Dr. Allen Harter, Dr. Jerry Joiner, and Dr. Jack Teegan. The astronauts then sat down to breakfast. They had a menu of filet mignon, scrambled eggs, toast, coffee, and tea. Guests at the breakfast included George Low, Director, Apollo Program Director at the Manned Spacecraft Center; Donald K. Slayton who is Director of Flight Crew Operations at the Manned Spacecraft Center; two of the backup pilots for the Apollo 8 mission, Astronauts Neil Armstrong and Buzz Aldrin. Astronaut Jack Schmitt also attended the breakfast. Following the breakfast, the astronauts went to the suit room where they donned their spaced suits."
[During the Apollo program, primary responsibility for crew selection fell to Deke Slayton who had become the Director of Flight Crew Operations after he was grounded from Project Mercury. His system was based around a simple structure whereby a crew would be assigned the backup role on a mission, miss two missions and be prime crew for the third. The backup crew for Apollo 8 could therefore expect to be the prime crew of Apollo 11 and if Apollos 9 and 10 are successful, can expect to carry out the first landing attempt. So it was with Neil Armstrong and Buzz Aldrin. The third member of the backup crew is Fred Haise in the Lunar Module Pilot role.]

[Apollo 8's crew assignment went through one major change when Mike Collins was taken off the Command Module Pilot role because of a problem with the bones in his spinal column. At first thought to be a spur of bone that was causing the problem in his neck, an eventual operation removed a disc from between two vertebrae and fused them together. Jim Lovell came in to replace him. Restored to flight status, Mike went on to the CMP role on Apollo 11, bumping Buzz Aldrin to be Lunar Module Pilot. He is one of the three CapComs for this mission and will cover the launch and departure from Earth orbit. Fred Haise was again backup LMP on Apollo 11 and became prime LMP on Apollo 14 which was then swapped to become Apollo 13.]

Public Affairs Officer - "The crew departed from the crew quarters at 4:32 am this morning, and began to board the spacecraft starting at 4:58 am at the 320-foot level. First over the sill was the commander, Astronaut Frank Borman. He was followed by the Lunar Module Pilot, Astronaut Bill Anders at 5:02 am, and finally the man who sits in the middle seat, Jim Lovell, came aboard at 5:07 am. The hatch on the Apollo 8 spacecraft was closed at 5:34 am. Since that time, our countdown has been progressing very satisfactorily. We are still Go for launch attempt at 7:51 am Eastern Standard Time. This is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 21 minutes and counting and we are Go for the Apollo 8 mission at this time. We really have a beautiful morning for the flight to the Moon. The weather conditions are very satisfactory for a launch attempt. Surface winds in the area are from the north-west at 7 knots, the temperature is about 60 degrees. We appear to have some scattered clouds from 10 to 12,000 feet high. All aspects of the mission are Go at this time. Weather is also satisfactory in around-the-world tracks where the contingency areas will be located. Weather is satisfactory in both the Atlantic and Pacific Oceans. We are still aiming toward a planned lift-off time of 7:51 a.m. Eastern Standard Time. Coming up shortly will be a transfer to full internal power aboard the Apollo 8 spacecraft. This is going full on the fuel cells and removing an external power that had been sharing a load earlier. This is Launch Control."

[At T minus 20 minutes, the TLI Procedures checklist comes into effect at the top of page L-1 and this includes items pertaining to preparation for launch and to the ascent. First item is to ensure the launch azimuth is entered into the computer. Then there are checks of the attitude displays, voice checks, and checks that the switches on the Main Display Console relevant to the automatic aborting of the Saturn V vehicle are all properly set.]
Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 16 minutes and counting. The Apollo 8 space vehicle is Go for our planned lift-off at this time. We have just completed our transfer to full internal power with the fuel cells for the Apollo 8 spacecraft. This was confirmed by spacecraft commander Frank Borman."
[With the spacecraft now being powered fully by the onboard fuel cells, the reactant valves are latched open to ensure that the hydrogen and oxygen they need keeps flowing.]
Public Affairs Officer - "Final checks from the flight azimuth going on at this time and we're also synchronizing the clocks in the spacecraft with the Mission Control Center in Houston. Following are some of the highlights that will be coming up with the final phases of the count. We'll have a final status check at about 5 minutes and 30 seconds, and at the 5-minute mark the Apollo access arm, the top arm will be fully retracted to its fall back position. The countdown sequencer will be armed at 4 minutes and 30 seconds and we'll get a clearance for launch from the range at the 4 minutes mark in the count. The key event will come at 3 minutes and 6 seconds. It's identified in the procedures as the firing command and it's the start of an automatic sequence. It starts at 3 minutes, 6 seconds and leads up to the ignition of the five engines in the first stage of the Saturn V. Those engines, the sequence, the engine ignition, will start at 8.9 seconds. As we build up the thrust, we should get a commit that we have satisfactory thrust coming out of all five engines as it builds up a thrust level close to seven and a half million pounds of thrust required for this rocket. We should get a lift-off at zero. We are now T minus 14 minutes, 22 seconds and counting. All aspects of the mission [are] Go at this time. This is Launch Control."
[The Saturn V rocket for Apollo 8 is shown in s68-55416, probably taken in the evening. As configured for Apollo, it is 110.6 metres tall and along most of its length is 10.05 metres in diameter. It consists of three stages. The S-IC first stage is 42.1 metres tall and comprises a larger tank for the LOX (the oxidiser) and below that, a tank for the fuel. This is a highly refined kerosene known as RP-1 (Rocket Propellant-1). Five F-1 engines are clustered at the bottom of the stage to provide 6,770 kN (1,522,000 pounds) each for a total of 33,850 kN (7,610,000 pounds) of thrust. This will increase to 40,000 kN (9,000,000 pounds) of thrust just before shutdown, the result of operating in the near vacuum.]

[Readers should note that at no time during Apollo 8 were metric or SI units used for any parameter in the mission, except for reports by engineers at MSFC, influenced as they were by the Germans that were the core of the centre. (This is the reason that distances on the Moon were given in kilometres during the later flights - the Lunar Rover was designed at MSFC.) In this journal, however, it is our policy to use SI units wherever possible while quoting original, usually English units. We will freely convert between the two systems.]

[The second, or S-II, stage of the Saturn V vehicle is 24.9 metres tall. Its bulk volume comprises an enormous insulated tank for a million litres of liquid hydrogen fuel. Below, and sharing a common bulkhead is the smaller, squat LOX tank which carries 331,000 litres. These tanks feed five J-2 engines, the fuel arriving via five protruding conduits which take it around the outside of the LOX tank. The engines produce 1,015 kN (228,000 pounds) thrust each for a total of 5,070 kN (1,140,000 pounds).]

[The S-IVB is the third stage of this rocket. Similar in construction to the S-II, its LH2 tank carries 253,200 litres, while the LOX tank's capacity is 92,350 litres. These feed a single, restartable J-2 engine which yields a thrust of 903 kN (203,000 pounds). The stage is narrower than the other two stages, at 6.56 metres diameter. It will inject the Apollo spacecraft into Earth orbit and, after checkout, onto the Moon.]

