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Last
Updated: Mon Jul 7 11:57:52 UTC 2008
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Maritime
Strike using the F-22A Raptor
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A question which is frequently asked is how could the F-22A Raptor be
employed in maritime strike (ASuW) roles, given that its basic
air-ground weapons configuration is currently optimised for
fighter-bomber and lethal defence suppression roles (DEAD). Maritime
strike is an important role for Pacific Rim operators, such as PACAF
and Australia.
There are no fundamental
impediments to the integration of an external anti-shipping missile,
carried on the F-22A's wing pylons. Given that the legacy AGM-84
Harpoon series lacks the survivability to tackle the most recent
generation of Anti-Ship Missile Defences (ASMD), the most practical
candidate for such a role would be an anti-ship variant of the AGM-158
JASSM, being acquired now by the RAAF. The drawback of this approach is
that subsonic profiles must be flown with the missile attached - given
the range of the JASSM/JASSM-ER stealth is simply not an issue.
Is there an alternative way to
attack warships which is cheaper and permits supersonic ingress to the
target? The answer is yes.
In late November, 2004, the US
Air Force conducted the Resultant Fury maritime strike exercise in the
Pacific. One of the aims of this exercise was to validate and
demonstrate the concept of using the Affordable Moving Surface Target
Engagement (AMSTE) scheme against maritime rather than ground vehicular
targets.
AMSTE is a scheme in which GPS
aided smart bombs are adapted with a radio datalink to permit them to
engage moving surface targets. The guidance system of the bomb is
modified with a datalink receiver, and the autopilot altered to include
a lead and intercept control law. As the bomb flies to its target,
continuous target position updates are relayed over the datalink,
several times per second. The bomb projects the target's position and
flies an intercept trajectory to impact at the last received coodinate,
fractions of a second before impact.
Target coordinates for the
bombs are produced by a radar equipped platform, standing off from a
safe distance. Because multiple datalink channels can be used, dozens
of bombs may be concurrently guided against multiple targets.
AMSTE was first devised as a
means of all weather attack against convoys or moving formations of
armoured vehicles. These are smaller and faster targets compared to
warships, and can change direction more rapidly. There was no doubt
that the AMSTE concept was going to be a success in maritime warfare,
and the Resultant Fury exercise proved this.
Spiral upgrades for the F-22A
will include over time the capability to carry AMSTE enabled munitions,
such as JDAM variants and Block II Small Diameter Bomb. This is
inevitable as they are required for lethal suppression of 'shoot and
scoot' Surface to Air Missile systems. By default this capability
becomes available for use in maritime roles.
It is worth observing that the
F-22A's Block 20 APG-77 AESA radar is exceptionally well suited for
this role, as it has exceptional power-aperture performance, and is
equipped with hardware and algorithms for Inverse Synthetic Aperture
Radar (ISAR) imaging of aerial targets. Expanding the ISAR modes to
permit imaging of surface shipping is not a difficult task. Given that
the planned ISR roles of the aircraft will require the addition of
transmit capable datalink terminals, providing the F-22A with the
capability to guide AMSTE enabled munitions is not a difficult feat.
The CONOPS for this regime of
attack would be the 'Hunter-Killer' model, in which a pair of F-22As
would alternate roles as 'Hunter' and 'Killer', until their payload of
JDAMs or SDBs is expended.
Other options also exist. From the outset the JDAM was intended to be
enhanced with a range of specialised seekers. To date only the laser
seeker has materialised, due to demand by operators in
counter-insugency strike roles. Numerous options exist for
anti-shipping seekers. These include Ku-band or millimetric band radar
seekers, low cost focal plane thermal imaging seekers such as the
DAMASK demonstrator, or adaptations of scanning infrared seekers. A
anti-shipping seeker equipped JDAM or SDB would allow completely
autonomous fire and forget targeting by the F-22A.
There are compelling reasons to adopt a guided bomb CONOPS for ASuW
roles should they be flown by the F-22A.
