Technology Explained – Cruise Missiles

The General Dynamics AGM/BGM-109 Tomahawk

Developed in the seventies as GD’s answer to the Boeing ALCM, the Tomahawk although functionally similar to its competitor is aerodynamically and structurally a very different beast. The Tomahawk was designed from the very beginning to coexist with a naval multimission environment, this is reflected in the airframe shape and structural modularity of the vehicle. These two attributes offered a basing/role flexibility, albeit gained at the expense of flat-out maximum speed, which not only secured the weapon’s future in the naval arena but also won it the role of the GLCM.

The basic Tomahawk is a 21ft(6. 4m) vehicle with a launch weight in the 2600Ib (1200kg) class, subject to a specific missile version. The missile airframe is essentially circular in cross-section from nose to tail, with most of the structural modules being cylindrical in shape. The aftmost section of the Tomahawk is the tail cone, which houses both the control surface actuators, which drive the four symmetrical folding control surfaces and the powerplant. Here is where a difference does exist between the basic Tomahawk and its air-launched MRASM derivative. The baseline Tomahawk is fitted with a 600Ib thrust class low bypass ratio Williams International F-107 turbofan, common also to the ALCM (see Sept TE, Strategic Cruise Missiles). As the Tomahawk is somewhat lighter than the ALCM, the thrust-to weight-ratio limitation due to the use of this powerplant is not so apparent.

The MRASM missile is then fitted with a Teledyne CAE variable speed turbojet, also 600Ib class, somewhat thirstier but far cheaper (cca 60%) than the turbofan. The powerplant thrust line is depressed by several degrees and offset below the longitudinal axis of the missile. Forward of the tail cone is the cylindrical aft body section of the weapon, it houses the ventral engine inlet/inlet duct assembly in all versions. Prior to launch the inlet is flush with the missile’s skin, but deploys upon reaching a programmed point in the launch sequence. In MRASM the upper half of this section houses the Tercom, INS and central computer, in the baseline Tomahawk situated in the nose. The aft body is then mounted on the missile’s mid-body section. The midbody is split into upper and lower halves (containing JP-10 fuel), with a wing stowage space between them. The pop-out wings pivot at the front of the mid-body ends just forward of the wing’s leading edge and at this point the forward module section mounts to the above basic airframe.

In the nuclear versions of the missile, the rear half of the forward module contains a fuel tank, the forward half a W-84 200 kT tactical nuclear device and the guidance electronics in the nose. Conventionally armed Tomahawks and MRASMs carry a large WDU-18/B 1000lb HE warhead, as used in the obsolete Bullpup missile, or a submunition dispensing payload bay, In either instance this is at the expense of fuel tank volume and results in a major reduction in range. The immediate nose section in the MRASM houses only the terminal guidance electronics. In those Tomahawk versions that use Tercom aided INS for guidance, the guidance system is common with that of the AGM-86 ALCM.

The General Dynamics BGM-109G GLCM

The ground-launched GLCM is the best-known of the Tomahawk family due to both the political upheavals associated with its deployment and staggering program development cost overruns. The GLCM was conceived in the seventies to enhance the theatre nuclear strike capability of the USAFE, essentially limited to the F-111 wings in the UK.

The requirement grew in urgency very rapidly, as the Soviets deployed the SS-20 Intermediate Range Ballistic Missile, . The SS-20 is essentially a scaled-down MIRVed ICBM (some sources suggest it was in fact derived from an ICBM airframe utilising both the payload, guidance and upper stages of the original missile), as such it has the capability to deliver three Megatonne class nuclear warheads from Western Siberia to Western Europe, with a respectable CEP (miss distance).

The missile is carried on a mobile launcher which is also air transportable in a C-5 class transport. Without intercontinental range it is exempt from ICBM limiting treaties and once field deployed out of its hardened base shelter, is extremely difficult to locate and thus near impossible to knock out in a pre-emptive strike. With a flight time far lesser than that of ICBMs targeted for the US, the SS-20 provides the Soviet theatre nuclear commander with a very rapid surgical strike capability against any European target (or if deployed in Vietnam as suggested by some sources, against any Northern Australian target).

