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 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 system.
PT.428
The initial design contest for the LAA was won by British Aircraft Corporation 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 from that point.When PT.428 ended in 1961, BAC began considering less-expensive options based on the same general concept. During this time, Colin Baron and John Twinn at the Royal Aircraft Establishment were developing an optical semi-automatic command to line of sight 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 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" 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 — 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 and the Detachment Support Vehicle. 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 Land Rover towing a 1-ton Missile Supply Trailer containing up to 10 further missiles. Blindfire radar was only provided for a third of fire units in British Army service, but for all fire units in the RAF Regiment.