Apollo Alum - 7/7/2007 4:52 PMTo Bill White and Neviden: I did look at at least one LOR model. It only increases the delta-vee cost (LTO plus LOM = 1,900 m/s, TEI = 1,650 m/s, EOI + EOM = 3,200 m/s + 10% safety = 7,300 m/s). L2R might be cheaper, but by definition cannot be cheaper than the direct flight. I will take a look at using two reusable vehicles - one for LS - LLO (or L2) - LS, one for LEO - LLO/L2 - LEO, but will be quite surprised if it makes an appreciable difference.
Apollo Alum - 9/7/2007 3:44 AMNeviden: you miss the point. It IS possible to build a single-stage vehicle with an Isp of 450 and a delta-vee of 12.5km/s. It just would be quite large. Mass ratio on the order of 17:1. Big, but not impossible. The problem here is you don't start out with all your mass and then progressively burn it off. Halfway through the mission you fill either the LOX tank or the LH2 tank. Turns out the bird seems to even theoretically impossible to build, not just an engineering nightmare.
Apollo Alum - 9/7/2007 4:38 PMThe one big risk with using L-2 at this point is that we have absolutely no experience there. Since it is a stable "trojan" point, it may well have collected quite a bit of debris over the years.
Apollo Alum - 9/7/2007 4:38 PMThis also applies to L-2 with the additional problem that L-2 is out of radio contact with Earth.
Apollo Alum - 9/7/2007 11:39 PMNeviden: it sounds good, but do the math. Calculate how much mass you are moving from point A to point B to handle all your refuelings. It is easy to say "refuel here." It is quite another thing to calculate how much it costs to get all that propellant where you need it. Do the math.
GraphGuy - 16/8/2007 2:30 PMI think that you can ignore LH2 and use pure LOX in a NERVA style engine. You probably would not want to land near a base though.
meiza - 17/8/2007 1:26 PMCompressed oxygen? You have to heat it, it's not helium you know.
meiza - 17/8/2007 9:26 PMCompressed oxygen? You have to heat it, it's not helium you know.