Apollo 14

January 31, 1971: first day of mission.

Apollo 14 is NASA's fourth attempt to land astronauts on the Moon. Originally slated for the Littrow Crater in October 1970, the near-loss of Apollo 13 caused a delay of several months while accident investigation and spacecraft safety modifications took place to ensure the safety of the Apollo system in subsequent missions. The planned landing site of Apollo 13, Fra Mauro, was considered to be of such scientific interest that Apollo 14 was re-targeted for this area.

Apollo 14 is last of the "H" class of missions, which followed the landing of Apollo 11 (a G type mission, whose main purpose was to simply prove that you could do it). The H missions emphasized the ability to land the Lunar Module very accurately to a desired spot, and two space walks would be performed for the gathering of samples and the deployment of surface science instrumentation.

Despite what one could imagine, the woes of Apollo 13 did not cause the cancellation of the Apollo program. The original plan was always for ten manned landing missions, designated 11 through 20. Apollo 20 was cancelled under budgetary pressure in January 1970. In September 1970, the lunar program was curtailed further with the cancellation of two more missions, Apollo 15 and Apollo 19. The original Apollo 15 would have been an H class mission akin to Apollos 12-14, while Apollo 19 would have been a "J" class advanced mission, with a three-day lunar stay and the use of the Lunar Roving Vehicle. The new program deleted the fourth H mission and the last "J" mission, hence giving NASA three more lunar landings, subsequently redesignated as Apollo 15 through 17, and all flew as J type advanced missions.

The Prime crew of Apollo 14 is as eclectic as any of the groups of three men who were gathered for these missions.

The Commander is US Navy Captain Alan B. Shepard Jr. At 47 years old, a veteran of the Pacific theater of the Second World War, the oldest astronaut to fly yet, and the first American to go to space on board Freedom 7 in May, 1961. This lunar mission is his second spaceflight, however - Méniere's disease caused him to get dizzy merely while trying to stand up, and this ailment grounded Shepard. Experimental surgery in 1968 relieved Shepard's disease and, back to health, he wrangled himself the Commander's seat on an Apollo lunar landing. His long time spent deskbound meant, however, that Apollo management bumped him and his crew to fly Apollo 14, rather than Shepard's first choice of Apollo 13.

Command Module Pilot Stu Roosa, 38, comes from the ranks of the US Air Force, where he is a Major. This country-music listening father of four is a former test pilot and engineer at the Edwards Air Force Base, and became an astronaut in 1966. Roosa was seated at the CapCom's position during the tragic pad test of Apollo 1 in 1967 that saw the loss of the entire crew in a fire.

Rounding up the crew is the 41-year-old Lunar Module Pilot, Edgar Mitchell. With an advanced degree in aeronautics, US Navy Commander Mitchell is one of the three men with doctorates to walk on the Moon. (The others are Buzz Aldrin and Harrison Schmitt.) A sensitive and introspective character, his vision went beyond engineering and science into the esoteric as well.

Apollo 14 astronauts continued the tradition of eating steak for breakfast that had been established already during Mercury. It was probably a welcome break in the somewhat bland low residue diet they had to adhere to for before the mission.

Photographs of Guenther Wendt wearing a helmet with a swastika on it caused some consternation with NASA at the time. According to Shepard, the gag helmet was procured by friends who had visited the set of Hogan's Heroes.

The mid afternoon launch of Apollo 14 avoids the cool morning air of a Florida winter. A cold front stretches across northern Florida with scattered rain showers to the south. This shower activity is intensifying and moving slowly towards the Cape.

Apollo 14 will be starting today from Pad A at Launch Complex 39 at the Kennedy Space Center. This complex was built with 2 fully operational launch pads; in the expectation of a much higher launch rate than was ever achieved. Only Apollo 10 departed from Pad B at a particularly busy time in the Apollo program, leading up to the launch of Apollo 11. Every other Apollo/Saturn V launch, including Apollo 14, began from Pad A.

The timing of an Apollo launch to the Moon falls within certain 'windows' or periods of time which are influenced by daily and monthly factors. The daily restriction to the window is due to the rotation of Earth bringing the launch site to the correct relationship with the Moon's position in its orbit. The timing of this window allows enough of a parking orbit around the Earth before the boost to the Moon. The monthly factors are the lighting requirements at the landing site. The landing should take place in the early lunar morning so that the Sun will be behind the astronauts as they approach from their east-to-west orbit. A low Sun-angle will produce shadows on the lunar terrain which will allow the Commander to recognize landmarks as well as aiding speed and distance perception. Landing in the lunar morning also finds a comfortable medium between the -180°C chill of the lunar night and the +125°C heat of the noon sunshine. With a lunar day lasting 29.5 Earth days, the correct conditions for the landing only occur monthly.

The first launch window for Apollo 14 begins at 15:23, Eastern Standard Time, 31 January 1971, and lasts almost four hours. If technical problems or poor weather delay the launch, they must wait until March when they will have three opportunities at the beginning of the month and another three at the end.

Three hours before launch, the prime crew entered the spacecraft and once settled, they continue into a series of prelaunch checks. CDR (Commander), Alan Shepard, takes the left couch facing the major flight controls and the abort handle capable of giving the manual command to separate the spacecraft and begin an emergency landing. CMP (Command Module Pilot), Stuart Roosa occupies the center couch, facing the caution and warning panel above and ready to monitor the computer's display during the critical minutes of ascent. LMP (Lunar Module Pilot), Edgar Mitchell, takes the right couch and has the primary task of monitoring the electrical and environment systems during launch.

Astronaut Bruce McCandless II and a suit technician assisted the crew in getting onto their seats. At one point, there were actually five people onboard the three-man spacecraft.

Before the voyage commences, there are three sections to the CSM Launch Checklist to be followed. The lift-off configuration is set and verified by the backup CMP, in this case Ronald Evans, who checks that each switch, knob, adjustment and talkback indicator is correctly set for the arrival of the prime crew. The CSM launch Checklist systematically covers each of the 57 panels in the Apollo 14 CSM. The Apollo 15 checklist, which is quite similar to that of Apollo 14, contains 454 lines. Some panels are covered by a single line, while panel 2 on the main display console requires 78 lines.

Before the prime crew enters, the backup crew perfotrms a great many tasks to check up the vehicle for launch.

