WHIFFERDILLS. A series of posts at Voluntary Xchange put Wally Schirra's contribution to the space program in context. Commander Schirra's commitment to precision with Sigma 7 secured him a slot on the Gemini project.

He ended up on the A list for the next program, Gemini. By that point, of the original 7 astronauts, 2 had been grounded for medical reasons (Shepard and Slayton), 1 had been grounded for political reasons (Glenn wouldn't be allowed to risk his life a second time), and 2 were B listed for being perceived as flippant either on their mission (Carpenter) or on the ground (Cooper).

(Gosh, did Senator Glenn get himself un-grounded for political reasons?)

The post I found most intriguing was that for Gemini.

Space travel is extraordinarily costly, and it is always cheaper if you have less weight. The NASA plan from 1962 had been for lunar orbit rendezvous: basically to throw stuff away along the way. The Moon mission would be composed of 4 big parts: 1) a launch rocket to get the other 3 pieces on their way, 2) a lunar orbiter to launch the other two down to the moon, 3) a lander, and 4) a return vehicle consisting of the top half of the lander. The last would be jettisoned too, after rendezvous with the orbiter, which would return to Earth on its own.

So, basically, if rendezvous and docking weren't proved possible with Gemini, the design that NASA was already committed to wouldn't work. On the other hand, the Russians were always pursuing the direct ascent or Earth orbit rendezvous of huge rockets. They never were able to make it both big, and workable, so in a very real sense the race to the Moon was over with the working out of rendezvous and docking on Gemini 6 and 8. Of course, no one knew that at the time.

Coupling and uncoupling a space train, which the good people at NASA refer to as "docking" and "undocking," is no easy feat.

So anyway, you have to get two craft into the same spot in the same orbit. Sounds easy. It isn't. The problem starts if they are in the same orbit but different spots. Ahh, you say, just have the one in front hit the brakes, and ouila, rendezvous. But, orbital mechanics doesn't work that way. When you hit the brakes you drop down to a lower (and different) orbit; when you speed up you go to a higher one. To further complicate things, doing either changes the shape of your orbit: hitting the gas stretches it out, while hitting the brakes flattens it.

What you have to do is this. First off, don't let anyone touch the gas or brakes in the one spacecraft. Then the other spacecraft either has to start in a higher orbit and hit its brakes to drop down to the other craft, or it has to start in a lower orbit and hit the gas to rise up to meet the other ship.

But, it gets worse. I know this sounds crazy, but when you hit the brakes (to slow down), you drop into a lower orbit where gravity makes you go faster. Alternatively, hitting the gas actually slows you down.

Commander Schirra did not do the flying. Gemini and Apollo Astronaut Mike Collins's Carrying the Fire describes rendezvous and docking from the pilot's point of view. The usual Gemini solution was for the trailing ship to catch up in a lower orbit, then do a burn to simultaneously rise to a higher orbit and slow down, although if one were not careful, one would wind up in a spiral around the path of the leading ship, which the astronauts referred to as a "whifferdill," and one would use a lot of fuel recovering from that maneuver. (Perhaps part of learning how to use the Force is mentally training yourself not to make a whifferdill, although that appears to be a standard maneuver on an x-wing fighter??) Some of the scarier moments in the Gemini missions involved rendezvous and docking maneuvers, particularly with those supposedly-passive Agena target vehicles.

Without the ability to rendezvous and dock, the space program would be in a position where a safe landing on the moon is possible (our British railroading colleagues had a maneuver called the "slip coach" that generalizes to orbital mechanics) but the safe return part wouldn't work. As track-planning guru John Armstrong noted, the British never worked out a way to couple the slip-coaches to expresses on the move.

Then comes Apollo, where one of the early lessons learned is that of being able to cooperate under trying conditions.

What did go wrong was the health of the astronauts - all of whom developed colds during the trip. This made them all testy, with each other and with mission controllers back on Earth.

Internal politics of NASA are hard to decipher, but none of the three astronauts on this mission ever flew again. This seems harsh, but it is sensible. Part of what was being tested was the ability to get along with everyone while spending 1-2 weeks in what amounts to a sub-compact car with two other guys who aren't bathing.

The tolerance of the astronauts was really a key issue in the Apollo program; this turned out to be critical for Apollo 13, which was severely disabled about 80% of the way to the Moon. In that case, a "lifeboat plan" which had been made under the assumption of carrying two men back over two days had to be modified on the fly to bring 3 guys back over a 4 day period.

Currently, our Mars project planners are contemplating sending couples on interplanetary missions, for what seem like eminently sensible reasons. (Houston, we request 30 minutes radio silence for a rendezvous-and-docking.) What happens, though, if one of those couples decides, somewhere near the asteroid belt, to call it quits?