16 thoughts on “Mars”

  1. Another example of ignorant NPR “news”. From the article:

    Then there’s the question of whether you can even land on a planet with such a thin atmosphere. And if people do manage to make it to the surface, the first Martians will have to cope with everything from cancer-causing radiation to dust.

    “Mars has a big dust problem,” Dittmar notes.

    Absolute drivel, completely contradicted by historical facts such as the Moon landing and the unmanned Mars landers.

      1. Parachute landings have a physical mass limit for landing on Mars.
        There are also practical issues with aerobraking large and heavy payloads. These can be worked around with the appropriate engineering, which might look a lot like a rocket powered descent, a la the Apollo lunar missions.

        People that imply that landing large payloads on Mars is some mystically difficult problem don’t know their physics very well and/or have a hard time making the conceptual leap to an Apollo style landing applied to Mars.

        1. “People that imply that landing large payloads on Mars is some mystically difficult problem ”

          Hmm, I don’t know. People made a pretty big deal about the 7 minutes of terror and the skycrane. It looked pretty difficult to a non-engineer and the payload was rather small for all the effort.

        2. There is an issue with the nature of the Mars regolith. It may be necessary to send some robots ahead to build a landing pad, so a rocket lander doesn’t land in a deep crater of its own making.

          1. Rand, the dispersion angle of the Dragon 2 has a high degree of cosine. It might be that Dragon 2 disperses a ring rather than a crater if such or its derivative were to be used on Mars. An interesting open question.

      1. That was an interesting read.

        They have several built in assumptions that need not be the case:

        1) aeroshield size. Limited by today’s launch vehicles diameter. NASA is looking at inflatable structures for this as mentioned in the article.

        2) propulsive deceleration assumed to be “impossible” at supersonic speeds. That turns out to be false, as shown by the Falcon 9 first stage entry.

        3) assumptions about the propulsive budget. Mission design could spend propellent to enter Martian orbit, making the landing descent problem quite different. Propellent might come from Diemos. Or electric propulsion might be used. Or aerocapture.

        Yes, it is a challenging problem. Yes, the scaling makes large payloads have a different solution than smaller payloads.

        Definitely as problem that can be handled by current engineering using current materials and processes.

      2. @ Bob-1,

        Interesting article, thanks for posting it.

        I can’t help but note (as do you) that it’s rather dated. This is especially true regarding propulsive descent. The main problem (true when written) they cite with using rockets to go from supersonic to landing is that no one knew how a rocket firing into the velocity vector in thin but significant atmosphere would behave in that regime (plume instability, etc).

        That’s no longer the case. When SpaceX’s F9 does its slow down burn, it’s moving at those speeds, and in air roughly as thick as that on Mars. Also, the boostback burn is done at a considerable angle to the velocity vector, giving “off center” data.

        Given SpaceX’s interest in Mars plus their penchant for doing tests as part of operational missions, I’ve always wondered if it’s pure coincidence that the F9’s recovery burns give Mars-relevant data. 🙂

        Anyway, IMHO, it looks to me as if one solution to the problem of landing something heavy on Mars is to use a heat shield to get down to about Mach 5 and about a mile in altitude, then go propulsive the rest of the way. (That’d require a lot less propulsive delta/v than, say, a lunar landing).

    3. You may have to resort to propulsive terminal approach to land a large object intact on Mars. I’m not seeing how that’s worse than all propulsive breaking to land on our moon.

      If loose dust kicked up at the landing site is a problem, what about landing a sweeper bot ahead of the main payload to prepare the site?

    4. Dust is a big issue. It’s likely toxic to humans if it is similar to Lunar dust and like Lunar dust it will cause many problems with machinery. IIRC, the problems arise because the dust is very small and jagged. The Space Show has some good episodes that talk about dust issues.

      1. Without doing a bunch of searches for information I realize I could be wrong, but it strikes me that a significant part of the problem with lunar dust is that it is particularly abrasive. As I understand it lunar dust is made up of shattered or pulverized rock/metal/glass particles that have undergone no further significant modification.
        In contrast Mars has a tenuous atmosphere that generates strong enough winds to move dust and other light particles around the surface. Surely, if nothing else, this should suffice to knock off the worst of the rough edges. Of course there will still be the problem of potentially toxic dust particles getting everywhere and reacting aggressively once they come into contact with moist surfaces (lungs/eyes, etc.) but this should still be more manageable than it will be on the moon.

    1. Oh, I’m sure the Mars-landing problem is solvable. I’m just saying that no previous technique would be practical for a human landing. My solution would be to send some robots down to build a landing pad, and get propellant at Phobos or Deimos.

  3. My understanding (admittedly limited) is that Martian dust is just as bad as Moon dust, maybe worse, but for a different reason.

    Moondust, as already noted, is loaded with sharp and highly abrasive glass particles – not good stuff to breathe. On the other hand, Martian dust is loaded with some fairly corrosive and toxic poisons such as superoxides and peroxides. I wouldn’t want to venture an opinion as to which of the two is worse.

    Of course, on Mars there is the remote possibility of biological contamination – not a factor on the Moon, as it turned out.

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