Rapier (missile)

Rapier is a surface-to-air missile developed for the British Army to replace their towed Bofors 40/L70 anti-aircraft guns. The system is unusual as it uses a manual optical guidance system, sending guidance commands to the missile in flight over a radio link. This results in a high level of accuracy, therefore a large warhead is not required.

Entering service in 1971, it eventually replaced all other anti-aircraft weapons in British Army service; both the Bofors guns used against low-altitude targets and the Thunderbird missile used against longer-range and higher-altitude targets. As the expected air threat moved from medium-altitude strategic missions to low-altitude strikes, the fast reaction time and high manoeuvrability of the Rapier made it more effective than either of these weapons, replacing most of them by 1977.

Rapier was later selected by the RAF Regiment to replace their Bofors guns and Tigercat missiles. It also saw international sales. In October 2021, it was replaced as one of the UK's primary air-defence weapons by Sky Sabre.

History

Earlier systems

The introduction of medium-range surface-to-air missiles, or surface-to-air guided weapons (SAGW) as they are known in the UK, had made flying at medium or high altitudes anywhere near the front line near suicidal. In response, air forces began introducing aircraft and weapons meant to be used at low altitudes, in nap-of-the-earth flying that used landforms to block the view of the aircraft from the radar systems on the missiles.

By the late 1950s, the British Army considered this threat considerable as new aircraft like the Sukhoi Su-7 became common and higher performance designs were in the pipeline. Against low-flying aircraft, only anti-aircraft guns were suitable, as they could be quickly swung and fired in seconds. However, the relatively short range of their Bofors 40/L56 guns meant they had only a very short period of time in which the aircraft was close enough to fire on.

To improve this, the Army began the development of a massively improved weapon known as " Red Queen". This used a large round in a rotary cannon arrangement for high rates of fire. In spite of some progress, in 1959, the General Staff concluded that guns were no longer useful against modern aircraft. For their immediate needs they purchased the updated Bofors 40/L70, and for the longer term began a new missile development for a short-range, rapid-reaction weapon, known as the Light Anti-Aircraft (LAA) system.

PT.428

The initial design contest for the LAA was won by British Aircraft Corporation (BAC) in 1960, and given the development name PT.428. This called for a system that could be carried on a single 4-ton Bedford TK truck. The firing unit was a single piece that would normally be placed on the ground during operation, but could be fired from the truck in an emergency. The system was deliberately designed to fit, when taken apart, as a single load in the Fairey Rotodyne. The system was quite advanced, including automated search and track radars, a separate television camera for target identification, and eighteen missiles in two nine-round boxes.

As budget pressures escalated in the early 1960s, the Army was given the choice of picking either PT.428 or their Blue Water nuclear missile. They chose the latter, a decision Solly Zuckerman found rather questionable. The Army officially replaced PT.428 with the similar but slightly less advanced MIM-46 Mauler from the United States. Mauler combined a search radar and nine missiles using either radar or infrared guidance on a single M113-derived vehicle. The concept was similar to PT.428, but larger and with fewer missiles.

Sightline

During the development of PT.428, BAC had also considered a lightweight version of the system which mounted six of the PT.428 missiles on a trailer that could be towed by a pickup version of the Land Rover. An early warning radar would be mounted on a framework above the roof of the truck, and initial tracking would be manual using a pair of binoculars mounted on a gimbal system in the truck bed. A small antenna on the launcher trailer would communicate with the missile to bring it into alignment with the binoculars and then follow semi-active radar homing (SARH) from that point.

When PT.428 ended in 1961, BAC began considering less-expensive options based on the same general concept."Rapier 2000/Jernas"
''Jane's Strategic Weapon Systems'', 15 February 2008 During this time, Colin Baron and John Twinn at the Royal Aircraft Establishment were developing an optical semi-automatic command to line of sight (SACLOS) system. Using this with the PT.428 missile produced the Sightline concept, which would be much less expensive than the original radar-guided version.

The next year, Mauler was downgraded on its way to being cancelled, leaving both the US and British Army with no modern short-range anti-aircraft systems. The General Staff and Air Staff responded by issuing the combined GASR.3132 requirement for a clear-weather daytime SAM for both the Army and the RAF Regiment. Whether GASR.3132 was designed for Sightline, or Sightline for GASR.3132, is not clear in existing references. The new concept was given the name "Defoe". An even smaller and cheaper system lacking an early warning radar was also considered under GASR.3134.

Rapier

In 1963, Defoe was made official, given the development target ET.316. BAC management initially gave it the name "Mongoose", but during a board meeting the issue arose that no one knew what more than one mongoose was called; mongooses? mongeese? The name "Rapier" was suggested and made official.

