6 ms·

What Happens If an Astronaut Floats Off in Space? (2013)

27 points by nomilk 5y ago

inglor_cz 5y ago
Gravity had a stunning setting, but the bad physics tugged on my nerves all the time.
- BitwiseFool 5y ago
  Kerbal Space Program has ruined my ability to suspend disbelief when watching things move around in space.
tyingq 5y ago
Death by asphyxiation after the oxygen runs out, I suppose. I'd be scheming ways to route the nitrogen propulsion into the suit for a less traumatic death.
- 0_____0 5y ago
  Oxygen running out would be the same as breathing an inert gas atmosphere... it's the CO2 that gets ya [edit: my point, less flippantly stated, is that mere hypoxia isn't as stressful as having your breathing gas fill up with CO2, as CO2 is what creates the breathing panic reflex.]
  - tyingq 5y ago
    I believe oxygen running out would mean the suit is no longer pressurized. I assume that is traumatic. The description of the Soyuz 11 autopsies seems to confirm that (brain hemorrhaging, high lactic acid, etc).
  - skhr0680 5y ago
    I recall reading about workplace accidents where (inert gas) displaced oxygen and workers didn’t notice until they literally started dropping dead
    - 0_____0 5y ago
      Yep. That's one reason you see people sort of standing around worksites. Got someone down in a manhole or crawlspace? Someone has to be monitoring and communicating with a worker in a confined space for exactly this reason.
rob74 5y ago
Wow, it's already 8 years since Gravity came out, time really flies! Despite all of its possible failures, I still consider this the film that makes the best use of 3D that I have seen so far - it really immersed you into the action, you had the feeling of actually being up in space or in the slightly claustrophobic space capsules and stations with the protagonists.
svantana 5y ago
Here's a random thought I've had: if an astronaut jumps off the ISS at exactly the right angle and speed, he could collide with the ISS again after one period. The period is given by the area of the orbit, so it should be straightforward to solve for the angle given a jumping velocity, an orbit and a current position. Something for Felix Baumgartner to consider...
- exDM69 5y ago
  If the astronaut jumps directly to the direction of the orbit normal at any velocity, it will end up in an orbit with equal period but slightly higher inclination, and meet the space station twice every orbit 45 minutes apart at the ascending and descending nodes, ie. where the orbital planes cross. Any other direction is more difficult as a significant velocity change is needed to get into an orbital resonance. E.g. 2:1 resonance with an 180 minute orbit where astronaut orbits twice for every 90 minute orbit the ISS makes, meeting at the astronaut's perigee or lowest orbit point. Other fractions also work for a more infrequent encounter.
  - goalieca 5y ago
    Now i want to try that experiment with a ball. Just nudge it gently and then wait to catch it.
  - svantana 5y ago
    > If the astronaut jumps directly to the direction of the orbit normal at any velocity, it will end up in an orbit with equal period That's obviously false for e.g. escape velocity, and by continuity also wrong for lower velocities.
    - exDM69 5y ago
      Yes, this is a small impulse approximation, which assumes that astronaut jump velocity is small compared to orbital velocity. Practical matters (mass) prevents instantaneous impulse to escape velocity in practice.
2OEH8eoCRo0 5y ago
Would you burn on reentry if you managed to deorbit yourself?
- baseballdork 5y ago
  Almost certainly. You'd be going almost 8km/s in low earth orbit. When your body reenters, it's going to experience the same compression heat as anything else moving several kilometers a second entering the atmosphere.
- peeters 5y ago
  Well if you managed to deorbit yourself you've already broken all physical laws, so it's difficult to say what would happen after.
dr_traktor 5y ago
> At the right angle and velocity, you might even fall back into Earth’s atmosphere and burn up. That's highly unlikely. Scott Manley has a video [1] examining whether an astronaut could deorbit a small object with human power, and not really. And that's something small, not a massive thing like an astronaut. Fun video though. [1]: https://youtu.be/cxNJoaBLLNM https://youtu.be/cxNJoaBLLNM
gameswithgo 5y ago
I am reminded of my favorite web comic, The Land of Upp: https://www.penny-arcade.com/comic/2006/08/02 https://www.penny-arcade.com/comic/2006/08/02
rlpb 5y ago
"Then NASA’s plan dictates that you take manual control and fly back to safety." I believe that visually flying back would be extremely difficult unless you're already quite close. The further you are away, the more you'll be thwarted in your efforts by orbital mechanics acting in counter-intuitive way. Unless you have a good understanding of orbital mechanics and can apply it to your advantage by using just your eyes. I wonder if NASA has any plans or provides any training around this.
- jakemoshenko 5y ago
  I imagine that NASA trains its astronauts in orbital mechanics.
  - sxp 5y ago
