NASA Considers Autonomous Martian Helicopter To Augment Future Rovers 83
A reader writes with this story at the Verge about an approach being considered by NASA to overcome some of the difficulties in moving a wheeled or multi-legged ground vehicle around the surface of Mars, which has proven to be a difficult task. Rover teams still have a tough time with the Martian surface even though they're flush with terrestrial data. The alien surface is uneven, and ridges and valleys make navigating the terrain difficult. The newest solution proposed by JPL is the Mars Helicopter, an autonomous drone that could 'triple the distances that Mars rovers can drive in a Martian day,' according to NASA. The helicopter would fly ahead of a rover when its view is blocked and send Earth-bound engineers the right data to plan the rover's route.
Lift? (Score:5, Interesting)
Re:Lift? (Score:4, Interesting)
BIG rotors made of aerogel.
But I agree, what NASA needs is God's Little Toy from Pattern Recognition (W. Gibson, I think it's that book).
Basically a blimp with a camera. It could even be tethered.
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A blimp would make sense andÃ"given those Martian windsÃ"it's need to be tethered to the rover or it'd soon end up drifting over the other side of Mars. Rotors could be used to position the blimp directionally so good pictures could be taken.
Just keep in mind that gas leakage would probably give the blimp a limited lifespan unless there were some way to reel it back in to refill the hydrogen or helium gas inside.
It might also make sense to release a blimp like that to drift around, particularly if
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A tethered blimp isn't a scouting drone, it's a periscope. And given those winds an untethered blimp would likely never see the rover again, so still no good for scouting.
It might be interesting as an independent, largely unsteerable, low-altitude survey drone to study wind patterns and look for interesting target regions for the next mission, but at that point we've changed the mission parameters so drastically that it's no longer relevant to the original discussion
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It's still a periscope - you can use it to see over hills, but not to scout ahead.
You'll also get piss-poor lift with a hot air balloon - Martian air density is only 0.02kg/m^3, compared to the 1.2+kg/m^3 on Earth. The colder temperatures will help somewhat, offering a better density gradient with temperature, but you're still talking about a lift of maybe 20% of the displaced air mass, versus 90% for a helium balloon. Even with helium, a balloon 2m across could lift under 80g, minus it's own weight. A ho
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A helium balloon on Mars would only carry about 10 g of per cubic meter. A hot air balloon would carry far less. (given 273 K ambient temperature and 373 K balloon temperature...rather difficult to maintain with the available power...around 3 g/m^3)
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No, a balloon is not so easy. With 1% the atmosphere, you need a 100X bigger balloon than on earth. And mind those winds.
But an aerofoil / rotor has advantages - first it only needs 40% of the lift (lower gravity) .
More significantly, while lift is linear to air density, lower pressure also means reduced drag on the rotor, allowing faster rotation and/or bigger rotors (lift proportional to area).
Drag formula is similar to lift, so with the same power, you can spin the rotor 10x faster to get the same drag a
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BIG rotors made of aerogel.
Aerogel is really fragile stuff. I bought a few pieces of it for my daughter's science project. It looks like a little cube of smoke, and you can barely feel it sitting on the palm of your hand. But even with reasonable careful handling, the corners broke off, and some of the pieces snapped in half. It is not something you could use to build a rotor that will fly more than once.
According to TFV, they make the helicopter work by spinning the rotor really fast (2400 RPM), keeping it really light, and only
Re: Lift? (Score:2)
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Where did you get ahold of aerogel at?
eBay.
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Well, the prototypes might be using plastic for ease-of-revision, but my guess would be molded carbon fiber, at least for later prototypes and the final product - I don't think there's anything competitive in terms of durability and strength-to-weight ratio, and the cost is peanuts by NASA budget standards. Hell, once shipping costs to Mars are factored in it's probably cheaper.
Hmm, come to think of it, I wonder why we see so much metal used in the current rovers.
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A blimp would suffer the same problem, but even worse. A cubic meter of unpressurized helium will only lift about 10 grams at the surface, and there's nothing you can do about that. The helicopter could at least spin its blades faster, though there's the problem of a power source...
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the problem of a power source...
Much less power will be needed to spin large blades. The thin Martian atmosphere will produce much less parasitic drag.
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Less drag for the same blade velocity, but less lift in the same proportion, and what matters is lift to drag ratio, which isn't as good at high speeds (and a Martian helicopter would likely require a supersonic rotor).
