Hybrid Rocket Motor Aerospike Nozzle Tests

This is a combination of 3 test firings of an Aerospike nozzle for my Senior Project in Aerospace Engineering from California Polytechnic State University in San Luis Obispo.

The test bed hybrid uses gaseous oxygen, GOX, and a 2" dia Plexiglas tube as the solid fuel. The Oxygen is at 100psi.

The first test run was not choked, which was expected for the throat area is ~10 times greater than what the ideal area should be. The ideal gap between the spike and the compression cowl needed to be .003", yes, 3 thousands of an inch. However, if this were too small, this could produce a thermal choke well in front of the actual physical choke, which would reduce the performance of the rocket. I machined the compression cowl to have a gap of .053" instead. This would have allowed me to re-machine it smaller to maximize the thrust of the rocket.

I planned to fire the test for only 10 seconds, however I got distracted and allowed it to fire for 20 seconds, 2-3 seconds shy of turning the two piece nozzle into 3 or more pieces, that's what all the sparks are at the end.

This nozzle was machined out of 4140 Chrome-Molly. What took over 32 hours of CNC machining only took 20 seconds to destroy.

The second set of fires is with the newer nozzle design which reduced the stagnation zones that burnt up the first nozzle. As you can see, this one produced over twice as much thrust than the first nozzle, this one was machined to have a throat gap of .013" which may have over choked this nozzle which leads to this being thermally choked which may explain why you can't see any fire out the end. However, it is a reusable aerospike nozzle. Thanks for looking.

Now you know why they call this rocket science.

Category:

Science & Technology

Tags:

• aerospike
• hybrid
• rocket
• motor
• diamonds
• space
• engine
• cal
• poly
• oxygen
• propane
• plexiglas
• nozzle
• aerospace
• engineering

[jpourkav]

you should try using graphite for the nozzle, it stands up to heat quite well...its what we use over here at Arizona State for most of our rockets

[ragobgar]

@jpourkav Yep, that was the next step, just didn't have enough time to implement. Though maybe now for a thesis...hum....

Thanks.

[MarkieSKII]

Okay ive got a question, whats the purpose? is it for flying? -in english please- :p

[ragobgar]

@MarkieSKII This test was for feasibility. Hot fire testing of an aerospike nozzle at Cal Poly has been attempted only a few times. I wanted to prove that it could be done successfully, but the main project behind the testing was to produce a working computer model of the nozzle. For if the model says one thing and your actual motor produces another, then something is way off, but if they are close, then you can scale up from small to big rockets, eventually leading back into flights.

[Alexpaths]

Dr. D put some pressure on us at CPSS to get the flight hybrid consistent to use as a 401 demonstrator next year. We are looking at 500 lbf thrust.

[ragobgar]

@Alexpaths Assume.....how'd it turn out? sorry been away from this for too long..

[elvinhickma12k]

Your video is popular on Netherlands

[Lightspit]

@jpourkav graphite was used by Germans in WW2 on the V2 rocket on the basis that in the flame it is no oxygen so the graphite will not ignite and burn. Englishmen can certify that the system worked.

[macintosh39]

make a tutorial its amazing

[gmrwawa]

question?

instead of focusing the heat proof material, can you redesign, the exit of combustion chamber and to direct the flame flow in the way that don't accumulate to much heat??

if you can, machined the spike in side the combustion chamber, perhaps the flame and temp can distribute faster and evenly.

[seldian]

Wish i could go to college for shit like this, unfortunately i blow at math.

[pinz2022]

@ragobgar

Did Rutan's crew ever figure out what went so horribly wrong that day? The big selling point of NOS was that it was supposed to be safe.

[pinz2022]

@himoroyden

Has anyone ever used ablatives to line a rocket nozzle as opposed to a re-entry heat shield?

[pinz2022]

@jpourkav

Makes me think of a number of the old science fiction stories of yesteryear. In them, the hero-genius somehow manages to discover an alloy completely immune to heat, but which can still be machined.

I guess that's what you engineering types call "un-obtanium", eh?