Author Topic: Mars Exploration: Rovers  (Read 15385 times)

Offline Kal_23

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Mars Exploration: Rovers
« on: 09/18/2013 01:23 pm »
So I'm watching a documentary on the latest mars rover, with the broken wheel. And it has gotten stuck because it hit a soft patch of dirt and sunk. My question is have the scientists ever thought of trying to put a hovercraft on Mars?

Offline Jim

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Re: Mars Exploration: Rovers
« Reply #1 on: 09/18/2013 01:36 pm »
So I'm watching a documentary on the latest mars rover, with the broken wheel. And it has gotten stuck because it hit a soft patch of dirt and sunk. My question is have the scientists ever thought of trying to put a hovercraft on Mars?

Atmosphere is too thin.  Would take too much power.

Offline Kal_23

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Re: Mars Exploration: Rovers
« Reply #2 on: 09/18/2013 01:45 pm »
Are there any other drive systems that be plausible? Because the way I see it this could be a real problem for future missions.

Offline Robotbeat

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Re: Mars Exploration: Rovers
« Reply #3 on: 09/18/2013 03:50 pm »
Are there any other drive systems that be plausible? Because the way I see it this could be a real problem for future missions.
Just use bigger wheels (Curiosity has much bigger wheels). There, solved the problem.

And besides, the wheel didn't get stuck until WELL after the 90-day mission they were supposed to last for. This isn't a huge problem for future missions.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Zach121k

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Re: Mars Exploration: Rovers
« Reply #4 on: 09/18/2013 04:50 pm »
There were plans for airborne craft. Such as the Ares Plane. http://marsairplane.larc.nasa.gov


Other proposed missions included a balloon and other gliders.
http://en.wikipedia.org/wiki/Mars_aircraft
« Last Edit: 09/18/2013 04:53 pm by Zach121k »
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Offline hop

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Re: Mars Exploration: Rovers
« Reply #5 on: 09/19/2013 01:51 am »
So I'm watching a documentary on the latest mars rover, with the broken wheel. And it has gotten stuck because it hit a soft patch of dirt and sunk.
Note, this does *not* refer to the latest rover (Curiosity), it presumably refers to Spirit, which was lost 2210 sols into her 90 sol mission. Spirit only became irrecoverably stuck because two wheels had already failed, and even then might have escaped if winter hadn't set in.

Both the MERs exceeded their mission requirements by a huge margin. Opportunity is still going and making new discoveries, over 3400 sols into her 90 sol mission. By any rational measure, the MERs were a great success, so it would be a mistake to say the loss of Spirit implies anything needs to be fixed.

Offline R7

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Re: Mars Exploration: Rovers
« Reply #6 on: 09/19/2013 09:51 am »
Just use bigger wheels (Curiosity has much bigger wheels). There, solved the problem.

Also, if possible, drive faster. The dynamics change with speed. Going snail-paced ensures you get stuck in every possible spot you can get stuck. And don't stop on slippery uphill. More powerful drive train and smarter driver AI required, but as a bonus you cover a lot more distance too for increased science gain.

Done myself a lot of driving on icy/snowy roads knowing that if I stop or even slow down it would mean shoveling to get going again.
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Offline Melt Run

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Re: Mars Exploration: Rovers
« Reply #7 on: 09/19/2013 05:54 pm »
Just use bigger wheels (Curiosity has much bigger wheels). There, solved the problem.

Also, if possible, drive faster. The dynamics change with speed. Going snail-paced ensures you get stuck in every possible spot you can get stuck. And don't stop on slippery uphill. More powerful drive train and smarter driver AI required, but as a bonus you cover a lot more distance too for increased science gain.

Done myself a lot of driving on icy/snowy roads knowing that if I stop or even slow down it would mean shoveling to get going again.
I bet that you don't close your eyes for 8 to 40 minutes at a time however when your on those icy roads. That is the time delay between when a image is sent and when the Mars rover receives a correction.

Offline Robotbeat

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Re: Mars Exploration: Rovers
« Reply #8 on: 09/19/2013 06:15 pm »
Just use bigger wheels (Curiosity has much bigger wheels). There, solved the problem.

Also, if possible, drive faster. The dynamics change with speed. Going snail-paced ensures you get stuck in every possible spot you can get stuck. And don't stop on slippery uphill. More powerful drive train and smarter driver AI required, but as a bonus you cover a lot more distance too for increased science gain.

Done myself a lot of driving on icy/snowy roads knowing that if I stop or even slow down it would mean shoveling to get going again.
I bet that you don't close your eyes for 8 to 40 minutes at a time however when your on those icy roads. That is the time delay between when a image is sent and when the Mars rover receives a correction.
Autonomous driving is a thing. Already used for Mars navigation, in fact.
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Offline Melt Run

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Re: Mars Exploration: Rovers
« Reply #9 on: 09/19/2013 07:33 pm »
So I'm watching a documentary on the latest mars rover, with the broken wheel. And it has gotten stuck because it hit a soft patch of dirt and sunk. My question is have the scientists ever thought of trying to put a hovercraft on Mars?
If there was enough power, if there were enough atmosphere, I couldn't imagine how much dust would be blown up!

Offline Blackstar

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Re: Mars Exploration: Rovers
« Reply #10 on: 09/19/2013 09:03 pm »
Autonomous driving is a thing. Already used for Mars navigation, in fact.

