Re: Nasa kinetics lesson

[Brian Whatcott <betwys@SBCGLOBAL.NET>]

At 11:31 PM 6/5/2003 -0700, Tucker Hiatt, you wrote:

> >http://www.nytimes.com/2003/06/05/national/nationalspecial/05SHUT.html
>
> Can we understand how NASA came up with an impact speed of about 530
> mph for the falling foam?  Didn't the foam fall from a co-moving
> section of the shuttle?  Even allowing for the shuttle's continued
> upward acceleration during the foam's brief downward fall (aggravated
> by a downward drag force), doesn't 530 mph seem a tad speedy?
>
> - Tucker
> --
> ***********************************
> Tucker Hiatt
> Physics Instructor & Wonderfest Director
> The Branson School


One might argue in this way: it is known that insulation can fall from the
structure, because it is seen falling from the launch point onwards.
 Reviewing the speed profile of the vehicle, what is a plausible maximum
product of drag force (tending to dislodge structure) and kinetic energy
due to relative acceleration of the particle in the local airflow?
0.5 rho v^2 A Cd X 0.5 m v^2  ?
rho is a function of altitude, and for constant acceleration force,  one might
 model it as an inverse function  of speed squared.  One would need to
estimate the speed at which rho essentially falls  to zero.
It would be pleasant to suppose that Mach 1 is exceeded where rho is low,
indeed where Mach loses meaning.
Still, even with this trivial level of analysis (speculation, really) one sees
a plausible bias to high vehicle speeds in the stratosphere as being
a dangerous interlude.
Argued in this way, one might counter argue that 530 MPH is by no means
the most plausible impact speed, which might be higher....

Brian Whatcott     Altus OK