Improving Mars Direct

It should be possible to improve upon Robert Zubrin's "Mars Direct" plan:

Zubrin's plan is good, but we could make the mission much safer. There are two main potential failure points in Mars Direct that are risky for humans: Will the crew vehicle be able to aerobrake into orbit and land; and will the ERV be able to lift successfully from Mars?

Reduce both risks by simply not landing humans in the first few missions. Instead, land robots to be tele-operated from a Mars orbital station. Eliminating the mass of the lander and aerobraking shield allows the ship to arrive with enough fuel to get into Mars orbit using the 3rd stage rocket. Even better, use two rockets, providing backup, and to act as each other's counter-balance when rotating for artificial gravity - no need to discard the 3rd stage rockets. Instead, the crew can return to Earth on the same ship(s) in which they arrived. They just need fuel for the return trip - and Zubrin's approach can be used to generate and deliver that to orbit before the crews even leave Earth.

That eliminates the two biggest human risks of Mars Direct, but brings back the risk of radiation. Cosmic rays might be partially shielded by orbiting very close to Deimos or Phobos. Water tanks over the crew quarters, and the rockets and fuel tanks below crew quarters, can provide more shielding. In the event of a solar flare warning, they can "duck" behind the moon. It should be possible to reduce the overall exposure to no greater than that experienced on Mars' surface. Later missions can test un-crewed landers, until we have proven landing and return to orbit capabilities.

Further improvement might be gained by eliminating the need to land tons of hydrogen. Recent observations by Mars rovers seem to indicate that water may be available in the soil. After all, only a small over-burden of soil would provide sufficient pressure to halt sublimation of ice. The fact that water was observed apparently collecting in dusty drops on the rover would seem to indicate that the heat of the rover warmed the ground enough to trigger sublimation of the uppermost layer of ice, with the gas then escaping and collecting on and near the rover. Water may be much more easily available on Mars than we have ever dared hope! (This also goes toward supporting my hypothesis that layers of ice and dust might build up over time, then become exposed horizontally and begin sublimating, being eroded by the wind, and collapsing- creating most of the "flowing water" gully-like and "mud-flow" features we see on Mars.)

Simply dumping heat from the nuclear reactor into the ground may create enough humidity to extract water from the air. Since the reactor is on a "truck", it might rove about (using nuclear electric power), warming the ground, collecting the sublimating water vapor on a chilled surface, and scraping it into an insulated container. This is the sort of spontaneous experiment that having humans and robots at Mars could enable.

Comments

Tom Craver said…
In 2023, we're finally starting to hear hints that NASA is indeed considering a "Phobos First" approach to Mars, including fuel production and teleoperation of surface robots.

A few added ideas:
Oxygen is the majority of reaction mass for a methane or hydrogen fueled ship. Mining oxygen from Phobos (or Deimos) regolith oxides should be less difficult than extracting whatever water resources might be there.

So a ship can arrive at Mars orbit with just enough O2 to get to Phobos, re-load enough to land and optionally enough to lift off back to Phobos, and then take on enough O2 to return to Earth.

That reduces fuel AND O2 requirements at every stage, which in turn reduces the size of the solar farm needed to produce fuel and O2 on Mars surface, and in turn means increase of other payload that can be delivered to the surface.

Another concept to consider: while solar power satellites might be questionable for Earth for several reasons, they seem very well suited for Mars:
- Beamed power could penetrate Mars dust storm with little attenuation.
- Manufacture of rectenna arrays will be much more viable in early days of Mars colonization.
- Given the more continuous and less attenuated solar energy in orbit, fewer solar panels will be needed - though there would be an increase in mass for the orbital beaming antenna. Perhaps that and the initial rectanna array delivered to the surface roughly equal the mass needed from Earth for a surface solar farm, though the need for batteries could be greatly reduced. And most of the mass won't need to be carried down to Mars.
10:27 PM, January 31, 2023
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