As development continued, it became increasingly clear that the Rapier was far more a formidable weapon than initially expected. The optical tracking system was so accurate that the missile almost always hit the target aircraft, so despite its small warhead and lack of a proximity fuze it almost guaranteed a kill. BAC joked that the system was a "hit-ile", as opposed to a "miss-ile". It also became clear that the warning radar system would be invaluable in the field, and GASR.3134 was dropped.

The first test firings of the missile took place in 1966. The system was extensively tested at Woomera, considerably supported by the Australian Army, an early user of the Rapier system.

In 1965, some Australian staff at Woomera began to develop a simulator system understand and tune the manual guidance system. This consisted of a joystick from the Rapier optical tracker which caused the projected image of the missile to move about. Models of the missile and various target aircraft were constructed and filmed using stop motion techniques to make a selection of films of various target attack sequences across the Woomera sky. The system was completed in 1968. In initial testing, tracking was seen to be a serious problem, and the British Army was concerned the system would be beyond the capabilities of the average gunner. Some problems were solved by adjusting the joystick's mechanical feedback to more closely match the missile's difficulty responding to various inputs. Many of the remaining issues were subsequently solved via a massive simulation run and data processing using an IBM 7090. Complete systems were tested in 1968, with a subsequent production contract in 1969.

On a parallel track, the RAF Regiment had been looking for a short-range weapon for airfield defense. Eventually, this led to the development of the Tigercat system in 1967, an adaptation of the Seacat naval surface-to-air missile system. Tigercat was similar to Rapier in basic concept, but based on older technologies and thus somewhat larger and heavier while offering less range and much slower speeds. Tigercat was introduced into service with No 48 Squadron RAF Regiment in 1968, giving the RAF Regiment the UK's first effective fully air portable low-level SAM system and valuable experience in operating systems of this type. In 1972 a trials unit known as the Rapier Pilot Battery was formed jointly by No 63 Squadron RAF Regiment and 9 (Plassey) Light Air Defence Battery Royal Artillery. Comprehensive trials ended in 1973 and the first Rapier unit in British service, No. 63 Squadron, deployed to its operational station in Germany in mid-1974.

In the 1980s, a new training simulator system was constructed in Stevenage. This consisted of a radius hemispherical dome whose inside surface was used as a movie screen onto which terrain images were projected. A copper vapor laser projected images of targets and the missiles in-flight on top of the background imagery, while a smaller helium-neon laser simulated the Rapier's tracking flare. A complete Rapier targeting unit was placed in the center of the dome, and its guidance signals were captured and sent to the simulator to update the position of the missile. The projected laser imagery was bright enough that it could be tracked by IR imagers and seekers, allowing it to be used with the updated Darkfire versions of the Rapier with their IR cameras, or other IR seeking missiles like the Stinger. This system was sold separately for use with other missile systems under the name British Aerospace Microdome.

Variants

The original Rapier took the form of a two-wheeled launcher carrying four missiles, an optical tracker unit, a generator, and a trailer of reserve missiles. The launcher consists of a vertical cylindrical unit carrying two missiles on each side, the surveillance radar dish and "Identification Friend or Foe" (IFF) system under a radome on top, the guidance computer and radar electronics at the bottom, and a prominent parabolic antenna for sending guidance commands to the missiles on the front.

The search radar, of the pulsed Doppler type, has a range of about . The aerial, located at the top of the launcher, rotates about once a second, looking for moving targets through their Doppler shift. Upon detecting a target, a lamp lights up on the Selector Engagement Zone (SEZ) — a box containing 32 orange lamps arranged in a circle about the size of an automobile steering wheel. The radar operator can use switches to blank out returns from other directions, providing jamming resistance.

The optical tracker unit comprises a stationary lower section housing the operator controls and a rotating upper section containing the tracking optics. The operator's optical system is a modified telescope containing a Dove prism to prevent the image 'toppling' as the optics rotate in azimuth. Using this system means that, unlike a periscope, the operator does not have to move to track the target. The upper section also contains a separate missile tracking system that follows the operator's optics, based on a television camera optimized for the IR band.

Upon detection of a target, the optical tracking system is slewed to target the azimuth supplied by the SEZ; the operator then searches for the target in elevation. The operator's field of view is selected based on the target's range: "wide" at about 20 degrees or "track" at about 4.8 degrees. When the target is found, the operator switches to "track" and uses a joystick to keep the target centred in the telescope. Once a steady track is established, the missile is fired. The TV camera on the tracker is tuned to track four flares on the missile's tail. Like the operator's telescope, the TV system has two views: about 11 degrees wide for the initial "capture", and 0.55 degrees for mid-course tracking.

