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"But Mazanek estimated that a chunk of ice the same size would have been more damaging because it weighs 63.4 pounds (28.5 kilomgrams) "the equivalent of a 500-pound (225 kilogram) safe hitting the wing at 365 mph (582 kph)"

The operative equation for kinetic energy is 0.5*M*V^2, where M = mass, and V = Velocity. In this case the velocity term of interest is actually the "relative velocity" of the debris when it struck the wing. Use of this operative equation suggests that Mazenek thought that the relative velocity of the postulated ice chunk would have been about 1025 mph, which is higher that previous estimates that have been discussed (510 mph). One suspects that this much kinetic energy would have caused immediate and extensive damage to the wing itself.

A 63.4 pound block of ice would have had a much greater "ballistic coefficient" than a 2.67 pound block of foam, since the mass is much greater (a factor of 24x), while the drag would be approximately the same. It is very unlikely that a block of ice decelerated to a relative velocity of 510 mph, let alone 1025 mph.

However, an intermediate scenario would be if the debris was a combination of foam + ice. This combination could scale up the kinetic energy proportionally to the total mass, without drastically altering the ballistic coefficient by a factor of 24x. For example, what if the debris what mostly foam with a small ice content? It is conceivable that a 4 pound chuck of water / ice could decelerate to a relative velocity of 400-500 mph, which would still be a devastating amount of kinetic energy.

Doesn't exterior ballistics use the formula mass x velocity -squared- to represent striking energy? I belive you were using only mass times velocity.

I know this from common firearms striking energy tables. (i.e. foot pounds of impact). It's always m x v2.

This would give all impact scenarios much more credence. The tiles are -very- lightweight and even the insulating foam traveling at .7 to 1.5 Mach would have a significant impact.

I was amazed at how lightweight the shuttle tiles are. They are -90%- air.

Fire a marshmellow at 1,000 miles per hour against a stationary marshmellow, you are going to have a sticky mess!

My recollection is that the shuttle was moving at about 1900 miles per hour when the insulations peeled off the external tank. This is about Mach 2.5, well into the supersonic velocities.

For subsonic velocities, the drag force on the foam, which accelerates it back towards the shuttle, would be proportional to the cross sectional area of the foam times the square of the velocity.

However, for supersonic velocities, I think that the drag is much higher, due to the foam having to create the supersonic shock wave and high-pressure area at its bow.

Therefore, given that the foam has little mass, a large cross-section, and is in a supersonic flow, I think that it would be very rapidly accelerated backwards toward the shuttle wing.

Do you know the correct power of velocity for drag in a supersonic flow?