Flight 1a Report - 5/01/04 - Plaster City, California.

Crash Test Dummy finally flew on May 1st at the Tripoli San Diego's launch!

The rocket flew on 5 motors. A central 54mm K660 and four airstarted outboards. The outboards were two G79's and two H143's started 2 seconds into the flight. A PerfectFlite miniTimer3 was used with a break wire to start the outboards. Our goal was to satisfy the first two mission objectives.

RockSim 7 indicated that it should fly to 5474 feet. Crash Test Dummy weighed 24 pounds before the motors, 30.5 pounds completely flight ready. Recovery is on two SkyAngle 60" chutes and the 60' of RocketRage Cobra Head harnesses.

Photos of the flight: (click on a picture for a hi-res image)

Now for the bad news.

The up part worked perfectly but the recovery was sub-optimal. Although the simulation indicated a flight to over 5000 feet, the drogue chute deployed well below that point.

It appeared to us viewing on the ground that deployment occurred some time after motor burnout but well short of true apogee. Given that we used four nylon shear pins, drag separation appeared unlikely as the culprit. We used two redundant altimeters, a Missile Works RCC 2 and a PerfectFlite miniAlt/WD. Fortunately, the PerfectFlite is a recording altimeter and should be able to supply a clue to the answer.

Considering the speed at which the rocket was travelling when the drogue was delployed, the damage was minimal - just a small, 1" zipper on the drogue body tube.

The Verdict

The Missile Works altimeter was beeping an altitude of 2637 feet when we recovered the rocket and the PerfectFlite recorded it's interpretation of the flight. The graphs are below, the first of the full flight and the second of just the first 15 seconds.

Click on the graphs for a hi-res image

Given that motor burnout occurred at 4.1 seconds into the flight but the first deployment event occurred at about 6.5 seconds in, drag separation appears unlikely to be the cause of the early deployment.

The graph clearly indicates that an event occurred prior to the PerfectFlite detecting apogee at 3154 feet. The altitude indicated by the Missile Works seems to correspond to this event. Therefore, it appears that the Missile Works altimeter detected apogee early and deployed the drogue chute.

The only thing left to determine is what caused the Missile Works to fire prematurely. It is a well used altimeter, having flown at least 10 times without a hitch. The only thing I can think of is that the static ports were improperly drilled. They are a little small and are somewhat ragged on the inside edge. This is something the manual warns of but I do not have any personal experience. The sensor on the altimeter is very close to one of the static ports - this may be a problem as well. If anyone has any suggestions, please send us a note.

For the next flight, we will clean up the static ports and fly without an apogee charge attached to the altimeter in question. It will still sense apogee and report the altitude, so we should be able to get an indication of its health.

Acknowledgments

Peter and I would like to thank everyone involved with helping us get this project in the air.

Among the many family and friends, we would like to say a special thank you to Andy McPherron, Alan Watkins and Jorge Velazquez, our official team photographer.

Photos of this launch were taken by Jorge Velazquez, Jim Julig and Elsa Mickelsen.