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NASA will soon put to the test the advances made in a key tool to measure the singular ‘sonic shocks’ that its supersonic silent research aircraft X-59 will produce during flight.
An impact detection probe, a cone-shaped air data probe developed with specific characteristics to capture the singular shock waves that the X-59 will produce. Investigators at NASA’s Armstrong Flight Research Center in Edwards, California, developed two versions of the probe to collect accurate pressure data during supersonic flight. One of the probes is optimized for close field measurements, capturing shock waves that are produced very close to where the X-59 will generate them. The second impact detection probe will measure the center of the field and collect data at altitudes between 5,000 and 20,000 feet below the plane.
When an airplane flies at supersonic speeds, it generates shock waves that travel through the surrounding air, producing strong sound waves. The X-59 is designed to deflect these shock waves, reducing the strongest sonic shocks to quieter sonic shocks. During the test flights, an F-15B aircraft with an impact detection probe attached to its nose will fly with the X-59. The probe, approximately 1.80 meters (6 feet), will continuously collect thousands of pressure samples per second, capturing changes in air pressure while flying through shock waves. The data from the sensors will be vital to validate the computer models that predict the force of the shock waves produced by the X-59, the central piece of NASA’s Quest mission.
“Una sonda de detection de impactos actua como fuente de la verdad, comparando los datos previstos con las mediciones del mundo real”, dijo Mike Frederick, the investigation principal de la NASA para la Sonda.
Para la sonda de campo cercano, the F-15B will fly around the X-59 at a cruise altitude of approximately 18,000 meters (55,000 feet), using a “follow the leader” configuration that is envisioned by real-time investigations. La sonda de campo medio, destinada para misiones separadas, will recopilará data más utiles as medida que las ondas choque travelen más cerca al suelo.
The ability of the probes to capture small changes in pressure is especially important for the X-59, since its shock waves are expected to be much weaker than those of most supersonic aircraft. Al comparar los datos de las sondas con las predictions de modelos computadora avanzades, los researchers pueden evaluar con precisión.
“Las sondas tienen cinco puertos de presión, uno en la punta y cuatro alrededor del cono”, explained Frederick. “Estos puertos miden los cambios de presión estática a medida que el avión vela través de las ondas choque, lo que ayuda nos comprender las characteristics de choque de un avión en special”. These ports combine their measurements to calculate the local pressure, velocity and direction of air flow.
The researchers will soon evaluate updates of the near field impact detection probe through test flights, in which the probe, mounted on an F-15B, will collect data in pursuit of a second F-15 rocket. The updates of the probe include the placement of pressure transducers – devices that measure air pressure in the cone – only 5 inches from its ports. Los diseños anteriores colocaban esos transduceres a casi 3 meters (12 feet) de distance, lo que retrasaba el tiempo de recordinga y distortaba las mediciones.
The sensitivity to the temperature of the previous designs also presented a challenge, because it provoked fluctuations in precision when the conditions changed. To solve this, the team designed a heating system to maintain the pressure transducers at a constant temperature during the flight.
“La sonda cumplirá los requisites de resolution y precisión de la misión Quesst”, confirms Frederick. “Este proyecto muestra cómo la NASA puede tomar tecnologia existente y adaptarla para solver nuevos desafíos”.