Probably one of the more overlooked Apollo missions was that of Apollo 9 launched on March 3, 1969. Coming just a couple of months after the historic voyage of Apollo 8 to the Moon, its mission in low Earth orbit did not seem all that spectacular and generated little public interest even at the time. But this mission, which tested the Lunar Module (LM) in flight with a crew on board for the first time, was a vital stepping stone for the Apollo 11 mission four months later making the successes of this and subsequent Apollo lunar landing missions possible.

Apollo’s Lunar Module

The Apollo lunar missions actually involved two separate spacecraft: The Command-Service Module (CSM) to support the crew during all phases of the mission save for the actual lunar landing itself which would be left to the purpose-built Lunar Module (LM). Initial flights of the CSM used an early Block I variant built by North American Aviation (which merged with Rockwell in March 1967 and subsequently with Boeing 29 years later), which was essentially a prototype meant for test flights in low Earth orbit for the purpose of verifying the basic CSM design. Lessons learned from constructing and flying these versions would be then incorporated into the improved Block II CSM which would include all of the systems needed to support a lunar landing mission.

The second Apollo spacecraft, the LM with Grumman Aircraft as the prime contractor (which is now part of Northrop Grumman after a 1994 merger), was designed to land a pair of astronauts on the lunar surface and return them back to orbit and the waiting CSM after a couple of days of exploration. The LM was a true spacecraft in the sense that it was designed to operate only in the vacuum of space resulting in a lightweight design with a distinctive angular shape incapable of surviving atmospheric flight. The LM consisted of two stages: the descent stage and the ascent stage. As the name implies, the descent stage was used to make the descent from lunar orbit to the surface. It included landing gear to support the LM on the lunar surface, a supply of consumables for the crew and the LM descent propulsion system (DPS) along with its supply of hypergolic propellant. The DPS employed a throttleable, pressure-fed engine built by TRW which burned Aerozine 50 (a 50-50 mix of hydrazine and unsymmetrical dimethyl hydrazine or UDMH) and nitrogen tetroxide to generate up to 46 kilonewtons of thrust.

The LM ascent stage housed and supported the astronauts inside of a pressurized cabin with a habitable volume of about 4.5 cubic meters. In addition to life support equipment and supplies for the crew, the ascent stage included a pressure fed LM ascent propulsion system (APS) as well as tanks to hold its Aerozine 50 and nitrogen tetroxide propellants. Jointly developed and built by Bell Aerospace and Rocketdyne, the main engine of the APS produced 16 kilonewtons of thrust to lift the LM ascent stage off of the lunar surface (with the descent stage now acting as a launch platform) and return the LM crew to lunar orbit where it would rendezvous and dock with the CSM for the return home. The LM ascent stage also included a reaction control system (RCS) to provide attitude control for the LM during flight and allow it to perform small maneuvers required during rendezvous and docking operations. The RCS consisted of 16 440-newton engines divided into four quads evenly spaced around the midsection of the stage. The LM stood about seven meters tall with its landing gear extended and would have a fully loaded mass of about 15 metric tons in its initial lunar landing flights.

By late 1966, NASA’s plans for the upcoming Apollo test flights had been set. First up would be the AS-204 mission which would make the first orbital test flight of the Block I CSM with a crew of three on board. The feat would be repeated with a second Block I CSM orbital test flight designated AS-205. Next up would be AS-206 which would be the first unmanned test flight of the LM. Since the Saturn V would not be making its first of up to three planned test flights until sometime during the second half of 1967, the first crewed test flight of the LM would require a pair of Saturn IB launches as part of a mission designated AS-207/208. Saturn IB SA-207 would launch the first crewed flight of the upgraded Block II CSM followed by an unmanned launch of the first crew-rated LM on SA-208. The two spacecraft would then rendezvous and dock to begin manned testing of the LM.

But as delays in the delivery of key pieces of Apollo hardware caused NASA’s ambitious schedule to slip more and more, in November 1966 program planners modified their test flight schedule. AS-204 would be launched on an open ended mission to be known as “Apollo 1” on February 21, 1967 (see “The Future That Never Came: The Unflown Mission of Apollo 1”). This flight would use Saturn IB designated SA-204 to launch the Bock I CSM-012 (Command-Service Module number 012) with its crew of three into Earth orbit. At this time, it was decided to eliminate the second crewed Block I CSM flight since it was now considered to be redundant. Next up in April would be the first unmanned test flight of the LM for the AS-206 mission. In August, the dual-launch AS-207/208 mission (now redesignated AS-205/208) would take place with the crew being launched in the first Block II CSM.

A Change of Plans

In the wake of the Apollo 1 accident on January 27, 1967 where astronauts Gus Grissom, Ed White and Roger Chaffee died in a cockpit fire during what should have been a routine countdown rehearsal, Apollo program managers were forced to reevaluate their plans as the cause of the Apollo 1 accident was investigated and corrective actions taken. They eventually devised a series of seven mission types which would test Apollo hardware in a step-by-step fashion culminating in a manned lunar landing before the end of the decade.

The “A” series would consist of up to three unmanned test flights of the new Saturn V launch vehicle which would send Apollo to the Moon. The “B” missions would perform unmanned test flights of the LM launched into low Earth orbit on the smaller Saturn IB launch vehicle. The “C” mission would be the first manned test of the Block II CSM in low Earth orbit which would also be launched by a Saturn IB. Next would follow the “D” mission where the CSM and LM would be tested in low Earth orbit with a crew aboard. Either the individual spacecraft for this mission would be launched on separate Saturn IB rockets or, if it were available, by a single Saturn V. This would be followed by the “E” mission which would be a repeat of the D test flight except that a Saturn V would be used to launch the CSM and LM into a high Earth orbit with an apogee of about 6,400 kilometers to build further confidence with this vital hardware. The “F” mission would test the CSM and LM in an even higher Earth orbit or possibly in orbit around the Moon itself in a final rehearsal for the “G” mission which would actually land on the Moon.

