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1* Why does a film that pretty accurately handles the whole "no orientation in space" thing work off such a 2 dimensional conceptualization of orbit? Every major satellite seems to exist in the same exact hulla-hoop around earth, with the Hubble, ISS, and Tiangong just a short trip by scooty-puff junior away from one another.
2** Very simple: ConservationOfDetail. Cuaron actually put everything in different orbits in his original script, but during filming realized that fully half the dialogue was explaining the very non-intuitive laws of orbital physics to the audience. So he simplified it down - literally doing an AdaptationDistillation on his ''own script.''
3* How can Ryan pick up a ham radio on Earth but no other bigger radio stations?
4** It was stated that the Russian satellite that blew up knocked out all communications devices in the U.S. and elsewhere. I assumed that this had the same effect across major powers who use up-to-date communications technology, but more primitive communications devices would not be affected. Also, her orbit happened to be in a location where she could pick up the signal.
5** Also the ISS has the ability to communicate with ham radio operators, it's not entirely unrealistic to expect the Russians to have the same.
6** Note that communication satellites (and NASA's TRDSS birds) are way, way up in geosynchronous orbit, safe from any low-orbit debris cascade which would affect manned vehicles like the ISS and Shuttle. So this really shouldn't be an issue, but the movie wouldn't be as exciting if Ed Harris was walking our heroine through every step via radio.
7** In a world where an extension of the STS (space shuttle) program was funded, there might not have been funding for the SGSS modernization program, and TDRSS might have fallen into disrepair. They still should have had line-of-sight radio, though.
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9* What exactly was Ryan's role on the mission? I assumed that she had designed the replacement for the Hubble, but later scenes imply that she's a medical doctor.
10** Her role is mission specialist. Generally speaking they are astronauts assigned to perform various aspects on a mission which may or may not have to deal explicitly with their discipline, so while she may have been selected to be an astronaut based on her medical expertise, her role on this flight was to upgrade Hubble. Interestingly Kowalski is implied to be the Mission Commander, which makes it extremely unusual for him to be out on an eva as Commanders generally don't leave the ship at all.
11*** It was Kowalski's last mission, he was just indulging himself with one last space walk.
12** Specifically, she wasn't a medical doctor, but a medical engineer. Her expertise was needed to install some piece of technology used in her profession that also had some unspecified non-medical use for the Hubble.
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14* How on Earth did the Tiangong (The Chinese Station) end up in the atmosphere? It would have had to have been hit by something (which it sure looks like it didn't) or been originally placed right up ''way'' too close to the atmosphere (where it wouldn't be, drag is bad).
15** Pay more attention. It appears to have passed through the same debris field. You can see the damage during approach.
16*** Still doubtful the debris could have hit the station that hard to move it that far without shattering it completely.
17** Considering the Tiangong is on the same plane as the ISS, and therefore in range of the debris cloud, it's possible that the Chinese crew tried to make an orbit correction to ''evade'' the cloud, and either overcorrected in their panic, or simply made a mistake and realized they dipped too low. Then, presumably, they evacuated on another Shenzou.
18*** Equally likely, the Tiangong crew intentionally de-orbited the station in order to reduce the scale of the Kessler Syndrome event they could see unfolding. Less debris = mankind back in orbit sooner. Nice work, guys.
19*** The size of the space station makes it very unlikely that it burns up in orbit. The US Skylab crashed to Earth, the ISS will be split up into pieces and the MIR was deorbited in a targetted manner. They basically launched a giant asteroid at the Earth without an idea where it would land, potentially dooming the Earth.
20*** Not even remotely- Tiangong-2 has a mass of approximately 8.6 metric tons and at its highest orbit reaches 378.4 km. IfMyCalculationsAreCorrect (which they admittedly may not be), assuming it were to remain completely intact during the descent, that would give it an approximate gravitational potential energy of around 0.032 (rounded) terajoules. For reference, the energy released by the Hiroshima bomb was about 63 TJ, or around 1978 times more than that. Would it suck to be in the immediate vicinity? Yes. Would it cause the apocalypse? Snowball's chance in hell.
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22* Why did Kowalski have to detach himself at all? What momentum was continuously forcing him away? The entire premise of the movie was on Newtonian physics, and he was completely stationary at that moment. Wouldn't he need just the tiniest nudge forward and he'll eventually get to the ship? When he unhooked himself, shouldn't he have just remained in position until another force acted upon him?
