Author Topic: Mars hopper  (Read 19827 times)

Offline douglas100

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Re: Mars hopper
« Reply #20 on: 07/08/2012 01:10 pm »
An airship (or any other form of LTA vehicle) in 1% atmosphere is quite a challenge.  (Even if it is a CO2 atmosphere...)

LTAs look soft and fluffy, but they are incredibly difficult to tame, especially if you're thinking full automation.  Every time you come near the surface, it's a game of Russian roulette.



nope, the airship is not for lifting the probe/lander, but for mounting and lifting huge solar array and uplift system. the lander is hanged on light weight cable, and lift off ground only when uplift system is on, like a helicopter.

Have to agree with meekGee. Although I think airships are cool in general, I think this idea has formidable difficulties. To lift a useful payload in the tenuous Martian atmosphere the envelope would have to be very large indeed. This would make the vehicle very prone to winds and turbulence (which isn't much of a problem for other types of equipment, apart from the dust problem.) I think deployment and control of such a large structure makes this idea inferior to other means of Mars surface exploration.

And again: this topic should be another thread (unless someone can cite some evidence that SpaceX is working on Martian hoppers and airships.)
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Offline cordor

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Re: Mars hopper
« Reply #21 on: 07/08/2012 02:36 pm »
An airship (or any other form of LTA vehicle) in 1% atmosphere is quite a challenge.  (Even if it is a CO2 atmosphere...)

LTAs look soft and fluffy, but they are incredibly difficult to tame, especially if you're thinking full automation.  Every time you come near the surface, it's a game of Russian roulette.



nope, the airship is not for lifting the probe/lander, but for mounting and lifting huge solar array and uplift system. the lander is hanged on light weight cable, and lift off ground only when uplift system is on, like a helicopter.

Have to agree with meekGee. Although I think airships are cool in general, I think this idea has formidable difficulties. To lift a useful payload in the tenuous Martian atmosphere the envelope would have to be very large indeed. This would make the vehicle very prone to winds and turbulence (which isn't much of a problem for other types of equipment, apart from the dust problem.) I think deployment and control of such a large structure makes this idea inferior to other means of Mars surface exploration.

And again: this topic should be another thread (unless someone can cite some evidence that SpaceX is working on Martian hoppers and airships.)

http://www-robotics.jpl.nasa.gov/applications/applicationArea.cfm?App=2

I can't picture spacex would spend resources on developing Mars exploration hardware. From what i understand, they do delivery business, they will ship a probe from earth to mars if NASA pay for it, but once there, how it hops around is NASA business.

Offline Idiomatic

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Re: Mars hopper
« Reply #22 on: 07/08/2012 05:32 pm »
If you can't imagine SpaceX spending money developing tech to explore/visit mars you haven't been following SpaceX AT ALL.

Offline cordor

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Re: Mars hopper
« Reply #23 on: 07/09/2012 02:02 am »
ya? show me the press release about spacex is going to build a mars explorer. They talked about visiting mars many times, but all gave me impression, it's based on assumption, someone like nasa is willing to pay for their delivering service. They never mention explorering mars out of their own pocket.

Offline Idiomatic

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Re: Mars hopper
« Reply #24 on: 07/09/2012 02:36 am »
ya? show me the press release about spacex is going to build a mars explorer. They talked about visiting mars many times, but all gave me impression, it's based on assumption, someone like nasa is willing to pay for their delivering service. They never mention explorering mars out of their own pocket.

Elon has said that a full presentation/video on their mars exploration systems will be given end of this year or early next year as they are fairly solid.

Offline cordor

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Re: Mars hopper
« Reply #25 on: 07/09/2012 02:53 am »
"The NASA science hardware would fly to the Red Planet aboard SpaceX's Dragon capsule" that's all i got.

Offline kkattula

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Re: Mars hopper
« Reply #26 on: 07/09/2012 04:42 am »
A 1000kg hopper would need a lot less propellant, but would have significantly less mass available for processing plant and power supply. i.e. take just as long or longer to generate the smaller amount of propellant.


