Indian researchers say they have tested a novel and simple way to reduce the drag and increase the range of high-speed missiles. In hypersonic shock-tunnel tests reported in the journal Physics of Fluids, the technique resulted in a 47% reduction of drag on a blunt cone representing the nosecone of a missile or space vehicle.
Blunt is better (Photo: Iron Man, Paramount Pictures)
Blunt noses are used to reduce the aerothermal loads on missiles at high speed, but they increase wave drag. Researchers at the Indian Institute of Science (IISc) in Bangalore tested various ways of reducing drag, including mounting an aerospike on, or ejecting a supersonic gas jet from, the tip of the nose. But these methods, while they work, are difficult to apply, they say.
In contrast, the technique tested by IISc is simple, and could be applied to existing missiles - including India's surface-to-air Agni, they note. Basically it involves coating the nose of the missile with a layer of chromium. When the nose heats up at hypersonic speed, the metal evaporates and reacts exothermally with the oxygen in the airflow. The heat released reduces the pressure and density behind the bow shockwave, which reduces the drag.
You can read the Times of India story here, and there is a link to the report here on IISc's website. Enjoy!