And fundamentally, a hovering Mars drone is constantly accelerating by 3.7 m/s^2 by accelerating the nearby atmosphere downward. This is energy intensive, entirely apart from the drag losses. The thinner the surrounding atmosphere, the lower the mass flow rate and higher the velocity you have
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Weather balloons are quite large and delicate. You need something that can be deployed from a rover without any assistance, and which can survive being tethered to that rover while fully inflated...recall that weather balloons are barely inflated at launch because they expand during ascent, when they actually reach those high altitudes they are far larger than they appear on the ground. We're talking tens of meters across, a hundred cubic meters per kg of payload and balloon, made out of a fragile plastic f
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Actually it would lift closer to 20 grams - CO2 is denser at the same pressure, and Mars' atmosphere has a density of 0.020kg/m^3 at the surface.
Your point remains though, your average rubber party balloon is 12g, and would be stretched pretty thin if inflated to the 1.5m diameter needed to displace 1m^3 of air.
Which is the reason blimps tend to be built large - the lift-to-surface-area ratio increases linearly with size: 2x the (linear) size requires 4x the skin and gives 8x the lift. 10x the size needs 10
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I *was* using the density of CO2...which at 273 K and 600 Pa is about 0.012 kg/m^3. It might reach 0.020 kg/m^3 when it's coldest, but it sounds high for a typical surface density.
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I'm using data from NASA's website - theory be damned, I'll trust their numbers.
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You mean like this [nasa.gov]?
Granted, it's actually targeted for Titan, but yeah...
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Titan's atmosphere has about 1.5 times the surface pressure of Earth, and the atmosphere is even denser due to the cryogenic temperatures (about 20 K lower, less than the difference between your freezer and room temperature, and it'd start raining nitrogen). The only place in the solar system better for balloons is Venus, they're barely possible on Mars.
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The only place in the solar system better for balloons is Venus
You forgot the gas giants.
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Didn't forget them, they're just not very good for ballooning. With their hydrogen-helium atmospheres, the only way to get a reasonable amount of buoyant lift is by heating your lift gas, and the low density of those gases means even that gives little lift at a given pressure. Better than Mars, but worse than Earth.
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There is a lot more Methane in the two smaller giant planets.
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1.5% in Neptune and 2.3% in Uranus, not enough to matter for buoyant craft.
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It's going to be a funny-looking quadcopter with a thousand-foot rotor span. Good luck getting that into a spacecraft shell and then assembled after landing.
Re:Lift? (Score:5, Insightful)
Atmospheric pressure on Mars is 1% that of Earth. How're you going to get any lift?
Gee I dunno .. why not watch TFV and see what the experts say. You know .. the video where they talk about needed to spin the blades at 2400 rpm, and shows the drone mockups being tested in a chamber that they pump down to Mars conditions.
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My big question is why just have one when you can have a swarm??
Give those martians something to *really be scared about... :-)
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Not sufficient to compensate for the lack of "air", but the gravity is about 38% of that on earth. It does help a bit.
Bert
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Even compensating for gravity difference the air density on mars would be similar to flying on earth at over 35,000ft.
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Not a big deal, ordinary helicopters can (barely) do that.
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Care to cite any evidence of that?
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Care to cite any evidence of that?
Care to explain why you had to ask? [wikipedia.org]
Google is your friend. (Sometimes, anyway.) So is Wikipedia.
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Problem: the original poster got their units messed up, and the surface of Mars has pressure equivalent to about 35000 meters, not feet. That's about 115 thousand feet. That's nearly 3 times the "altitude without payload" figure listed there.
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Thanks for correcting me.
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much weaker gravity as well
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Atmospheric pressure on Mars is 1% that of Earth. How're you going to get any lift?
The same way turbines, propellers and aircraft function at high altitudes on earth. Combination of larger rotors, increased rotor speed and/or angle of attack.
Re:Lift? (Score:4, Insightful)
Atmospheric pressure on Mars is 1% that of Earth. How're you going to get any lift?
if you rotate the blades 10x as fast as you do on Earth, you'll get the same lift.
That said, gravity on Mars is 1/3rd as much as Earth, so you only need 1/3rd the lift. So rotating the blades at 6x the rate you'd rotate them on Earth would be sufficient.
Or you could go with much larger blades.
Either way ... it's doable. It would require more power than it would on Earth, but it's certainly doable.
This is a pretty interesting discussion of how we'd fly on Mars [x-plane.com], done in the context of the X-Plane simulator. It's written with fixed wing planes in mind rather than helicopters, but most of it still applies.
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if you rotate the blades 10x as fast as you do on Earth, you'll get the same lift.
Sorry you are off by a factor of 10. Ten time faster rotation means ten times the lift not 100 times.
That said, gravity on Mars is 1/3rd as much as Earth, so you only need 1/3rd the lift. So rotating the blades at 6x the rate you'd rotate them on Earth would be sufficient.
