America's first astronaut-ready spacecraft in eight years is currently being put through its paces in an unmanned test flight to the ISS, but 50 years ago, another spacecraft was undergoing an even bigger test. In the first week of March 1969, NASA's Apollo 9 mission saw the Lunar Excursion Module (LEM) getting its first full orbital workout as the US sprinted the last lap of the race to be the first on the Moon.

In the first months of 1969 NASA was on a real high, basking in the success of the first manned flight to orbit the Moon. But the triumph of the Apollo 8 mission in December 1968 was just a step, albeit a very significant one, in the US program to place an American astronaut on the Moon by the end of the decade.

The crew of Apollo 8 flew to the Moon in Command Service Module (CSM) – a two-part modular spacecraft consisting of a Service Module that carried the spacecraft's main engine and was designed to only operate in space, and the Command Module, which was the home for the astronauts and was designed to return them safely to Earth.

However, if astronauts were to land on the Moon itself, another spacecraft was required –the Lunar Excursion Module (LEM). NASA engineers had to grapple with the fact that the LEM was a highly specialized craft that could only operate in the vacuum of space, and the only way to properly test it and certify it for the lunar landings was to put one into space.

Apollo 9's objectives

The result was Apollo 9. The most complex space mission ever undertaken at the time, Apollo 9 was a 10-day low-Earth orbit flight. It was the 19th American manned spaceflight, the third manned Apollo mission, and the second to be launched atop the gigantic Saturn V rocket. But most important, this was the first mission where all three of the main components for a Moon lander – the Saturn V, the CSM, and the LEM – flew at the same time, and the first time that NASA could fully rehearse the launch of a lunar mission.

It was not, however, the first time an LEM had gone into space. That happened on January 22, 1968 when an unmanned LM 1 was sent into orbit by a Saturn IB booster. But to properly test the spacecraft, a crew was needed. What NASA wanted from Apollo 9 was to demonstrate how the crew, the spacecraft, and mission control could work together; fly the LEM in orbit; rehearse docking and undocking maneuvers; and test the full spacesuit that would be worn by the first moonwalkers.

In addition to this, the crew would address a number of concerns that the engineers had raised. Would the drogue needed to dock the two spacecraft engage without damaging the mechanism? Would the trunk where the two craft met be too weak to hold up to thruster fire? And would the electronics of the two spacecraft interfere with one another?

It also had another first that was truly worrying. Every other manned space mission had been in capsules equipped with heat shields, streamlining, and parachutes. If the LEM ran into trouble while its two crew members were aboard and couldn't return to the CSM, they would have no way of returning to Earth and would face the choice of dying in orbit or burning up in the atmosphere. That put a lot of pressure on the little machine to perform.

The crew of Apollo 9 was led by Colonel James Alton McDivitt (USAF), who was Mission Commander. He was 39 years old, and command pilot of Gemini 4. The Command Module Pilot was Colonel David Randolph Scott (USAF), 36 years old and former pilot of Gemini 8. And the Lunar Module Pilot was Russell Louis "Rusty" Schweickart, a 33 year old civilian on his first spaceflight.

Lift off

Apollo 9 lifted off on March 3, 1969 from Pad A of Launch Complex 39 at the Kennedy Space Center after a three-day delay due to the crew suffering a minor viral respiratory infection. Though there were some vibration problems similar to those seen in previous Saturn V launches, the S-IVB third stage and its payload went into an 89-minute orbit about 119 miles in altitude without major incident.

Mission control was keen to get all of the primary mission objectives out of the way as fast as possible, so no time was wasted. As soon as the post-insertion checkouts were completed, the CSM separated from the booster and the four protective panels around the LEM were jettisoned.

McDivitt then turned the Command Module around and used the reaction thrusters and zeroed in on the docking target atop the Lunar Module. When the docking system was set and secured, he activated the springs to free the LEM and fired the explosive bolts that kept in place.

Once free of the S-IVB, McDivitt rotated the now double spacecraft and the fired the main engine, known formally as the Service Propulsion System (SPS), to move well away from the booster and into a higher orbit. Mission control then restarted the S-IVB's engine and let it burn dry as it powered into an orbit around the Sun.

Check outs and power ups

On the second day of the mission, the crew was busy running system checks and practicing maneuvering the docked spacecraft through a series of pitches, rolls, and yaws, as well as three more SPS burns to simulate the course corrections that a lunar mission would require. Then, on the third day, the crew opened up the LEM and went inside to power it up, run system and communications checks, then deploy the four landing legs that were folded up during the launch. They then rounded up the day with a five-minute television broadcast to the public back on Earth and fired the LEM descent engine for 372 seconds.

Spacewalk

On the fourth day, the Apollo 9 crew went for a walk – a spacewalk. The objectives were two fold. First, to test the Primary Life Support System (PLSS) backpack for the Apollo spacesuit, which was flying in space for the first time. This was the key component that the spacesuit that would be worn while walking in the Moon and contained the oxygen tanks, air purifiers, cooling system, communications system, and power supply that turned the suit into a completely autonomous spacecraft in its own right.

The second goal was to rehearse the emergency egress procedure that would be needed if the docking mechanism failed. For this Schweickart, wearing the PLSS, would leave the Lunar Module through its front hatch, then move and over hand to the Command Module. However, this was abandoned because Schweickart was suffering from recurrent bouts of space sickness and they didn't want to risk his being incapacitated by nausea while outside the spacecraft.

