

11 Amazing Things NASA's Huge Mars Rover Can Do - sasvari
http://www.space.com/13689-nasa-amazing-mars-rover-curiosity-science.html

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ars
Yes, this really is an amazing rover! But I wonder why they chose such a
complicated landing sequence. So many places where things can go wrong.

I hope this rover actually does land successfully - with its RTG power source
it could last for decades!

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nknight
Because Mars is a pain in the ass to land heavy gear on.

There's too much gravity, too little atmosphere, and we haven't perfected AI.
You can't rely entirely on parachutes, the air bags they used on the last few
landings won't hold up to something so heavy, and landing with direct use of
retrorockets would pretty much require a human pilot to be sure of -- and even
if we had a human pilot, the enormous amount of dust it would kick up is
problematic.

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rbanffy
They could have practiced on the moon...

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nknight
Even if they had the budget for a 1-ton lunar probe, landing on the Moon bears
almost no resemblance to landing on Mars. The Moon's gravity is 0.16g to 0.38g
on Mars, and the Moon has no atmosphere at all. This makes direct rocket
landings far easier and completely changes the landing profile.

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rbanffy
Obviously the Moon is a very different environment, but it's also much closer
to home (which makes it a lot easier to find out what went wrong). It's a
little cheaper in terms of fuel, and the trip is much shorter. We can't say we
have any recent experience with easy rocket moon landings either.

There are so many new ideas being employed for the first time I don't feel
sure it will work. I assume they did several crane drop tests indoors, but I
don't know if they did outdoor tests with a chopper attached to the crane
module to see how stable the crane platform needs to be and with the crane
module using its own rockets (tethered to a tower, maybe) to control its
position while a reduced mass rover simulator touches down. Like I said, tons
of new ideas, hardware and software that have never been used (and that won't
be used together until they get to Mars) that will all have to work perfectly
the first time.

Again, I'm all in to sending this rover to Mars, but shouldn't we be sending
rovers to the Moon for some time now? These people are much smarter than
either you or me, but it doesn't change the fact engineering progresses
incrementally and it seems we are jumping up the stairs and skipping steps. I
only hope we don't break a leg here.

I am an engineer. We don't like complicated things.

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jerrya
The earth is an even closer place to land on.

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rbanffy
Of course. I wouldn't suggest landing on the Moon something that never landed
on Earth. I wouldn't land on the Moon (or Mars) anything that didn't land
reliably over Earth a hundred times, until we understand thoroughly what can
go wrong.

I would be perfectly confident with a device you could trow it out of a plane,
that would parachute until a reasonable altitude, engage rockets to hover and
lower a rover to the surface a dozen times without incident.

It'll be at least 30 years until we can inspect the crash site to learn what
went wrong.

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pavel_lishin
And how do you translate what you learned from a parachute landing on Earth to
the moon?

It's like assuming that you can easily swim five miles because you can easily
jog five miles.

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rbanffy
For the Moon, we would use rockets, or a crane attached to a vehicle with
rockets. For Mars (and Earth, or Titan) we add parachutes to the mix because
there is an atmosphere. From hovering-stage until rover deployment, everything
is the same except for wind, which would be absent on the Moon.

The idea is that you have to lower a car-sized rover from a hovering rocket-
powered platform that has to remain relatively still regarding the ground. On
Mars, the platform would use parachutes to slow it down. On the Moon it may
not be needed at all, but you would use rockets, if you still needed the
hovering platform approach (say, landing a very heavy habitation module).

Throwing the probe out of a plane, letting it descend on parachutes for some
time and then making it hover using rockets until it gently deposits a rover
on the surface seems a good way to make sure we know how to do all the
required steps for a successful deployment on Mars. Lots of important
variables are very different - Mars' atmosphere is very thin, so the crane
would have to use far more power to slow itself down (or a much larger
parachute), but the gravity is lower, so the rover would descend more slowly
and it would require less power to hover. There could be some wind, but the
forces applied to the vehicle would be different than what would be on Earth
(Martian atmosphere is thin, but the winds are faster). The whole operation
appears to me somewhat similar.

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ars
No one is arguing about the need for testing. They are saying that testing on
the moon adds nothing.

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rbanffy
It would at least prevent us forgetting how it's done ;-)

I think it'd be worth, and relatively easy, to operate a rover on the Moon.
Remember we don't always know what we should have learned until after we try.
This Mars rover is a huge step. Huge steps is someting engineers should learn
to avoid.

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adaml_623
Anybody else notice that the page title is "10 Amazing Things NASA's .... etc"

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jerrya
Does anyone notice that the image with the rover and its chem cam is straight
out of H. G. Wells?

Compare and contrast:

[http://i.space.com/images/i/13468/i02/nasa-curiosity-
rover-m...](http://i.space.com/images/i/13468/i02/nasa-curiosity-rover-mars-
chemcam.jpg?1321666474)

with

<http://i.imgur.com/kYofe.jpg>

This leads me to believe that our Martian rover needs some sort of acoustic
imaging devices.

~~~
adaml_623
Maybe they are expecting 'trouble'. Certainly they seem to be downplaying the
fact that they are deploying an autonomous robot with a laser that can
vapourise stone.

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ortusdux
#12: MMRTG Nuclear Power Source. Deviating from its predecessors, Cursorily
will be powered by 10 pounds of plutonium dioxide. Earlier, solar power
rovers, had to hibernate during long periods of darkness, and at times these
hibernations proved mission ending
([http://en.wikipedia.org/wiki/Spirit_rover#Stationary_researc...](http://en.wikipedia.org/wiki/Spirit_rover#Stationary_research_platform)).

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Loic
Is it me or on all the pages of space.com you cannot find a single link to the
NASA website? As soon as you try to get more about the project, you are sent
to previous stuff on space.com but no links to the original source, that is,
the NASA website. Very annoying...

