Contour design and test studies of a round to square aerospike nozzle

Simple design methods of round to square inner nozzle contour and plug contour of the aerospike nozzle were presented. The inner nozzle contour was described by two circular arcs and a parabola; the plug contour was described by a parabola and a third-order curve. And the results of hot-firing tests on a 1-cell linear aerospike nozzle engine with round to square inner nozzle were given, using oxygen as oxidant and hydrogen as fuel. Design parameters and structure photographs of the experimental engine, the test apparatus and ignition method were introduced. Curves measured in the tests, test photographs and data analyse were also provided. At three altitudes, thrust coefficient efficiencies vary within the range of 93% to 98%, which is shown that the test aerospike nozzle engine maintain high thrust efficiency. It is proved that the design and test methods of the aerospike nozzle are feasible.