John Deere "Gator" Crossover Utility Vehicle

RobS · 2012-04-15 22:54:01

How'd you like to have a John Deere "gator" crossover utility vehicle on Mars. It can seat 2 or 4, has a 50 horsepower engine, can operate a small bulldozer blade, its cargo compartment can have a hydraulic lift for dumping, and it masses about 500 kg:

http://www.deere.com/en_US/docs/zmags/r … r_xuv.html

It's basically like a lunar rover. You can get an all-electric version, too.

Of course, it would have to be modified; the tires would probably fail in the cold, the steel might need to be replaced by lighter aluminum to save mass, etc. But it's a cool little vehicle and something like it would be great.

GW Johnson · 2012-04-16 13:11:50

RobS:

This is an excerpt from my last post from the "airbreathing engines" thread under this same topic:

"The closest thing I know to a practical piston engine system independent of atmospheric oxygen was attempted for submarines decades ago. Diesel fuel plus hydrogen peroxide actually did work from storable liquids while submerged. It's somewhat similar to the propulsion of the torpedoes, but more suited to a reusable vehicle. There were great difficulties with it, and it was superseded by atomic power in submarines, then forgotten.

Given some sort of fuel that could replace the diesel, and some way to make hydrogen peroxide on Mars, that technology might lead to practical internal combustion or gas turbine power plants on Mars. The storable liquids are pressurized at around 1 atm, like here. Hydrogen peroxide decomposes to oxygen and steam. Steam is the diluent gas that reduces stream temperatures to something you can confine with cooled steel.

It can be done, but needs some development before we take it to Mars and count on it at the risk of lives."

Given a tad of development to make fuel-peroxide really work well, the same piston-engine "Gator" could be run with stored liquids pre-pressurized to around 1 atm in their storage tanks. This shouldn't take more than a couple of years to check out and debug pretty thoroughly, if done by a Spacex-type of outfit. (A ULA-type would milk this for lots of gov't $ for about a decade.)

Rubber tires in the cold are a problem with brittle failure. But it can be done. Already was done for the Antarctic bases in the late 1950's.

GW

SpaceNut · 2012-04-16 17:28:26

There are several manufacturers of these styles of vehicles that I am aware of.....
http://www.deere.com/wps/dcom/en_US/pro … icles.page

RobS · 2012-04-16 19:06:13

The tires could alway be replaced by the wire mesh tire system the lunar rover used. I suppose its springiness would even mimic the shock absorbing ability of pneumatic tires. Zubrin seemed to think that liquid methane and liquid oxygen could be used in internal combustion engines with atmospheric carbon dioxide as a dilutant. One could also recycle the exhaust as a dilutant gas. Yes, Spacenut, if you google "utility vehicle" you'll find four other manufacturers listed. The gator struck me as cute and light, a sort of lunar rover for crossing the Rocky Mountains. Of course, it may be too small for men in space suits!

louis · 2012-04-16 19:22:30

RobS wrote:

The tires could alway be replaced by the wire mesh tire system the lunar rover used. I suppose its springiness would even mimic the shock absorbing ability of pneumatic tires. Zubrin seemed to think that liquid methane and liquid oxygen could be used in internal combustion engines with atmospheric carbon dioxide as a dilutant. One could also recycle the exhaust as a dilutant gas. Yes, Spacenut, if you google "utility vehicle" you'll find four other manufacturers listed. The gator struck me as cute and light, a sort of lunar rover for crossing the Rocky Mountains. Of course, it may be too small for men in space suits!

It's got to be electric, battery driven.

One thing I would remark upon, a battery on a vehicle can also be used to power many other applications around the base e.g. maybe a pneumatic drill.

We should be looking to developing wire tires on Mars asap. It would be great if the Mars colony could build its own vehicles from an early date. Wire dates will make that easier. Electric motors are relatively simply to construct. A pressurised may not be so difficult to construct.

