SUV's on Mars? - Making it sound simple, got me wondering

Rxke · 2004-03-04 12:13:46

By now, some people might have guessed, I'm an avid reader of the 'Rocket Company' series on HobbySpace...
This fictional story about building a cheap reusable rocket is a real treasure-trove for idea's etc.

Their last installment talks about SUV's on the Moon, and they make it sound so simple... Could the same approach be used on Mars, too?
They use a 'converted' commercial hybrid SUV, with some relatively modest adaptations, making it run not on petrol, but... [http://www.hobbyspace.com/AAdmin/archiv … page1.html]well, read the-short-chapter!
Mars OTOH, has a different milieu, it's not a vacuum, so cooling will be different etc...

GraemeSkinner · 2004-03-04 13:26:02

I'd think by the time they made all the adjustments it would be easier to build something to a custom design rather than modify an existing chassis. The advantage of building from scratch would be using lightweight metals, designing the chassis to cope with the stresses involved with travelling across the martian landscape (and the stresses involved with the two power units they suggest).
I'm all for saving money, but then it has to be balanced well with usability, reliability, and safety.
Its good however that people are thinking about new ideas - I always like seeing new ideas, at least it shows people are not letting their grey matter stagnate.

Rxke · 2004-03-04 13:53:03

The advantage of building from scratch would be using lightweight metals, designing the chassis to cope with the stresses involved with travelling across the martian landscape (and the stresses involved with the two power units they suggest).

I didn't give it much thought, really... But now that you mention it, it could OTOH be better to use a tried and tested design, esp SUV, that's already 'ruggedized' (and i mean a REAL suv, not a fancy car) you save a lot of R&D that way.
But using a lighter alloy, say titanium, that way it would be 300% overengineered, hehee, what with lesser gravity and all that...
Don't think there are hybrid SUV's on the market, today, though... And launch cost being what they are...

And i agree with what you said about using your imagination, the authors of the series, with an impressive engineering background, keep coming up with novel approaches on existing technology, you'd almost believe they know something we do not... Hopefully some people like Bill Gates (rich, guys, i mean) are reading this series too and gets all excited?

Yang Liwei Rocket · 2004-03-05 08:04:45

SUVs are u kidding?

we need much better high tech transports than Suv

Those over sized hunks of junk devour fuel, we have enough wars on earth because of people trying to get gas and petrols to pump into their fuel eating antique cars. :hm:

Lars_J · 2004-03-05 13:28:34

SUV? What a joke...

Infinately better solution:
Just stick an RTG on a scaled up typical rover chassi (6 wheels), and you'll have a vehicle that will not only be lighter but also infinately more reliable and capable - able to operate for YEARS without being refueled, with very few moving parts.

The basic idea of a hyper efficient hybrid system used on the moon may not be a bad one (in theory) - but why in the world would you want to bring the rest of the SUV body with you? The number of moving parts should be reduced for reliability reasons, and every wheel should have its own electrical engine for redundancy.

Dook · 2004-03-05 20:37:04

2,000 pounds per vehicle that each has a metal structure, wheels, springs, shocks, windows, hybrid-gasoline engine, full frame (aluminum I know), liquid oxygen tank, propane tank, 2 full radiators, water pump, water heater, exhaust radiator, exhaust filter, ion exchange column, lithium polymer batteries, solar cells and movable array, and another tank for breathing oxygen?? No way that weight figure is correct. In fact I would put the actual weight at over twice that amount. Plus you have the problems of liquid oxygen boiloff (unless you can keep it below -298 F), loss of vehicle pressure and oxygen each time you get out of the vehicle (which would be often), and heat loss through the metal structure. Also, I don't see anything to keep the inside warm since the whole thing would be shaded by the solar panels. And no provision for bathroom facilities or even a place where the astronauts can stand up without going outside in a space suit on a year long trip?

Assuming a 48 cu in engine that produces 20 hp at 3,600 rpm the engine is taking in 172,800 cubic inches of oxygen/propane per minute. Liquid oxygen has an expansion ratio of 862 to 1, so you would need a tank 2000 cu in (166 cu ft) tank just to provide enough oxygen to run the hybrid engine for 10 minutes. Someone check my math.

I like my idea (simple mars exploration vehicle post) better.

