RUGGED, light and virtually indestructible, the general purpose vehicle or
Jeep is a legend in US military history. Since the first model was built in
1940, the basic green machine has been ever present in the nation鈥檚 armoury.
But war has changed, and the Jeep is about to undergo a transformation to
bring it up to date. The new design, commissioned by the US Marine Corps, is
called the Reconnaissance, Surveillance and Targeting Vehicle (RST-V), and to
develop it the Marines have turned to the Defense Advanced Research Projects
Agency (DARPA), the research and development branch of the US Department of
Defense.
The project lays down some ambitious specifications. The new vehicle must
carry three or four marines on long-range missions into enemy territory. It must
travel at speeds of up to 100 kilometres per hour on ordinary roads and be able
to negotiate anything from sand dunes to peat bogs at about half that speed. And
it must be well enough armoured to shield its occupants from small arms
fire.
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Most difficult of all, the Marine Corps wants the whole package to weigh no
more than 4 tonnes and be compact enough to fit inside the small V-22 Osprey
vertical-takeoff transport planes that will shuttle the vehicle from mission to
mission. This limits the dimensions of the vehicle to about 1.6 metres wide and
1.7 metres high. It will be much smaller than the RST-V鈥檚 closest relative, the
Highly Mobile Multiple Wheeled Vehicle or HMMWv, otherwise known as the Humvee,
which saw action with American forces in the Gulf War. 鈥淵ou鈥檙e trying to make a
fairly small package hold and do a large number of different jobs,鈥� says Arthur
Morrish, the programme manager at DARPA.
A feature of the RST-V design is ahybrid electric power system, which uses a
diesel-driven generator to produce power for electric motors mounted on each
wheel. The design is lighter and far more compact than mechanical drive trains
that stretch from the engine to each axle. It also reduces fuel consumption and
provides built-in reliability: if one motor fails, the others will keep the
vehicle going. Even if the generator breaks down, the vehicle can run for short
periods on batteries. Best of all, batteries allow the RST-V to operate
stealthily, with no engine noise and no hot exhaust gases to give it away to the
enemy鈥檚 thermal sensors.
But there are problems powering a vehicle this way. The electric must be
computer-controlled to coordinate the acceleration, braking and drive system,
and this needs complex cabling and monitoring systems. Then there is the
question of what type of battery to choose. Lead-acid cells offer more power per
dollar than nickel metal hydride or lithium-based batteries. But they are also
heavier and wear out more quickly.
Battery design has improved by leaps and bounds in the last few years. Their
power density鈥攖he power produced by a battery of a given volume鈥攈as
trebled. And for vehicles using lead-acid batteries, recharge times have
plummeted from eight hours to a brisk nine minutes. The cost is falling too. The
most recently developed lead-acid cells cost around $125 per
kilowatt-hour, about a fifth of the cost of nickel metal hydride or
lithium-based batteries.
Just what the best combination will be remains to be seen but DARPA has no
shortage of test beds that it can use to find out. It has already designed
several hybrid electric vehicles, including a battery-aided cousin of the Humvee
called a Hummer.
Last December, the Pentagon also unveiled a diesel powered hybrid-electric
Humvee fitted with lead-acid cells. It is powered by four 75-kilowatt electric
motors that can take it from a standstill to 80 kilometres per hour in a
sports-car-like seven seconds鈥攖wice as quickly as its diesel-engined
cousin. The vehicle has some unusual features. Since the wheels run
independently, it can spin itself round without moving forwards. And when
running on battery power alone it can travel up to 30 kilometres while creating
virtually no heat or sound.
Hybrid electric vehicles are more fuel efficient than conventional
diesel-engined vehicles, which turn most of the energy stored in fuel into heat.
Morrish expects the RST-V to deliver between 1.5 to 2 times the fuel economy of
diesel vehicles. The partially electric Humvee tallied about 13 litres per 100
kilometres, twice the efficiency of standard models. This is an important factor
for a military force that uses around 100 million gallons of fuel a year. Even a
small increase in efficiency could make a significant saving.
Expanding suspension
The RST-V鈥檚 suspension system will also be novel. It has to be tough enough
to tackle the roughest terrain while protecting any sensors and computer
equipment on board. Moreover, the RST-V will have to be able to negotiate slopes
of up to 40 degrees. On a sideways slope this steep, a vehicle as narrow as the
RST-V鈥檚 specified 1.6 metres will topple over, because its centre of gravity is
too high, says Raymond Shaw of General Dynamics Land Systems, the manufacturer
that is building a prototype for DARPA. So GDLS is designing the RST-V to expand
like an accordion. It folds in, and once you drive out of the aircraft it folds
out, giving the vehicle a potential width of over 2 metres, says Shaw. This
extra width gives the vehicle the extra stability it needs.
Lastly, the RST-V will have to protect its occupants from enemy fire. The
conventional way of stopping rifle bullets is with metal armour plating. But
this would weigh down a small vehicle such as the RST-V. Carbon-fibre composite
plating and ceramic plates or combinations of them could provide the same degree
of protection while weighing only 20 per cent of full steel armour.
The new design is even attracting attention from outside the military. David
Uhrig, who owns a military surplus brokerage in Chillicothe, Ohio, says the
next-generation Jeep will be the most significant redesign in nearly 40 years.
The last time the military went back to the drawing board with such vigour was
when the Marine Corps commissioned the Mighty Mite. 鈥淚t was the ultimate Jeep,鈥�
says Uhrig, with reverence. 鈥淏ut because it cost four times as much as the Army
was paying [for another model], Congress killed the project after only 3140 were
built.鈥� In 1940, the original Jeeps cost $2500 each, equivalent to about
$30 000 today.
DARPA hopes to have two prototypes of the new Jeep to choose from by the end
of the year. Then Uhrig should find out just what kind of military surplus he鈥檒l
be selling in 40 years鈥� time.