SpaceNut · 2012-04-16 19:42:51

louis the lunar rover threads are probably trashed on the lunar Chariot and small pressurized rovers that Nasa was working on mabe they can be recovered. All that remains from the Nasa work for the moon can be found on the Desert Rat web site...

Current rover design has been using the cast tire rim with no actual tire employed. No need to pressurize the rover if its used for exploring with space suits....

Robs the engine combustion sound about right as does the diesel that GW Johnson proposes...

GW Johnson · 2012-04-17 08:29:45

I rather think Zubrin is wrong claiming atmospheric CO2 can be used on Mars as the dilution gas for fuel-oxygen combustion inside engines. The compression required is simply technologically infeasible on Mars. Thermodynamics requires engine cycle pressures similar to those here on Earth for decent output. Here on Earth, the source to be compressed is at 1 atm, on Mars it is at about 0.006 to 0.007 atm. We do not have compressors capable of compression ratios that high, in a physical form that could be part of a practical engine.

That's why I suggested the diesel/hydrogen peroxide scheme with the steam dilution gas "built-in" to the already-pressurized propellants. There's a reason they tried this (and not hydrazine decomposition) as submarine propulsion from late in WW2 until atomic power came along in the mid and late 1950's. It actually worked at practical levels of power, and with practical amounts of liquid storage. Peroxide storage stability is the only real hitch.

I don't know the details, but the steam torpedo power plant is a cousin of this system, and versions of it have been around since WW1. It's suitable for a one-way weapon, but not really suitable for the sub itself, or else they would have done it already.

My intuition suggests that liquid methane could be burned with hydrogen peroxide the same as diesel or kerosene can. Not sure whether compression or spark ignition might be better suited with methane (high vs low octane number) in piston engines (turbine doesn't care). But I'd think you could build a piston or turbine engine for shaft power around this combination that would work even in vacuum.

GW

SpaceNut · 2012-04-17 20:42:44

GW Johnson · 2012-04-19 09:16:44

You know, if this fuel-peroxide diesel thing were to work, then that makes possible locomotives on Mars not too dissimilar to what we have here. Not the same, but the same basic idea: IC/electric series hybrid.

That makes railroading possible big-time on Mars, once a set of bases (nascent colony) get planted. And that makes possible bringing together resources from different regions to one place to do manufacturing. It's a real bootstrap/chicken-and-egg process, but we've already done it here.

That's a major piece of technology that needs to be nailed down. It's not a prerequisite for a first mission, but it sure would be an enabler for a real settlement.

GW

Decimator · 2012-04-19 11:54:02

Do we actually need rails? Once the rocks are cleared from a path, what's stopping us from using that path indefinitely with normal wheels?

GW Johnson · 2012-04-19 12:25:44

Need rails? Use dirt path?

Sure, it's done all the time, especially in Australia. The only difference between a train of truck-trailers and a train on rails is friction. Any sort of wheels (pneumatic or solid) on roads, especially dirt roads, is very high friction. Rail friction is (2-3 order-of-magnitude) 100-1000 times lower.

If manufacture of the engine propellants is tough, then that's a serious issue to consider, since fuel use is proportional to the friction.

GW

Glandu · 2012-04-24 07:13:54

Beaten by GW, quicker than me(like often). Energy is costly(especially on Mars), and Rails reduce a lot fuel consuption. The global energy use of a truck on earth is 11 times bigger than the one of a train(France, 2005). Remove air drag on both(as air drag will be very low on Mars), and the difference is even bigger.

Though rails will also need energy to be built. Kind of investment. seems very worthwile to me between points of interests & central bases.

RobS · 2012-04-24 07:49:41

I'm intrigued by the idea of using hydrogen peroxide, GW Johnson. It occurs to me that we don't need much CO2 to dilute the combustion process, though. Maybe a small tank when you turn on the engine, but after that you could reuse the combusion products, and they're already at the right pressure. That'd work, right? Current internal combustion engines already reburn exhaust in order to reduce pollutants.

