I think his basic architecture is excellent and some 10 years ago got me re-energised about manned space exploration. Though:1): He's optimistic on the vehicle masses. But just how optimistic? A detailed re-analysis should clear that up. But you're right about the ERV mass; it'd probably be 3 times that quoted 3-ton mass, even with all-composite strutures.2): I think he also underestimates (but not massively) the danger of cosmic radiation and coronal mass ejections, the two major rad-dangers. 3): I think 5 would be a good crew number, not 4 -- one crew member would essentially be 'spare'. The loss of life of one member on a 4-person crew would be a terrible blow for mission completion. Losing 1 of 5 -- less so, of course.4): Re-size Mars Direct vehicles and logistics for 5 crewmembers, increase radiation shielding, and maybe -- adopt a more 'Semi-Direct' architecture which Nasa once touted.An upgraded Ares V could do a revised Mars Direct -- Regenerative RS-68's, slightly 'stretching' the EDS upper stage and increasing to 2x J-2X, adding some small solids (like those from the Atlas-V) would give a payload increase from 130 to 150 tons, enough for a more realistically revised "Mars Direct Version 3.0".Or, you could adapt my own Mission Architecture, which nods to Zubrin anyway.
Kaputnik - 30/3/2007 8:33 AM...not just a test-bed for Mars technologies, because we can test those in orbit at lower cost.
aftercolumbia - 30/3/2007 9:17 PM- Aerocapture is silly, we went with direct landing
RedSky - 31/3/2007 7:23 AMWhat I worry about with any direct entry landing scheme (i.e., no orbit insertion first before landing) is what is the contingency if a few weeks before entry, it is determined that a landing as scheduled is unsafe. This could be anything from a global dust storm, to some suspect equipment that may need troubleshooting. With a direct entry, there is no option for a wave off, is there?
I remember when Mariner 9 got to Mars, it took a month or two for a global dust storm to settle down so that the surface became visible. Since the crew will be at Mars for 18 months or more, being in orbit and able to wait out such events seems wise.
aftercolumbia - 5/4/2007 4:51 AMOxyhydrogen propulsion is far more mature at this scale than aerocapture at any scale. Also, given the mass penalties of having the extra aerocapture shield (or heavier single shield), plus the vagaries of retaining or doubling up on deep space power (probably solar, but even nuclear would still involve external radiators), the question of which option is heavier needs more study.To another post: Direct entry liftless is about 6-8g, depending on the arrival speed. A liftless entry won't happen because the chances are too good you will land quite far from the ERV/MAV (up to 100km). An L/D=0.16 entry can probably reduce it to 4-6g. L/D=0.5 could reduce it perhaps to less than 1g (theoretically, about 2.5-3g(Mars).)
Verio Fryar - 5/4/2007 11:37 AMDirect entry when returning to Earth is in the baseline of almost every mission plan. It should be much harder on the astronauts because of the higher velocity and they being weaker after 2+ years in space.
Verio Fryar - 5/4/2007 10:37 AMDirect entry when returning to Earth is in the baseline of almost every mission plan. It should be much harder on the astronauts because of the higher velocity and they being weaker after 2+ years in space.