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Crash Course in Safely Crashing on Mars

Posted by timothy on from the go-fast-turn-left dept.

An anonymous reader writes "NASA described today how they prepared for the twin air-bag crash landings on Mars. The sites are Gusev Crater on January 4th and Terra Meridiani on January 25th. The golfcart-sized rovers have double-lined bladders, that must protect against: the equivalent of a forty mile-per-hour crash, compression against a surface of unknown sharpness, impacts repeated in rapid succession up to sixteen times, and the big bounce covering more than half-a-mile. Airbag landings are considered easier than retro-rocket or soft landings."

27 comments

  1. Hmmm... by JofCoRe · · Score: 3, Funny

    Airbag landings are considered easier than retro-rocket or soft landings.

    Hey, maybe they should land airliners this way?

    ...and the big bounce covering more than half-a-mile.

    Hmmm... maybe not.. :)

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  2. Nonsense by Anonymous Coward · · Score: 0

    They claim the thing will land with 40MPH and bounce more than half a mile... well take 40MPH and multiplay it with the gravitational constant g=9.18 and you get ~350 feet, far less than half a a mile.

    1. Re:Nonsense by lexarius · · Score: 2, Informative

      Uh... you've got your units a bit off. 40 is "miles/hour", that g is "meters/second^2" (which is incorrect for Mars), and you somehow wind up with units of feet when you multiply them?

    2. Re:Nonsense by Anonymous Coward · · Score: 0

      Not sure, but it might be a joke relating to NASA, measures and previous attempts to conquer Mars...

    3. Re:Nonsense by Anonymous Coward · · Score: 0

      18 meters per second=40.241 miles per hour. This is speed on impact, not acceleration. See
      http://www.able2know.com/www/Detailed/1228.ht ml

    4. Re:Nonsense by cazzazullu · · Score: 1

      uh, I think you better check your physics-course before posting such nonsense. Imagine, reaching 350 feet up in the air by going the measly speed of 40 mph... Second, the gravitational constant of mars is far less than that of earth (too lazy to go check it out). You could pee over fifteen people in a row on mars. Thirth, you dont need to land vertically. Bouncing off at an angle of 45 degrees is the most effective to reach long distances (if you forget about friction with the atmosphere). Remember: x(t) = x0 + v0*t + g*t*t

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  3. please explain this sleep bit by ArmorFiend · · Score: 1
    Because the two rovers will be operating simultaneously on the surface, scientists monitoring their activities will have to set their clocks to Martian time, not Earth time. In practice, the extra 36 minutes each Martian day makes for a complicated rotation of workers' sleep
    That doesn't make any sense to me. Do the rovers only function well during daylight hours or something?
    1. Re:please explain this sleep bit by TMLink · · Score: 1

      Will the rovers be able to communicate with NASA when Mars has rotated so that the planet is between the rovers and Earth?

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    2. Re:please explain this sleep bit by Anonymous Coward · · Score: 0

      Don't they use satellite relays?

    3. Re:please explain this sleep bit by kanly · · Score: 2, Informative

      Yes, they do. They are solar powered; in fact, the mission lifetime is determined by how long it will take for the solar panels to become degraded by dust cover.

      I attended a lecture about sleep & human performance recently, and this question came up. The best strategy would be to keep the workers in an environment with a light pattern synched to mars time. Unfortunately, this would be very expensive. Even more unfortunately, since Spirit and Opportunity are landing at very different longitudes, they would need two.

      That's not going to happen, so they're just using blackout shades, and telling the engineers not to spend much time in the Big Blue Room.

    4. Re:please explain this sleep bit by Anonymous Coward · · Score: 0

      yeah.. sure.. we have a satellite shell around Mars...

    5. Re:please explain this sleep bit by lexarius · · Score: 1

      I'd say the large solar panels on top of the rovers (and most space equipment) might have something to do with this.

    6. Re:please explain this sleep bit by WTFmonkey · · Score: 2, Interesting
      how long it will take for the solar panels to become degraded by dust cover
      What about "windshield wipers?" A quick swish every few hours (or days, whatever) keeps 'em clean{er}. Or a quick shot of compressed air, or something like that?
    7. Re:please explain this sleep bit by rk · · Score: 1

      Uh, actually we do. both MGS and Odyssey are designed to be used as communications relays for surface missions.

    8. Re:please explain this sleep bit by ArmorFiend · · Score: 1

      Thanks,
      I guess on Mars you don't have to worry about cloudy (dusty?) days, so they forgo the weight of a serious battery. If its dusty/eclipse/night, they just go out for space brewskis...