The first A mission, Apollo 4, used the Saturn V designated SA-501 to launch the unmanned Block I CSM-017 and a simulated LM payload, LTA-10R (Lunar Test Article number 10R). This Block I CSM tested key systems and post-Apollo 1 modifications for the eventual manned missions. Launched on November 9, 1967, Apollo 4 successfully met all of its test objectives and ended with the splashdown of the CM in the Pacific Ocean after 8½ hours of flight (see “Apollo 4: First Flight of the Saturn V”).

Next up was the first B Mission called Apollo 5. Saturn IB SA-204R (the recertified SA-204 originally meant to launch Apollo 1) successfully launched the unmanned LM-1 (Lunar Module number 1) into low Earth orbit on January 22, 1968 (see “Apollo 5: The First Flight of the Lunar Module”). Although problems were encountered during the nearly eight-hour long flight forcing ground controllers to fly an alternate mission plan, all of the mission’s major test objectives were successfully met. With no need to fly a second unmanned test flight with LM-2, the way was clear for a manned test using the first LM certified for astronauts, LM-3.

Apollo 6 was the second A mission launched on April 4, 1968. For this flight, Saturn V SA-502 launched the unmanned Block I CSM-020 and LTA-2R on a repeat of the Apollo 4 mission which would more closely emulate an actual flight to the Moon and subject the CM to an even more stressing reentry test validating the CSM for manned flights. Unfortunately, a number of problems were encountered with the Saturn V during the Apollo 6 flight including the failure of its S-IVB third stage to reignite to push the Apollo spacecraft into a simulated trajectory to the Moon. While many of the important mission objective were met, the problems encountered raised much concern among Apollo program officials (see “Apollo 6: The Saturn V That Almost Failed”). Already being prepared for a third unmanned Saturn V test flight as early as mid-July 1968 was SA-503. But after the nature of the issues encountered during the Apollo 6 mission were assessed and fixes confidently identified, NASA officials decided on April 27, 1968 that a third unmanned test flight of the Saturn V would not be necessary freeing SA-503 for the D mission to test the LM in Earth orbit which hopefully would get off the ground in January 1969.

The C mission to test the new Block II CSM with a crew on board in Earth orbit was launched on October 11, 1968. Called Apollo 7, the SA-205 Saturn IB launched CSM-101 into orbit with astronauts Wally Schirra, Donn Eisele and Walter Cunningham on board (see “Apollo 7: Rise of the Phoenix”). The CSM was put through its paces and performed nearly flawlessly opening the way for the next crewed Apollo mission.

The Mission Plan

The crew for the Apollo D mission was USAF Colonel James A. McDivitt as the Commander, USAF Colonel David R. Scott as the Command Module Pilot (CMP) and Russell L. Schweickart as the Lunar Module Pilot (LMP). The 39-year old McDivitt had a distinguished military career that included 145 combat missions during the Korean War and service as an experimental test pilot before he was selected as part of NASA’s second group of astronauts in September 1962. Jim McDivitt had previously flown as the command pilot on the four-day Gemini 4 mission in June 1965 (see “The Forgotten Mission of Gemini 4”). Dave Scott, 36 years old, was a West Point graduate and received a masters in aeronautical engineering from the Massachusetts Institute of Technology (MIT) in addition to graduating from the USAF Test Pilot School and Aerospace Research Pilot School. Scott joined NASA with the third group of astronauts selected in October 1963 and had flown previously as the pilot on the Gemini 8 mission in March of 1966 (see “Gemini 8: The First Docking in Space”). Rusty Schweickart, who was 33 years old, served as a USAF (and later, an Air National Guard) pilot before leaving the service in 1963 to finish degrees in Aeronautics and Astronautics from MIT. He had been working as a scientist at MIT’s Experimental Astronomy Laboratory when he was selected as part of NASA’s third group of astronauts along with Scott. This would be Schweickart’s first spaceflight.

The all-Navy backup crew for the mission was Commander Charles “Pete” Conrad, Commander Richard Gordon and Lt. Commander Alan Bean. Originally, McDivitt, Scott and Schweickart were selected in March 1966 as the backup crew for the Apollo 1 mission. But when the second Block I CSM flight was cancelled in November 1966, the three men were reassigned to fly the AS-205/207 mission for the first manned test flight of the LM in Earth orbit. When NASA reworked their test flight plans for the Apollo program after the Apollo 1 accident, the three men were assigned to fly the D mission. And with AS-503 now cleared for manned flight, the plan was for the Saturn V to launch CSM-103 and LM-3 into Earth orbit for testing.

Continued delays with preparing LM-3 for its mission made it clear that it would not be available in time to meet the scheduled January 1969 launch date. In order to keep Apollo’s aggressive test schedule on track for a 1969 Moon landing attempt, it was announced on August 19, 1968 that SA-503 and CSM-103 would be used for a newly-devised “C-prime” mission to send the CSM into lunar orbit with no LM in December 1968. This mission would allow procedures and hardware to be tested in lunar orbit. McDivitt and his crew were offered the mission but declined because of the years they had already spent training for the LM test flight. Ultimately, the E mission crew of Frank Borman, Jim Lovell and Bill Anders got the assignment for what became the Apollo 8 mission (see “Apollo 8: Going Where No One Has Gone Before”). McDivitt, Scott and Schweickart would fly the D mission in February of 1969 with SA-504 as the launch vehicle of CSM-104 and LM-3 for the mission now designated “Apollo 9”.

