Modern-Aviation

2021 saw significant milestones achieved in the assembly of NASA’s X-59 Quiet SuperSonic Technology aircraft (QueSST), and all eyes now look forward to a pivotal 2022. Following the X-plane’s temporary move from Lockheed Martin’s Skunk Works in California to their facilities in Texas, the X-59 is set to start 2022 with critical ground testing, as progress continues toward NASA’s target of the aircraft’s first flight later this year.

While in Texas, ground testing of the X-59 will be done to ensure the aircraft can withstand the loads and stresses that typically occur during flight. The team will also calibrate and test the fuel systems before the X-59 makes the journey back to California for more tests and completion.

The X-59 is designed to reduce the loudness of the sonic boom, which occurs when an aircraft flies faster than the speed of sound, to a gentle, quiet sonic “thump”. The X-plane will demonstrate this in flights over communities around the U.S. starting in 2024, as NASA collects data that could open the future to commercial supersonic flights over land.

NASA recently flight tested a visual navigation system designed to enhance precise aerial positioning between two aircraft in supersonic flight.

A pair of T-38s flying in formation at supersonic speeds.
This image, captured during 2019’s Air-to-Air Background Oriented Schlieren (AirBOS) flight series, was originally monochromatic and is shown here as a colorized composite image. NASA flew a B-200 outfitted with an updated imaging system at around 30,000 feet while this pair of T-38s were required to not only remain in formation, but to fly at supersonic speeds at the precise moment they were directly beneath the B-200. The images were captured as a result of all three aircraft being in the exact right place at the exact right time, and they are helping NASA prepare for similar imagery of the X-59, using the sun as a necessary background.

The Airborne Location Integrating Geospatial Navigation System (ALIGNS) was developed to prepare for future acoustic validation flights of the X-59 Quiet SuperSonic Technology airplane. The X-59 is designed to reduce the loud sonic boom, heard on the ground when an aircraft flies at supersonic speeds, to a quiet thump – a technology that will be demonstrated when the X-plane flies over communities starting in 2024.

X-59 Concept Art
NASA’s X-59 Quiet SuperSonic Technology aircraft, or QueSST, is designed to fly faster than the speed of sound without producing a loud, disruptive sonic boom, which is typically heard on the ground below aircraft flying at such speeds. Instead, with the X-59, people on the ground will hear nothing more than a quiet sonic thump – if they hear anything at all. The X-59 will fly over communities around the United States to demonstrate this technology, but first, NASA will need to validate the X-plane’s acoustic signature, using a ground recording system.
Credits: NASA / Joey Ponthieux
First, NASA will need to fly the X-59 as part of an acoustic validation phase, to confirm that the aircraft is as quiet as it’s designed to be. This is where ALIGNS comes in.

To validate the X-59’s acoustic signature, the team at NASA’s Armstrong Flight Research Center in Edwards, California will need to both measure and visualize its shock waves, which are waves of pressure produced by aircraft as they fly faster than the speed of sound and are heard as sonic booms. Getting accurate measurements of the X-59’s unique shock waves will require a chase aircraft, flying in exact positions relative to the X-59 while both aircraft fly at supersonic speed.

A shock-sensing probe, mounted to the nose of an F-15, will be the primary tool in measuring the X-59’s shock waves. For the probe to take accurate measurements, the F-15 will need to fly in and out of the X-59’s shock waves at precise distances.

“ALIGNS is software that is designed to create a virtual point on the shock wave that is produced from the target aircraft. The pilots will get directional cues on the ALIGNS display to help them steer the F-15 to that specific point in space,” said ALIGNS Principal Investigator Troy Robillos.

“For our initial flights, we used the ALIGNS tablet to show our pilots where to steer the F-15. ALIGNS shows the horizontal, vertical, fore, and aft offsets in relation to a point on the F-18 shockwave.”

The acoustic validation phase will also include shock wave visualization. Using a technique called schlieren photography, NASA is able to capture imagery of the shock waves from supersonic aircraft – a critical requirement to confirm that the X-59’s shock waves travel through the air as predicted.

The maneuver to capture these images will be challenging. The F-15 chase aircraft, with a special camera system, will need to position itself in a precise location that places the X-59 in frame from a moderate distance, directly in front of the sun, as both aircraft are flying at supersonic speeds.

“ALIGNS is absolutely going to help us get this done,” says NASA test pilot Jim ‘Clue’ Less. “We’ve flight tested it, we’re going to continue to make it better, and we’ll be ready.”

Matt Kamlet
NASA Armstrong Flight Research Center

Last Updated: May 20, 2021
Editor: Lillian Gipson

This image, captured during 2019’s Air-to-Air Background Oriented Schlieren (AirBOS) flight series, was originally monochromatic and is shown here as a colorized composite image. NASA flew a B-200 outfitted with an updated imaging system at around 30,000 feet while this pair of T-38s were required to not only remain in formation, but to fly at supersonic speeds at the precise moment they were directly beneath the B-200. The images were captured as a result of all three aircraft being in the exact right place at the exact right time, and they are helping NASA prepare for similar imagery of the X-59, using the sun as a necessary background.
Credits: NASA