    They did after the first attempt to dock by just winging it failed: https://en.wikipedia.org/wiki/Space_rendezvous#First_attempt_failed https://en.wikipedia.org/wiki/Space_rendezvous#First_attempt...
fitblipper 5y ago
I'm no expert but this part seems to stretch science into hollywood sensationalism: "At the right angle and velocity, you might even fall back into Earth’s atmosphere and burn up." There is a Scott Manley video that describes orbital mechanics well where he covers if someone could throw a ball from orbit back to earth. https://www.youtube.com/watch?v=cxNJoaBLLNM https://www.youtube.com/watch?v=cxNJoaBLLNM It is pretty clear that the best one can do is throw the ball directly backwards which would slightly decrease the orbital height on the opposite side of the earth. I can't imagine someone drifting off a structure faster than someone could hit a golf ball so it seems extremely unlikely that falling back to earth and burning up would be an outcome. I love Kerbal Space Program and find orbital mechanics interestingly counterintuitive so please correct me if I am wrong.
- fennecfoxen 5y ago
  The thing to remember is in a low earth orbit, your orbit has you moving around 8 kilometers per second. So even before we start getting to the counterintuitive parts (higher is slower, lower is faster, etc) take a moment and think about that 8km/s figure by itself. Consider a token 1% of that amount: 80 m/s (~180 mph). Do you think your orbit has more than a 1% margin before your craft plunges into the atmosphere? (I certainly expect it does). Does this seem like a reasonable speed you could get to using your personal astronaut propulsion device? I don't actually know, but it certainly challenges my image of astronauts zooming around a space station at speeds that would make a kick-scooter look fast.
  - jkelleyrtp 5y ago
    Since there's no drag, you can accelerate as much as you want given the fuel in your pack. In fact, propellant is talked about in terms of Detla-V (delta in velocity). It seems like the first models of cosmonaut suits gave about 70 m/s of DV while the most recent astronaut MMUs give about 25m/s [1]. So, I don't think an astronaut could de-orbit themselves with just their suit alone. [1] https://en.wikipedia.org/wiki/Manned_Maneuvering_Unit https://en.wikipedia.org/wiki/Manned_Maneuvering_Unit
    - 5y ago
tzfld 5y ago
What about having a large enough module on a space station, and you simply stuck in the center of it, just floating and cannot push/pull yourself anywhere?
- BeeOnRope 5y ago
  You could throw something one direction so you float in the other.
  - deleted 5y ago
    [deleted]
- jakemoshenko 5y ago
  This seems impossible to me without a bad actor being involved. How did you get stuck there in the first place? In one scenario you departed from a wall or hand hold somewhere and air resistance slowed you to a stop in the middle. In that case, you should be able to swim through the air given enough time. In the other scenario there is no air in the space station, and as far as I can imagine, the only way to have gotten there with zero velocity would be for someone or something to place you there. Then presumably you could ask that same someone or something for help getting back. There are some nightmare scenarios involving malevolent robots or rooms so large and velocities so slow that you would die before you made it to the other side that are pretty terrifying to consider.
  - devenson 5y ago
    You could accidentally throw your last throwable object which zeros out you velocity, leaving you hopelessly stuck.
    - jakemoshenko 5y ago
      Good point, then you are the bad actor!
- throwaway0a5e 5y ago
peeters 5y ago
In the context of Gravity this omission kind of makes sense, but the article ignores the ability of your ship to pick you up. The RCS of orbiting ships is extremely precise. As long as they know your relative velocity they'd be able to manuever back to you. > At the moment, there’s no spacecraft to pick you up. The only one with a rescue-ready air-locked compartment—the Space Shuttle—is in retirement. Then how'd you get into space in the first place in this hypothetical?
- mschuster91 5y ago
  > Then how'd you get into space in the first place in this hypothetical? Outside ISS mission going bonkers - a tank rupturing leading to an unfortunate astronaut getting catapulted off, for example.
  - peeters 5y ago
    Yeah I can definitely think of catastrophic scenarios where a ship couldn't help you, it's just the article makes it sound like an impossibility. > However, if the pack’s three pounds of fuel runs out, if another astronaut doesn’t quickly grab you, or if the air lock is irreparably damaged, you’re in big trouble. No protocols can save you now. Perhaps the author meant and there. If SAFER stabilizes you but you don't have enough fuel to get back to the ship, the ship could possibly still get back to you.
villgax 5y ago
I am surprised that there isn't anything like Stark technology, to go out of one of the pods and retrieve you autonomously maybe even the Dragon could be repurposed for such things.
deleted 5y ago
[deleted]
underseacables 5y ago
I thought protocol was that there was nothing you could do. They just keep going
z3ncyberpunk 5y ago
You die. Case closed.

