RRS Rocket Motor Class
Beginning Solid Propellant Rocket Propulsion Course put on by the Reaction Research Society. 17 March - 19 March, 2000. Mojave CA. Click on any image for a larger version.
Entrance to the RRS Mojave test area (MTA). From left to right. The new multi-level liquid fuel motor test stand. The solid fuel propellant mixing and packing shed. The old solid and liquid test stand. The block house (yellow building). At the right edge of the picture is the large Quonset hut (cut off in the picture) that is used currently for storage but is planned for propellant research activities. |
A view from the top level of the new liquid test stand. The MTA has a 50K AGL waiver for flights. As you can see there is not much about. |
Inside the big Quonset hut weighing out the liquid parts of the mix. In the propellant mixing shed a small kitchen-aid mixer is used to mix the liquids and metals. The formulation used has the curing agent added with the liquids and before the AP is added, so once the liquids are mixed the clock starts ticking. |
After the liquids and metals are mixed for three minutes, it is transferred to a large mixer and all the AP is added. Three five minutes mixes with two mixing bowl "scrape downs" are done. |
The individual grains are packed with the mixed propellant. A few important notes. Unlike the AeroTech motors they don't use a casting liner and a motor liner. Each grain (they call it a cartridge) is packed into a phenolic liner. Contrast this to the DPS method where a whole "stick" is packed and then the individual grains sliced off. |
The grains are cured in an incubator. The heat source is two light bulbs which raise the temperature to about 120F. They cure for about 4 hours. |
Because there is no motor liner used, the grains that make up the propellant load for the motor must be exactly sized or the motor will not seal correctly. This sizing is done by sanding the ends of each grain to a specified size. |
The grains are drilled to form a one inch core. |
The ends of the grains are beveled so as to allow a clean path for the flame front between each grain |
All the bits of propellant collected from the drilling are burned off in a big pit. This was done in the middle of the day. The picture only looks dark as the camera corrected for the incredible fire ball that erupted. |
Motor assembly. The motor hardware is very similar to the Kosdon type. Snap rings are used to hold in the forward and aft closures. The nozzle is make of graphite. One odd point: They specify a LOT of grease. Having got used to a "use it sparingly" attitude it felt very odd to "glop it on". |
The test stand is the red thing on the right of the picture. The static test instrumentation measured the chamber pressure and the thrust of the motor. The yellow cylinder contains compressed air and is used to calibrate the pressure sensor. A big 100 pound weight is used to calibrate the load cell (for thrust measurements). |
Hooking up my motor for test. Another odd thing is the igniter used is screwed into a threaded insert in the forward bulkhead. Equally odd is the choice of igniter material. They use a compound called ALCLO with is Aluminum powder and potassium perchlorate. I was told this is almost the same stuff used in fireworks industry for M80's and cherry bombs. An open air test of one of their igniters broke a concrete block. One the motor is ignited it is INSTANTLY up to full pressure. I've never seen anything like this before. Unfortunately I didn't get a good picture of the motor firing. Total impulse was 2,848 Ns or a small L motor |
The class in front of the old test stand. I'm third from the left in the back row |