Shaun Barrett · 2004-03-06 07:45:31

I don't know much about propane/oxygen combustion in an internal combustion engine (what's the ratio of propane to oxygen for complete combustion, for example?) and I don't know where your "172,800 cubic inches of oxygen/propane per minute" comes from.
But there are 1728 cubic inches in 1 cubic foot, not 12.
Your 2000 cubic inch tank would only be about 1.16 cubic feet, not 166.
I don't know if this is any help or not.

Dook · 2004-03-06 08:17:47

Your right about the tank size, also the 172,800 cu in comes from multiplying 48 cu in engine size by the 3,600 rpm but I did not take into account that it is a four cycle engine so it is only taking in oxygen/propane on half the revolutions, not each. So 86,400 cu in of oxygen/propane would be used a minute. I don't know the ratio of oxygen to propane used either, certainly much more oxygen than propane.

edit 8 march: hehe, still got that wrong. Four cycle is, intake-compression-power-exhaust so it is only taking in oxygen/propane on 1/4 of the rpm so 43,200 would be used a minute. So a 10 cu ft tank has 17,280 cu in of liquid oxygen. Each cu in of oxygen expands 862 times as it warms so this would provide a total of 14,895,360 cu inches of oxygen gas. Divide by 43,200 (amount used a minute) and we get 344 minutes (5.7 hours) of driving time, which is better but nowhere near enough for a year long trip on the martian surface. This is also not taking into account the amount of oxygen lost due to bleed off. If you cannot keep liquid oxygen below -297 then it is almost a hopeless cause because the oxygen will turn to gas and explode any container you try to put it in, you have to let it bleed off.

Hazer · 2004-03-06 22:14:29

Now this seems like one of the oddest, if not original ideas that I have ever heard.
For Mars, I think you will indeed need an inherently high-tech vehicle, but you will have to engineer it to be easily repairable in the field without the need for special replacement parts.
What's the use of engineering a 300 million dollar vehicle if you cannot fix it when it breaks down on Mars?

Dook · 2004-03-07 08:21:58

$300 million, I sure hope that figure is exaggerated. I wouldn't expect the actual cost to be more than $1 million. If so maybe NASA should find another supplier, heck, I could build the thing in my backyard for the cost of the parts alone. Surely NASA could do the same thing.

Shaun Barrett · 2004-03-07 16:56:39

In Kim Stanley Robinson's books about Mars 'camping trips', he separates the vehicles from the sleeping habs. The vehicles tow trailers which have high-tensile-strength tents stowed in them. People spend most of the day in their suits but at night they can cook, eat and bed down comfortably in relatively spacious, heated, inflatable accommodation.
For any trips lasting longer than a couple of days, I think this would be more practical and better for morale.

I have many doubts about using almost-off-the-shelf SUVs on Mars. I think too much of the engineering solutions have been developed specifically for terrestrial conditions, including terrestrial gravity. By the time you make all the modifications necessary for Mars, it might be cheaper and more effective to start from scratch(?).
???

Dook · 2004-03-07 21:16:17

Why not have the heating and sleeping area inside the vehicle itself? And pressurize the thing so they don't have to wear pressure suits the whole time.

Rxke · 2004-03-07 23:59:33

Great reactions, keep 'em coming!
To be honest, I thought the SUV idea was a bit too far out, but of course in that particular story they have a craft that dramatically reduces launch-costs, making it a bit more probable to do such an errr.. experiment.
I'm still intrigued with their original idea, (the reusable small launcher) and if the space-elevator is not forthcoming, it might be the way to go... Come to think of it, i'm going to stirr up that elevator topic again, done some reading... looking good... Looking better evvery day....

Shaun Barrett · 2004-03-08 01:56:16

Hi Dook!
Your idea of pressurising the SUV and riding around in a shirt-sleeve environment certainly sounds simpler and more comfortable. But if you do that, the necessary modifications to the SUV become more problematic.
We've discussed the ideal artificial atmosphere for martian habs here at New Mars over the months and we've almost come to an unspoken consensus (I think). Using the good old fashioned pressure units, a 5 lb/sq.in. atmosphere comprising 3 lb/sq.in. of oxygen and 2 lb/sq.in. of nitrogen seems to be a good compromise.

