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Nov 11 2014

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A case for going to Mars’ moon Deimos instead of Mars itself

The Deimos case, Part 1. Part 2 will be out next week. The author makes a good case:

  • It’s cheaper, from a deltaV perspective, to get to Deimos from Earth LEO than going to the Moon.
  • Because Deimos is tidally locked like the Moon so that the same side is always faced toward the Martian surface, and because Deimos’ orbit is slightly above Mars synchronous orbit (MSO), it rotates the planet every five and a half days. This would make it a better option for remotely operating rovers than from Earth.
  • Deimos’ base could be built underground, providing significant protection from radiation for long-durattion missions.

The author compares a base on Deimos to the base camp for ascending Mount Everest.

Those opposed to tele-exploration of Mars from its moons often lament this concept sends humans 99.99 percent of the distance between Earth and Mars and then stops. Our answer is the majority of funding and consumables expenditures, complexities, and risks accrue in traversing the last one hundredth of one percent. Likewise, the base camp at Mount Everest is 99.96 percent the distance between Houston, Texas, and the summit. Yet it is obvious the majority of challenges are in that final fraction of a percent. Successful ascents to the summit of Mt. Everest occur only after significant resources and supporting infrastructures are deployed at various base camps, and the majority of these resources never reach the summit.

Depending on the resources discovered, Deimos could be utilized as a staging area for the entire Mars system, including the surface. Deimos may hold valuable resources within its interior, and transportable main belt asteroid resources may lie just outside the orbit of Mars. In situ resource utilization (ISRU) at Deimos could be a game-changer for Mars exploration. If water ice deposits are found beneath the surface, a Deimos “gas station” could facilitate Earth return transits and even human missions to the Martian surface far sooner than anticipated.

A lot of good points, but I remain somewhat unconvinced, at least for a NASA mission. Going to Deimos just isn’t going to capture the imagination of the public like going to Mars will. It’s hard enough for NASA to get funding for a human mission to Mars. It’s hard to see how adding the intermediate step of going to Deimos will help from a public affairs standpoint. We’ll see if Part 2 next will will seal the deal.

That said, the article is worth referencing just for its detailed examination of the crew radiation hazard. They reference the
Radiation Protection (RP) scale, where a top score of 100 equals the protection that the surface of the Earth provides from space radiation. Here are some RP scores.

  • RP100: Surface of the Earth at sea level
  • RP50: 5500 feet altitude above sea level
  • RP2: on board the ISS.
  • RP0.1: inside a space suit

And NASA’s career space radiation exposure limits, based on the concept of Risk of Exposure Induced Death, or REID. NASA’s limits aan astronaut’s career at a cumulative dose of 3% increased risk.

  • 0.01 milliSeivert: Avg annual dose on the surface of the earth (RP100)
  • 50 mSv: occupational cumulative dose allowed per year in the US per OSHA.
  • 160 mSv: Annual dose on the ISS (RP2)
  • 219 mSv: Annual dose on the surface of Mars
  • 657 mSv: Annual does in deep space while inside a space ship
  • 1000 mSv: Career dose allowed to NASA astronauts (REID = 3%)

Digging a mere 7 meters under the surface of Deimos provides an RP100. (Moon: 4.12 meters, Mars: 2.65 meters for RP100)

Finally, for spacecraft, the author recommends:

RP5 (51.5 grams per square centimeter shielding equivalent) is a particularly attractive compromise level of protection for the entire crew compartment in transit. Not only will it protect the crew from acute radiation sickness for all but the most intense solar storms, it is an inflection point beyond which additional shielding doesn’t decrease the dose equivalent significantly until much higher levels of shielding are attained. In other words, RP5 provides the most reduction in radiation dose for the least mass. Considering other attributes of our proposed mission architecture (see below), RP5 (2.5 times the protection provided by any spacecraft to date, over 10 times the protection of the Apollo lunar lander and 50–100 times the protection of the spacesuit) can now be considered within the realm of reasonably achievable.

All very worth the reading (and the time to assemble it here) for this sci-fi author.

UPDATE: Not much new in Part II of the article. While this idea has some merits, I don’t see it as politically viable for NASA. For the same reason (doesn’t capture the public’s imagination), I don’t see a commercial space company using the idea, either.

Permanent link to this article: http://www.newspaceraces.com/2014/11/11/a-case-for-going-to-mars-moon-deimos-instead-of-mars-itself/

1 ping

  1. Measuring cosmic radiation at 39,000 ft | Off to the Space Races

    […] This is at least tangentially related to my post here which had a lot of detail on space radiation. […]

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