23** That's because he ''wasn't'' completely stationary. When Stone's leg was caught by the parachute ropes, it tangled up quite a bit; then she grabs Kowalsky's tether, and when ''his'' momentum stretches the line, he starts pulling her in his same vector, and the ropes come undone. Save for one or two distance shots, the camera focuses on the two characters, so from our perspective it ''looks'' as though he's stationary, because the tether is taut, but he's actually pulling her ''free'' of the ropes all the while (remember, he's a more massive object than she is, especially with the MMU on his back.) By the time he lets go, her leg is barely hanging on to one measly loop of rope (as opposed to the aforementioned tangle) so even though his momentum IS being arrested, and their combined mass would have slowed down to a complete stop eventually, he estimated that the ropes would have come completely off her foot before that happened. The fact that the parachute rope ''snapped back'' and flung her back to the ISS (and disentangled itself completely) as soon as his mass was absent is proof of the force he had exerted on her.\
24If it helps, picture the following scenario: a skier stands on the pier, holding on to the tug line. The speedboat sails off at a constant speed until the line is stretched, then it instantaneously starts slowing down but it's not decelerating fast enough to let the line go slack. But ever since the line first went rigid, the skier was pulled along the pier and towards the water. Due to the force the speedboat applied on the skier, the former won't come to a complete stop before the latter falls off the pier.
25** What I fail to understand is why Kowalsky didn't remove his jetpack apparatus and kick it to push him towards the ISS after unhooking himself. This would have given him enough speed to reach Ryan, if not the ISS. Astronauts are trained to do this in a case of last resort.
26*** That is basically what Ryan does when her fire extinguisher runs out of [=CO2=] --she tosses it away to push herself towards the Tiangong. However, she was only a few feet away from it, moving parallel to it, and only needed a slight nudge in a vaguely approaching vector to come within arm's reach (and even then, she almost missed it anyway.) Matt, OTOH, is moving away in a perpendicular vector from the nearest stable structure. Assuming he could have detached the MMU quickly enough, he would have needed the (empty) unit to be massive enough that tossing it away in a ''perfectly parallel'' vector wouldn't just completely counteract his forward motion, it would push him back in an exactly opposite direction. Early [=MMUs=] tend to be bulky, but the frame he wore in the movie doesn't seem much different from [[http://en.wikipedia.org/wiki/Simplified_Aid_for_EVA_Rescue a SAFER module]]. Those are designed to be lightweight and portable. Matt would have had to detach his whole backpack, O2 included, to A: completely counteract his own mass, and never mind B: pushing himself back. It would have been incredibly improbable for him to do A (it's impossible to know his velocity in relation to either Ryan or the ISS) but even then, he would have needed her to anchor herself first, then toss him a line (because waiting for her to get to the Soyuz or even just replenish her own O2 would deplete what little oxygen he had in his suit.) Those are far too many assumptions to make about mass, velocity, and his and Ryan's remaining O2, within the few seconds before he drifted out of range.
27*** That jetpack is certainly more massive than the fire extinguisher. Kicking it away would have given him some delta-v and even a little delta-v at this point would have saved his life to say nothing of shedding the jetpack's extra momentum.
28*** Maybe. Kowalski is a veteran astronaut who knows how things move in space. In his judgement his only option to save Ryan was to untether himself.
29** The RuleOfDrama. The only way Kowalski could've been continuously pulling on the rope was if there was some other force acting on him, but since it's space, there's pretty much nothing to cause the force. However, having an experienced astronaut stick with Stone for the movie would've fixed the plot too easily.
30** There was a strong possibility that it wouldn't work, and I believe Kowalski chose not to try because he didn't want Stone, whose chance of survival was much higher, to attempt to rescue him in any way that endangered her own life. After all, he outright refuses her even attempting to come after him in the escape pod.
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32* If the debris is orbiting at the same altitude as the shuttle and space stations, how can it have a much higher velocity? I've played enough Kerbal Space Program to know that orbits of similar altitudes will always be similar speeds.
33** It could be that the debris are in orbit with high eccentricity, and that their periapsis coincidentally intersects with the shuttle and space stations. You could also have multiple debris, each debris cluster orbiting with different inclinations, if they are that unlucky.
