Steam Power for Tanks

[rickshaw]

There are two major problems with steam-powered combat vehicles, and they are complementary/interrelated:

1: Steam power is, for the most part, inherently less efficient than internal combustion (both thermally and mechanically), at least for combat vehicle purposes. Trains/locomotives operate under a different kind of duty cycle that takes advantage of steam's efficiencies while minimizing the inefficiencies; however the exact opposite is true when it comes to automotive applications (and combat vehicles come under that category).  The same can be said for turbine engines. Say what you will about the Lycoming engine in the M1, the MTU diesel in the Leopard II makes more power and uses less fuel.

You're discussing chalk and cheese.  The M1 Abrham Lycoming is a gas turbine - it runs continuously at high speed to gain the greatest efficient fuel burn.  That is not unfortunately translated into the most efficient use of fuel versus power in a situation where mechanical power loads can vary enormously at any given moment.  The Diesel OTOH can and does tailor its fuel demands to the mechanical demands placed on it, so it is inherently more efficient.  A steam engine however can store energy, after heat is produced in the form of a boiler which can mean that it produces the most efficient power output for its fuel burn.

2. The designs for lightweight, thermally efficient steam engines that do exist (cf Doble steam engine) are extremely high-pressure/temperature designs. I don't know about you, but being in combat basically in the same box as a 750psi @ 750°F (52Bar @ 400°C) pressure cooker doesn't sound that good of an idea.

No worse than the fact that you are within a few centimetres of sufficient chemical energy to completely destroy the AFV where it is stored.   The engine compartment where that pressure cooker is, is completely isolated from the fighting compartment(s) where the personnel are.  If the tank suffers a penetration which is sufficient to penetrate both compartments and create a catastrophic release of heat and pressure from that "pressure cooker" I rather think it would be a moot point as to whether the ammunition has exploded, the crew are dead anyway (from inner spalling ) or heat/pressure from the steam system.

Steam power is an idea that is lofted once in a while, but dies quickly when it is realized that any of steam's perceived advantages are overwhelmingly outweighed by its disadvantages and the conveniences of the alternatives.

As the original article pointed out, a great deal of the prejudice against steam was and remains exactly that, prejudice, rather than a realistic appraisal of its advantages and disadvantages.

[rickshaw]

Later, it was learned that Henschel in Germany actually had been making layouts for a steam power installation in a Tiger tank at almost the same time. They found that existing boilers and condensers occupied too much space, and since the OKH was disinterested, the project was dropped.

After remembering having a look at this thread...... a steam-powered Porsche Tiger II?

Maybe it's my eyes playing tricks on me, but the Porsche pattern seems to have a bigger powerpack compartment than the Henschel pattern?

It would.  It was an electrical drive system which required rather a large dynamo as well as the motor to drive the vehicle.

[GTX]

Whilst not steam powered as such (it is actually wood gas I believe with the resulting gas compressed into the cyclinders shown), this could give inspiration for a steam powered tank:




Regards,

Greg

[raafif]

ooh!, more info for my Pz-II woody -- strange marking on the Italian stuff there -- red stars ? = Russian then captured by Germany & hurridly remarked with crosses & the four-leaf clover symbol ??

[dy031101]

Curiosity- is there any picture and/or drawing that shows the engine deck of the US Steam Tank?

[sagallacci]

If you are willing to go with an open cycle system, steam does offer a very compact power package. A high-efficency/small volume boiler and direct drive engine would need only a fraction of the space of a Diesel or turbine as well as offering a much simpler and very robust unit. The obvious drawback are the need for lots of water, though cycling the exhaust steam through the reserve water can recover some of it and add a little thermal efficency.
The extra few tons of water, a portion of which would presumably be in light weight unarmored tankage, would be more than off-set by the lack of a big and heavy armored engine+transmission package.

[rickshaw]

It would be possible, indeed desirable to use the water as armour.  It would be an effective form of passive armour, particularly against chemical energy rounds.  The Swedes pioneered such armours utilising fuel tanks as "anti-Bazooka " plates along the sides of the Strv-103 "S" tank (they look like thin "Jerry" cans).

[sagallacci]

I was wondering about just that, though more in the sense of a filler for spaced armor (though wonder about hydro shock issues??) But at the same time, it would be an easy way to distribute tonnage.

[rickshaw]

I was wondering about just that, though more in the sense of a filler for spaced armor (though wonder about hydro shock issues??) But at the same time, it would be an easy way to distribute tonnage.

With careful baffling such shocks would be reduced.  If compartmentalised, you'll only lose one compartment at a time.  If designed properly, repairs would be quick and easy - just remove the damaged section and replace it with a new tank.

[Hobbes]

If you are willing to go with an open cycle system, steam does offer a very compact power package. A high-efficency/small volume boiler and direct drive engine would need only a fraction of the space of a Diesel or turbine as well as offering a much simpler and very robust unit. The obvious drawback are the need for lots of water, though cycling the exhaust steam through the reserve water can recover some of it and add a little thermal efficency.
The extra few tons of water, a portion of which would presumably be in light weight unarmored tankage, would be more than off-set by the lack of a big and heavy armored engine+transmission package.

Are you sure about that?
If you use a piston steam engine, its size depends on the operating pressure. The higher the pressure, the smaller the engine. A diesel engine has a working pressure of about 20-25 bar (compression ratio of 20:1 plus turbocharging). If your steam pressure is 20 bar, the steam engine needs the same piston surface area as a Diesel. I've no idea what boiler pressures you can reach.

The steam land speed record holder is interesting in this regard: it uses 40 bar.
http://www.steamcar.co.uk/design.html

Compare to the JCB Dieselmax:
http://en.wikipedia.org/wiki/JCB_Dieselmax
less total weight, and 4x the power output.

A steam turbine can be more compact, will be about the same size as a gas turbine. But a small turbine spins at high speeds so it needs gearing.

Then the boilers. Note the size of the boilers in the LSR vehicle, and that's only 250 kW. A tank needs 4 times more. You also need lots of fuel (a diesel is around 40% efficient, an open-cycle steam engine won't get more than 10%, so that's 4 times the fuel for the same range), plus tons of water since you throw it all out of the exhaust.