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| Last
Updated: Sun Aug 29 16:43:38 UTC 2010
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Hardening
RAAF Air Base Infrastructure
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5th February, 2008
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by
Dr Carlo Kopp
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| ©
2008 Carlo Kopp |
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Andersen
AFB at Guam. The absence of modern hardening measures, no differently
to RAAF basing in the north of Australia, presents a major
survivability issue for this base in any escalated contingency (US Air
Force image).
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The proliferation of large quantities of
precision guided munitions, including cruise missiles capable of air
and submarine launch, has changed the regional strategic calculus. Most
nations will be equipped with a robust capability to attack air bases,
and may have the option of surprise pre-emptive attacks.
Historical experience shows that attacks on air bases can be highly
profitable in terms of inflicting attrition on an opponent's air
assets. No matter how survivable a combat aircraft might be, on the
ground it is
as vulnerable as any other soft target. Operation Bodenplatte in
1944/45, the Israeli Six Day War
and Desert Storm are all
good examples
of how exposed aircraft become inviting targets, and subsequently,
scrap metal.
The problem of base hardening is one which has not been addressed in
the Australian defence debate to any great extent in the past. While
some very good theoretical work has been done in Australia, it has not
been
reflected strongly in planning. Dispersal areas and redundant taxiways
have been employed for recently constructed bases such as RAAF Curtin.
Unfortunately, the proliferation of smart bombs and cruise missiles
across the region, many with precision guidance capabilities, much
reduces the effectiveness of dispersal in base hardening.
Evolving Airbase Hardening
Measures
The established philosophy of 'classical' airbase hardening developed
during the Second World War, when both the Allies and Axis at various
stages of the conflict were able to bring the full might of their heavy
and medium bomber forces, and fighter bombers, against their opponents'
airfields. As these aircraft were armed with dumb bombs and guns of
varying calibres, experience soon showed that direct hits on parked
aircraft would be mostly produced by dive bombing or low altitude
strafing or rocket attacks. Given the accuracy of dumb bombs aimed by
gyro stabilised optical bombsights, dropped from medium or high
altitudes, direct hits on parked aircraft were the exception rather
than the rule for this regime of attack. Dive bombing and strafing thus
became the techniques of choice for dealing with airfields.
The revetment evolved as a defensive measure in this environment,
typically involving the construction of a U-shaped berm using earth,
sandbags, rock or other available materials. The revetment served
several useful purposes:
- Protection of parked aircraft against spall, shrapnel,
exploding gun ammunition and debris produced by contact fused bombs
impacting in the near vicinity.
- Protection of parked aircraft against shallow dive bombing,
low level strafing
and rocket attacks, where the berm was high enough to conceal the
aircraft entirely.
- Containment of damage effects when the aircraft in the
revetment was hit, thus preventing fratricide damage of other parked
aircraft.
These advantages have seen the classical revetment with earthwork berms
widely adopted since then. Refinements evolved, including where space
permitted the placement of additional berms or concrete structures to
block the line of sight into the entrance of the revetment.
Minimal
revetting is used to protect these F-15As during a 1980s exercise (US
DoD).
The advent of nuclear bombs complicated matters considerably. While a
revetment would protect an aircraft from some of the overpressure and
flash effects of a nearby nuclear event, that protection was not
entirely good enough.
If the the nuclear weapon was airburst at low altitude, or surface
burst, the high velocity shockwave would often be powerful enough to
suck the aircraft out of the revetment and wreck it. If the weapon was
airburst at a sufficiently high altitude, a line of sight path may have
existed between the bomb and the parked aircraft, resulting in ignition
or burn damage, as well as shockwave damage.
Revetments became increasingly displaced by Hardened Aircraft Shelters
(HAS). The HAS is a concrete or combined concrete and earthworks
structure which wholly protects the aircraft from blast, flash and
other weapons effects. Construction techniques and hardness vary
widely. HAS built solely for defence against nuclear attack would be
built to withstand some nominal blast overpressure consistent with a
nuclear weapon yield in kilotonnes/Megatonnes and some nominal miss
distance, consistent with an opponent's delivery system. The most
elaborate shelters were further equipped with door seals and filtered
ventilation to protect personnel from nuclear fallout effects. This
would allow the ground crew, alert pilot and aircraft to 'sit out' a
nearby nuclear strike until outside radiation levels declined to the
point where the aircraft could be safely sortied again.
PLA AF Quzhou AB in the
Nanijing MR.
Quzhou is atypical insofar as the revetments in the dispersal area are
connected by a full arc of taxiway, requiring multiple 'cuts' by an
attacker to close the taxiway. The revetment pads of typical PLA
airfields are 75 to 100 ft in diameter and can accommodate up to three
Farmer, Fantan or Fishbed fighters. Dispersal taxiways are typically 45
ft wide. At least one Badger base has pads sized to fit a single
aircraft, but no berms were installed. It is worth considering that the
PLA's approach to the construction of semi-hardened and hardened basing
closely follows the Soviet Cold War model, exemplified by former
Frontal Aviation bases in East Germany such as Grossenhein, Templin-Gross (note the auxiliary dispersal alert runway), Altenburg-Nobitz, Tutow-Demin, Brand, Welzow,
Damgarten, Wittstock, Eberswalde-Finow, Zerbst, Hinsterwalde, Juterbog, Merseburg, Rechlin and Sperenberg. For comparison, Ramstein AFB in West Germany (US DoD).
