NASA plans to test advanced instruments to evaluate the silent sonic booms produced by the X-59 supersonic aircraft. These devices contain a shock sensor that collects detailed pressure data from the shock waves produced during supersonic flight. These probes, which are important for validating computer models that predict shock wave power, are available in two versions targeting different measurement areas and will be tested in various flight configurations using the F-15B aircraft.

NASA device to measure sound shock

NASA is preparing to test progress on a key device designed to measure the distinctive “sonic booms” produced by the quiet X-59 supersonic research aircraft. Known as a shock sensor, it is a cone-shaped airborne data device specifically designed to capture the unique shock waves produced 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 by collecting shock waves close to the aircraft source. Another probe is designed for midfield measurements, collecting data at altitudes 5,000 to 20,000 feet below X-59.

Supersonic flight testing and data collection

When an airplane flies supersonic, it creates shock waves that travel through the surrounding air, creating a loud sonic boom. The X-59 is designed to deflect these shock waves by reducing loud bursts of sound to quieter bursts of sound. The F-15B, which had a shock sensor installed in its nose during test flights, will fly together with the X-59. The approximately 1.8-meter probe will continuously collect thousands of pressure samples per second and record changes in air pressure as it flies through shock waves. Data from the sensors will be vital to validating computer models that predict the strength of shock waves produced by X-59, the centerpiece of NASA’s Quest mission.

“The impact detection probe serves as a ground truth by comparing predicted data to 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 approximately 55,000 feet using a “follow the leader” setting that allows researchers to analyze 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 shockwave analysis technology

The probes’ ability to detect small pressure changes is particularly important for the X-59 because its shock waves are expected to be much weaker than those of most supersonic aircraft. By comparing probe data with predictions from advanced computer models, researchers can better evaluate their accuracy.

“The probes have five pressure holes, one at the tip and four around the cone,” Frederick said. “These ports help us understand the shock characteristics of a particular aircraft by measuring changes in static pressure as the aircraft flies through shock waves.” Ports combine measurements to calculate local pressure, speed, and direction of airflow.

Effect recognition technology update

Researchers will soon evaluate an upgrade to the near-field impact sensor during test flights, where the probe mounted on an F-15B will collect data while chasing a second F-15 during supersonic flight. Upgrades include placing the probe just 5 inches away from the ports of pressure sensors (devices that measure air pressure on the cone). In previous designs, these transducers were spaced approximately 12 feet apart, which delayed recording times and distorted measurements.

Temperature sensitivity of earlier designs was also an issue, causing accuracy to fluctuate with changing conditions. To solve this problem, the team developed a heating system that would keep the temperature of the pressure sensors constant 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.”