Public Affairs Officer - "This is Apollo Saturn Launch Control at T minus 11 minutes and counting; T minus 11 and that count is still Go at this time. Coming up shortly, about 5 minutes from this time actually, we will retract [the White Room] to its full fallback position - the spacecraft access arm, which is at the 320-foot level at the spacecraft. The astronauts, astronauts Frank Borman, Jim Lovell, and Bill Anders, going through some final communications checks with the crew here in the Control Center. These are checks of the VHF communication, the very high frequency communications that will be used at the lift-off. We want assure ourselves that they will be operating satisfactorily. Also coming up, the astronaut crew will be busy on some final checks of astrocomm circuit. This is a special circuit in which abort recommendations could be given to the astronauts if the indications were received as such here in the Control Center some 3½ miles from the launch pad. Also, Mission Control Center in Houston can send the same recommendation. We have now passed the 10-minute mark in our countdown. We are 9 minutes, 51 seconds and counting. All aspects of the mission [are] Go at this time. Still aiming for a launch time of 7:51 am Eastern Standard Time on a flight azimuth of 72 degrees. The flight azimuth has been verified in the instrument unit, the guidance system for the launch vehicle and we have also had an update to assure that we had the correct flight azimuth in the spacecraft. This has been confirmed by the crew and we are proceeding. T minus 9 minutes, 21 seconds and counting, this is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control T minus 7 minutes, 30 seconds and counting. Still aiming toward our planned lift-off time. The Spacecraft Test Conductor Dick Proffitt has just to complete a status check of all elements concerning the spacecraft operations. All reported Go and there were three particularly strong and loud Go's from the three astronauts in the spacecraft 320 feet above the base of the launcher at Complex 39. Jim Lovell reported just a few minutes ago that he could see a blue sky and it looked like the Sun is out. The Spacecraft Test Conductor reported that it's a very fine day. We are at T minus 6 minutes, 50 seconds and counting and we are proceeding at this time. This is Launch Control."

Public Affairs Officer - "This is Apollo Saturn Launch Control at 5 minutes, 30 seconds and our count is still Go at this time. We just completed further status checks here in the Firing Room at the Control Center. Here in the Control Center, we have had our status checks and the range has given a Go as has the Launch Director Rocco Petrone. We are still counting and are Go coming up on the 5-minute mark in the count. Mark. T minus 5 minutes and counting, T minus 5. At this point, the Apollo access arm should be coming back and it is now moving back at the 320-foot level to its fully retracted position high atop the tower at Pad A. Our countdown still proceeding at this time. At the 4-minute mark in the countdown, the overall count will be turned over the Launch Vehicle Test Conductor, Ray Roberts. The Launch Vehicle Test Conductor, will conduct the final 4 minutes as all different aspects move over to the Launch Vehicle Test Conductor's channel. The automatic sequence, as reported, will come in at the 3-minute and 6-second mark in the countdown. We are standing by at 4 minutes, 16 seconds in counting. This is Launch Control. This is Launch Control coming up on 3 minutes and 30 seconds and counting. Mark. T minus 3 minutes and 30 seconds and counting. We have completed our communications checks with the Apollo 8 astronauts in the cabin and the communications are Go. Coming up shortly we'll be in the automatic sequence, where we have a completely automatic checkout of the launch vehicle from 3 minutes and 6 seconds down. We have firing command. The firing command is in, we are now in the automatic sequence. T minus 3 minutes and counting. During this period, Once we do get the firing command, the various tanks within the three stages or the Saturn V launch vehicle begin to pressurize. They must all be under pressure before ready to launch. We have a sequence status report here in the Control Room. It will give us read-outs on the overall status of the space vehicle as we reach the terminal phases in the countdown. Now 2 minutes and 32 seconds and counting. Our status report indicates that all aspects are ready. The Instrument Unit is ready, the spacecraft is ready - is ready. A final check of the Emergency Detection System, that ready light also on. First stage preparations are completed."

[The Emergency Detection System (EDS) automatically measures critical values such as S-IC thrust, rotation rate and structural integrity, and act upon these to initiate an abort if required during that part of ascent where human reaction would be too slow to ensure escape from the situation. It is normally inhibited once the major part of the atmosphere has been left behind.]

[The computer, meanwhile, has begun operation using Program 01, which initialises all its storage locations and allows the guidance platform to be properly aligned. P01 leads to P02, which the crew now verify is operating. This program permits the crew to backup the lift-off discrete. When lift-off finally occurs, it will automatically move the computer to P11, which will operate during ascent. The crew are at the bottom of page L-1.]

Public Affairs Officer - "Two minutes, 15 seconds and counting, the tanks continuing to pressurize in the vehicle. Not as many reports coming now as we all stand by in the Launch Vehicle Test Conductor's channel. Coming up on the 2-minute mark in the Apollo 8 mission, Two minutes and counting. T minus 2 minutes and counting, we are still proceeding. We now have recorded that the first stage liquid oxygen tank has been pressurized and the pressure still building up. One minute, 45 seconds and counting, we have a vehicle weighing 6.2 million pounds on the pad. Interesting enough, some 1,200 pounds of that weight is just frost on the side of the vehicle created by the extremely low temperatures of the propellant. Coming up on 90 seconds. Mark. T minus 90 seconds and counting. The Apollo 8 crew standing by, spacecraft commander Frank Borman, Jim Lovell, and Bill Anders. We now have a report that the liquid hydrogen tank in the first stage [probably means third stage] is pressurized."
[To the Commander's left, just underneath his window is panel 325. Just prior to launch, as on page L-2 of the checklist, he pulls a handle on this panel that causes the feed of coolant to the spacecraft's radiators to bypass them. In photograph s68-55415, one of these two radiators is visible as the large white panel wrapped around the base of the Service Module. There is another on the opposite side. In space, these radiators take warmed water/glycol coolant and, by radiation of heat, lower its temperature. An increased flow is preferentially sent to the radiator facing away from the Sun as it is better able to radiate the heat. However, during the ascent through the atmosphere, the skin of the spacecraft will endure significant frictional heating and will be unable to act as a cooler. Therefore it is bypassed until after orbit is achieved.]
Public Affairs Officer - "One minute, 15 seconds, all third stage propellants pressurized at this time as we come up on the 60-second mark on a flight to the Moon. T minus 60 seconds and counting, the vehicle is now completely pressurized. We are coming up on power transfer shortly. T minus 50 seconds and counting. We have the power transfer and are now on the flight batteries within the launch vehicle. Forty-five seconds, final reports coming from Frank Borman at this time, a final look at the switch list aboard the spacecraft."
[Two of the spacecraft's batteries have been switched across the main power busses in the Command Module to supplement the power from the fuel cells during this period of particularly high demand. Later in the mission, these batteries will be recharged from the fuel cells when the rest of the spacecraft's demand have reduced.]

[At about T minus 45 seconds, a tape recorder in the Command Module is to be placed in the record mode by Bill Anders. This recorder, known as the DSE (Data Storage Equipment) records spacecraft telemetry as a digital code, and there is a track to record the crew's onboard conversations. Mission Control can replay the tape's contents to Earth at a time that suits them. It is primarily intended for those times in the mission when a good radio link cannot be maintained with Earth (like when behind the Moon or during powered flight). If the recorder was started, no onboard conversation from the launch has survived in the DSE's voice transcript.]

[Before the engines are ignited, the final operation by the crew is a "GDC align". The GDC (Gyro Display Coupler) provides a separate attitude reference via a set of strapped-down gyros, the BMAGs (Body-Mounted Attitude Gyros). It provides the drive signals for the attitude indicators, and for launch, the crew want these displays to show attitude with respect to the main attitude reference, the IMU (Inertial Measurement Unit). The GDC Align push button is to the lower left of the Main Display Console, next to the Attitude Set Control Panel. The push button is held until the expected attitude display of 162° in roll, 90° in pitch and 0° in yaw is achieved. The value for roll is derived from the current value for roll (90°) plus the flight azimuth of 72°]

Public Affairs Officer - "35 seconds and counting. We'll lead up to an ignition sequence start at 8.9 seconds, which will lead up as we build up the thrust to a lift-off, if all goes well, at zero. We just passed the 25 second mark in the count, 20 seconds, all aspects we are still Go at this time."
[At 16.97 seconds before launch, the guidance platform in the Saturn's IU is released, known as the Guidance Reference Release (GRR) event. It is assumed that the launch is definitely going to happen and so they know what the launch azimuth is going to be. Remember that the Earth is turning and throughout the launch window, the required flight azimuth (essentially the bearing flown by the vehicle as it leaves) constantly changes. Now the Saturn's guidance platform is free to keep a constant orientation as the vehicle rotates around it.]

[The GRR event marks the start of 'timebase zero', the first of eight timebases which the Saturn's computer uses to sequence pre-programmed events. This occasional resetting of the computer's timing reference gets around the fact that the length of some actions is indeterminate. TB-0 sequences all events leading up to lift-off.]

