Zeropoint Posted July 14, 2012 Report Share Posted July 14, 2012 Re: More space news! I have a hard time understanding why, if they're afraid of dust getting on the rover, why they don't just give the lander a sealed cargo bay, land it, wait for the dust to settle, and then drive the rover out. The airbag landing system of Spirit and Opportunity seemed to work okay; why not use it again, or refine it? Quote Link to comment Share on other sites More sharing options...
Cancer Posted July 14, 2012 Report Share Posted July 14, 2012 Re: More space news! Didn't I post that a little while back? Anyway' date=' yeah, I'm rooting for Curiosity, but I'm not betting any money on its success. Seriously, all that landing sequence is missing is a mousetrap and a bowling ball.[/quote'] YOu did, my apologies. Quote Link to comment Share on other sites More sharing options...
Old Man Posted July 14, 2012 Report Share Posted July 14, 2012 Re: More space news! Np, it's certainly worth posting twice. @zeropoint: is Curiosity much larger than Spirit and Opportunity? I vaguely recall some discussion that the airbag system doesn't scale up. Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted July 14, 2012 Report Share Posted July 14, 2012 Re: More space news! That is a relevant question to which I do not know the answer. Quote Link to comment Share on other sites More sharing options...
L. Marcus Posted July 14, 2012 Report Share Posted July 14, 2012 Re: More space news! I think Curiosity weighs in at about four tonnes ... Quite a bit heftier than its predecessors. Quote Link to comment Share on other sites More sharing options...
Christopher Posted July 15, 2012 Report Share Posted July 15, 2012 Re: More space news! Curiosity per wikipedia weights: 900 kg http://en.wikipedia.org/wiki/Mars_Science_Laboratory Opportunity: only 180 kg http://en.wikipedia.org/wiki/Opportunity_rover#Design_and_construction Apparently togehter with the thin athmosphere of mars this is a big weight to land it safely (i.e., without instruments going haywire/beign damaged). Opportunity had a planned mission time of 90 days, that it worked that long is sheer luck. This one is planned for a much more intensive, much longer survey. Ideally it is there when the first humans land. Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted July 16, 2012 Report Share Posted July 16, 2012 Re: More space news! Okay, given that surface area scales with the square of max dimension, and weight scales with the cube, I can see that covering a craft in airbags might not work for larger craft. My question about a sealed cargo bay stands, though. Quote Link to comment Share on other sites More sharing options...
Christopher Posted July 16, 2012 Report Share Posted July 16, 2012 Re: More space news! Okay' date=' given that surface area scales with the square of max dimension, and weight scales with the cube, I can see that covering a craft in airbags might not work for larger craft. My question about a sealed cargo bay stands, though.[/quote'] I think this landing system is more about bringing it down in one piece. And this thing propably has equipment that doesn't likes impacts very well. You simply can't just aerobrake, rocketbrake or parachute it down. You have to use a multiple way appraoch to get something that mass down on mars safely (with a starting speed high enough for interplanetary travel). Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted July 17, 2012 Report Share Posted July 17, 2012 Re: More space news! I think this landing system is more about bringing it down in one piece. And this thing propably has equipment that doesn't likes impacts very well. You simply can't just aerobrake, rocketbrake or parachute it down. You have to use a multiple way appraoch to get something that mass down on mars safely (with a starting speed high enough for interplanetary travel). I understand THAT part; it's the crazy "hover on rockets while lowering the rover on a rope, then fly away and crash" bit that confuses me. This thing is already rocketbraking to a stop at the surface . . . and then burning MORE fuel to sit around in the air, and then yet MORE to fly away (and of course, it had to spend fuel to slow down that fuel). I try to assume that the professionals know what they're doing, but this design is making that kind of difficult for me. I'd love to read about the various options they considered and why they went with this one. Quote Link to comment Share on other sites More sharing options...
L. Marcus Posted July 18, 2012 Report Share Posted July 18, 2012 Re: More space news! Inflatable heatshield to be put to the test saturday. Quote Link to comment Share on other sites More sharing options...
Old Man Posted July 18, 2012 Report Share Posted July 18, 2012 Re: More space news! Quote Link to comment Share on other sites More sharing options...
Christopher Posted July 18, 2012 Report Share Posted July 18, 2012 Re: More space news! I understand THAT part; it's the crazy "hover on rockets while lowering the rover on a rope, then fly away and crash" bit that confuses me. This thing is already rocketbraking to a stop at the surface . . . and then burning MORE fuel to sit around in the air, and then yet MORE to fly away (and of course, it had to spend fuel to slow down that fuel). I try to assume that the professionals know what they're doing, but this design is making that kind of difficult for me. I'd love to read about the various options they considered and why they went with this one. Judging form wikipedia: http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Landing_system There is even a video where nasa en-detail explains why they dod it: And yes, they know it sounds crazy complicated. They also think it is crazy complicated. But it is simply the only way to get 900 KG of fragile, scientific material down to the surface of mars in one piece. Quote Link to comment Share on other sites More sharing options...