GW Johnson · 2012-04-24 10:18:47

I ran a crude ideal chemistry balance that assumed a "hydrocarbon" at an empirical H to C ratio of 2:1, and ideal conversion to nothing but CO2 and H2O. It balanced out as: CH2 + 3H2O2 = CO2 + 4H2O. By mass, the required peroxide to fuel ratio is about 7.3. The steam to fuel mass ratio is about 5.1, and the CO2/fuel mass ratio is 3.1. It might balance a bit different with methane fuel, but crudely in the same ballpark, I think.

That's a lot of steam to dilute the fuel-oxygen 6000F reaction down to something cooled steel can contain. Burning fuel and air, the nitrogen in the air fulfills the same dilution role, so that fuel air reactions at stoichiometry are in the 4000 F neighborhood, not 6000 F. Air/fuel by mass is typically near 14-15 with hydrocarbons.

The diesel-peroxide submarine propulsion scheme was not as efficient as sucking air on the surface or through a snorkel, but it did allow short bursts at high power while very deeply submerged. They did it in the same diesel engine as ran diesel and air normally. But I know little of the details. Normally, diesels run very lean of stoichiometry, and control power by mixture ratio, there being no air throttle at all.

Exhaust gas feedback in cars is a very small percentage, and is done mainly to finish burning fuel-like pollutants that couldn't get burned completely before the exhaust valve opened. It's a hot enough feed that your EGR valve will fail from corrosion, sooner or later. Mine certainly did, just not long ago. It upsets air/fuel mixture just a tad when that happens, knocking about a mpg off of about 30 mpg.

GW

RobS · 2012-04-24 10:30:33

My main concern, though, is making and storing hydrogen peroxide on Mars. It might be easier to take the H20/CO2 exhaust from the engine, cool it, condense out the water, and recirculate the cooled CO2 as a dilution gas; or capture the water (which you'll want to recycle anyway) and reinject it into the engine as a dilution factor.

GW Johnson · 2012-04-24 11:53:31

Peroxide can be handled OK, but not at full strength. 50% peroxide in water is the max accepted strength for safe long-term storage. You distill it up to 90+%, use it, then dilute what you didn't use back down under 50%. At 90%, you've only got 3-5 days before it spontaneously decomposes, and very violently, too. That's why the scheme never really caught on for the submarines. But, ignition of peroxide with hydrocarbon is hypergolic.

I think what RobS is proposing with exhaust gas dilution is fuel+oxygen, diluted by combustion gases. It can be made to work, but you have to cool the gases before you can feed them back. Since heat transfer is intrinsically slow compared to chemistry, that'll be the limiting factor on any design.

As for making hydrogen peroxide, I dunno. Never looked into it before. But I know it's done in very large quantities industrially. I've seen tank car trains of under-50% going by at RR crossings.

GW

GW Johnson · 2012-05-05 13:05:39

Chemical engines for Mars

I took a look around on the internet for the history of air-independent propulsion in submarines and torpedoes, specifically high energy-release chemical. Various sites had different things to say, but I think what I found matches well with much of what I thought I knew earlier.

Non-battery submarine ship propulsion (exclusive of air through a schnorkel and nuclear power) seems to have taken two forms, neither very successful for pushing the ship. One was running a piston diesel engine with fuel plus pure oxygen from bottles or a LOX supply, and running almost the entire exhaust stream back through as dilution gas. The articles didn’t say, but I’d almost bet there was a sea water cooler to cool the exhaust gas before feedback. These systems needed bottled argon for a temporary initial dilution gas to start up. They had serious problems with fires and explosions handling the oxygen, dangerous on any ship, really dangerous in a submarine. The other problem with exhaust gas feedback was the necessary filtering to clean it up of solids (carbon, etc).