From now on until launch, the crew are seated on their couches, breathing 100% oxygen from the life support system, and go through their last checks with the aid of the Test Conductor over the radio.

The spacecraft/vehicle stack is designated AS-509, signifying that it is the ninth launch of the Apollo/Saturn V combination. As the Apollo spacecraft components come off the production line, they are also assigned serial numbers. Each had modifications which built on the experience gained from previous missions or which came from requirements of their particular mission.

Both the Saturn V launch vehicle, SA-509, and the Lunar Module, LM-8, received several small improvements. However, as the result of Apollo 13 near catastrophic failure, the Command and Service Module, CSM-110, gained numerous improvements to both prevent similar problems and to help the crew to better deal with any possible future inflight emergencies.

The Apollo 14 Saturn V stack now standing on the launch platform on Pad 39A is 110.6 metres [363 feet] high. With a take off mass of 2,950,867 kg [6,505,548 pounds], it will be some 1,731 kg [3,814 pounds] heavier than Apollo 13, making it the heaviest rocket yet launched by the US. At the bottom of the stack is the 42.1 m high [138 ft], 10 m [33 ft] in diameter S-IC first stage. With a dry weight of only 130,300 kg [287,300 pounds], now almost fully fuelled and ready to go, it weighs 2,283,309 kg [5,033,834 pounds]. The five F-1 engines clustered at the bottom of the stage provide a total of 33,379 kN [7,504,000 pounds] of thrust at lift-off (Flight Evaluation Report figures).

The second stage, S-II, is 24.8 m [81.5 ft] tall and 10 m [33 feet] in diameter. With a dry weight of 35,435 kg [78,120 pounds], it weighs 488,014 kg [1,075,887 pounds] at ignition. The five J-2 rockets motors clustered at its base produce a total of 5,187 kN [1,166,044 pounds] of thrust at the start of its burn.

For historical reasons, the third and last stage of the Saturn V is called the S-IVB and actually first flew as the second stage of the Saturn 1B launcher. It's 17.9 m [58.6 ft] high and 6.6 m [21.7 feet] in diameter with a dry weight of 25,030 pounds [11,353 kg] and a lift-off weight of 118,268 kg [260,736 pounds]. It's powered by just one J-2 engine with a rated thrust of 230,000 pounds [1,020 kN].

Listings of numerical data on the Apollo flights are available from Apollo By the Numbers.

The Saturn V launch vehicle is assembled, transported on, and launched from the Mobile Launcher. This structure consists of a base platform 48.8 by 41.1 metres [160 by 135 feet] and 7.6 metres [25 feet] high with a 13.7-metre [45-feet] square hole over which the vehicle is mounted. (The platforms would later be converted for use by the Space Shuttle.) Sprouting from one end of this platform is the LUT (Launch Umbilical Tower). This 116-metre [381-feet] tower bears nine swing arms which provide the ground crew with access points to the vehicle, and a wide range of services including fuel, LOX, hydraulics, electrical power and various gases for purging and pressurization. These arms are articulated so they can swing away from the vehicle to give it clearance as it rises, and to protect them from the rocket's white hot exhaust gases. The crew enter the spacecraft via the top, or ninth, arm, which carries an environmentally controlled room at its end. Known as the "white room", it covers the CM hatch until the crew is aboard. 43 minutes before launch, it is swung away from the spacecraft by 12°. Five minutes before launch, it completes its retraction to 180°, on the opposite side of the tower from the Saturn V.

The Flight Director holds immense power in the Apollo organization when he is on duty. The mission rules stipulate this very clearly. "The Flight Director may, after analysis of the flight, choose to take any necessary action required for the successful completion of the mission."

Six unmanned abort tests were performed to prove the Launch Escape System. One of them turned into a genuine abort when the Little Joe II launch vehicle began to break apart, triggering the Emergency Detection System and a subsequent firing of the LES.

If at anytime during the launch the LV suffers an unrecoverable problem, then the launch will be aborted and the CM with the crew onboard will be either safely returned to Earth or enter a safe orbit. There are several different abort modes available, each optimized for a certain phase of the launch. During the first part of the launch, the Mode 1A is in effect. At the start of a Mode 1A abort, the LVDC is told to shut down the F-1 engines and self destruct. At the same time, the CM separates from the SM and the rest of the LV, and the Launch Escape Tower (LET) pulls the CM to safety. The LET is capable of accelerating the CM at about 7g. At that rate it would be up to 100 km/h in well under 0.5 seconds and could do the standing quarter mile in 3.5 seconds, leaving even a top fuel dragster behind. In order to move the CM away from the launch pad and out over the Atlantic were it can make a safe landing, a pitch motor is used to tilt the CM/LET eastwards. About 11 seconds later, three seconds after the main LET motor burns out, a pair of canards (small airfoils) deploy from the top of the LET to help turn the CM around. While this is going on, the highly dangerous hypergolic propellants of the CM's RCS are automatically dumped overboard. After just 14 seconds, the LET's job is done and it is jettisoned with the help of a small rocket motor. The CM then deploys its parachutes and lands in the Atlantic.

At 42 seconds after lift-off, the abort mode is switched to 1B. Since the LV has already pitched over and is moving out over the Atlantic, the pitch motor is no longer needed during an abort. The rest of the Mode 1B sequence is very similar to a Mode 1A abort.

Dave Scott, Apollo 15 CDR, from 1998 correspondence with W. David Woods: "The 'abort' function was so very critical in terms of success/failure that many people thought there should be no crew function, and it should all be automatic (which in turn would introduce other more consequential failure modes). The most difficult simulations during the entire training process were 'launch aborts' - even more so than lunar landings (the landing itself was more difficult than launch, but not for 'aborts'). More crews 'bought it' during launch sims than any other area, by far!"

