clongton - 18/3/2008 9:03 PMMissions are sized what they are today because that’s what the available launch vehicles will support.
A_M_Swallow - 18/3/2008 3:58 PMLets try a mission that will be hard without a space depot - sending 100 metric tons to Low Lunar Orbit in one go.ISP of RL-10-2 burning LOX & LH2 is 462delta-v LEO to LLO = 4.04 km/sm0 = m1 exp(delta-v/(ISP * g)) = 100 * exp( 4040 / (462 * 9.81)) = 244 mTMass of fuel = 244 - 100 = 144 mTThis option would require 3 launches in a short timescale without a fuel depot.I am not certain that KSC is set up for machining gunning off Ares-V/J-232 rockets.
mike robel - 18/3/2008 8:27 PMBut, as I demonstrate in my above example, we either need 1 Jupiter 232 Launch and 5 Atlas V launches OR 2 Jupiter 232 Launches.
clongton - 19/3/2008 1:58 AMWhat you're missing is what I get to do with my propellant. If I drag it up with my spacecraft, I only have 25% left to do my mission with. If I buy it on orbit, I get to use it all for the mission. That is not included in your figures. You're trying to make it come out as if it were economically better or not. That's not the point.
mike robel - 18/3/2008 9:34 PMAnd, the 2nd 232 puts 100tons of fuel into orbit and burns none of it. You only burn only what it takes to get your primary payload into orbit, not 3/4s of the fuel that is being carried as cargo.