This pair of
J-8Is most likely belong to
the 16th Air Regiment, 6th Fighter Division, based at Yinchuan in the
Lanzhou MR. Yinchuan is one of several 'superhardened' PLA-AF bases
(PLA).
The PLA-AF fighter base at
Feidong in the Nanjing MR [Click
for more ...] is a good example
of the design of a
'superhardened' fighter base. The primary runway , available for
takeoffs and landings, has a wide full length parallel taxiway to
enable
recoveries in the event of damage. An auxiliary take-off only alert
runway is directly connected to the underground hangar entrance,
allowing the fighter to roll out of the tunnel, line up, open the
throttles and take off quickly. The PLA invested considerable thought
into planning its network of 'superhardened' fighter bases, usually
placing the runways behind a hill or mountain, relative to the threat
axis. Another good example of such a base is at Yinchuan [Click for more ...] in the Beijing MR. While modern smart
weapons have diminished the effectiveness of such base designs, they
still present genuine challenges in targeting and achieving robust
weapons effects (US DoD).
Where the HAS was considered inadequate, inventive military engineers
sought to construct complete hangars underground. The Warsaw Pact, the
Swiss, the Chinese and the Taiwanese have invested heavily in such
designs. Arguably the most numerous and elaborate arrangements were
constructed by the PLA in China, these including concrete structures to
protect blast doors, and auxiliary take-off only runways, which doubled
up as recovery taxiways, to enable scrambling fighters to get to the
runway threshold seconds after rolling out of the main entrance. Many
such 'superhardened' bases remain in use, especially in China and
Taiwan.
While protecting aircraft, personnel and critical support equipment was
a priority in the base hardening game, these components of a unit were
not the only vulnerabilities a base might have. Runways and taxiways
are inherently exposed and thus also attractive targets. Because
runways and taxiways can be rapidly repaired given adequate earthmoving
machinery, personnel, and materials, most targeteers regard damage
inflicted to runways and taxiways to be temporary, and will plan to
reattack frequently enough to keep an airbase closed. In the battle for
the control of the air, an initial play would be to cut runways and
taxiways to bottle up aircraft in shelters or revetments, with
subsequent sorties planned to pick off the stranded aircraft.
Mindful of this military engineers soon evolved techniques to make this
strategy difficult to execute. Redundant runways, the use of longer
runways than otherwise required, the use of taxiways as auxiliary
runways, and variously redundant taxiway schemes were adopted. Mostly
the aim of these was to force an opponent to deploy a much larger
number of munitions to effect a shutdown of flying operations at such a
base.
Other techniques to harden airbase surfaces included the use of
specialised concrete compositions, which would include aggregates or
additives to increase the toughness of the concrete, making it harder
to fracture even with a specialised runway busting munition. The
Soviets used blast furnace slag extensively for high strength concretes.
The fuel infrastructure of an airbase is another potential
vulnerability. If an attacker can destroy the fuel supply, and
associated plumbing, that alone might be enough to render a base
unusable.
The defender's play varies, from concrete walled above ground storage,
to buried fuel storage with varying depths of concrete roof and soil
above. Underground fuel storage can be expensive, as the cost scales
almost directly with the thickness of the tank roof and soil layer
above it. Suffice to say multiple redundant fuel tanks of smaller
capacity are invariably more survivable than smaller numbers of larger
tanks.
While aircraft, personnel, support equipment, surfaces and refuelling
infrastructure are the primary targets an attacker will pursue, they
are not the only targets. This in turn has seen hardened bases gain
shelters or bunkers for munitions storage, as well as for critical C3
elements at a base.
By the end of the Cold War many nations had constructed a considerable
number of well hardened bases, designed to be almost impregnable to
attacks using dumb bombs, rockets, aircraft cannon, or to attackes
employing nuclear weapons, if not hit directly.
The late 1960s however saw the emergence of a new weapons technology,
for the first time used in significant numbers. The technology was the
Precision Guided Munition (PGM) or 'smart bomb', a technology initially
dominated by television or contrast lock guided weapons, and laser
guided weapons. First deployed during the Second World War, guided
bombs soon wrought havoc upon North Vietnam's basic infrastructure.
Reinforced concrete structures which could withstand dozens of near
misses by even very large bombs, collapsed when hit directly by a
precision guided bomb.
While the US Air Force
successfully destroyed around 375 of Iraq's 594 HAS during the Desert
Storm campaign, typically at least two 2,000 lb BLU-109/B warheads were
required per target for this purpose (US DoD).
