February 06, 2016

On Spaceflight

A few days ago, I happened across this article that describes a hypothetical plan that might have been attempted to rescue the crew of the Columbia shuttle, destroyed on re-entry in 2003. Apparently, the plan described therein was an appendix to the official report on the crash. (I don't like to use nouns like 'tragedy' to describe such events, though they are certainly that. Such a choice of words seems to me to emphasize the emotional dimension of the event a little too much. Perhaps in a different context, I might describe it thus--but not on this occasion.) It's the most absorbing reading I've found this week.

Granted that the Ars Technica writeup is in the character of a paraphrase--I admit that I haven't looked over the original source material yet (but see below)--it's quite a fascinating read. I even went so far as to recommend it to the attention of the Big Boss at work (one is naturally a little shy about sending him things like unsolicited Web links). He commented that it was very interesting in a reply the same day, which is something coming from him. I'd thought he might save the link for weekend 'light reading', but I guess he got to it sooner than that. I figured it would appeal to his interest in logistics, contingency planning, and the ramifications of tight deadlines (in this case literally drop-dead due dates) in a team situation.

One thing that I found very instructive was the discussion of the lithium hydroxide canisters that are used to sequester carbon dioxide on board the spacecraft. I always thought the problem would be running out of air as such, but instead the chief bottleneck turns out to be CO2 buildup in a confined space. This strikes me as a good example of a hidden bottleneck, i.e. a critical limiting factor whose presence and significance wouldn't be terribly obvious to a layman. I don't yet understand the charts showing the CO2 partial pressure traces, but I'll work on that.

Just now, I downloaded the source material of CAIB Report Appendix D.13, which can be found here. Reading that reveals additional aspects of the rescue concept which the Ars Technica writeup didn't cover. I'll make some random comments and point out some interesting (to me, at least) details:
  • There were live animals apparently on board Columbia as part of some experiment or other, which would have had to be put down by the crew (sad but necessary) in order to extend the life of the LiOH canisters.
  • A couple of ideas for onboard repair of the breach in the wing edge were floated, which might or might not have worked, but that there was even a possibility of such a thing is a good example of resourceful thinking.
  • A sketch of the EVA procedure by which the crew could have visually inspected the wing edge is given. It sounds awkward to perform: two crew members needed outside the craft, the first with towels wrapped around his boots to keep the soles from scratching up the wing surface any further, and the second using the first astronaut's body as a stepladder to get a view of the spot on the wing where the damage was suspected. No EVA cameras on board for that mission?! I presume those made their way into the standard equipment list in short order after the crash. Even a selfie stick would probably have helped.
  • There's a minor typo in the labels of the x-axis of Figure 4.
  • The arrangement of the two shuttles at rendezvous would have been with the bay doors open and facing each other at a 90-degree relative angle, 20 feet apart. It reminds me of the scene from an episode of Star Trek: Enterprise involving the two ships flipped upside down respective to each other and a temporary flexible bridge between them. (I never actually watched the series with any regularity--caught that scene on YouTube one time.)
  • EVAs are apparently not simply a matter of donning a spacesuit and depressurizing the airlock--not that those steps are simple in themselves, either, but there is some kind of 'prebreathe' procedure, the purpose of which is to get the astronaut acclimated to the altered pressure and composition of the internal atmosphere of the sealed suit. In order to have enough time to transfer the Columbia's entire crew to Atlantis, the prebreathe step would have had to be abbreviated. Thinking back to the EVA scenes in 2001: A Space Odyssey, as agonizingly and realistically slow as those seemed to be, I guess this whole process of crew transfer, passing the suits back and forth through open space for reuse, etc. would have been even more so.
  • If an in-orbit repair of Columbia had been essayed, and assuming success, there was then the question of how and when to bail out upon reentry. NASA staff modeled the thermal profile of the wings depending on angle of attack and apparently worked out that the crew would have fared best if they could manage to get down to 34,000 feet before bailing out.
  • In the summary list at the end including a breakdown of all of the steps in every part of this procedure, in the final Appendix E "Rendezvous Burn Plans", there is a comment by one of the authors directed to someone else on the panel named Richard, which wasn't scrubbed during editing: "Richard, this case [February 13 rendezvous target date] would involve some fancy IY generation." A small point of amusement.
From a technical point of view, Appendix D.13 is at least as interesting as Ars Technica's gloss thereof.

In contemplating all this material, I'm struck by how incredibly complicated real spaceflight is. What we see in even the most technically advanced and realistic sci-fi movies and TV is almost laughably simplistic compared to what this report described. If all you know is Star Trek and such, you can't help but be stunned by the multitude of steps involved in even the simplest activities in space. At least 2001 began to approach these realities. I haven't seen Gravity or The Martian, but I suspect that these may also have made some contribution to a (more) realistic view of space travel in the popular mind.

While I was already a fan of Star Trek: The Motion Picture for various reasons, having read this report makes me appreciate that film a little more because of its incidental illustrations of the dangers associated with space travel even in that otherwise rather antiseptic and utopian version of the twenty-third century: the transporter accident that killed the Vulcan science officer, Sonak, and the wormhole incident that nearly destroyed the Enterprise before the mission could even begin. It's strange that The Next Generation pretty much eschewed even that relatively easy level of realism. Oh, sure, there were episodes driven by warp-core containment failures or similar, but essentially these were resolved or at least resolvable in principle via a few button pushes--no real elbow grease required.

The amount of effort required just to get a few astronauts or cosmonauts into near-Earth orbit or to the moon is astounding to the uninitiated. Take a look at this associated article about underwater mission training for astronauts to get a further idea of all the behind-the-scenes preparation involved. How much more tricky would it be for us to get to Mars? As someone pointed out somewhere, the hardest part of a journey in space is getting from the Earth's surface to the initial orbit. Everything after that is relatively simple, I suppose. The intellectual brilliance that NASA and the ESA and similar organizations bring to these problems is amazing.

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