How would vehicles for Mars differ from Earth's?

[CCWilson]

I'm sure that Earth-built vehicles and heavy equipment wouldn't function in the cold of an airless planet or moon because all lubricant and fuel would freeze, among other issues. So how do you design vehicles and other equipment for transportation and work in those environments? Would electric power be the way to go? Would internal combustion engines work, if insulated?

 

[Simon Bridge]

You design the vehicles to cope with the environments by carefully considering the environment in terms of the mission profile and available materials of course.
I'm afraid the question is too broad.

We use electricity because it is cheap to transport and more can be made in situ.
It is technically possible to make ICEs that work on Mars, but why would you want to?
Is there something in particular you are thinking of?

 

[CCWilson]

I'm writing a story and need more general information than I have about how vehicles and equipment - especially heavy equipment like bulldozers or well-diggers - could be designed to function on an airless planet. Would gears and articulated arms and such need to be lubricated and thus insulated, or are there strong materials that glide over each other well enough without lubrication and would hold up at temperatures near absolute zero? Are there energy sources other than batteries that could put out the massive power needed to drive heavy equipment? I confess almost total ignorance on these issues.

If someone knows of a white paper or article or textbook that discusses this subject in a way understandable to a layman, I'd appreciate it. Thanks.

 

[Simon Bridge]

You can run an ICE in vaccuum, for eg, the same way you run a human - put it in a box with air and fuel supplies and some way to keep cool.

There are ceramics that make joints that don't need to be oiled.
The Mars Rover uses aerospace bearings and lubrication is one of the concerns.
http://www.nasaimages.org/luna/servlet/view/search/what/Sun/Hazard-identification+Camera/Spirit?q=+Mars+Rover&os=0&pgs=50&sort=Title%252CDate
There are endless clever ways to get lubricant to bearings.

You probably want to look into the design of space probes - NASA is the place to start.
Voyager went a long way and had a few moving parts.
The various rovers' designs are well discussed.

You have to narrow your spec somewhat - are these vehicles expected to be manned? How long do they need to run for? How big? How much work does it have to do?

For an example of a light 2-man transport for an airless environment - have a look at the LRV design.

For power sources - probes often use nuclear batteries.
There is nothing especially wrong with using electric power to do heavy work.
There are already electric drive systems for heavy machinery like bulldozers - run on hybrid technologies.

For pure SF you way want to look at the SF RPG resources around - GURPS Space is handy, covering current to advanced tech.

What you won't find is a single (lay) paper discussing the field - it is too broad.
Google for "how to engineer for space challenges" and similar terms and you'll get lots of specifics.

 

[CCWilson]

Many thanks, Simon. I'm looking into all your suggestions. Here's what I need: a vehicle to carry substantial weight, including an operator, over long distances (hundreds - maybe even thousands - of miles) - and here's the kicker: no sun, so no solar power! I suspect that a fuel cell - hydrogen or otherwise - might be my best bet - although I wonder if an insulated, oxygen-fed internal combustion engine might give greater range. I assume that nuclear batteries would be underpowered but I'd be happy to learn otherwise. Thoughts?

 

[Simon Bridge]

The machine would be purpose-built for this, or you imagine that it has to do that trek in an emergency?

You want a space version of one of these:
http://www.chinabzk.com/bzk/en-us/product/D20.htm
... the engine has a max power of 187kW.
Maybe smaller? Bigger? But looking at a terrestrial design for parameters would be a good place to start.

Nuclear power generation:
https://netfiles.uiuc.edu/mragheb/www/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/Radioisotopes%20Power%20Production.pdf

Air independent propulsion:
http://en.wikipedia.org/wiki/Air-independent_propulsion

 

[CCWilson]

Engineers would have several years to develop the vehicle. A little Google research and I'm leaning toward an RTG (radioisotope themoelectric generator) power source to charge batteries to run an electric engine. That's a concept that was new to me but is very interesting. As you probably know, the heat from the isotope's decay would generate electricity through the use of thermocouples. The ideal isotope to use, apparently, is Plutonium 238, whose radioactivity is not dangerous unless inhaled or ingested. The US has stopped production of Pu 238 and would have to restart it if we ever decided to actually develop such automobiles - which is very unlikely - but might be the best option for my story.

 

[Simon Bridge]

RTGs are neat :)
I once worked out what it would take to power my house on one (not cost effective).
The big bottleneck, technically, is on the T part.

Note: if you also had large-scale nuclear power generation, the waste products could be used to fuel RTGs.

Looking at the figures - and applying them to the power-stage of the Dozer (link above), you'd need:

623 Cassini-style units - about 4.8T just in fuel.
(There's a pic of one in the wikipedia page)

62 BES5-type units and 1.9T in fuel.

BTW: since it is a story you can always look at ideal Carnot cycle engines or Stirling Engine.

 

[Czcibor]

In case if you need a stronger engine I'd advice something like 1,3 MW with weight of 13 tones. ;)

http://en.wikipedia.org/wiki/McMurdo_Station