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First Photos of the Reentry of the ATV "Jules Verne"
White Yeti writes with news of the reentry breakup of the ESA's Automated Transfer Vehicle. All went as planned, and the ESA blog has preliminary photos. An international team of observers, in two aircraft south of Tahiti, saw a series of explosions and over a hundred small pieces of debris. Observations were mostly made using optical cameras and spectrographs. The two images on the ESA site are low-res samples, so we should get more spectacular images soon.
I guess the summary could have been clearer about this being an intentional breakup during re-entry. The craft is designed to be destroyed after use.
It depends on the design/shape of the object. But generally a bit above mach 1. A blunt reentry object will cause a very strong shock wave at the front of the craft and will cause much more heating than a sharp object. Once you hit about Mach 5 IIRC the heating issue is getting quite serious. Reentry is about >7000m/s (speed of sound at that height does not really make sense) and causes extreme heating no matter what the design. For comparison Mach 1 is about 350 m/s at sea level.
If information wants to be free, why does my internet connection cost so much?
The Jules Verne was carrying nothing but rubbish; it was intentionally burned up on re-entry. It's just a supply ship: it carries stuff up to the Station, serves as a little extra habitable volume while docked (I hear some of the crew have found it a very quiet place and have pressed it into service as sleeping quarters), and finally carries away waste and junk and incinerates the lot in the atmosphere.
With the uncertainty over the future of the American manned capability, there is now talk of developing an upgraded ATV which would include a re-entry module, and make ATV into a complete manned spaceflight system. Mind you, there's always talk; ESA headquarters is full of extremely expensive paperwork relating to manned spacecraft that never flew. At least in this case there's something concrete to point at, though.
Real Daleks don't climb stairs - they level the building.
Logical and correct, although supersonic heating has nothing to do with friction.
Something moving through air pushes that air out of the way. At subsonic speeds (i.e. below the maximum speed the air as a fluid can move) this carries heat away from the aircraft. At supersonic speeds, the air simply cannot get out of the way quick enough, so piles up against the fuselage. This compression (not friction) creates heat.
If we can put a man on the moon, why can't we shoot people for Apollo-related non-sequiturs?
For what? Its primary mission is to deliver supplies from Earth. Oxygen, water, food, fuel. While docked it acts pretty much as a walk-in wardrobe. Once its supplies are exhausted there's no further use for it; they load it up with rubbish and send it off to burn up. Then another one gets launched.
It would probably be possible to redesign the ATV with a heatshield to allow it to come home intact. But that adds a lot of weight and drastically reduces its capacity as a cargo carrier; you'd only do that if you wanted to use it to carry human crews. Maybe that'll be done some day, but not right now.
The only other use for the ATV while in orbit is for station-keeping. It can boost the Station's orbit, and some day an ATV may be given the mission of de-orbiting the entire structure. But there's no sense sending up more fuel to allow the ATV to continue working as a tugboat - that fuel would be delivered by, er, another ATV. So you might as well let that do the job.
If there were other stations in near-Earth space, then keeping a spare ATV in orbit might make sense. It could ship equipment and perhaps crews between them. But right now there's nowhere to go from the Station except for back to Earth.
Real Daleks don't climb stairs - they level the building.
Here is a simple way to think about it -
The kinetic energy of your (or an airplane's) motion gets converted into friction through turbulence and shock effects. Heat is just the velocity of atoms bouncing off each other, and the sound speed depends on the velocity of those atoms, and thus on the temperature.
In an ideal gas, the absolute temperature is a measure of the energy, and thus is a constant times the square of the rms gas velocity. By the same consideration, for an idea gas, the speed of sound is (a constant) times the rms particle velocity. (That constant is the square root of the (adiabatic index /3), or about 0.7 for a monatomic gas.)
So, you are correct. Speeds much slower than the speed of sound will generally be associated with small amounts of heating, which may be negligible compared to other effects, such as cooling caused by the air flow, while speeds much higher than the sound speed will generally involve heating to something much above the ambient temperature. (Generally, of course, airplanes are designed not to convert all of their kinetic energy into turbulence, but during re-entry, that is done pretty effectively.)
The real gases in air are very non-ideal in the temperatures and pressures in re-entry so this simple theory is not realistic for speeds much above Mach 3 or so. It turns out that an engineer's rule of thumb is that the temperature in K is roughly equal to the speed in meters / sec, based on more realistic models of specific heat in the ionized plasma formed at these high speeds.