PGMs vs Hardened Shelters
While the advent of PGMs, specifically the Laser Guided Bomb, produced an
enormous impact on the ability to precisely hit targets per sortie,
this did not necessarily translate into hard kills against well
hardened targets. Many structures, such as command bunkers and HAS,
were built to withstand significant overpressure effects from nuclear
near misses. A key limitation during this period was a propensity for
the thin shelled Mk.80 series bomb casings to fracture on impact and
fail to penetrate the reinforced concrete. A large number of hits might
then be required to produce effect - if any. This was much the problem
encountered by the RAF and USAAC during the 1940s CBO in Europe, and
led to the Barnes Wallis designed Tallboy and Gland Slam bunker busters.
The US Air Force in 1985 sought to rectify this by initiating
development of the new I-2000 Have Void warhead, which eventually
became the BLU-109/B of Desert Storm fame. The new weapon had a
cylindrical hardened steel casing with a tungsten tipped ogival
nosecone, and tail mounted FMU-143 fuse. It is claimed to be capable of
penetrating 6 ft of reinforced concrete. Lockheed Missiles & Space
Company and National Forge Company were contracted to develop and
manufacture the 2,000 lb class weapon. The narrower casing and thicker
walls resulted in a lower volume of explosive filler, with only 550 lb
of
PBNX-109 employed. In 1991 the BLU-109/B was extensively used by the
F-117A force, usually with the Texas Instruments GBU-27 (modified
GBU-24) guidance kit. The weapon proved highly effective against HAS
and other bunker targets. Many targets however were so well hardened
that two rounds were required to effect a kill, the first to break into
the concrete and the second to fly down the hole so produced and
penetrate inside the cavity.
An F-111F of the
431st TES based at
McClellan AFB in California, carrying the first GBU-28 test drop
article
to the Tonopah test range, in February, 1991. Only two USAF types were
cleared to carry the weapon at that time, these being the F-15E and
F-111. The weapon weighs 4,700 lb (2,130 kg) and is over 19 ft (5.8 m)
in length (TI).
Deeper targets were engaged with the deep
penetrating 5,000 lb class GBU-28 "Deep Throat"
weapon, equipped with the BLU-113/B warhead.
Since then the US has developed the derivative thermobaric BLU-118/B,
using a BLU-109/B casing filled with a thermobaric incendiary
filler charge. When initiated, the thermobaric filler would combust all
of the oxygen in the target cavity, heating it to a high temperature in
the process. While initially developed for attacking biological and
chemical weapons storage bunkers, the weapon proved very useful in late
2001 attacks against Taliban cave complexes.
The 1980s BLU-109/B has been
used extensively, both with the GBU-24/27 LGB kit and the GBU-31(V)3
JDAM (upper) kit. A GBU-109/B casing with a thermobaric filler (lower)
is a BLU-118/B (US DoD).
Damage
effects to a hardened shelter at Al Jaber in Kuwait, and the
personnel and aircraft responsible.
The legacy BLU-113/B warhead is now being replaced with the more lethal
BLU-122/B,
which entered production in 2005/2006. The BLU-122/B has a new
nosecose, new explosive filler, different internal casing geometry, and
was tested against 18 ft thick reinforced 5000 psi (34.5 MPa) rated
concrete.
The
BLU-122/B (above) replaces the BLU-113/B.Sled test of the BLU-122/B
(below).
The replacement for the legacy BLU-109/B is the new 1,922.8 lb
BLU-116/B Advanced Unitary Penetrator (AUP), designed to double the
penetration capability of the BLU-109/B. The much thicker 2.26 inch
BLU-116/B casing uses high toughness Air Force 1410 nickel-cobalt steel
alloy, and a much smaller 10.7 inch diameter than the 14.6 inch
BLU-109/B, as well as a new optimised nose shape. An external
lightweight aluminum aerodynamic shroud is used to shape the exterior
and balance of the round to that of the BLU-109/B, so as to make it
compatible with existing bomb kits. The smaller enclosed volume results
in only 240 lb of PBXN filler. The BLU-116/B is claimed to penetrate
either 8-12 ft of reinforced
concrete or 100 ft of soil.
The
subcalibre BLU-116/B (above) replaces the BLU-109/B.The sheetmetal
external shroud provides compatibility with GBU kits designed for the
BLU-109 series.
The 1990s saw extensive use of cruise missiles to perform punitive
raids, and this in turn led to the demand for a penetrating warhead
suitable for a range of stand-off weapons. The WDU-42/B or J-1000
warhead, in the 1,000 lb class with a 240 lb AFX-757 filler, was
developed for the AGM-154 JSOW and the AGM-158 JASSM. The AGM-86D/E
Block I/III CALCM is equipped with the Lockheed-Martin designed 1,200
lb AUP-3M (Advanced Unitary Penetrator) claimed to be capable of
penetrating 12 ft of reinforced concrete, this warhead being derived
from the BLU-116/B. The latest Raytheon RGM-109H Block IV
Tactical Tomahawk Penetrator Version (TTPV) is fitted with an ARC
manufactured 1,000 lb WDU-34/B penetrator warhead.