Public Affairs Officer - "T minus 15, 14, 13, 12, 11, 10, 9, and we have ignition sequence start."
[We are at the top of page L-3 in the checklist.]

[The F-1 engine has a complex ignition sequence which will be described here. First, a description of the engine.]

Labelled diagram of F-1 engine

[ A large combustion chamber and bell have an injector plate at the top, through which RP-1 fuel and LOX are injected at high pressure. Above the injector is the LOX dome which also transmits the force of the thrust from the engine to the rocket's structure. A single-shaft turbopump is mounted beside the combustion chamber. The turbine is at the bottom and is driven by the exhaust gas from burning RP-1 and LOX in a fuel-rich mixture in a gas generator. After powering the turbine, the exhaust gas passes through a heat exchanger, then to a wrap-around exhaust manifold which feeds it into the periphery of the engine bell. The final task for these hot gases is to cool and protect the nozzle extension from the far hotter exhaust of the main engine itself. Above the turbine, on the same shaft, is the fuel pump with two inlets from the fuel tank and two outlets going, via shut-off valves, to the injector plate. A line from one of these 'feeds' supplies the gas generator with fuel. Fuel is also used within the engine as a lubricant and as a hydraulic working fluid, though before launch, RJ-1 ramjet fuel is supplied from the ground for this purpose. At the top of the turbopump shaft is the LOX pump with a single, large inlet in-line with the turboshaft axis. This pump also has two outlet lines, with valves, to feed the injector plate. One line also supplies LOX to the gas generator. The interior lining of the combustion chamber and engine bell consists of a myriad of pipework through which a large portion of the fuel supply is fed. This cools the chamber and bell structure while also pre-warming the fuel. Lastly, an igniter, containing a cartridge of hypergolic fluid with burst diaphragms at either end, is in the high pressure fuel circuit and has its own inject point in the combustion chamber. This fluid is triethylboron with 10-15% triethylaluminium.]

[At T minus 8.9 seconds, a signal from the automatic sequencer fires four pyrotechnic devices. Two of them cause the fuel-rich turbine exhaust gas to ignite when it enters the engine bell. Another begins combustion within the gas generator while the fourth ignites the exhaust from the turbine. Links are burned away by these igniters to generate an electrical signal to move the start solenoid. The start solenoid directs hydraulic pressure from the ground supply to open the main LOX valves. LOX begins to flow through the LOX pump, starting it to rotate, then into the combustion chamber. The opening of both LOX valves also causes a valve to allow fuel and LOX into the gas generator, where they ignite and accelerate the turbine. Fuel and LOX pressures rise as the turbine gains speed. The fuel-rich exhaust from the gas generator ignites in the engine bell to prevent backfiring and burping of the engine. The increasing pressure in the fuel lines opens a valve, the igniter fuel valve, letting fuel pressure reach the hypergol cartridge which promptly ruptures. Hypergolic fluid, followed by fuel, enters the chamber through its port where it spontaneously ignites on contact with the LOX already in the chamber.]

Public Affairs Officer - "The engines are on. 4."

[Rising combustion-induced pressure on the injector plate actuates the ignition monitor valve, directing hydraulic fluid to open the main fuel valves. These are the valves in the fuel lines between the turbopump and the injector plate. The fuel flushes out ethylene glycol which had been preloaded into the cooling pipework around the combustion chamber and nozzle. The heavy load of ethylene glycol mixed with the first injection of fuel slows the build-up of thrust, giving a gentler start. Fluid pressure through calibrated orifices completes the opening of the fuel valves and fuel enters the combustion chamber where it burns in the already flaming gases. The exact time that the main fuel valves open is sequenced across the five engines to spread the rise in applied force that the structure of the rocket must withstand.]
Public Affairs Officer - "...3..."

graph of engine thrust rise during F-1 startup

[This diagram shows how the thrust built up in each engine. It takes two seconds for full performance to be attained on all engines once the first has begun increasing. The engines are started in a staggered 1-2-2 sequence so that the rocket's structure would be spared a single large load increase, with the centre engine being the first to start. The graphs for the four outboard engines show a distinct hiccup in their rate of increase as they reach about three-quarters of full thrust. This is due to helium from the pogo suppression system being ingested by the engines. The centre engine had had its system disabled before the flight.]

[Borman, from the 1969 Technical Debrief - "The S-I ignition sequence starts at T minus 9 seconds; however, the crew noticed no indication of ignition until about T minus 3 seconds, when the noise level reaches the cockpit."]

[As the flow of fuel and LOX rises to maximum, the chamber pressure, and therefore thrust, is monitored to confirm that the required force has been achieved. With the turbopump at full speed, fuel pressure exceeds hydraulic pressure supplied from ground equipment. Check valves switch the engine's hydraulic supply to be fed from the rocket's fuel instead of from the ground.]

Public Affairs Officer - "2, 1, 0."
[Image KSC-71PC-543 shows the vehicle on the pad as the engines build up to their full thrust. Note that the image of the crescent Moon has been artificially added to this photograph.]

[At lift-off, one of the most important areas of the Main Display Console that the Commander must monitor is the subpanel which annunciates the progress of the launch. From top to bottom, this subpanel contains the Abort light, Mission Event Timer and Launch Vehicle Engine lights.

Photograph of the launch vehicle lights panel onboard Odyssey, the Apollo 13 Command Module.

This photograph shows the panel of launch vehicle indicator lights as seen in the Apollo 13 Command Module Odyssey. Below this is the lift-off light which is embedded top-left in a cluster of critical switches (with safety covers) that are used to override the automatic abort sequences.

Photograph of the abort override panel onboard Odyssey, the Apollo 13 Command Module.

One second to lift-off, the five launch vehicle indicator lights in the spacecraft have gone out, announcing to the crew that the thrust is OK and the stack is about to be let go by the hold-down clamps.]

Public Affairs Officer - "We have commit."

[At the point of lift-off, the lift-off lamp is illuminated as a verification for the crew.]

[The stack is held onto the pad two ways. Four hold-down arms clamp the base of the S-IC, each capable of applying a force of 350 tonnes, anchoring the vehicle until full thrust is confirmed. A pneumatic device, backed up by an explosive, collapses the lever linkage to allow the arm to rise. Additionally, this vehicle has 12 controlled-release mechanisms which prevent the vehicle from accelerating too rapidly in the first moments of motion. These consist of tapered pins mounted to the pad which are pulled through dies mounted on the vehicle. The deformation of the pins controls the initial acceleration for the first 150 mm of flight; a simple and ingenious arrangement.]

Public Affairs Officer - "we have lift-off, lift-off at 7:51 a.m. Eastern Standard Time."

[Once the launch vehicle begins to rise, even fractionally, it cannot safely settle back onto the pad. Shutdown of the engines for the first 30 seconds of flight is explicitly inhibited, as even a controlled shutdown of an engine at this critical early phase, would result in a catastrophic collapse of the Saturn back onto the pad. Even a failing engine may be creating some thrust, and might be enough to buy time for an abort. This also eliminates the possibility of shutting down an engine due to an error in the Emergency Detection System. The vehicle is now in motion, so of the nine access arms, the five which have remained attached up to this point, must now detach their umbilicals from the vehicle and swing clear. These supply services to the S-II, S-IVB and the Service Module. The first two centimetres of travel trigger the release of the umbilical connector plates which in turn triggers retraction of the arms.]

[Disconnection of the IU's umbilical triggers the start of timebase 1.]

000:00:01 Borman: Lift off. The clock is running.

000:00:04 Collins: Roger. Clock. [Pause.]

[Photograph KSC-68PC-327 shows the rising vehicle as seen from the southeast, and S68-56002 is a view from the west some seconds later. In this latter view, a yaw motion is discernible by the leaning of the stack away from the tower. The vehicle is programmed to fly this 1.25° yaw maneuver, beginning one second into the flight, in case a gust of wind comes up that might tend to push the vehicle into the umbilical tower.]

[Borman, from the 1969 Technical Debrief - "There was no reason for concern on lift-off. There was vibration until the hold-down arm's release, and then at lift-off, you got an acceleration similar to the Titan."]

