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A couple of people from the JPL team talked about why they used the sky crane rather than other methods and they mentioned that the amount of dust caused by usi

by amock 14y ago

A couple of people from the JPL team talked about why they used the sky crane rather than other methods and they mentioned that the amount of dust caused by using rockets all the way down would cause issues for the rover. So it seems like some dust is ok but too much would cause enough problems that the sky crane is worth it.

prawn 14y ago
Might they want to minimise interference with the layers of dust/dirt on the ground, where possible? Probably not - maybe that's akin to explorers worrying about longboats pushing into the sand when they reached a beach...
- simcop2387 14y ago
  I think it's mostly that they wanted to minimize any clouds from causing it to think it's closer to the ground than it is, and to keep the instruments from getting covered/clogged on landing.
- amock 14y ago
  They plan on driving a significant distance, so I don't think they're too worried about contamination of the landing site. I think the real issue is that they have many sensitive instruments and protecting against very small high velocity particles is difficult.
  - fjarlq 14y ago
    Andrew Bingham, the engineer of the hazcam dust covers, explains in detail: http://forum.nasaspaceflight.com/index.php?topic=29612.msg938852#msg938852 http://forum.nasaspaceflight.com/index.php?topic=29612.msg93... "These dust covers were one of the last things added to the rover. The MSL HazCams are build-to-print copies of the MER HazCams. On MER, the cameras were protected inside the lander, and in over 10 rover-years on the ground they haven't seen dust building up enough to be worrysome. The Skycrane system was supposed to reduce the plume ground pressure during landing to the point where dust wouldn't be an issue for MSL." "But after Phoenix landed and everyone saw the pictures of pebbles ON TOP OF the pads on the bottom of the lander legs, and the legs themselves coated with a sticky looking layer of dust, some concerned folks looked at the issue more closely. It turned out there is a core flow in the Mars Lander Engines on the descent stage that stays strong all the way to the surface, even hanging at the end of the skycrane. And that can kick up a lot of dust+reaction products during the skycrane maneuver, some of which would go back towards the rover. There was a review of hardware in danger of being coated with "sticky" dust; everything was determined to be dust tolerant EXCEPT the HazCams."
jebblue 14y ago
They didn't need a sky crane for the Viking landings. http://en.wikipedia.org/wiki/Viking_program http://en.wikipedia.org/wiki/Viking_program
- simonh 14y ago
  But then the Viking landers had a full-up launch mass of 657 kg including full propellant tanks for the landing rockets. Curiosity is 900kg just for the rover. If you added in landing rockets and their fuel as well it would be well over double the mass of a Viking lander, so the force of the landing rockets and therefore dust agitation would be commensurately greater. Another advantage of a skycrane is that the rockets need to angled away from the payload anyway, and so the point where the plumes hit the surface is some distance from the payload, whereas rockets in the payload itself would hit the ground immediately below or to the side of it. Much closer.

by amock 14y ago

prawn 14y ago

Might they want to minimise interference with the layers of dust/dirt on the ground, where possible? Probably not - maybe that's akin to explorers worrying about longboats pushing into the sand when they reached a beach...

simcop2387 14y ago
I think it's mostly that they wanted to minimize any clouds from causing it to think it's closer to the ground than it is, and to keep the instruments from getting covered/clogged on landing.
amock 14y ago
They plan on driving a significant distance, so I don't think they're too worried about contamination of the landing site. I think the real issue is that they have many sensitive instruments and protecting against very small high velocity particles is difficult.
- fjarlq 14y ago
  Andrew Bingham, the engineer of the hazcam dust covers, explains in detail: http://forum.nasaspaceflight.com/index.php?topic=29612.msg938852#msg938852 http://forum.nasaspaceflight.com/index.php?topic=29612.msg93... "These dust covers were one of the last things added to the rover. The MSL HazCams are build-to-print copies of the MER HazCams. On MER, the cameras were protected inside the lander, and in over 10 rover-years on the ground they haven't seen dust building up enough to be worrysome. The Skycrane system was supposed to reduce the plume ground pressure during landing to the point where dust wouldn't be an issue for MSL." "But after Phoenix landed and everyone saw the pictures of pebbles ON TOP OF the pads on the bottom of the lander legs, and the legs themselves coated with a sticky looking layer of dust, some concerned folks looked at the issue more closely. It turned out there is a core flow in the Mars Lander Engines on the descent stage that stays strong all the way to the surface, even hanging at the end of the skycrane. And that can kick up a lot of dust+reaction products during the skycrane maneuver, some of which would go back towards the rover. There was a review of hardware in danger of being coated with "sticky" dust; everything was determined to be dust tolerant EXCEPT the HazCams."

jebblue 14y ago

They didn't need a sky crane for the Viking landings. http://en.wikipedia.org/wiki/Viking_program http://en.wikipedia.org/wiki/Viking_program

simonh 14y ago
But then the Viking landers had a full-up launch mass of 657 kg including full propellant tanks for the landing rockets. Curiosity is 900kg just for the rover. If you added in landing rockets and their fuel as well it would be well over double the mass of a Viking lander, so the force of the landing rockets and therefore dust agitation would be commensurately greater. Another advantage of a skycrane is that the rockets need to angled away from the payload anyway, and so the point where the plumes hit the surface is some distance from the payload, whereas rockets in the payload itself would hit the ground immediately below or to the side of it. Much closer.