GEVs/Grav/Arty

> From Oerjan:

Until you get Mavericks or Hellfires which you can fire indirectly at
ranges of 40 km and above, indirect-firing artillery will have a
niche.

Whenever you have a supply dump (which isn't mounted on grav vehicles)
within 50-150 km of the enemy, indirect-firing artillery will have a
niche.

** That distance might change if you have grav vehicles that need refuelled
once a month, fly at hundreds of kph, and have weapons with
40+ km range... :)

> 2) A tank is loud and noisy. So is a GEV. Either can be made lower

Grav might be low-signature, but I doubt it. If something starts
messing with the local gravity field, I suspect it would be fairly easy
to detect :-/

** Maybe. Depends. If I can just find a way to create a localize field to
negate my own mass, then it might not be detectable from too far away. But it
might. Who knows? And this would definitely have a lower *relative* signature
than tracklayers which are loud in the audible spectrum. It'd take higher tech
to detect.

It probably wouldn't be anywhere near as noisy as a GEV, but it would have
other signature problems to cope with.

** Possible.

Considering that even the Challenger (the heaviest of the current Western
tanks) is "only" 62 tons fully loaded, and the various
ex-Soviet tanks average around 45 tons, I'm not entirely sure why
you'd
want to make the GEV tank 80 tons :-/

> I'm also not sure why you are talking about GEV tanks, when I wrote:

"... I wouldn't be surprised at all if you could build GEV SPs and APCs with
today's hovercraft technology. Not particularly economic, of course, but
probably possible."

Note the complete omission of tanks from the list; it was entirely
intentional. Modern 155mm SP guns average around 25-30 tons when fully
combat loaded, ie about half the mass of an MBT.

** D'oh! My bad. Sorry. But my point about any heavy vehicle eating lots of
diesel still applies.

Looking at today's military hovercraft and assuming that track transmission is
about as heavy overall as skirts (the skirts themselves are probably lighter,
but the extra turbines and fans aren't), we'd need to increase their cushion
pressure by about 75% from the 1989 level to make an M113 APC hover. I'd be
quite surprised if this were not *technically* possible today. Why you'd want
to do this beats me,
though <shrug> It'd definitely have severe problems with dust/spray
clouds and noise, too.

** Depending on skirt design, dust spray could be minimized. Noise
might also be minimized - I've encountered quiet high volume fans.
Nothing like a GEV would use, but who knows? I'm not vizier enough to suggest
the technology couldn't be adapted.

An M1A2 would need about four times the ground pressure of today's hovercraft.
This starts sounding a bit too heavy for today's
technology. The most serious problem isn't the energy supply, though -
it is finding space for the lifting and maneuvering fans and air intakes,
preferrably somewhere where they won't be wrecked by the first
burst of small-arms fire directed at the vehicle <g>

** Admittedly. But we might use some form of air-ram and vectored
thrust. We might develop a lot more fan efficiency. We might heat the exhaust
gas to give us more lift. I don't know how it might be solved, but it might be
solved I suggest. Like all conjectures,it is a guess, but it seems possible
given 180 years.

> 4) GEVs can move through swamps and if packing non-recoil weapons

There are no non-recoil weapons.

** Laser? Gyrojet? Harsh words?

 Only low-recoil ones...

** What recoil do you see from a HEL?

and I'd want to be *very* certain of my platform's stability (and ability not
to drift into various nearby objects) before I fired any large weapons
from it while hovering over a swamp :-/

** Assuming your computer couldn't compensate with vectored thrust.

I didn't have a lot of interest in it until you made me look closely at
it :-/

** <sniffle>:) <MUHAHAHAHA!> Welcome to the world of
too-many-things-to-work-on-or-buy..... I've been a resident for
years.... ;)

> ** What recoil do you see from a HEL?

Photons have momentum. They don't have mass, but they do have
momentum, calculated as planck's constant / wavelength (I think
that's right, ooo my memory is bad today, I think there might be some 2*Pi
factors in there).

A laser shoots out a lot of photons. Conservation of momentum has to apply.
The laser must therefore recoil.

> Thomas Barclay wrote:

> ** D'oh! My bad. Sorry. But my point about any heavy vehicle eating

Sure. I made the same point in the original post <shrug>

> It'd definitely have severe problems with dust/spray

The highest-pressure hovercraft I found - the US MCAC/LCAC - was also
the most modern, and the noisiest and most dust-throwing.

The problem isn't with the skirt design. It's with the basic gas
dynamics - no matter how your skirts are designed they won't have an
airtight seal against the ground (not if you want to move at any kind of
speed, anyway!), so you'll get air leaking out from the cushion.
These gas jets cause most or all of the dust whirl-up... and the higher
the cushion pressure is the faster these jets will be, and the worse
the dust or spray whirl-up will be.

> The most serious problem isn't the energy supply, though -

Sure; that was what I was thinking of. Still difficult to find good places to
put them, and tricky to design them so they won't be damaged by small arms
fire.

> We might develop a lot more fan efficiency.

Quite likely. Won't help much for the vulnerability problems, though.

> We might heat the exhaust gas to give us more lift.

Gives you very little extra lift unless you get scaldingly hot gasses
(the cushion volume is way too small for any measurable hot-air balloon
effect), but even a small increase in gas temperature would cause you massive
IR signature problems.

> > 4) GEVs can move through swamps and if packing non-recoil

Lasers, true <g> Well, not exactly true, but at least an extremely low recoil.

Gyrojets have recoil from gas friction against the launch tubes, just
like all other rocket-ish weapons; not nearly as much as guns of
course, but still quite measurable (and on a hover vehicle with no ground
friction, it'd impart a certain amount of velocity too).

Harsh words tend to be rather inefficient as combat weapons - "Sticks
and stones...", etc <g>

> and I'd want

Could be done, yes.

I've been a resident of the world of too many things to do for the past
fifteen years. You merely added another load onto the too-big burden
<g>

Regards,