[Lovell, from the 1969 Technical Debrief - "That's right, except it appeared that the sense slowed down a little bit after it got off the ground, and I was watching the altimeter and it didn't seem to go up as rapidly as the initial lift-off did."]

[The altimeter is mounted at the top of panel 1 and is usually used to monitor the spacecraft entry back into the atmosphere.]

[Anders, from the 1969 Technical Debrief - "It was my recollection that the vibration continued until slightly past 'tower clear' call."]

[This may have been the sound waves bouncing off the tower and back onto the Saturn V. Also, the yaw steering has completed by the time the vehicle has cleared the tower.]

[Borman, from the 1969 Technical Debrief - "After the vehicle was released, the noise in the cockpit got very loud and effective crew communication was impossible. The last call that I heard was a faint 'tower clear' call by the LOM [Launch Operations Manager]. Did you hear it very well, Bill? You heard it, Jim. All three of us heard that call; however, it was really in the background. The noise was loud, but the flight was smooth until we went through Max Q or Mach 1. After that it smoothed out and the S-IC gave a very stable, smooth ride."]

[Lovell, from the 1969 Technical Debrief - "I don't think that the vibrations were any greater than they were in the Titan. Although there were a lot of small separate vibrations and a lot of noise, I think the flight itself was very smooth."]

[Anders, from the 1969 Technical Debrief - "The thing that impressed me about the early stages of lift-off was the very positive control during the gimbaling of the S-IC engines. It was very positive.]

["I thought the sideways oscillations during the early part of lift-off were a little bit greater than the DCPS [Dynamic Crew Procedure Simulator at Houston, an early example of a simulator which could impart motion and vibration to the crew to help them get a feel for the launch experience]. In fact, it felt to me on the first stage ride like an old freight train going down a bad track."]

[The initial yaw maneuver makes the stack rotate around its center of gravity. At launch, this is about 30 metres above the rocket's base, midway along the LOX tank. The crew is at the end of a lever arm 67 metres long. Even the 1.25° of motion adds up to 5 or 6 feet sideways movement in the CM in just a few seconds.]

Public Affairs Officer - "We have cleared the tower. Tower clear at 13 seconds."

000:00:14 Borman: Roll and pitch program.

000:00:16 Collins: Roger.

[The Flight Plan calls for Frank to report to Mission Control the accomplishment of many of the events that occur during ascent. He has already reported lift-off and like many other commanders, has not reported the yaw maneuver. Frank does report the initiation of the roll and pitch program.]

[Clear of all the pad's ironwork, the rocket can safely rotate around its longitudinal axis by 17.876° from its launch roll angle of 90 ° to its flight azimuth of 72.124°. With the roll completed, it will begin pitching over to fly along this bearing with the crew in a heads-down attitude. All these maneuvers are pre-programmed - although the rocket's computer 'knows' where it is, it is not using that information to adjust its flight path. It will dumbly fly a precise set of maneuvers, known as the tilt sequence, until the second stage has taken over. This sequence has been computed to place as little sideways aerodynamic force on the vehicle as possible while it gets through the thicker atmosphere.]

000:00:18 Borman: How do you hear me, Houston?

000:00:19 Collins: Loud and clear. [Long pause.]

[The full extent of AS-503's tail of flame is beautifully displayed in KSC-68PC-341 and s68-56050.]
Public Affairs Officer - "20 seconds now we get a loud and clear from Frank Borman."
[The four outboard engines cant outwards at this point so that if one of them should shutdown inadvertently, the direction of thrust will still be near the rocket's centre of gravity. The vehicle's roll maneuver should be complete by 28 seconds.]

[As the stack makes its way to orbit, it passes through predetermined slices of time during which there are appropriate ways of aborting the mission should something go seriously wrong. These are known as abort modes. For the first two of these, there are defined safe ranges of vehicle motion rates as not exceeding ±4° per second in pitch and yaw, ±20° per second in roll. Motion rates exceeding these limits will entail an abort.]

[The first 42 seconds of flight, which takes the stack to an altitude of about 3,000 metres (10,000 feet) are flown in abort Mode IA (one Alpha). In this mode, the CM would separate from the SM then the LET (Launch Escape Tower, or just 'tower'), which is the solid-fuelled rocket mounted on top of the CM, would carry it up from the wayward launch vehicle while a small 'pitch control' motor at the top of the LET would steer the assembly east out over the ocean and away from a possibly exploding booster below. The tower would be jettisoned only 14 seconds after the initiation of the abort. While this is going on, 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 descend on parachutes to a normal splashdown.]

Public Affairs Officer - "32 seconds, BOOSTER says the S-IC, the first stage, looks good."
['BOOSTER' is the name given to one of the front row console positions in Mission Control. There is one for each stage. Once that stage's job is done, the position is vacated.]
000:00:42 Collins: Mark. Mode 1 Bravo, Apollo 8.

000:00:44 Borman: Mode 1B. [Pause.]

[Abort Mode IB extends from 42 seconds into the flight to an altitude of 30.5 km (16.5 nautical miles) as defined by the launch/insertion checklist. With the vehicle being further downrange and tilted over, the pitch control motor would not be required in the event of a IB abort. However, it had been discovered during hypersonic testing, that the CM/LET stack could be marginally aerodynamically stable in a tower-first as well as a base-first attitude so a pair of canards were added which would be deployed automatically to force the 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 IB mode.]
Public Affairs Officer - "The crew confirms their progress at 50 seconds into the flight."
[While the vehicle was sitting on the pad, the spacecraft cabin maintained an atmosphere of 60% oxygen, 40% nitrogen, the latter being supplied by equipment on the ground. Meanwhile the crew breathed pure oxygen within their suits. As the vehicle ascends into thinner air, the cabin pressure is allowed to fall until it reaches 41 kPa (6 psi) whereupon automatic regulators begin maintaining it at that pressure. The circuit which supplies suit air is kept at a slightly higher pressure and it dumps into the cabin, gradually replacing the mixed atmosphere with a pure oxygen one. In case the cabin pressure has not fallen by the time they reach 7.6 km altitude, the checklist includes instructions to operate the cabin pressure relief valve and dump some of the spacecraft's atmosphere.]
000:00:58 Collins: Apollo 8, you're looking good.

000:01:01 Borman: Roger. [Long pause.]

Public Affairs Officer - "One minute out and Mike Collins tells the crew, 'We're looking good.' One minute, 15 seconds, and we're a little more than half a mile into the sky and about - nearly 4 miles downrange."

[The announcer's figures are incorrect and he has probably slipped a decimal point. As Frank replies, Apollo 8 reaches Mach 1; the speed of sound and is already at 7.35 km altitude. As the vehicle gains speed, the aerodynamic forces acting upon it also rise. However, as it ascends and encounters thinner air, these forces will decrease and at about this point, 1 minute, 18.9 seconds into the flight and 13,430 metres (44,062 feet) altitude, the stack reaches the point of maximum dynamic pressure, often called Max Q, where the interaction of these two phenomena has the largest effect on the vehicle's structure. It is usually considered a more dangerous time within the whole ascent.]

Dual graph showing vehicle's Mach number and the dynamic pressure experienced throughout atmospheric flight.

[This graph, redrawn from the AS-503 Flight Evaluation Report, illustrates the changes in the vehicle's Mach number, and the dynamic pressure the vehicle experiences as it rises through the appreciable atmosphere.]

Public Affairs Officer - "One minute, 40 seconds, all looks great. A mile and 6/10ths into the mission and Frank Borman has confirmed each event as it's been passed to him by Mike Collins at this point."

000:01:52 Collins: Mark. Mode 1 Charlie, Apollo 8.

000:01:54 Borman: Mode 1C. [Pause.]

[Mode IC is used for aborts occurring between 30.5 km (16.5 nautical miles) and the jettison of the tower. As the air is now very thin, the airflow around the pair of canards at the top of the tower would have little aerodynamic effect during an abort, so the Command Module's RCS would be used to control the orientation of the spacecraft until they become effective. Note that in the Mode IC abort (on page A-2 of the checklist) that the canards are deployed even before the RCS is pressurized. This may be because if the CM gets into a "pointy end forward" attitude for too long, the RCS will be ineffective once it reaches the denser air. The safe range of vehicle motion rates are now defined as not exceeding ±9° per second in pitch and yaw, ±20° per second in roll.]

