SBIR-STTR Award

Conventional rockets all use a traditional bell nozzle. The nozzle represents lost weight from a payload point of view, but is necessary to direct thrust and ensure that the exhaust gas expands at the correct rate. However, this expansion velocity is dependent on the external air pressure, and for a rocket, that pressure is constantly changing. In other words, traditional bell nozzles are a compromise; while they are effective at optimizing thrust for a given external air pressure, they are less efficient at other points during the rocket's trajectory. Nozzle design traditionally involves selecting an external pressure to design to; in every other part of the trajectory, the rocket will be under or over expanded. The objective of this proposal is to obtain experimental flight data to validate a plug cluster aerospike design. In phase 1 of this proposal we will design and manufacture the thrust mount for the plug-cluster aerospike assembly. This will provide the thrust and other telemetry data for sea-level pressure conditions. In future phases we will collect suborbital flight data, utilizing a suborbital flight of the Firefly Alpha launch vehicle first stage, in addition to ground testing.

The objective of this proposal is to fully evolve a plug cluster aerospike design, moving from state-of-the-art computational analysis to manufacturing, ground testing, and then a full stage integration ground test. If the phase II option is exercised, the aerospike would be flight tested as well. The computational analysis is already well underway, with numerous studies producing results that have never before been published. The ground testing phase will start with a full plug cluster aerospike engine test in a horizontal configuration; our phase I effort laid the groundwork for this test to be carried out later this year. The engine test will be followed in the development cycle by a fully integrated first stage test where the engine, thrust structure, and tanks will be tested together in a vertical configuration. Construction of the vertical test stand flame trench has already begun. Finally, the phase II option would permit the last evolution in engine development: a suborbital flight test of the Firefly Alpha launch vehicle. This flight test data acquisition opportunity is the first of its kind, and we would capitalize on it by flying a highly instrumented aerospike to record and publish performance in unprecedented detail.