[Spaceships] simply fuel math...

[hal]

Originally Posted by RyanW

I believe the realistic dV formula was the rocket equation presented above, and hidden behind the table in Spaceships, except Spaceships abstracts the choice of fuels to a somewhat generic representation and a limited set of mass ratios so it doesn't have to deal with individual Isp (shut up iPad, Isp is capitalized correctly).

Always good to know about the abstraction aspect. I find it mildly interesting that the Delta-V formulas do not give a value of 1 for 1 tank. But, if I work it out (which I'm doing to do now... <after a pause>

Unless I messed up?

Formula for Delta-V is .003 x Isp x Ln(Loaded Mass/Dry Mass)

Solving for ISP when you know Delta-V

Isp = Delta-V/.003/Ln(Loaded Mass/Dry Mass).

I got an Isp of 974.79 for Rocket Fuels that grant .15 MPS per single tank.

I used a SM:9 hull of 3,000 tons, with one fuel tank worth 5% of the mass for the hull. I probably could have gotten the same results using Ln(1/.95) as I did for using a mass of 3000 and a dry mass of .95*3000.

Seems kind of high to me that the Isp is that high.

I'm tired and maybe I didn't do the math right. Double check?