The primary objectives of the Apollo 9 mission were to continue the demonstration of the performance of the crew, space vehicle and mission support facilities for a crewed Saturn V mission. With the first manned flight of the LM, the objectives centered on demonstrating crew performance as well as various rendezvous procedures for the first time. Launch of Apollo 9 would take place from Pad A of Launch Complex 39 – the fourth Saturn V launched from LC-39A. The first two stages of Saturn V SA-504 plus an initial 152-second burn of the S-IVB third stage would place Apollo 9 into an Earth parking orbit at an altitude of 191 kilometers with an inclination of 32.5°. The primary payload for the mission included CSM-104 with a total mass of 22,028 kilograms – almost seven metric tons less massive than would be typical for a lunar mission owing to the light load of propellants carried by the SM for an Earth orbital mission. The other payload and focus for many of the mission’s tests was LM-3 with a launch mass of 14,525 kilograms. The total in-orbit docked mass of CSM-104 and LM-3 was 36,553 kilograms making the combination the most massive crewed spacecraft ever orbited up until that time.

In-Orbit Testing

Apollo 9 would complete almost two revolutions in low Earth orbit attached to the S-IVB during which time all the spacecraft systems would be checked as would be done during an actual lunar mission. Apollo 9 would deviate from the standard lunar mission profile at the moment the S-IVB would normally reignite to send Apollo towards the Moon. Instead the CSM, call sign “Gumdrop”, would separate from the S-IVB stage turn around and then move back towards the stage to dock with the LM, call sign “Spider”. The CSM would then extract the LM and move off to begin its test program in earnest. Meanwhile, the S-IVB stage would reignite its J-2 engine about four hours and 45 minutes after launch for a 62-second burn to place the stage into an orbit with a 2,022-kilometer apogee as part of an engineering evaluation of the stage’s capabilities. A third burn of 241 seconds duration starting about six hours and seven minutes after launch would place the S-IVB stage into an escape trajectory and ultimately solar orbit. The S-IVB would then dump its remaining propellant load through the J-2 engine and open the propellant tank vents to safe the stage.

During the balance of the first day in orbit and into the second day, the Apollo 9 crew would checkout the performance of the CSM and perform a total of four burns of the SM’s Service Propulsion System (SPS) to check the performance of the pair of docked spacecraft and raise its orbit for the tests to come. During the third day, McDivitt and Schweickart would enter the LM for the first time to begin the checkout of Spider. This would be the first internal crew transfer between spacecraft instead of an EVA transfer which took place in January 1969 during the Soviet Soyuz 4/5 mission (see “Soyuz 4 & 5: The First Crew Exchange in Space”). After almost ten hours of systems checks, the LM descent propulsion system (DPS) would be fired for over six minutes with Spider still docked with Gumdrop. This would test the DPS, the LM autopilot and manual throttling of the engine.

On the fourth day, activities would center on performing an EVA – the first for an American mission since Gemini 12 in November of 1966 (see “The Grand Finale: The Mission of Gemini 12”). Both the CM and LM cabins would be depressurized with Schweickart exiting from the LM while Scott observed from the open CM hatch. The EVA performance of the new A7L spacesuits would be assessed for the first time in flight and Schweickart would test the Portable Life Support System (PLSS) which would be worn during EVAs on the lunar surface. Scott would rely on his umbilical for life support and communications while he was standing in the CM hatch. Attached to the spacecraft by a 7.6-meter nylon tether, Schweickart would move from the LM porch to the CM hatch using handrails to demonstrate the LM crew rescue procedures in case an internal transfer proved to be impossible. During much of the planned 2¼ hour EVA, Schweickart would use a pair of foot restraints on the LM descent stage porch nicknamed “golden slippers” to keep him in place and his hands free to perform his various tasks.

Activities for the fifth day of the mission would concentrate on testing the LM in free flight with a crew on board for the first time. After McDivitt and Schweickart checked out Spider as would be done prior to the descent to the lunar surface, the two spacecraft would undock to begin 6½ hours of independent flight. The DPS would be fired twice for about 20 seconds each to move the LM up to 176 kilometers from the CSM. In case of a problem with the LM, this mission profile would allow the CSM to easily reach the LM for a rescue. After the LM descent stage was jettisoned, the ascent stage’s APS would be fired briefly twice to bring the LM back into the vicinity of the CSM for the rendezvous test. Following docking and the transfer of the crew back to the CSM, the now unoccupied ascent stage would be jettisoned and the APS would be fired remotely for about six minutes until propellant depletion. The expected 1,725 meter per second delta-v would place the unmanned LM ascent stage into an extended 243 by 5,930 kilometer orbit.

With most of the major objectives met by the end of the fifth day, the balance of the ten-day mission would be spent performing system checks, engineering tests, additional SPS burns and experiments. The SPS would make its eighth planned burn of the mission to bring Gumdrop home with splashdown occurring in the West Atlantic recovery zone with the Iwo Jima-class amphibious assault vessel, the USS Guadalcanal, serving as the primary recovery ship. The total mission length was expected to be 238 hours, 46 minutes and 30 seconds – just minutes shy of ten full days.

