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Information from the LASRE project provided Lockheed Martin with design information for a potential reusable launch vehicle (RLV).
It gave Lockheed an understanding of the performance of a lifting body and linear aerospike engine combination.
The LASRE project concluded its flight operations phase in November 1998.
The goal of the experiment was to provide in-flight data to help Lockheed Martin validate the computational predictive tools it has been using to determine the aerodynamic performance of a future potential RLV.
LASRE included a 20-percent-scale, half-span model of the X-33 (minus the fins) that was rotated 90 degrees.
The engine is made primarily from copper and copper alloys and is water-cooled.
A 0.3 inch-thick layer of silicone ablative protects the reflection plane from the impingement of the rocket engine exhaust.
This material degrades with use but is intended to last the life of the test program.
It 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 gear.
The model, engine, and canoe together were called the "pod."
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Theoratically, a major advantage of the aerospike rocket engine is the ability of the nozzle to adjust with altitude changes to the free-stream static pressure, which results in a higher specific impulse than a conventional bell nozzle has at low altitudes.
This altitude compensation is caused by the unique nozzle geometry of the aerospike engine, which has a central ramp terminating in either a plug base or spike in the center and is scarfed, or open, to the atmosphere on the sides.
The nozzle exhaust flow is free to expand on the open sides and self-adjust to staticpressure changes with altitude. The compensation of the exhaust gases allows the nozzle to run a more optimum conditions than a conventional bell-type nozzle. |  |
Buried inside the pod are the tankage, plumbing, valves, instrumentation, and controllers required to operate the aerospike rocket engine, making the system essentially self-contained.
The LASRE propellant feed system is a pressure-fed system that supplies gasous hydrogen fuel and liquid oxygen to the aerospike engine.
In addition to being used as a purging gas, high-prssure gaseous helium is used as a pressurant to move the oxidizer and cooling water.
The entire pod was 41 feet in length and weighed 14,300 pounds.
The experimental pod was mounted on NASA's SR-71, on loan to NASA from the U.S. Air Force.
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The experiment, mounted on the back of an SR-71 aircraft, simulated the operation of the X-33.
The experiment focused on determining how a the X-33's engine plume would affect the aerodynamics of its lifting-body shape at specific altitudes and at speeds reaching approximately 750 miles per hour.
The interaction of the aerodynamic flow with the engine plume could create drag; design refinements looked to minimize that interaction.
During the flight research program, the aircraft completed seven research flights from NASA's Dryden Flight Research Center, Edwards, CA.
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 1 hour and 50 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.
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 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.
A final hot-fire flight test did not take place due to 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.
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