Andrzej Jeziorski/Munich
Daimler-Benz Aerospace's (Dasa's) hypersonic missile (HFK) research programme is beginning to progress "out of a research background" towards an application in a future short-range air defence (SHORAD) system.
According to Peter Gleich, head of aeromechanics at the company's missiles subsidiary LFK, the technology will be sufficiently developed by 2001 for application in a real SHORAD system. Germany is participating in the current international SHORAD study, with France, Italy, Spain, Turkey and the UK, and is hoping to develop a replacement for its Gephard and Roland air-defence systems.
LFK has now carried out four launches of a 100kg HFK test vehicle flying at Mach 5.5, with accelerations varying from 350g at launch to a maximum 450g provided by a rocket motor generating 20t of thrust. The high-thrust phase lasts for 0.8s.
Gleich says that an operational missile would not accelerate quite so fast, but would still reach Mach 5.5 in about 1.5s. He adds that the preferred operational solution would have an active or semi-active radar seeker with a conformal antenna, and would destroy the target primarily by direct impact.
Gleich adds, however, that simulations show that hit to kill may not always be possible with a highly agile target, so the missile will carry a small explosive warhead with a proximity fuse.
The next HFK launch is due on 11 November, when the company hopes to test a steering mechanism consisting of 36 individual microrockets to provide lateral thrust. According to Gleich, the launch will test guidance and steering as well as a sapphire infra-red (IR) seeker window. A dual-mode radar/IR seeker is a potential guidance solution.
An earlier seeker window was lost in a previous test, after 900 milliseconds, having registered a temperature of 700íC. Surface heating because of friction is one of the major challenges the designers face with an infra-red seeker - the temperature of the window could obscure the target heat source - while attempts to steer such a high-speed missile aerodynamically are hampered by intense heating of the leading edges of control surfaces, which reach some 1,800íC at Mach 6, says Gleich.
Dasa is nevertheless looking at aerodynamic control in the SHORAD application. Various possible configurations of a hypersonic surface-to-air missile are being studied, involving a combination of lateral thrusters, conventional fins and "jet fins", a variant of the "grid fins" now seen on some Russian missiles.
Gleich says that jet fins provide an advantage over conventional fins in that they experience much lower moments for twice the steering response. Simulations suggest that these fins - especially if mounted forward on the missile body, for higher agility - could make side thrusters unnecessary unless the missile operates at higher altitudes.
The only problem is finding the right material to withstand the high temperatures experienced in flight. To date, the HFK's stub fins have been made of steel, but Gleich says that Dasa is now looking at ceramic fins. Jet fins are to be tested on an HFK missile in 1999.
Source: Flight International