[The crew are at the top of page L-4 in the checklist. Now that Apollo 8 is above the significant atmosphere, the danger of an aerodynamically induced catastrophe has subsided. The EDS is disabled by Jim Lovell throwing a switch on Panel 2 of the Main Display Console. Most malfunctions of the launch vehicle can be dealt with by human intervention and aborted manually.]

[The prodigious consumption of the F-1 engines means that the vehicle is becoming lighter by 15 tonnes each second. This, and the fact that they are becoming more efficient in the near-vacuum means that the g-forces experienced by the crew are rising rapidly. Therefore, at 2 minutes and 6 seconds, the centre engine of the S-IC stage is shutdown by a pre-programmed signal to limit this acceleration. The same signal lights the centre lamp of the launch vehicle indicator lights momentarily and also begins timebase-2, providing the vehicle has achieved sufficient velocity (a measure to keep the vehicle safe in case TB-1 starts inadvertently). At the time of this cut-off the total stage thrust had risen by 20% to 40,000 kN (9,000,000 pounds). The outboard engines will burn until depletion of the LOX supply is sensed, in this case, another 28 seconds.]

[Eight seconds before the outboard engines cut-off, the slow, deliberate tilting of the vehicle is brought to a halt - the so-called 'tilt arrest' - in preparation for staging. When the two sections of the Saturn come apart, they do not want there to be any appreciable rotation of either.]

000:02:07 Collins: Apollo 8, Houston. You are Go for staging. Over.

000:02:10 Borman: Roger. [Long pause.]

Public Affairs Officer - "The crew has been given a Go for staging. Inboard [engine is] out on time, Frank Borman says. The inboard engines. 2 minutes, 25 seconds. We see an S-IC, the first stage cut-off."

[The first stage engines underperformed by three-quarters of one percent but the stage burned for 2.45 seconds longer, shutting down at 2:34 GET, an event intimated to the crew by the four outer engine lights on a display coming on.

Layout of launch vehicle lights.

This is the start of timebase-3 which will sequence the staging of the two stages and the operation of the second stage. At cut-off, the rocket is travelling 12.57 metres per second (41.24 feet per second) faster than planned at 1,894 m/s and at an altitude of 65.7 km (35.5 nautical miles).]

000:02:36 Borman: Staging. [Long pause.]
[The first and second stages have, between them, a ring 10 metres in diameter, to match the stages above and below, and a height of 5.5 metres. This ring, the interstage, is there to make room for the S-II's engines which protrude some distance below the bottom edge of the stage's wall. If, at staging, the interstage were to stay with the S-IC, there is a danger that any slight rotation of the massive first stage would cause contact between it and the engine bells on the S-II. Therefore a cut is made directly above the S-IC using a shaped explosive charge. This leaves the interstage attached to the S-II. However, the ring imposes a significant mass penalty on the second stage. So much so that it is a mandatory abort if the interstage doesn't separate. It too is dropped 30 seconds after the first separation. This gives time for the second stage engines to establish smooth acceleration with minimal rotation.]

[The sequence for separation is as follows: Half a second after shutdown of the first stage, the four ullage motors mounted around the interstage ignite, followed a fifth of a second later by a command to fire the first separation explosive and ignition of the eight retro rockets mounted in the conical fairings near the base of the S-IC. The two sets of rockets firing in opposite directions pull the two sections of the vehicle apart. Physical separation comes soon after and half a second later, the J-2 engines on the S-II stage are started. The S-II ullage rockets were eventually deleted from the later Saturn V's. Ullage is a brewer's term for the space in a barrel taken up by air rather than liquor. The rocket people modify its use to mean the establishment of that space at the opposite end of a tank from the outlet so that the liquid leaves the tank cleanly. They usually achieve this by firing small rockets to settle the tank's contents to one end.]

[During the test flights of the Saturn V, NASA mounted film cameras at strategic places around the vehicle to allow engineers to see the dual plane separation at work. The following film clip, kindly donated by www.footagevault.com, is from the flight of Apollo 4. Two cameras were mounted on either side of the S-II stage looking past its J-2 engines toward the departing S-IC.

The start of the movie shows first plane separation. Because the camera was operating at 4-times normal speed, the film appears to portray events at quarter speed. Second plane separation follows near the end of the footage as the interstage falls away. As the ring enters the superhot exhaust gases, it glows furiously, presumably as its paint coating is vapourised. Finally, we catch a few frames of the camera being ejected from the stage in a re-entry capsule to be parachuted into the Atlantic and recovered. This film clip is from the opposite side of the stage.

[In the last third of the twentieth century, these images became icons for America's technological prowess and sense of outreach. Being among the most spectacular films from the early years of space flight, they have found their way into just about every documentary of the era. Indeed, the BBC in the UK used them as its title sequence for its television coverage of Apollo 8 and they seemed to herald the spirit of the age when the dreams of Kubrick's 2001: A Space Odyssey seemed to be coming true.]

[The Apollo 8 launch vehicle also carried a complement of six cameras, four film and two television. The TV cameras were mounted in the base of the S-IC looking at propulsion and control components and their images were radioed to the ground live. Two film cameras were mounted at the top of the S-IC looking up to view the departing S-II and the interstage and to watch the ignition of the five J-2 engines. A further two film cameras viewed the interior of the S-IC's LOX tank via fibre-optic bundles. Only the film from one of the LOX cameras was recovered.]

Public Affairs Officer - "S-II has ignited, we can confirm, and the thrust looks good, all engines, all sources show the second stage is burning perfectly. 2 minutes, 51 seconds into the mission."

[Borman, from the 1969 Technical Debrief - "The S-IC/S-II separation was nominal; the crew was thrown forward in their seat, as you would expect in a staging. Then the g load was shifted from 4 to about 1. Consequently, you noticed the change in thrust quite distinctly.]

["There was some indication of light flash at staging through the hatch window. It was noticeable, in fact, through the left-hand window."]

[The S-II stage carries five J-2 uprated engines which burn LH2 and LOX to produce a total of 5,087 kN (1,143,578 pounds) thrust. The engine design allows for restarting in flight but this feature is only implemented in the engine used in the S-IVB.]

Labelled diagram of J-2 engine

[The thrust chamber and bell of each engine is fabricated from stainless steel tubes brazed together in a single unit. Supercold LH2 is pumped through these tubes to cool the thrust chamber and simultaneously prewarm the fuel. The engine carries two separate turbopumps, both powered in turn by the exhaust from a gas generator which burns the stage's main propellants. The hot gas exhaust is fed from the gas generator, first to the fuel turbopump, then to the LOX turbopump before being routed to a heat exchanger and finally into the engine bell. The fuel and LOX outputs of both turbopumps are fed, via main control valves, to the thrust chamber injector via the LOX dome. Unlike the solid steel injector of the F-1, the J-2 injector is fabricated from layers of stainless steel mesh sintered into a single porous unit. A solid LOX injector behind this carries 614 posts which pass LOX through the injector and into the combustion chamber. Each post has a concentric fuel orifice around it and these orifices are attached to the porous injector. The fuel delivery is arranged to ensure that about 5 percent seeps through the injector face to cool it, the rest passing through the annular orifices.]

[The ASI (Augmented Spark Igniter), fed with propellant and mounted to the injector face, provides a flame to initiate full combustion. Valves are provided to bleed propellant through the supply system well before ignition to chill all components to their operating temperatures otherwise gas would be formed which would interfere with the engine's use of propellant as a lubricant in the turbopump bearings. A tank of gaseous helium is fabricated within a larger tank of gaseous hydrogen. This is the Start Tank. The helium provides control pressure for the engine's valves while the hydrogen spins up the turbopumps before the gas generator is ignited. A PU (Propellant Utilization) valve on the output of the LOX turbopump can open to reduce the LOX flowrate. This adjusts engine thrust during flight to optimise engine performance.]

