Just arrived in Houston after a long flight in which I had time to jot down some final words on Gravity. Please see yesterday’s Logbook L-418 and especially Monday’s L-420 for my general thoughts on the movie. The short story is: go see it, it will be a great aesthetic experience and a close encounter with some amazing space hardware that we really operate in orbit. Right now.
As mentioned before, hardware rendering is amazingly realistic, events and operations not as much. Here are some more thoughts on that (Spoiler Alert!)
12) Flying a rendezvous
You’re sitting in your tiny Soyuz and want to fly to the International Space Station? That’s done four times a year, by the way – every time a new crew is launched to Station. It’s called rendezvous and it’s technically what Dr. Stone tries to do when she aims at the ISS Tiangong and attempts to fire the Soyuz main engine. Except that it doesn’t work that way.
Let’s say that you are trailing behind the Station. In order to catch up, you need to be in a lower orbit. Here’s the trick: every orbit has its own specific orbital velocity. The lower you are, the faster you go. So, if you are on a lower orbit than your target, you catch up: we call that phasing. Then at some point you need to come up to your target’s orbit. For that, you’ll give two posigrade burns (meaning forward) at two precise moments. That, believe it or not, will end up making you slower. But it will raise your orbit, so you’ll have achieved your goals: reach your target and matched its slower velocity. You get the point: even in the simplest possible case that I have just described, a rendezvous involves firing the engine multiple times in burns of extremely precise orientation and duration. No “aim and fire” here!
13) Can’t trick the Soyuz…
… into thinking that it’s 3 meters from the ground. There is no control format to manually input height-above-ground and the soft landing rockets are fired automatically by command of a radar altimeter. Moreover, to expose them not only you would have to separate the Soyuz modules (which they did, I liked that!) but you would also need to detach the heat shield that protects the bottom of the descent module during re-entry. And, you guessed it, that also happens automatically.
14) Riding the fire extinguisher
Never mind that we don’t have a side hatch in the Soyuz descent module (why would you need one?), but what are the odds of making it to ISS using a fire extinguisher? I remember an old tire ad that said “Power is nothing without control”. In this case I would say “Thrust is nothing without control”. Let’s say you want to move straight backwards. First of all, you need to make sure that you orient your body so that your target is straight behind you (how?). Then the firing direction of the extinguisher needs to be perfectly aligned with the center of mass of your body/suit system. If it’s only slightly misaligned, you will inevitably spin. As soon as you start spinning, your target, that we assumed you were somehow able to put right behind you, will not be behind you any more… start to see a problem here?
15) Reentry
When we practice reentry in the Soyuz simulator in Star City there is one thing we need to do no matter what, in spite of the instructors throwing at us combinations of malfunctions worth of, well, a movie: we absolutely have to give a braking burn in the correct orientation and with the required ΔV. In a nutshell that means that we slow down just as much as needed to encounter the atmosphere at the proper angle. Why is that important? Well, that happens to be the key to our getting home in one piece. I’ll let you be the judge of whether the apocalypse-day type of scenario depicted in the movie could have ended well for Dr. Stone.
16) And finally…
…let it be known that the Russians are no fools and certainly no newcomers in the spacefaring business. I guess one could argue that they invented it. This space debris catastrophic cascade reaction is unrealistic as it is. That the Russians, who have three crewmembers on ISS all the time, would cause it, is nonsense!
There were of course many more little things, from the drop of partial oxygen pressure in the descent module without overall drop of pressure to getting out of the Sokol suit under water in a few seconds (it’s really not a quick-doff suit, as you can see in the picture), but I’ll call this done from my side. Getting back to my own training tomorrow!
Doffing a Sokol suit.
(Trad IT) Traduzione in italiano a cura di +AstronautiNEWS qui:
https://www.astronautinews.it/tag/logbook/
(Trad ES) Tradducción en español aquí:
https://www.intervidia.com/category/bitacora/
(Trad FR) Traduction en français par +Anne Cpamoa ici:
https://anne.cpamoa.free.fr/blog/index.php/category/logbook-samantha
11/10/2013