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NASA’s X-59, seen in this illustration, is designed to fly faster than sound but generate quieter sonic “thumps” rather than booms. Credit: Lockheed Martin
NASA is set to test improved tools for assessing the quieter sonic thumps produced by its X-59 supersonic aircraft.
These tools include a shock-sensing probe that collects detailed pressure data from shock waves generated during supersonic flight. These probes, crucial for validating the computer models that predict shock wave strength, come in two versions targeting different measurement fields, and will be tested using an F-15B aircraft in various flight configurations.
NASA’s Sonic Thump Measurement Tool
NASA is preparing to test advancements in a key tool designed to measure the distinctive “sonic thumps” produced by its quiet supersonic research aircraft, the X-59.
This tool, known as a shock-sensing probe, is a cone-shaped air data device specifically engineered to capture the unique shock waves generated by the X-59. Researchers at NASA’s Armstrong Flight Research Center in Edwards, California, have developed two versions of the probe to collect precise pressure data during supersonic flight. One version is optimized for near-field measurements, capturing shock waves close to the aircraft’s source. The other probe is designed for mid-field measurements, gathering data at altitudes ranging from 5,000 to 20,000 feet below the X-59.
A close-up of NASA’s shock-sensing probe highlights its pressure ports, designed to measure air pressure changes during supersonic flight. The probe will be mounted on NASA’s F-15B Aeronautics Research Test Bed for calibration flights, validating its ability to measure shock waves generated by the X-59 as part of NASA’s Quesst mission to provide data on quiet supersonic flight. Credit: NASA/Lauren Hughes
Supersonic Flight Testing and Data Collection
When an aircraft flies supersonic, it generates shockwaves that travel through the surrounding air, producing loud sonic booms. The X-59 is designed to divert those shock waves, reducing the loud sonic booms to quieter sonic thumps. During test flights, an F-15B aircraft with a shock-sensing probe attached to its nose will fly with the X-59. The roughly 6-foot probe will continuously collect thousands of pressure samples per second, capturing air pressure changes as it flies through shock waves. Data from the sensors will be vital for validating computer models that predict the strength of the shock waves produced by the X-59, the centerpiece of NASA’s Quesst mission.
NASA’s F-15B Aeronautics Research Test Bed performs a calibration flight of the shock-sensing probe over Edwards, California, on August 6, 2024. The probe will measure shock waves from NASA’s X-59, providing data that may change limits for overland supersonic flight from being speed-based to sound-based. This work is part of NASA’s Quesst mission, with the X-59 as its flagship aircraft. Credit: NASA/Steve Freeman
“A shock-sensing probe acts as the truth source, comparing the predicted data with the real-world measurements,” said Mike Frederick, NASA principal investigator for the probe.
For the near-field probe, the F-15B will fly close behind the X-59 at its cruising altitude of approximately 55,000 feet, utilizing a “follow-the-leader” setup allowing researchers to analyze shock waves in real-time. The mid-field probe, intended for separate missions, will collect more useful data as the shock waves travel closer to the ground.
During a test flight over Edwards, California, NASA’s F-15B Aeronautics Research Test Bed evaluates a shock-sensing probe. The probe will capture detailed shock wave data from the X-59, advancing research in quiet supersonic travel. Credit: NASA/Steve Freeman
Advances in Shockwave Analysis Technology
The probes’ ability to capture small pressure changes is especially important for the X-59, as its shock waves are expected to be much weaker than those of most supersonic aircraft. By comparing the probes’ data to predictions from advanced computer models, researchers can better evaluate their accuracy.
“The probes have five pressure ports, one at the tip and four around the cone,” said Frederick. “These ports measure static pressure changes as the aircraft flies through shock waves, helping us understand the shock characteristics of a particular aircraft.” The ports combine their measurements to calculate the local pressure, speed, and direction of airflow.
NASA’s F-15B Aeronautics Research Test Bed, equipped with a shock-sensing probe, soars over Edwards, California. The probe’s data will help refine supersonic flight models and support NASA’s mission to reduce sonic booms to quieter “sonic thumps.” Credit: NASA/Steve Freeman
Upgrades to Shock-Sensing Technology
Researchers will soon evaluate upgrades to the near-field shock-sensing probe through test flights, where the probe, mounted on one F-15B, will collect data by chasing a second F-15 during supersonic flight. The upgrades include having the probe’s pressure transducers – devices that measure the air pressure on the cone – just 5 inches from its ports. Previous designs placed those transducers nearly 12 feet away, delaying recording time and distorting measurements.
NASA’s F-15B Aeronautics Research Test Bed flies over Edwards, California, carrying a shock-sensing probe designed to measure supersonic shock waves from the X-59. This crucial data supports NASA’s Quesst mission to enable quieter supersonic flight over land. Credit: NASA/Steve Freeman
Temperature sensitivity on previous designs also presented a challenge, causing fluctuations in accuracy with changing conditions. To solve this, the team designed a heating system to maintain the pressure transducers at a consistent temperature during flight.
“The probe will meet the resolution and accuracy requirements from the Quesst mission,” Frederick said. “This project shows how NASA can take existing technology and adapt it to solve new challenges.”
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