Instead, Schweickart and McDivitt went into the Lunar Module while Scott remained in the Command Module. Schweickart wore the PLSS while McDivitt and Scott remained connected to the internal life support systems by umbilicals. The two spacecraft were depressurized and Schweickart went out the front hatch of the LEM. He didn't leave the craft, but was attached to a 25-ft (7.6-m) nylon line and his feet set in the "golden slippers" foot restraints bolted to the "porch" outside the hatch.

Meanwhile, Scott opened the hatch on the Command Module so he could film Schweickart and send back television coverage to Earth, while Schweickart photographed him. They were originally going to spend two hours outside, but it was decided to halve this out of consideration for Schweickart's health. Despite their restricted positions, Scott and Schweickart managed to collect thermal experiment samples that had been riding outside and Schweickart was able to practice moving a bit, finding the handrails easier than had been the case in the Earthbound simulators.

The flight of the LEM

Day five was when things got dramatic. Wearing suits without gloves or helmets to make working easier, McDivitt and Schweigert moved into the LEM while Scott remained in the Command Module. Once everything was buttoned up, Scott separated from the LEM and moved off to a safe distance.

It was at this point that NASA revived an old tradition. Up until the Gemini 3 mission, American spacecraft were named by the astronauts. It was a practice that the space agency was never comfortable with, fearing that a poorly chosen moniker would look embarrassing in the headlines of the world's newspapers. So, for four years spacecraft were only called by their mission designations.

Now, as the CSM and the LEM flew away from one another, the tradition had to be revived because radio call signs were needed. Apollo 9 ceased to exist and became "Gumdrop" for the Command Module and "Spider" for the Lunar Module.

With McDivitt at the controls, Spider did a 90-degree pitch and a 360-degree yaw maneuver to help Scott to confirm that the legs had deployed properly. The inspection completed, McDivitt fired the descent engine, sending the LEM 23 km (14 mi) from the CSM. He then opened up the throttle to 40 percent before bringing it back to 10 percent as the distance increased to 90 km (47 mi) and then to 160 km (100 mi), where it could only be seen from the CSM using the capsule's sextant. Because the LEM was now in a higher orbit, it soon trailed 185 km (115 mi) from the CSM.

In order to return astronauts to lunar orbit from the surface, the LEM was made in two stages. The descent stage had the larger main engine for slowing down the module so it could land, and on top of this was the ascent stage, consisting of the crew compartment and the ascent engine. At the end of a Moon visit, the descent stage acted like launch pad from which the ascent stage separated and lifted off.

Since the ascent engine was literally vital to future astronauts, McDivitt and Schweigert fired the explosive bolts that divided the ascent stage with its crew capsule from the descent stage. They then fired the ascent engine and sent the module back toward the CSM, a trip that would take over two hours. McDivitt acquired Gumdrop visually at a range of at 75 km (47 mi). Scott could see the LEM's thrusters, but otherwise it was hard to see the tiny spacecraft, whose tracking light was malfunctioning.

As it approached Gumdrop, McDivitt spun the Lunar Module again to allow Scott to inspect its exterior for any damage. Then, after six hours and 23 minutes of free flight, Spider re-docked with the Command Module. The crew returned to Gumdrop and then the hatches were sealed, the two spacecraft separated, and mission control fired the ascent engine remotely and allowed to burn until the fuel ran out, sending the empty module into a higher orbit.

The last days

The last days of the mission were relatively uneventful. All the main objectives had been met, so the crew concentrated on Earth resources experiments. This involved photographing the Earth in both the visual and multispectral ranges as they orbited over the southern USA, Mexico, Brazil, and Africa. By taking shots in different spectral bands and using different filters, Apollo 9 showed that that space imaging could be a great asset in seeking resources and monitoring pollution – a fact that was useful for later satellite missions and for the Skylab space station in the early 1970s.

On March 13, 1969, Apollo 9 returned to Earth after 151 orbits – 10 days, 1 hour, and 1 minute after launch. The Command Module splashed down in the Atlantic Ocean Northeast of Puerto Rico and about 3.1 miles from the target point. The crew and capsule were recovered by divers and helicopters the aircraft carrier USS Guadalcanal.

After splashdown

In all, Apollo 9 had an impressive list of accomplishments. It proved the Lunar Module was fit for operations and that the crew could handle it in space. It was the first time that two people had gone on EVA at the same time, the first time crew had transferred between two docked spacecraft, and that the two craft could operate together under flight conditions.

Today, the Apollo 9 Command Module is on display at the San Diego Air & Space Museum. The Service Module burned up over the Atlantic shortly after the crew splashed down. Meanwhile, the Lunar Module's descent stage plunged into the atmosphere on March 22, 1969, while the ascent stage remained in orbit until October 23, 1981. The S-IVB is still orbiting the Sun and will continue to do so for many centuries.

But the most significant aspect of Apollo 9 was that all the parts of the Apollo program were finally in place. The CSM, LEM and the Saturn V were all okayed for the Moon. The way was now officially cleared for the final dress rehearsal in lunar orbit that would lead to the Apollo 11 landing in July 1969.

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