At the end of a mission, when an Apollo capsule returned from space and splashed down into the ocean, there were two ways it could float.
One of those was called Stable One, and it's the one that most people picture -- the capsule floats with the pointy end toward the sky, and the big, heavier end in the water. The astronauts are lying back in their seats, facing the top of the spacecraft.
The other position, known as Stable Two, was just the opposite. The capsule could actually also stay floating in a stable manner with the broad end facing the sky and the pointy end in the water. In this position, the astronauts hung from their seats by their straps, waiting for the capsule to be flipped over. After a long space mission in near-weightlessness, this wasn't the most comfortable way to become reacquainted with Earth's gravity.
Needless to say, Stable One was the preferred way of landing.
But considering all that could have gone wrong with the landing of the second manned Skylab mission, 39 years ago this week, ending up in the water in Stable Two was just a minor inconvenience.
The landing issues began not at the end of the mission, but at the beginning, before the crew had even docked with the Skylab space station. On the way to rendezvous, pilot Jack Lousma looked out the window and saw something floating by that looked exactly like the bells for the Apollo spacecraft's maneuvering engines. You don't need astronaut training to know that this would be a bad thing.
As it turned out, what Lousma saw wasn't a thruster. But it wasn't much better. A leak had formed in one of the maneuvering engines, and propellant had seeped out through the engine. It had frozen in the engine bell, and eventually that piece of ice, shaped like the thruster had come loose and floated away. The engine was still attached, but because of the leak, it couldn't be used. The spacecraft used four sets of thrusters to maneuver, and one whole set had to be shut down.
This was a problem, but more on the inconvenience end of the spectrum than the cataclysmic end. The commander could still fly the spacecraft, it was just a little more complicated.
After docking, the situation worsened. Again it was Lousma who saw the problem through a window, this time reporting to his crewmates, Alan Bean and Owen Garriott, that it looked like it was snowing outside Skylab. Since it generally tends not to snow in orbit, there had to be another explanation, and there was -- another engine leak.
The second leak meant shutting down a second set of thrusters. Now the situation was more serious, but exactly how serious, no one knew. NASA was unsure as to whether it was possible to fly an Apollo spacecraft home safely with only two thruster quads.
Vance Brand and Don Lind, the mission's back-up crew, were called into duty. They began working in the spacecraft simulators at Johnson Space Center in Houston, Texas, to determine two things -- could an Apollo spacecraft safely return to Earth with half its quad thrusters shut down, and, if not, could a rescue mission be flown to recover the crew aboard Skylab?
The pair answered the second question first. Yes, if needed, a rescue mission could be launched. It would require some modifications to an Apollo capsule in order to fly. The capsule was designed to hold three astronauts, but flying a crew up to Skylab and bringing the crew there home would require a minimum of five seats. It could be done, but it wouldn't be comfortable. A second row of seats could be installed underneath the top row in the space normally used for cargo, giving the astronauts on the bottom row only a tiny amount of room between them and the seat above them. This presented another problem -- while the Apollo capsules were intended to land in the water, they were designed to, in an emergency, be able to land safely on solid ground as well. To do this, the seats had shock absorbers that would cause them to give in the event of an overly hard landing. With the extra row of seats, this would have caused the top seats to basically collapse onto the ones below them at a high force; not an ideal situation. With no immediate remedy presenting itself, NASA officials decided that the odds of this happening were sufficiently low that it was worth the risk.
With that question answered, Brand and Lind began working on the other question, and determined that the rescue mission they had earned the right to fly wouldn't be needed after all -- with a little bit of clever flying, the crew aboard Skylab would be able to come safely home in the same vehicle they had launched in. Lind, who was only weeks away from flying the rescue mission, ended up having to wait another 12 years for his first trip into space.
All's well that end's well, of course, but it's interesting to consider the What If's, also, like the missions that never flew. Next time you're at the U.S. Space & Rocket Center's Davidson Center, look a little more closely at the Apollo command module on display there, and ponder what it would have been like riding underneath the seats you see. Odds are, you'll never complain about a cramped ride again.
(The full version of this story is included in "Homesteading Space: The Skylab Story," by David Hitt, Owen Garriott and Joe Kerwin, available in the USSRC gift shop.)
Contributing Author: David Hitt