27 points by nomilk 5y ago

inglor_cz 5y ago

Gravity had a stunning setting, but the bad physics tugged on my nerves all the time.

BitwiseFool 5y ago
Kerbal Space Program has ruined my ability to suspend disbelief when watching things move around in space.

tyingq 5y ago

Death by asphyxiation after the oxygen runs out, I suppose. I'd be scheming ways to route the nitrogen propulsion into the suit for a less traumatic death.

0_____0 5y ago
Oxygen running out would be the same as breathing an inert gas atmosphere... it's the CO2 that gets ya [edit: my point, less flippantly stated, is that mere hypoxia isn't as stressful as having your breathing gas fill up with CO2, as CO2 is what creates the breathing panic reflex.]
- tyingq 5y ago
  I believe oxygen running out would mean the suit is no longer pressurized. I assume that is traumatic. The description of the Soyuz 11 autopsies seems to confirm that (brain hemorrhaging, high lactic acid, etc).
- skhr0680 5y ago
  I recall reading about workplace accidents where (inert gas) displaced oxygen and workers didn’t notice until they literally started dropping dead
  - 0_____0 5y ago
    Yep. That's one reason you see people sort of standing around worksites. Got someone down in a manhole or crawlspace? Someone has to be monitoring and communicating with a worker in a confined space for exactly this reason.

rob74 5y ago

Wow, it's already 8 years since Gravity came out, time really flies! Despite all of its possible failures, I still consider this the film that makes the best use of 3D that I have seen so far - it really immersed you into the action, you had the feeling of actually being up in space or in the slightly claustrophobic space capsules and stations with the protagonists.

svantana 5y ago

Here's a random thought I've had: if an astronaut jumps off the ISS at exactly the right angle and speed, he could collide with the ISS again after one period. The period is given by the area of the orbit, so it should be straightforward to solve for the angle given a jumping velocity, an orbit and a current position. Something for Felix Baumgartner to consider...

exDM69 5y ago
If the astronaut jumps directly to the direction of the orbit normal at any velocity, it will end up in an orbit with equal period but slightly higher inclination, and meet the space station twice every orbit 45 minutes apart at the ascending and descending nodes, ie. where the orbital planes cross. Any other direction is more difficult as a significant velocity change is needed to get into an orbital resonance. E.g. 2:1 resonance with an 180 minute orbit where astronaut orbits twice for every 90 minute orbit the ISS makes, meeting at the astronaut's perigee or lowest orbit point. Other fractions also work for a more infrequent encounter.
- goalieca 5y ago
  Now i want to try that experiment with a ball. Just nudge it gently and then wait to catch it.
- svantana 5y ago
  > If the astronaut jumps directly to the direction of the orbit normal at any velocity, it will end up in an orbit with equal period That's obviously false for e.g. escape velocity, and by continuity also wrong for lower velocities.
  - exDM69 5y ago
    Yes, this is a small impulse approximation, which assumes that astronaut jump velocity is small compared to orbital velocity. Practical matters (mass) prevents instantaneous impulse to escape velocity in practice.

2OEH8eoCRo0 5y ago

Would you burn on reentry if you managed to deorbit yourself?

baseballdork 5y ago
Almost certainly. You'd be going almost 8km/s in low earth orbit. When your body reenters, it's going to experience the same compression heat as anything else moving several kilometers a second entering the atmosphere.
peeters 5y ago
Well if you managed to deorbit yourself you've already broken all physical laws, so it's difficult to say what would happen after.

dr_traktor 5y ago

> At the right angle and velocity, you might even fall back into Earth’s atmosphere and burn up. That's highly unlikely. Scott Manley has a video [1] examining whether an astronaut could deorbit a small object with human power, and not really. And that's something small, not a massive thing like an astronaut. Fun video though. [1]: https://youtu.be/cxNJoaBLLNM https://youtu.be/cxNJoaBLLNM

gameswithgo 5y ago

I am reminded of my favorite web comic, The Land of Upp: https://www.penny-arcade.com/comic/2006/08/02 https://www.penny-arcade.com/comic/2006/08/02

rlpb 5y ago

"Then NASA’s plan dictates that you take manual control and fly back to safety." I believe that visually flying back would be extremely difficult unless you're already quite close. The further you are away, the more you'll be thwarted in your efforts by orbital mechanics acting in counter-intuitive way. Unless you have a good understanding of orbital mechanics and can apply it to your advantage by using just your eyes. I wonder if NASA has any plans or provides any training around this.

