It was a decent day, a little windy but with the radio tracking equipment I wasn't too worried about the wind. John and I were on the video cameras with Joel on the launch controller. Once the rocket was on the tower the altimeter was turned on and the igniter wired up. At the controller we did did a quick continuity check, no continuity. So I checked out the wires, all seemed good so I replaced the igniter. It was the first bad ignitier I've had in three years, and I've used hundreds. New igniter, good continuity. All is ready.
Last check all clear. I warned the observers one last time this was going to be a really fast liftoff. 5,4,3,2,1 and ignition!
Click Here for a short video of both camera shots combined. 2.09MB, 22 seconds.
As expected, the little rocket shot out of the rail like a bullet.
It didn't take long and the rocket was out of sight.
I think the fast take off surprised everyone but me, I had warned them... There was a loud pop at the end of the motor burn, I'm not sure if was a sonic boom or the pop of the motor at burn out. My AP based motors seem to burn out so quickly there is a pop at the end of the burn. I guess it doesn't matter, as the rocket continued on its merry way, unobserved by any of us. The rocket isn't painted so the body is almost translucent, and being so small, moving so fast, all I could do was grab my direction finding receiver and track the rocket through the sky. After about a minute, it was pretty clear the rocket was safely under the parachute. I continued tracking the rockets descent until I lost the signal.
We all piled into Joel's car for the search, after a few minutes on the road I picked up a strong signal. I got out and walked into a freshly cut hay field, about 500' in...
I found the rocket, intact and laid out nicely. Beeping out an altitude of 7,426'.
Now I was anxious to get the data from the ARB3D. After loading up my van, John and I headed back to my place to download the data.
Here's a screen capture of the downloaded data.
This flight profile fell very close to exactly what my software had predicted. I real nice test for the ARB3D as the rocket did indeed break mach at 837 mph. 39.55 g's is real load, and a good test for the airframe. The burn time was about .5 second faster than expected, but well within the motors limits. Speaking of the motor, I was pleased to find the Isp calculated to 196 seconds. Very good in a small motor. The ER1.75I also had no problems with the almost 5,000 degree combustion temperature either, as the motor came out in great condition.
So the ARB3D has performed well in a fairly demanding flight. Now I've got a little more confidence flying these electronics in a larger rocket again. Although it still doesn't explain the early deployment on the A2MD maiden flight.