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Simulation of the Mars Science Laboratory Sky Crane
Posted by
kdawson
on Mon Oct 20, 2008 09:24 PM
from the rocket-science dept.
from the rocket-science dept.
An anonymous reader points us to Gizmodo for a fascinating video of NASA's Sky Crane. "When I read that the UFO-looking Mars Science Laboratory's aeroshell would use a floating crane — called Sky Crane by NASA — to softly land the rover on Mars, I couldn't believe it. Now, watching this hyper-realistic NASA simulation, I still can't believe how the whole thing works. I don't know about you, but the whole operation mesmerizes me to no end."
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Submission: How the Mars Science Laboratory Sky Crane Works by Anonymous Coward
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Cool Movie - but bad idea! (Score:5, Interesting)
That is so complicated. The "beach ball" idea from the two current rovers was much better.
Maybe if the Sky Crane was a ballon system so it can float around Mars would make this better. But still way too complicated.
Re:Cool Movie - but bad idea! (Score:5, Informative)
I think the idea is that as you get more massive that doesn't work as well anymore. The weight of the airbags becomes untenable... I haven't looked at the math in few years, so unfortunately I can't be more specific.
Mars is one of the hardest places to land because its atmosphere is so wispy; on Earth some simple parachutes and a well-shaped capsule do the trick. On Venus the atmosphere is so thick anything you drop in will happily land softly as long as it doesn't melt. The moon and other such places you really only have the landing rocket option, which can be heavy but not particularly complicated.
On Mars though, the atmosphere is too thin to allow the capsule to slow it down to subsonic speeds on its own, meaning supersonic chutes are necessary if you want to use the atmosphere to slow you down. If you want to land with a rocket, you run into issues of trying to light an engine with supersonic flow going into the nozzle; trying to light it and flip around I imagine introduces some pretty wretched dynamic and structural problems. That tends to mean a series of parachutes including custom Mach 2 or Mach 3 chutes that would never be needed on Earth, or in this case using an aeroshell as well. Even then, you're still going too fast, so you need to slow down more. As suggested before, the airbags have worked in the past but don't scale well with higher mass vehicles. Thus you really need some kind of rocket (that ignite at subsonic speed); I'm not sure why a sky crane works better than some other system with rockets, I'd imagine its the easiest method of separation and also allows you to use less fuel since the crane itself doesn't have to slow down to a safe speed (i.e. release it down and reel it back up to reduce landing speed.)
Also, they had this option out there three years ago when I worked on a Mars mission for a class, so it's been out there a while and is probably as well developed as a non-tested system can be.
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Re:Cool Movie - but bad idea! (Score:5, Interesting)
I'm on the project, and I understand all the reasons why we're doing it this way, but for what it's worth, I think it's as bat-shit insane as the rest of you. One thing no one can argue, though: it's incredibly cool.
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Re: (Score:3, Informative)
You can see the pedigree of the concept. The airbag system used a brutal retro-rocket on the teather milliseconds before impact to slow the airbag-lander from smush speed to bounce speed.
This is similar. The retro rocket is far more gentle and precise but basically we have a last-second retro rocket on a tether dropping the lander onto the surface.
I presume tradeoff studies were done to find the optimum balance between the amount of crane hover precision and winch control precision for a giving touchdown sp
Re:Cool Movie - but bad idea! (Score:5, Interesting)
Or you need to send down a bunch of pieces which assemble themselves into a larger vehicle.
"Mars Mission. The Beginning of Megatron"
(queue theme music and intro credits...)
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Re: (Score:3, Interesting)
Re:Cool Movie - but bad idea! (Score:4, Interesting)
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Re: (Score:3, Informative)
The cables allow for some leeway in how hard you can hit the ground and still have a functioning rover. If you come in too fast with a single piece of equipment, the whole thing goes crunch. The rockets and ground acquisition sensors are good, but not perfect.
With the rover on the end of the bridle, this decouples the weight of the scientific payload from the weight of the support equipment needed to ensure a soft landing of the payload. Once the thing is on the ground, you don't need any of the support equ
Re: (Score:3, Interesting)
Indeed, you are right about Spirit and Opportunity.. I almost forgot.
