Home' Defence Technology Review : DTR JUN 2016 Contents 35
DEFENCE TECHNOLOGY REVIEW | ISSUE 21 | JUN 2016
When the shortlisted Combat Reconnaissance Vehicles turn up for the Risk
Mitigation Activity later this year, no one should feign surprise at their imposing
size. It’s all in the requirements, explains James Walsh.
CRV - big for a reason
shifted to the European unescorted vehicle width limit (3m) and
the wing spar height in the cargo bay of a C-17A Globemaster III
heavy airlifter (3.6m).
When people who are not familiar with modern wheeled
armoured vehicles see one for the first time, they are surprised
by how wide and high they are. Their length is not normally
a surprise. An average car is less than 2m wide. An ASLAV is
2.6m wide. A CRV will be a smidgeon less than 3m wide (to keep
inside the European unescorted vehicle width limit). This does
not sound much of a difference but the waistline of the vehicle
sits considerably higher than an ASLAV so the impression is of a
vehicle at least half as big again.
The overall vehicle height is the main surprise for newcomers.
The turret roof of an ASLAV is 2.6m high. The overall height of a
CRV will be another metre higher again. This seems crazy at first.
But the maths is rudimentary. The overall height of 3.6m is the
sum of all the space claims needed to get from the ground to the
roof of the turret. To understand these, let’s start at ground level
and work upwards.
All armoured vehicles need ground clearance. Wheeled
armoured vehicles need more clearance than equivalent tracked
armoured vehicles to accommodate higher suspension travel.
Moreover, the simplest way to protect a vehicle from a bomb
detonating under the ground is to get away from it: to trade space
for protection. Every additional millimetre of ground clearance
means less energy delivered to the underside of the vehicle and
(based on Mowag’s Piranha 2). ASLAV protected its occupants
from small arms fire, was fitted with a medium calibre (25mm)
cannon, was still amphibious and capable of 500km journeys at
highway speeds of 100km/h.
Twenty years on, the requirements for the CRV are far more
demanding than for ASLAV. As DTR explained in the October
2015 issue, while the mobility of the CRV is roughly equivalent
to ASLAV (except that it is not amphibious), the lethality and
survivability are significantly higher. But lethality will not be the
main driver of size for the CRV. Survivability will be.
HIGH SURVIVABILITY MEANS BIGGER VEHICLES
The challenges are threefold. Protection levels keep getting higher
(as threats increase and multiply). Vehicle crews and dismounts
are required to carry more and more equipment. And the soldiers
themselves are getting taller and wider. These three factors all
mean bigger vehicles. It is important to understand that even
small increases in internal volume cause significant increases
in overall size, weight and cost. It is not a simple matter to add
another box of ammunition let alone another soldier to a vehicle.
On the other side of the ledger, various constraints prevent the
vehicles from exceeding certain dimensions and external profiles.
In the 1990s, most Western armoured vehicle programs required
transport in a C-130 Hercules medium airlifter. This restricted
the width, height and loading weight of armoured vehicles such as
the US Army’s Stryker. As protection requirements continued to
increase, this requirement was relaxed when it became clear that
armoured vehicles could not enjoy the required protection levels
and be kept under 20 tonnes and so the dimensional constraints
WHEN A BRITISH general climbed into one of the vehicles
competing for the UK’s armoured utility vehicle program (FRES
UV) in 2007, he announced to all and sundry that the British
Army would never buy such a big vehicle. He was obviously
surprised by its size. He shouldn’t have been. All three contenders
were of a similar size and for straightforward reasons.
As Land 400 Phase 2 began in earnest two years ago, there
were similar comments about the size of expected Combat
Reconnaissance Vehicle (CRV) contenders. Some commentators
at the time seemed confident that all of the requirements could
be fulfilled with a vehicle not much larger than the in-service
ASLAV. The larger vehicles in the global 8x8 market were widely
considered to be too big. The fact, however, is that the Land 400
requirements are some of the most demanding in the world. As
a result, the vehicles now competing for Land 400 Phase 2 are
among the largest in the world.
The laws of physics have not changed. Nor has anyone
discovered the armour material referred to by designers as
‘unobtainium’ which protects against all threats while weighing
and costing nothing. Nor does the development of armoured
vehicles obey Moore’s law: they are not halving in size and
doubling in speed every 18 months. But armoured vehicle
designers are still trying to make their vehicles as small as
possible. They do not increase the size of their vehicles, for
example, to improve aesthetic proportions or to make it bigger
than a competitor’s vehicle. This is not the US pick-up truck
market where vehicles are designed large to accommodate the
tastes of consumers. In the armoured vehicle world, there is no
prize for building the biggest target.
So what are the design constraints on a modern wheeled
ABOVE: Forward profiles of the in-ser vice ASLAV-25 flanked by
the AMV35 (left) and Boxer CRV (right). The growth in vehicle
width and height is a result of creeping customer requirements,
particularly that for increased protection.
Images: BAE Systems, DTR , Rheinmetall
BELOW: Graphic illustration of how protection design
requirements drive overall vehicle height. Image: DTR
armoured vehicle and why have they become as big as they are?
The origins of modern wheeled armoured vehicles can
arguably be traced to Mowag’s amphibious 4x4 vehicle known
as the Puma. This vehicle should not be confused with Iveco’s
diminutive 4x4 and 6x6 designs from the late 1980s, the relatively
new 4x4 protected mobility vehicle from South Africa’s OTT
or the current-generation German tracked infantry fighting
vehicle of the same name. Mowag’s Puma was little more than a
thin metal box that floated, propelled itself on land and in water
and prevented shrapnel only of the small and slow variety from
harming the occupants.
That was 1962. In the 50 plus years since, the descendants
of Puma have been asked to do more and more. Specifically,
protection levels have steadily increased, the number and lethality
of installed weapons has increased while the mobility has been
expected to stay roughly the same. As a result, vehicles have
become larger and larger. They have evolved from 4x4, to 6x6,
8x8 and even 10x10. Vehicle mass has increased from less than 10
tonnes to more than 30 tonnes.
As a signpost along the way, ASLAV is a classic and capable
vehicle from the early 1990s. The typical requirements increased
significantly between Mowag’s Puma vehicle and the ASLAV
400mm Height of appurtenances of
150mm Total thickness of roof protection
100mm Head clearance
150mm Survivability space claim
300mm Total thickness of mine
500mm Separation between bomb
and underside of vehicle
600mm Height of turret above hull roof
1400mm Vertical height of 95th percentile
male with boots and helmet
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