Each stage of the Saturn V launch vehicle has shaped explosive charges attached to its outer surface which, in the event of an abort, rupture the fuel and oxidizer tanks, dispersing their contents into the atmosphere rather than allow them to impact the Earth with dangerous loads still on board. The charge for the S-IC (the designation of the first stage) cuts a longitudinal breach in the fuel tank on the opposite side of the vehicle from that for the oxidizer tank so as to minimize their mixing during dispersion. Charges for the S-II (second stage) cut a 9-metre [30-feet] longitudinal opening in the hydrogen fuel tank and a series of lateral 4-metre [13-feet] ruptures in the squat LOX (liquid oxygen) tank. Those for the S-IVB (third stage) make two parallel 6-metre [20-feet] openings in the fuel tank and a 1.2-metre [4-feet] diameter hole in the LOX tank. These charges are fired only after the Command Module has separated from the launch vehicle. In such an instance, the Range Safety Officer will issue a coded, redundant self-destruct command on a special radio frequency that will detonate the onboard explosive charge.

The Instrument Unit (IU) is located on top of the third stage and just below the Spacecraft-LM Adapter which houses the LM. The IU is a ring about 0.9 m [3.0 feet] high and 6.6 m [21.7 feet] in diameter, and weighs a total of 2,043 kg [4,505 pounds]. This modestly sized part of the Saturn V turns it into an independent spacecraft in its own right, with a radio telecommunications system, an environmental control system for cooling all the onboard electronics in the IU, and the Saturn V's command and guidance system. It houses a digital guidance computer that received attitude and acceleration signals from an inertial measurement unit, and an analog flight control computer which receives commands from the guidance computer to give orders to the various engine pointing and control systems in the Saturn V stack.

At T minus 20 minutes; the Boost Preparation checklist deals with alignment of the X Stable Member Azimuth and checks that the various RCS (Reaction Control System) thrusters on the side of the Service Module (SM) are powered from the two main electrical busses in such a fashion to allow maximum RCS control, should one bus lose power.

The crew is checking the final status of the electrical system and the setup of the FDAI (Flight Director Attitude Indicator). This instrument, often called the "8-ball", is similar to the ball-style artificial horizon found on many aircraft and, likewise, allows determination of the spacecraft's attitude with respect to a desired frame of reference, usually this will be the IMU (Inertial Measurement Unit) though it may be the GDC (Gyro Display Coupler), a device which displays the spacecraft's attitude compared to independent body mounted attitude gyros (BMAGs). The FDAI will also show attitude errors and the rates of change of attitude.

Astronaut Ronald Evans, the back-up CMP, communicates with the spacecraft from the LCC (Launch Control Center), five kilometers from the launch pad. In Mission Control, Houston, astronaut Gordon Fullerton, the designated the CapCom for the first part of the mission, will start his duties when Apollo 14 clears the tower and control of the mission transfers from the LCC to Houston.

Dave Scott, A15 CDR, from 1998 correspondence with W. David Woods: "During launch, all transmissions between the spacecraft and MCC are made to and from the Commander and the CapCom, only. This is essential to maintain continuity, clarity, command, and control of the existing situation as well as potential and actual abort situations. In the spacecraft, just as in MCC, only one person communicates during time-critical situations."

Up until the time of the Apollo 12 launch, the mission rules covering weather minimums for a launch were a bit looser. Neither thick clouds nor rain were a problem if the winds were light and there was no lightning or indications of impending lightning. So Apollo 12 started in the rain and quickly climbed into heavy cloud. Just 36.5 seconds later, it was hit by lightning, and again 52 seconds into the flight. The master caution alarm sounded when most of the electrical and navigation systems were knocked off line. The Command Module Pilot, Richard Gordon, only slightly exaggerated when he looked at the caution and warning panel and reported that "all the lights are on." However, the Saturn V booster continued to run perfectly and shortly after reaching orbit, the crew managed to get everything back up and running. But the very successful ten day mission came uncomfortably close to a very dramatic end, less than a minute after it started. So NASA tightened the rules and Apollo 14 has to wait for the clouds to move past.

Both Deke Slayton and Al Shepard were selected in April 1959 as members of the Mercury Seven, the first class of NASA astronauts. In 1971, they were also the only ones left in active service with the space agency.

The weather has improved considerably. The cumulus congestus clouds that brought rain to the Cape have moved on leaving behind a broken layer of cumulus at 4,000 ft and scattered altocumulus at 8,000 ft. Its a humid 71° [22°Celsius]. The surface winds are light with 5 knots out of the west.

The Flight Plan indicates that in the CM, the five launch vehicle indicator lights are illuminated at T minus 4 minutes, 10 seconds. Throughout powered flight, these lights, arranged to resemble the pattern of the engine clusters on the S-IC and S-II stages, will provide the commander with cues about the progress of the boost and the status of the engines.

Some recording is available from the spacecraft communications in the minutes prior to launch.

The engine lights should have come on now, and Al is reporting this to the Launch Conductor.

With just one side to the conversation available, this is most likely a confirmation that the radio is still working.

According to the launch checklist, this should be Roosa noting that the computer is still running Program 2, "Gyrocompassing", which maintains a proper launch orientation for the guidance system stable platform.

Occupying a central position on the Main Display console is the DSKY, well within the reach of both the Commander and the Command Module Pilot from their seats. The Display and Keyboard (pronounced "dis-key") is the user interface through which the crew interacts with the Apollo Guidance Computer. The computer itself is not located inside the Main Display Console but rather sits on a shelf near the crewmembers' feet, in the Lower Equipment Bay. Among its many purposes is the determination of their position and their attitude with input from onboard instrumentation, the calculation of engine firings to alter their trajectory, and automatic control of the various thrusters to accomplish such a task. The crew communicates with the computer through a numeric keypad and a coded system of Verbs and Nouns, which each signify various tasks they can ask the computer to perform. The computer's responses are made on three seven-digit numeric displays, known as registers.

Program 2 will automatically initiate the computer's launch program, Program 11, upon receiving a signal from the Instrument Unit. Should this fail to happen, however, Stu Roosa is preparing to give the computer a manual launch confirmation by pressing the Verb button and then typing in "75". By leaving this on standby on the computer, he can initiate the launch guidance with a single press of the Enter key on the DSKY.

Ed Mitchell confirms here that the onboard tape recorder is running. Known as the DSE - Data Storage Equipment - it records onboard systems data and astronaut voice communications onto magnetic tape for the purpose of later replaying the data down to Earth via radio.

At T - 2 minutes, 15 seconds; glycol coolant is routed to bypass a radiator on the surface of the Service Module. The radiator will be heating up from aerodynamic friction during the passage through the atmosphere and therefore will not work as a cooling device. Coolant flow to the radiator will be reinstated once the spacecraft is in Earth orbit.

