Off the rails
‘If it ain’t broke…’ might be an accurate summary
of developments in artillery compared with progress in other military
technologies. But the humble gun may soon have a new lease of life according
one man at Dstl.
In 1995 defence research scientist David Haugh published a paper describing
the potential of electromagnetic (EM) launchers on future warfare.
The basic principles of firing a projectile have been untouched for
over 800 years, but David argued that electromagnetic launchers –
or ‘rail guns’ – offered a quantum leap in gun science.
Conventional guns vs rail guns
In a conventional gas or powder gun the projectile is pushed by gas
molecules. This effectively means that the projectile can never exceed
the speed of the molecules pushing it - typically less than 2000ms-1.
There is also a limitation due to the strength of the gun barrel, which
acts as a pressure vessel.
In an electro-magnetic (EM) gun, chemicals are dispensed with and the
projectile is pushed by an EM field. There are no upper velocity limits
set by the physics of the action, so there is potential for very high
shot velocities.
The lack of explosive propellant in armoured vehicles, one obvious
home for such guns, means that their vulnerability is also greatly reduced.
David highlights another huge advantage:
“No propellant means that the weight of the ammunition is greatly
reduced,” he says. “Weight reduction is a big element for
the armed forces. If you can do that, while also increasing performance,
then you are on to a winner.”
While a vehicle’s weight may reduce in one area, does it rise
elsewhere due to the power supply needed to generate the electrical
power for its EM gun?
“The power supply is a major problem,” concedes David.
“But it’s a problem that is shared across the board with
other modern weapons as everything becomes more electric in nature.
“That said, current power supply research means we could see
something workable emerge in the near future. Until then, this is lab
research using capacitors of many cubic metres in size.”
Aside from this drawback, the real strength of EM guns lies in the immense
projectile speed they can provide. More speed in the air means greater
damage at the target, more penetration into armour, longer range and
more accuracy against moving targets.
‘Dumb’ projectiles are also nigh on impossible to disrupt,
requiring no guidance systems and a simple targeting system. This could
make them more reliable than guided weapons in a hostile, electronic-jamming
battlefield.
An EM gun has a lower recoil too. In fact, the breech can be left open
as there is no need to seal any pressure. Lower recoil benefits platform
stability, so a lighter, faster vehicle could carry an EM gun to match
the power of a conventional gun on a heavier tank.
The Dstl team says problems with aerodynamic heating in flight due
to the high projectile velocities should also be overcome by using suitable
materials to resist the temperatures.
But despite Dstl’s research, the UK effort is dwarfed by US spending
on the concept as well as other nations, including France, Russia, China
and Japan.
David warns: “If we don’t look into the use of EM launch
technology then we are in danger of becoming complacent - we could conceivably
have chemically propelled gun systems on future battlefields that are
about 70 years old in design concept.
“It’s a high-risk technology, but with a high pay-off
if it is done correctly,” says David. “The MOD wants to
see an EM weapon system that we can use on the battlefield in 20 years
time."
How does it work?
Rail or EM guns have only one moving part – the armature, which
drives the projectile. They consist of the following components:
Rails
These usually consist of thick copper bars, but can be made of any conductive
material. Running parallel to one another with a gap between them to
fit the armature, these rails have to conduct very high currents (MAmp
and higher) and must be braced against tremendous electromagnetic forces.
Armature
The armature, which drives the projectile, closes the electromagnetic
loop between the rails and is forced along their length at extremely
high speed. The armature can be a solid piece of conductive metal, a
conductive sabot housing a dart or sub-calibre penetrator, or a metallic
plasma for very high velocity shots.
Power supply
Rail guns require tremendous currents to fire a projectile at great
speed. Typically, the current used in medium-large calibre rail guns
is in the millions of amperes, while the duration will be less than
10ms. Maintaining a high current as long as possible increases the amount
of energy input to the projectile.
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