Zeropoint Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! That video explains WHAT they're doing, but doesn't go into any detail about WHY, and certainly doesn't mention any competing ideas that were passed over in preference of this one. Quote Link to comment Share on other sites More sharing options...
McCoy Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! That video explains WHAT they're doing' date=' but doesn't go into any detail about WHY, and certainly doesn't mention any competing ideas that were passed over in preference of this one.[/quote'] Yeah, they say they're doing the sky crane bit so they don't kick up a lot of dust which would settle back on the probe. My question is why not go rockets all the way to the surface, let the dust settle for a day, or even two, then open a dust-proof box and let the probe out? Quote Link to comment Share on other sites More sharing options...
AmadanNaBriona Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! From watching the video, my guess is that the final burn is carrying extra fuel in case of unexpected problems, so they want to get the disposable part that could go boom away from the expensive payload Quote Link to comment Share on other sites More sharing options...
McCoy Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! From watching the video' date=' my guess is that the final burn is carrying extra fuel in case of unexpected problems, so they want to get the disposable part that could go boom away from the expensive payload[/quote'] So get down safely, vent the O2 into the atmosphere. No boom. Quote Link to comment Share on other sites More sharing options...
Lawnmower Boy Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! Precocious galaxy. Lava planet potentially Earth's current smallest/nearest neighbour. Quote Link to comment Share on other sites More sharing options...
Cancer Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! So get down safely' date=' vent the O[sub']2[/sub] into the atmosphere. No boom. Most rocket fuels (other than the initial booster stage) use hypergolic fluids, things that explode on contact with a catalyst or the other component of the fuel mixture and require no igniter. Those tend to be nasty stuff. One of the Soviet/Russian boosters does use dinitrogen tetroxide and hydrazine for the initial stage, which makes for a really nasty chemical spill when one fails on launch. I can see why you wouldn't want that stuff on or near a newly deployed lander/rover. Quote Link to comment Share on other sites More sharing options...
Tom Carman Posted July 19, 2012 Report Share Posted July 19, 2012 Re: More space news! I believe that hypergolic propellants can generally be grouped into 3 categories: 1) corrosive; 2) carcinogenic; 3) both. Quote Link to comment Share on other sites More sharing options...
Old Man Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! Well, plus they can also explode. Anyway, I speculate that the reason they're not going rockets all the way down is that the propellant necessary would weigh more than the parachute does. At high atmospheric speeds a 'chute is going to produce more drag than the rockets would, anyway. Lots of things about rocket science and interplanetary travel are counterintuitive; I think this is just an unusually extreme example. Still, I can't help thinking there must be a better way. Autorotating propeller? Some kind of balloon? Shrug. Quote Link to comment Share on other sites More sharing options...
McCoy Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! Well, plus they can also explode. Anyway, I speculate that the reason they're not going rockets all the way down is that the propellant necessary would weigh more than the parachute does. At high atmospheric speeds a 'chute is going to produce more drag than the rockets would, anyway. Lots of things about rocket science and interplanetary travel are counterintuitive; I think this is just an unusually extreme example. Still, I can't help thinking there must be a better way. Autorotating propeller? Some kind of balloon? Shrug. The 'chute i understand. It's the sky crane that makes no sense. Hovering in place to lower the probe then takeing off for parts unknown has to take more fuel than landing by rocket. Quote Link to comment Share on other sites More sharing options...
Old Man Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! Does it? I wonder if it takes appreciably more fuel than hovering in place immediately prior to landing. I'm not sure if they wait until hover is established before lowering the rope, but I can't watch the vid again here in the office. Quote Link to comment Share on other sites More sharing options...
McCoy Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! "20 meters above the surface, it lowers the rover on a tether that is 21 feet long." [emphasis added] Anyone else having Climate Orbiter flashbacks? Quote Link to comment Share on other sites More sharing options...
Old Man Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! As if this landing had an appreciable chance of success to begin with. Quote Link to comment Share on other sites More sharing options...
AmadanNaBriona Posted July 20, 2012 Report Share Posted July 20, 2012 Re: More space news! "20 meters above the surface' date=' it lowers the rover on a tether that is 21 [b']feet[/b] long." [emphasis added] Anyone else having Climate Orbiter flashbacks? Quote Link to comment Share on other sites More sharing options...
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