[To start the J-2 engine, spark plugs in the ASI and gas generator are energised. The Helium Control and Ignition Phase valves are actuated. Helium pressure closes the Propellant Bleed valves, it purges the LOX dome and other parts of the engine. The Main Fuel valve and the ASI Oxidiser valves are opened. Flame from the ASI enters the thrust chamber while fuel begins to circulate through its walls under pressure from the fuel tank. After a delay to allow the thrust chamber walls to become conditioned to the chill of the fuel, the Start Tank is discharged through the turbines to spin them up. This delay depends on the role of the engine. A one second delay is used for the S-II engines. Half a second later, the Mainstage Control Solenoid begins the major sequence of the engine start. It opens the control valve of the gas generator where combustion begins and the exhaust supplies power for the turbopumps. The Main Oxidiser valve is opened 14° allowing LOX to begin burning with the fuel which has been circulating through the chamber walls. A valve which has been allowing the gas generator exhaust to bypass the LOX turbopump is closed allowing its turbine to build up to full speed. Finally, the pressure holding the Main Fuel valve at 14° is allowed to bleed away and the valve gradually opens, building the engine up to its rated thrust.]

[As the thrust of each second stage engine reaches 65%, it causes its indicator light on the Main Display Console to be extinguished.]

000:03:05 Borman: ... second plane Sep.

000:03:08 Collins: Roger. Understand; Sep.

000:03:10 Borman: Roger. [Long pause.]

[Exactly 30 seconds after the first separation command, another is sent from the IU to detonate the cutting explosive at the top of the interstage. The S-II's acceleration cleanly pulls it away from the interstage. Four seconds later, Frank throws a switch and jettisons the unused Launch Escape Tower which takes the Boost Protect Cover with it. For the first time in the flight, all the windows in the spacecraft are uncovered. This film clip, kindly donated by www.footagevault.com, was taken by an automatic camera mounted inside an unmanned command module, believed to be the AS-202 mission.

The jettison of the LET is visible at the very start of the clip, as the porthole on the BPC disappears.]

[Borman, from the 1969 Technical Debrief - "The LET and BPC jettison was nominal. The windows were clear when the tower jettisoned. We had no effect of retrorocket exhaust fumes on any of the windows."]

[With no launch escape tower, they begin flying in Abort Mode II. This lasts until the point where the S-II gives way to the S-IVB. In a Mode II abort, the Command and the Service Modules will separate from the launch vehicle and the SM main engine or its RCS engines will be used to get the spacecraft away from the launch vehicle. Then the CM and SM will separate before the CM completes a normal splashdown on the ocean.]

Public Affairs Officer - "And at 3 minutes into the flight, the Range Safety console has been released at the Cape. 3 minutes into the flight, we are 50 [nautical] miles [93 km] high and about 10 miles [means 100 nautical miles (185 km)] down range."
[So far, the Saturn's guidance system has been keeping track of where it is going but has not done anything to alter its pre-programmed tilt sequence. Now the vehicle is essentially in space and beyond any reasonable aerodynamic forces so the sequence is terminated. At 3 minutes, 16 seconds, the IU begins the IGM or Iterative Guidance Mode, in which it starts steering the rocket to where it wants to go. It begins using position and velocity information to allow it to compute an appropriate trajectory to orbit and adjusts its flight path to achieve it. Attitude control is achieved by rotating or gimballing the outboard J-2 engines which alters the direction of the force they apply.]

[Borman, from the 1969 Technical Debrief - "The guidance initiate was just as simulated on the DCPS. I noticed about a 20-degree pitch-down; the g-level dropped off again, and there was a smooth flight on the S-IVB."]

[The DCPS is the Dynamic Crew Procedure Simulator at Houston, an early example of a simulator which could impart motion and vibration to the crew to help them get a feel for the launch experience.]

Public Affairs Officer - "3 minutes, 25 seconds, we have verified that the tower has jettisoned. The crew has verified the tower has jettisoned."

000:03:31 Borman: Houston, how do you read? Apollo 8.

000:03:34 Collins: We hear you loud and clear, Apollo 8.

000:03:35 Borman: Okay. The first stage was very smooth, and this one is smoother.

000:03:40 Collins: Understand; smooth and smoother. Looks good here.

Public Affairs Officer - "Frank Borman says staging was smooth and the ride now is even smoother."

000:03:47 Collins: Apollo 8, Houston. Your trajectory and guidance are Go. Over.

000:03:51 Borman: Thank you, Houston. Apollo 8.

[Comm break.]
Public Affairs Officer - "Coming up on 4 minutes into the flight and the communications thus far have been excellent. It's been a little sparse but it's been quite sharp and clear. 70 [nautical] miles [130 km] altitude and about 20 miles or more downrange. Correction, let's make that 200 [nautical] miles [370 km] downrange. Flight Director Cliff Charlesworth gets an enthusiastic Go from both TRAJECTORY and BOOSTER at 4 minutes, 50 seconds into the flight."

000:04:58 Collins: Apollo 8, Houston. Your trajectory and guidance are Go. Over.

Public Affairs Officer - "Mark. 5 minutes and the crew is advised their trajectory and guidance are looking good."

[While the S-II is firing, Mission Control are putting out status reports every minute of the ascent.]
000:05:02 Borman: Thank you, Michael.

000:05:04 Collins: Yes, you're looking real good, Frank.

000:05:05 Borman: Very good. [Long pause.]

Public Affairs Officer - "And Frank Borman came back with a very chatty, 'Thank you, Michael.' He's talking to Michael Collins, who would be in the center seat today except for an operation several months ago. 5 minutes, 20 seconds into the flight. 300 [nautical] miles [556 km] downrange. We're nearly nearing 100 [nautical] miles [185 km] altitude, and everything looks just grand."

[Apollo 8 is essentially at its orbital altitude so most of the work the S-II has is to get it up to orbital velocity. With respect to the launch site, this is 7,389 m/s (24,243 fps). However, the Earth is turning so taking its speed out of the number gives 7,793 m/s (25,567 fps). Generally, the velocity readings in the spacecraft are given using this space-fixed frame of reference. The stack will actually overshoot their orbital altitude slightly, coming back 'downhill' as they get towards orbital velocity.]
000:05:59 Collins: Apollo 8, Houston. Trajectory and guidance are Go.

000:06:02 Borman: Roger. Apollo 8. Go.

000:06:05 Collins: Mark.

000:06:06 Collins: You have S-IVB to orbit capability. Over.

000:06:09 Borman: Roger. Thank you. S-IVB to orbit. [Long pause.]

[Should the S-II fail, they can reach the safety of orbit by separating and firing the S-IVB's engine. This would be an abort mode as they would use up fuel in the third stage meant to send them to the Moon. It would mean a Earth-orbital flight only for which an alternate flight plan exists.]
Public Affairs Officer - "And Collins gives the crew another Go on trajectory and guidance, which at this point are the most critical elements. At 6 minutes, 10 seconds into the flight, our downrange distance now 400 [nautical] miles [740 km]. Our velocity in feet per second, nearly 15,000 feet per second [4,600 m/s]. We've achieved nearly 60 percent of the velocity required to make orbit. 57 percent right now, and we're 96.5 [nautical] miles [178.7 km] above the Earth. The SURGEON reports he likes everything he sees."
[They are more or less at orbital height but they are not travelling fast enough to maintain it. If all thrust were terminated now, the vehicle would gently arc back into the atmosphere. It is now essentially horizontal and accelerating at about 1.4g.]

[The flight azimuth they are flying affects the relationship between the vehicle and the ground stations it passes over. As they have got away on time and are flying a 72° azimuth, Bill ensures that antenna D, one of the four omnidirectional antennae around the circumference of the Command Module, is selected.]

000:07:01 Collins: Apollo 8, Houston. Your trajectory and guidance are Go. Over.

000:07:05 Lovell: Apollo 8's Go.

000:07:09 Anders: Onboard chart confirmed.

000:07:10 Collins: Roger. Understand. [Long pause.]

