Editing Fireflash (section)

==Description==
[[File:Fireflash missile.png|thumb|left|Drawing of a Fireflash missile]]
The Fireflash was a [[beam riding]] missile - it was designed to fly down a radio beam emitted by the launch aircraft, which the pilot would keep aimed at the target.

It had a very unusual configuration: the missile body was unpowered. It was propelled by a pair of [[solid rocket|rocket boosters]] on the forward fuselage that were jettisoned 1.5 seconds after launch.{{efn|A cordite charge within a cylinder drove a piston, that sheared the pin that attached each rocket to the missile.}} The missile body, now travelling at around Mach 2,<ref name="rafm" /> would coast the remaining distance to its target under guidance from the launch aircraft (the missile was unguided during the boost phase).{{efn|The unusual configuration (an unpowered guided munition that coasts to the target after boosted to high speed by a rocket) was also used decades later in the British [[Starstreak (missile)|Starstreak missile]].}} The rocket engine nozzles were slightly offset to rotate the missile - this increased accuracy by evening out the effect of any slight asymmetry in thrust.<ref name="flight227" />

This configuration drastically limited both range and flight duration, but was used because of fears that [[ionisation|ionised particles]] in the hot, rocket motor exhaust stream would interfere with the guidance radar signals; further development showed the fears were unfounded.

Steering was accomplished by four rudders in a cruciform configuration. These were moved by four pairs of pneumatic servos, operated by solenoid valves. An air bottle, pressurized to {{convert|3000|psi}}, supplied air for the servos and also supplied the air that spun the three, air-blown gyroscopes in the missile's [[inertial navigation system]]. A high pressure air supply from the aircraft was also required to spin the gyros before the missile was launched.<ref name="flight227">Flight (1957), p. 227</ref>

The purpose of the control system was to keep the missile centred in the guidance beam emitted by the launch aircraft. The pilot of the aircraft would keep the beam aligned with the target using his gunsight, which was harmonized with the axis of the radio beam.<ref name="flight227" /> An advantage of this system was that it would be unaffected by the target aircraft using radar countermeasures such as [[Chaff (countermeasure)|chaff]]. The missile's receiver, fitted at the rear, only detected signals from the launch aircraft.<ref>{{cite web | url=http://www.ekco-electronics.co.uk/Blue_Sky/Blue%20Sky%204.htm | title=Blue Sky 4 | publisher=Etko Electronics | access-date=29 December 2012 }}{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>