SR-71 LASRE during in-flight cold flow test

This shot, from above and behind the SR-71 in flight, runs 11 seconds and shows the Aerospike engine and its fuel system being charged with gaseous helium and liquid nitrogen during one of two tests. The tests are to check for leaks and check the flow characteristics of cryogenic fuels to be used in the engine.

The NASA/Lockheed Martin Linear Aerospike SR-71 Experiment (LASRE) concluded its flight operations phase at the NASA Dryden Flight Research Center, Edwards, California, in November 1998. The goal of this experiment was to provide in-flight data to help Lockheed Martin, Bethesda, Maryland, validate the computational predictive tools it was using to determine the aerodynamic performance of a future potential reusable launch vehicle.

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, operates like a kind of "flying wind tunnel." The experiment focused on determining how the engine plume of a reusable launch vehicle 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. The first of those two flights occurred October 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, California, at 10:21 a.m. PST, successfully validating the SR-71/pod configuration.

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 1 hour and 57 minutes, reaching a maximum speed of Mach 1.58 before landing at Edwards, California, at 12:13 p.m. PST.

During further 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 as a result of 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.

The experiment itself was a small, half-span model that contained eight thrust cells of an aerospike engine and was mounted on a housing known as the "canoe," which contained the gaseous hydrogen, helium and instrumentation.

The model, engine, and canoe together were called the "pod." The entire pod was 41 feet in length and weighed 14,300 pounds. The experimental pod was mounted on the NASA SR-71, on loan to NASA from the U.S. Air Force. The X-33 program was cancelled in early 2001.

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