jakemoshenko 5y ago
I imagine that NASA trains its astronauts in orbital mechanics.
- sxp 5y ago
  They did after the first attempt to dock by just winging it failed: https://en.wikipedia.org/wiki/Space_rendezvous#First_attempt_failed https://en.wikipedia.org/wiki/Space_rendezvous#First_attempt...

fitblipper 5y ago

I'm no expert but this part seems to stretch science into hollywood sensationalism: "At the right angle and velocity, you might even fall back into Earth’s atmosphere and burn up." There is a Scott Manley video that describes orbital mechanics well where he covers if someone could throw a ball from orbit back to earth. https://www.youtube.com/watch?v=cxNJoaBLLNM https://www.youtube.com/watch?v=cxNJoaBLLNM It is pretty clear that the best one can do is throw the ball directly backwards which would slightly decrease the orbital height on the opposite side of the earth. I can't imagine someone drifting off a structure faster than someone could hit a golf ball so it seems extremely unlikely that falling back to earth and burning up would be an outcome. I love Kerbal Space Program and find orbital mechanics interestingly counterintuitive so please correct me if I am wrong.

fennecfoxen 5y ago
The thing to remember is in a low earth orbit, your orbit has you moving around 8 kilometers per second. So even before we start getting to the counterintuitive parts (higher is slower, lower is faster, etc) take a moment and think about that 8km/s figure by itself. Consider a token 1% of that amount: 80 m/s (~180 mph). Do you think your orbit has more than a 1% margin before your craft plunges into the atmosphere? (I certainly expect it does). Does this seem like a reasonable speed you could get to using your personal astronaut propulsion device? I don't actually know, but it certainly challenges my image of astronauts zooming around a space station at speeds that would make a kick-scooter look fast.
- jkelleyrtp 5y ago
  Since there's no drag, you can accelerate as much as you want given the fuel in your pack. In fact, propellant is talked about in terms of Detla-V (delta in velocity). It seems like the first models of cosmonaut suits gave about 70 m/s of DV while the most recent astronaut MMUs give about 25m/s [1]. So, I don't think an astronaut could de-orbit themselves with just their suit alone. [1] https://en.wikipedia.org/wiki/Manned_Maneuvering_Unit https://en.wikipedia.org/wiki/Manned_Maneuvering_Unit
  - 5y ago

tzfld 5y ago

What about having a large enough module on a space station, and you simply stuck in the center of it, just floating and cannot push/pull yourself anywhere?

BeeOnRope 5y ago
You could throw something one direction so you float in the other.
- deleted 5y ago
  [deleted]
jakemoshenko 5y ago
This seems impossible to me without a bad actor being involved. How did you get stuck there in the first place? In one scenario you departed from a wall or hand hold somewhere and air resistance slowed you to a stop in the middle. In that case, you should be able to swim through the air given enough time. In the other scenario there is no air in the space station, and as far as I can imagine, the only way to have gotten there with zero velocity would be for someone or something to place you there. Then presumably you could ask that same someone or something for help getting back. There are some nightmare scenarios involving malevolent robots or rooms so large and velocities so slow that you would die before you made it to the other side that are pretty terrifying to consider.
- devenson 5y ago
  You could accidentally throw your last throwable object which zeros out you velocity, leaving you hopelessly stuck.
  - jakemoshenko 5y ago
    Good point, then you are the bad actor!
throwaway0a5e 5y ago

peeters 5y ago

In the context of Gravity this omission kind of makes sense, but the article ignores the ability of your ship to pick you up. The RCS of orbiting ships is extremely precise. As long as they know your relative velocity they'd be able to manuever back to you. > At the moment, there’s no spacecraft to pick you up. The only one with a rescue-ready air-locked compartment—the Space Shuttle—is in retirement. Then how'd you get into space in the first place in this hypothetical?

mschuster91 5y ago
> Then how'd you get into space in the first place in this hypothetical? Outside ISS mission going bonkers - a tank rupturing leading to an unfortunate astronaut getting catapulted off, for example.
- peeters 5y ago
  Yeah I can definitely think of catastrophic scenarios where a ship couldn't help you, it's just the article makes it sound like an impossibility. > However, if the pack’s three pounds of fuel runs out, if another astronaut doesn’t quickly grab you, or if the air lock is irreparably damaged, you’re in big trouble. No protocols can save you now. Perhaps the author meant and there. If SAFER stabilizes you but you don't have enough fuel to get back to the ship, the ship could possibly still get back to you.

villgax 5y ago

I am surprised that there isn't anything like Stark technology, to go out of one of the pods and retrieve you autonomously maybe even the Dragon could be repurposed for such things.

deleted 5y ago

[deleted]

underseacables 5y ago

I thought protocol was that there was nothing you could do. They just keep going

z3ncyberpunk 5y ago

You die. Case closed.