I am fairly confident that NASA has made the correct choice about the EDL method, but I really wonder if they are going to be ready in 2009. I haven't seen any photo's of the MSL construction, so I don't even know if they have already started building it or not. Or are they planning to do construction in just a few months? I know the science instruments are all (nearly) finished, but I hardly hear news about the rest of the hardware.
Re: (Score:2)
Awesome post. I'm fairly ignorant on the whole space topic - I researched briefly what we have to gain from actual visits to other planets in our system and compared it to the cost of actually sending craft to visit right before deciding that it made the most sense to develop all the necessary exploratory technology but not implement it for a number of years.
But that will in no way stop me from reiterating the basics of your post the next time I'm discussing extraterrestrial exploration in an effort to sou
Re: (Score:3, Informative)
Airbags don't work on something as big as the MSL rover. It's that simple.
MSL weight: 1 ton (Score:2)
You should point out it weights 1984 pounds... just shy of one ton. It makes the landing system a lot more intuitive.
WTF: Hyper-realistic? (Score:5, Funny)
Almost realistic: the simulation approaches what the same inputs would do to the real system.
Realistic: the simulation behaves the same way as the real system.
Hyper-realistic: the simulation is better at realism that they real system?
What next, über-realistic? Or is profit next?
Re: (Score:2)
Profit is next actually... I have no idea why the story submitter can't believe this. There are some awesome engineering feats that our species has accomplished here on earth. UAVs are awesome. The Thames flood damn is awesome. ISS is awesome. Comms satellites are awesome. Heavy lift helicopters are awesome. VTO spaceships and fighter jets are awesome. Autonomous gliders launched from weather balloons in near space are awesome. Why is it so difficult to believe this Mars mission? The Lunar lander did simila
Re: (Score:2)
Why is it so difficult to believe this Mars mission? The Lunar lander did similar feats. It's even possible to test this with modified equipment right here on earth.
I agree almost 100%. But why must we test the awesome tech we're developing for space exploration in space? It's awesome engineering with a good cause, but we can do the same things here (more or less) at a much reduced cost. I'm convinced that the difference in cost between deploying locally and deploying extraterritorially must exceed any benefits we'll receive from making actual landings. I know slashdot is full of folks who want robots/astronauts actually tromping around, but what's the actual cost/
Re: (Score:2)
As someone who tinkers around with robots, perhaps I can shed some light on the question you ask:
I know slashdot is full of folks who want robots/astronauts actually tromping around, but what's the actual cost/benefit?
There is much to be learned by building robots galore. Intelligent machines can make many tasks much more cost effecting in the 'long run' but will cost much to start, and seem silly for a long while. I say in the long run because what we think we know today is merely the tip of an iceberg. A couple of benefits of robotics engineering experience are: iRobot's vacuum robot and bomb disposal robots for the militar
Re: (Score:2)
Perhaps I did miss the point? I hope I didn't.
What we don't know is exactly what we'll find and we are kind of running out of time and discoveries on this planet. Time to explore the next great frontier... surface exploration of other solar planets.
I don't think that the great explorers of Earth waited for the very best high tech gear that was possible before they went exploring to find new lands and the poles etc. Whether that seems wise or not, you really will have trouble inventing new and groundbreaking diving gear without getting in the water. What you can discover in your backyard pool is good, but it's not quite the same as experimenting at 275 meters.
Yes, some flight equipment can be tested in Eart
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Re: (Score:2)
No, it really isn't. Fast cuts are ok, but if the shaking isn't caused by my own head, I feel like I'm being lead around. It's not very comfortable. I'm talking to you Ronald D. Moore.
Re: (Score:2)
Hey! You spelled über correctly! Don't tell me you can pronounce it too? ;)
Another slashdown? (Score:2)
Why not use what works? (Score:2, Insightful)
Why does NASA have to spend money on new untested methods? If the old baloon method worked well for two previous rovers, why not use it again? It is hard to beat a 100% success rate. Does anyone know why they want to use this over other methods?
