>> Sunday, November 3, 2013
As promised, here's some rocket science for ya.
Now, although it's not true of all rocket scientists, in my particular career, I've made something of a specialty out of telling people stuff they didn't want to know, because, well, that's really what safety engineers do. If someone's excited about their work and progress, and it's all hunky dory, safety people don't have to say anything. But, if it's not, safety engineers get the (not surprisingly) thankless task of telling engineers that their baby is ugly and needs some sort of makeover.
That mindset, looking for flaws, either becomes engrained in some of us, or, as I suspect is true with myself, we gravitate to positions like that because we're natural pick-aparters, devil's advocates, skeptics. And, if we have a thick enough skin (I'm nearly a solid), and stick to our guns, we can actually do good things because many a design has been passed over by enthusiastic supporters (aka reviewers) only to fail cataclysmally in reality. Safety folks, if they have a vestige of a spine, help keep that from happening.
But I digress. What I'm here to do is rain on the parade regarding the science of the movie Gravity. Yes, there will be spoilers, so, if you don't want to read them, stop HERE. Now, of course, the first thing people will tell me is to let it go: it's just a movie. After all, I had a great time watching Iron Man III (and the first two Iron Man movies) and the science is quite thoroughly whacked, though just as pretty (I love watching him don/doff suits). I understand what you're saying, I really do, but there's a reason I don't just let it go for Gravity and actually enjoy the Iron Man nonsense, and I'll explain why at the end (which will probably be in a later post).
Gravity is a very pretty movie, with excellent effects, notably the space scenes, and some fairly effective acting. The zero-g footage was particularly spectacular and well-done. When the ISS broke up, the movements involved, including the way the oscillation caused bending moment effects was pretty cool and likely based on some fairly correct physics. Orbital debris is also a significant risk for space vehicles, particularly those in low earth orbit as all the space stations, Hubble Space Telescope and the Shuttle (when it flew) were tied to. In principle....more on that later.
Aside from that, there was almost nothing that was right.
First, I think the movie owes astronauts and the people who train them an apology. The main character, whose name I forgot, is a strong female protagonist and scrappy, etc., which is great, in theory. However, she is also far more ignorant of basic EVA protocol, space information, science, training, etc. than any astronaut I've ever met, including those who were never planning to go EVA. EVA, in particular, is my baby, so let me point out a few things.
- First of all, you DON'T go out spacewalking while nauseous because puking in the suit=dead astronaut. That's why they don't do spacewalks the first few days after launch so they can get acclimatized to the zero g (which sets many a tummy a-flutter), which means, if they were late in the flight, as they were supposed to be, if she were still so nauseous they would not LET her go out and would probably be worried she had something else wrong with her.
- Secondly, one doesn't send out three astronauts at the same time without desperate need. Sending three astronauts out would have to be for a heckuva a reason (only once, in the entire history of spacewalking, has anyone (US, Russia or China) sent out three spacewalkers at once [STS-49 to try to retrieve IntelSat IV F-3 - which they managed to do]). We don't send out three at once for the very good reason that everything is designed for a pair. There are connections for two suits in the airlock (which has to hold a suit tech and two suited crewmembers and is probably smaller than your shower stall). We don't send out just one person any more either, but pairs have managed to get the job done over and over again.
- If one were desperate enough to have to send out three EVA crewmembers, it certainly would not be to piddle-poo around with a jet pack that looks amazingly like the Manned Manuevering Unit, that stopped flying before I started working in the space industry in 1989 - (flew in 1984 only). And certainly not on a Hubble Servicing Mission, given that those are always wall-to-wall back-to-back EVAs (where, interestingly enough, no one has enough free time to go bouncing up and down on his safety harness - shudder). They do those missions with a staff of four EVA astronauts that go out in pairs on alternating days (because doing EVAs on successive days is tremendously tiring - EVAs are hard physical labor working against the pressurized suit, mean usually 16 hour days [at least], and are taxing to hands in particular). And, on HST, much like they do on ISS, EVA crewmembers work their tails off each EVA and have half a dozen other tasks to do if they miraculously get finished early.
- EVA crewmembers are drilled continuously and at great length, both on safety requirements, contingencies and actual tasks in the Neutral Buoyancy Lab. Preferably 10 hours in the water for every one on orbit. This is particularly true on something like HST where they EVAs are packed, challenging, gruelling and frequently run into snags. The crews that perform EVAs (and I know it from personal experience with HST) are smart as hell, driven, capable, knowledgeable and professional. I personally was a little offended on their behalf at the behavior of the crewmembers in the movie.
- And, no, crewmembers do not bounce back and forth on their tethers for entertainment, because (a) that's stupid, (b) they don't have time, and (c) most importantly, it's not safe. Crews count on the tethers to save them if they get separated, but bouncing on that puts forces on them, adds to the risk of them rubbing on something (and failing when you need it) and also imparts forces on the ship you're attached to, which is trying to hold the arm and HST still at the same time.
- You don't manipulate computer boards on EVA for a couple of reasons, not the least of which is that pressurized gloves don't have that kind of dexterity. The gloves are ballooned out and you have to work against them without being able to really feel what you're manipulating. But, far more importantly, circuit boards are covered with sharp edges, those little solder-tipped spots where ICs poke through. In a suit where glove material can be torn open with anything even vaguely sharp, no way you'd handle a circuit card or slide it into a card cage with all those resultant pinch points. I might add the HST folks that design those challenging EVAs are very cognizant and work very hard to make all the unusual equipment they send up EVA friendly and safe. But, if they had managed to send this contraption, it would never have gotten past the crewmembers or me or any other EVA Safety Engineer.
- When they tell you to come in because there's danger, you do it. No one is more cognizant of how close to death they are than an EVA astronaut. Space is completely unforgiving and there's no second chance if your suit fails catastrophically.
- Even if the airlock wasn't sound (and with the catastrophic damage to the shuttle, I wouldn't trust it either), the system to provide power and oxygen to the suit via umbilical in the airlock might still have worked. Given how low her oxygen was, I would have tried that before setting forth for the station (if that were viable, which it isn't - more on that later). Still, there is an emergency oxygen supply, intended to provide oxygen in case of a "hole in the suit" scenario. Not saying you want to use it, but this is probably sufficient emergency to justify it. It's not unnexpected, with the hyperventilating, that her oxygen went low first, but the CO2 would also also likely gone up since CO2 scrubbing capability and oxygen supply are generally about the same capability.
- As has been noted by others, crewmembers do not don the suit in just their skivvies. They have socks and diapers, and, most importantly, a liquid cooling garment, necessary to keep from dumping a liter of sweat out when they doff the suit (as happened on EVAs before we had the liquid cooling garment). No argument, though, that the skivvies look better on the big screen.
- Orlans, the Russian spacesuit presumably stored in the Soyuz capsule, would be plenty heavy to sink like stone in water (120 kg), but doffing it, since you slide out the rear swifter than most spacesuits, rather than peeling them off like long johns, still would take five minutes, even if you could get it open in the pressure of underwater.