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Post by wanderer11 on Aug 2, 2005 15:43:29 GMT -4
Further photographic analysis conducted the day after launch revealed that the large foam piece was approximately 21 to 27 inches long and 12 to 18 inches wide, tumbling at a minimum of 18 times per second, and moving at a relative velocity to the Shuttle Stack of 625 to 840 feet per second (416 to 573 miles per hour) at the time of impact. from Columbia Accident Investigation Board Report, page 34
Does anyone know how they came up with this velocity for the foam debris? It has always sort of bugged me. How did the foam accelerate so much in such a short distance when it seems as though it should have actually slowed down? Is the orbiter accelerating 500 mph for every 50 feet at that point?
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Post by frenat on Aug 2, 2005 16:47:50 GMT -4
The shuttle is still accelerating but I would think not by that much. Rather, the foam accelerated in the opposite direction from the relative wind.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Aug 2, 2005 18:44:58 GMT -4
Foam has very little mass in proportion to its surface area, thus the drag force acting on it will accelerate it very rapidly in the opposite direction that the Shuttle is moving. It the same as if you through a piece of foam out your car window while speeding down the highway. The wind catches the foam and it very quickly accelerates away from your car and behind you.
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Post by wanderer11 on Aug 3, 2005 13:21:31 GMT -4
It the same as if you through a piece of foam out your car window while speeding down the highway. The wind catches the foam and it very quickly accelerates away from your car and behind you. I know what you are saying, but the acceleration you are talking about is relative, right? The foam would actually begin slowing down instantly. Without any propulsion, it would have to slow down. But your analogy makes sense considering that the shuttle could be travelling much faster than 500-ish mph figure they used for the test. But it would still have to be a difference in speed of this amount between the orbiter and the foam, wouldn't it? Anyone have any idea what the speed of the shuttle was at that time?
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Post by gwiz on Aug 3, 2005 13:31:58 GMT -4
It the same as if you through a piece of foam out your car window while speeding down the highway. The wind catches the foam and it very quickly accelerates away from your car and behind you. I know what you are saying, but the acceleration you are talking about is relative, right? The foam would actually begin slowing down instantly. Without any propulsion, it would have to slow down. But your analogy makes sense considering that the shuttle could be travelling much faster than 500-ish mph figure they used for the test. But it would still have to be a difference in speed of this amount between the orbiter and the foam, wouldn't it? Anyone have any idea what the speed of the shuttle was at that time? Speed was somewhere around Mach 2 or 3, I think. Yes, it's all relative. Relative to the Shuttle, the foam is rapidly accelerated aft by the air flowing past. Relative to the ground, the foam is rapidly decelerated by the stationary air.
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Post by scooter on Aug 13, 2005 16:12:45 GMT -4
The foam didn't accellerate, it decellerated...very rapidly, due to it's low mass and high drag coefficient. You could say it accellerated in a negative vector, relative the shuttles wing leading edge...same difference. Drop a sheet of paper or some styrofoam out the window of your car at 60mph...same thing. Edit...they were in thinner air, but it was enough to matter...thus the "near miss" that Discovery had at a later point in the climb, at SRB burnout. Dave
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