Mars’ underground brine could be a good source of oxygen

Re:Mars’ underground brine could be a good source of oxygen by chongli on Thursday December 03, 2020 @12:08AM (#25285611)

Aerocapture with the thin Martian atmosphere is much riskier than aerobraking [1]. Since you’re trying to bleed off all of your delta-v in one pass, your margin for error is much lower due to the high energies involved. Aerobraking is much less risky but way slower, taking months to decelerate and so much less feasible with human passengers.

For landing on earth you only need aerobraking and parachutes. For the moon all you need are the retro rockets (we’ve already done it). To send humans to Mars you need retro rockets, a heat shield, and a parachute. The combination of systems makes the whole procedure a lot more complicated and error prone, increasing risk.

[1] http://sicsa.egr.uh.edu/sites/sicsa/files/files/projects/dec...

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Re:Mars’ underground brine could be a good source of oxygen by m4rtink on Thursday December 03, 2020 @02:35PM (#25293492)

Fair enough - and indeed, the Lunar delta-v needed is usually quite small. Apparently Chang'e 5 sample module needed just 1,67 km/s to reach lunar orbit for example.

Still, I think there are definitely cases where atmosphere helps (even if it causes issues elsewhere).

So even if you used propulsive breaking to get captured into orbit of a body with atmosphere for safety reasons, you can still capture into a very eccentric orbit & then carefully use aerobraking (as demonstrated many times at Mars already) to lower and circularize your orbit before landing. And with a bit better aerosurfaces you could even use the atmosphere to tune your orbits inclination as needed.

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