The CM batteries are connected across the two main power busses in the spacecraft to supply the extra power required during this particularly busy period. They also ensure that systems will continue to be powered in the event of a fuel cell failure during powered flight. This safety feature was used on Apollo 12. The batteries will be recharged later, once the mission settles down to a lower power regime.

In preparation for the higher noise level during launch, the volume of the radio in the astronauts' headsets is increased.

Al Shepard's final hands-on act is to press the GDC ALIGN button on the Main Display Console. This will transfer knowledge of their present attitude to the Command Module's backup attitude reference system.

A certain amount of knowledge about the anatomy of the engine will help to understand its function. A large combustion chamber and bell have an injector plate at the top - not unlike a giant showerhead - through which RP-1 kerosene fuel and liquid oxygen (LOX) are injected at high pressure. Above the injector is the LOX dome which also transmits the force of the thrust from the engine to the rocket's structure. A single-shaft turbopump is mounted beside the combustion chamber. The turbine at the core of the turbopump is at the bottom and is driven by the exhaust gas from burning RP-1 and LOX in a fuel-rich mixture in a gas generator. This way, once started, the engine produces its own operating power. After passing through the turbine, the exhaust gas continues into a heat exchanger, then to a wrap-around exhaust manifold which feeds it into the periphery of the engine bell. The final task for these hot gases is to cool and protect the nozzle extension from the far hotter exhaust of the main engine itself. The nozzle is the visible cone-shaped part of the engine and what people looking at it will probably perceive as the 'real' engine, although the combustion happens above it. The purpose of the nozzle is to direct the extremely hot, energetic gas molecules in the opposite direction to the spacecraft's desired direction - hence generating the actual propulsion. Also above the gas-driven turbine on the same drive shaft is the fuel pump with two inlets from the fuel tank and two outlets going, via shut-off valves, to the injector plate. A line from one of these 'feeds' supplies the gas generator with fuel. Fuel is also used within the engine as a lubricant and as a hydraulic working fluid - This keeps the weight down. Before launch, RJ-1 ramjet fuel is supplied from the ground for this purpose. And then at the top of the turbopump shaft is the LOX pump with a single, large inlet in-line with the turboshaft axis. This pump also has two outlet lines, with valves, to feed the injector plate. One line also supplies LOX to the gas generator. The interior lining of the combustion chamber and engine bell consists of a myriad of pipework through which a large portion of the fuel supply is fed before it goes into the actual combustion chamber to be burnt. This cools the chamber and bell structure while also pre-warming the fuel.

The last important component to note is an igniter, containing a cartridge of hypergolic fluid with burst diaphragms at either end, and located in the high pressure fuel circuit. It has its own inject point in the combustion chamber. Upon ignition command a mixture of triethylboron with 10-15 per cent triethylaluminium is released into the combustion chamber.

The function of a hypergolic igniter is rather simple. A great deal of heat is needed to light the RP-1 and LOX propellant that is being pumped into the engine. The mixture of triethylboron and triethylaluminium is hypergolic with oxygen, meaning that once they come in contact with the LOX inside the combustion chamber, they will combust violently. This will provide the starting 'fire' to start the engine properly.

Every liquid fuel rocket engine on the Saturn V-Apollo stack, except for the F-1 and J-2 engines, employed hypergolic propellants. This was done for the ease of storage and the ensuing reliability of function.

At T - 17 seconds, the Saturn's inertial guidance system starts to compute vehicle attitude data based on its own (internal) sensor data.

Service arm 2 is retracted. It provides power and environmental control to the S-IC stage.

Just six seconds before lift-off, the five F-1 engines will start their ignition sequence. First the center engine, then 0.2 seconds later, two of the outboard engines, and finally another 0.3 seconds later, the last two outboard engines. At T minus 1.5 seconds, they will all reach their full rated thrust and start to burn fuel at a total rate of some 13 metric tons a second. In the few seconds between engine start and hold-down arm release, they will consume about 40 tons of propellant.

The ignition sequence of an F-1 engine is a complicated affair with many interrelated events happening almost simultaneously. At T minus 8.9 seconds, a signal from the automatic sequencer fires four pyrotechnic devices. Two initiate combustion within the gas generator while another two cause the fuel-rich turbine exhaust gas to ignite when it enters the engine bell. Electric wire links are deliberately burned away by these igniters to generate an electrical signal to move the start solenoid. The start solenoid directs hydraulic pressure still provided from the ground supply to open the main LOX valves. LOX begins to flow through the LOX pump, starting it to rotate, then into the combustion chamber. The opening of both LOX valves also causes a valve to allow fuel and LOX into the gas generator, where they ignite and accelerate the turbine connected to the gas generator's output. Fuel and LOX pressures rise as the turbine gains speed. The fuel-rich exhaust from the gas generator ignites in the engine bell to prevent backfiring and burping of the engine. The increasing pressure in the fuel lines opens another valve, the igniter fuel valve, letting fuel pressure reach the hypergol cartridge which promptly ruptures. Hypergolic fluid, followed by fuel, enters the chamber through its own ports where it spontaneously ignites on contact with the LOX already in the chamber.

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

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

0.3 seconds after range time start, the so-called first motion is detected when the Saturn V unseats from the launch pad. This starts the clock, and the mission officially begins

"Launch commit" refers to the fact that as soon as the engines fire and the Saturn V space vehicle moves even a fraction of an inch, the launch must happen.

At one second to lift-off, the five launch vehicle indicator lights in the spacecraft will go out, telling the crew that the thrust is OK and the hold-down arms are about to release.

The stack is held onto the pad two ways. Four hold-down arms clamp the base of the S-IC, each with a force of 350 tons, anchoring the vehicle until full thrust is confirmed. A pneumatic device collapses the lever linkage to allow the arm to rise. If any one of these arms fail to release within 36 milliseconds of the expected time, an explosive device will be triggered to force the release of the arm. Additionally, a number of controlled-release mechanisms (up to 16, depending on the mission) 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.

With a line that has come from crews since Shepard's first flight for America, he is again confirming that the MET (Mission Event Timer) has begun counting. The timer receives a signal that the vehicle has lifted off, begins incrementing and the Flight Plan calls for this to be reported.