The location of the missile relative to the line of sight is measured using a system identical to the "chopper" system used in early infrared homing missiles. The chopper is inside the launcher, rather than on the missile, and feeds an image from the tracking camera which passes through the light from the flares. The chopper generates signals that encode the angle of the missile relative to "up" and the angle out from the centre, or "error off". The simple computer in the base then calculates the control inputs needed to bring the missile into the line of sight and sends them to the missile via the transmitter on the launcher platform, to the small receiver antennas on the rear of the mid-body fins. The operator simply keeps the telescope's crosshairs on the target using the joystick, and the missile automatically flies into the line of sight. The basic concept is similar to that used by most anti-tank missiles, except that those normally use small wires — rather than a radio link — to send guidance information to the missile.

The missile contains a warhead with a contact fuze and a single-stage solid-rocket motor that accelerates the missile to about , about Mach 2. Engagement time to the maximum effective range is about 13 seconds. Response time from initial target detection to missile launch is about six seconds, repeatedly confirmed in live firing.

The whole system and its crew are delivered by two Land Rovers designated the ''Fire Unit Truck'' (FUT) and the ''Detachment Support Vehicle'' (DSV). Royal Artillery batteries comprised three troops each of four fire units, while RAF Regiment squadrons had eight fire units. By 1980, each Royal Artillery fire unit consisted of a 24-volt, 101 FC 1 tonne Land Rover towing the Rapier Launcher and carrying four missiles on board, a , 3/4 ton, 24 V FFR (Fitted For Radio) Land Rover towing a 1-ton Missile Supply Trailer (MST) containing up to 10 further missiles. Blindfire radar (see below) was only provided for a third of fire units in British Army service, but for all fire units in the RAF Regiment.

Blindfire radar, FSA

Although accurate and simple to use, the original Rapier system clearly suffered from a lack of all-weather capability. To address this need, BAC started work on a separate radar guidance unit, primarily to improve foreign sales. This led to the introduction of the Marconi DN 181 "Blindfire" radar in 1970, the first examples being sold to the Iranian Army in 1973.

The British Army did not purchase the Blindfire system until 1979, entering service with Rapier "Field Standard A" (FSA). The RAF Regiment had 27 Squadron operational with Blindfire at RAF Leuchars by 1979, and was in the process of bringing all the RAF Regiment GBAD (Ground Based Air Defence) Squadrons into line. By 1997 more than 350 Blindfire radars had been produced.

To ensure accuracy, Blindfire uses a very narrow "pencil" beam and tracks both the target and missile. To allow the operator to monitor the Blindfire system when it tracks the target, the existing optical tracker follows the Blindfire radar, although it is possible for the optical tracker to be manually "laid on" a second target whilst the Blindfire engages the first. The Blindfire trailer carries its own generator unit, and is towed by a third Land Rover (a 12 V winch-equipped 101 FC) with the designation ''Tracking Radar Tractor'' (TRT).

Tracked Rapier

With sales to Iran came the additional requirement for a fully-mobile version of Rapier to protect the Chieftain tanks being supplied on a UK MOD contract. BAC responded by adapting the Rapier system to fit on the M548, a cargo-carrier version of the ubiquitous M113. Development started in 1974 as "Tracked Rapier", with the first public showing at the 1977 Paris Air Show as a static display unit.

The initial proposal for the system was to simply mount the towed launcher, including its petrol generator set but minus its running gear, on the flatbed of the M548 carrier. When this was shown to Mr. G.R. Jefferson, the GW Managing Director, he was not very impressed. Aware of the amount of money available, he required a much more extensive change. Greville Beale and Adrian Pollicutt led the development of a significantly different arrangement which was produced in a short period.

This included significant changes to armour the M548 vehicle, now designated RCM 748, and to incorporate the diesel-powered Coventry Climax H 30 engine to run the new generator set, and also as the auxiliary power unit. The majority of the electronic equipment in the launcher was not changed significantly from the towed version. However, a completely redesigned armoured launcher with the capability of loading eight missiles was produced, mounted via anti-vibration mounts to the flatbed of the vehicle. The armoured cab was provided with pan-climatic heating/cooling and NBC protection.

The optical tracker was placed inside the armoured cab of the vehicle, elevating through the roof for operation. The tracker was operated from the right side of the crew cabin, while on the left were the driver and tactical controller who also had a helmet-mounted sight, allowing him to lay the tracker onto a visual target.

From moving to firing took only 30 seconds, a tremendous improvement over Towed Rapier, which required at least 15 minutes to unlimber, cable-up and align. A further difference between Towed and Tracked Rapier was that the Tracked Rapier launcher had eight (protected) missile rails compared with four in the towed system, enhancing firepower and reducing re-supply requirements. It was also air-portable, ready to deploy on landing, in C-130 aircraft.

There was no room for Blindfire on a single RCM748 vehicle, so this was instead towed or was to be carried on a separate modified M548/RCM748. Feeding data to the control system in the firing unit again required setup time to connect the two pieces of equipment.

