To survive re-entry, a blunt body is a good shape, because it piles up enough air ahead of it in a “stagnantion zone” to keep the real heat of the bow shock away from the vehicle.
Spheres aren’t ideal blunt bodies, but they’re close, and they don’t need orientation controls to keep them pointed the right way. (Indeed, if the sphere spins during descent, that distributes the heat more evenly.)
And since most tanks will be empty, they’ll have a very large surface area for very little mass.
Boundegar: Wouldn’t a sphere be pretty much the exact opposite of aerodynamic?
You’re right, or nearly right as MrHarley’s graphic illustrates. But I think what shaddack was getting at was that a sphere tends to survive because it tends to spin and the heating gets more evenly distributed.
More stable shapes (e.g. oviod, streamlined) heat to melting/failure at the leading surface and continually vaporize, fragment, restabilize, repeat, to complete destruction.
I think the critical factor may be its low mass to surface area ratio, especially when empty. Even if it started carrying 100kg of liquefied gas, this would boil off once the attached plumbing broke up, then you have a surface which can decelerate rapidly while radiating away the heat which may destroy it.
I was discussing the new Star Wars movie with a friend the other day, and the conversation veered over to Spaceballs. Yes, it’s a great movie, but looking back, I think Ice Pirates was actually better. As a kid, I actually taped both of them from HBO free weekends and I watched Ice Pirates like five times as often. I’ve seen neither as an adult. I wonder if I’d still feel the same.
The only thing that confuses me is that 45kg is pretty heavy for part of a spacecraft (that’s about 100lbs for you non metric types).
Bits of rockets fall, well, every launch really. This is why the US launches mainly from Florida because no-one cares if rockets land on Florida I mean because they launch towards the east (to take advantage of the Earth’s rotation) so spent stages fall in the Atlantic. ESA’s launch site in Kourou is similarly positioned. At Baikonur they usually drop the first stages in unpopulated bits of Kazakhstan, although some launches will over fly China, they’ve historically tried to avoid dropping anything there. Partly so as not to annoy them, but also to make sure that no technology is recoverable.
The Chinese don’t care as much though as these pictures show.
Man, those villagers are taking quite a risk just going up so near to a freshly dropped stage. Hydrazine and other rocket fuels are really nasty stuff.
But if you do not know this? (Not all are educated like that )
I think this is a good example of the peeps dropping this debris should a) educate the people/make it possible to educate themselves or b) take care to drop it elsewhere.
Oh for sure. I wouldn’t necessarily expect rural villagers in China to know about the dangers of approaching rocket debris. I was just reacting to so many people just walking right up to this steaming hulk to take a look. I’d be really tempted to do that too, even knowing what I know.
“If I smell anything at all, I’ll just run upwind.”
Always make sure you know which way the wind is blowing before approaching rocket motors. Some of my old cow-orkers discovered that weak hydrochloric acid steam is quite unpleasant to get in your eyes and lungs… it seems to linger in the lungs for a while.
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