Boeing
AGM-86C/D ALCM Block II terminal attack. This weapon is fitted with the
1,200 lb APU-3M penetrator (US DoD).
The most recent penetrating warhead to be introduced operationally is
the TAM Garland manufactured 208 lb design in the new GBU-39/B Small Diameter Bomb, sized so that 8
rounds fit into the weapon bay of the F-22A Raptor (it is worth noting
that an F-111G could be fitted with up to 40 SDBs). With 50 lb of a new
high energy explosive filler, this weapon is designed to provide the
lethality, against many targets types, of the legacy Mk.84 and
BLU-109/B. Designed with a long and small diameter casing, the bomb is
geometrically much closer in shape and form to a traditional armour
piercing discarding sabot subcalibre tank gun round. As a result it is
claimed to match the penetration capability of a BLU-109/B ie around 6
ft of reinforced concrete.
A unique feature of the SDB is its Optimal Guidance, which is designed
to align the
bomb body exactly with the weapon's velocity vector at the point of
impact, as this maximises penetration of the target. All of the
bomb's kinetic energy is used to drive the weapon in - older guidance
systems did not achieve this and velocity components tangential to the
impact would at best waste energy, at worst contribute to premature
casing rupture.
It is interesting that the literature on
armour piercing discarding sabot subcalibre tank ammunition design
stresses that projectile length and density are the greatest
determinants of its ability to punch through armour. This is termed
area density (ie warhead weight / cross-sectional area), the higher the
better from an attacker's perspective.
Reinforced
Concrete penetration by GBU-39/B SDB (US DoD).
| Penetrating
Warheads |
Designation
|
Mass
[lb]
|
Filler
[lb]
|
Guidance
Kit / Munition
|
Penetration
Performance
|
| BLU-109/B
Have Void |
~2,000
|
PBNX-109 |
GBU-24,
GBU-27, GBU-31 JDAM
|
6
ft
reinforced concrete
|
BLU-116/B
AUP
|
~2,000 |
AFX757/PBXN-110
|
GBU-24,
GBU-27, GBU-31 JDAM |
8-12
ft
reinforced concrete |
| BLU-118/B |
~2,000 |
Thermobaric
|
GBU-24,
GBU-27, GBU-31 JDAM |
6
ft
reinforced concrete |
| BLU-113/B |
~5,000
|
Tritonal
|
GBU-28/EGBU-28
|
Undisclosed |
BLU-122/B
(BLU-113 PPI)
|
~5,000
|
AFX757/PBXN-110
|
EGBU-28C/B
|
18
ft
reinforced concrete |
SDB
|
~208
|
Undisclosed
|
GBU-39/B
Small Diameter
Bomb
|
6
ft
reinforced concrete |
| WDU-42/B
/ J-1000 |
~1,000
|
AFX-757
240
lb |
AGM-154
JSOW, AGM-158 JASSM |
Undisclosed |
| WDU-34/B |
~1,000 |
Undisclosed |
RGM-109H
Block IV TTPV |
Undisclosed |
| AUP-3M |
~1,200 |
AFX757/PBXN-110 |
AGM-86D/E
Block I/III CALCM |
12
ft
reinforced concrete |
KAB-500
|
~840 |
Undisclosed |
KAB-500Kr/L/S/S-E |
Undisclosed
penetration/blast
|
KAB-1500
|
~2,450
|
Undisclosed |
KAB-1500L-Pr
|
30
ft soil +
6 ft
reinforced concrete |
Table
1. US and Russian Penetrator Warheads.
While the US has dominated the design of penetrating bombs in recent
years, others have
also contributed technology. The UK developed the two stage BROACH
warhead, which uses a precursor shaped charge to bore a hole through
the outer layers of the hardened structure, into which the penetrator
proper then enters, milliseconds later.
The Russians have disclosed the existence of a subcalibre penetrating
warhead for the large KAB-1500
series guided bombs, available with semi-active laser homing,
electro-optical correlator or datalink, and GPS/Glonass inertial
guidance kits. The smaller KAB-500
series is, with the exception of the fuel air explosive armed
KAB-500Kr-OD variant, always equipped with a blast penetration warhead,
but it is not specifically built as a deep penetrating bunker buster
like the KAB-1500L-Pr warhead.
The longer term outlook is that the US will continue to refine its
current inventory of penetrator warheads, as these largely span the
full range of US PGMs. The Russians are likely to develop further
warheads, to fill the niches currently not covered by the existing
KAB-500 and KAB-1500X-Pr penetrators. There will inevitably be demand
as major Rosoboronexport clients appreciate the extent to which their
opponents have hidden under concrete, and US manufacturers have shown
that such warheads can be designed and mass produced. Russian industry
has excellent metallurgical and metal fabrication skills and there is
no reason to believe that they could not design and build an 'AUP-ski'
or 'BLU-122-ski' if so tasked.
