Re: Debris mass and impact velocity

From: Don Ledger (
Date: Fri Feb 07 2003 - 23:46:10 EST

  • Next message: Dave Radomski - KT0H: "Columbia - Urban Legend"

    Hi Robert,
    Don't forget, I was using a Boeing 747 for comparison here and 
    way down the scale from the Mach 18.2 Columbia was doing. Marcus 
    asked me as well about the weight of the ET insulation. I'm 
    attempting to find my source on that weight.
    I once saw a demo [16 mm] of a 12 pound turkey [thawed] fired 
    out of a compressed air cannon and into the wing root of a DC-9 
    at only two hundred miles per hour. It penetrated the "D" 
    section of the leading edge and went through the spar like an 
    ice pick through hard cheese. Sobered me up. The D section is 
    important to the fore/aft strength of the main spar [ i.e. 
    pre-mach compression waves] which of course is meant to handle 
    lift and bear the weight of the shuttle. The delta wing handles 
    the stresses a bit differently than the a straight wing but 
    handles the higher mach numbers, boundary layer transistions and 
    heat much more efficiently.
    I'll try and find that source.
    Don Ledger
    Matson, Robert wrote:
    > Hi Don,
    >>I believe however that NASA has set a weight of about 3 
    >>kilograms- or about 7 pounds-for the weight of the piece that
    >>flaked off the ET.
    > I thought it was 2.7 lbs?
    >>If that same piece hit the leading edge of the wing of a B-747 
    >>at the wing root at Mach .89, well it's a good chance the
    >>stressed leading edge would lose it's effectiveness ...
    > Is Mach .89 the velocity that they came up with for the impact?
    > Seems high, but maybe it's right.  The velocity can be estimated
    > by taking the distance from the flake-off point to the left wing
    > leading edge and dividing it by the time it took to get from one
    > to the other.  I don't know what the frame resolution of the
    > tracking video was -- perhaps the standard 30 fps?  In how
    > many frames does the debris appear?  I remember it being
    > something like 3 or 4.  So we're talking about a distance
    > in the ballpark of 80 feet (?) being covered in 3 frame
    > durations (0.1 seconds?):  800 feet-per-second.  ~550 mph.
    > So not exactly a trivial impact... --Rob
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