I've just made a rough guesstimate of the glass area of a moderate-sized SUV in square inches and multiplied that figure by 5, to get the total internal pressure on the glass of your vehicle.
I get a rough figure of at least 15 tonnes - and that doesn't include the pressure on the doors, the roof, and other thin metal panels. The outward pressure on the windshield alone will be on the order of 4.5 tonnes.

It seems to me that if you want to pressurise an SUV cabin, you're going to have to reconsider the basic construction of such a vehicle. I think the changes required would be so fundamental that you might just as well purpose-build your Mars Car and forget your Jeep Cherokees etc.

In any event, unless the MarsSkins being developed here in Australia are a success, can you imagine two adults eating, sleeping and attending to other bodily necessities, doing useful research, and also wriggling into and out of bulky pressure suits - all inside an SUV?!!

After two days of that, I think we could safely phone the martian homicide squad ... because there will be a murder to investigate!
:bars2:

Dook · 2004-03-08 10:55:10

Redesign? Fine with me. How about a cylinder with driving windows up front, a separate depressure area in the back, and one rear hatch window? The windows would have to be aircraft strength but that's nothing we don't already know how to do.

RobS · 2004-03-09 23:36:56

I have wondered whether the technology for developing inflatable habs can't be sued to develop inflatable vehicles. In other words, except for the hard metal doors and the chassis, the vehicle would be a balloon of advanced plastics such as kevlar and nomex. Such a system might allow a large vehicle to be squeezed into a small payload bay as well.

The new chasses being developed for fuel cell vehicles puts all the power generation and use--fuel cells and wheels--in the chassis, with the car body on top a snap-on. One could even go to the dealership and "upgrade" by having a different body snapped onto the chassis you bought. This kind of technology, applied to Mars, could allow a vehicle to consist of a thin chassis to which wheels could be put on and a body inflated on top of after arrival on Mars.

-- RobS

Shaun Barrett · 2004-03-10 00:05:25

Very nice idea, Rob. :up:

I suppose this is a dumb question but have they considered making inflatable habs (or inflatable Mars vehicle passenger compartments for that matter! ) with a double-wall, not only for the obvious safety factor but also to allow hydrogen to be pumped into the cavity?
I'm just thinking of the advantage of hydrogen for radiation protection: No cascade of secondary particles.
???

RobS · 2004-03-11 14:21:49

The inflatable Transhab designed for ISS and possible deep space use wasn't just doubled walled; I think it was made out of about 40 layers. I doubt a centimeter of gaseous hydrogen would provide any significant shielding because at the pressure it wouldn't have any significant mass. But the layers themselves are made out of high-hydrogen plastics and would store more hydrogen in them than a gas layer.

-- RobS

Bill White · 2004-03-11 14:50:47

I have wondered whether the technology for developing inflatable habs can't be sued to develop inflatable vehicles. In other words, except for the hard metal doors and the chassis, the vehicle would be a balloon of advanced plastics such as kevlar and nomex. Such a system might allow a large vehicle to be squeezed into a small payload bay as well.
The new chasses being developed for fuel cell vehicles puts all the power generation and use--fuel cells and wheels--in the chassis, with the car body on top a snap-on. One could even go to the dealership and "upgrade" by having a different body snapped onto the chassis you bought. This kind of technology, applied to Mars, could allow a vehicle to consist of a thin chassis to which wheels could be put on and a body inflated on top of after arrival on Mars.
-- RobS

I favor inflatables for many many purposes on Mars.

As an aside, the chassis RobS is talking about was discussed in a Wired magazine article a while back. Very inexpensive and interchangeable fiberglass bodies on a "skateboard" chassis with 4 wheel 4 axle electric drive. The target market is China where average income levels will remain insufficient to purchase US grade street legal autos for a long time to come. These would NOT be crashworthy in US, Australia Japan etc. . .but in Beijing they would survive crashes with bicycles.

Anyway, adding a Transhab style cabin to the chassis would seem easy enough and the fabric could probably be folded then rolled up and vacuum packed for minimal volume while shipping.

"Instant car in a can?"

Use a larger chassis, perhaps modular, add oversized tires, each wheel with independent drive and suspension with very high ground clearance all of it computer controlled for traction control and have various inflatable tops interchanged as needed for various purposes. SUV, pickup truck, long distance van with sleeping accomodations.

Inflatables with a relatively heavy chassis would also seem to have a low center of gravity for rollover protection and the like.