KAB-500Kr
Electro-Optically Guided Bomb
KAB-500L Laser
Guided Bomb
KAB-500S
Glonass/GPS/inertially guided bomb a.k.a. "JDAM-ski". The 24 channel
receiver is capable of tracking US Navstar GPS and Russian Glonass
vehicles, and has a differential and carrier phase GPS capability to
enhance accuracy.
KAB-1500Kr
Electro-Optically Guided Bomb, live round (upper), training round
(lower).
KAB-1500L
Laser Guided Bomb
KAB-1500L-F
with blast fragmentation warhead (upper) and KAB-1500L-Pr with
penetrator warhead (lower).
Top to bottom, the KAB-500Kr,
KAB-500L, KAB-500S,
KAB-1500TK/Kr, KAB-1500L. The KAB-500 and
KAB-1500 family of guided bombs are direct equivalents to the US
Paveway II/III and GBU-15 family of weapons, and have been cleared on
the Su-30MK and some Su-27SK variants (Rosoboronexport).
Hardened Shelters vs PGMs
While the BLU-109/B and BLU-113/B were widely regarded to
be a stunning success in 1991, accounting for hundreds of targets
including well hardened HAS, the reality is that many of these targets
required multiple hits to penetrate. An attack would see a pair of
GBU-24 or GBU-27 pickled with a fixed delay, so that the second round
would fly into the hole produced by the first round. Effectively the
first round acted as a precursor to expose the inner layers of the
shelter carapace, so that the second round could punch through.
The penetration performance of any such warhead depends not only on the
warhead design features and impact velocity/angle, but also on the
strength and thickness of the
reinforced
concrete or other materials used in the construction of the bunker or
shelter.
The design of high strength and hardness concrete materials is a
science, and not a trivial one either. The concrete composition has a
critical impact on its properties, and high strength concretes
frequently include additives such as blast furnace slag, fly ash, and
sometimes aggregates including very hard materials such as quartz.
Tensile strength can be further improved by adding metal wire or
whiskers into the mix, graphite fibres or glass fibres. The thickness
and type of steel
used for the
reinforcement mesh will also influence the strength of the material.
For comparison typical concrete strengths used in US evaluations of
penetrating warheads are 5,000 psi (~35 MPa) and 10,000 psi (~70 MPa),
yet many commercial high strength construction
concretes provide 13,000
psi (~90 MPa) to 18,000 psi (~124 MPa).
Penetrators impacting on concrete typically cause catastrophic
delamination and separation of the concrete from the reinforcement
mesh, allowing the projectile to punch its way through. For a
reinforced concrete to provide high resistance to a penetrating
projectile, it must be tough in the sense that it does not disintegrate
or fracture when the shockwave produced by the projectile propagates
through the material.
A century ago long range firepower was delivered by large calibre guns,
the biggest typically being in the 11 inch to 16 inch category. These
were typically rail mobile or casemated artillery pieces, guns on large
warships and coastal defence gun batteries. Such weapons remained as
the primary armament of battleships /
battlecruisers and a range of fortifications until the late 1940s.
What is of interest is that the projectiles fired by these weapons were
1,800 to 2,800 lb in weight, made of high quality hardened steels, and
usually cylindrically shaped with an ogival nosecone. In other words,
they were not much different in terminal velocity (~500 m/s), shape,
size and weight to contemporary large air delivered penetration. Refer
Table 2.
Projectile
|
Weight
[lb]
|
Diameter
[in]
|
Penetration
Performance |
BLU-109/B
|
1,950 |
14.5 |
6
ft
reinforced concrete |
16"/50
Mark
7 - AP Mk.8 (Iowa class BB)
|
2,700 |
16.0
|
30
ft concrete
|
40
cm/45 Type
94 - APC Type 91 (Yamato class BB)
|
3,219
|
18.1 |
Unknown
|
Table
2. Comparison of BLU-109/B vs 1930s US and Japanese Battleship Gun
Projectiles.
What is of no less interest is that considerable effort was invested
into the design not only of armour plating for warships, but also
armoured concrete structures for casemats, forts and other bunkers
associated with defensive gun batteries. Good case studies of the
latter include the well known French Maginot Line of fortresses, with
multiple metres of concrete often capped with steel [1].
What this shows is that designers of bunkers and HAS have a larger
repertoire of technologies available to them than might be immediately
apparent. For instance cast iron or steel slabs of suitable thickness
placed over a
reinforced concrete structure would likely frustrate all but the most
capable penetration warheads. No differently, advanced concretes can
drive up the required mass of a penetrator to the extent that many
basic 1,000 lb class weapons would be ineffective.
Understandably, no matter how good a HAS or bunker might be, a
penetrating projectile can be built to defeat it. From a strategy
perspective what matters is the effort required to defeat such a
shelter or bunker.
A smart strategic planner will identify which delivery systems are
cheaper vs which are more expensive, and harden to defeat all but the
most expensive means. In turn this renders most of an opponent's means
ineffective, forcing the use of expensive and scarce assets.
Let us consider a scenario where a defender wishes to frustrate the US.