Initial US plans called for deploying single GLCMs towed by light vehicles, but this soon yielded to the idea of four round launchers, operated in flights of four launchers. This arrangement was finally adopted by the USAF. GLCM flights are based each in a hardened concrete shelter, theoretically impenetrable to conventional •PGMs. Each flight has thus four Transporter Erector Launcher (TEL) units and is c<>ntrolled by two Launch Control Centers (LCC), The TEL is a !;\6ft (16. 9m) semi-trailer, the forward third of which is an armoured Forward Equipment Box, containing a generator and launch interface electronics. The remainder of the TEL trailer is then the hydraulically raised four-round launcher. The 57ft (17. 3m) LCC trc1iler is the nerve centre of each GLCM flight. LCCs provide nuclear, biological, and chemical (NBC) protection for the two operators and house the launch control computers a software target library and HF, VHF, UHF, satellite, and landline communication equipment. GLCMs can be targeted and launched only from the LCC, the TEL electronics allow disarming only. The TELs are tied into their LCCs with optical fibre EMP immune cables. Both the TEL and LCC weigh around 80,000lb (36 tonnes), both are blast and small arms hardened, both are air transportable by C-141 and C-5, and both are towed by a common eight-wheeled 400 HP V-10 10-ton diesel tractor.

Prior to launch the actual launcher is raised and the rear blast doors opened, the missile is fired from its tube with a 7,000lb class Atlantic Research Corp solid propellant booster, breaking through a tube cover and climbing until sufficient speed is attained for wing/control/inlet deployment and engine startup. It then descends to a programmed altitude, locks on to a heading for its initial Tercom matrix (see Sept TE, ALCM) and follows the characteristic attack profile of the Tercom-guided cruise missile; flying from matrix to matrix until its target is reached, where the W-84 is then airbµrst at a programmed altitude. The GLCM has comparable range to the ALCM at 1,500nm (cca 2,500km) but is marginally slower at 485kt against the 530kt of the ALCM.

In the event of ‘increased readiness’, the TELs and LCCs would deploy out from their shelters, splitting into two groups each with two TELs and an LCC, and disperse by road to presurveyed launch sites within 100 miles of the shelter. Operationally the weapon has had few of the Tercom-related problems of the ALCM essentially because the mountainous terrain of Eastern Europe is unique and well mapped, the biggest problem surfacing with the GLCM being the excessive program cost of the order of $4,000 million (virtually a whole order· of magnitude against initial estimates).

The GLCM offers an identical mode of deployment to the SS-20 with all of the inherent immunity to a pre-emptive strike (unless of course, a fifth columnist followed the convoy to • its dispersal site. . . ), but compared to an SS-20 it is far inferior in throw weight and response time and thus is really no more than a retaliatory deterrent weapon. Even so the Russians are uncomfortable about it, SS-20 is easily detectable and can be hit (in theory) with Patriot class SAM/ABM missiles, whereas the GLCM is quite difficult to detect and equally difficult to hurt down. With the ability to hit moderately hard targets in the Moscow area from West European bases the GLCM has quite a considerable deterrent value, the manner in which the Soviets responded to its deployment eg initiating large-scale anti-nuclear hysteria throughout Western Europe testifies to this convincingly. The USAF intends to deploy 29 GLCM flights in Europe by 1988, most of these based in the UK, Italy and West germany. IOC was attained initially in December 1983, at Greenham Common in the UK.

The General Dynamics BGM-109A/B/C SLCM

The SLCM cruise missile family satisfies many of the US Navy’s diverse · surface attack needs. Initial studies for the submarine-launched Tomahawk began in 1972, the missile first flew in 1976. The weapon was originally intended for launch from the torpedo tubes of nuclear attack subs, however the weapon’s launching modes and payload/range characteristics have since been diversified: At this stage four launching modes are anticipated or in use. Torpedo tube launch is currently used with SSN-637 and SSNa688 class attack subs, but newer 688 class vessels from 719 on are expected to carry twelve vertical launch tubes in the forward ballast tanks, freeing space for torpedoes or Harpoon rounds.

