Linear Aerospike SR-71 Experiment (LASRE) dumps water after first in-flight cold flow test.
The NASA/Lockheed Martin Linear Aerospike SR-71 Experiment (LASRE) concluded its flight operations phase in November 1998. The experiment's goal was to provide in-flight data to help Lockheed Martin validate the computational predictive tools they are using to determine the aerodynamic performance of a future potential reusable launch vehicle.
Information from the LASRE experiment helped Lockheed Martin maximize its design for a future potential reusable launch vehicle. It gave Lockheed an understanding the performance of the X-33 lifting body and linear aerospike engine combination.
LASRE was 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-71 aircraft, operated like a kind of "flying wind tunnel." The experiment focused on determining how a reusable launch vehicle'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 project, 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. The first of those two flights occurred Oct. 31, 1997. The SR-71 took off at 8:31 a.m. PST. The aircraft flew for one hour and fifty minutes, reaching a maximum speed of Mach 1.2 and a maximum altitude of 33,000 feet before landing at Edwards at 10:21 a.m. PST, successfully validating the SR-71/pod configuration.
Linear Aerospike SR-71 Experiment (LASRE) during first in-flight cold flow test.
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. The first of these flights occurred March 4, 1998. The SR-71 took off at 10:16 a.m. PST. The aircraft flew for one hour and fifty-seven minutes, reaching a maximum speed of Mach 1.58 before landing at Edwards at 12:13 p.m. PST.
During three more flights in the spring and summer of 1998, liquid oxygen was cycled 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. The ground firings and the airborne cryogenic gas flow tests provided enough information to predict the hot gas effects of an aerospike engine firing during flight.