The strategically cheapest delivery system the US has is the cruise
missile, which permits punitive raids without the exposure of combat
aircraft. Cruise missiles are typically limited to a 1,200 lb class
penetrator, so hardening to defeat the new AUP-3M series and J-1000
would render these weapons ineffective, forcing the use of a B-2A armed
with a BLU-122/B, or forcing a major aerial spat to allow the F-15E to
penetrate carrying the same weapon. The overall cost to the attacker is
thus driven up considerably. Making the structures resistant to larger
weapons in turn makes an attack even more expensive in resources.
If a cruise missile penetrating warhead must have a 2,000+ lb mass to
produce effect, the generic 3,000 lb class cruise missile must be
replaced by a 6,000 lb class cruise missile, in turn constraining
delivery systems and again driving up costs.
A key consideration now for Pacrim strategic planners is that the
Russians are exporting the KAB-500/1500 series, and thus this category
of penetrator could be used at any time. Moreover, cruise missiles have
become a very popular weapon in the Pacrim, and thus an available
delivery system for an 800 to 1,200 lb class penetrator warhead is
becoming widely available. Indeed
it would be naive to assume that an "AUP-3M-ski" in this class will not
appear over the next decade.
Given current propulsion technology, cruise missiles with standoff
ranges in the 200 NMI to 700 NMI class will be limited to warheads in
the 800 to 1,200 lb class. A larger and deeper penetrating concrete
piercing warhead at given missile launch weights results in a shorter
ranging missile which in turn increases the exposure of the delivery
system, and thus risk to an attacker.
A good case study would be a
2,000 lb class penetrator fitted to a Kh-22
Kitchen, Kh-41 Moskit/Sunburn, 3M54E Club/Sizzler or Kh-61
Yakhont/Brahmos class
supersonic
cruise missile - an attractive class of delivery system due to the high
terminal velocity of the vehicle - such a weapon would be limited to a
range of around 250 NMI [2].
Supersonic ASCMs present as
attractive delivery vehicles for subcalibre concrete piercing warheads,
as the Mach 2+ terminal velocity at impact increases kinetic energy 7.5
to 11 fold compared to a conventional "Tomahawk-like" subsonic cruise
missile. Upper depicts the Novator 3M54E Sizzler, which launches a Mach
2.7 rocket propelled guided warhead section, lower depicts a notional
adaptation of the Mach 2.2 3M81 / Kh-41 Sunburn. Both missiles have
been marketed across the region, and both will be available in air
launch and naval variants.
Any current hardening measures applied to structures such as bunkers,
HAS, underground fuel storage, munitions storage etc should be
designed, at a minimum, to defeat a 1,000 lb class penetrating munition
in the class of the AGM-86D AUP-3M, this warhead being a reasonable
benchmark for regional standoff delivery capabilities over the coming
decade. The best case delivery vehicle would be a KAB-1500 or subsonic
cruise missile such as a 3M14E Sizzler, Kh-55SM Kent or YJ-62, the
worst case a supersonic cruise missile such as the Kh-41 Sunburn, 3M54E
Sizzler or
Kh-61 Yakhont.
Hardened Shelters vs
Electromagnetic
Weapons
The emergence of electromagnetic weapons such as non-nuclear low frequency EMP bombs, and microwave
bombs, the latter exploiting now rapidly evolving High Power
Microwave (HPM) source technology, presents a very serious risk to
modern high technology weapon systems.
During the Cold War key items of nuclear warfighting technology and
infrastructure were well hardened against nuclear EMP attacks. Since
then two trends have progressively changed the operational environment:
- Digitisation, networking and the large scale insertion of
non-hardened COTS technology computing and networking equipment has
made many modern systems highly vulnerable to EMP and HPM damage.
- Electromagnetic weapons technology has shifted from the
nuclear warfighting domain into the conventional weapons domain, thus
dramatically lowering the strategic threshold for the use of such
weapons.
For an attacker aiming to disable an airfield and the assets sited
there, electromagnetic weapons offer the choice of crippling or
electrically destroying targets with a much smaller number of munitions
compared to the conventional alternative of cracking open multiple HAS.
A
wide range of available munitions could be readily adapted for HPM
payloads (Author).
The simplest approach to hardening against EMP and HPM threats is to
enclose the vulnerable equipment in a Faraday
cage, which shields it from exposure. The 'traditional'
technique for constructing these would involve cladding the internal
walls, or embedding within the walls, of a structure an electrically
conductive mesh using for instance copper wire. Needless to say for a
structure the size of a larger HAS, this can become quite expensive to
implement.
Technology has however progressed since the Cold War period, and a
range of electroconductive concrete products are now available in the
market. These materials when applied in suitable thickness have been
employed not only for electromagnetic shielding, but also for
electrical heating - the whole conductive volume of the concrete
becomes a resistive heating element.
