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Supersonic flight became a reality in October 1947, when the Bell X-1 rocket plane broke the sound barrier. NASA’s Lewis Research Center in Cleveland (now NASA Glenn), which had served as the agency’s aeropropulsion lead since its creation in the 1940s., He later helped NASA advance the technology needed to make longer supersonic flights possible.
A large number of military aircraft capable of reaching supersonic speeds followed the Bell X-1. In the 1960s, Lockheed’s family of Blackbirds (the original A-12, the YF-12 interceptor, and the SR-71 reconnaissance vehicle) became the world’s first aircraft capable of flying at supersonic speeds for extended periods. . However, expanding this capability to larger transport aircraft was difficult, largely due to a lack of data collected on propulsion systems during longer supersonic flights.
To solve problems that were not found during the design phase testing of these aircraft and advance crucial technology, such as the mixed compression supersonic inletthe military provided two YF-12s retired to the Dryden Flight Research Center (now NASA Armstrong) in 1969 as part of a collaborative effort between NASA and the Air Force. They planned to compare YF-12 flight data with data collected in wind tunnels at NASA’s Ames, Langley, and Lewis Research Centers.
Lewis researchers had studied supersonic inlets in wind tunnels since the early 1950s and were in the midst of a comprehensive evaluation of supersonic nozzles and inlets using a Delta F-106 Dart. In this new effort, Lewis was responsible for testing a full-scale YF-12 entry in the center’s 10×10 supersonic wind tunnel and analyzing a 32,500-pound-thrust Pratt & Whitney J58 engine at the Aircraft Systems Laboratory. Propulsion (PSL).
Although mixed compression inlets, which allowed the engines to operate as turbojets at subsonic speeds and as ramjets at higher Mach numbers, were very efficient, their design left the engines vulnerable to flow disturbances that often caused “no starts”. The pullouts produced instantaneous drag that could stall the engine or cause the aircraft to roll or yaw rapidly. Lewis researchers tested an actual intake from a crashed SR-71, which they installed in the 10×10 in November 1971.
Over the next year, the researchers collected aerodynamic data under different conditions in the wind tunnel. They also tested a new intake control system patented by Lewis engineers Bobby Sanders and Glenn Mitchell, which used mechanical valves to protect the aircraft from starts. It was the first time the system was tested on a large-scale piece of hardware.
The researchers also studied the relationships between the airframe, intake, engine and control system during normal flight conditions and when experiencing realistic flow disturbances.
In the summer of 1973, a full-scale J-58 engine became the first hardware tested at Lewis. New second PSL altitude camera. Over the next year, researchers captured data under normal conditions and while using mesh intake screens to simulate airflow distortions in flight.
The PSL tests also measured engine emissions as part of a larger effort to determine the high-altitude emissions levels of potential supersonic transports.
Although the YF-12 program ended in 1979 as the agency’s aeronautical priorities changed, a year of ground testing in NASA’s wind tunnels had already been completed and the YF-12s had completed nearly 300 research flights. The program had expanded to include the development of high temperature instrumentation, fuselage pressure and flow mapping, thermal loads, and the entry control system.
NASA engineers demonstrated that small-scale models could be successfully used to design large-scale supersonic inlets, while flight data was used to better understand the effect of subscale models and tunnel interference on the data. Perhaps most importantly, Lewis’s program led to a digital control system that improved the response of the supersonic intake to flow disturbances, nearly eliminating engine restarts.
Many of the program’s concepts were integrated into the SR-71 design in the early 1980s and have contributed to NASA’s continued efforts over the decades. to achieve a supersonic transport aircraft.
Additional Resources:
Mach 3+ NASA/USAF YF-12 Flight Research, 1969-1979 by Peter Merlin
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