    9. Re:please explain this sleep bit by jafuser · · Score: 1

      Since we have a tendency to revert to 25 hour circadian cycle anyway, it should be even easier for us to operate on a mars day than an earth day, as long as we don't have our cycle forced to reset by factors such as sunlight or alarm clocks.

      As to the dusty solar panels -- I wonder why they don't build on a robotic arm to brush off the dust? There must be more to it than just dust, or it would seem like a small investment could greatly prolong the life of the mission.

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    10. Re:please explain this sleep bit by Anonymous Coward · · Score: 0

      I thought exactly the same thing, do you think there is some red-faced engineer at NASA slapping himself on the forhead and repeating "wind sheild wipers ... damn it!" over and over again?

    11. Re:please explain this sleep bit by Anonymous Coward · · Score: 0

      Mars dust is incredibly sticky stuff. Truly inconvenient. Air isn't going to be effective. Windshield wipers need lubricant, and the last thing you want to do is introduce, say, water, when the probe is looking for water, or teflon, when the probe is looking for organic molecules.

  4. Lesson 1: by JasonMaggini · · Score: 1

    "Go that way. Really fast. If something gets in your way... turn."

  5. Air-bag landings by zero_offset · · Score: 1
    Airbag landings are considered easier than retro-rocket or soft landings

    By whom? I can't find the reference, but I remember reading after the last airbagged probe to Mars where a bunch of reasonably reputable engineers were decrying this approach, and insisting that parachutes were still the best.

    Sure the Martian wind storms would be bad for parachute descents, but it seems like you could mitigate that (this is me speculating now, I don't remember the discussion from the Real Engineers) by either delaying the landing by going to orbit first, or by combining air bags with chutes, or by using the chutes to control the descent trajectory. Or some combination. I'm not an engineer, but I do recognize all these are more complicated than just wrapping it in a bag, shooting it at Mars, and hoping for the best... but it does seem like a pretty sloppy way to design a landing.

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    1. Re:Air-bag landings by fredrikj · · Score: 1

      According to the article, the capsules first get slowed down severely by atmospheric friction, parachutes and helper rockets. The airbags are just there to cushion what's left of the velocity when the capsules hit the ground.

    2. Re:Air-bag landings by boarder · · Score: 2, Informative

      The problem with parachutes on Mars is not so much the wind as the air pressure (or lack thereof). Parachutes in the thin atmosphere have to be very big to slow things down. You also can't pop out a large chute when you are burning in at 20,000 mph. There is a ton of design, testing and re-testing to run up the mission cost. Materials are also more expensive for them. Single point failures also have a larger potential for disaster with a chute system. Recall the air force guy that did the skydive from 100,000 ft... he needed something like 4 parachutes to safely land: pilot chute (slows you down to a safe speed to open main chute), main chute, reserve chute (I read once that the main failed) with a pilot chute for it. In my senior design class we had to land a nuclear generator on Mars (something you wouldn't want to bounce around too much), and chutes were the only way to go. The only way we were able to land it was using ring chutes (very interesting opening mechanism) for the first section of the descent, then a normal chute for the second portion. Airbag systems seem to me to be MUCH simpler (therefore cheaper mission cost) and safer.

      The flip side to all of this is that airbags have only limited use. Precise landing area requirements, manned vehicles, "this side up ^" payloads, etc. all are better with chutes and/or retro rockets.

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    3. Re:Air-bag landings by Shadowlion · · Score: 1

      "this side up ^" payloads,

      Is this really an issue with airbags? I thought that the payload was designed so that it opened up like a flower, and thus any "petal" touching the ground would force the payload to right itself.

    4. Re:Air-bag landings by KlaymenDK · · Score: 1

      Well, consider this:
      What good is being able to place the glass topside-up when the beer's already on the floor (spilled while tumbling during the landing)?

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  6. Simpler solution... by jakedata · · Score: 1

    "The golfcart-sized rovers have double-lined bladders"

    This may be helpful, but wouldn't it be simpler to take a leak before the landing sequence starts?

  7. Lesson 2 by leonbrooks · · Score: 1

    ...and if you run out of ground - one of the multi-kilometer drops at the edge of Valles Marineris would be spectacular (being American, the craft would explode when it hit) but even a six-foot edge or hole would probably do - it's too late to stop even if there was no transmission lag. Oh, well.

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  8. I didn't realise... by leonbrooks · · Score: 1
    ...that the airbag-style landers had any feet.

    Will they end up looking like Rincewind's Luggage?

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