I flew Postitve Ascent for its 18th flight on Saturday, 9/28/13. I wasn't planning on doing any more launches this year but the motor was built and the weather was too good to pass up.
The motor was the Cesaroni 5 grain Pro75 M1300 Imax/ Dual thrust. The motor provides 6438 Newton-seconds of total impulse. The motor consists of 4 Imax grains sitting on top of a Vmax grain. Vmax is an aggressive, high speed propellant, while the Imax is a medium speed, efficient (more total impulse, that's where the Imax name comes from) propellant. This is how the boost-sustain (dual thrust) thrust curve is created. All 5 grains burn normally but the Vmax basically gives a kick until it burns out at about 1 second, leaving the Imax grains to continue burning for another 4.5 seconds or so. This is clearly illustrated by the thrust curve:
M1300 Thrust Curve
The conditions at the time of the launch were not perfect, but pretty close. The sky was perfectly clear but there was a breeze from the southeast at 5 to 10 mph with stronger gusts to 15+ mph. This was a a little unsettling as I was expecting a 10,000 foot flight and two other flyers had already landed well outside of the field. I put a fairly heavy angle on the pad to the southeast and went for it.
The launch was perfect in every way. The rocket took off aggressively on the Vmax kick and the flame clearly shrunk as the Vmax grain burned out. The Imax grains seemed to burn forever. The clear skies were really nice; I had never been able to visually follow the rocket all the way up that high before. I only lost site once during the drogue portion of the descent. When I saw it again, it was about 4000 feet up still and clearly coming in on a perfect trajectory to land safely in the field. The main charge fired at 900 feet and the recovery harnessing slowly pulled taut as the main opened gracefully. The rocket only landed about 1000 feet away.
A pad video can be found here:
Pad Video
The altitudes reported by the SL100 and Co-Pilot V2.0 read out 10,501 feet, and 10,409 feet, respectively, for an average of 10,455 feet. The SL100 also reported 686 mph top speed.
Overall, it was an absolutely perfect launch, and I am happy to be able to end the season that way.