Preparing Apollo 9 for Launch

The first major piece of D mission hardware to arrive at Cape Kennedy (which reverted to its original name of Cape Canaveral in 1973) was the S-II-4 second stage of Saturn V SA-504 on May 15, 1968, although at this time it had been assigned to support the E mission. The S-II-4 stage was the first in the series to incorporate a number of design modifications to improve the overall performance of the Saturn V. First of all, the vacuum thrust of the stage’s five J-2 engines was increased by 2.2% providing a total thrust of 5,515 kilonewtons. The use of a new lightweight tank design with thinner walls resulted in 1.5 metric ton decrease in the stage’s dry mass down to 38.4 metric tons. The propellant load of cryogenic liquid hydrogen and liquid oxygen (LOX) was increased by 17.0 metric tons resulting in a gross liftoff mass of 484.9 metric tons.

After numerous delays, the descent stage of LM-3 was delivered to the Cape on June 9, 1968 followed five days later by the ascent stage. Not long after post-delivery testing of LM-3 began on June 11, it was clear that a lot of work remained to be done before the new spacecraft could be launched. As the delays mounted over the coming weeks, it became evident that LM-3 would not be ready to fly by January 1969 leading to the August 19 decision to postpone the D mission (now to be designated “Apollo 9”) and fly the new C-prime mission of Apollo 8 first instead. As a result, the SA-504 launch vehicle and CSM-104 spacecraft were reassigned to support the Apollo 9 mission.

The next major piece of Apollo 9 mission hardware to arrive on September 12, 1968 was the S-IVB-504N third stage of the Saturn V. After the S-IVB-503 stage for SA-503 was completely destroyed during a ground testing accident on January 20, 1967, the original S-IVB-504 stage was reassigned for use on SA-503 and given the new designation of S-IVB-503N. Likewise, the original S-IVB-505 stage was redesignated S-IVB-504N on January 25 when it was reassigned for use on SA-504. Like the S-II-4 stage, S-IVB-504N sported a number of modifications including the newer J-2 engine which increased the thrust of the stage to 1,023 kilonewtons and a decrease in the dry mass of about half a ton to 11.5 metric tons.

Next to arrive was the improved S-IC-4 first stage of the Saturn V on September 30, 1968. S-IC-4 now had a dry mass 3.8 metric tons less than the earlier S-IC stages and supported a 106.4 metric ton increase of the propellant load of RP-1 and LOX. The liftoff mass of the fully loaded S-IC-4 stage was now 2,279.9 metric tons. Cameras used to monitor propellant behavior and stage separation were deleted and the number of measurements made during flight decreased from 2,798 to 2,159 as the Saturn V transitioned from R&D to an operational status. These and other changes led to a further decrease in the dry mass of the Saturn V and an increase in performance. With the delivery of the S-IC-4 stage, stacking of the launch vehicle on Mobile Launch Platform-2 (MLP-2) could begin.

After completing its integrated systems checks at the North American Rockwell facility in Downey, California at the end of August 1968, CSM-104 was shipped to Cape Kennedy and arrived on October 5. A series of combined systems checks followed including tests with the prime and backup crews with CSM-104 in a high altitude chamber until November 18. With the completion of combined systems checks on LM-3 on December 3, final integration of the Apollo 9 spacecraft modules started with the final stacking of the launch vehicle and overall testing completed on December 27. On January 3, 1969, Apollo 9 was rolled out to LC-39A for the final round of prelaunch checkouts. After the completion of the countdown demonstration tests on February 12, all was set for launch scheduled during a 3½ hour window starting at 11:00 AM EST on February 28.

Countdown & Launch

The terminal countdown for the Apollo 9 mission started at 10:00 PM EST on February 26 with the clock at the T-28 hour mark. In the meantime, the Apollo 9 crew was diagnosed with a mild viral respiratory illness, so the decision was made a half an hour into a scheduled three-hour hold at the T-16 hour mark to recycle the countdown to T-42 hours to allow the crew time to recover. With the crew’s health improved, the countdown was resumed at 2:30 AM EST on March 1.

The countdown for Apollo 9 proceeded without major incident. With the crew passing their physicals on March 2 to ensure they had recovered from their illness, the almost routine events of waking the crew early on launch day, having breakfast, suiting up and transferring to LC-39A went off without a hitch with the crew entering CSM-104 before the T-2 hour mark of the countdown. The countdown continued uninterrupted until liftoff of Apollo 9 at 11:00:00 AM EST (16:00:00 GMT) on March 3. With a liftoff mass of 2,942 metric tons, this was the heaviest Saturn V (or indeed, any rocket) launched to date.

The ascending Saturn V under the power of its five F-1 engines hit Mach 1 68.2 seconds after launch and encountered maximum dynamic pressure 17.3 seconds later. The rocket continued to ascend smoothly with center engine cutoff commanded at 134.3 seconds after launch in order to limit the acceleration load to less than 4 gs. This event was followed by the shutdown of the remaining four outboard engines 28.4 seconds later at an altitude of 64.5 kilometers. After a nearly perfect performance, S-IC-4 was jettisoned 0.7 seconds after engine shutdown where the S-II-4 stage ignited and continued the ascent. The spent S-IC-4 stage impacted in the Atlantic Ocean 536 seconds after launch about 642 kilometers downrange.