The practical consequence of this is that converting a HAS into a
Faraday cage becomes much cheaper. While it will still be necessary to
invest in suitable seals for the main doors and other access points,
the large expense of producing a durable shielding surface inside the
enclosure will be significantly reduced. Moreover, as the shielding is
bulk material, it will be feasible to effect much better
electromagnetic shielding, across a wider range of wavelength, compared
to mesh technology. In effect the structure of the shelter becomes an
integral Faraday cage [3].
While EMP and HPM payloads represent the primary risk to airfields and
parked aircraft, the increasing power levels produced by recent
multimode X-band radars in combat aircraft will present a risk all of
its own. With feasible damage effects at hundreds of metres of
distance, a combat aircraft flying a low altitude pass over an airfield
could use its radar to inflict electrical damage. The recently revealed
Tikhomirov NIIP Irbis E radar qualifies in this category [4].
Other Threat Considerations
While PGMs with penetrating and electromagnetic payloads represent the
primary threat against aircraft on the ground, other threats do exist
and have presented risks in the past.
Special Forces units penetrating airfield perimeters have been used to
inflict damage. Perhaps the best example are British SAS operations
against the Argentinians in 1982, and the aborted Mikado
raid, and subsequently aborted submarine
insertion. These present good examples of the use of SF to cripple
an adversary's assets. It is well documented that the Soviet Spetznaz
were tasked with a similar role to hobble NATO's air power in the event
of a NATO-Warpac conflagration. The VC and NVA mounted several
successful raids during the Vietnam conflict [5].
The most common approach currently followed to dealing with the problem
of ground assaults and raids against air bases is the deployment of air
field defence ground troops, if necessary supplemented by infantry and
armed base personnel.
The difficulty this approach presents is that an often very large
footprint must be defended, moreso if the attacker has mortars, wire or
command link guided rockets, RPGs, large calibre sniper rifles, or
other "standoff" anti-materiel weapons.
Placing aircraft into hardened shelters minimises exposure to times
when the aircraft are taxiing, which makes them much harder to hit.
Also, hardening fuel and munitions storage frustrates this regime of
attack.
With the ongoing Global War On Terror another risk which arises is that
of terrorists attacking basing to produce propaganda effect - nothing
captures public attention better than TV footage of burning aircraft on
aprons.
It inevitably follows that hardening measures cover a much wider range
of threats than PGMs.
The advent of cruise missile
technology, air and submarine launched, across the region changes the
strategic calculus. Pre-emptive attacks against exposed airfields
become viable and potentially very effective. The images depict trials
of the RGM-109C Tomahawk against a revetted RA-5C Vigilante (US Navy).
Hardening RAAF Bases
The very limited hardening and passive defensive measures applied to
RAAF bases in the north are a product of the regional capability
environment of more than a decade ago, when PGMs were scarce or absent
in regional inventories, and standoff or cruise missiles operated only
by the US and Soviets. The region is now a very different place, and
the RAAF's northern basing can be considered, for all intents and
purposes, naked if subjected to a pre-emptive attack using cruise
missiles or other PGMs.
In strategic terms, given the small size of the RAAF combat fleet,
attrition in combat is not an option to be seriously considered.
Hardening the basing infrastructure with lots of concrete is much
cheaper than replacing
billions of dollars of slow to replace hardware.
In terms of priorities, RAAF Tindal, Darwin and Learmonth are the
highest priorities, as they are in the strategically most important
locations, and have the best runways making them more useful in a
contingency than the gapfiller bases at Curtin and Scherger.
With advent of cruise missile capabilities across the
Asia-Pacific-Indian region, early interception becomes a key priority,
and this drives up the strategic importance of the Cocos Islands
runway, and the Christmas Island runway, primarily as diversion sites,
but also as additional Forward Operating Bases (FOB).
Over the next decade Australia will thus have to properly develop and
harden its northern airbase infrastructure if it intends to use these
sites in a real contingency.
Hardening of Australia's northern bases involves a number of specific
measures:
- Runway improvements to provide at least one 10,000 - 12,000
ft length runway for each base. This is required to accommodate the
full spectrum of aircraft types, including tankers and heavy airlifters.
- Runway surfaces will need to be rated to PCN 100 to 150 so
as to provide durability with repetitive use by heavy aircraft, and
also to provide damage tolerance.
- Each base requires a 10,000 to 20,000 tonne capacity
hardened concrete underground fuel storage farm (for instance multiple
cylindrical 2,000 tonne tanks)
- Bases located at coastal sites will require an offshore
fuel loading jetty or seabed pipeline to permit rapid replenishment of
aviation fuel supplies. Tindal will require provisions for
replenishment by rail from Katherine.
- Redundant hardened munitions bunkers with redundant access
roads will be required.
- A buried hardened command bunker for C3, ops, and ATC.
Underground air raid shelters should be constructed for other areas of
each base.
- Wagon wheel and other redundant taxiway arrangements
should be introduced, where not extant.
- Hardened Aircraft Shelters capable of resisting at least a
bunker busting 1,000 lb class supersonic cruise missile warhead in the
class of
the AUP-3M will be required not only for fighter aircraft, but also for
KC-30 tankers, C-17s, Wedgetails,
AP-3C/P-8 LRMPs and other large aircraft. This does offer the added
benefits of denying satellite recce visibility and protecting the
aircraft from the harsh
environment.
