Reasons To ARM Wrestle – Item 7
Developing technologies for a Phobos/Deimos large sample return.
One of the keys to affordable exploration and settlement of Mars will be determining if Phobos and/or Deimos have water in them, and if so, how to extract it efficiently. Having a large source of propellant feedstocks available in Mars orbit (for supersonic retropropulsion on landing, hydrogen feedstock for surface ISRU, and Earth-return propellant) could significantly reduce the amount of propellant needed for both round-trip and one-way Mars missions. If Option B is selected, and if it is designed properly, it would be possible to use the same hardware to capture and return a decent-sized sample — more than 1 metric ton — to lunar distant retrograde orbit (DRO) for evaluation and hopefully ISRU process development/debugging.
There is an operationally rough descent to Mars, due to the sparse Martian atmosphere. We really can’t rely on an Earth-like reentry using aerodynamic forces and parachutes to slow us down. Of course, this means using copious amounts of propellant to slow down large and relatively delicate Mars mission craft for a proper landing on the Red Planet. So do you carry your fuel all the way from Earth, or use ISRU to produce what you need at Mars? The solution here, which I certainly agree with, is ISRU propellant production as a baseline.
With that in mind, if Phobos and/or Deimos can serve as a resource complex, that’s ideal. Goff’s assertion of using the Option B mission as an operational and technological training ground looking forward to Martian resource assays makes good sense. The only area that I disagree at all is an assumption that Option B hardware would be used for the Martian missions. Given the sorts of timelines we are subject to in developing space missions, lessons learned will play a big part in each mission, in the design of every system. Even in the relatively break-neck pace of Apollo, no two spacecraft were the same, there were always upgrades from mission to mission. I’m not really criticizing Goff here, rather I’m just pointing out that the evolution of missions will improve upon Option B successes and failures.