As S-II-4 was burning, Apollo’s launch escape tower was jettisoned 198.3 seconds after launch since it was no longer needed to support abort options during the rest of the ascent. The S-II stage completed its task and shut down its five J-2 engines eight minutes and 56.2 seconds after launch at an altitude of 186.6 kilometers some 1,538 kilometers downrange. The only issue noted during the ascent on the S-II stage was a mild longitudinal vibration (called “pogo”) during part of the burn. Modifications would be made to subsequent S-II stages to avoid the issue in the future. The S-IVB-504N stage then ignited its single uprated J-2 engine after separation to continue pushing its payload to orbital velocity with its first burn of the mission. The spent S-II-4 stage then tumbled to Earth impacting about 20 minutes and 25 seconds after launch about 4,469 kilometers downrange in the Atlantic.

The S-IVB-504N stage finally shut down its single J-2 engine 11 minutes, 4.7 seconds after launch 16.0 seconds later than planned. Apollo 9 was now in a 184.6 by 186.6 kilometer parking orbit with an inclination of 32.6°. And with an estimated in-orbit mass of 132.5 metric tons, Apollo 9 was the heaviest object ever placed into Earth orbit up until this time beating the previous record holder, Apollo 8 with its attached S-IVB stage, by five metric tons.

The Beginning of Orbital Operations

With the attitude during this phase of the mission controlled by the S-IVB’s pair of APS (Auxiliary Propulsion System) pods at its base, Apollo 9 assumed a nose-forward attitude for the start of the in-orbit checkout of the spacecraft systems. One of the first tasks accomplished by the crew was to extend the CM’s docking probe. This probe was designed to be inserted into the conical drogue in the LM top hatch and latch into place for a soft docking. Pressurized nitrogen would then be used to retract the probe by 25 centimeters so that the docking rings and the seals of the two spacecraft would come into contact allowing a set of three pairs of latches to engage for a hard docking of the two spacecraft.

Towards the end of the second revolution of the mission, the CSM Gumdrop separated from the S-IVB stage at 18:41:16 GMT and moved safely away as the four panels of the SLA (Spacecraft Launch Adapter), which protected the LM during ascent, were jettisoned. Dave Scott then turned Gumdrop around and moved back towards the LM, Spider, still tucked inside the S-IVB stage. Hard docking was successfully accomplished at 19:01:59 GMT. Jim McDivitt and Rusty Schweickart then pressurized the docking tunnel between the two craft and removed the 76-centimeter CM docking hatch after the pressure had been equalized and the seal between the two craft had been verified. The docking latches were then inspected to ensure that they had properly secured the two spacecraft and an umbilical was connected so that the LM could draw power from the CSM. Afterwards, the CM docking hatch was replaced for the next phase of the mission.

With Spider now securely docked to Gumdrop, the LM was pulled from S-IVB-504N at 20:08:09 GMT. After the RCS (Reaction Control System) engines on the SM fired briefly to move off, S-IVB-504N used its APS to change its attitude in preparation for its second burn of the mission. At 20:45:55 GMT, the J-2 engine of S-IVB-504N reignited for a 62.1-second burn which placed it into an intermediate orbit of 195.8 by 3,095.8 kilometers. The subsequent 80-minute coast allowed the J-2 engine to warm up as part of the testing for its third burn – the only time during the Apollo program where the S-IVB would make three burns as part of this mission’s “out-of-specification” engineering evaluation of the stage.

The S-IVB-504N stage ignited for its final burn at 22:07:19 GMT. For the first 100 seconds of the 242.1-second burn, the J-2 engine thrust was 2.6% lower than planned owing to the out of nominal conditions of the test. Following engine shutdown, the APS ullage engines were fired until propellant depletion resulting in an additional delta-v of 9.7 meters per second. The underperformance of the J-2 engine left S-IVB-504N travelling 1,520 meters per second slower than planned but the third burn was still enough for the stage to escape the Earth with a hyperbolic excess velocity of 908 meters per second (compared to the planned 5,594 meters per second). S-IVB-504N ended up in a 0.859 by 0.994 AU solar orbit with a period of 325.8 days where it remains to this day. Because of the loss of the engine’s pneumatic system pressure regulator which controlled the propellant valves during this final burn, the planned propellant dump could not take place. However, the propellant tanks’ vents were opened allowing the stage to be safed. Last contact with S-IVB-504N was at 05:21:06 GMT on March 4 some 13 hour and 20 minutes after launch.

Meanwhile, the Apollo 9 crew began their activities with the docked CSM/LM. At 21:59:01 GMT, the SM fired is SPS (Service Propulsion System) for 5.2 seconds. The resulting delta-v of 11 meters per second from this first SPS maneuver raised the docked spacecraft’s orbit to 206.1 by 236.3 kilometers as well as checked out the spacecraft’s ability to handle an SPS burn. After completing other tasks and having a good meal, the crew went down for their first rest period of the mission just over nine hours after launch. Given the nature of the mission activities to follow which required all three crew members, the three astronauts were allowed to sleep at the same time to keep them on the same schedule. This was a departure from the earlier pair of manned Apollo missions where the crews slept on a staggered schedule so that there was always an astronaut “on watch” to monitor spacecraft systems.

Checking Out Spider

At about 10:40 GMT on March 4, Houston woke up the Apollo 9 crew to begin their first full day in orbit. At 14:12:04 GMT, the SPS was fired for the first of three burns of the day. The 110-second burn with a delta-v of 259 meters per second raised the orbit to 205.0 by 356.5 kilometers to further test the docked spacecraft during maneuvers as well as prepare for orbital operations to follow. Three hours, five minutes and 39 seconds later, a second burn of 280 seconds changed the velocity of the docked spacecraft by 783 meters per second. This not only lightened the CSM and moved its center of gravity forward for the tests to come, but also raised the orbit to 208.5 by 509.1 kilometers as well as shifted the orbital ground track 10° to the east to provide better lighting conditions for the rendezvous exercise later in the mission. A final burn for the day was started at 20:24:41 GMT. This 27.9-second out of plane burn with a delta-v of 92 meters per second shifted the ground track another 1° eastward.

