Newsgroups: sci.military.moderated
From: George Herbert <gherbert@crl.com>
Subject: Re: Tank engines
Date: Fri, 20 Mar 1998 17:24:58 GMT

Samuel Fang <sfang@vt.edu> wrote:
>Brian <brian@coombs.anu.edu.au> wrote:
>>	Interestingly, why does the US Army persist with the gas turbine,
>>considering its inordinate demands on fuel?  In the gulf, the British
>>challengers and chieftains, equipped with diesels were able to advance
>>approximately twice as far as US Army units without refuelling.  In an
>>article in Janes International Defence Review, it was noted that the
>>determinant of the speed of advance for the US Armoured units was not the
>>speed of the tanks and other AFV's but the speed at which the supply,
>>most notably fuel resupply train could keep up!
>
>Well, it's nice to have some reserve maneuver speed...
>
>And it's kind of embarrassing to have your tanks getting passed by
>their tankers on rough terrain...
>;-)
>
>Seriously, though, the ease of maintance and replacement of a gas
>turbine is probably one of the major reasons why they're around.
>Relatively speaking, the gas turbine on the M1 series is easy enough
>to be taken out and swapped for a new one.  The actual dynamic parts
>of the drivetrain are easier to work with.
>
>Also, while the Challengers and Chieftains may be able to go farther
>without refueling, they're still going to take the same amount of time
>(or longer) to get there, given their lower speeds.  The unique sound
>characteristics of the gas turbine also give it something of an edge
>in detection (though there is the problem with thermal imaging...).
>;-)

It's important to go back and look at the state of the art
at the time the turbine decision was made.

Diesels have come a long ways since then, in both reliability
and power density.  At the time, the M-1 roughly doubled the
power of the existing tank engines.  The desired speed required
that power level, and the only way to do it then was turbine.
Lower average maintenance and higher average fuel usage were
tradeoffs, but the key driver was the power requirement.

Since then, I think people have generally concluded that
the M-1 doesn't need quite that much power and speed.
The heavy variants need that much power, but the origional
M-1s had more power than they could really use.
A 50 ton tank now does reasonably fine with a 1200 HP
diesel.  It's not unreasonable to suggest that a variant
M-1 with a high power diesel might be worthwhile investegating,
and such variants have been tested.

In an ideal world, with lots of money for tanks, the real
ideal solution would be a turbine m-1 with an APU,
perhaps with an electric drive system that allows the APU to
maneuver the vehicle at 4-5 mph for non-combat-advance
local mobility, keeping you from having to keep the turbine
rolling all the time.  That would probably hav maximum range
and minimum maintenance.  Other good solutions are a high
power diesel (but that requires more maintenance),
or just keeping more attention on logistics.
Desert Storm demonstrated that the US logistics model
fundamentally worked, although expensive and painful
at times.  I think the US Army looks at its budgets
and the procurement realities and figures that paying
for fuel in war is easier than paying for new engines
or seriously modified tanks in peacetime, and is going
to keep doing it the existing way for a while.

-george william herbert
gherbert@crl.com