[Bill is probably comparing readings from the DSKY with the tables on pages L-4-A and 4-B.]
Public Affairs Officer - "7 minutes into the flight, and we're nearing the second stage - nearing the point where we will drop off the second stage and light the third stage. That event is to come at about 8 minutes and 40 odd seconds into the flight, We have now achieved 70 percent of the velocity required to obtain orbit. Our present velocity is 18,600 feet per second, and we're 100 miles above the Earth, 100 even. 625 miles downrange."
[At 7 minutes, 23.45 seconds, the PU valve on each J-2 engine is actuated, lowering the flow-rate of LOX, thus altering the mixture ratio and making the engines burn richer. This is part of a strategy to make sure that as little propellant as possible is left in the tanks when the second stage has done its work. As the engines burn, there will always be a slight discrepancy in the actual mixture ratio, nominally 5.5:1, LOX to fuel by mass. By sensing how the levels in the tanks are decreasing, the Saturn's computer can decide an appropriate point to change the mixture ratio to 4.5:1 such that the tanks will be depleted simultaneously. The change causes the thrust of the stage to reduce from 5,087 kN (1,143,578 pounds) to 3,877 kN (871,607 pounds).]
000:07:31 Lovell: Just tried to PU shift, I believe.

000:07:37 Collins: Roger. That's the correct time for it.

000:07:41 Lovell: Roger. [Long pause.]

Public Affairs Officer - "Coming up on 8 minutes. Mark. 8 minutes. 20,400 feet per second [6,218 m/s], 101.7 [nautical] miles [188.3 km] above the Earth, 734 [nautical] miles [1,359 km] down range."

000:08:03 Collins: Apollo 8, Houston. Your trajectory and guidance are Go.

000:08:06 Borman: Roger. We're picking up a slight pogo at this point.

000:08:11 Collins: Understand; slight pogo. Thank you. [Long pause.]

[Pogo is very much a problem in large-scale rocketry, and often misunderstood. First of all, it is not an acronym; rather it is a term borrowed from a child's toy, the pogo stick, a spring loaded affair that children could bounce along on. Like the pogo stick, the phenomenon concerns longitudinal oscillations, but in the launch vehicle, they are unpleasant and potentially damaging.]

[One of the best explanations of the phenomenon was given by George Mueller, then Director of the Office of Manned Space Flight at NASA headquarters, during a congressional hearing into a Boeing contract in July 1968. The text appears in chapter 20-3 of SP-4204, Moonport: A History of Apollo Launch Facilities and Operations, one of the NASA History Series available online.]

[George Mueller, from 1968 Congressional Hearing - "Pogo arises fundamentally because you have thrust fluctuations in the engines. Those are normal characteristics of engines. All engines have what you might call noise in their output because the combustion is not quite uniform, so you have this fluctuation in thrust of the first stage as a normal characteristic of all engine burning.]

["Now, in turn, the engine is fed through a pipe that takes the fuel out of the tanks and feeds it into the engine. That pipe's length is something like an organ pipe so it has a certain resonant frequency of its own and it really turns out that it will oscillate just like an organ pipe does.]

["The structure of the vehicle is much like a tuning fork, so if you strike it right, it will oscillate up and down longitudinally. In a gross sense it is the interaction between the various frequencies that causes the vehicle to oscillate."]

[Borman, from the 1969 Technical Debrief - "The early stages of the S-II flight were nominal - very smooth and very quiet. However, toward the end of the S-II flight, we did pick up a pogo oscillation, I would estimate the frequency to be on the order of 12 cps [cycles per second], and probably plus or minus 0.25 g. Quite frankly, it concerned me for a while, and I was glad to see S-II staging. It never gave any indication of going undamped. It was a noticeable oscillation."]

[From the transcript below, Frank evidently forgot that he had reported that the pogo was, in fact, beginning to be damped out prior to cut-off.]

[Pogo in the S-II stage continued to be a problem for Apollo 9 resulting in modifications to the stage from Apollo 10 onwards to have the centre engine shutdown early, thereby removing a major source of resonance at that time in the flight. The other four engines burned for longer until the propellants are depleted. However, S-II pogo continued to dog the Saturn V and on Apollo 13, the centre engine actually cut out, such was the severity of the shaking. The event is portrayed in the Ron Howard/Tom Hanks movie Apollo 13. The cure on subsequent missions was to install an accumulator in the LOX feed of the centre engine which served to absorb the pressure variations that were an important ingredient of pogo. When and how severe the pogo occurs depends not only on the structure of the vehicle and the flow of its propellante, mass is another of the many factors that influence its characteristics. Apollo 8 is not carrying a Lunar Module and instead has a ring of similar weight as ballast. Nevertheless, the rocket's payload is about 5 tonnes lighter than on subsequent missions.]

000:08:30 Collins: Apollo 8, Houston. You have level sense time. Over.

000:08:32 Borman: Roger. Level sense, On.

[The S-II is nearing the end of its powered flight. The actual time of engine cut-off is determined by sensors within the tanks that detect the falling propellant levels.]

[The S-II builders, North American Aviation of Seal Beach, California, more than the other Saturn manufacturers, were under great pressure to return as much thrust from as little weight as possible. As a result, the S-II is a triumph of exotic, lightweight construction and this extends to the strategies adopted to ensure full propellant depletion. As has already been discussed when the engine mixture ratio was altered, the need to completely consume propellants by managing this ratio was one part of the design strategy. The shutdown of the stage is another where the timing of the engine cut-off is determined by the quantity of propellant.]

[Each tank has five sensors that indicate when the propellant level in that tank is near exhaustion. When the IU receives two indications from the same tank, it sends commands to the engines to shut down. To make this system fail-safe and preclude the chance of an early shut-down from faulty sensors, this level-sense cut-off system is not armed until the stage's propellant gauging system independently measures that the levels are getting low. The call from Mike Collins is to let the crew know that the cut-off system is armed and they can expect shutdown any second.]

[Meantime, at 8:33.12 GET, the IU brings any rotation of the vehicle to a stop, an event known as "chi freeze". As with the separation of the first and second stages, unwanted vehicle rotation might cause the engine bell of the fresh stage to contact the interstage.]

000:08:35 Borman: The pogo's damping out.

000:08:37 Collins: Understand; pogo damping out.

000:08:42 Collins: Apollo 8, Houston. You look good for staging.

000:08:45 Borman: Staging?

Public Affairs Officer - "And the crew is advised they look good for staging, and Borman says, 'Same here.' We've got S-II cut-off."

[The crew are working off the top of page L-5 in the checklist. The S-II sends its cut-off signal at 8 minutes, 44.04 seconds, bringing the launch vehicle indicator lights on and marking the start of timebase 4 which will orchestrate staging and the operation of the S-IVB during its first burn. The LV lights are extinguished at staging.]

[Three quarters of a second after T4 begins, two ullage motors at the base of the S-IVB begin firing. Tenth of a second later, four retro motors mounted around the conical interstage ignite and the stages are cut apart by a shaped explosive charge around the base of the S-IVB. Another tenth of a second later the single J-2 engine at the base of the S-IVB begins its ignition sequence, announcing this to Frank by lighting lamp 1 of the launch vehicle indicator lights, in the top right position. It ignites 4¼ seconds after the start of T4 and takes about three seconds to get to full thrust. 65% thrust extinguishes the panel lamp in front of Frank. Typical thrust from this engine will be 901.6 kN (202,678 pounds), nearly exactly what was predicted. Note that the J-2 engine on this stage is not an uprated version.]

000:08:50 Borman: S-IVB ignition. [Pause.]

Public Affairs Officer - "We've got S-IVB ignition. Borman confirmed S-IVB ignition."

[The sequence of events for the first ignition of the single J-2 engine in the third stage is essentially the same as for the engines in the S-II (see earlier description). The main change is that the supercold fuel is allowed to flow through the walls of the thrust chamber to condition it for three seconds, instead on one, before the Start Tank discharges through the turbines, spinning them up in preparation for operation.]

