Re: Anti-armor mines!

Richard Slattery wrote:
>Submarines taken as a whole have exactly the same density as the water
around >them, so the detectors must be able to detect either the shell
of
the sub, or >the big pocket of air inside them.... or both in
combination
    While the density of a submarine is that of water, that's the
average
density! Not the density of, say, it's very dense nuclear fuel.
Similarly
with mines, while a mine could be made to be of a similar density to
earth,
parts of it would be of higher density. Thus a mine could be located
using a
gravity gradiometer.

>[Gravity gradiometers] will also detect rocks, gophers, roots, baked
bean
>cans....
    Sure a gravity gradiometer will detect dense rocks, bolts, and other
things that are denser than water or soil (gophers and roots have a
similar
density to water and soil). In conjunction with other sensors, computer
power and algorithms, I think that false indications will be minimal.
After
all, the baked bean can problem would have been extensively studied in
earlier trials! Baked bean tins and a whole variety of other common
dense
items would have their signatures recorded so that they can be
eliminated
from consideration.

Tony Christney <acc@questercorp.com> wrote:
>Keep in mind that both gravity meter and gravity gradiometer readings
are
>interpreted to indicate variations in the local densities. The
>materials used to build a several thousand ton submarine are far
>denser than the surrounding seawater (roughly 7 times as dense, IIRC).
>The difference in density between a mine and the surrounding
>substrate is much less. How could you tell the difference between
>a rock and a mine? I'm sure J.A. will correct me if I'm wrong, but
>most mines you would be looking for would be less than 10kg.
>
>I'm not saying it's impossible, but I just think that the signal to
>noise ratio would be extremely low. Avoiding detection would simply
>be a matter of matching the densities of the mine and the substrate.
>This would make detection by gravimetric means _impossible_ since the
>mine would not change the local gravity field.

    Naturally the effectiveness of sensors, and things designed to be
hidden, will change over time and with advances in technology. Much like
stealth aircraft hiding from radar. Now with bistatic radars, and with
liberal computing power, stealth vehicles can be located. Not easily and
not
as cheaply as standard radar. Stealth manufacturers will then find
another
way to keep their craft hidden.
    I don't think mines will be 'stealthed' against gravity detection or
other sensors. I think they will be made in whatever way is cheapest.
After
all, they're used in quantity and are disposable. Therefore, employing
expensive stealth measures is counterproductive to sales. Would you buy
one
stealth mine, or 1000 mines that can be easily located when time is
taken?
After all the purpose of mines isn't to kill people or vehicles. They're
there to injure people and immobilise tanks. They're there to slow or
block
an advance through the minefield.
    One stealth mine can only injure one or two squads, or immobilise
one
tank at most. The remainder can carry on and come to no harm. The
position
is over run. Therefore the expensive stealth mine is ineffective!
    1000 mines that are easily located. Well, the infantry platoon stops
as
their leading guys get shredded, the tank platoon comes to a halt as
their
tracks are blown away. Both platoons realise they're in a mine field and
retreat.
    Mine disposal engineers are brought up, and check their gravity
gradiometers, metal detectors, magnetic anomaly detectors, ground
penetrating radars, thermal vision and other sensors. Their computers
correlate all the info, together with the historical satellite photos,
and
the conclusion is that there is about 990 mines, located there, there,
there
and there! An
hour or two later, the engineers have carefully cleared the mine field.
The
attack proceeds several hours later. The minefield has stopped many
times
it's own value in enemy equipment and personnel, used up time, and
consumed
mine disposal resources.
    Also, mine manufacturers would be concerned about future
disposability.
They would be actively looking for ways that their mines could be easily
located and disposed of. Why? Think of lawsuits by civilians! Even
though
these mines would be easily located and easily disposed of, they would
be
dangerous in their active state and take some time to disable and
dispose of
them.
    One could quite easily imagine future mines that emit a creaking
noise
and a flash of firefly light every 100 seconds, being powered, say, by
heat
changes from day to night. This would keep civilians and most animals
away.
Every one knows that the minefield is there.

Andrew Martin
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