What Happens If an Astronaut Floats Off in Space? (2013)
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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 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.
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.
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.
https://en.wikipedia.org/wiki/Orbital_decay
But from a POV of an astronaut fiddling around with his propulsion unit, this drag is low.
What if you had a really good pitch, do this, and then waited until it comes around the Earth (several months, I guess) hurling back at you, and threw another ball against it? They would collide and fall?
Suppose you're orbiting at 10,000 units per second.
You throw a ball backwards at -20 units per second, giving it a velocity of +9,980 units per second.
Later, you throw another ball at the first ball with the same velocity. Traveling at +9,980 units per second, it will... obviously never be able to hit the first ball. But if the two balls did somehow collide, how could they end up falling to earth as a result?
If your idea is that you sneak up on the first ball from behind (after all, you are going faster) and throw the second ball at it from behind, now you have a ball traveling at v = +10,020 colliding with another ball traveling at v = +9,980. Here at least the collision is possible, but how does falling become a possibility?
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.
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.
That's obviously false for e.g. escape velocity, and by continuity also wrong for lower velocities.
Practical matters (mass) prevents instantaneous impulse to escape velocity in practice.
So if you start off in a perfectly circular orbit, then you need to lower your perigee by the same distance as you raise your apogee, in order to maintain the same orbital period and meet up with what you jumped off.
The angle of impulse is easy in this case. It's perpendicular to the direction of travel. (For a circular starting orbit, and for a small impulse).
> 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?
Outside ISS mission going bonkers - a tank rupturing leading to an unfortunate astronaut getting catapulted off, for example.
> 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.
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.
Newtonian physics will take it from there.
> DAN BARRY | Stranded in the middle of the room
> STS-96
> Entering the space station from the orbiter for the first time in 1999 was an exhilarating experience. Even with just two modules-Unity and Zarya-in place, the station's volume was 10 times that of Discovery's flight deck and mid-deck combined. I floated exactly to the center of Unity, where I could not reach the walls, and got stranded in the middle of the room. It's not easy to get stranded-I had to have my friends help me get perfectly still. Once I was stationary, my brain remained convinced that I could somehow maneuver or kick myself over to the wall. But when I reached out an arm, my body moved back and my center remained in the middle of the room. I instinctively tried moving fast, then slow, then bicycled my legs. None of it helped. I just had to wait for the air currents to drift me to the wall. Sneezing and spitting didn't do much good either. On the other hand, throwing clothing as fast as I could produced enough reaction to send me to the opposite wall.
Never forget your towel.
I wonder if the same effect could be achieved with a single piece of clothing, by repeatedly snapping it in the same fashion that one would playfully snap a towel in a locker room.
https://twitter.com/Rainmaker1973/status/1393598159008505856
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.
[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.]