NASA's X-59 QueSST (Quiet Supersonic Technology) Aircraft
NASA's heritage of studying supersonic flight reaches back more than 70 years. That accumulated knowledge, especially as it relates to understanding sonic booms and how to make them quieter, is at the heart of what the mission is about. It's taken years of hard work and the latest in wind-tunnel testing, advanced computer simulation tools, and actual flight testing to reach this point where it's time to prove the theory in the air with a large-scale supersonic X-plane. 1)
NASA's aeronautical innovators are leading a government-industry team to collect data that could make supersonic flight over land possible, dramatically reducing travel time in the United States or anywhere in the world.
The LBFD (Low-Boom Flight Demonstrator) mission has two goals: 1) design and build a piloted, large-scale supersonic X-plane with technology that reduces the loudness of a sonic boom to that of a gentle thump; and 2) fly the X-plane over select U.S. communities to gather data on human responses to the low-boom flights and deliver that data set to U.S. and international regulators.
Using this data, new sound-based rules regarding supersonic flight over land can be written and adopted, which would open the doors to new commercial cargo and passenger markets to provide faster-than-sound air travel.
Elements of NASA's quiet supersonic technology mission are organized within two of the agency's aeronautics programs — the Advanced Air Vehicles Program and the Integrated Aviation Systems Program — and managed by a systems project office whose members span both programs and all four of NASA's aeronautical research field centers: Langley Research Center in Virginia; Glenn Research Center in Cleveland; and Ames Research Center and Armstrong Flight Research Center, which are both located in California.
Phase 1 - 2018-2023: Aircraft Development. NASA anticipates that initial flights to prove performance and safety (also known as "envelope expansion") will take about nine months. At the successful conclusion of these flights, NASA will officially take delivery of the aircraft from Lockheed Martin in early 2023.
Phase 2 - 2023: Acoustic Validation. NASA will fly the X-59 within the supersonic test range over NASA's Armstrong Flight Research Center and Edwards Air Force Base in California to prove the quiet supersonic technology works as designed, aircraft performance is robust in real atmospheric conditions, and the X-59 is safe for operations in the National Airspace System.
Phase 3 - 2024-2026: Community Response Study. The agency will use the X-59 to gather data on how effective the low-boom technology is in terms of public acceptance. This will be done by flying over select U.S. cities beginning in 2024 and asking residents to share their response to the sound the X-59 produces.
Phase 4 - 2027: Final data to regulators. NASA will provide a complete analysis of the community response data to U.S. and international regulators for their use in considering new sound-based rules regarding quiet supersonic flight over land. Such rules could enable new commercial cargo and passenger markets in faster-than-sound air travel. This will be turned over when the mission ends.
Figure 1: This graphic shows the Concept of Operations, or "ConOps", for the Low-Boom Flight Demonstration mission. The mission has three phases. Phases 1 and 2 will be conducted within the R-2508 Complex at Edwards Air Force Base in California, using the facilities and support aircraft depicted here and including overflights of the base community. For Phase 3, the demonstrator will be deployed to communities in other parts of the country to conduct low -boom community response overflight studies (image credit: NASA)
NASA's first purpose-built, supersonic X-plane in decades will soon take to the skies. Final design, construction and assembly of the vehicle is targeted to be complete by 2021. A single pilot is to fly the 96.8-foot-long, 29.5-foot-wide aircraft powered by a single jet engine. Its design research speed will be Mach 1.42, or 940 mph, flying at 55,000 feet.
Figure 2: LBFD overview: This "four-view" of the X-59 Quiet SuperSonic Technology demonstrator provides specifications of the piloted vehicle that is being built by Lockheed Martin Skunk Works. The X-59 is an experimental aircraft only; it is not a prototype design for a commercial airliner and will never carry passengers. Its unique shape and set of technologies reduce the loudness of a sonic boom reaching the ground to that of a gentle thump. Starting in 2024, it will be flown above select U.S. communities to collect data from residents responding to the X-59's sonic thump (image credit: NASA)
Members of the Low-Boom Flight Demonstration mission, which includes managing construction of the X-59 Quiet SuperSonic Technology aircraft and the flights to collect community response data, are located at all four NASA aeronautical research field centers:
• Ames Research Center: X-59 configuration, systems engineering
• Armstrong Flight Research Center: airworthiness of X-59, safety and mission assurance, flight/ground operations, flight systems, systems engineering, project management, community response testing
• Glenn Research Center: X-59 configuration, propulsion performance
• Langley Research Center: systems engineering, configuration assessment, research data, flight systems, project management, community response testing.