Armoured box launchers are currently in use with surface vessels, the DDs963 class and the Iowa class (eg New Jersey) being fitted. The DD-963s are to however undergo a future refit, with Vertical Launch System (VLS) installations, SLCM/ Harpoon/Standard compatible with rapid launch/reload capability. The same installation will be used also on the newer CG-47 class Aegis cruisers. One of the reasons why the USN strongly favour the VLS is that it is virtually impossible for a potential opponent to establish, eg through observation/recce, the nature of the vessel’s weapon mix. Furthermore a failed launcher cannot disable the weapon system as in eg FFG-7 class vessels.

The SLCM is equipped with the same 7,000lb launch booster as the GLCM, the launch sequence is virtually identical aside from the torpedo tube launch where a steel protective shell is discarded upon leaving the tube. The nature of the weapon’s attack profile will however depend on the specific type of guidance and warhead fitted.

The BGM-109A TLAM/N (Tomahawk Land Attack Missile/ Nuclear) is virtually equivalent to the USAF GLCM employing both the Tercom guidance and 200kT warhead of the ground-launched weapon. Though this missile was initially intended to perform a strategic role it was subsequently decided to shift the role into theatre nuclear strike and strategic reserve, As such it would be employed primarily against high-value land targets such as airfields, missile sites and naval installations, the weapon providing the USN with its desired surgical capability against post-nuclear exchange targets and with a flexible tool for use in Third World contingency situations. Significantly it offers the attack sub fleet a near strategic retaliatory strike capability which due to the nature of the attack submarine is highly survivable and extremely flexible. The USN intends to acquire 800 rounds which will arm 32 SSN class boats and about 100 surface vessels.

The BGM-109B TASM (Tomahawk Anti-Ship Missile) is a stand-off anti-ship weapon with a conventional warhead. The basic TASM design employs an inertial midcourse guidance system with a terminal active radar guidance set modified from the MDC AGM/BGM-84 Harpoon missile. A 1,000Ib high explosive warhead is employed, this has cut range down to the 250nm class. TASM performs similarly to Harpoon, after launch it will drop to a low cruise altitude and using target bearing/range data loaded just prior to launch, aim for the immediate target area. Cruising at a low altitude conceals the location of the launch vessel. As TASM approaches the target area it will climb steeply and initiate a target search, flying a preprogrammed pattern, It is at this stage that the radar seeker is turned on, the previous flight being under inertial guidance (strap-down kit). Once the target is located, TASM locks itself on, drops to a sea-skimming altitude and moves in for the kill, manoeuvring to evade defences and finally punching through the side of its victim. .

The radar seeker is frequency agile, is credited with the ability to selectively choose high-value targets and may have a home on-jam capability. The missile has ho IFF capability, however.

This aspect of the missile’s guidance, together with its considerable (250nm+) stand-off range and apparently observed difficulties in target resolution/ECCM have raised a considerable amount of criticism. Essentially the issue revolves around the all-important rules-of-engagement in surface-surface but particularly submarine-surface strike situations. The problem lies in acquiring positive target identification, already limiting the effectiveness of existing Harpoon this restraint is a big problem with TASM. Suggested solutions essentially revolve around the use of LAMPS Ill helos or orbital radar platforms to provide the launch vessel commander with Over-The-Horizon. (0TH) target data. Another option under review is ship/sub-TASM launch and hand-off to a targeting aircraft (eg P-3). All of these options really limit the flexibility of the weapon.

The BGM-109C TLAM/C (Tomahawk Land Attack Missile/ Conventional) is a non-nuclear precision and attack weapon. TLAM/C is the heaviest of the SLCM family at 2,800Ib, it carries the large 1,000lb warhead of the TASM, the Tercom/inertial guidance of TLAM/N and an additional DSMAC II terminal guidance set. DSMAC (Digital Scene Matching Area correlator) compares an optical view of the target area to stored images In the computer memory in order to eliminate the final Tercom/ inertial errors.

