I can only hope that the lethal-injector override exists; but is kept quiet by NASA for PR reasons.
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I expect oneās EMU might restrict oneās flailing motions a bit, so if the jetpack-equivalent craps out for whatever reason, youād be Frank Pooleing your way into the Infinite with no slowing in sight.
But just for us Physics noobs out here, what would happen if you were spinning off into the cold freefall of space and you were afforded full mobility? Never mind the temperature or radiation or explosive decompression, just while spinning away in a vacuum with no obvious propellants at hand, could you slow or otherwise alter your spin through any kind of, well, controlled flailing? Maybe curling into a ball and extending your legs repeatedly, twisting yourself around, doing whatever you could to alter your center of gravityā¦ is it conceivable that that would have any kind of effect? Or would you just be a perpetual motion cosmonaut, doomed to spin along as a corpsicle until some gravitic field finally captures you thousands of millennia hence?
The orbital decay time from the ISS orbit is quite long compared to 7.5 hours and if you need propulsion to do a retro burn, you might as well use it to get back to ISS.
I learned a LOT from that book. Most fiercely didactic bit of fiction Iāve ever read. Even by normal Neal Stephenson standards.
Now thereās a twenty-dollar word if ever I did hear one.
Newtonās first law of motion:
Every object in a state of uniform motion tends to remain in that
state of motion unless an external force is applied to it.
To stop the motion, you would need an external force. Perhaps if one were to collide with a satellite or a meteor, or some source of gravity would pull the corpsicle into orbit.
Well, that makes sense for āa state of uniform motion.ā To me, that implies a relatively static object, like an empty beer can or a lump of cheese. But does the same apply for a self-powered wiggling dingus with a dynamically-moving center of gravity? Does rotational inertia not apply in a vacuum?
A spinning astronaut in space will keep spinning for a long, long time. The spin rate can be controlled to a limited extent by extending or retracting the limbs as a figure skater does, but thatās about it.
NASA did quite a bit of research into this, starting with how cats are able to reorient themselves in zero-G. Because you can extend, retract, and flex the limbs and torso you can certainly change your orientation while conserving momentum. Iām not sure whether anything can be done about killing spin.
Remember that āthe cold of spaceā is mostly a myth. Youāre surrounded by one of the universeās best vacuum bottles; your ability to lose heat is limited to your ability to radiate it and to use it to do things like like decompress the gasses in your life support packā¦ and a resting human produces approximately 100W of heat, independent of any solar heating. (Iām not sure whether the pack and suit, taken as a whole and including the gas bottles, is a net heat source or sink.) Hence STFnal concepts like ālaser refrigerationā, where the idea was to gather the excess heat energy as electrical energy, and turn it into light energy which could be dumped more effectively than if you were just sitting there radiating IR.
Nothing like watching Dark Star with an audience of geeks, who get all the gags where physics is broken or classic SF is referred toā¦
Certainly itās one of my nominees for best extremely-low-budget film ever made.
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as long as you conserve angular momentum you can do whatever you want; unfortunately, thatās not very much, even for a cat, and weāre much less flexible even before the spacesuit. in theory i guess you could try using the jetpack to stabilize yourself, but itās incredibly unlikely that you could actually do it.
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Thanks, guys. I always wonder about crap like this.
The article seems to infer that the jetpack, SAFER, will automagically stop a spin.
From a tech-page on SAFER:
ā¦SAFERās automatic attitude hold feature. This feature arrests uncontrolled rotation of a detached crewmember expected in an accidental separation.
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cool! i was wondering about that.
i was glad to see Dan OāBannon get a writing credit for Prometheusā¦ even if he might not have been. (havenāt seen the directorās cut, i hear itās a lot betterā¦)
Hereās a good description:
Simplified Aid For EVA Rescue (SAFER) - A SAFER Way to Walk in Space - Jet Backpack for Space Walks
I donāt know if itās a standard practice, but astronauts have used the Manned Maneuvering Unit to work untethered. (http://en.wikipedia.org/wiki/Manned_Maneuvering_Unit)
I think an astronaut could possibly slow a spin if the axis ran head to toe. Think of a ballet dancer doing a whatever itās called. Arms out, more mass further from the center of rotation, and you slow down. Bring your arms in and you speed up. Of course, residual drag is going to end up slowing you anyway, but that could be a LONG time in space since thereās so little drag.
If anyone is more up on physics than I am, please feel free to correct me on my inertia blathering. ; )
I donāt know if thereās a specific way to do it, but an astronaut did something along those lines in Marooned. (http://en.wikipedia.org/wiki/Marooned_(film))
Okay, but how would a non-magical creature do it? Unlike cats, we are bound by the laws of physics.
