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On the Matter of Space Junk
SpaceAdmiral writes "Nature reports that space is in need of cleaning. From the article: 'Space could soon become too risky to visit unless derelict satellites and rockets are removed from orbit. That's the stark warning from a new simulation of space junk drifting around the Earth, and scientists are calling for swift international action to solve the problem.'" According to another astronaut there is at least one more piece of space trash they haven't accounted for. Philip K Dickhead writes "Veteran astronaut Mike Mullane claimed that the NASA Space Shuttle is 'the most dangerous manned spacecraft ever flown [...] It has no powered-flight escape system." He also accused US space officials of suppressing safety concerns raised by crew-members of shuttle flights."
Big number fallacy; a nuke is big, sure, but let's be amazingly optimistic and assume it can completely physically clear a 10-mile radius of space junk, while not adding anything itself.
The average radius of the Earth is 3,959 miles, call it 4000. The definition of LEO orbit is from 400 to 1600 miles above the Earth. Sphere volume (close enough) is defined as (4/3)*pi*r^3.
To cover LEO, we need to cover a volume of (4.0/3)*pi*((4000+1600)**3 - (4000+400)**3) miles, which is 378,000,000,000 cubic miles (378 American billion). Our incredible optimistic nuke can "clean" (4.0/3)*pi*(10 **3) cubic miles, or 4,200 cubic miles. Dividing the (unrounded) numbers reveals that we need to set off 90,449,062 (~90 million) miracle nukes to clean the orbit.
(If you start python and type as your first line "from math import pi", those expressions will slide right into Python so you can verify them. Insignificant figures have been trimmed for presentation.)
And it's even harder than that, since the objects are moving at different speeds, and it's quite easy for objects to slip between the cracks if we don't light up the entire orbit at once.
Clearly, this is absurd, because we don't even have that many pieces of space trash in orbit, by many orders of magnitude. Because of the difference, we don't even need to do any sort of statistics to safely conclude that there are no "concentrations" of space trash that could be nuked, and we are in fact going to have to address the situation one piece of trash at a time.
> Surely you cant eject gracefully from that little
> Russian capsule either, or can you?
The capsule itself isn't dangerous, so there's no need to eject from it. The danger is the rocket it's attached to. That's why Mercury, Apollo, Soyuz and Shenzhou all have what's called an "escape tower". That's a big solid rocket attached to the top of the capsule which will fire if the main rocket starts to blow up. The escape tower will haul the capsule away from the exploding rocket, then the parachutes open and the capsule lands. The Russians have had at least two incidents where their crews were saved by this system.
Gemini capsules were on a rocket filled with a fuel that burned slow enough that any explosion would be much less violent, so they had ejection seats instead of an escape tower.
Shuttle has no options. When it goes boom, everyone dies.
The Challenger crew compartment was essentially still one piece when it hit the ocean. Considering that part crew escape mechanism design involves engineering decisions like NOT putting the crew vehicle next to the "bomb" , like the space shuttle, but rather putting it on top, like [soyuz|apollo|other traditional] spacecraft; well, yeah, then there's plenty of time for a solid fuel rocket to separate them from the fireball.
Certainly you cant eject during reentry, if your ship is burning up, isnt that jumping out of the frying pan and into the fire?!?
The space shuttle is a flimsy design, 30 years out of date. "Standard" spacecraft design is pretty darn reliable-- they basically don't burn up on reentry because they're not built out of ceramic foam blocks glued onto superlight carbon fiber frames, they have predictable non-flimly ablative heat shields. The only time you'd ever need to "bail out" with a standard design would be if the parachute failed, after actual reentry, and that is (in theory) possible.
So basically the two space shuttle accidents have shown that it is a highly vulnerable system. A fuel tank explosion on launch of (say) one of the Apollo/Saturn V launches would result in the crew module separating and being pulled away by the solid fuel rockets of the escape tower for a safe parachute landing. Damage to the reentry vehicle from an insulating foam chunk off the launch vehicle would be impossible, given that A) the former is above the latter, B) it's not built like french racing bicycle out of delicate materials, but more like a solid military aircraft.
If a job's not worth doing, it's not worth doing right.
They use solid-fueld braking rockets for last-second deceleration of a parachute landing. Rocket failure might result in some pretty nasty bumps and bruises, but that's all. It's a highly reliable system. The soviets even used it for para-dropping armored vehicles with the crew strapped inside. NASA opted for "splashdown" and naval recovery for simplicity's sake.
If a job's not worth doing, it's not worth doing right.
Your professor almost certainly was talking about a series of US "high altitude" (i.e., space) nuclear weapons tests performed in 1958 and in 1962. This was at the very beginning of the "space age", so while the radiation effects on the few satellites in orbit were very significant (or fatal in some cases) there weren't many of them up there to be destroyed.
You can find good writeups in any good history of US nuclear testing. The Wikipedia article on "Nuclear testing" is as good a place to start as any. Look for "Rocket-propelled warheads".
This sort of thing was banned by the Limited Test Ban Treaty, signed by the US and USSR in 1963.
As opposed to the ones that have a powered ejection seat...
As opposed to the ones that have any form of escapesystem at all. The Gemini and the Vostok used ejection seats (the use of which was the normal mode of ladning in the case of the Vostok - the cosmonaut did not ride his capsule all the way down). The majority of manned spacecrafts (Mercury, all the various versions of the Soyuz, Apollo, Shenzhou and the planned CEV) fetures escape towers - a rocket that will pull the part of the spacecraft with people inside away from any accidents (and hopefully high enought up for parachutes to work). As far as I can tell, the Shuttle shares the dubious distinction to be one of two (the other was Voskhod, which was basicly a juryrigged Vostok) to have flown in space with no escapesystem at all.
Back in the 'good, old days', a lot of thought went into weird and wonderfull ways to bail out from orbit, but these days it seems like there is little will to admidt that things can go horrible wrong up there...
Everything in the world is controlled by a small, evil group to which, unfortunately, no one you know belongs.
Quark (1977) or Quark (1978) was a great show where Adam Quark, captain of a United Galactic Sanitation Patrol ship, and crew collected giant space baggies of trash.
What was old is new and in humour there is truth.