Then don't buy the chassis, require auto makers to bid on who will give you the most money for the privilege of giving you the chassis needed for your settlement (with their logo prominently displayed of course)

By the way, I also see permanent settlers using inflatable furniture, chairs, beds, tables, perhaps filled with emergency water rations.

SBird · 2004-03-15 17:13:44

These would NOT be crashworthy in US, Australia Japan etc. . .but in Beijing they would survive crashes with bicycles.
8< ----- SNIP!
By the way, I also see permanent settlers using inflatable furniture, chairs, beds, tables, perhaps filled with emergency water rations.

Having been to China, I can say with certainty that crashes with bicycles are the least of your concerns. The way traffic operates over there, I wouldn't feel safe in anything less substantial than a tank.

I do agree that inflatables are the way to go given the weight and space constraints. On the other hand, there's somethings that's just a little anticlimactic about going all the way to Mars just to sit around on flimsy little balloon chairs. :;):

C M Edwards · 2004-03-17 14:26:21

RE: Inflatable furniture, I'd have thought throw pillows for sure...

RE: SUV's, they're hardly the most reliable things on the planet (Earth!), but more importantly as a class they're hard to work on. Lots of modern cars are made to be repairable only with specialized equipment. While it's reasonable that the first crews would bring any equipment with them that was necessary to repair their vehicle, it's also reasonable that they would look for vehicles that didn't require much to repair them in the field.

Unfortunately, many other types of vehicle have the same difficulty: You need a garage to fix them. They are designed to exclude repair in the field.

GraemeSkinner · 2004-03-17 14:35:58

Modern vehicles use technology that is hardly every repairable at the roadside, older vehicles are simpler to maintain. We have two cars, one a modern (2 year old) estate car that has me baffled whenever I need to do anything on it; the other (45 year old technology) is simple to work on with simple engineering. As someone previously said keep it simple. Inflatable habs will be worth looking into for future exploration, but for the first few manned missions I'd be hoping for simple technology - with hopefully less to go wrong.

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#1 2004-03-04 12:13:46

Re: SUV's on Mars? - Making it sound simple, got me wondering

#2 2004-03-04 13:26:02

Re: SUV's on Mars? - Making it sound simple, got me wondering

#3 2004-03-04 13:53:03

Re: SUV's on Mars? - Making it sound simple, got me wondering

#4 2004-03-05 08:04:45

Re: SUV's on Mars? - Making it sound simple, got me wondering

#5 2004-03-05 13:28:34

Re: SUV's on Mars? - Making it sound simple, got me wondering

#6 2004-03-05 20:37:04

Re: SUV's on Mars? - Making it sound simple, got me wondering

#7 2004-03-06 07:45:31

Re: SUV's on Mars? - Making it sound simple, got me wondering

#8 2004-03-06 08:17:47

Re: SUV's on Mars? - Making it sound simple, got me wondering

#9 2004-03-06 22:14:29

Re: SUV's on Mars? - Making it sound simple, got me wondering

#10 2004-03-07 08:21:58

Re: SUV's on Mars? - Making it sound simple, got me wondering

#11 2004-03-07 16:56:39

Re: SUV's on Mars? - Making it sound simple, got me wondering

#12 2004-03-07 21:16:17

Re: SUV's on Mars? - Making it sound simple, got me wondering

#13 2004-03-07 23:59:33

Re: SUV's on Mars? - Making it sound simple, got me wondering

#14 2004-03-08 01:56:16

Re: SUV's on Mars? - Making it sound simple, got me wondering

#15 2004-03-08 10:55:10

Re: SUV's on Mars? - Making it sound simple, got me wondering

#16 2004-03-09 23:36:56

Re: SUV's on Mars? - Making it sound simple, got me wondering

#17 2004-03-10 00:05:25

Re: SUV's on Mars? - Making it sound simple, got me wondering

#18 2004-03-11 14:21:49

Re: SUV's on Mars? - Making it sound simple, got me wondering

#19 2004-03-11 14:50:47

Re: SUV's on Mars? - Making it sound simple, got me wondering

#20 2004-03-15 17:13:44

Re: SUV's on Mars? - Making it sound simple, got me wondering

#21 2004-03-17 14:26:21

Re: SUV's on Mars? - Making it sound simple, got me wondering

#22 2004-03-17 14:35:58

Re: SUV's on Mars? - Making it sound simple, got me wondering

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