The system had not yet been fully developed when the Iranian Shah fell from power in 1978. The vehicles were later purchased by the British Army as part of a Fixed-price Develop and Supply contract. The first production Tracked Rapier was accepted on time and to cost at Wellington Barracks in early 1981, and entered service with ''11 (Sphinx) Air Defence Battery'', of 22 Air Defence Regiment, Royal Artillery in 1983 in Napier Barracks near Dortmund.

After initially entering service at Towed FSB1 standard, with planar array radar and the 'Pointing Stick', the Tracked Rapiers were upgraded, with the latest version included a thermal-imaging enhanced tracker which enabled single vehicle 24-hour operation without the need for the Blindfire unit.

A modified M548 Missile Resupply Vehicle carried replacement missiles, a relief crew, and additional field kits, rations and water. A further M548 was configured as a REME Forward Area Support team with test facilities and spares.

During the Gulf War, 12 and 16 Regiment Royal Artillery tracked batteries, quickly fitted with sat-nav for desert use, combined to provide Tracked Rapier support to deployed armoured regiments.

Tracked Rapier was retired in the early 1990s, due to manning limitations when the Towed FSC version entered service. It has since been replaced by Starstreak missile launchers mounted on the Alvis Stormer.

FSB

Shortly after introducing FSA, "Field Standard B" (FSB) added a number of basic upgrades. Additionally, the search radar was upgraded to be easily shut down in case of an anti-radiation missile attack. FSB included lessons from the Falklands campaign, notable the 'pointing stick' that enabled the detachment commander of a fire unit to point the aiming unit at a target.

Laserfire

With the range of upgrades and new components, the original low-cost Rapier system was gone. In order to address international market requirements for a lower-cost system, BAC started development of the "Rapier Laserfire" in 1982. Laserfire replaced the original optical tracker unit with a new lidar (laser radar) illuminating system that is considerably smaller, allowing the entire system to be mounted on a single pallet that could itself be mounted on a truck or other flatbed vehicle.

Laserfire used a millimetric Doppler radar. Due to its very high frequency of operation and ability to transform its beamshape from narrow azimuth and high elevation to wide azimuth and narrow elevation, Laserfire was able to detect helicopters hovering or travelling at low altitude and in areas of high clutter by detecting the movement of the helicopter's rotor blades.

Initial engagement is similar to the original Rapier, but the target was illuminated and automatically tracked by a high power YAG:Nd laser. After the missile was launched the laser alternately illuminated the target and missile to determine their locations, and guidance was sent to the missile as normal (see laser guidance). Laserfire thus represented a fairly major upgrade to the original optical system, allowing semi-automatic engagements, and greatly reducing operator skill and training requirements.

On the downside, Laserfire no longer has the optical system of the original, which served an important second duty by allowing the aircraft to be visually identified at long range. Additionally, while the Laserfire tracking system was capable of being operated at night, target acquisition was optical, like the original Rapier.

Darkfire

In 1985 development started on a new tracker that replaced the original optical system with a new IR thermal imager system to improve its abilities, especially at night. This version was known as "Rapier Darkfire" for this reason. Trials of the new system started in 1987, and were deployed operationally in 1990 as "Field Standard B2" (FSB2), the earlier upgrades retroactively becoming FSB1. This system was also known as "Rapier 90". Cooling for the imager was provided by bottles of compressed gas.

FSB2 also introduced a number of improvements that greatly improved Rapier capabilities. First and foremost was the Tactical Control Console that allowed four Rapier launchers to be controlled from a central location. The launchers themselves were upgraded to carry six missiles instead of four, improving battery capacity. Finally, the search radar was updated to use a new planar array radar, although its capabilities remained generally the same as the earlier model.

Missile upgrades

In 1988 tests started on an improved warhead using a proximity fuze, in order to give Rapier capability against smaller targets that would be difficult to hit directly, notably high-speed remotely piloted vehicles. Serial production of Mk. 1E began in 1989.

In 1992 the Army signed a contract to upgrade all Rapier systems to an enhanced version. A Mark 2 missile variant commenced development in 1986 culminating in a complete re-design which entered service in the mid-1990s. Along with a further upgrade of the proximity fuze, the new missile incorporated (then) state-of-art technologies including:

Von Karman supersonic aerodynamic profile; composite propellant, with a two-stage shaped burn and laminated body solid rocket motor; ceramic substrate surface mount PCBs; completely new electronic systems and software; both analogue and digital proprietary ASICs; highly ECM resistant front end and command link with redundant encoding; fully Digital Autopilot incorporating Kalman state filtering; inertial navigation comprising ring-laser roll and rate gyroscope; Kapton ribbon cabling.

The missile warhead is available in two versions, the Mk. 2A for the normal anti-aircraft role, and the Mk. 2B, which includes a shaped charge warhead and dual fuzes, and which is useful against light armour as well.

Rapier 2000

In 1992, shortly after the introduction of Rapier 90, another major upgrade series started at MBDA

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