The second was a Walter turbine-based design, centered on high-purity hydrogen peroxide decomposition, usually after-burnt with a little diesel fuel. Peroxide catalytic decomposition produced very superheated steam with oxygen in it. Some of these systems used alcohols or other lighter liquid fuels for the afterburner fuel. All were water-cooled combustors, some featured water injection. The articles didn’t really get into peroxide stability, but it takes above-90% strength to work like this, and the safe storage life at that strength is but a very few days. Spontaneous decomposition is very violently explosive, really bad inside a pressure hull.

The was one experimental USN sub (SS-X-1) that used peroxide decomposition for the oxygen to feed a piston diesel engine. I do not know how the steam and oxygen were separated, or what the dilution gas was. The boat was nearly lost to some sort of explosion, I presume related to high-strength hydrogen peroxide.

The non-electric torpedoes pretty much used the same class of systems from WW1-onward. Most of these by far used compressed air bottles to burn with an alcohol fuel, feeding through a turbine to drive the torpedo propeller. The articles today talk about methanol fuel, while the old salts’ tales I heard talked about ethanol, which actually has the higher combustion energy. Some of these were “wet” systems with seawater injection into the combustion stream, others “dry” without it. I think I read about peroxide being tried in some of these, but alcohol-air was, and is, by far the most common and most practical.

There is a reason earth-moving machinery here on Earth is almost invariably diesel-powered, with some heavy-duty hydraulics. The torques and forces required are enormous and variable. A piston diesel engine as a prime mover is the perfect choice to supply them, having really good low-speed torque. Gasoline engines also have similar characteristics, but are not as economical at part load, due to intake stream throttling. Diesel is controlled by mixture ratio, no throttle at all.

To run a piston engine like that on Mars, I think I would opt for LOX with liquid CO2 as the dilution gas. The LOX tanks are fairly low pressure items, but the liquid CO2 tanks are fairly high pressures (dozens of atm). LOX from water, and atmospheric CO2 are common on Mars. The LOX and liqCO2 tanks will be far larger than the diesel fuel tanks we are used to seeing. You just cannot aspirate and compress a 7 mbar CO2 atmosphere enough to serve on Mars. Pre-ignition as-compressed pressures in engines like that are in the neighborhood of 9-10 atm gasoline, and 15-22 atm diesel. 21/.007 is a compression ratio of 3000:1, which simply cannot be built into such an engine by any known means.

I don’t think I would mess with massive exhaust gas recirculation as the dilution gas, because there are very serious contaminant filtering issues. It would be easier and more reliable to work the liquid CO2 pressure tank issue.

I’d recommend liquid methane as the fuel on Mars, as it can be made from local water and atmospheric CO2. The engine will likely have to be spark ignition and throttled, like a gasoline engine, because methane has a high octane number, making it unusable as a diesel fuel. That fuel tank will also be larger than a simple diesel fuel tank.

The locomotive or truck tractor application is more in line with electric drive. Running a generator is more of a constant-speed thing, and that’s really well-matched with a turbine. LOX-liquid methane with liquid CO2 as the dilution gas source should work pretty well.

I don’t think I’d mess with hydrogen peroxide unless I had to, for some other compelling reason. The spontaneous decomposition difficulty is just too dangerous. At “safe” strengths, it’s just not useful as an oxidizer.

GW

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#1 2012-04-15 22:54:01

John Deere "Gator" Crossover Utility Vehicle

#2 2012-04-16 13:11:50

Re: John Deere "Gator" Crossover Utility Vehicle

#3 2012-04-16 17:28:26

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#4 2012-04-16 19:06:13

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#5 2012-04-16 19:22:30

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#7 2012-04-17 08:29:45

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#9 2012-04-19 09:16:44

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#10 2012-04-19 11:54:02

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#11 2012-04-19 12:25:44

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#12 2012-04-24 07:13:54

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#13 2012-04-24 07:49:41

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#14 2012-04-24 10:18:47

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#15 2012-04-24 10:30:33

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