- The recent emergence of electromagnetic pulse (EMP) and
microwave (HPM) weapons requires that all shelters be hardened against
this form of attack.
- Concrete pads for the requisite number of tents or prefab
housing modules needed to support an extended deployment.
- Underground water and electricity distribution to
areas to be used to house personnel, redundant desalination plants and
electricity generation of necessary capacity. Sewerage facilities of
required capacity.
- A stormwater drainage system to handle monsoonal weather
conditions, including runways, taxiways, shelters, carports, concrete
housing pads, bunkers etc.
- Provisions should be made for the deployment of air defence
systems, especially search radars and defensive missile batteries.
There exist a large number of well hardened NATO and former Warsaw Pact
bases which can be used as templates for the design of a robust base
hardening package.
HAS
at Balad AB in Iraq (US DoD).
Conclusions
The advent of PGM technology in the region has rendered extant RAAF air
base hardening measures ineffective, opening up the strategic option of
a pre-emptive attack, especially using submarine or air launched cruise
missiles, against forward deployed RAAF assets at northern bases.
It follows that Australia should invest in a robust program to harden
all RAAF basing in the north, and apply like hardening measures in the
development of the Cocos Islands and Christmas Island.
Australian Industry and Research Organisations (e.g. CSIRO,
Universities) are at the leading edge of construction technologies
globally, and Australian research and industry innovations are held in
very high regard internationally.
It follows that Australian industry and researchers can make valuable
contributions to the development of new air base hardening
capabilities, which in turn could directly benefit coalition partners
and other allies of Australia.
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Reading:
- Lieutenant Colonel Thomas C. Blake, Jr., Improving the
Ground Survivability of In-Theater TACAIR, Air University Review,
September-October 1975, URL: http://www.airpower.au.af.mil/airchronicles/aureview/1975/sep-oct/blake.html.
- John Stillion, David T. Orletsky, Airbase Vulnerability to
Conventional Cruise-Missile and Ballistic-Missile-Attacks: Technology,
Scenarios, and U.S. Air Force Responses, RAND Corporation MR1028, 1999,
URL: http://www.rand.org/pubs/monograph_reports/MR1028/.
- Major David L. John, USMC, Airbase
Survivability/Recoverability Assessment, CSC 1989, URL: http://www.globalsecurity.org/military/library/report/1989/JDL.htm.
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Imagery
Sources: Author; Rosoboronexport; Russkaya Sila; Ugolok
Neba; MilitaryPhotos.net; Military.cz
Endnotes:
[1]
No less interesting was the development of guns and projectiles to
demolish such fortifications, the best example being the 1,329 ton
Krupp AG 80 cm (31.5 inch) calibre Gustav/Dora railway gun, which fired
a standard round of 4800 kg (10,600 lb) and a concrete penetrating
round of 7000 kg (15,500 lb), the latter heavier than the RAF Tallboy
bomb. This gun was developed specifically to defeat the Maginot Line
concrete and steel bunkers.
[2] Intermediate Range Ballistic Missiles in the 800 to
1,800 NMI range class are also popular in Asia now, and again present
an attractive delivery system for an 800 lb to 2,000 lb class
penetrating warhead, due to the accuracy afforded by GPS/Glonass
capabilities, and the high terminal velocity of the vehicle.
[3] The difficulty with using a mesh for shielding is
that the size of the holes in the mesh may be large enough for them to
pass microwave radiation in the centimetric and millimetric bands, even
if the mesh is 100% effective at greater wavelengths.
[4] C Kopp: Considerations on the use of airborne
X-band radar as a microwave directed-energy weapon, Journal of Battlefield Technology,
vol 10, issue 3, Argos Press Pty Ltd, Australia, pp. 19-25.
Refer also "Ирбис"
готовиться к прыжку - "Авиасалоны мира", №5, 2006,
стр.22-25 (Russian).
[5] Refer Vick A, Snakes in the Eagle's Nest: A
History of Ground Attacks on Air Bases, RAND Corporation MR553, 1995,
URL: http://www.rand.org/pubs/monograph_reports/MR553/.
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RAAF Northern Air Bases
[Click on base name for
satellite image ....]
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Imagery Supplement
(US DoD/US Air Force)
US Air Force 'Tab Vee'
Shelters
Kadena AFB, Okinawa.
Tab Vee at a NATO site.
EF-111A Raven at a NATO site in
1991.
F-4E Phantom at Ramstein,
Germany, 1980.
Unspecified location 1983 image.
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Shelter Attack by BGM-109C Tomahawk Block II
(Weapon trials in 1988)
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Desert Storm Bomb Damage Assessment
Al
Jaber, Kuwait.
Al
Salem AB, Iraq.
Al Salem AB, Iraq.
Al Salman AB, Iraq.
Al Salman AB, Iraq.
Al
Salman AB, Iraq.
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