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RE: Hover tanks

From: "B Lin" <lin@r...>
Date: Wed, 25 May 2005 18:13:49 -0600
Subject: RE: Hover tanks

Actually, I don't think that HS has "lightweight" armour technology as
Iridium and Osmium are the two densest metals known.  The hulls and
turrets of HS tanks are cast Iridium and since the size is roughly 9
meters by 4 meters for the hull, it is a rather heavy object.  Also the
listed weight for a HS tank is 170 tonnes, roughly 3 times what an
Abrams weighs for roughly the same dimensions.

An Abrams has a 1500HP turbine engine (21HP/ton). VTOL aircraft and
helicopters have dramatically higher power requirements - for instance
the CH-54 Skycrane with a max weight of 21 tons has two Pratt & Whitney
JFTD12-4A, 4500 HP engines (about 428 HP/ton).

The Harrier with 13 tons max weight has a Pegasus engine capable of
21,000 lbs of thrust (note that the Harrier can not take off vertically
when fully loaded as the thrust to weight ratio is not greater than 1 to

The LCAC (Landing Craft, Air Cushion)for the US Marines uses 4 turbine
engines producing 12,280 BHP for a craft that is 200 tons full load (61
HP/ton).  The footprint of an LCAC is 88 feet x 47 feet, roughly 8 times
the size of an M1 Abrams, but only 3 times the weight.

Inferring that a smaller footprint requires more power to maintain a
vehicle off the ground, to get something like a HS tank off the ground
using the stated footprint would probably require something closer to
the power/weight ratio of a helicopter (428 HP/ton) or about 72,760 HP
of engine power or 340,000 lbs of thrust to go purely VTOL.

For reference, a PTG10 Gas turbine from GE has an output of 15,000 BHP
and the dimensions of 30' x 8' x 13' and weighs 32 tons. And the
Rolls-Royce Trent 900 engine which powers the Airbus 380 generates
70,000 lbs static thrust and has a fan blade diameter of 112 inches
(almost 10 feet). 

The ability to generate a huge amount power in a compact enough space
will essentially require fusion plants or some equivalent to make hover
tanks practical, as fuel and space requirements are a major stumbling
block.	For example the LCAC has a fuel capacity of 5000 gallons.  It
burns 1000 gallons an hour to run its engines.	


-----Original Message-----
From: owner-gzg-l@lists.CSUA.Berkeley.EDU
[mailto:owner-gzg-l@lists.CSUA.Berkeley.EDU] On Behalf Of Roger Burton
Sent: Wednesday, May 25, 2005 5:09 PM
Subject: Re: Hover tanks

On Wed, May 25, 2005 at 03:42:04PM -0600, B Lin wrote:
>If you didn't care about floating on water (as most MBT's don't) then
>you can have larger ground pressures and a more compact footprint.  But
>as you shrink the footprint and increase the ground pressure, you need
>more power to stay aloft until you reach something like a Harrier which
>can be held aloft on pure thrust.

Well, yes. Part of the problem with this argument is that hovertanks
really don't make sense _unless_ you regularly have to sprint at high
speed and/or cross substantial open water, and can make them light
enough to do that; for any given output from your power plant, you can
connect it to a conventional track drive mechanism and get much more
armour into a more compact chassis at the price of going rather more

(Hammers' Slammers basically ignore this by having practically infinite
power output, very lightweight armour technology, and terrain that's
peculiarly well-suited to hovercraft.)


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