Experimental Results on the Feasibility of an Aerospike for Hypersonic Missiles

A series of wind tunnel tests have been performed on an aerospike-protected missile dome at a Mach number of 6 to obtain quantitative surface pressure and temperature-rise data, as well as qualitative flow visualization data. These data were used to determine aerospike concept feasibility and will also provide a database to be used for calibration of computational fluid dynamics codes. Data were obtained on the hemispherical missile dome with and without an aerospike that protrudes ahead of the dome along the axisymmetric center line. Data were obtained on two models (one pressure, one temperature) in the NASA Langley 20-Inch Mach 6 Tunnel at a freestream Reynolds number of 8.0x106/ft and angles of attack from 0 to 40 degrees. Surface pressure and temperature-rise results indicate that the aerospike is effective for very low angles of attack (<5 degrees) at Mach 6. Above 5 degrees, impingement of the aerospike bow shock and the flow separation shock from the recirculation region created by the aerospike causes pressure and temperature increases on the windward side of the dome which exceed values observed in the same region with the aerospike removed. Flow characterization obtained via oil-flow and schlieren photographs provides some insight into the quantitative surface data results, including vortical flow and shock-wave impingement. Introduction The aerospike concept is proposed as a promising dome assembly design for high-speed tactical guided missiles. The concept was first conceived in the 1950s as a means of reducing the heat transfer rates and aerodynamic drag on axisymmetric blunt bodies1-4. In fact, the spiked-nose concept was successfully incorporated into the design of the C-4 and D-5 trident missiles and reduced the drag of these vehicles by up to 50% at Mach numbers as high as 85. At Mach numbers from 3 to 8, the surface pressures and aerothermodynamic heating rates collectively may be severe enough to cause failure of the hemispherical dome material. Conceptually, the aerospike creates a conical region of recirculatory flow in front of the hemisphere dome that shields and protects it from the oncoming freestream flow. Furthermore, an addition to the end of the aerospike, known as an aerodisk, can be used to allow a fixed length aerospike to be effective over a wide range of Mach numbers by fixing the separation of the boundary layer near the front of the aerospike which creates the recirculation region regardless of Mach number. The aerospike/aerodisk configuration, along with the induced flowfield, is shown schematically in figure 1. The configuration consists of a hemispherical dome mounted to a cylindrical body. Attached to the dome along the axisymmetric centerline is the aerospike/aerodisk assembly. At low hypersonic * Aerospace Engineer, Hypersonic Airbreathing Propulsion Branch, Gas Dynamics Division, MS 168, Hampton, VA 23681-0001, AIAA Senior Member. ✝ Research Engineer, USAF Wright Laboratory, Armament Directorate, Eglin AFB, FL 32542-5434,