The sysadmin in me says: The more moving parts, the greater the chance something will break.
Re:Why not use what works? (Score:5, Informative)
Trebuchet's don't scale very well. AFAIR, neither did the beach ball. This thing is lots bigger and heavier.
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Re: (Score:2)
And I can't help but think about all that extra weight that needs to be launched and is useless once the rover has landed, not to mention the cost of the sky crane itself.
Re: (Score:3, Insightful)
True, but how much does a triangular pyramid covered with self-inflating balloons weigh? Plus it had the hinged ramps that would fold down, so the old landing method wasn't completely without complex stuff.
Re:Why not use what works? (Score:5, Informative)
It has to do with mass, the MSL rover, at 900 kg, is much too heavy to land using the airbag methods that landed the 180 kg Spirit and Opportunity rovers. To give a sense of scale, the MSL rover is the size of a minivan, while Spirit and Opportunity are the size of small riding mowers. See:
http://en.wikipedia.org/wiki/Image:Mars_Science_Laboratory_empty_chassis.jpg
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Re: (Score:2)
I was just going to use that example but state that therefore it obviously DOES work for much larger payloads!
And (Score:5, Funny)
We've got to flex some of our engineering muscle in front of our Martian friends so they will less inclined to invade us. In this light, clearly this > bouncing beach ball delivery.
Maybe have an external speaker system that blasts Ride of the Valkyries during descent, too.
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preposterous (Score:2)
The skycrane seemed preposterous originally & still does. Having said that, autonomous helicopters are pretty germane nowadays & everyone knows about Stanford's aerobatic helicopter so maybe it's not so crazy anymore.
Not entirely practical (Score:2, Informative)
Re:Not entirely practical (Score:5, Informative)
So what? This thing is much larger than anything landed anywhere before, with the exception of the manned LEM.
The Apollo capsule had an atmosphere much thicker (as in height) and much thicker (as in density) than the Mars landers have available. The Apollo LEM could use rocket braking because of the Moon's low gravity.
Mars is a stone cold bitch to land on because the atmosphere is too thin to completely rely on parachutes, and Mars' gravity is too high to rely completely on rockets.
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Re: (Score:2)
Apollo had people in control to turn off the rockets so they didn't take off again (well not "land" in the first place). The lander had to hit 0 speed at some distance from the ground, and then stop firing the thruster.
The "lower by rope" system has the advantage off a much much larger range heights for that 0 speed point. It doesn't have to do a thruster based landing it just to get within [length of the rope] from the ground before it starts going back up.
This seems a good solution to me - not as cool as
what I don't understand (Score:2, Interesting)
We seem to be able to get to mars better, the Russians do land landings better than us.
why not have them design and build the landing mechanism, and we just fly it there?
Half life (Score:2)
Did anyone else get a Black Mesa vibe from the wind sound effect at the end of the video?
Also, would wind sound like that in an atmosphere like mars'?
-b
simulation? (Score:2)
I don't think that word means what you think it does.
No solar panels? (Score:2)
Re:No solar panels? (Score:5, Informative)
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Story? (Score:2)
Who is tagging every post on /. as story and why? I know this is off-topic but I'm so curious. Oh and by the way, this [youtube.com] is how to find life on Mars.
Is that you Mal? (Score:2)
Was it just me or did anyone else expect to see Jayne suspended from the bottom of that rover?
Landing on Mars is hard (Score:5, Informative)
The problem with soft-landing heavy objects on Mars is that there's not enough atmosphere for aerobraking and parachutes to do the job, so the approaches used for Earth re-entry won't work. There's too much gravity for landing on rockets. as with lunar landers, without most of the payload being landing fuel. The problem gets harder as the mass goes up. This was realized only about five years ago, to the embarrassment of some within NASA. So there are now various complicated hybrid schemes, like this.