Figure 3: Teams at NASA's Glenn Research Center in Ohio (top left), Langley's Research Center in Virginia (bottom left), Armstrong Flight Research Center (top right) and Ames Research Center (bottom right) in California play key roles in developing and evaluating the X-59 Quiet SuperSonic Technology aircraft. NASA hopes to enable a new commercial market of supersonic aircraft that can fly over land (image credit: NASA)
Once built and delivered to NASA in 2021, the new X-plane will spend the next three years making a series of flights, initially to prove the quiet supersonic technology works as expected, and then to fly over several U.S. cities to measure public reaction, if any, to the hushed sonic thumps rippling over the population on the ground. Meanwhile, flight tests using other NASA aircraft will continue to provide researchers with more data about sonic booms and quiet supersonic technology.
• June 15, 2021: Mountains of data will be required if NASA's X-59 Quiet SuperSonic Technology (X-59QueSST) airplane is going to help change the future of commercial supersonic flight over land, and a sophisticated suite of instruments is needed in the air and on the ground to collect it. 2)
- On the aircraft, these instruments are known as the air data system. A computer takes input from probes, sensors, and other devices and feeds that information – like altitude, airspeed, air pressure, and temperature – to the pilot and flight control computer to ensure safe and accurate flying.
- In an effort to perfect the X-59's air data system, engineers from across the agency visited the 8- by 6-foot Supersonic Wind Tunnel at NASA's Glenn Research in Cleveland. There, they evaluated the air data probe, which is installed at the tip of the aircraft's nose and is used to measure key flight parameters, as well as the aircraft's attitude while flying.
- "As the aircraft flies, it is critical that we have the most accurate flight data available for safety and the supersonic research mission," said Jeff Flamm, the X-59 lead aerodynamics engineer at NASA's Langley Research Center. "Wind tunnels give us a controlled environment to precisely calibrate the aircraft's probes and sensors, and the data we collect at Glenn will inform the decisions we make to set us up for success during our initial flights."
- While in the tunnel, the probe was subjected to various flight conditions, including runs at takeoff, transonic, and supersonic speeds, to fine tune and verify successful hardware and software operation. The wind tunnel data will be used during initial flight testing, while the team uses the real flight data from the early flights to further calibrate the air data system to adjust for any conditions not presented during testing.
- "We are able to simulate specific flight conditions and speeds in our wind tunnel, which has made it a destination for the X-59 team," said David Friedlander, research engineer at NASA Glenn. "An aircraft like the X-59 will cover a multitude of flight scenarios and different ambient environments, so the tunnel data we produce is critical to its success."
- The air data probe is now on its way to Lockheed Martin Skunk Works to be installed on the X-59. NASA is planning to start its test flight series in 2022.
- The X-59 team will return to the tunnel at NASA Glenn later this year to complete a sonic boom test. Using a small model – measuring about a foot and a half in length – this test will produce pressure, or "shock wave," data to compare with computer modeling and better predict actual sonic booms and sonic thumps during flights. After leaving Glenn, the team will travel to Japan for additional testing with JAXA. The outcome of both tests will validate the unique airframe design technologies NASA believes will allow future supersonic planes to fly quietly.
- Once the X-59's airworthiness has been proven in wind tunnel and flight testing, NASA will begin community overflights in 2024 to gauge the public's perception of the sonic thump. Data from these flights will be presented to regulators in the U.S. and abroad with the potential to lift the ban on commercial supersonic flight over land.
Figure 4: NASA engineer Courtney Winski inspects the X-59's air data probe at NASA's Glenn 8- by- 6-foot Supersonic Wind Tunnel (image credit: NASA)
Figure 5: The X-59 QueSST's air data probe is mounted inside the 8- by- 6-foot Supersonic Wind Tunnel at NASA's Glenn Research Center (image credit: NASA)
• May 7, 2021: NASA has awarded a contract to Harris Miller Miller & Hanson Inc. of Burlington, Massachusetts, to support a national campaign of community overflight tests using the agency's X-59 Quiet SuperSonic Technology research aircraft. 3)
- This cost-plus-fixed-fee, indefinite-delivery/indefinite-quantity contract has a maximum potential value of approximately $29 million with an eight-year period of performance.
- Significant subcontractors include:
a) Westat Inc. of Rockville, Maryland
b) Blue Ridge Research and Consulting LLC of Asheville, North Carolina
c) EMS Brüel & Kjær Inc. of Folsom, California.
- NASA is designing and building the X-59 research aircraft – a piloted, single-seat supersonic X-plane – with technology that reduces the loudness of a sonic boom to that of a gentle thump. NASA's aeronautical innovators are leading a team across government and industry to collect data that could allow supersonic flight over land, dramatically reducing travel time within the United States or to anywhere in the world.
