EXPERIMENTAL ENGINE TEST GIVES VALUABLE INSIGHT.

Byline: Jim Skeen Daily News Staff Writer

Lockheed Martin Skunk Works has concluded an experiment on a scale-model rocket engine without conducting a planned test firing atop an SR-71 jet.

Lockheed Martin officials say the one-tenth scale linear aerospike engine was troubled by liquid oxygen leaks, and they had derived enough information in two firings on the ground and five flights to test engine characteristics and gas flows.

``We learned enough from the ground firings and the airborne cryogenic gas flow tests to predict the hot gas effects of an aerospike engine during flight,'' said Jerry Rising, Lockheed Martin's vice president for the X-33/VentureStar program.

The $20 million linear aerospike experiment tested a 14,300-pound scale model of the unconventional rocket engine that will be used to power the X-33 rocket plane and the proposed VentureStar spacecraft.

The aerospike lacks the usual bell-shaped exhaust nozzle of traditional rocket engines. Instead, the aerospike uses atmospheric pressure as part of its nozzle, with the surrounding airflow containing the rocket's exhaust plume.

This allows the engine to adjust during its orbital ascent to stay at optimum performance, whereas traditional engines cannot compensate for atmospheric changes, officials said.

The aerospike engine will be used for the X-33, a suborbital aircraft, and its planned follow-on project, VentureStar, a spacecraft aimed at dramatically reducing the cost of getting satellites and other payloads into space.

The experiment focused on determining how the VentureStar's engine plume would affect the aerodynamics of its lifting body shape at specific altitudes and speeds reaching approximately 750 mph.

The interaction of the aerodynamic flow with the engine plume could create drag, and design refinements will aim to minimize that interaction.

``The data we've received from the experiment will help us validate our computational predictive tools we're using to determine VentureStar's aerodynamic performance,'' Rising said. ``That will certainly help us maximize our design as we approach our initial design review in late next year. It gives us a leg up on understanding the performance of the lifting body and linear aerospike engine combination even before we test fly X-33.''

The experiment also provided a wealth of information to the Skunk Works about how to get reusable launch vehicle hardware ready for flight, Rising said.

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PHOTO An experimental aerospike rocket engine sits atop an SR-71 jet.