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Because who needs a space craft?

Picture this:
While performing a routine spacewalk, outside your small, 1-man space pod, a fault in the propulsion system controls causes the pod to explode, launching you into a low orbit of the Earth.

Now with a limited air supply, and only your own space suit & MMU (Manned Manuvering Unit) at your disposal, you are tasked with re-entering Earth's atmosphere, in a survivable manner. (Please note, that chance of survival does not need to be 100%).

The Question:
Is it scientifically possible to survive re-entry in this manner, and if so how? If not, and if it would be possible, if the scenario were to be modified, please describe how it could be modified, in order to make it possible.

Note: Your MMU does not need to be of the modern NASA variety. The story is set in the near future, so the design can be slightly more advanced (but still within reason for an MMU).



Edit: Originally, I had planned for the MMU to provide a wireless transceiver (allowing the astronaut to calculate his re-entry angle based on GPS signals?), a set of manuvering thrusters which set his re-entry vector & slow him down to prevent a crash - if possible, and possibly the material needed to construct a rudimentary heat-shield (if such material would feasibly be used in construction of an MMU).

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  • $\begingroup$ Would you be orbiting the Earth six or seven km / second? If so, no. $\endgroup$
    – Mikey
    Jan 23 '16 at 3:20
  • $\begingroup$ You can be orbiting at any feasible speed. Plus the thrusters on your MMU could be used to alter your speed (to a realistic extent) if necessary. $\endgroup$
    – user17130
    Jan 23 '16 at 3:30
  • $\begingroup$ They might as well say, "You're gonna die Jeff". $\endgroup$ Jan 23 '16 at 3:37
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    $\begingroup$ Check out this: en.wikipedia.org/wiki/MOOSE $\endgroup$
    – AMACB
    Jan 23 '16 at 3:55
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    $\begingroup$ I assumed your MMU to be something like a near-future EVA setup, in which case, absolutely not. Further to this, I would expect your destroyed space pod would have the only chance of things like a parachute? I'm not trying to be contrary, because I think it's a good question (+1), it just seems like a dead end to me. The answers will be good here though. Maybe define what's included with the MMU that's not included with the 1-Man Space Pod? $\endgroup$
    – Mikey
    Jan 23 '16 at 5:42
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There are many problems to overcome:

According to NASA, most meteors of a radius of 80 feet burn up in the atmosphere so that they cause little to no damage. So, we need to somehow cool off our poor guy so that he isn't a pile of ashes by the time he hits (or floats, if he was ashes) to the ground. Add a very potent coolant system or heat shield.

Now that we've solved burning up, we still have to consider landing. Terminal velocity at sea-level for an upright human is about 200 mph. Most meteors burn up around 30 miles, so our friend would have to decelerate in a "mere" 30 miles, either requiring a reverse propulsion system to boost him upward, or a parachute. The former would also require some kind of stabilization system, such as gyroscopes, to avoid flipping over. The problem with a upward thrust is that gravity will push down when you are not at terminal velocity, so you would have to supply a continuous thrust of around 9.9 m/s^2 for about 10 minutes to slow him down to land safely (which is impractical), so you would need a parachute. To be safe, we also include a upward-accelerating jetpack to ensure a safe landing.


All in all, your chances for survival are fairly slim, but it could be possible to survive such a fall.

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  • $\begingroup$ Thank you for such a practical analysis of the problem (+1). Out of curiosity, do you think it would be feasible for our astronaut to re-configure his MMU in order to provide the thrust which you mentioned? $\endgroup$
    – user17130
    Jan 24 '16 at 14:29
  • $\begingroup$ Unlikely if he is floating around in space. Even if he was inside a space station, I doubt he could figure out how to even if it was possible. $\endgroup$
    – AMACB
    Jan 24 '16 at 16:03
  • $\begingroup$ We can dispense with the parachute. He's got quite a range of places to land and presumably good guidance as to the deorbit burn and where to aim. His target should be a place that lacks things sticking up and has just received a huge snowfall. Extremely dangerous but potentially survivable. $\endgroup$ Jan 24 '16 at 17:48
  • $\begingroup$ Pretty good summary of the issues, but you missed the first one: getting into re-entry in the first place. Unless the hapless voyager can alter his orbit enough to re-enter, he will just orbit forever. Not every orbit that intersects the upper atmosphere is a re-entry: if you come in too shallow, the atmospheric shock just bounces you back up! $\endgroup$
    – Securiger
    Nov 14 '18 at 11:37
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    $\begingroup$ (And the delta V needed for this manoeuvre is vastly more than real world EVA kits can provide: for example, the MMU does a maximum of 23.4 m/s. when you need km/s.) $\endgroup$
    – Securiger
    Nov 14 '18 at 11:46
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If this sort of scenario was considered likely, the MMU might incorporate a "ballute".

This is a low mass substitute for a reentry heat shield, and has the added bonus of being an air bag for your final landing. Real life use includes being used to retard bombs (so the bomber can escape the blast) and this has been proposed for real life space missions. The movie 2010 has the Russian spacecraft using a ballet to aerobrake in the orbit of Jupiter, so the technique is versatile.

enter image description here

Now this might not be a common thing to add to an MMU, since while lighter than a heat shield, the mass of the fabric and gas bottles to inflate the Ballute will still be considerable, and make manoeuvring in space slow and unwieldy (you will also require far more fuel for your MMU to work). It would be like suggesting you always carry a parachute and a backpack full of survival gear for both desert and arctic conditions, on the off chance you fall out of an airplane or window.

