SRAAM mockup at Royal Air Force Museum Cosford
|Type||Short-range air-to-air missile|
|Place of origin||United Kingdom|
|Used by||Experimental programme only|
|Weight||ca. 70 kg (150 lb)|
|Length||2.75 m (9 ft 0 in)|
|Diameter||165 mm (6.5 in)|
|Wingspan||ca. 320 mm (13 in)|
|250 m – 2 km|
The Short Range Air-to-Air Missile, or SRAAM, was an experimental British infrared homing ("heat seeking") air-to-air missile, developed between 1968 and 1980 by Hawker Siddeley Dynamics. It was designed to be very manoevrable for use at short range in a dogfight situation. SRAAM was unusual in that it was launched from a launch tube instead of being attached to a launch rail, allowing two to be carried on single mounting point.
Although initially intended to replace the AIM-9 Sidewinder, it was downgraded to a technology demonstrator program in 1974. Between 1974 and 1977, several SRAAM missiles were launched in tests. In 1980, the knowledge gained from the SRAAM project became the British contribution to the multinational ASRAAM missile project.
The Vietnam War made it clear that the air-to-air missiles then in use by the USAF were inadequate. The AIM-9 Sidewinder had limited "off-boresight" capability, which meant that the launching aircraft had to point itself at the target in order to lock-on. As the Sidewinder's seeker could only see the hot exhaust of the engine, in practice this meant that the launching aircraft had to line up behind the target for a shot, and follow it for a time prior to launch.
In practice, pilots would often take shots at aircraft that were passing by the front of their own aircraft, launching as soon as the seeker's indicator growl was heard. By the time the missile had cleared the launch aircraft, the target was no longer in the seeker's view, and the missile would fly off ballistically. The initial US response was to train their pilots to only fire missiles under certain conditions, and use their cannon under others.
In 1970 the British Ministry of Defence came to the conclusion that a better short-range missile was needed, and drew up a request for proposals (Air Staff Target 1218). This outlined the need for better maneuverability and a wider seeker angle, in order to successfully intercept the target in the types of shots the pilots were attempting to make, as opposed to demanding they not take those shots. AST 1218 also included the requirement that the missile could be carried by aircraft that lacked the target acquisition systems of the Phantom and Lightning.
In 1968, Hawker Siddeley had started private development of a missile named "Taildog". This was to be a short-range, low-cost missile that would fill the gap between guns and then-current missiles like Firestreak and Red Top. Hawker described it as 'a gun that fires around corners'. In 1970, Taildog became Hawker Siddeley's response to AST 1218.
Taildog was highly manoeuvrable through the use of thrust vectoring for all flight control. The vectoring was initially accomplished by rotating small vanes into the rocket exhaust. Six of these vanes were arranged as segments of a circle at the tail end of the missile body, where they were protected from the rocket exhaust. Each segment was pivoted at one end, allowing it to be rotated so the other end would be moved into the exhaust. The control system would activate the segment closest to the required change in direction. External aerodynamic surfaces were reduced to vestigial surfaces near the rear of the missile, and were unmovable.
The initial version of Taildog was 2.0 m long, had a diameter of 16.5 cm and weighed 50 kg. It was capable of engaging targets between 250 m and 2 km, as compared to perhaps 12 km under the best case for Red Top. The first photographs of mock-ups were shown in early 1970, and were displayed at a trade show in Hannover later that year.
Hawker's proposal was received favourably, and in 1972 the Ministry of Defence awarded a development contract (Air Staff Requirement 1222). Two versions were studied, the advanced SRAAM-100 and a basic version called SRAAM-75. Both used the same airframe but different electronic fits. SRAAM was slightly longer than Taildog, with a length of 2.75 m (9 ft 0 in). The diameter remained the same. The thrust director system was replaced with a moving dome deflector, which consists of a cone-shaped deflector placed in the exhaust which is moved to the sides to cause the thrust to change. The fins were moved to the rear and got a different shape.
SRAAM was designed to be carried in a launch tube to protect the missile. The fins on the missile were hinged and designed to extend following launch. The launcher comprised two tubes and most of the guidance system, enabling the missile to be carried by almost any aircraft with little modification. The missile could be fired automatically when a target came into view of the seeker (unlike e.g. Firestreak, which needed to be fed targeting information by the aircraft's radar).
The contract was cancelled in 1974 due to defence cuts in favour of work on Skyflash, but retained as a technology demonstration program. In 1977, eight test missiles were fired from the ground and from a Hawker Hunter F.6 (RAF serial XG210). The trials were successful, with one famous incident demonstrating the missile's maneuverability when it turned into the Hunter's flight path immediately after launch and almost collided with it. In the same year, the British MOD chose the AIM-9L Sidewinder as its next short-range missile, but the SRAAM project was kept alive to provide a base for a future missile design.
- Gibson 2007, p. 48
- "Missiles 1969", Flight, 14 November 1968, pg. 797
- "Diamond Jubilee Salon", Flight, 5 June 1969, pg. 935]
- Gibson 2007, p. 49
- "Taildog Makes Its Bow". Flight International: 650, 704. 23 April 1970.
- "Britain's Aircraft Industry 1970". Flight International: 366. 3 September 1970.
- Gibson 2007, p. 51
- Gunston 1979, p. 221
- Gibson 2007, p. 34
- "Asraam - Europe's new dogfight missile", Flight, 6 June 1981, pg. 1742]
- Gibson 2007, p. 50
- RAF Museum website
- Gibson, Chris; Buttler, Tony (2007). British Secret Projects: Hypersonics, Ramjets and Missiles. Midland Publishing. pp. 34–53. ISBN 978-1-85780-258-0.
- Gunston, Bill (1979). An illustrated encyclopedia of the world's rockets and missiles. Salamander Books. p. 221. ISBN 0-517-26870-1.
- "British Aerospace SRAAM". Retrieved 27 January 2011.