Used at slow speeds.
« Last Edit: 09/19/2013 09:03 pm by Blackstar »

Offline Blackstar

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Re: Mars Exploration: Rovers
« Reply #11 on: 09/19/2013 09:15 pm »
There were plans for airborne craft. Such as the Ares Plane. http://marsairplane.larc.nasa.gov


I'll nitpick here, but with a purpose:

There were proposals for airborne craft. There were not plans for any. There was a Mars airplane proposal in the Mars Scout competition that did not get selected. It was never an approved mission.

The Mars airplane is a neat idea, but it's the kind of thing that seems nifty until you start looking at the engineering closely. It would have to be deployed in the air, and do so during that very rapid descent toward the surface. Drop the heat shield, deploy the wings, start the engine, and do all of that while zooming straight toward the surface at high speed. If one thing does not go perfectly, you call in the NTSB to investigate the first plane crash on another planet.

Another downside is that the science payload is pretty slim. It cannot carry much in the way of instrumentation. I was in a meeting once where a scientist mentioned that another drawback of such a mission is that if you do see interesting things on the ground you cannot really do anything about it. You cannot go and actually touch the cool stuff with your instruments.

When evaluating mission proposals, reviewers look at the upsides--how much science can it do?--and the downsides--what is the risk and the cost? A Mars airplane doesn't do all that well on either side of that equation. Yeah, it would be cool. But cool isn't part of the equation.

An airplane on Titan has more upsides. The deployment risk is considerably lower because Titan has just about the best possible atmosphere for entry and for flying. And because Titan's surface is what it is, a rover would have a lot of trouble there and so being airborne has a lot of advantages. I think I posted a proposal for a Titan airplane on this site awhile back. Downside of a Titan airplane is that it is expensive to go that far out. Saturn missions--even really simple ones--start at a billion dollars and go up from there.

Offline Robotbeat

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Re: Mars Exploration: Rovers
« Reply #12 on: 09/19/2013 09:24 pm »
Autonomous driving is a thing. Already used for Mars navigation, in fact.

Used at slow speeds.
Used at slow speeds on Mars, but not entirely on Earth. Darpa Grand Challenge winners averaged ~15 mph, which is orders of magnitude faster than rovers on Mars. It's possible, even feasible.
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Offline Blackstar

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Re: Mars Exploration: Rovers
« Reply #13 on: 09/19/2013 10:06 pm »
Autonomous driving is a thing. Already used for Mars navigation, in fact.

Used at slow speeds.
Used at slow speeds on Mars, but not entirely on Earth. Darpa Grand Challenge winners averaged ~15 mph, which is orders of magnitude faster than rovers on Mars. It's possible, even feasible.

How many paved roads are there on other planets?

Offline Robotbeat

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Re: Mars Exploration: Rovers
« Reply #14 on: 09/19/2013 10:27 pm »
Autonomous driving is a thing. Already used for Mars navigation, in fact.

Used at slow speeds.
Used at slow speeds on Mars, but not entirely on Earth. Darpa Grand Challenge winners averaged ~15 mph, which is orders of magnitude faster than rovers on Mars. It's possible, even feasible.

How many paved roads are there on other planets?
DARPA Grand Challenge was off-road.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Blackstar

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Re: Mars Exploration: Rovers
« Reply #15 on: 09/20/2013 12:18 am »
Yeah, okay, whatever.

JPL is not going to drive a rover fast autonomously on Mars.

Offline R7

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Re: Mars Exploration: Rovers
« Reply #16 on: 09/20/2013 08:53 am »
JPL is not going to drive a rover fast autonomously on Mars.

Ever? Why?
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Offline bob the martian

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Re: Mars Exploration: Rovers
« Reply #17 on: 09/20/2013 01:17 pm »
JPL is not going to drive a rover fast autonomously on Mars.

Ever? Why?

"Hey, slow down, what's that over there?"

Offline hop

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Re: Mars Exploration: Rovers
« Reply #18 on: 09/20/2013 05:28 pm »
JPL is not going to drive a rover fast autonomously on Mars.

Ever? Why?
I'm surprised you even need to ask. If you are talking about anything remotely real (i.e. missions that could plausibly be designed in the next several decades), it should be pretty obvious. If you are talking about some far future fantasy... why bother asking, you can make up any scenario you like.

Going fast to get over soft stuff is a valid strategy for off-roaders who can get out and shovel, or wait for help or use other recovery aids. It might also be a valid strategy for military robots, which can potentially be recovered and are ultimately expendable. It's not a valid strategy for an irreplaceable vehicle that costs hundreds of millions if not billions. Being slow and methodical and being able to stop at any point and wait for the ground is a feature, not a bug. Even if the AI and sensor technology were up to driving at speed with acceptable LOV risk (which it isn't), it would be a bad trade.

There's also no actual need. Vehicles like MSL have very good mobility, and could be made even more capable if required. There millions of square kilometers of scientifically interesting territory accessible to current systems.  If you really needed to get over a lot of loose sand, there are ways to do it with a slow vehicle, but for the most part the interesting science isn't in the sand, so you are probably better off just going around.

On top of that, going fast would drive up your costs a lot. You need more power, more robust parts (=more mass), more and faster sensors and computers (=even more power, more mass) etc.

Not going to happen in the real world on any time-frame worth thinking about.

Offline Robotbeat

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Re: Mars Exploration: Rovers
« Reply #19 on: 09/20/2013 05:35 pm »
The Apollo lunar rovers drove fast, where fast in this context means non-quasi-statically. They were really tooling out there! And the Apollo lunar rovers were incredibly lightweight. And they covered more territory than Curiosity is supposed to using just non-rechargeable batteries.

As machine learning allows autonomous driving over terrain to approach human capability, I really don't think this has to be such a huge issue. If anything at all has improved and is improving continuously in spaceflight, it's computing power, sensors, and algorithms.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

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