Semi nozzleless

[NeighborJ]

Has anyone ever tried to make rockets with a rubber star type formula as a nozzle. I know I've seen someone use the cavity after the nozzle to make strobe and coloured effects but I'm thinking of replacing the nozzle with a comp which can erode at a rate which creates a neutral burn rate. I believe a semi nozzled rocket can use hot fuel to get away from the regressive burn characteristics typical of nozzleless rockets. Any thoughts?

[mabuse00]

Something like that was posted here not very long ago, I just cannot find the posts again...

 

 

I believe that any pyrotechnical composition would burn very fast under the extreme conditions at the nozzle area, thus it will open up to fast and loose thrust, creating a regressive behaviour again.

 

 

My idea upon this certain post here was not to use strobe or color mixtures under the nozzle, but rather some really hot whistle mix.

In combination with an endburner above. Like a 2 stage setup...

A booster that kicks the rocket straight up, and secons stage the keeps the velocity.

[dagabu]

Yupper, done that with Red Metallic Fueled, parts, not by weight. 2 increments of red and BP above that. I like the whole casing filled with this comp better, a slower rise, very nice for the Rockets Red Glare of the national anthem.

 

Strontium Nitrate 53

Magnalium, granular, -325 mesh 19

Parlon 17

Red Gum 5

Charcoal Airfloat 5

Sulfur 5

Dextrin 5

Edited August 30, 2016 by dagabu

[NeighborJ]

I'll need to try that red fueled but I still believe it could be done possibly with the addition of a negative catalyst such as tidioxide. I really wouldn't care if the nozzle mix couldn't burn on its own. I have a delay mix which uses it and I was surprised to find how unaffected it was under combustion pressure. I'd need to do some calculations to see if the burn rate will match the burning surface area/nozzle ratio. I know I can likely throw these calculations out the window due to the frictional forces of the nozzle gas. I just wouldn't have a way of dialing it in without an acme motor tester. Each motor style will need different comps for optimization. I was thinking of removing the load cell from a bathroom scale and rig it up to my meter. It wouldn't give a weight but I could at least tell if it is regressive or progressive rate.

[AzoMittle]

Interesting idea, I like it! Perhaps use a lance formula that burns slower to begin with, or a burn rate inhibitor like you said, heck you could probably even use something like a 75% comp 25% clay mixture.