THEONE Posted April 10, 2011 Share Posted April 10, 2011 what is better a low burning propellant (rcandy-BP-....) or a high burning ? Link to comment Share on other sites More sharing options...
dagabu Posted April 10, 2011 Share Posted April 10, 2011 I am not familiar with that nomenclature... Link to comment Share on other sites More sharing options...
THEONE Posted April 10, 2011 Author Share Posted April 10, 2011 (edited) I am not familiar with that nomenclature... We have rcandy that 1 inch burns in 10 sechave another that burns in 6 secother in 14 sec other in 19 sec....Which is better and why... Edited April 10, 2011 by THEONE Link to comment Share on other sites More sharing options...
dan999ification Posted April 10, 2011 Share Posted April 10, 2011 We have rcandy that 1 inch burns in 10 sechave another that burns in 6 secother in 14 sec other in 19 sec....Which is better and why... its how you use it that counts, my r candy normally burns around 10-12 seconds an inch, confined it burns a 1.5 inch grain in less than 1 second. no fuel is really better than the other its how you use it and what you use it for that defines it being best. bp rockets can sometimes use fast fuel for small motors and slower fuel for bigger ones i dont know if r candy is the same or not why so many inconsistency's with the fuel are they different[catalysts, additives]? getting consistent fuel gets consistent results. dan Link to comment Share on other sites More sharing options...
dagabu Posted April 10, 2011 Share Posted April 10, 2011 (edited) . bp rockets can sometimes use fast fuel for small motors and slower fuel for bigger onesdan Fuel consumption increases as the pressure and thermal energy builds. The hole fuel mass can ignite all at once if too much heat is created by the burning grain. Retarders are used to slow the fuel (charcoal and oil is popular with pyro). As far as R-candy burn speed goes, fast catalyzed R-candy is great for endburners and straight R-candy is great for long cored rockets. Edited April 10, 2011 by dagabu Link to comment Share on other sites More sharing options...
THEONE Posted April 11, 2011 Author Share Posted April 11, 2011 (edited) I dont remember very well but i make rcandy with 65/35 kno3 sugar (without any syrup) and it burns 1 inch in about 6 sec... (without red iron oxide)Maybe this is very fast for a core burner rocket correct ? Edited April 11, 2011 by THEONE Link to comment Share on other sites More sharing options...
dagabu Posted April 11, 2011 Share Posted April 11, 2011 Correct, you want 12-16 seconds for a core length x2 ID or longer and then speed it up slowly until it CATOs and then back off one step. Link to comment Share on other sites More sharing options...
THEONE Posted April 12, 2011 Author Share Posted April 12, 2011 Correct, you want 12-16 seconds for a core length x2 ID or longer and then speed it up slowly until it CATOs and then back off one step. Can you my friend explain to me little better this one? Link to comment Share on other sites More sharing options...
azure Posted April 13, 2011 Share Posted April 13, 2011 Fuel consumption increases as the pressure and thermal energy builds. The hole fuel mass can ignite all at once if too much heat is created by the burning grain. Retarders are used to slow the fuel (charcoal and oil is popular with pyro). As far as R-candy burn speed goes, fast catalyzed R-candy is great for endburners and straight R-candy is great for long cored rockets. A little charcoal or lampblack added to rcandy will increase burn rate quite a bit Link to comment Share on other sites More sharing options...
dagabu Posted April 13, 2011 Share Posted April 13, 2011 A little charcoal or lampblack added to rcandy will increase burn rate quite a bit Take a look at that again, the charcoal will reduce the burn rate if the fuel mix is optimized, charcoal becomes an IR blocker slowing the fuel consumption. If it speeds up your rocket, you are oxidizer rich and fuel poor. Link to comment Share on other sites More sharing options...
Mumbles Posted April 13, 2011 Share Posted April 13, 2011 I was under the impression that charcoal and lampblack could be added to act as an opacifier and increase the efficiency of radiant heat absorption, thus increase the burn rate. Otherwise the IR light which is produced largely passes through and diffuses through the grain, sort of wasting that additional energy. Link to comment Share on other sites More sharing options...
dagabu Posted April 13, 2011 Share Posted April 13, 2011 I was under the impression that charcoal and lampblack could be added to act as an opacifier and increase the efficiency of radiant heat absorption, thus increase the burn rate. Otherwise the IR light which is produced largely passes through and diffuses through the grain, sort of wasting that additional energy. Hmmmmm, maybe I got it all backwards? I have to go check my notes, wouldn't be the first time I got something wrong Link to comment Share on other sites More sharing options...
mabuse00 Posted April 15, 2011 Share Posted April 15, 2011 As far as I understood the blackening of the propellant prevents pre-heating up of the propellant below the burning surface, avoiding softening or affecting it otherwise before ignition. So the burn rate will be lower but more steady. Link to comment Share on other sites More sharing options...
dagabu Posted April 15, 2011 Share Posted April 15, 2011 As far as I understood the blackening of the propellant prevents pre-heating up of the propellant below the burning surface, avoiding softening or affecting it otherwise before ignition. So the burn rate will be lower but more steady. Why dont you and Mum iron this one out, I am confused now... Link to comment Share on other sites More sharing options...
Recommended Posts