The more accurate numbers are 100 *.38 = 38. So the rotors would have to rotate 38 times as fast.
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Lift (along with drag) is proportional to the *square* of airspeed, all else being equal. But the rotor blades on a Mars helicopter would have airspeeds in the transonic to supersonic region, with very different airflow, so simply applying a scaling law like that isn't very accurate.
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So make them larger -- as large as you can get with the tips not quite going supersonic. (The speed of sound on Mars (probably around 540 mph at ground level) is a bit lower than it it is on Earth thanks to the low pressure, low temperatures and mostly CO2 atmosphere, so that's an even bigger problem.)
More blades as well -- not just 2, but 3, 4, 5, 6, whatever. There's diminishing returns past two (well, one!) but it can help when you don't mind using a lot more power for a little more thrust.
Go for fatt
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http://www.spaceref.com/news/v... [spaceref.com]
Attempt to fly at 100,000 feet, which is about I suspect the same density as martian atmosphere.
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Well, I suppose with awesome ion drives that might be feasible - but that's still going to have to be a pretty large and/or expensive satellite to justify sending a person + life support system halfway across the solar system instead of just sending a replacement satellite.
Especially since with a person on board you probably aren't going to take an efficient route, instead consuming hundreds of times the fuel to get there in weeks or months instead of years. Plus there's that hazard pay - which presumably y
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That's an interesting point - it's tough to imagine the economy of scale whereby human spaceflight is cheaper than another satellite. More fuel needed for the human to go the same distance due to time/mass, and then you'll have more spent on the return trip. That fuel cost would have to be less than the material cost of the original satellite for this to make sense.
Sending a robotic ship to place a new satellite, collect the old one, and return to wherever the nearest human base is would be much more effi
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The video however shows a full-scale mockup of the craft being developed, as well as a prototype being tested in a vacuum chamber at Mars atmospheric density, with the blades rotating at ~2400rpm. The good bits start at about 1:50.
Why don't you link to the real article? (Score:2, Informative)
Crazy Engineering: Mars Helicopter [youtube.com] on JPL's youtube channel (and it was there 2 days ago...)
Re: Sattelites??? (Score:2)
Nice thinking outside the box, NASA! (Score:1)
However: Serious technical challenges, here. In development, they'd have to find some way to simulate the Martian atmosphere; can be done. Martian gravity? Not sure how you'd do that, but let's put it aside for now. 'Autonomous' is putting it mildly! This would have to be a bit more than your garden-variety quadcopter drone. I believe we have the technolo
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There is an existing simulation for Mars flight in X-Plane. I've flown (simulated) flights on Mars many, many times. Very interesting differences from here on Earth. See:
http://www.x-plane.com/desktop... [x-plane.com]
http://www.x-plane.com/adventu... [x-plane.com]
Note I "flew" on Mars in a previous version of X-Plane. I'm not sure if the current version 10 supports flights on Mars. If nothing else, read the second link.
NASA trolling (Score:2)
Here we see NASA trolling for more funding at the expense of real exploration.
A ground vehicle is hands-down the cheapest, most effective, capable and and least risk vehicle for exploring terrain on a planet.
Mars rovers too slow? Put more solar panels on it and drive faster. Solar panels getting covered with dust? Cover the panels with UV resistant and abrasion resistant windows and install wipers or vibration based dust removal systems. Metal wheels getting torn up by rocks? Thicken the metal on the wheels
AMEE (Score:1)
This didn't turn out so well for Val Kilmer.
http://www.imdb.com/title/tt01... [imdb.com]
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send engineer over to fix blade when it breaks (Score:1)
I have been flying quadcopters for about 2 years over that time i have broken at least 50 blades..
I don't see an engineer heading over there to replace the broken blades when needed.
and if you think they got nice avionics for that thing and it will prevent it think again a gust of wind during landing and the thing is dead
There Is A Better Solution (Score:4, Interesting)
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Nature evolved legs for dealing with rough terrain. NASA needs to start using walking rovers, not rolling rovers.
Ah, but when man first invented the wheel (long after metallurgy and shipping) there was a great thunderclap from the heavens as God slapped his forehead and said "Why didn't I think of that?".
We can look to nature for inspiration, but have you ever seen the old film of the early plane with flapping wings?
morons (Score:2)
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How stupid are these people?!
Smart enough to have tested a prototype in a vacuum chamber that simulates Mars' atmosphere. And probably smart enough to RTFA before bashing somebody else. But I'm sure after reading a one paragraph summary that you are more educated on the topic than they are.
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Oh, and to clarify, Mars isn't a vacuum, it has atmosphere, just not much.
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