After test flying the Lust For Thrust on an Aerotech J570 on Saturday it was time to get the rocket up first thing Sunday morning. I was able to squeeze in 385 grams of N2O into the flight tank after chilling it overnight in the cooler and prefiling it with 50 grams of nitrous and venting it to make it even colder.
The fill line made from the paintball tank adapter and the Holley nitrous line worked as designed. The hydraulic connector did not leak and held the pressure. This design was the safest I could come up with to prevent the inadvertent launching of the tank while disconnecting from the fill line. You do not have to reprofile the threads on the tank adapter to accept the remote connector/ hydraulic coupler which was discussed in the previous post.
The rocket flew quite well on a J570 the previous day. I wanted to use a commercial motor that was close to the same length as the RMS hybrid as possible to make sure the weight and balance would be within safety margins. The flight went up to 5485 feet.
Lust For Thrust flying on an Aerotech J570
Since Sunday was the last day of Balls, I had to prep on Saturday with the exception of filling the flight tank. I was able to get it off on the 2nd rack of the day. Tahoma Photography captured the launch got a much better shot than I did. My picture consisted of the fin can in the upper portion of the frame.
The exhaust plume is very light in color, those in the know have told me that means I was very close on the N2O/Fuel ratio. This flight went up to 2965 feet. I will still need to pull the data from the altimeter, unfortunately the recovery charge went off but the main did not deploy, this resulted in a hard landing destroying the avionics package. I was hopeful that he memory card in the GPS was good, but as luck would have it, I did not format it, so no data from that piece.
After driving 1740 miles in two days I was able to devote time to doing a post launch analysis of the motor. The pyrovalve, a 1/4 inch section of an Estes C-6 motor, burned almost completely.
There was no soot on the topside of the injector plate.
The O-ring on the paintball tank adapter was compressed. Consider this a single use item, they are cheap and can be gotten in quantities of 100 from Amazon.
The propellant grain weighed 535g, weight after launch was 320g. The liner was in great shape with no burn through and could probably be used again.
The nozzle showed very little erosion, unfortunately a piece of the flange broke off during handling so it cannot be used again. I have seen recent posting about allowing a steel nozzle on sugar motors. I will have to reach out to Tripoli research to see if this qualifies for it. Some of the grain adhered to the nozzle, but it did come off after a little persuasion. Soaking it in water should dissolve any left over residue.
Overall performance was better than expected, the landing was a bit hard. After repairs I plan on using the Rocketman ultralight parachutes to make it easier for them to deploy and also remove one of the Eggtimer Quantums to increase the space in the avionics bay and allow larger capacity batteries for the GPS and telemetry. Lust For Thrust will be repaired and back in the air for the next flying season soon.
UPDATE: After repairing a burned out trace on the Eggtimer Quantum I was able to download the flight data for both the J570 and the Hybrid.
This is not the end of project, just the conclusion of the beginning. We learned that sorbitol can be a viable grain for the Aerotech RMS Hybrid motor allowing those that have these to fly them again. The project would not have been able to happen without the help of certain people and I would like to thank them here.
Gary Rosenfield: Technical Advice
Jordan Slavish: Machining
Edward Warnosky: Technical Advice, Material Support
Stu Barrett: Material Support
Christopher Pearson: Material Support
Tim Covey: Technical Advice
Alex Pavlik: Technical Advice
Leland Dexter: Technical Advice
Patrick Carroll 