34** Or, the debris is at the same altitude, but orbiting in the opposite direction. (17,500 mph x 2) More likely, the debris itself is in a perpendicular orbit at the same altitude, effectively forming a trail or even a ring that the orbits of the Explorer/ISS and their crews intersect each time they go around the earth every 90 minutes. The relative motion between them would make it seem that the characters in the movie are standing still, and it's the debris that's coming to them but really it's the other way around.
35*** If Explorer/ISS were orbiting one direction at 17,500 mph and the debris field were orbiting the other direction at 17,500 mph (giving each an orbit time of 90 minutes) wouldn't each intersection occur every 45 minutes?
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37* In the Soyuz, it's made clear that the air jets can completely maneuver the pod from all angles. Correct me if I'm wrong, but the fuel and the air jets are two separate things, right? If so, why didn't she just air jettison herself over to Tiangong?
38** The "air jets" are actually the "Reaction Control System" thrusters and they have their own fuel supply separate from the main engine. While they can move the ship around in any direction, they really can't be used to propel it the way the main engine can.
39** So you're saying that it can be done, though? I mean, there's ''no reason'' that she can't use them or at least try using them.
40*** Fun fact: this is a double flub! All modern Soyuz spacecraft have a single engine system, the KTDU-80, which drives both the main engine and the attitude control ("air jets"). So if the main engine was out of fuel, so should the attitude control engines. Of course, it's also highly unlikely the berthed Soyuz would be left without fuel, either.
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42* Why was Ryan Stone sent into space in the first place? It seems like she's there because she invented/designed a piece of technology to be attached to the Hubble. But even if it's her invention, why can't someone else attach it? Training a civilian to become an astronaut is quite expensive, so wouldn't it have been much easier and cheaper to teach a regular NASA astronaut/engineer how to attach it.
43** You're right, it is a little sketchy. Theorizing goes into WMG territory, but maybe she had flying experience, or went to Space Camp as a kid, or was healthy and athletic and had a solid profile for the job. We don't know, though.
44*** She didn't seem to have flying experience; by her own admission, she crashed the simulator Soyuz every single time she flew it.
45*** Its not just that they have a doctor changing circut boards on the HST, its also the fact that she doesnt seem all that stable psychologically. I mean she IS somewhat of a depressive, rather common among americans. But space programs also test astronauts mentally as well. Its unlikely she could hide, or downplay that side of her personality enough to pass a psych evaluation. She displays no particular aptitude for the task assigned that anyone else could perform just as easily.
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47* The ISS has a standard crew of 6; in fact, [[http://www.collectspace.com/news/news-093013a.html the mock patch]] for the then-fictional Expedition 42 has six names on it. If they had to cram themselves into the one intact Soyuz (which seats three), would it be controllable, let alone (given the G-forces) survivable?
48** Maybe some of the ISS crew were killed on its last pass through the debris?
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50* How many kids did Ryan have? After the hallucination sequence she said to herself she was coming home to someone.
51** She "asking" Matt to tell her daughter --her late daughter, since Matt was dead too-- that she was coming home. As in, her own home.
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53* When Ryan changes over to the Russian space suit, where is its oxygen supply,tanks?
54** It doesn't have any. It has, at best, an oxygen feed through the tether. That's what made her ejection from the Soyuz towards Tiangong even ''more'' of a "do or die" than it already was: she only had whatever air was inside the suit, so if she failed to board Tiangong, she'd have suffocated even faster.
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56* How does Ryan even survive the second wave of debris that is actually enlarged compared to the first? I know the obvious answer is "because the film would end otherwise, dummy", but from a rational standpoint it really seems implausible and bugs me. She's outside the space station making repairs in a flimsy suit, and a HUGE cloud of razor sharp shrapnel so dense ''she can see it with the naked eye'' is flying straight towards her and the station at hundreds of miles per hour relative to her speed. Said cloud totally annihilates the station and shreds it into even more sharp pieces. Even one slow fragment from the station could pierce her suit, whereas the hail of ''thousands'' of pieces that she can see flying towards her should in reality turn her into red mist. Even the bits she can't physically see would be travelling fast enough to kill her!
57** Implausible but not impossible. It doesn't happen, don't worry about it!
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