The Typhoon and it's Rocket

So the RP-3 was developed under the code term Unrotated Projectile, and was originally intended to be used as a barrage weapon in the anti-aircraft role or fired from a fighter aircraft to break up an enemy bomber formation.

And from reading the original documents in the National Archives at Kew, a lot of assumptions were made.

The idea for using the UP would be for a Hurricane to approach the bomber formation straight and level, and then fire the rockets at the bombers.

The maths required to ensure that the rapid rocket had any chance of a hit was mind-boggling and not something your average fighter pilot would be working out in combat.

The Luftwaffe, interestingly, would have the same idea later in the war when they deployed weapons like the Werfer-Granate 21 and the 55-millimeter R4M rocket that they used against the 8th Air Force.

In both cases, the chances of achieving an air-to-air kill were infinitesimal, but you could disrupt the formation and allow the other prowling fighters a chance to pick off a straggler.

Needless to say, while the rechristened RP-3 would not see much air-to-air action, its potential as an air-to-ground weapon was clear.

So let's take a closer look at the RP-3.

The RP-3's motor was a steel tube three and a quarter inches in diameter and just over 55 inches long.

At the tail end, four eight-by-five inch fins were attached to provide stability.

At the business end was a shell ring where the warhead was threaded on and would be then held in place with eight spring-loaded pins.

At either end of the rocket motor were saddles that allowed the rocket to be slid onto the projector rails and held in place with a little bit of wire.

But what was inside the rocket motor? Well, with the help from our friends at The Aviation Historian, who a while ago I collaborated with on an article about the RP-3 rocket with the fantastic Ian Bart, Ian came up with this animation, which we're gonna talk through to see what was going on inside that steel tube.

At the front of the motor was the igniter, which was then connected to the orbiter and some washers with a thermal initiator that would trigger the propellant.

The shell ring with its spring-loaded pins to hold the shell in place comes next, along with the spigot which would attach to the front of the motor.

The rocket was powered by a solventless cordite propellant, which was ignited by the electrical cable that ran from the back up to the igniter through the center of the propellant.

It would then burn from the front to the back, giving the rocket its power.

As we've discussed before, the fins and the casings and the saddles came on, and at the business end, the fuse was then inserted into the shell, which was screwed on and secured by the spigot and those springs that we spoke about a moment ago.