# RE: Debris mass and impact velocity

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Fri Feb 07 2003 - 23:25:50 EST

• Next message: Don Ledger: "Re: Debris mass and impact velocity"

```Markus posted:

> Relative airspeed between ET and orbiter is in the order of 800-830kph
> at that point (sorry for being metric :).

By ET I assume you mean external tank -- don't you mean the foam
debris and the orbiter?  (The ET and the orbiter are still mated,
of course.)

> In the E-212 footage it appears in eight or nine frames, depending
> on how closely you look. Followed by ~2 frames where it is covered
> by the wing before the impact cloud first shows up.

Ahh, so roughly 10 frame durations or 1/3 of a second (again assuming
30 fps for the camera).  However, I failed to account for the fact
the relative velocity of the debris is increasing from the point of
break off to wing-impact.  Assuming constant acceleration, we have:

80 feet (?) = 1/2 * A * (0.33 seconds)^2
A = 1470 ft/sec^2

V (impact) = A * 0.33 seconds = 490 ft/sec.

Still plenty fast.  If I've underestimated the distance traveled,
the velocity would of course be greater.

--Rob

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