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NASA intends to test improved tools to assess the quiet sonic booms produced by the X-59 supersonic aircraft. These instruments include a shock sensor that collects detailed pressure data from shock waves generated during supersonic flight. These probes, important for validating computer models that predict shock wave strength, are available in two versions targeting different measurement fields and will be tested using the F-15B aircraft in various flight configurations.
NASA instrument for measuring the sound shock
NASA is preparing to test progress on a key instrument designed to measure the distinctive "sonic booms" produced by its quiet X-59 supersonic research aircraft. This instrument, known as a shock sensor, is a cone-shaped air data device specifically designed 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 accurate pressure data during supersonic flight. One version is optimized for near-field measurements, picking up shock waves close to the aircraft source. Another probe is designed for mid-field measurements, collecting data at altitudes between 5000 and 20 feet below the X-000.
Supersonic flight testing and data collection
When a plane flies supersonic, it generates shock waves that travel through the surrounding air, creating a loud sonic boom. The X-59 is designed to deflect these shock waves, reducing loud sonic booms to quieter sonic booms. During test flights, an F-15B with a shock sensor attached to its nose will fly with the X-59. The roughly 6-foot probe will continuously collect thousands of pressure samples per second, recording changes in air pressure as it flies through the shock waves. Data from the sensors will be vital for validating computer models that predict the strength of shock waves generated by X-59, the centerpiece of NASA's Quest mission.
"The impact-sensing probe acts as a ground-truth by comparing predicted data with real-world measurements," said Mike Frederick, NASA's principal investigator for the probe.
For the near-field probe, the F-15B will fly close to the X-59 at a cruising altitude of about 55 feet, using a "follow the leader" setting that allows researchers to analyze the shock waves in real time. The midfield probe, designed for separate missions, will collect more useful data as the shock waves approach the ground.
Advances in shock wave analysis technology
The probes' ability to pick up small pressure changes is especially important for the X-59 because its shock waves are expected to be much weaker than most supersonic aircraft. By comparing probe data with predictions from advanced computer models, researchers can better assess their accuracy.
"The probes have five pressure holes, one at the tip and four around the cone," Frederick said. "These ports measure changes in static pressure as the aircraft flies through the shock waves, helping us understand the impact characteristics of a particular aircraft." The ports combine their measurements to calculate local pressure, velocity and direction of airflow.
Impact recognition technology update
Researchers will soon evaluate the upgrade to the near-field impact sensor during test flights, where a probe mounted on one F-15B will collect data while chasing a second F-15 during supersonic flight. The upgrades include placing the probe's pressure sensors – the devices that measure air pressure on the cone – just 5 inches from its ports. In previous designs, these transducers were placed nearly 12 feet apart, delaying recording times and distorting measurements.
The temperature sensitivity of earlier designs was also a problem, causing accuracy to fluctuate with changing conditions. To solve this problem, the team developed a heating system to maintain a constant temperature of the pressure sensors during flight.
"The probe will meet the resolution and accuracy requirements of the Quest mission," Frederick said. "This project shows how NASA can take existing technologies and adapt them to solve new challenges."