All Saturn V launches were extensively photographed from every conceivable angle and KSC-71PC-106 is a fine shot of Apollo 14 at lift-off.

The Saturn V accelerates off the pad very gently at about 1.7 m/s². At that rate, it would take it about 16 seconds to reach 100 km/h [62 mph]. At good car can reach 100 in 10 seconds, the best electric cars can do it in less than three.

On this, and all Saturn V launches, the stack can easily be seen leaning away from the LUT as it ascends from the launch pad. This yaw, begun 1.35 seconds after lift-off, maneuvers the vehicle 1.25° from vertical in a direction away from the tower to ensure clearance in case a gust of wind pushes it back or a swing arm doesn't fully retract. Then nine seconds into the flight, almost as the rising rocket clears the tower, the stack is brought vertical again. To those who were not prepared for it, this fully intended yawing of over 110 metres of metal, filled to the brim with propellant, could cause some consternation. The launch checklist for the CSM calls for the initiation of this yaw to be reported to the ground but the transcript does not carry it.

Once the launch vehicle begins to rise, even fractionally, it cannot safely settle back onto the pad. The LV is committed to launch 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. The first two centimeters of travel trigger the release of the umbilical connector plates which in turn triggers retraction of the arms.

The Saturn V is at its most vulnerable during this part of the launch. Numerous, otherwise correctable problems, could send the LV crashing into the tower or falling back onto the pad. Both events would result in the uncontrolled breakup of the launcher and the release of 5,700,000 pounds [2,600,000 kg] of propellant. Clearing the tower leaves the worst of these problems behind. Even if an engine failed, the LV has already burned off enough propellant to be able to continue to climb. Soon it would be able to resume acceleration and continue towards orbit.

About 10 seconds after lift-off, the launcher rises above the tower. This very significant event is reported to the crew.

Dave Scott, A15 CDR, from 1998 correspondence with W. David Woods: "The 'Tower Clear' call is made by the Launch Director - this is a very critical transmission in terms of both safety and responsibility: (1) safety, of course, at the instant of the call, and by visual observation of the Launch Director, the Saturn is clear of a major obstacle (such failures as an engine hardover would probably be catastrophic prior to Tower Clear); and (2) this is the official transfer of mission responsibility from the LCC (Launch Control Center) at the Cape (the Launch Director) to the MCC in Houston (the Flight Director). The Flight Director would have acknowledged this over the comm link with the Launch Director. This is very important topic, as few people seem to realize the significance of the call."

MILA (Rev-1)

For the first part of the first revolution (REV), the spacecraft will be tracked by and communicate through the Merritt Island Launch Annex (MILA) ground station.

Control of the mission has been transferred to Mission Control in Houston, Texas. Gordon Fullerton assumes the role of CapCom from Ronald Evans. The role of Public Affairs Officer has also transferred to Houston.

Shepard has reported that the LVDC's guidance program has begun to roll on to the flight azimuth of 75.558° and to pitch downrange.

Seated on the left crew couch, Al Shepard has a clear line of sight to several instruments that allow him to monitor the automatic Saturn V ascent. At the center is the FDAI - Flight Director/Attitude Indicator, also known as the 8-ball, which shows spacecraft attitude. Up on the left corner is an accelerometer that displays the present g level. To the right of the FDAI are the engine status light. Below, a round gauge called LV alpha/SPS pc displays the angle of attack for the Saturn V. The final primary instrument is a series of gauges that measure the pressure levels in the various Saturn V stages.

Gordon Fullerton became a NASA astronaut in 1969 after previously training for the Air Force's since-cancelled Manned Orbital Laboratory (MOL) military space station.

Shortly after clearing the tower, the launcher briefly continues its vertical climb before starting its roll program. The launch pads at Launch Complex 39, Kennedy Space Center, are aligned to the points of the compass with the LUT north of the vehicle. Therefore, at launch, the vehicle's frame of reference, its azimuth, is 90° east of north and the purpose of this roll maneuver is to align the launch vehicle with the desired trajectory, with an azimuth 75.558° east of north, before it begins to pitch over. These maneuvers place the spacecraft into a "heads down" attitude.

The LV has finished rolling onto the flight azimuth of 75.558°. Prior to launch, the guidance system's inertial platform was prealigned to this bearing. By rolling around its long axis, the rocket has aligned itself with the platform so from this point on, it merely has to tilt around its pitch axis.

JSC-71-18398 shows the vehicle well into its vertical flight.

The abort mode has switched from the initial Mode 1A, low altitude abort, to the Mode 1B, medium altitude abort.

Not only is the cabin pressure now being allowed to fall from its sea level value of 14.7 psi [1 bar] to the flight value of about 5 psi [0.3 bar], but the the nitrogen/oxygen mixture is being replaced by pure oxygen. The crew has been breathing pure oxygen since before they headed to the pad to avoid any possibility of nitrogen gas forming bubbles in their bloodstream as the pressure drops.

At 68 seconds into the flight, the spacecraft breaks the sound barrier at Mach 1.

The aerodynamic forces acting on the launch vehicle have been rising as the vehicle gains speed. However, the air around it is thinning rapidly with its increasing altitude. The interaction of these two changing values results in a maximum dynamic pressure on the vehicle's skin at 1 minute, 21 seconds; at a speed of about Mach 1.6 and an altitude of 12.3 km. This moment of maximum dynamic pressure is also often described as Max Q.

During the ascent through the atmosphere, it is important that the rocket points in the direction it's flying. Flying sideways generates lateral (sideways) aerodynamic forces that can overload the structure. To avoid this, the first stage, and the start of the second stage, are flown according to a carefully calculated, preprogrammed tilt schedule.

Mode IC is the high altitude LET abort. Since they are now above most of the atmosphere, after the LET pulls them away, they need to jettison the tower and use the CM's thrusters to turn the CM around in order to reenter the atmosphere in the correct BEF attitude.

As the S-IC nears the end of its burn, Stuart Roosa has inhibited the EDS (Emergency Detection System) with a switch directly below the computer keypad. The EDS is only needed for flight through the thickest part of the atmosphere where high aerodynamic forces and the structural load they impart to the vehicle could cause loss of control to turn catastrophic too quickly for the crew to react in time. With EDS switched off, any required aborts must be initiated by the crew.

