So, I really have no idea where to post this, so I'm going to drop it here and it can be moved to wherever it is appropriate.
I'm trying to calculate the effective exhaust velocity of an engine which burns aluminum oxide and hydrogen gas at a bare-bones minimum temperature of 973.15 degrees Kelvin (700 C, the ignition temperature) The formula I have for specific impulse is Tc x Rgas, where Tc is combustion chamber temperature and Rgas is the specific exhaust velocity. It's a simplified version of the whole equation, and you can see where I got it here. First off, I believe my problem is in my equation for the Universal Gas Constant. The only one I've found that I know how to use is 8.3144621x(Tc/M) where M is the atomic weight. I've seen where the Universal Gas Constant is listed as 8.3144621x(J/mol K), but I don't know what the J, mol or K stand for, and have yet to find a definition.
When I use the weight in amu's, I get a number for the Isp ranging in the thousands (which I doubt), and when I use the weight in kg (1.66053982x10^-27) I get numbers to the power of -32, 40, 60 and so on. Another main issue is that I have been unable to get the same number twice. I know I'm doing something horribly wrong, but I don't know what. Here is everything that I know that I use for my calculations:
Exhaust total weight (amu): 43.98853
Exhaust average weight (amu): 14.66284
R: 8.3144621(Tc/m)
Tc: 973.15 degrees Kelvin
Ve (effective exhaust velocity): Rgas x Tc
Rgas: R/MM (total exhaust gas weight)
I posted this on the Physics Forums, but with over 30 reads and no replies, I assumed that nobody there has any idea how to help. This is for my school Science project, and I need an estimate of the Isp of an ALICE (Aluminum Ice) powered rocket to compare with conventional motel rockets. Plus, I like doing this level of math. Any help would be appreciated. Thanks!
I'm trying to calculate the effective exhaust velocity of an engine which burns aluminum oxide and hydrogen gas at a bare-bones minimum temperature of 973.15 degrees Kelvin (700 C, the ignition temperature) The formula I have for specific impulse is Tc x Rgas, where Tc is combustion chamber temperature and Rgas is the specific exhaust velocity. It's a simplified version of the whole equation, and you can see where I got it here. First off, I believe my problem is in my equation for the Universal Gas Constant. The only one I've found that I know how to use is 8.3144621x(Tc/M) where M is the atomic weight. I've seen where the Universal Gas Constant is listed as 8.3144621x(J/mol K), but I don't know what the J, mol or K stand for, and have yet to find a definition.
When I use the weight in amu's, I get a number for the Isp ranging in the thousands (which I doubt), and when I use the weight in kg (1.66053982x10^-27) I get numbers to the power of -32, 40, 60 and so on. Another main issue is that I have been unable to get the same number twice. I know I'm doing something horribly wrong, but I don't know what. Here is everything that I know that I use for my calculations:
Exhaust total weight (amu): 43.98853
Exhaust average weight (amu): 14.66284
R: 8.3144621(Tc/m)
Tc: 973.15 degrees Kelvin
Ve (effective exhaust velocity): Rgas x Tc
Rgas: R/MM (total exhaust gas weight)
I posted this on the Physics Forums, but with over 30 reads and no replies, I assumed that nobody there has any idea how to help. This is for my school Science project, and I need an estimate of the Isp of an ALICE (Aluminum Ice) powered rocket to compare with conventional motel rockets. Plus, I like doing this level of math. Any help would be appreciated. Thanks!