We discussed several different fuel + oxidizer combinations and examined reasonable lateral velocities.
So we considered several different models for rocket fuel —
1) liquid O2 and H2
2) N2O and HTBP (rubber, $17.5/kg)
3) Ammonium perchlorate and Al+HTPB
These are somewhat expensive, but most importantly we decided that they’d just add an extra level of complexity that we’d like to avoid.
We also looked rocket engine data from reusable (not that we’d be likely to get it back) solid-propellant model rocket engines from Aerotech, and we found the M750W that puts out a 9325 N-s total impulse over ~15 seconds, but the propellant + casing is ~$1,000. This is 5 kg of rocket propellant — that’s a lot of heat!
We also played with the Tsiolkovsky Equation — See Equations 1 and 4 from Joe’s derivation.
We assumed a max. exhaust velocity Ve of ~ 4 km/s, and where Mp is 5.3 kg propellant and Ms is 3.5 kg propellant casing (for 8.8 kg total), we get about 4 km/s velocity on the rocket. And this doesn’t even include any mass Ms for an actual satellite we’d put up there, or Mr the mass of the rocket structure (which both go in the denominator in the logarithmic term, which is bad for us).
We need 8 km/s, which means we need to raise the ratio of m0/m1 as high as possible. More research in the works…
At the next meeting, we’ll be looking at purchasing cables and materials for small scale Delphiki testing, made possible by collecting our big winnings at the Rice Elevator Pitch competition (1st Place, Houston Entrepreneurs’ Organization award, $1000)!