How fast have you gone?

Well to get reliable results for a shot like this, one cannot use a closed form eqn as density varies too greatly as CJL notes (which is of course why skydivers can rach some extreme speeds if they jump from extreme altitudes.)

Heres a crack at a simulation using the data provided--looks very close to what was estimated (not bad for a first try)



You'll see that it reaches a much higher Vt than predicted based on ground density (which was just shy of M1 at 332m/s) and braking begins at about 40,000' but doesn't have time to substantially slow it--only arrest further acceleration.

As a sidenote the kinetic energy at contact lookes to be the equivalent of 1.5 fully loaded semis (80,000# GVW) at highway speeds.

As an additional note.
Most all that were there heard TWO "booms" about 15 seconds apart.
The first was probably the mach wave, and the second was the impact.

You are correct in your observation of terminal V.
It doesn't apply the same above 60k.

The estamates for impact speed were all the way up to about 1600 mph???

The shock wave entering the ground liquified the 30' dia. area at the point of entry.
It was if someone had set off a large explosion underground, expelling the soil and turning it up side down.

I don't know if the dia. of the hole would give any indications of speed??

There were large pieces of hard ground that were in chunks that couldn't have been cut cleaner with a laser.
It was rather amazing..
Paul

Paul as I recall it didnt Chuck Rogers do the final report of all that info. for those that dont know Chuck Rogers, he was a TRA BOD member as well as the guy in charge of running all simulations for Xprize and the FAA for the Xprize events. He now works for NASA doing that very Job. Im pretty sure his conclusions we very similar to those of your guys Team came up with. I bet he would have some pretty precise answers on the speed of it coming back in.

rrocket said:

The shock wave entering the ground liquified the 30' dia. area at the point of entry.
It was if someone had set off a large explosion underground, expelling the soil and turning it up side down.

There were large pieces of hard ground that were in chunks that couldn't have been cut cleaner with a laser.

Click to expand...

Any pictures?

rrocket said:

As an additional note.
Most all that were there heard TWO "booms" about 15 seconds apart.
The first was probably the mach wave, and the second was the impact.

You are correct in your observation of terminal V.
It doesn't apply the same above 60k.

The estamates for impact speed were all the way up to about 1600 mph???

The shock wave entering the ground liquified the 30' dia. area at the point of entry.
It was if someone had set off a large explosion underground, expelling the soil and turning it up side down.

I don't know if the dia. of the hole would give any indications of speed??

There were large pieces of hard ground that were in chunks that couldn't have been cut cleaner with a laser.
It was rather amazing..
Paul

Click to expand...

Yea, if one looks closely at the data, the acceleration is a constant -32'/s^2 (free fall in space) to about T+220 sec, where a little noise appears, corresponding to about 95,000'. The same thing is apparent on the ascending limb of the altitude vs time curve at about 95k as well. So above 95k is where atmospheric drag effects would seem to essentially negligible for sounding rockets.

A big inflection occurs at about 75,000'==w/o doing the sims, I would guess anything "dropped" from below 75K would have a Vt of that calculated at ground air density. Not sure what instrumentation might have been on board--but a strong argument for tele

And hey I'd love to see some pics as well. When we staged the first Balls golf tourney on the playa last year, that stuff was way hard to punch a 4" hole into....This with forged steel clubs. BTW, the motor used had an ISP of 228--this would then be a definite best case scenario for altitude (subject to the usual datcom limitations inherent to RS, and does not adjust for nozzle efficiency losses).