Inhibited vs uninhibited pros and cons?

[Crimson0087]

Question. I have been working on getting a motor with 4 bates grains with the outside inhibited. Is there an advantage to doing it this way other than increasing burn time? Would it be better if I simply had 4 fully uninhibited grains with a core through the center and just had a larger nozzle? I know that it would be a very short burn but wouldnt it have more thrust?

[NeighborJ]

An inhibitor sleeve really doesn't displace much fuel, maybe a gram on each grain. If you are planing on using multiple grains, they must be inhibited to protect the casing from burnthru. If you use only one grain cast tightly into the case you won't need an inhibitor because all fire pathways between the fuel and case are effectively sealed with fuel.

 

An inhibitor sleve doesn't need to be thick unless it is a very large motor with extended burn time.

[stix]

With four fully uninhibited cored grains, I imagine you would get immense initial thrust then it would fade out.

 

You would need to have a casing that could handle that sort of pressure. You would have something that resembled more of a missile than a rocket.

[dagabu]

I experienced nozzle clogging and subsequent CATO with uninhibited grains. Not every time, mind you but often enough to abandon the research. I used to have a few AeroTech casings that I used my own grains and scratch built graphite nozzles in, I think that is where I would go if I were to do it again.

 

For pyro, I would make my own paper casings, press in a clay nozzle, make r-candy then shred it to small pieces, add an increment and press just like a BP motor.

 

I think I would use a skinny spindle with a a bell shaped nozzle, as close to a de Laval nozzle shape as possible. Yes, I understand that the shape will only apply maximum thrust for a short while but it will not decrease the raw thrust before or after the delta is formed.