Activities during the third day in orbit centered on checking out the LM. While all three astronauts donned their A7L spacesuits starting at 09:00 GMT on March 5, Schweickart began to suffer from the effects of space sickness and vomited his breakfast. McDivitt was also slightly nauseous but was not as badly affected as his crew mate. After Scott opened the docking tunnel hatch and removed the drogue, the way was clear for Schweickart to enter Spider at 11:15 GMT for the first time. After transferring the LM to internal power and beginning to activate its systems, Schweickart was joined about an hour later by McDivitt to begin a day’s worth of systems checks on the LM after the hatches between the two craft were sealed. Among the activities was the successful deployment of the LM’s landing at 13:00 GMT.

At 13:39 GMT McDivitt had a private conversation with the CAPCOM to discuss Schweickart’s condition after he vomited for a second time while in the LM. Fortunately, Schweickart’s condition improved noticeably afterwards but McDivitt was concerned enough to propose significantly shortening the EVA activities for the following day. In the meantime, the first live television broadcast of the mission started 14:28 GMT for a quick five-minute transmission from the LM.

As part of the testing, Scott put Gumdrop into a free drift mode to allow Spider’s RCS engines to be tested by changing the docked craft’s attitude. The final major test of the day involved a burn of the descent stage’s propulsion system (DPS) with the spacecraft still docked starting at 17:41:34 GMT. For the first five seconds of the 371.5-second burn of the DPS, the LM’s autopilot started at a throttle setting of 10% then raised it to 40% for the next 21 seconds before going to 100%. For the last minute of the burn, the DPS was throttled manually cycling several times between 10% and 40%. The out-of-plane maneuver had a total delta-v of 530 meters per second and shifted the orbital plane eastward by another 6.7° with only a small change in orbit altitude which was now 207.6 by 509.3 kilometers.

After successfully completing the day’s tasks, McDivitt and Schweickart powered down the LM and returned to the CSM at about 19:00 GMT. The final activity for the day was the fifth SPS burn of the mission starting at 22:26:12 GMT. The 43.3-seond burn with a delta-v of 174 meters per second circularized the orbit to 233.2 by 242.6 kilometers for the upcoming LM test flight. Afterwards, the astronauts removed their spacesuits and settled down for a good meal and some rest after a long day of work.

The EVA

The major activity for March 6 was the EVA to test the A7L spacesuit and the PLSS backpack which would be used by astronauts on the lunar surface. Because of Schweickart’s severe nausea the previous day, McDivitt had consulted with Mission Control to limit the day’s activities to simply depressurizing the LM cabin to test the suit. However, Schweickart’s condition had noticeably improved so it was decided to have him exit the LM after all to perform an abbreviated EVA with Scott performing his tasks from the CM side hatch. All three crew members finished donning their spacesuits at 12:15 GMT and an hour and a half later entered the LM to begin activating its systems. At 15:53 GMT Jim McDivitt radioed from the LM that Rusty Schweickart’s condition was excellent clearing the way for the EVA.

With everyone prepared and the hatches between the spacecraft closed, the LM was depressurized first and its forward hatch opened at 16:46 GMT. About 13 minutes later, Scott had finished depressurizing the CM cabin. At this point, Rusty Schweickart began to exit Spider feet first and face up slowly with Jim McDivitt monitoring his progress from the LM. Three minutes later, Dave Scott opened Gumdrop’s side hatch to observe his crew mate’s exit into space. By 17:07 GMT, Schweickart had fully exited the LM and placed his feet into the “golden slippers” foot restraints. For the first time, a US astronaut was conducting an EVA drawing his life support from a self-contained backpack instead of from his spacecraft via an umbilical. With Schweickart in essence being a sort of independent spacecraft at this point, the crew had given him the informal callsign of “Red Rover”. Once in place, Schweickart made a photographic survey of the spacecraft exterior using a 16 mm movie camera as well as a handheld Hasselblad 70 mm camera as McDivitt photographed his LMP’s progress from inside the LM.

Meanwhile, Dave Scott partially exited the CM side hatch with his legs and lower torso still inside the cabin. Scott was observed attempting to retrieve thermal samples from the CM exterior (which were missing) and at 17:26 GMT turned to remove samples on the SM. Afterwards, Schweickart passed his cameras to McDivitt as well as thermal samples he retrieved from the LM’s exterior, He then began an evaluation of the LM’s exterior handrails at 17:42 GMT while his crew mates observed. The planned simulated transfer between the LM and CM hatch was not performed to limit Schweickart’s EVA time in light of his nausea issues the previous day. Schweickart then returned inside of the LM and closed the hatch at 17:48 GMT. A minute and a half later, Scott reported that the CM side hatch had been closed and locked. The two spacecraft were then repressurized ending the EVA activities. Schweickart and Scott had spent 67 and 61 minutes, respectively, in a vacuum with Schweickart spending a total of 37 minutes outside the LM.

With the LM fully repressurized, McDivitt and Schweickart performed a 15-minute live television broadcast from inside the LM starting at 18:58 GMT. The picture quality was much improved compared to the previous telecast allowing the astronauts to discuss their accomplishments. After the telecast was ended as Apollo 9 moved out of range, McDivitt returned to the CSM followed by Schweickart at 20:55 GMT after he had deactivated the LM’s systems for the day. All three astronauts removed their spacesuits and began light duties before they started their next sleep period. Despite the problems encountered, the Apollo 9 mission was continuing to meet its primary mission objectives.

