What Happens If An Astronaut Floats Off In Space?
In short: he's in trouble.
By Erik Sofge posted Sep 30th, 2013 at 10:00am
Courtesy Warner Bros. Pictures
Space Scare
Despite the risks, no mission has ever lost a space-walking astronaut.
In the film Gravity, which opens this month, two astronauts are on a spacewalk when an accident hurtles them into the void. So what would actually happen if you went, in NASA's terminology, "overboard"?
NASA requires spacewalking astronauts to use tethers (and sometimes additional anchors). But should those fail, you'd float off according to whatever forces were acting on you when you broke loose. You'd definitely be weightless. You'd possibly be spinning. In space, no kicking and flailing can change your fate. And your fate could be horrible. At the right angle and velocity, you might even fall back into Earth's atmosphere and burn up. That's why NASA has protocols that it drills into astronauts for such situations. You would be wearing your emergency jetpack, called SAFER, which would automatically counter any tumbling to stabilize you. Then NASA's plan dictates that you take manual control and fly back to safety.
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. (In fact, there aren't any.) 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. So your only choice is to orbit, waiting for your roughly 7.5 hours of breathable air to run out. It wouldn't be too terrible. You might get a little hungry, but there's up to a liter of water available via straw in your helmet. You'd simply sip and think of your family as you watched the sun rise and set—approximately five times, depending on your altitude.
As a start:
http://lipn.univ-paris13.fr/~duchamp/Books&more/Penrose/Road_to_Reality-CAPE_JONATHAN_(RAND)(2004).pdf
Page 391:
"Fig. 17.5 (a) Galileo’s (alleged) experiment. Two rocks, one large and one small, are dropped from the top of Leaning Tower of Pisa. Galileo’s insight was that if the eVects of air resistance can be ignored, each would fall at the same rate. (b) Oppositely charged pith balls (of equal small mass), in an electric Weld, directed towards the ground. One charge would ‘fall’ downwards, but the other would rise upwards.
Now the Wrst point to make here is that this is a particular property of the gravitational Weld, and it is not to be expected for any other force acting on bodies. The property of gravity that Galileo’s insight depends upon is the fact that the strength of the gravitational force on a body, exerted by some given gravitational Weld, is proportional to the mass of that body, whereas the resistance to motion (the quantity m appearing in Newton’s second law) is also the mass. It is useful to distinguish these two mass notions and call the Wrst the gravitational mass and the second, the inertial mass. (One might also choose to distinguish the passive from the active gravitational mass. The passive mass is the contribution m in Newton’s inverse square formula GmM/r2, when we consider the gravitational force on the m particle due to the M particle. When we consider the force on the M particle due to the m particle, then the mass m appears in its active role. But Newton’s third law decrees that passive and active masses be equal, so I am not going to distinguish between these two here.6 ) Thus, Galileo’s insight depends upon the equality (or, more correctly, the proportionality) of the gravitational and inertial mass"
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