I'm working on a small computer program in VB that calculates the mass of propellant a spacecraft needs from its ISP, empty mass, and the deltaV that's required. I've rearranged the rocket equation, but when I put the numbers in, I get completely wrong results.
The rearranged rocket equation:
P = M * e^(dV/(g*Isp)) - M
whereas P = Propellant Mass
M = Empty Mass
e = 2.718....
dV = DeltaV
g = 9.8m/s^2
Isp = Specific Impulse
According to Orbiter, a spacecraft that weighs 1770kg, has an ISP of 3000 (from a spacecraft.dll file) and a fuel mass of 900 will get a deltaV of about 2900. However, when I put the deltaV, the ISP, and the empty mass into my program, it says the required fuel is only 183kg. Now, I noticed that the equation requires an ISP in seconds, but the pdf for spacecraft.dll says its ISP is in N/kg/s.
How do I convert the ISP from a spacecraft.dll file to the ISP for the rocket equation?
The rearranged rocket equation:
P = M * e^(dV/(g*Isp)) - M
whereas P = Propellant Mass
M = Empty Mass
e = 2.718....
dV = DeltaV
g = 9.8m/s^2
Isp = Specific Impulse
According to Orbiter, a spacecraft that weighs 1770kg, has an ISP of 3000 (from a spacecraft.dll file) and a fuel mass of 900 will get a deltaV of about 2900. However, when I put the deltaV, the ISP, and the empty mass into my program, it says the required fuel is only 183kg. Now, I noticed that the equation requires an ISP in seconds, but the pdf for spacecraft.dll says its ISP is in N/kg/s.
How do I convert the ISP from a spacecraft.dll file to the ISP for the rocket equation?