What might work is a main lander that takes care of propellant production, and one or two, small, wheeled hoppers with a return range in the tens or hundreds of kms.

They would tank up, drive to a safe distance then hop to a distant target. Drive around for a while doing science, then hop back to near the main lander and drive up close for refueling.
« Last Edit: 07/09/2012 09:39 am by kkattula »

Offline Kaputnik

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Re: Mars hopper
« Reply #27 on: 07/09/2012 09:00 am »
Well that makes a little more sense that the initial suggestion.

However, any serious science mission starts not with a cool bit of hardware, but with a scientific objective.

I would suggest that landing a vehicle of the suggested complexity and ability would be in the same league technically as a sample return mission. If the two were head-to-head which do you think would actually get funded?
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Offline kkattula

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Re: Mars hopper
« Reply #28 on: 07/09/2012 09:47 am »
Well that makes a little more sense that the initial suggestion.

However, any serious science mission starts not with a cool bit of hardware, but with a scientific objective.

I would suggest that landing a vehicle of the suggested complexity and ability would be in the same league technically as a sample return mission. If the two were head-to-head which do you think would actually get funded?

Mini-hoppers returning samples to the main lander for return to Earth?

Since the mini- hoppers would need precision navigation aids back to the main lander anyway, why not send a second lander with just an empty ERV?

The first ISRU lander could produce propellant for it, while the rover-hoppers load it with samples.

Plus the whole thing is good practice for a light-weight human mission.

Offline go4mars

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Re: Mars hopper
« Reply #29 on: 07/09/2012 05:33 pm »
Earth return vehicle (or earth return vehicle launcher) should double as a hopper.  Land it on ice, refuel, go to somewhere interesting, collect samples (humans with dirt-bikes and rappelling cables).  Then fly the hopper either directly to base or back to the ice depending on how much range it has, and whether the base has a natural water source too.

The most robust way to hop around might be a dual fuel method: use the same engines and tank for both CO and hydrogen, as needed/able.

Smelling the roses is for detailed characterization after the broader planetary/regional concepts are established.  Though a lot of similarly useful discoveries would be made quickly on the dirt bikes.  This hopper would land near interesting features presumably.
« Last Edit: 07/09/2012 05:38 pm by go4mars »
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline go4mars

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Re: Mars hopper
« Reply #30 on: 03/15/2013 04:49 am »
What would be the best power source for a rocket hopper while in ISRU mode (other than broadcast power)?  Nuclear?  Solar? 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline meekGee

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Re: Mars hopper
« Reply #31 on: 03/15/2013 05:13 am »
Even the general question of how to power a stationary ISRU (or anything for that  matter) has not been answered yet.

I can't imagine a hopper that's carrying the power source and ISRU plant with it. It will be less hassle to carry more fuel from the stationary ISRU plant to suffice for a longer trip.

Neither a nuclear plant nor a solar field are something you want to carry with you...
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Offline Norm38

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Re: Mars hopper
« Reply #32 on: 03/16/2013 01:09 am »
What would be the best power source for a rocket hopper while in ISRU mode (other than broadcast power)?  Nuclear?  Solar? 

NTR with compressed C02 as the reaction mass.  Refueling is running a pump.

Offline meekGee

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Re: Mars hopper
« Reply #33 on: 03/16/2013 03:07 am »
What would be the best power source for a rocket hopper while in ISRU mode (other than broadcast power)?  Nuclear?  Solar? 

NTR with compressed C02 as the reaction mass.  Refueling is running a pump.

OOh!

Sure, if only the power plant can:
a) allow T/W > 1
and
b) can fully shutdown arbitrarily.

This is not some puny 100W RTG mind you... 
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Offline A_M_Swallow

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Re: Mars hopper
« Reply #34 on: 03/16/2013 06:03 am »
Even the general question of how to power a stationary ISRU (or anything for that  matter) has not been answered yet.

I can't imagine a hopper that's carrying the power source and ISRU plant with it. It will be less hassle to carry more fuel from the stationary ISRU plant to suffice for a longer trip.

