Recent advances in the aerothermodynamics of spiked hypersonic vehicles

Effectiveness of aerospikes/aerodisk assemblies as retractable drag-reduction devices for large-angle blunt cones flying at hypersonic Mach numbers is investigated experimentally in hypersonic shock tunnel HST2 using a 120-deg apex-angle blunt cone. An internally mounted accelerometer balance system has been used for measuring the aerodynamic drag on the blunt cone with and without forward-facing aerospikes at various angles of attack. The measurements indicate around 55% reduction in drag for the blunt cone with flat-disk spike at zero degree angle of attack for a freestream Mach number of 5.75. Surface convective heat-transfer rate measurements have been carried out on the blunt cone with a flat-disk tipped spike of varying length in order to locate the shock reattachment point on the blunt-cone surface. The measured heat-transfer rates fluctuate by about ±20% in the separated flow region as well as near the reattachment point indicating the unsteady flowfleld around the spiked blunt cone. The shock structure around the 120-deg apex-angle blunt cone with a 12-mm-long flat-tipped aerospike has also been visualized using the electric discharge technique. The visualized shock structure and the measured drag on the blunt cone with aerospikes agree well with the axisymmetric numerical simulations

Experimental Investigations of Hypersonic Flow over Highly Blunted Cones with Aerospikes

Experimental investigation on drag and heat flux reduction in supersonic/hypersonic flows: A survey

Drag reduction and thermal protection is very important for hypersonic vehicles, and a counterflowing jet and its combinations is one of the most promising drag and heat release reduction strategies. In the current survey, research progress on the drag and heat release reduction induced by a counterflowing jet and its combinations is summarized. Three combinatorial configurations are considered, namely the combination of the counterflowing jet and a forward-facing cavity, the combination of the counterflowing jet and an aerospike, and the combination of the counterflowing jet and energy deposition. In conclusion, some recommendations are provided, especially for jet instability protection, for the tradeoff between drag and heat release reductions, and for the critical points for the operational and geometric parameters in the flow mode transition.

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A survey of drag and heat reduction in supersonic flows by a counterflowing jet and its combinations

Investigation of film cooling on nose cone by a forward facing array of micro-jets in Hypersonic flow

The requirements for the design of a new short-range high-velocity missile are both the drag reduction and the correct information acquisition for the optoelectronic sensors embedded in the hemispherical nose. High anglesof attack must be studied to fulfill the maneuverability requirements of present and future missiles. A supersonic missile generates a bow shock around its blunt nose, which causes rather high surface pressure and temperature and, as a result, the development of high drag and damage of embedded sensors. The pressure and the temperature on the hemispherical nose surface can be substantially reduced if an oblique shock is generated by a forward-facing spike. Both the experiments and the computations are carried out to study the flowfield around three-dimensional blunt bodies equipped with forward-facing spikes for a large range of attack angles at a Mach number of 4.5. A blunt body, a classical disk-tip spike, a sphere-tip spike, and a biconical-tip spike are studied. The experiments involve high-pressure shock tunnel investigations using a shock tube facility. The differential interferometry technique is applied to visualize the flowfield around the different missile spike geometries. The differential interferogram pictures as well as surface pressure measurements are compared with numerical results. Numerical simulations based on steady-state three-dimensional Navier-Stokes computations are performed to predict the drag, the lift, and the pitching moment for the blunt body and for each spike-tipped missile. The computations allow one to bring out the advantages of each spike geometry in comparison to the blunt body.

Flowfield Around Spike-Tipped Bodies for High Attack Angles at Mach 4.5

The requirements imposed by EADS Germany for the design of a new high-velocity missile V/SHORADS (Very/Short Range Air Defense System) are both the drag reduction and the correct information acquisition for the optoelectronic embedded sensors at even high angles of attack. High angles of attack must be studied to fulfill the maneuverability requirements of present and future missiles. A supersonic flow around the blunt nose of a missile generates a bow shock which causes a rather high surface pressure and, as a result, the development of a high drag. The pressure on the body surface can be substantially reduced if, instead of a normal shock, an oblique shock is generated by a forward facing spike. The spike reduces the drag as well as the temperature and protects the surface in the case of embedded sensors.

Flow field around spike-tipped bodies

The requirements imposed by EADS Deutschland GmbH for the design of a new high velocity missile V/SHORADS (Very/Short Range Air Defence System) are the reduction of drag and to obtain reliable information from the opto-electronic embedded sensors at even high angles of attack. The aim of our investigation is to find new spike geometries and to optimise these to reach high angles of attack without losing the drag reduction effect well-known for small angles of attack. Flow visualisation pictures taken with differential interferometry are shown. A classical disk spike geometry is compared with a new spherical spike and the advantages of the latter are discussed. For equal diameters and lengths the disk spike proves to be more efficient below 8° whereas the sphere spike is more efficient beyond this angle of attack. Pressure measurements are presented and compared to the numerical calculations.

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J. Srulijes

Papers

Flowfield Around Spike-Tipped Bodies for High Attack Angles at Mach 4.5

Flow field around spike-tipped bodies

Flow Visualisation, Pressure Measurements and Numerical Calculations on Spike-Tipped Bodies