I played with the flight info for laughs and giggles as well. I use RASAero 2 to obtain the CD versus velocity for the rocket shape. I didn't bother to run a flight sim as there is not enough information on the weight of the rocket or the thrust curve of the motor, and as there appears to have been a motor failure during the flight, the sim wouldn't be that useful to determine the ground impact velocity, so I made a generic spreadsheet to calculate the terminal velocity of any rocket at any altitude if you know the CD, the mass, the diameter, and the atmospheric density.
View attachment e3m.xlsx
RASAero predicts a Cd of 0.442 (which I thought was low) for a rocket with an OD = 4.5", a 5:1 TA NC, and 3 swept fins with 30 sq in area each with a hexagonal foiling as shown in the photos in the thread. The 6' long x 4.5" diameter x 0.25" nominal wall weighs just under 24 pounds, I bestimated the fins 2 0.5 pounds and the NC @ 1 pound. Considering what else goes in the rocket, I bestimated a burnout weight of 32 pounds, and with a 16 sq.in. cross-section obtain a 2 pound/sq.in. sectional density. Having spent some time at White Sands doing laser shoot down missile testing and commuting from Las Cruces daily, I bestimated the launch site altitude to be ~5000' msl and used the aerospaceweb.org atmospheric calculator to obtain the atmospheric parameters for my spreadsheet, and by looking at clothing worn by Manny and company in the launch video, bestimated the launch temperature was between 40F to 60F. The standard atmosphere temperature for 5000' msl is 41F so I did not bother with an offset however raising the temperature would also increase the sound speed so I didn't.
For the rocket I bestimated, the ground impact velocity was approximately 810' fps or Mach 0.73, not even transonic. Playing with the spreadsheet, you would need a rocket weight of 60 pounds (sectional density of 3.75 psi) to impact the ground at Mach 1. The bestimated rocket drops thru Mach 1 ~24 kft MSL which is ~19 kft AGL. As the speed of sound is ~1100 fps, the closest sonic boom signature would arrive on the closest point on the ground ~19/1.1=17.3 seconds after the rocket became sonic the location would be near the point of impact. If the launch crew was 3 miles away from the point of impact the slant distance from the supersonic rocket would be the sqrt(19^2+15.8^2)=24.7 kft on the slant with a (24.7/1.1)=22.5 second acoustic delay.
The transit time of the rocket from the sonic point to ground impact is ~16.5 seconds. From the descriptions in this post, and the fact that the rocket was not found, I have to conclude the rocket impacted at a rather distant location from the launcher. For an average male adult standing on a flat surface, the horizon distance is ~3 miles or ~15.8/1.1= 14.4 seconds away acoustically. If the point of impact was visible but distant from the launch crew, a boom heard near the time of impact could not be due to the impacting rocket, but rather the sonic signature of the rocket at altitude.
Play around with the spreadsheet if you don't believe the physics.
Bob
