NASA News Release 98-79
November 20, 1998

NASA and Lockheed Martin officials have announced conclusion of the flight operations phase of the Linear Aerospike SR-71 Experiment (LASRE).

Data analysis will continue for some weeks, but according to Lockheed Martin Skunk Works Vice President Jerry Rising, findings from the experiment will prove very valuable to the ongoing VentureStarTM design process.

"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."

LASRE is a small, half-span model of a lifting body with eight thrust cells of an aerospike engine. The experiment, mounted on the back of an SR-71aircraft, operates like a kind of "flying wind tunnel." 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 miles per hour. The interaction of the aerodynamic flow with the engine plume could create drag; design refinements look to minimize that interaction.

During the flight research program, the aircraft completed seven research flights. Two initial flights were used to determine the aerodynamic characteristics of the LASRE apparatus on the back of the aircraft. Five follow-on flights focused on the experiment; two were used to cycle gaseous helium and liquid nitrogen through the experiment to check its plumbing system for leaks and to check engine operation characteristics; and three were used to cycle liquid oxygen through the engine. In addition, two engine hot firings were conducted on the ground.

It was decided not to do a final hot-fire flight test due to the liquid oxygen leaks in the test apparatus. "We learned enough from the ground firings and the airborne cryogenic gas flow tests to predict the hot gas effects of an aerospike engine firing during flight," said Rising.

In addition to refining and enhancing confidence in predictive tools that will be used in finalizing the design of VentureStar, Rising said that LASRE has amassed a wealth of information on how to get reusable launch vehicle hardware ready for flight and to keep it flying.