Propulsion High Power Rocketry Hybrid Motors I have been testing a number of commercially available small hybrid rocket motors for a while now - the RATTWorks H-70 and I-70 hybrid rocket motors. These hybrid motors use NOx as the oxidiser, and offer great safety benefits over other rocket motors. The motors neccesistated an automated, ground based oxidiser fill system, so I decided to build one sufficiently flexible to allow multiple motors to be filled at the same time. It was not as expensive as I expected (about 200 pounds) to build it, and just involved some careful plumbing of the flow lines to the ball valves and solenoid valves. The test rocket designed to accomodate these motors, is a fairly small diameter vehicle (38mm) - enabling the rocket to fly to altitudes of 6000-7000 feet (depending on launch conditions). The vehicle was designed using Rocksim 4.0. Flight simulations were also run on Alticalc to allow a comparison between the 2 software packages. The airframe was completely fibreglassed with 3 layers of thin fibreglass cloth and polyester resin, and the fins were made of G-10 fibreglass. The recovery system uses the anti-zipper technique, and is electronically inititiated, since unlike some solid rocket motors, hybrid rocket motors do not have built-in ejection charges. A custom built payload bay frame was built out of aluminium and stainless steel studding, to allow different payloads to easily be swapped in and out of the payload section. The payload bay accomodates altimeters such as the ALTACC, the IAX-96 and the G-Whiz LC Deluxe, and has sufficient space for the batteries and additional engineering/scientific payloads.