NASA is planning to fly its F-15B jets through supersonic shock waves in order to help test its revolutionary X-59 jet.
When aircraft break the sound barrier, they produce shock waves that reverberate through the surrounding air and produce the thunderous sonic booms typically associated with supersonic flight. The X-59, developed by Lockheed Martin and NASA, was designed with a radical new geometry that could help reduce these booms down to a much quieter "thump."
To help the agency measure these thumps, NASA's Armstrong Flight Research Center is planning to fly an F-15B research aircraft behind the X-59 during supersonic flight, carrying two specially designed probes that will collect "precise pressure data" about the X-59's shock waves, according to a NASA statement. The agency says this "follow-the-leader" arrangement will allow scientists to analyze data from shock waves in real time just behind where the X-59 will produce them.
Small ports, or holes, on the probes will measure air pressure, speed and direction during flight, collecting thousands of samples per second. These measurements will allow NASA scientists to compare what they observe during the X-59's test flights to data from simulations and models.
"A shock-sensing probe acts as the truth source, comparing the predicted data with the real-world measurements," said Mike Frederick, NASA's lead investigator for the probes that will fly on the agency's F-15Bs, in the agency's statement.
One of the probes mounted on an F-15B will measure the near-field shockwaves produced close behind the X-59 while in flight, while another "mid-field probe" will be used in later testing to measure shock wave data closer to the ground.
To aid in the X-59 test campaign, NASA has also been flying its F-15D Eagle and F/A-18 Hornet support aircraft over microphones set up throughout test airspace near its Armstrong Flight Research Center in the western Mojave Desert.
The agency is "learning to listen to the X-59" with these flights, which see the jets perform inverted (upside-down) dives that produce "softer" sonic booms. These recordings will be later compared against recordings of the sonic booms expected to be produced by the X-59.
The X-59 is designed to fly faster than the speed of sound without generating the thunderous sonic booms that are typically produced during supersonic flight. Those booms are the reason supersonic flight above land within a certain distance of the U.S. have been prohibited since 1973.
If the technologies and concepts being tested with the X-59 successfully reduce the noise produced by breaking the sound barrier, we could someday see supersonic planes approved once again for commercial air travel, revolutionizing not only civilian flight but also disaster relief and medical transport.
After years of development and delays stemming from the COVID-19 pandemic, the X-59 was unveiled to the public at a glitzy ceremony in January 2024. The aircraft passed its Flight Readiness Review four months later and fired its engine for the first time in November 2024.
A date has not yet been set for the jet's first test flight.
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