Bangalore. A team of multi disciplinary researchers at the Bangalore-based Indian Institute of Science (IISc) has devised innovative, simple and cost effective techniques to improve the efficiency and range of military missiles and civilian space vehicles moving at hypersonic five to six times the speed of sound) speeds.

According to Dr K P J Reddy of its Aerospace Engineering Department, ts researchers have developed a novel method to reduce the drag generated during flight by pushing out the heat generated around the nose portion of a space vehicle or missile, and without necessitating any changes in the structural designs.

For it is a simple and easy to adopt process, involving the coating of the nose cone with a layer of chromium. This coating evaporates due to the heating of the missile nose during its flight through the atmosphere and the evaporated metal particles in atomic form react exothermally with atmospheric oxygen to push out some of this heat.

IISc is now in its centenary year. Its findings could have major implications in reducing the weight of the carrier vehicles.

It may be noted that the large aerodynamic drag which missiles and space vehicles flying in hypersonic speeds experience through the dense atmosphere makes for their vastly reduced thrust and decreased payload capability. That explains the massive difference in the launch weight of a vehicle and that of its payload.

For instance, India’ s high performance, three-stage GSLV MK-III space vehicle now under development with a liftoff weight of 629-tonnes, can deliver just a 10-tonne satellite payload into a near earth orbit.

Normally, the nose cone of a missile or a launch vehicle is blunted with a view to reduce the generation of heat and in turn the drag force. Till now most of the techniques meant for drag reduction focused mainly on vehicles moving at supersonic speeds.

Space vehicles or missiles mostly use solid chemical propellants, and much of the power generated by them is wasted by the drag.

Against this backdrop, IISc researchers initiated a project to investigate the possibility of developing a drag reduction technique for blunt body configuration vehicle traveling at hypersonic speeds.

Techniques that are currently in vogue for drag reduction involve the addition of an aero-spike at the nose-tip of the missile or blowing a supersonic gas jet ejecting from the nose-tip of the vehicle. Clearly and apparently, these techniques cannot be introduced in the existing stockpile of missiles or launch vehicles as that would warrant a modification in their designs.

The dynamics of IISc process is estimated to bring down the incidence of drag force by 47%.

According to DR Reddy, the advantages of the hypersonic drag reduction technique pioneered by IISc scientists include the flexibility of suitably controlling the aerodynamic drag of the vehicle by altering the quantum of heat energy released and its passive, non-intrusive nature.

As things stand now, the successful application of this research finding could bring down the cost of launching per kg of a hypersonic vehicle threefold to US$600 from US$ 20,000. Efforts are also being made to extend the scope of this technique to improve the efficiency, and in turn, reduce the launch cost of a space vehicle.

As pointed out by Dr. Reddy, by going in for this technique it is possible to launch a missile with a velocity of 9-km per second instead of 11-km per second.

In a related development, the space gun system with an electric propulsion now being experimented by the US National Aeronautics and Space Administration (NASA) holds the hope of brining down the cost of satellite launchings to a substantial extent. However, the hitch here is the massive generation of heat and in turn a high aerodynamic drag impacting on the vehicle.

It is here that the IISc technique of drag reduction assumes significance.