Mars Science Laboratory (MSL) mission: NASA's Curiosity rover lands on Mars, 6th August 2012
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Crispy
The following psytrance is baṉned: All
"How do you autonomously land a tonne payload on the surface of Mars without subjecting it to excessive Gs, heat, chemicals or rough terrain?"
Limejuice
Well-Known Member
That's a pretty majestic question IMO.
Not being a boffin, does your clause 'not subjecting it to excessive Gs' include a possible massive deceleration event? See, as a non-scientist I would have given that its own special question, and linked it to something about preserving the Rover's no-claims bonus.
I really hope it works because the answer to the engineering problems is inbloodygenious. Plus, what's not to love about a one-tonne space car that shoots lasers and hunts for life?
2hats
Dust.
See Viking? Each fully fuelled lander (with the flight shell: aeroshell plus heat shield plus bioshield) weighed in at over a tonne at the top of the martian atmosphere. The final surface package of lander minus spent fuel and flight shell clocked in at about 0.6 tonne.
Though the differences here (in mission design) were to minimise the mass that was to be driven around the surface of the planet, the Viking landers being static, of course, and the dust contamination of the rover itself. Quite what they are expecting to happen in dust storm season, I don't know. Perhaps modelling suggests descent stage exhaust gas driven dust particles would be accelerated to higher velocities than those expected from a natural martian dust storm and/or the descent motors would drive dust up into the immediate atmosphere from much deeper below the martian surface than would naturally occur (and thus create misleading sample profiles for some time after landing) - so they went for the sky crane approach.
Possibly they wanted to shave some weight off by not having to rely on really sturdy landing legs too. The Viking struts/pads were designed to withstand a landing of up to 30g but in the end experienced around only a handful of g. Of course they knew next to nothing about the state and dynamics of the martian atmosphere back then. The gas models used for understanding super and hypersonic flow regimes were less sophisticated too (so they wanted to design in for a big margin of error). A lot of work was done in the 80's to refine these based on data gathered from eg shuttle re-entrys (STS1 exhibited worrying control issues because they started off using a model which missed out on a lot of the important gas physics). There are still major issues though - the regime for an Earth-like atmosphere is quite well understood now. Mars however is largely carbon dioxide and radiative heat behaviour is significantly different. So it's a work in progress...
2hats
Dust.
I notice everything is in metric this time 
The hover crane is not unlike the Viking lander stage in many respects (lots of Viking technology is being recycled/built upon). I think, if everything is on target, key points in the descent profile are clearly the lowering of the rover to the surface (retrorockets based on those used by Viking) but also the supersonic parachute deploy (actually scaled up from Viking).
The parachute has to deploy at Mach 2 and has to quickly decelerate the vehicle to sub Mach 1.4 to try and avoid wild oscillations that will (have the effect of trying to) repeatedly open and close the 'chute envelope (and so dramatically reduce its efficacy). This is one of the most dangerous phases of the descent and one of the key problems with landing on Mars: there's a very narrow window of opportunity in terms of altitude and velocity because the Martian atmosphere is so thin meaning aero-braking isn't as effective so one has to deploy 'chutes at supersonic speeds. Obviously too early and your 'chute fails plus your downrange error can grow, too late and you risk ploughing into the surface. They're also making it harder for themselves as the ideal target touchdown location is about 1km above the (reference) Martian surface (areoid).
The early stage of the entry is interesting too. For the first time they will be flying a guided approach at hypersonic speeds, generating lift at very high speed in the upper atmosphere to both linger there in order to gain the altitude they seek at touchdown, and to minimise positional error at 'chute deploy (some tricks borrowed from Apollo command module entry profiles). The vehicle trajectory even climbs at one point. All previous entries at Mars have been ballistic, except Viking which was a full lift up trajectory (no guidance) in order to reach a high altitude landing site (but with corresponding loss of accuracy - they just wanted to get there and probably wanted to bleed off as much energy as high as possible to play safe anyway - 'chute deploy was at around Mach 1).
Then, of course, the backshell and heatshield have to separate cleanly! Not only does my mind boggle at all the opportunities for it to go wrong but it makes the Viking lander successes seem almost miraculous given what little was known, the approximations made at the time and limits of computer modelling in the mid 70's. Little wonder those landers were built like tanks.
The hover crane is not unlike the Viking lander stage in many respects (lots of Viking technology is being recycled/built upon). I think, if everything is on target, key points in the descent profile are clearly the lowering of the rover to the surface (retrorockets based on those used by Viking) but also the supersonic parachute deploy (actually scaled up from Viking).