The first reason is cost. Anti-ship missiles cost between hundreds of
thousands to millions of dollars apiece. Usually multiple rounds must
be launched to saturate the ASMD system on the target warship. JDAMs
and SDBs are munitions in the $20,000-50,000 cost bracket, and thus
saturation can be effected at much lower cost per target warship.
The second reason is survivability. Modern ASMD systems are
optimised to detect and engage inbound sea skimming missiles and
present often formidable detection and engagement capabilities. Smart
bombs flying steep vertical dive trajectories literally fly down the
blind coverage funnel above a warship, presenting difficulties for
defensive systems not built to engage inbound ballistic missile class
threats.
The third reason is lethality. A J-1000 warhead or SDB warhead is built
to penetrate multiple feet of reinforced concrete, and will slice
through the decks of a modern warship with ease. These weapons are akin
to the munitions fired by heavy naval guns which proved so lethal
during the 1940s.
Technology however offers some important gains over 1940s artillery.
Not only are these modern bomb warheads designed to penetrate deep, but
modern smart fuses offer other possibilities, as they can sense how
deep they have penetrated using an accelerometer.
Of particular interest is the option of fusing a penetrating bomb to
initiate below the keel of a target warship. This will inevitably
produce similar damage effects to a smart torpedo detonating under the
hull of the target, causing a hull breakup.
In summary, there are very many ways of executing ASuW operations using
the F-22A, providing a more lethal and operationally sustainable
weapons system than legacy anti-shipping missiles offer.
Further Reading:
Air & Space Power
Chronicles, Maxwell AFB -
July 2000 - EXPANDING
THE ENVELOPE - Stealth and Other Strike Roles
Defence
Today -
September/October
2006 -
NCW 101 - Part 8 Ground and Maritime Moving
Target Indicator Radar
Air
Power
Australia - January
2007 - Regional Precision Guided
Munitions
Australian Aviation -
December 2002 - JDAM Matures - Part 1
Australian Aviation -
January/February 2003 - JDAM Matures - Part 2
Air
Power Australia - January 2007 - GBU-39/40/42 Small
Diameter Bomb
Air Power
Australia - July 2005 - Warship
Vulnerability
Maj. Lawrence J. Spinetta -
Air Force Magazine - July 2006, Vol. 89, No. 7 - Sinking Ships
DARPA - 1999 AMSTE
PPT Presentation
Dave DeVore - Presentation to 7th International Artillery &
Indirect Fire Symposium - 19 June 2002 - AMSTE Overview
Northrop
Grumman - Briefing Slides - Affordable
Moving Surface Target Engagement
Raytheon - Briefing Slides - Resultant
Fury 04
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AMSTE CONOPS and Resultant Fury
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During the Resultant Fury exercise
conducted late November, 2004, the US Air Force trialed the use
of
AMSTE-modified 2,000 lb JDAM guided bombs, with datalink updates from
an
E-8C JSTARS, and laser guided 2,000 lb GBU-10/BLU-109 bombs targeted by
a Litening II pod on a B-52H. Upper - former USN LST Schenectady takes
a
hit by multiple JDAMs; Lower - damage effect produced by JDAM hits on
waterline. The vessel sank 1.5 hrs later [More images at U.S.S.
SCHENECTADY - OPERATION
RESULTANT FURY].
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F-22A Raptor Maritime Strike CONOPS #1
F-22A Raptor Maritime
Strike CONOPS #2
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Damage Effects - Maritime Strike
Damage Effects of Warhead Initiation Below
the Keel
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This sequence of images shows the effect
of a Mk.48 series torpedo initiating below the keel of the target
vessel. The expanding gas bubble breaks the keel of the vessel,
snapping the hull in two. A smart bomb with a smart fuse programmed to
initiate below the hull of the target would produce the same effect,
but with additional hull weakening produced by kinetic damage effects
as the bomb penetrates down through the hull (Image via Wikipedia).
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Artwork, graphic design and text © 2004, 2005, 2006, 2007 Carlo Kopp; Text © 2004, 2005, 2006, 2007 Peter Goon; All
rights reserved. |
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