Author Topic: manned rovers for the Moon and Mars  (Read 1306 times)

Offline Eric Hedman

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manned rovers for the Moon and Mars
« on: 03/16/2018 05:34 am »
I'm wondering about a couple of things as they would relate to potential manned rovers for the Moon and Mars:

1 - what would power them on long drives?  solar / batteries, nuclear, methane/lox etc?

2 - On concepts I never see large radiators.  Would they need large radiators to dissipate heat?

3 - what kind of range/duration of mission would they need to support?

4 - Could an exploration rover double as a construction vehicle?  Or would dedicated rovers be more appropriate?

I'm curious what people think.

Offline Cheapchips

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Re: manned rovers for the Moon and Mars
« Reply #1 on: 03/16/2018 06:49 am »
Batteries are the only thing that makes sense on Earth.  On Moon/Mars outpost I'd expect the same. Centralised power production is always more efficient that what you can achieve on a vehicle.

On vehicle solar/nuclear are solutions for lack of infrastructure.  If the Moon/Mars manned missions are base building that's not really an issue.  A Telsa semi equivelent battery pack offers a huge exploration range from the outpost.

I'd hope that whatever's used for Moon/Mars can leverage commercial battery packs and motors.  Don't know how you could adapt them for heat dissipation.  I assume EV's all make use of airflow over the battery to some degree?

Edit: Also, the moon buggy and all existing unmanned rovers have been mass constrained.  That's not so much of an issue with launch vehicles required for based building.  They could chuck several 5 ton vehicles to the surface. 
« Last Edit: 03/16/2018 07:13 am by Cheapchips »

Offline speedevil

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Re: manned rovers for the Moon and Mars
« Reply #2 on: 03/16/2018 03:40 pm »
If you relax the size constraint, a lot of things get a lot easier.
Heat loss goes as the square, volume as the cube.
Double the length of your rover, and your insulation just got twice as easy.
Good MLI insulation runs at 1W/m^2 leak or so on the moon.

Even a very insulated 1kg electronics package needs a radioisotope heater pretty much to survive over a lunar night.
A 1000kg electronics package needs you to remember to shut the lid, and it'll drop 5C or so on thermal inertia alone, before even going into batteries.

If your lunar vehicles are looking more like mine construction equipment (perhaps because they are mine construction equipment) - a lot of things get rather easier.

If a valid thermal solution is to load ten tons of water into a transpirative cooler, and a valid power solution is to have five tons of off-the-shelf lithium-ion cells, ...

If a vehicle can cope with a load full of crushed rock, it can cope with the atmospheric loads if you stick a lid on it.

This is more valid for the Moon than Mars, at least in the BFR architecture where the costs to launch to the moon are well under the costs to Mars.
But, even if you're considering 'conventional' launchers, in the FH price/kg range ($20M/ton or so landed on the moon), you need to stop and think really carefully about mass optimisation.
If you're optimising for low launch costs, and your launch cost is a tenth of your budget, you're possibly doing it wrong.
« Last Edit: 03/16/2018 03:44 pm by speedevil »

Offline Dalhousie

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Re: manned rovers for the Moon and Mars
« Reply #3 on: 03/18/2018 09:09 pm »
I'm wondering about a couple of things as they would relate to potential manned rovers for the Moon and Mars:

1 - what would power them on long drives?  solar / batteries, nuclear, methane/lox etc?

Batteries, fuel cells, and internal combustion are all options.  Solar panels for life support (a large significant power user) would be desirable, if the panels could be efficient enough.  Power outputs of RTGs are too low and reactors emit too much radiation[/quote]

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2 - On concepts I never see large radiators.  Would they need large radiators to dissipate heat?

Yes they would.

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3 - what kind of range/duration of mission would they need to support?

NASA studies currently aim at 2 week sorties, at radii of upto 100 km from the station.  This means a range of 300-400 km

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4 - Could an exploration rover double as a construction vehicle?  Or would dedicated rovers be more appropriate?

A common chassis would be possible for some purposes.  But the fitout would be different.  The same chassis could serve as an exploration vehicle, carry a crane, tip tray, flat bed. Perhaps a turntable mounted excavator on the rear. But it would not make a good loader, dozer, telehandler.  They could make inefficient ones, which might be good enough initially.

Size matters. An exploration vehicle might mass 4-6 tonnes.  Many vehicles seen on construction sites mass 10-30 tonnes.

« Last Edit: 03/18/2018 09:13 pm by Dalhousie »
Apologies in advance for any lack of civility - it's unintended

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