The acceleration is already up to about 3.6g and starting to build rapidly. Having already burned about 1,800,000 kg [4,000,000 pounds] of propellant, the LV now only weighs about 1,150,000 kg [2,500,000 pounds], less than 40% of its lift-off mass. Also the F-1 engines are now running in very rarefied air allowing them to produce a total of 39,600 kN of thrust, 17% more than the 33,800 kN at sea level. In order to reduce this acceleration buildup and the resulting structural loads, the center engine of the S-IC is shut down 29 seconds before the rest of the engines.

Another effect of the reduced air pressure on the S-IC is visible on movie coverage of the launch as the base of the vehicle appears to be progressively consumed by the conflagration. Near the ground, the plume is constrained by air pressure into a narrow flame extending rearwards. With decreasing air pressure, the hot gases are able to expand into an ever widening plume. Towards the end of the S-IC's flight, the air is so thin and the slipstream so negligible that a small amount of exhaust is able to expand forwards up the side of the rocket's structure giving the appearance, on TV coverage, of the rocket's base being consumed by the plume.

The thrust of the S-IC had been compressing the LV like a giant spring. At the moment of cut-off, the structure recoils with some force.

Mitchell, from the 1971 Technical Debrief - "When the outboards cut-off, as we had previously been briefed and as previous crews had discussed, there was a sharp unloading. I expected to be thrown against the instrument panel, and I had my hands out to brace against it. But it was not as much as I expected. I do recall feeling the unloading reverberate through the spacecraft in several pulses."

The spent S-IC has lifted the vehicle to about 67 km; above most of the atmosphere. The S-II will continue the ascent to the orbital height of about 191 km, as well as accelerating the vehicle to about 90% of the required orbital velocity.

Having done its job, the the S-IC separates and is retarded by eight retrorockets built into the conical faiings near the bottom of the stage. In just a few seconds the five J-2 engines on the base of the S-II stage will ignite.

The S-II stage carries five J-2 uprated engines which burn LH₂ and LOX to produce up to 230,000 pounds [1,020 kN] thrust each.

For the initial three-quarters of the burn, the J-2s are run at a mixture ratio of 5.5:1, LOX to LH₂. This produces a high thrust, thanks to the larger amount of oxygen feeding the fire so to speak. At a point determined by the LVDC, the mixture ratio will be altered to 4.8:1.

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

The ASI (Augmented Spark Igniter), fed with propellant and mounted to the injector face, provides a flame to initiate full combustion. Valves are provided to bleed the cryogenic propellants through the supply system well before ignition to chill all components to their operating temperatures. Otherwise the relatively warmer components would cause gas to be formed which would interfere with the engine's use of propellant as a lubricant in the turbopump bearings.

Attached to the engine is a spherical tank of gaseous helium which is located inside a larger tank of gaseous hydrogen fuel. This is the Start Tank. The high-pressure helium from the tank provides pneumatic operating power for the engine's valves while the high pressure hydrogen spins up the turbopumps before the gas generator is ignited. A PU (Propellant Utilization) valve on the output of the LOX turbopump can open to reduce the LOX flowrate. This adjusts engine thrust down to 890 kN (200,000 pounds) during flight to optimise engine performance. Although this is technically a way to throttle the engine, it is not considered a truly throttleable system.

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

The S-II stage's role in a Saturn V stack is unglamorous, yet crucial. While lacking the brute force of the S-IC stage required for takeoff or the multitude of functions available for the S-IVB third stage that will eventually place the crew in their translunar trajectory, the S-II stage is an extremely fine tuned, high performance machine using the still-exotic combustion of liquid oxygen and hydrogen. During its operation, it will take the Apollo 14 stack from 67.9 kilometers to 188.2 kilometers of altitude and accelerate the spacecraft from 2,744.6 m/s to 6,985.2 m/s.

The interstage ring or skirt has been jettisoned. The dual plane separation process that started with the shut-down of the outboard S-IC engines is now complete.

The reason for the dual plane separation is to reduce the possibility of the interstage skirt contacting the engine bells upon departure. The first cut is just above the S-IC forward skirt, leaving the interstage behind still surrounding the engines. Any unintended rotation of the S-IC is unlikely to do damage. Thirty seconds are then allowed for the S-II to settle into its flight before the skirt is jettisoned and the stage smartly accelerates away, leaving it behind before any inherent rotation it might have can threaten the engines.

The skirt separation is a critical event. If it does not separate properly, not only can the partially skirt cause engine damage, its dead weight will mean that the Saturn V does not have sufficient fuel for a lunar mission.

These two videos, kindly donated by Stephen Slater, show the separation of Apollo 4's S-IC stage from its S-II across both planes. They were taken using film cameras mounted on either side of the S-II thrust structure, upper and lower. The cameras were ejected and, having parachuted into the ocean, were located by radio.




Both videos are presented here at 23.976 frames per second, a standard film frame rate. However, they were shot at about 4 times this rate, probably 96 frames per second. Therefore, although in real time 30 seconds elapse between each plane separation, the same events in these versions are separated by two minutes.

Should this footage appear familiar to you, it is not a mistake. Due to the spectacular nature of the film, and the fact that it is one of a kind record of these events, these clips have been a part of countless documentaries about spaceflight. They usually represent a mission other than the original Apollo 4, however! Later missions did not carry the camera equipment so as to maximize the payload capacity of the Saturn V, where every pound launched mattered.

A single, small, solid-propellant motor near the top of the tower fires for one second, jettisoning the entire LES (Launch Escape System) and the Boost Protective Cover. With the BPC gone, the astronauts can now look out of all of their windows. The LET and the BPC will reenter and burn now.

With the tower gone, during a Mode II abort, the whole CSM separates from the LV and uses its RCS thrusters or even the SPS engine to move safely away. The CM then separates from the SM and makes a normal landing.

This line comes from the launch checklist items:

GLY EVAP STEAM PRESS - AUTO
GLY EVAP H2O FLOW - AUTO

They tell Mitchell, who is currently looking after the environment systems, to let the automatic systems control the water flow to the evaporator which is used to remove excess heat from the CSM's glycol cooling loop. However, the checklist doesn't say that these items should be reported. Even if it did, Shepard would do the reporting. It appears that Mitchell accidentally hit his push to talk button while reading these items. Instead of calling needless attention to this very minor error at a critical time in the mission, Fullerton handles it very coolly.

