Once they had the spacecraft upright and stable, a dye was released into the water if required, to aid search and rescue, and the post-landing vent (PLV) could be opened to let fresh air in. Mindful of NASA's need to keep supposed lunar bugs at bay, Collins, while somewhat sceptical of the fear, tried his best not to leave the vent open. ''The big item for us was that we not contaminate the world by leaving the post-landing vent open. We had that underlined and circled in our procedures to close that vent valve prior to popping the circuit breakers on panel 250. I'd like to say for the following crews that they pay attention to that in their training. If you cut the power on panel 250 before you get the vent valve closed, in theory, the whole world gets contaminated, and everybody is mad at you.''

Dick Gordon pointed out how this vent gave the Apollo 12 crew, floating on heavy seas, more minor problems. ''The procedures say, of course, to open the PLV ducts. With that rough water out there, when we did, we just took water in through the intakes and that fan just blew it into the spacecraft. After a while, we got tired of getting wet so we just turned the PLV duct off. We just turned it off, and then when we got real warm again, I turned it back on just to let some more air in.''

The crew released their restraints and began powering down the spacecraft while the recovery forces swung into action. A typical recovery force had five helicopters deployed from a US Navy aircraft carrier that was stationed at the spacecraft's aim point. As spacecraft crews and their support teams gradually improved their re-entry guidance and landing became more accurate, recovery planners began to worry that the CM might make a hard landing on the carrier itself, so for later missions, the carrier stationed itself a few kilometres to one side of the aim point. Each of the five helicopters had a specific task in the recovery. One was intended to photograph and later televise the splashdown from close quarters. Another had little more to do than be a radio relay between the CM, the helicopters and the ship. Two further helicopters had frogmen on board whose task was to drop into the sea and attach a

Jack Schmitt exits Apollo 17, helped by a Navy swimmer.

flotation collar around the spacecraft that would both stabilise it and provide a platform for the exiting crewmen. They also recovered the detached parachutes if possible. The fifth helicopter carried a 'Billy Pugh' rescue basket with which it would pluck the three crewmen, one by one, off a life raft next to the spacecraft and into the helicopter to be taken to the ship.

Inside the spacecraft, the crew charged a gas-powered counterbalance for the main hatch in preparation for opening. After the Apollo 1 fire, the two-piece inward-opening hatch of the Block-I spacecraft was replaced with a single unified hatch that could quickly be opened outwards. A problem with this arrangement was that while sitting upright on Earth, the heavy door had to move against gravity so an ingenious counterbalance arrangement was added that was powered by compressed air bottles.

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