Testing Spider in Free Flight

The fifth day of the Apollo 9 mission focused on testing the LM in free flight with astronauts at the controls for the first time. All three astronauts donned their spacesuits by 06:00 GMT on March 7. Two hours later, Schweickart entered the LM and by 08:15 GMT started activating its systems. McDivitt joined the LMP forty minutes later to begin the long list of systems checks needed before the upcoming test flight.

With both spacecraft ready, undocking was attempted at 12:38 GMT but the latches holding the two craft together failed to release immediately. At 12:39:36 GMT, Gumdrop and Spider finally undocked. Spider then took up a position to allow Scott to inspect the LM from Gumdrop. About 23 minutes after undocking, Scott fired the CSM’s RCS for 9.5 seconds to begin moving away from Spider in a 226 by 235 kilometer orbit. The maneuver placed Gumdrop 3.7 kilometers ahead of Spider 45 minutes later.

At 13:47:35 GMT, Spider’s DPS was fired for 19.0 seconds for its “phasing maneuver” which placed the LM into an orbit with the same period as Gumdrop but ranging 22.6 kilometers above and below the CSM over the course of an orbit while drifting as far as 181 kilometers from Gumdrop. The next burn of the DPS started at 15:39:08 GMT. This 22.4 second burn placed Spider into a 247.0 by 257.2 kilometer orbit. At 16:16:07 GMT, Spider’s descent stage was jettisoned without any problems and the LM’s RCS was fired for 31.7 seconds for the “coelliptical sequence”. This placed the ascent stage into a 209 by 256 kilometer orbit which allowed it to start closing in on Gumdrop which was 152 kilometers ahead and 19 kilometers above Spider. The now discarded LM descent stage, with the COSPAR designation of 1969-018D, remained in its decaying orbit until 03:45 GMT on March 22 when it reentered Earth’s atmosphere off the east coast of Africa.

At 16:58:15 GMT, Spider’s APS was ignited for the first time. The 2.9-second burn for the “constant differential height” maneuver placed Spider into a lower 206 by 215 kilometer orbit which allowed it to start catching up with Gumdrop. This was followed at 17:57:59 GMT by a 37.6-second burn of the APS for the “terminal phase initiation” which would place Spider on course for its final rendezvous with Gumdrop. Two small course correction burns were performed using the LM’s RCS 10 and 22 minutes later. Terminal phase braking using the LM’s RCS started at 18:30:03 GMT with Spider coming to a stop 48 seconds later to begin another round of formation flying and inspections by Scott in Gumdrop.

As Spider was being maneuvered for redocking, Jim McDivitt had some problems trying to get a good view of the docking target on Gumdrop while looking through the LM’s overhead rendezvous window because of glare from the Sun. This prompted McDivitt to comment “that wasn’t a docking, that was an eye test.” The forward-looking arrangement of the LM’s controls also contributed to the difficulty in getting the two spacecraft properly aligned. Despite this, the two Apollo spacecraft finally redocked at 19:02:26 GMT wrapping up almost six hours and 23 minutes of independent flight. The first manned test of the Apollo LM in Earth orbit was a complete success.

About an hour and a half after docking, McDivitt reentered the CSM while Schweickart configured Spider for its final unmanned tests following undocking. Schweickart returned to the CSM at 21:00 GMT and Spider’s ascent stage was jettisoned at 21:22:45 GMT. Ten minutes later, Gumdrop’s RCS were fired to move away from the uncrewed ascent stage. At 21:53:15 GMT, the APS was ignited for the stage’s final test. Burning for 362.3 seconds until its oxidizer supply had been depleted, the spent LM ascent stage (with the COSPAR designation 1969-018C) had changed its velocity by 1,638 meters per second and was now in a 234.5 by 6,965.2 kilometer orbit. While the orbit of the now-derelict spacecraft was expected to decay in five years, Spider’s ascent stage remained in orbit until it reentered on October 23, 1981 – over 7½ years later than expected.

The Last Days of the Mission

With the majority of the mission objectives met, the crew of Apollo 9 had a much more relaxed schedule for their last six days in orbit. This allowed the crew to continue to perform engineering evaluations, systems checks and experiments at a more leisurely pace. At 19:25:07 GMT on March 8, the SPS was fired for the sixth time – one revolution later than originally planned because the RCS burn needed to settle the SPS propellant in their tanks prior to ignition had been improperly programmed. This brief 1.43-second burn of the SPS with a delta-v of 10 meters per second lowered the CSM’s orbit to 200.9 by 228.0 kilometers ensuring that the CSM’s RCS could be used to bring Apollo 9 home in case of an SPS failure at the end of the mission.

Starting at 20:10 GMT, the crew began taking photographs for the only science experiment of the mission, the S065 Multispectral Photography Experiment. Included in the mission at the last moment, this experiment called for taking photographs of selected land and ocean targets simultaneously in four different spectral bands in the near infrared and visible wavelengths. These images would be used for an early assessment of space-based Earth resource imaging in preparation for NASA’s upcoming Earth Resource Technology Satellite (ERTS, later known as Landsat). These data would also prove to be useful for planning multi-band photography experiments for the Skylab program. The experiment used four modified Hasselblad Model 500-EL cameras secured to a common mount and synchronized for simultaneous exposures. The standard hand held Hasselblad 70 mm cameras on board were also used to photograph targets of opportunity. Other tests during the last days of the mission included landmark sightings for use in spacecraft navigation.

