Talk:Mars Direct

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1., The plan involves launching an unmanned Earth Return Vehicle (ERV) directly from Earth's surface to Mars using a heavy-lift booster (no bigger than the Saturn V used for the Apollo missions), containing a supply of hydrogen, a chemical plant and a small nuclear reactor.

==> Atomic reactor launchd to space? Try to sell that to the general public! Even the plutonium thermo-decay powered satellites are dangerous enough, we need not more chance for radioactive pollution through launch failures!

I think the article might be misstating the plan here. I think from my memory of reading "a case for mars" a few years ago that the plan calls for the same sort of thing (thermo-decay) that we are already launching.

Nope, just read the synopsis in the book The Case for Mars. A small nuclear reactor is definately called for. I can get the power output info if you want it. I'm not sure what kind of safeguards are in mind for the reactor, but I'm sure that something could be arranged. Verad 07:14, 23 July 2006 (UTC)

The reactor would not be turned on untill it got into space, so there will be no danger of the release of fission products on earth. Once in space, it will have some control system, but even if there is a meltdown, the materials will be released into space. The uranium fuel (I think that is what they plan to use) used is only slightly radioactive. I am not sure about sheilding, beacuse on the way there it is unmaned, but on the way back there will be people on the ERV. I think they will expell the reactor and use batteries or fuel cells or something else before they got to earth (possibly just before entering earth orbit), so the reactor does not go on earth or in some orbit near earth. Polonium 22:09, 12 August 2006 (UTC)

Also, the public concern about launching nuclear power plants is exaggerated IMHO. There wasn't much fuss concerning recent space probes like Cassini and Pluto Express. There were protests, but I don't consider them significant. -- KarlHallowell 17:51, 2 January 2007 (UTC)

2., A second vehicle, the Mars Habitat Unit would be launched on a high-energy transfer to Mars carrying a crew of 4. This vehicle would take some 6 months to reach Mars. During the trip, artificial gravity would be generated by tying the spent upper stage of the booster to the Habitat Unit, and setting them both rotating about a common axis.

==> That's not artifical gravity, that is only good to make people crazy by constantly confusing their inner ear (the balance sensor of the brain). They will get nausea, curse Mr. Coriolis and vomit all the way to Mars and have faces greener than ufonauts upon arrival.

THe plan actually does all the math on this. It calls for attaching them to eachother at a pretty significat distance (over a mile) so that a marse level of "gravity" could be generate at low RPMs (less than 1RPM) with minimal coriolos forces.

Rotations of several RPM is sustainable. As I understand it, 1 RPM is a traditional bound for no observable effect in people. -- KarlHallowell 17:51, 2 January 2007 (UTC)

3., the Habitat Unit aerobraking into Mars orbit before soft-landing

==> Mars has only 1/100th dense athmosphere as the Earth. Big structures, like a crew carrier spaceship cannot aerobrake there, they will need huge retrorockets and you can afford that weight with current technology!

Again I think the math on this one works out as well. The nice thing is you can go deeper into the atmospheer and do it mroe than once. Anyway I might go look up the details and add them to the article.

What do you mean by "large"? Mass versus cross-section of the vehicle is what matters here, not the absolute size of the vehicle. Even if a vehicle has a poor shape for aerobraking (eg, is needle-shaped and thus has a high mass versus cross-section area), one can still increase the effective area by using some sort of drogue parachute. -- KarlHallowell 17:51, 2 January 2007 (UTC)

4., The soviets wanted to make manned moon landing with multi-ship approach (2 Proton ELVs) but they abandoned it because the risks were too much due to complexity. Yankee should consider the 1979 iranian hostage rescue helicopter fiasco for a familiar story on how complexity skyrockets risks.

My comments indented above Dalf | Talk 10:02, 2 January 2006 (UTC)

A lot of the risk is mitigated (and complexity reduced) because people aren't launched until there is working infrastructure on Mars. In particular, the methane and oxygen for returning to Earth is already in place and the ERV has been vetted (well as much as it can be remotely) when the manned vehicle takes off. That in turn means that the nuclear reactor associated with the ERV and methane processing has worked for 18 months on Mars and that the aerobraking system has been successfully tested. One interesting feature of Martian expeditions is the discussion of failure abort modes. For example, The Case For Mars provides considerable detail of abort modes for both the Mars Direct and a NASA proposal issued about the same time (though understandably biased towards Mars Direct IMHO). -- KarlHallowell 17:51, 2 January 2007 (UTC)