Though the USN have not quoted CEPs for the missiles, numerous trail shots illustrate the missiles burying themselves into target walls (eg AWST, 20/08/84, p17) or screens (eg Flight 16/1 0/82, p1113), which for given: warhead size (960Ib) and nominal target hardness would suggest 15 to 25ft. this pin-point accuracy combined with the missile’s 700nm + range suggest its use against high-value targets, typically naval bases (including static shipping), airbases, SAM/ASM launch/C3 , installations, command posts and other non-nuclear hardened point targets,

Current growth capabilities envisaged are a pop-up attack terminal trajectory for the weapon and also a submurntIon dispensing payload bay replacing the HE warhead for airfield attack or defence suppression. The attack profile resembles that of TLAM/N, with the exception of the terminal phase when DSMAC provides the final update.

The SLCM family provide the USN with a very versatile group of weapons, particularly the submarine-launched land attack missiles offer an entirely new capability, both in_ nuclear and conventional warfare. The USN intends to acquire a total of 4,000 rounds by 1992, IOC was initially attained in 1983.

The General Dynamics AGM-109H/L MRASM

MRASM is a low-cost air-launched derivative of the Tomahawk family, conventionally armed and intended for both USAF and USN use. As outlined earlier, the propulsion was changed to a turbojet to cut costs, but other measures were also taken. The LN-35 inertial set was replaced with a low-cost strap-down ring laser gyro set, the redundant launch booster was eliminated and the core weapon guidance (Tercom/inertial) was relocated to the aft body, freeing the front of the missile for a fully modular_ payload bay with terminal guidance only. All versions have 250 nm+ class range, the land attack versions using Tercom/lNS/DSMAC guidance, the antiship version using datalink midcourse and Imaging Infra-Red (IIR) terminal guidance.

The AGM-109H is the USAF’s airfield attack weapon. l_t is the heaviest of the Tomahawk family, at 3,100lb at launch. MRASM is to be carried primarily by the B-52G and F-16, though other aircraft will be compatible, and is intended for stand-off counterair or defence suppression missions. The weapon’s forward payload bay is modular, built around a ‘backbone _ · beam into which individual payload modules are plugged into. These Modules are tailored to the target, carrying submunitions such as mines, GEBs (Combined Effects Bomblets) or in particular, runway attack submunitions (eg BKEP). These are Usually rocket boosted arid will punch holes into concrete surfaces some instances penetrate beneath the concrete surface and lift it.

The attack profile is typical, again the launch aircraft loads the missile with target particulars, Tercom matrices and DSMAC scenes, it then releases the missile within 250nm of the target. The surfaces and inlet deploy, inertial guidance is activated and the weapon is off to its first matrix. Upon reaching the target, however, MRASM activates its Pattern Controller Subsystem. This unit uses the exact position data provided by DSMAC and flies the missile over the target; eg runway/taxiway, along. A programmed flightpath during which it dispenses the submunition payload in a programmed pattern. As the payload may be mixed both surfaces and facilities/aircraft may be attacked and area denial mines may be also used.

The technique used for expelling Munitions from the payload bay is commonly termed ‘air-bag’ technology and is simple and robust. Munitions or clusters of munitions are fixed the bay with a strap, this strap has a link in it designed to fail at a certain tensile loading. An ‘air bag’ of a high-strength fabric (Kevlar?) Is placed beneath the munition, it is tied to the nozzle of a gas-generating cartridge. Upon cartridge ignition, the ‘airbag’ fills with hot gas and applies an outward force to the munition. At some instant the pressure in the bag will generate enough force against the munition to break the link in the strap and the munition is then ejected. Cheap and nasty, but cost-effective. The DSMAC guidance is credited with night/adverse weather capability.

Costing about 60% of a baseline Tomahawk, MRASM is nevertheless an expensive tool, one would therefore expect the USAF to employ it only in very high-density scenarios or perhaps for surprise counter-air strikes, to ‘lock in’ enemy aircraft prior to a large-scale air strike with fighter bombers. The modularity of the weapon does allow for future upgrades with more advanced submunitions and thus it may eventually acquire other roles.

