Shuttle Foam Test Yields Hole in Wing (Produces vs Yields)

AP ^ | 07/07/2003 | MARCIA DUNN, AP Aerospace Writer

[El Gato]

That's gotta have alot of volume of air/nitrogen or whatever they're using to be able to launch a non-tube conforming 'round'

They use a sabot to seal the "payload" from the propellent gas, and have a "stripper" that stops the sabot, but not the payload, be it chicken or foam. Although in the case of the foam, I think, but am not certain, that they put on a new tube that was the shape they wanted. Pictures show it basically square in cross section. I don't know how they "valve" the compressed gas into the barrel behind the sabot, possibly by puncturing a diaphram, as I've read that's the way some similar "guns" do it.

[fnord]

So the foam travelled a relative distance of 53.4 feet in .252 seconds, right?

Initial velocity of 682.5 m/s
Initial acceleration of 12.1 m/s2

Is this what you started with in your calculations?

[Resolute]

No, those were the approximate initial conditions for launcher & orbiter (cojoined) at the approximate time of foam separation. I derived the initial conditions by applying curve fit to the data presented here:

Observation on TPS damage on Orbiter (Post 2431)

The initial acceleration (actually deceleration) of the foam is 1329.0 m/s2, applied in the opposite direction to the boosting acceleration of the launcher and orbiter. The deceleration due to drag decreases rapidly as the foam slows down: Drag is proportional to the airspeed squared, assuming a constant drag coefficient (in this case 0.65).

[Resolute]

You didn't ask for this, but here is the Fortran source code that I used to estimate the foam separation "dynamics" with respect the axial direction (no lateral or rotational dynamics):

program test

data dx0 / 0.0 / ! m
data rho / 0.08823 / ! kg/m^3
data press / 7345.4 / ! N/m2
data xmass / 1.211 / ! kg
data sref / 0.120492 / ! m^2
data g / 9.80665 / ! m/s^2
data v0 / 682.5 / ! m/s
data deltat / 0.00001 / ! s
data tfinal / 0.5 / ! s
data dtout / 0.030 / ! s
data dteps / 0.000001 / ! s
data cd / 0.65 / ! non-dimensional

vmag = v0
dx = dx0

nsteps = nint ( tfinal / deltat )

do i = 0 , nsteps

time = deltat*float ( i )

! compute drag force

Q = 0.5*rho*vmag**2
drag = cd*Q*sref

! integrate relative deceleration, including drag +
! gravity + powered boost

acc_new = - drag/xmass - g - 12.14
if ( i.ne.0 ) then
vmag = vmag + 0.5*deltat*( acc_new + acc_old )
end if

! integrate relative velocity

vrel = v0 - vmag
if ( i.ne.0 ) then
dx = dx + 0.5*deltat*( vrel + vrel_old )
end if

! save old states for trapezoidal integration

acc_old = acc_new
vrel_old = vrel_new

! check cumulative displacement, exit when threshold is met

if ( dx/0.3048.ge.53.37 ) then
write(*,1) time,vrel/0.447028,dx/0.3048,Cd
write(8,1) time,vrel/0.447028,dx/0.3048,Cd
exit
end if

! output the relative velocity and translation at scheduled intervals

test = time - dtout*anint ( time/dtout )
if ( abs(test).le.dteps ) then
write(*,1) time,vrel/0.447028,dx/0.3048
write(8,1) time,vrel/0.447028,dx/0.3048
1 format(f9.6,3f9.2)
end if

end do

pause 'end of sim'

end

[Darksheare]

Coolbeans.
Being a former artillery soldier, I'm used to the 'old fashioned' way of sending something on it's way.

Thanks for the info.