The parachute has to deploy at Mach 2 and has to quickly decelerate the vehicle to sub Mach 1.4 to try and avoid wild oscillations that will (have the effect of trying to) repeatedly open and close the 'chute envelope (and so dramatically reduce its efficacy). This is one of the most dangerous phases of the descent and one of the key problems with landing on Mars: there's a very narrow window of opportunity in terms of altitude and velocity because the Martian atmosphere is so thin meaning aero-braking isn't as effective so one has to deploy 'chutes at supersonic speeds. Obviously too early and your 'chute fails plus your downrange error can grow, too late and you risk ploughing into the surface. They're also making it harder for themselves as the ideal target touchdown location is about 1km above the (reference) Martian surface (areoid).
The early stage of the entry is interesting too. For the first time they will be flying a guided approach at hypersonic speeds, generating lift at very high speed in the upper atmosphere to both linger there in order to gain the altitude they seek at touchdown, and to minimise positional error at 'chute deploy (some tricks borrowed from Apollo command module entry profiles). The vehicle trajectory even climbs at one point. All previous entries at Mars have been ballistic, except Viking which was a full lift up trajectory (no guidance) in order to reach a high altitude landing site (but with corresponding loss of accuracy - they just wanted to get there and probably wanted to bleed off as much energy as high as possible to play safe anyway - 'chute deploy was at around Mach 1).
Then, of course, the backshell and heatshield have to separate cleanly! Not only does my mind boggle at all the opportunities for it to go wrong but it makes the Viking lander successes seem almost miraculous given what little was known, the approximations made at the time and limits of computer modelling in the mid 70's. Little wonder those landers were built like tanks.
sleaterkinney
Well-Known Member
I might start a poll
sleaterkinney
Well-Known Member
It's got the lot, Guided entry, Parachute opening at Mach 2, Powered descent using rockets then the rover lowered by a sky crane.
http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Landing
Will it work?
http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Landing
Will it work?
Pickman's model
Starry Wisdom
Like the one where they confused metrick and imperial
TitanSound
Mr Beardy Drummer
After watching the video of the landing sequence, yes. It HAS to just so we can all marvel at men and women in sheds being bonkers.
Crispy
The following psytrance is baṉned: All
There have been paper studies after paper studies, but no real money or commitment to a plan. The schedule that most planned visits take is 7.5 months on the voyage out, a 15 month stay on the surface and another 7.5 months to come home. This takes advantage of earth-mars alignment every two years.
marty21
One on one? You're crazy.
hell of a trip - there have been people in the space station for long periods - a year+ ?
Crispy
The following psytrance is baṉned: All
Yeah, longest stay in space is (wiki...) 437 days. ISS crew rotations are up to 6 months. There have been simulated mars missions on earth. This was the latest: http://www.bbc.co.uk/news/science-environment-15574646 (but this is a much shorter trip. In the real world, a 500 day mission would be a high-energy flight and more expensive)
weltweit
Well-Known Member
I am kind of in the same boat.
It seems very complicated and with so many things that have to go right there are just more things that could go wrong.
I am going to cross my fingers and hope everything goes to plan.
2hats
Dust.
How do you land humans on Mars and still meet your obligations under the UN treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space/COSPAR Planetary Protection Policy? Not only in avoiding the accidental introduction of Earth microbes to Mars but the possibility of returning Martian life to Earth. You can't clean a human to planetary protection standards. Even if it is possible to avoid cross-contamination (at some suitably ultra-low level of risk), it will significantly drive the cost of a mission up. Wasn't much of an issue for the Moon but will be for Mars...
dylans
overlord of all acorns
Did they spell metric wrong as well? God, you'd think scientists would be able to spell a simple word. NASA's standards are slipping
Pickman's model
Starry Wisdom
you thick fuck. in metrick the rate of gravitational acceleration in m/s2 is 9.80665; in imperial it is about 32 f/s2. if you fuck it up and get confused then your fucking expensive bauble is going to whack into the planet's surface at an ungodly speed.
dylans
overlord of all acorns
in metric
2hats
Dust.
Wrong planet, and besides, you'd miss.
DotCommunist
So many particulars. So many questions.
I'd like to think whatsis face, cornishman with the huge 'burns will be excited to see success and not thinking 'you bastards! we were so close!'. Man that was a downer on christmas day.
dylans
overlord of all acorns
Is there anything live online on monday morning? Outside the natural history museum's event I mean. I would like to wake my kid up for the landing if there is anything to watch that is.
If I was in London I would have liked to have taken him to the NHM event but at 6.00 am we can't get there from brum. (sold out now anyway)
If I was in London I would have liked to have taken him to the NHM event but at 6.00 am we can't get there from brum. (sold out now anyway)
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