Julian Moxon/BOURGES
AEROSPATIALE IS working on a small diameter, low-cost ramjet-powered missile intended for air-to-air, anti-radar and light naval applications.
Researchers at the company's Bourges site will soon test a prototype engine, which in production form would cost about the same as a typical missile rocket engine. A ramjet-powered missile could have a range of between two and five times that of a conventional air-to-air missile says Alain Chevalier, head of Aerospatiale's missile division propulsion department.
"The problem has always been the cost of developing the turbopump and associated hardware for a small ramjet," says Chevalier, whose team has developed a simpler pressurisation system for the kerosene fuel which has no rotating parts, but is light and inexpensive.
Kerosene is forced into the ramjet injectors by a rubber bladder, which inflates progressively along the length of the fuel tank. Initially, the bladder forms a close fitting sheath around the lengthwise compressed-air bottle from which it is inflated. At ignition, the bladder expands to the full diameter of the fuel tank at the end furthest from the engine, the "bubble" then moving along the length of the tank, forcing kerosene to the ramjet injectors at around 20bar (206lb/in2).
To solve the problem of differing pressure requirements with increasing altitude, Aerospatiale has also developed a new injector which uses an "all or nothing" principle to turn fuel on or off, actuated by a simple electromagnetic coil.
Up to 12 computer-controlled injectors split equally into two different diameters, will be used in a test due to be carried out in 1996.
Chevalier says, that the engine is very much a technical demonstrator, but that tests to date provide "very promising" results.
A missile fitted with the engine would still use a powder booster to reach Mach 2, the ramjet then pushing the missile to Mach 3/4 for an air-to-air burn time in the region of 100s.
Source: Flight International