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Trident I first launch on 18 January 1977 at Cape Canaveral, showing the aerospike

A Drag Reducing Aerospike is a device used to reduce the forebody pressure drag of blunt bodies at supersonic speeds. The aerospike creates a detached shock ahead of the body. Between the shock and the forebody a zone of recirculating flow occurs which acts like a more streamlined forebody profile, reducing the drag.

This concept was first introduced on the Trident missile and is estimated to have increased the range by 550 km. The Trident aerospike consists of a flat circular plate mounted on an extendible boom which is deployed shortly after the missile breaks through the surface of the water after launch from the submarine. The use of the aerospike allowed a much blunter nose shape, providing increased internal volume for payload and propulsion without increasing the drag. This was required because the Trident I C-4 was fitted with a third propulsion stage to achieve the desired increase in range over the Poseidon C-3 missile it replaced. To fit within the existing submarine launch tubes the third stage motor had to be mounted in the center of the post-boost vehicle with the reentry vehicles arranged around the motor.

Further development of this concept has resulted in the air-spike ^[1]. This is formed by concentrated energy, either from an electric arc torch or a pulsed laser, projected forwards from the body, which produces a region of low density hot air ahead of the body. This has the advantage over a structural aerospike that the air density is lower than that behind a shock wave providing increased drag reduction.

In 1995 at the 33rd Aerospace Sciences Meeting it was reported that tests were performed at an aerospike-protected missile dome to Mach 6, obtaining quantitative surface pressure and temperature-rise data on the feasibility of using aerospikes on hypersonic missiles.

• Trident missile

1. ^ Golovitchev, V.I., Tretjakov, P.K., "Evaluation of Drag Reduction of Blunt Bodies at Supersonic Speeds by Counter-flow Combustion", AIAA 2002-3296

• http://techreports.larc.nasa.gov/ltrs/PDF/aiaa-95-0737.pdf.

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