Wednesday, April 23, 2008


OK, this item has me perplexed.

Here's a summary of the situation: The Soyuz TMA-11 capsule was returning from the International Space Station with a crew of three. The pilot -- the CNN article calls him "flight engineer", but he's a rated pilot, and besides, somebody's gotta work the stick -- was Yuri Malenchenko, along with returning ISS commander Peggy Whitson and South Korean astronaut Yi So-Yeon. But "something" went wrong during re-entry. According to the report, the capsule landed 260 miles off-target, and twenty minutes late.

Say what?

Initially, that was all I knew, and it made absolutely no sense me. Off-course I can understand, but how the purple roaring hell do you land twenty minutes late? If you're twenty minutes late firing your retros, you're not missing by 200 miles, sport, you won't even hit the right continent. And if you're only 200 miles off, it's an overshoot or undershoot, and dammit, I just couldn't figure out where you eat up twenty minutes during descent.

Until some other information came out in this report, that is. That made everything clear. No one's saying for sure, but I'm fairly certain what had to have happened. It turns out that (1) there was some heat damage to the front hatch, and (2) they experienced 8 Gs during re-entry.

"Oho," says I, "This sort of thing has happened before..." Well, sort of.

The Soyuz 5 re-entry also landed way off-course, and also experienced large re-entry forces, as a result of an unusual re-entry attitude. No mention about timing, though, which is to be expected. But, given this precedent, this is what I think happened.

One of the few flies in the ointment of an otherwise well-honed design is that the Soyuz capsule is perfectly happy flying forward during re-entry. It's an aerodynamically stable configuration. With Apollo, weight distribution trumps aerodynamics, essentially forcing it to fly butt-first during re-entry. And once you get established butt-first, the Soyuz will stay that way once it's properly spin-stabilized. But if something screws that up...

Kudos are due to Yuri Malenchenko, because he probably saved their lives. He had the training and experience to recognize the situation, and was able to act quickly enough to achieve a survivable re-entry and landing. That's fine stick-and-rudder work by anyone's standard. You, sir, are one steely-eyed missile man.

In any case, getting unstuck from their nose-first posture probably caused them to skip off the upper atmosphere briefly, altering their final descent to a much steeper profile than they had originally planned. And while eight gees aren't fun, they're easily tolerable to a fit person, even one debilitated by a long stretch of free-fall. And yeah, I can see that kind of path taking some extra time, accounting for the twenty minute delay in descent.

All in all, I'm somewhat less than shocked. Re-entry, as I've said before, is always a hand of Texas Hold-'Em with the Grim Reaper. When you do everything perfectly, you can stack your hand with aces. When you don't, well, you pays your money and you takes your chances. I'm just glad they all made it back home this time.

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