Neither a nuclear plant nor a solar field are something you want to carry with you...

It depends which planet you are on.  For Mars use solar power to split CO2 into 2CO and O2 at your base camp.  Burn them to fuel the hopper.

Offline meekGee

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Re: Mars hopper
« Reply #35 on: 03/16/2013 03:23 pm »
Even the general question of how to power a stationary ISRU (or anything for that  matter) has not been answered yet.

I can't imagine a hopper that's carrying the power source and ISRU plant with it. It will be less hassle to carry more fuel from the stationary ISRU plant to suffice for a longer trip.

Neither a nuclear plant nor a solar field are something you want to carry with you...

It depends which planet you are on.  For Mars use solar power to split CO2 into 2CO and O2 at your base camp.  Burn them to fuel the hopper.

for sure - I was interpreting the question at the top of the page as a "carry along" ISRU that goes with the hopper, and so was saying I can't think of any power source that is light enough (unless you want to hop once every couple of years....)
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Offline Andrew_W

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Re: Mars hopper
« Reply #36 on: 03/16/2013 10:40 pm »
A rocket with a propellant mass ratio of 2 and an exhaust velocity of 3km/s could hover above Mars surface for just 9 minutes before running out of fuel, I don't see any way of getting the vehicles surface to surface range up to a distance that would make it economic enough to compete against surface rovers.
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Offline 93143

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Re: Mars hopper
« Reply #37 on: 03/17/2013 07:30 am »
A rocket with a propellant mass ratio of 2 and an exhaust velocity of 3km/s could hover above Mars surface for just 9 minutes before running out of fuel, I don't see any way of getting the vehicles surface to surface range up to a distance that would make it economic enough to compete against surface rovers.

Well, that's half the delta-V required for orbit...  With a decent mass ratio you can do quite a distance semiballistic, much faster than a rover, and if you've got a nuclear CO2 engine you can refill directly from the atmosphere without having to power a cracking plant.

It was Zubrin's idea, I believe...

Offline Andrew_W

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Re: Mars hopper
« Reply #38 on: 03/17/2013 09:26 am »
A rocket with a propellant mass ratio of 2 and an exhaust velocity of 3km/s could hover above Mars surface for just 9 minutes before running out of fuel, I don't see any way of getting the vehicles surface to surface range up to a distance that would make it economic enough to compete against surface rovers.

Well, that's half the delta-V required for orbit...  With a decent mass ratio you can do quite a distance semiballistic, much faster than a rover, and if you've got a nuclear CO2 engine you can refill directly from the atmosphere without having to power a cracking plant.

It was Zubrin's idea, I believe...

I would have thought having half the mass as propellant was a decent mass ratio. What's been suggested - as I see it - is a vehicle that can do on Mars what a helicopter can do on Earth, not many nuclear powered helicopters around...
I confess that in 1901 I said to my brother Orville that man would not fly for fifty years.
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Offline rklaehn

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Re: Mars hopper
« Reply #39 on: 03/17/2013 11:09 am »
Assuming short ballistic hops with no hovering, and ignoring gravity and drag losses for now, the optimum trajectory is to launch at a 45° angle. Then both horizontal and vertical velocity are v = delta_v/sqrt(2).

Then the flight time t is 2*(delta_v/sqrt(2))/g and the covered distance is 2*delta_v/sqrt(2) * (delta_v/sqrt(2))/g = v^2/g.

d = v^2/g

This approximation roughly holds as long as d is much smaller than a planetary radius.

For a roundtrip, the velocity has to be divided by 2, and the covered distance is 1/4 of the one-way distance.

Now let's plug in the rocket equation into the equation above:

v = v_e * ln(m0/m1).

d = v_e^2 * ln(m0/m1)^2 / g

For mars, g is 3.8 m/s^2. Assuming a v_e of 3000m/s and a mass ratio of 2, you get a respectable 1137915m or about 1100km. A mass ratio of 2 leaves a lot of room for payload, and an Isp of 3000m/s should be achievable using the easiest ISRU propellant CO/O2.

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