[Although no close-up film exists of an S-IVB staging from an S-II, the following clip, kindly donated by www.footagevault.com, is often-used in documentaries, where it is often incorrectly used to portray the burn for the Moon.

The footage is from the AS-202 Saturn IB flight. The top of the cylindrical S-IB stage is visible in the foreground, distorted by the wide-angle lens to appear cone-like. This earlier model of the S-IVB stage sported three ullage motors instead of two used on the Saturn V. Their plumes can be seen as the stage departs.]

000:08:59 Borman: Guidance Initiate. [Pause.]

Public Affairs Officer - "And thrust looks good to us at 9 minutes into the flight."

[Once more, the IU begins guiding the vehicle and its payload to orbit as they gain the final 10% of the velocity they need. The two ullage motors are jettisoned from the bottom of the stage to save weight.]
000:09:06 Borman: Hey, Houston. How do you read? Apollo 8.

000:09:07 Collins: Apollo 8, reading you loud and clear.

000:09:09 Borman: Okay. We got Guidance Initiate.

000:09:12 Collins: Roger. Understand.

000:09:14 Collins: Trajectory and guidance are Go, Apollo 8.

000:09:17 Borman: Thank you. [Long pause.]

Public Affairs Officer - "We now have 89 percent of the velocity required, we're 920 [nautical] miles [1,704 km] downrange, and we're 9 minutes, 20 seconds into the flight. Flight Dynamics Officer [FIDO] says our altitude is nominal, which is the great conservative word for very nearly a perfect mission - as nearly as we can observe at this point."

000:09:49 Collins: Mark. Mode 4, Apollo 8.

000:09:52 Borman: Mode 4. Roger.

Public Affairs Officer - "Nine minutes, 50 seconds and we've just gone to what we call mode 4. If any trouble should develop now we would go ahead and burn into orbit with our Service Propulsion engine."

[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. It is called when the inertial velocity of the spacecraft reaches about 7,200 metres/second (23,600 fps). At about the same time, a Mode III abort is also enabled. Mode III, like Mode IV, entails using the SPS for separation, but it then is used for a retro burn and a quick return to Earth.]
000:09:57 Collins: Apollo 8, Houston. Your predicted cutoff, 11 plus 28. Over.

000:10:03 Borman: Understand; 11:28.

000:10:06 Collins: Roger. [Long pause.]

Public Affairs Officer - "We're now at 10 minutes, 10 seconds. We are at 103.7 nautical miles [192.1 km] above the Earth. Our velocity is at an even 24,000 feet per second [7,315 m/s], which is very, very close to orbital velocity, that's 95 percent of it and we're 1,200 [nautical] miles [2,222 km] downrange, which would put us a little bit out of Bermuda."

000:10:44 Anders: How do you read, Houston?

[Communications have been switched to work through the tracking ship Vanguard]
000:10:46 Collins: Reading you loud and clear.

000:10:49 Collins: Go ahead, Apollo 8.

000:10:50 Collins: Apollo 8, this is Houston. Over.

000:10:54 Borman: Loud and clear, Houston. Loud and clear, Apollo 8.

000:10:57 Collins: Roger. You're looking good, Apollo 8. [Long pause.]

Public Affairs Officer - "Ten minutes and 50 seconds and we've heard from Bill Anders for the first time, he simply said, 'How do you read, Houston?' He gets a 'looking good' comment from Mike Collins."

000:11:16 Lovell: HP is coming up...

000:11:21 Lovell: HP is plus... [Pause.]

Public Affairs Officer - "Eleven minutes, 20 seconds and we're hearing a little something from Jim Lovell, a reading from one of his meter gauges."

[The technical transcript gives the last two utterances as coming from Frank but it would make more sense to be coming from Jim. He is occupying the centre couch and has the task of monitoring the progress of the ascent by watching three computer displays right in front of him. He has entered Verb 82, Noun 50, which changes the display from velocity, altitude rate and altitude, to one that displays altitude, height of perigee (HP, its lowest point) and "Time of free fall". Time of Free Fall is the amount of time it would take, if the booster were to fail at that point, for the spacecraft to impact the Earth.]

[Up to now, the vehicle has not had enough speed to sustain an orbit. If their engines were to quit, they would reach an apogee but the path their vehicle is describing would, in simple mathematical terms, have a negative value for the height of perigee; in other words they would impact the surface of the planet on their way down to it. The computer does not display such hypothetical values. As they near the end of their burn, there comes a point when they do have enough velocity that HP would just become positive. If their engines quit then (and if the Earth had no atmosphere) they would coast around to the far side of the planet and just miss the ground. (Of course this cannot happen in real life for the Earth does have an atmosphere that would slow them down long before this hypothetical situation came about. It can almost occur around the Moon where there is no atmosphere and later flights would coast only nine miles above its landscape.)]

[As the last increment of velocity is added, Jim can see the HP figure begin to rise towards the desired value of 100 nautical miles. The crude 5-digit display would show this as 01000. Their apogee is already around that value and the S-IVB should cut-off when perigee gets there also.]

000:11:30 Borman: ...and we have SECO (S-IVB Engine Cut-Off).

000:11:33 Collins: Roger. SECO. [Long pause.]

Public Affairs Officer - "We have SECO says Frank Borman. SECO, and I would call it 11 minutes, 30 seconds - that will be an estimate - 11 minutes, 30 seconds. Our launch digital data shows our velocity now, 25,577 feet per second [7,796 m/s]."

[SECO is announced to the crew by LV lamp one coming on, and this event also begins timebase 5, a timebase that controls the operation of the S-IVB while in Earth orbit. Orbital insertion is defined as TB-5 plus 10 seconds and is marked by the LV lamp going out. The orbit they have achieved has a perigee of 181.5 km (98.0 nautical miles) and an apogee of 191.3 km (103.3 nautical miles) and being so low, has a period of 88 minutes, 10 seconds.

Graph showing ascent to orbit.

This diagram shows the profile of the planned ascent in a graph derived from the AS-503 Saturn V Flight Manual. The vertical axis is exaggerated by a factor of ten with respect to the horizontal axis. The major events (with actual times) are included.

Graph showing acceleration on the vehicle throughout its ascent to orbit.

This diagram is derived from the AS-503 Saturn V Flight Evaluation Report. It shows the g-forces experienced by the crew throughout the ascent. The major points are as follows:

  1. Launch. Apollo 8's first stage delivered more thrust than expected to a launch vehicle that was lighter than most of the later Apollo-Saturns. Therefore, compared to other missions, this graph starts off at about 1¼ g. For comparison, Apollo 15 left the launch pad at a more stately 1.1 g due to being a relatively heavy vehicle with a first stage that showed a slightly lower than expected thrust.
  2. S-IC inboard engine cut-off. The graph to this point shows how steeply the acceleration is rising, and gives a hint to how high it might have gone had the inboard engine not been cut-off.
  3. S-IC outboard cut-off. The overall thrust and acceleration rise have been reduced, reaching a peak of 4g at the time of S-IC cut-off.
  4. S-II ignition. The total thrust of the second stage is much lower than that of the first so, even after the disposed mass of the S-IC is taken into account, acceleration is correspondingly lower.
  5. Engine mixture ratio change. The ratio of LOX to fuel is changed from 5.5:1 to 4.5:1. A richer mixture reduces the thrust of the engines and thus the acceleration.
  6. S-II cut-off. Having reached about 1.9 g, the five J-2 engines are shut down.
  7. S-IVB ignition. There is only a single J-2 engine burning at this stage. As the ground weight of the remaining vehicle is about twice the thrust of the engine, the resultant acceleration is about half a g, gently rising for the duration of the burn to 0.7g.
  8. S-IVB cut-off and orbital insertion. The spacecraft and S-IVB are in earth orbit and weightless.]
000:11:58 Collins: Apollo 8, Houston. You are Go. Over.

000:12:01 Borman: Apollo 8 is Go. Thank you, Houston. [Pause.]

Public Affairs Officer - "The data now has been reduced and we show an altitude of 102.5 [nautical miles, 189.8 km], and the crew has been given a Go for all but they responded enthusiastically that they too, in fact, were Go."

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