For your scenario, if the construction shack can't send a rescue pod out quickly enough to pick up the unfortunate astronaut, they might be able to launch a "reentry pack" with prepackaged ballute, inflation gear, extra oxygen, survival kit and a powerful solid fuel rocket motor. It intercepts the astronaut, who rapidly straps it on (or the robotic arms on the device grab him and pull him aboard), then it orients itself, the solid fuel motor fires to begin reentry and the ballet inflates. For simplicity, the device might actually be designed to land on water so the ballute becomes an improvised life raft as well (using it as an airy bag on land might bounce you face first into the desert floor....).

Happy landings

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  • $\begingroup$ While still not quite as epic a solution as I had originally been hoping for, your solution is both realistic and practical (assuming I can find a way for our unfortunate astronaut to acquire one of these ballute systems). I will certainly consider it if I can't find a way to achieve re-entry using the materials that are already in the astronaut's possession (+1). Thank you very much! $\endgroup$
    – user17130
    Jan 24 '16 at 14:25
  • $\begingroup$ No problem. Don't stand too close to windows, though ;-) $\endgroup$
    – Thucydides
    Jan 25 '16 at 1:55
  • $\begingroup$ Solid combustibles to inflate the ballute are a lot lower mass than gas bottles. Not like the sodium azide capsules that (explosively) inflate auto air bags, more like the lithium perchlorate "candles" that have been emergency oxygen generators since the earliest Soviet space stations (ideally producing something that doesn't support combustion, like carbon dioxide and nitrogen). $\endgroup$
    – Zeiss Ikon
    May 4 at 13:28
  • $\begingroup$ The ballute pack might actually be included in the pod (in case something goes wrong) and so the astronaut has to get to the debris and search them to find the pack. $\endgroup$
    – ltmauve
    May 8 at 18:43
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Even if it is possible, it won't happen; since the astronaut was in a space pod, his or her suit probably wasn't designed for re-entry. A space suit strong enough to withstand re-entry would be so bulky and reinforced, it might as well be a small spaceship.

Of course, the odds that this astronaut survived the pod explosion to begin with are, shall we say, astronomical.

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See MOOSE project of General Electric designed in the early 1960s - only 90 kg. I bet that with modern materials we could make it even lighter.

enter image description here

The key to make re-entry easier is to increase surface to mass ratio. If you have good ratio then even paper plane made from silicone treated paper would survive.

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The real concern with this situation isn't related to falling to Earth (gravitational potential energy), but to the problem of kinetic energy.

Anything in low-Earth orbit travels at a high speed:

The mean orbital velocity needed to maintain a stable low Earth orbit is about 7.8 km/s (28,000 km/h; 17,000 mph) — Low Earth orbit - Wikipedia

Using round numbers, an astronaut and environmental equipment might weigh 100kg.
100kg, traveling at high speed has a lot of energy:

E = mv²

m = 100 kg
v = 7.8 km/s

E = 100 kg × (7.8 km/s)²
  = 100 × 60 km² / s²
  = 6 000 000 000 m²s⁻²
  = 6 GJ

So, before you can even think about what happens when falling down, you have to do something with all that kinetic energy before you are even able to fall down.

According to Kyle's Converter, 6 gigajoules is as much energy as in 1.4 tons of TNT.

1.4 tons of TNT produces a serious amount of heat, and you will be at the center of that process.

Forget about re-entry. Imagine you're on solid ground here on Earth, sitting on 1.4 tons of TNT. What are your chances of surviving when that energy is released, even if its release were slowed down enough to not be an explosion?

To say you would be toast would be an incredible understatement.

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Let's see what happens:

First, you have to enter on a very narrow angle. Too deep, you black out, tumble and die. Too shallow, you bounce and you probably run out of life support before you come back down. That's an accuracy you're not going to accomplish by eyeball.

Second, as you enter you need to maintain just the right shape to cause the shockwave to flow around you rather than touch your suit anywhere. You lose orientation, the plasma gets to your suit and you burn.

Third, even if the plasma doesn't touch you it's very, very hot. Most of that energy becomes hot air behind you but you're going to pick up some of it. You're going to need unobtainium insulation on your suit if you want something thin enough that you can actually move about in your suit. Oh, but if your suit is that well insulated how did you keep from cooking yourself while you were in space??

Fourth, the deorbit maneuver requires actual rockets, something that is unlikely to be on a suit for safety reasons. Cold gas thrusters aren't good enough.

There's only one way to survive the trip: Change your species to Kerbal. :) (And even then you need to burn the 600 m/s in your jetpack to shed some of the 2,300 m/s orbital velocity you have.)

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Given you had enough supplies, you could force an intercept to a space station. If you had 60 m/s, and some solar panels to power life support, you might not be screwed. But the force in reentry would almost surely kill you. Even taking the heatshield from your pod, pushing it to a deorbit trajectory, and duct-taping yourself to it after covering the heatsheild with the pods cover to ensure wake stability is better.

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    $\begingroup$ According to the question, this scenario occurs because the worker has become separated from the (exploded) pod, which likely didn't have a heat shield anyway (not designed to reenter or aerobrake). $\endgroup$
    – Zeiss Ikon
    May 4 at 13:31
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    $\begingroup$ Unless your pod was in an orbit that planned to take it to that space station, there is almost certainly not going to be a space station in LEO that you can reach with a survivable relative velocity if you only have 60 m/s of delta-V in the tank. $\endgroup$
    – notovny
    May 4 at 18:45
  • $\begingroup$ aerobraking my fellows, what if it is a comsat mission in a 300 km orbit, aerobraking can get you there. They can detach a soyuz to help you. $\endgroup$
    – user85386
    Jun 12 at 2:23

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