Mumbai: Scientists from the Indian Institute of Science (IISc), Bangalore have developed a new technology for increasing the range of high speed space vehicles including missiles.
“This technology reduces drag of high speed space vehicles which dictates the range of the missile for a given amount of fuel,” Prof K PJ Reddy of Department of Aerospace Engineering said.
“The thrust generated by the rocket engine must compensate for the drag encountered by the missile in its path,” he said.
“This technology involving spray coating of the high speed missiles and other space vehicles can be used in the existing stockpile of missiles,” Reddy, leading a team of scientists who developed it said.
“This method will ensure that without spending any additional energy the overall aerodynamic drag of the vehicle can be controlled and this in turn will improve the efficiency of the hypersonic flight of the vehicle. This is a very attractive technique for controlling aerodynamic drag of the vehicles flying at hypersonic Mach numbers,” Reddy said in the recent issue of Physics of Fluids Journal.
The technology has been demonstrated by the scientists Vijay Kulkarni, GM Hegde, G Jagdeesh and E Arunan of the high enthalpy aerodynamics laboratory in the Department of Aerospace Engineering.
“The IISc scientists have got Indian patent for the technology,” Reddy said.
The main advantages of this innovative hypersonic drag control techniques are that it is a completely passive device that is non-intrusive and does not need any additional power during the actual flight to control the aerodynamic drag of the missile flying at hypersonic speeds.
Also, the amount of heat energy released into the shock layer of the body can be altered to suitably control the aerodynamic drag of the hypersonic vehicle.
“The nose of the missile is essentially blunted in order to reduce the heating problem but the drag encountered by the blunt bodies when they travel at hypersonic speeds (five to six times the speed of sound approximately 2 km per second) is larger,” he said adding hence one way of increasing the range of the missile or any vehicle is to reduce the drag force.
“The new method involves a radically different technique in the sense that no additional device or power is required for controlling the aerodynamic drag in the proposed technique during the actual hypersonic flight,” Reddy said.
“The technique is to coat the nose portion of the missile with a thin layer of material such as chromium,” the aero scientist said.
“This metal coating evaporates due to the heating of the missile nose or vehicle during its hypersonic flight and the evaporated metal particles in atomic form react exothermically with the oxygen atoms surrounding the body to release additional heat into the air in front of the missile. This heat addition reduces the drag force up to about 47%,” he said.
In fluid dynamics, drag is the force that resists the movement of a solid object through a fluid. For a solid object moving through a fluid, the drag is the component of the net aerodynamic or hydrodynamic force.
One of the features of the new method is that it is expected to enhance the commercially viability of the technology.
In addition, this technique will also be useful for the development space vehicles which consume lesser fuels and thus reduce the cost of space travel in the future, Reddy added.
Asked how it can be considered as a breakthrough, Reddy said, “The existing techniques for reducing the drag force involve addition of an aero spike at the nose of the missile or blowing a supersonic gas jet from the missile nose tip.”
“Implementation of these techniques involves major modification to the missile structure and hence can not be applied to existing missiles which are in stockpile,” he said.
“While in the new technology developed by IISc, straight away you can spray the existing missiles or space craft without doing any modification,” he added.