Rocket Motors and Candle Flames.

At the end of the second world war the British had two anti-aircraft guided missile projects running –the Army’s Brakemine and the Navy’s anti-kamikaze missile Stooge. The latter was a command guidance missile developed by Fairey Aviation, which was simply steered into the path of an incoming aircraft. It became evident, however, that this missile would not be fast enough to intercept jet aircraft so the project was cancelled at the end of the war. The British made use of the German missile project technology, particularly that for Wasserfall. It isn’t clear when the Navy’s long range missile project started, but there are references to Seaslug as early as 1949. The Germans had experienced severe problems with the rocket’s exhausts interfering with the missile’s reception of command signals; this was worse when the rocket motor ‘burnt-out’ and formed a candle flame from the slow burning of fuel residue. The British saw this as a major problem and took various steps to avoid the problem. The RAF’s Fireflash had an un-guided boost phase followed by a guided glide phase, and Seacat had its receiver aerials in the trailing edges of the wings. Seaslug, however, posed a greater problem as it had a sustainer which burnt for 38 seconds followed by a glide phase of up to 20-25 seconds when a candle flame could easily form and the aerial was just a few inches away from the rocket nozzle. The Project 502 team’s solution was to fit the sustainer motor with an extinguisher to snuff out any candle flame. This contained a pint (568ml) of carbon tetrachloride (now properly called tetra-chloro-methane) and was injected into the sustainer motor when the internal pressure dropped off.