Until now, the IU has been following a predetermined trajectory to minimizes lateral aerodynamic loads without using (i.e. feeding back) any information about current position or velocity. This is called "open loop" control since the results of the last guidance command are not being fed back to help compute future commands. The IU now begins the IGM (Iterative Guidance Mode) which closes the guidance loop by using the difference between where it is and where it wants to be to correct its guidance commands. Open loop guidance can put a spacecraft into orbit, but closed loop guidance has a much better chance of placing it into exactly the desired orbit.

At over 100 kilometers in attitude, they have passed the Kárman line, the arbitary border between space and 'not yet space', meaning that Stu Roosa and Ed Mitchell are now space-travelling astronauts.

Shepard is clearly in charge, ensuring his crew keep their eyes on the job despite the fantastic sights opening to his crewmates for the first time.

To assist the crew in interpreting the figures from their instruments, a cue card is provided that shows the expected values for various displays during each part of the ascent. The most important of these numbers are the V_I - their velocity, the rate of climb (known as the H-dot) and their altitude, listed as H. The leftmost column labeled "DET" signifies the amount of time since lift-off. This way, they can make sense of what they see on their computer display and the other instruments, and relate them to the expected values. A major deviation from them is certainly an indication of trouble. For now, Stu Roosa's remarks suggest that their ascent is very much as predicted by pre-mission computations.

It is interesting to note that the V_I value for their inertial velocity does not start to increment from zero, but starts with 1,341 feet per second, which is velocity imparted on them by the rotation of the Earth itself!

Comm break.

Although the IU's LVDC controls the Saturn V during the launch, the CMC monitors the ascent and displays the flight path and attitude information on the DSKY and the FDAI. If significant and increasing deviations between the current and the expected parameters arise, the astronauts have the ability to take over the LV and manually fly it into orbit using the same hand controllers that they will later use to fly the CSM. The astronauts spent a fair amount of time practicing this not only because it is an important capability, but also because as test-pilots, they relished the thought that they might get to fly the mightly rocket into orbit instead of just riding on it.

Retrofire is Mission Control's Retrofire Officer, often just called Retro. He not only computes the re-entry into Earth's atmosphere at the end of the mission, but also continuously computes abort maneuvers which would quickly return the astronauts to Earth if necessary throughout every stage of the mission. He is saying that if they aborted now, they would land past an area of bad weather in the Atlantic.

This announcement means that should the S-II stage fail to burn to completion, they will be able to reach a stable Earth orbit using the S-IVB third stage. The resulting maneuver would be known as COI or Contingency Orbit Insertion. This would mean the cancellation of a lunar mission, however.

This method of relating GET (Ground Elapsed Time) is a common shorthand used throughout the mission. To some extent, the context determines whether the first figure is hours or minutes. These times are 0 hours, 8 minutes, and 39 seconds; and 0 hours, 9 minutes, and 16 seconds.

Each propellant tank in the S-II has five sensors near the bottom which signal when they are uncovered by the draining liquid. When it receives two such signals from the same tank, the IU computer begins a sequence which will lead to engine cut-off. However, this engine cut-off system is not armed until the level has fallen below a certain threshold to reduce the possibility of an erroneous, premature cut-off. Fullerton is telling the crew when Mission Control expects the cut-off system to be armed, based on current consumption, and when the engines will subsequently be shut down.

The crew are activating the gimbal motor system for the CSM's SPS engine in case it is needed to achieve orbit after an LV failure. There are two redundant motors for both the pitch and the yaw axis. These motors need to be turned on, one after another, with a short pause between each activation. This sequence will be repeated often during the flight.

Now that the SPS gimbal motors have been exercised, the engine nozzle needs to be aimed so that as near as can be worked out, the thrust will act through the spacecraft's centre of mass. This is achieved with a set of thumbwheels, the Gimbal Position Indicators.

They can now still go to the Moon even if one engine in the S-II stage shuts down prematurely. This utterance by Stu may be in light of an incident during Apollo 13's ascent, when the S-II's centre engine shut down early due to severe vibration. The other engines were able to burn for longer, using up the spare propellant. Apollo 13 managed to head for the Moon despite this problem. Apollo 14 is less likely to suffer from the same vibration problems because their source was located and altered to detune its tendency to resonate.

Should the S-II cut-off early, the S-IVB now has the ability to place itself, the CSM and LM into a safe orbit. However, the crew must switch to an alternate mission. There are numerous alternate missions depending on the nature of the anomaly leading to the alternate mission and the status of the spacecraft. The scope of these missions varies from quickly abandoning the LM and staying in Earth orbit, to flying to the Moon, but not landing. For this reason and because training for the primary mission was so demanding, the crew probably spent little time on these alternate missions.

As with the first stage, the center or inboard engine of the S-II is cut-off early; in this case, to minimize the vehicle's pogo oscillation tendencies late in the burn. The inboard engine cut-off was at 7:43; 1 minute, 36 seconds before the outboard engines.

At 7:53, the PU (Propellant Utilization) valves open, reducing the LOX flowrate and therefore the mixture ratio to the engines from 1:5.5 to 1:4.8. This results in a thrust reduction from 925,000 pounds [4,110 kN] to 776,000 pounds [3,450 kN], a drop of 16%, but with about a 1% improvement in specific impulse (fuel efficiency). Despite the reduction in thrust, during the technical debriefing, Roosa twice said that "It just felt like you cut in the AS (afterburner) on the stack."

The PU system was originally designed to change to a lower mixture ratio based on measurements of the declining propellant levels to ensure that both the fuel and the oxidizer were depleted at the same time. This was a 'closed-loop' arrangement. However, mathematical analysis showed that, given the many variables that affected the chances of achieving simultaneous depletion, it was better simply to change to the lower MR once a predetermined velocity had been reached.

Fullerton is informing the crew that the "level sense arm" signal has been sent to the IU. The engines will be shut down once two probes in one of the tanks have been uncovered by the dwindling propellant. This system wasn't armed (activated) until late in the burn so that if there was an erroneous cut-off, there would be sufficient margin in the S-IVB for the Translunar Injection burn. They can expect cut-off shortly.