The scheme with the cables does not look promising. Unlike Luna, Mars has winds and weather. This looks like one of the student lander designs from NASA's high school curriculum. [thinkquest.org]
One bad feature of this design is that the actual landing forces have to be taken by the rover's suspension. Previous designs had the rover inside the landing module, not underneath it. That approach uses crushable components (air bags, crushable blocks, collapsible legs, etc.) to cushion the landing. With this "flying crane" approach, the autopilot has to do a really, really smooth landing or the rover will be broken.
Anyone know? Audio recordings of Mars? (Score:2)
Watching that and hearing the wind blow made me wonder if there have been any audio recordings taken on Mars? I'm sure it would be boring as hell but still that would be really cool for the first minute or so... you know, to listen to Mars (well whatever you can hear in the 1km radius around the rover anyways).
Re:Anyone know? Audio recordings of Mars? (Score:4, Informative)
Just a little longer...
http://www.space.com/businesstechnology/081001-tw-phoenix-microphone.html [space.com]
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Really Poor Concept (Score:3, Informative)
The whole operation is horrendously complicated, with dozens of potential failures at each point, and no realistic means of allowing for such failures. Every step would have to function perfectly, or we've just sent another multi-billion paperweight to a dead planet.
Whatever happened to KISS?
The engineer who proposed this really needs to look into alternate fields of employment. I suggest Fecal Matter Relocation.
Why the crane part? (Score:3, Insightful)
I'm OK with everything up until they start winching the lander down under the crane. How is that better than sitting the rover on top of the retro rocket module, hovering, then landing, and having the rover drive off the top of the lander?
The number of failures that could happen to the winching system seems nuts; a line might not lower, or at the wrong speed, or a line could tangle, or a side to side oscillation while descending, or a cable not disconnect, and if any of these go wrong, you have no time to fix it.
Re: (Score:3, Insightful)
I think some one figured out that a winch is ligher weight then a folding ramp. You have to remember that this next rover is the size of a car. Think about how you'd make a folding ramp that would allow a car to drive off a lander. The winch is very compact and light
A ramp carries a risk too. It would need a set of motoers and gears to make it unfold. If there is anything in spacecraft that will fail it is those kinds of moving parts and they depand on batteries that have beenin space for a year.
The wi
Re: (Score:3, Informative)
That is the reason for the skycrane. If the air were as dense, a standard parachute landing would be all that is required. The problem is an inability to decelerate to a stop without the sudden stop part. I believe that gliders are also out of the question due to atmospheric conditions. This is a compromise of all known possible options. One that will land the heavier weight, and perhaps give them much greater accuracy in choosing a landing spot... With the speed of the rover hitting the right spot first tr
Re:turtle on its back (Score:4, Interesting)
The video showed the lander dropping straight down on the wheels without any side motion at all. This seems unlikely to me. The rover would be swinging like my dick on those cables unless there were some thrusters used to stop any swinging motion.
Other than that, it's a pretty neat idea, ESPECIALLY for a spacecraft which is not a rover. A rover can move out of the landing zone, but a stationary spacecraft cannot. It would be sitting on soil which has traces of hydrazine from the landing rockets - but this system would avoid that problem.
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Re: (Score:2)
The atmosphere is way way too thin for that to be practical. It should be pretty obvious that if there was an easier and more reliable method of landing a 900kg rover, NASA would have gone with that.
NASA engineers are somewhat of an intelligent bunch methinks...
Re:This is needlessly complicated and HERE is why: (Score:5, Insightful)
Even in their most recent plan for this Mars descent, their first mode of descent is to drop the module like a stone, using elaborate and expensive heat shielding to protect the even-more-expensive gear. But maybe -- just maybe -- they could take a lesson from Spaceship One and just take their time getting this thing down to the ground.
Sorry - but you have no clue. Mars' atmosphere at the surface has about 1% of the Earth's density, making something like aerodynamic flying impossible.
There simply isn't any other way than "dropping like a stone" - even on their parachutes, the rovers did exactly that. Those parachutes were supersonic, and their
main purpose was trajectory stabilization (although they did of course contribute to the braking).
Go read this article [universetoday.com] already linked above for a well written explanation about why
landing on Mars is actually very hard and cannot in any way be compared to landing on Earth.
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