Jose wrote:
Yes, and it is also why the shedding foam can only do serious damage
within the lower atmosphere, as the drag cannot decelerate the chunks
enough to strike with enough force to do harm at that altitude.

Uh... even with no atmosphere, the rocket is accelerating wrt the
detached foam. I'm not convinced this is insignificant.

Jose

You could figure this out; if there is no air around when the foam sheds
then its velocity in relation to the Shuttle is based on the distance it
covers and how many Gs the Shuttle is accelerating at.
From the bipod ramp to the place where it hit Columbia was about fifty
feet.
Say the Shuttle was accelerating at 3 G's. At one G acceleration is 32
ft. sec/per sec, so at 3 G's it's three times that, or around 100 ft.
per second, so the foam takes around around 1/2 second to reach the wing
after release (actually a little more than 1/2 second, as it's picking
up more velocity in relation to the shuttle in the last 1/2 second than
the first 1/2 second, so let's call it .7 seconds) So, it travels 50
feet in .7 seconds, or around 80 feet per second at impact. That works
out to around 55 mph at impact for that hypothetical case. IIRC, the
piece that hit Columbia was doing around 400 mph, so velocity is around
1/8 of that that damaged Columbia's wing. Every time you double the
velocity of a impactor, you quadruple its energy, so something going 55
mph isn't going to pose much of a threat at all, as if I'm doing my math
right it only has around 1.6% of the energy of the Columbia impact.

Pat