The AGM-109L is the USN’s air-launched weapon and is configured in two basic versions. The land attack version uses the same Tercom/inertial/DSMAC guidance as TLAM/C and also the standard warhead, the mission profile and the type of target are also identical. The anti-shipping version uses a data link for midcourse guidance and an IIR seeker, modified from the AGM- 65D Maverick missile, for terminal guidance.

The primary launch aircraft is envisaged to be the A-6E Intruder, though there should be compatibility with other aircraft. The attack profile for the anti-shipping version is probably unique in the Tomahawk family, The A-6E would launch at distant targets from prebriefed data or closer targets from attack radar data, the missile would then receive datalink updates until within line-of-sight to the target, after which the seeker would be cued onto the target and a TV contrast lock engaged to provide a terminal launch-and-leave capability. Navy MRASM is shorter and lighter than the USAF weapon, it is easily recognised by its swept wings in which it is also unique. The weapon will basically supplement the existing Harpoon and also provide a vast improvement over earlier, eg Walleye, standoff land attack weapons.

Proposed Tomahawk Applications

The flexibility and modularity of the basic Tomahawk airframe must be a delight for the weapon system designer. As a result, numerous other applications for the basic weapon have been proposed. The strategic anti-shipping or ‘Sea Control’ role is probably the most significant. In this role the anti-ship (AF Sea Control) MRASM would be carried by the B-52, which would serve as a long-range patrol aircraft, using its extensive ESM systems to sniff for enemy shipboard radar and communication transmissions. It could then attack targets with MRASM from outside the opponent’s air defence umbrella.

Yet another proposal along similar lines envisages the use of anti-ship SLCM type round, fired from ground-based TEL trailers as used with the GLCM. In this arrangement, the missiles would be targeted at shipping by their flight LCC as with the GLCM, the LCC would acquire its targeting data from aircraft, ships and particularly surveillance satellites. If using a· longer-ranged missile such mobile anti-shipping forces could be airlifted rapidly to key areas, such as Norway, Iceland, Turkey, Korea or Japan, to bottle up Soviet battle fleets inside their home ports, eg Murmansk, Sevastopol, Vladivostok.

During operation, the flights would regularly relocate to thwart enemy reconnaissance and subsequent air attacks. Another potential role for the weapon lies in standoff anti-armour attack, where typically an MRASM style weapon would carry autonomously guided anti-armour submunitions, in the class of the TGSM or Skeet, with tanks costing over $1 million apiece it could become eventually cost-effective.

In the context of Australia’s force structure, the cruise missile with its strategic flavour definitely appears as a luxury. To effectively use any weapon in the class, one really requires extensive long-range surveillance and communication systems, something which is very much out of the reach of Australia’s DoD at this instant.

Later anti-ship versions of Tomahawk, hopefully with an 0TH targeting capability using the P-3, could certainly be useful. No regional powers, excluding Vietnam, really have the sort of air defence system which would merit the use of MRASM or TLAM/ C in preference to a traditional low level night air strike. Were Australia of course to develop the need for a nuclear deterrent at short notice,· the use of TLAM/N in conjunction with attack submarines could be. a very cost-effective substitute for ballistic missiles or long range penetration aircraft.

The Soviets are certainly unhappy about the cruise missile weapon family – it forces them to spend heavily in defensive areas such as AEW/AWACS and PVO as a whole. With the recent Soviet trend to invest more in offensive weapons, pouring roubles into expensive (and expensive to support) systems that are inherently defensive must be very unpleasant for Soviet leadership.

As the US holds the lead in key technologies associated with cruise missile development (propulsion, electronics, stealth) and anti-cruise missile defences lookdown radar ·signal processing, IA planar arrays) the Soviets can only come out even with inside assistance, until then the cruise missile will continue to bleed their resources.

A final point for us to ponder is our future Australian air defence structure, as the deployment of a sub-launched TLAM-ski is not that far away and it will certainly be available on the Third World arms market in due course. The ultimate implications are more than obvious.