Phobos Grunt, get the brolly out again
Discussion
Hoofy said:
Eric Mc said:
By the time the debris is close to the ground (under 40,000 feet or so) most of its velocity will be gone. OK, getting thumped by a lump of metal at 400 mph will still ruin your day - but it won't be travelling at 17,500 mph.
Would this really make a difference? A 1kg lump hitting my house at 400mph or 17,500mph is going to still have me making an insurance claim (act of God? Science proving God exists?), assuming it doesn't pass through me while I sit at my desk.ETA: Eric puts it in a much more dramatic way with the same result.
By the time anything gets to the ground it will have a relatively low forward component of velocity due to the aerodynamic drag acting to slow it down. Whereas the vertical component will be backed up by the force of gravity all the way down. If you look at pics of the Columbia wreckage from back in 2003, even the pretty heavy parts landed pretty much vertically (no impact trails around them).
However, as mentioned, 1 kg dropped from any significant altitude will be traveling at terminal velocity for its mass/drag coefficient at sea level air density, which would deffinately hurt if it hit you ;-)
However, as mentioned, 1 kg dropped from any significant altitude will be traveling at terminal velocity for its mass/drag coefficient at sea level air density, which would deffinately hurt if it hit you ;-)
MiniMan64 said:
Since energy = mass x velocity squared (curse not being able to write proper maths on here!) I would say it would make rather a large difference, yes.
ETA: Eric puts it in a much more dramatic way with the same result.
Well, I just imagined it would pass through faster. I mean being hit by a car travelling at 100mph or a car travelling at 5000mph really wouldn't make a difference to me would it. ETA: Eric puts it in a much more dramatic way with the same result.
Hoofy said:
MiniMan64 said:
Since energy = mass x velocity squared (curse not being able to write proper maths on here!) I would say it would make rather a large difference, yes.
ETA: Eric puts it in a much more dramatic way with the same result.
Well, I just imagined it would pass through faster. I mean being hit by a car travelling at 100mph or a car travelling at 5000mph really wouldn't make a difference to me would it. ETA: Eric puts it in a much more dramatic way with the same result.
PH - Speed Matters (especially if space junk is heading in your direction).
Eric Mc said:
Since the beginning of the space programme in 1957, as far as we know, no human being has even been injured by space junk. However, people have had near misses. Only a few week ago a Russian man had a lucky escape when a piece of space debris crashed through the roof of his house. Luckilly for him, it was "only" travelling at normal terminal velocity of a couple of hundred miles an hour. If it had been travelling at orbital velocity his home (and him) would have been converted to their constituent atoms.
PH - Speed Matters (especially if space junk is heading in your direction).
Yeah, heard about that. Learn something new every day!PH - Speed Matters (especially if space junk is heading in your direction).
Hoofy said:
MiniMan64 said:
Since energy = mass x velocity squared (curse not being able to write proper maths on here!) I would say it would make rather a large difference, yes.
ETA: Eric puts it in a much more dramatic way with the same result.
Well, I just imagined it would pass through faster. I mean being hit by a car travelling at 100mph or a car travelling at 5000mph really wouldn't make a difference to me would it. ETA: Eric puts it in a much more dramatic way with the same result.
Terminal velocity decreases with hight and friction is approximately proportional to the square of the speed. This means that the speed sheds very quickly. Hence the high energy levels and ablation seen in the upper atmosphere. Only high density objects made of substances resistant to heat will tend to survive. Large flat panels and empty tanks will move very slowly indeed in comparison to a lump of iron chondrite in a meteorite.
MiniMan64 said:
It's all about energy delivered though, 5 times the speed does not equal 5 times the energy, it's 25 times the energy.
What I mean is that if an object hits me very quickly or so quickly you need a calculator to work out the kinetic energy, it really doesn't matter. I'm going to be killed.
Eric Mc said:
Hoofy said:
I can't help thinking that is such an expensive piece of kit for such a s
t video. It would have been better if he had not bothered filming it.
The object is over 100 miles above his head, is smaller than a van and travelling at 17,5000 mph. Could you do any better?t video. It would have been better if he had not bothered filming it.I am actually impressed with the images these chaps can capture.
This site does but I am not sure what it is basing its simulation on (how accurate) and how valid the sites is. Heavens above above lists it but I suppose its a decaying orbit and that affects the tracking. My starry night also lists it but again, not live tracking, predicted.
http://www.n2yo.com/?s=37872
http://www.n2yo.com/?s=37872
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