Pogo, a humorous name for a very serious problem.

In a Mode IV abort, the SPS engine is now capable of putting the CSM into orbit. Although far short of going to the Moon, at least the astronauts get a much wider choice of when and where they land instead of just being dropped somewhere in the Atlantic.

The outboard engines cut-off at 9:19. One second after outboard cut-off, the S-IVB separates from the S-II. The start sequence of the S-IVB's single J-2 engine begins a tenth of a second later.

Unlike the earlier staging, the S-II separation occurs at just a single plane, the top of the truncated-cone interstage which joins the S-II and S-IVB. With only one engine at the aft end of the stage, there is plenty of clearance between it and the edge of the interstage below.

It's interesting that although Mitchell had been expecting the S-IC cut-off to be much more dramatic than the S-II cut-off, he reported just the opposite in the technical debriefing. Perhaps he had been prepared for a violent S-IC cut-off, but was surprised when the S-II cut-off was still powerful enough to send him "forward on the straps", but without the reverberations of the first stage cut-off.

Mitchell, from 1971 Technical debrief: "There was a great deal of debris, ice, and pyro-function noise associated with it (S-II separation). It was a very loud and messy separation in the sense that there was quite a bit of debris thrown around."

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 J-2 start). 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 of one, before the Start Tank discharges through the turbines, spinning them up in preparation for operation.

This well-known footage shows the separation of an S-IVB second stage from an S-IB first stage during the ascent of AS-202, a Saturn IB launch vehicle, on 25 August 1966. It is the only time an S-IVB was successfully filmed separating and igniting. What distinguishes this stage from an S-IVB used on a Saturn V was that this type had three solid-fuelled ullage motors mounted on its aft skirt whereas a Saturn V's S-IVB only had two. The three exhaust fans emanating from these three motors are very apparent.

After the film was exposed, the camera was ejected and parachuted into the ocean, to be located by radio and recovered.

H-dot is the climb rate or rate of change of altitude with time. Now that they have almost reached their orbital altitude, the climb rate is dropping quickly. From now on, the S-IVB mostly works to increase their velocity.

That's 2,000 feet per second [610 m/s] to go to reach their planned orbital velocity.

Now only 1,500 feet per second [460 m/s] to go.

This first burn of the S-IVB was 4.1 seconds shorter than was predicted. This was due mostly to slightly better than expected performance of the S-IVB.

Even before their orbital insertion, the S-IVB and its J-2 engine begin first preparations for their upcoming Translunar Injection burn. The engine's start tank is filled with liquid and gaseous hydrogen during the last 60 seconds of the burn. It will slowly begin to gain the pressure needed for a restart of the engines by allowing the temperature inside the tank to increase through heat leak as the sunlight warms it, and hence causes the supercooled liquid to warm also, increasing its pressure. A minimum of 80 minutes is required for the pressure in the start tank to rise sufficiently for the restart. This minimum wait will also let the other components to cool down after the hardships of the first S-IVB burn.

Power is removed from the servomotors that aim the SPS engine nozzle, known as thrust vector control. This had been enabled in case the SPS engine had been needed in an abort situation. They are a very high-power item and the crew does not want them to be operating when not required.

The crew is now experiencing prolonged weightlessness for the first time in the mission after a ride that has subjected them to loads of almost 4g. See G-loads for a graph of the G loads during the launch. This is not the highest that will be experienced during the mission. Entry through the Earth's atmosphere decelerates the Command Module by about 6.5g.

At 000:12:40 GET, a propulsive venting of the liquid H₂ begins by opening a valve on the S-IVB stage. This both keeps the propellants settled in their tanks and prevents the tank from pressurizing too much due to the heat leak. The valve will be closed before the second S-IVB burn to build up pressure instead of relieving it.

Al has apparently keyed in Verb 82 Enter on the DSKY to display the onboard computer's estimate of the low and high points of their orbit.

SECS is the Sequential Events Control System. It looks after the complex sequencing of events like the operation of the Earth Landing System (parachutes) or the CSM's separation from the launch vehicle. It had been active in case an abort had required it.

Not only do they turn off the sequential electronics with the switches, but Al also pulls the circuit breakers.

As well as the primary guidance system with its gyroscopically-stabilised platform, the Command Module had a secondary system that had its own gyros for attitude determination. By being affixed to the spacecraft structure (as distinct from being on an isolated platform), these gyros were known as 'body mounted attitude gyros' or BMAGs.

Al is referring to the two Cabin Pressure Relief valves. The purpose of these valves is to maintain the cabin at a safe pressure during flight, as well as for equalizing pressure during ascent and entry. The Normal position allows them to vent excessive pressure from the cabin but prevents them from opening fully to prevent sudden loss of cabin pressure due to a malfunction in one of the valves.

On reaching orbit, the APS (Auxiliary Propulsion System, the S-IVB's own attitude control system), will continue to control the attitude of the stack, making sure that it flies in a level attitude relative to the local horizon. This requires that it set up a slow pitch rotation at a rate which matches the vehicle's rate of rotation about Earth (therefore called 'orbital rate' or 'orb rate') so that throughout the orbit, the same side keeps facing Earth. In this case, the crew is in a 'heads down' attitude and the vehicle is pointing in the direction of travel.

There are a number of interrelated reasons for the orb rate maneuver during Earth parking orbit. They entered orbit nearly "pointy-end-forward" and will boost to the Moon (the TLI or Translunar Injection burn) in a similar attitude. Staying in that same attitude, relative to the local horizontal, avoids excessive attitude changes. Also, this attitude presents a small cross section to the extremely thin atmosphere that the spacecraft and S-IVB is still moving through, and this minimizes friction-induced heating. Also, the small thrust resulting from the venting of LH₂ pushes the vehicle in the same direction as orbital motion. Finally, keeping the CSM in a 'heads down' attitude ensures that the spacecraft's optics, mounted on the opposite side of the Command Module from the hatch, are facing towards the stars so Stu can sight on them during the upcoming navigation tasks.

Comm break.

CANARY (Rev-1)

Tracking and communications has been taking over by the Canary Island ground station off the western coast of Africa.

Long comm break.

Very long comm break.

Carnarvon is the tracking station in Western Australia. Apollo 14 now slips beyond NASA's capacity to receive real-time data and communications.