March 9 saw the Apollo 9 crew perform two more S065 photography sessions as well as landmark sighting tests and photography of targets of opportunity. At 17:39:00 GMT on March 10, the SPS was fired for the seventh time in the mission. This 24.9-second burn with a delta-v of 198 meters per second raised the apogee to 468.9 kilometers and lowered the perigee to 186.5 kilometers in order to set the proper conditions for the deorbit burn at the end of the mission. More photography took place during subsequent orbits.

In addition to two more S065 photography sessions on March 10, the Apollo 9 crew made sightings of NASA’s Pegasus 3 satellite in orbit since July 1965 (see “The Last Launch of the Saturn I”). Deactivated by ground command six months earlier, the giant derelict satellite was spotted on two successive revolutions at 16:43 and 18:14 GMT from a range of about 1,800 kilometers. Three final S065 photography sessions were made over the next day as well as sighting of Spider’s ascent stage. The results of the S065 experiment proved to be excellent in part because the astronauts had plenty of time to prepare their equipment and take photographs. They also had the flexibility to wait for the optimum cloud cover and viewing conditions to ensure the best images. Targets in the southern US, Mexico, Brazil and Africa were eventually observed giving scientists the data they needed to verify their expectations for future Earth resource imaging programs.

Coming Home

March 13 was the last day for the Apollo 9 crew in orbit. The beginning of the day was spent stowing gear and preparing for reentry and splashdown. Because of unfavorable weather in the prime recovery zone, the deorbit burn was postponed one revolution to bring Apollo 9 down at an alternate Atlantic recovery zone 1,100 kilometers to the southwest. The SPS was fired for the eighth and final time starting at 16:31:14 GMT during the mission’s 151st revolution. The 11.74-second burn changed the velocity of the CSM by 98 meters per second and lowered the perigee to 7.8 kilometers below sea level ensuring reentry. About 4½ minutes after the completion of the deorbit burn, the CM and SM separated. After reorienting itself so that its heat shield faced the direction of travel, Gumdrop reached its entry interface at an altitude of 122 kilometers at 16:44:10 GMT travelling at 7,893 meters per second.

After reentry, the CM’s parachutes were deployed on schedule with Apollo 9 splashing down at 17:00:54 GMT (12:00:54 PM EST) at 23.22° N, 67.98° W in the eastern Atlantic north of the island of Hispaniola. After a mission lasting 241 hours and 54 seconds, Apollo 9 had come down only five kilometers from its target point and 5.6 kilometers from its primary recovery ship, the USS Guadalcanal, after travelling about 6.79 million kilometers in Earth orbit. The Apollo 9 crew was retrieved by helicopter and they were onboard the recovery ship 49 minutes after splashdown with the five metric ton CM following 83 minutes later.

Following recovery, the crew and spacecraft were returned to the mainland for debriefings and examinations. Although some minor issues had been encountered, Apollo 9 was a resounding success with virtually all of the primary and secondary mission objectives achieved. The mission’s success eventually prompted Apollo program managers to skip the planned E mission (which would have been a repeat of Apollo 9 but in a higher Earth orbit) since it was now considered to be too conservative. Instead, Apollo 10 would fly the F mission to test the LM in lunar orbit as a final rehearsal of the first lunar landing attempt in the summer of 1969.

After the Apollo 9 mission, Jim McDivitt became Manager of Lunar Landing Operations in May 1969 and, in August, the Manager of the Apollo Spacecraft Program. McDivitt retired from NASA and the USAF as a Brigadier General in June 1972 and moved on to a series of jobs in industry. Dave Scott was named backup commander of the Apollo 12 mission in April 1969 and eventually commanded the Apollo 15 lunar landing mission in July 1971. After retiring from the USAF in March 1975, Scott was appointed the director of NASA’s Dryden Flight Research Center in April 1975 after a two year stint as its deputy director. He left NASA on September 30, 1977 for a career in the private sector. Rusty Schweickart continued in the astronaut corps serving a supporting role in the Skylab 4 mission but there was reluctance (both on his part and that of NASA management) to fly him on another mission until space sickness was better understood. Schweickart left NASA in 1977 to serve in various roles in California state government before moving on to the private sector.

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Related Video

Here is an excellent NASA documentary about the Apollo 9 mission entitled Apollo 9: Three to Make Ready:

Here is a collection of raw 16 mm silent film footage taken by the crew during the Apollo 9 mission:

Related Reading

“Apollo 8: Going Where No One Has Gone Before”, Drew Ex Machina, January 5, 2019 [Post]

“Apollo 5: The First Flight of the Lunar Module”, Drew Ex Machina, January 22, 2018 [Post]

General References

David Baker, The History of Manned Space Flight, Crown Publishers, 1981

Alan Lawrie & Robert Godwin, Saturn V The Complete Manufacturing and Testing Records, Apogee Books, 2005

Richard W. Orloff and David M. Harland, Apollo: The Definitive Sourcebook, Springer-Praxis, 2006

Apollo 9 Press Kit, NASA Press Release 69-29, February 23, 1969

Saturn V Launch Vehicle Flight Evaluation Report – AS-504 Apollo 9 Mission, MPR-SAT-FE-69-4, NASA Marshall Space Flight Center, May 5, 1969

Post Launch Mission Operation Report – Apollo 9 (AS-504) Mission, Office of Manned Space Flight, May 6, 1969

Final Flight Evaluation Report – Apollo 9 Mission, Office of Manned Space Flight, June 1969