- The scope of the work under this contract includes supporting NASA in the planning, execution, and documentation of phase three of the agency's Low-Boom Flight Demonstration mission.
- NASA currently is working with Lockheed Martin Skunk Works of Palmdale, California, to design, build and conduct initial flight testing of the X-59 research aircraft as part of phase one of the mission. The team will work during phase two to prove the X-59 performs as designed and is safe to fly in the national airspace. During phase three, NASA will fly the X-59 aircraft over communities yet to be selected and ask residents to share their response to the sound the aircraft generates during supersonic flight.
- NASA will provide the results of the community survey and the X-59 acoustic data collected during the community overflight tests to U.S. and international regulators for use in considering new sound-based rules to enable supersonic flight over land.
Figure 6: This composite image, which includes an illustration of NASA's X-59 research aircraft, shows the airplane's final configuration following years of research and design engineering. The single-pilot aircraft is now under construction at Lockheed Martin's Skunk Works facility in Palmdale, California (image credit: Lockheed Martin)
• March 22, 2021: For the deserts of Southern California, the major milestones of aviation have long been marked by the unique sights, and sounds, of flight. 4)
Figure 7: NASA's X-59 QueSST (Quiet SuperSonic Technology) aircraft 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 (image credit: NASA / Joey Ponthieux)
- From the late Chuck Yeager's breaking of the sound barrier in 1947, to the space shuttles' approach and landing at NASA's Armstrong Flight Research Center (then Dryden) in Edwards, and through today, one recognizable sound is the sonic boom – a loud, sometimes startling event that we hear on the ground when an aircraft overhead flies faster than the speed of sound, also called supersonic speed.
- NASA, for decades, has led the effort to study sonic booms, the loudness of which are considered the key barrier to enabling a future for overland, commercial supersonic aircraft. That future will be closer to reality when the agency's X-59 Quiet SuperSonic Technology (QueSST) airplane takes to those familiar skies in 2022, taking the first steps to demonstrating the ability to fly at supersonic speeds while reducing the sonic boom to a significantly quieter sonic thump.
Figure 8: As part of the CarpetDIEM (Carpet Determination in Entirety Measurements) flight series, NASA will test the CI-GRS, using traditional sonic booms from an F/A-18 in supersonic flight. These tests will provide lessons learned as NASA prepares to capture the X-59's quiet sonic thumps during the acoustic validation and community overflight phases of its mission (image credit: NASA Photo / Lauren Hughes)
- While NASA will fly the X-59 over communities around the U.S. as early as 2024 to analyze the public's perception and acceptability of quiet supersonic flight, the agency will first need to prove that the X-plane is as quiet as it's designed to be.
- To do this, NASA will measure the sound of the sonic thumps in the Mojave Desert using cutting edge technology – a brand new, state-of-the-art ground recording system for a brand new, state-of-the-art X-plane.
- NASA has contracted Crystal Instruments of Santa Clara, California to deliver a high-fidelity sonic boom – and soon to be, a quiet sonic thump – recording system, capable of providing the data necessary for the agency to validate the acoustic signature of the X-59.
- "This will be the first time that we have a single system across NASA to do this research, and it will incorporate a lot of newer technologies to allow us to get this done," said Larry Cliatt, NASA's tech lead for the acoustic validation phase of the NASA's Low-Boom Flight Demonstration mission. "I consider it the next generation of sonic boom, and soon to be quieter sonic thump, recording systems."
- NASA will utilize the CI-GRS (Crystal Instruments Ground Recording System) to gather time, waveform, and spectral data related to sonic booms and sonic thumps. The CI-GRS will also feature the ability for NASA to install custom software and algorithms to perform various specialized operations for real-time sonic thump analysis.
Figure 9: NASA will use the CI-GRS to gather data related to sonic booms, and in the future, the X-59's quiet sonic thumps. A feature of the CI-GRS will be the ability for NASA to install custom software and algorithms tailored to various specialized operations for real-time analysis of sonic thumps (image credit: Crystal Instruments)
- With this technology, NASA will have the ability to extract, review, and analyze specific data from a recording. For example, the CI-GRS will have the capability to accommodate software that can distinguish a low-amplitude sonic thump from the X-59 among other ambient sounds. That software will also be able to calculate a number of different types of acoustic metrics, including perceived sound level, which is the currently accepted measure for sonic boom loudness.
- "What we are building is a data acquisition system that will use the latest advancements in technology, with cutting edge hardware and software capabilities, so that NASA can capture the high-quality sonic boom data they need," said Darren Fraser, Crystal Instruments vice president of sales.
- The first deliveries of the CI-GRS are expected to be deployed for initial field testing at NASA Armstrong, and later, some will deploy outside Edwards Air Force Base with units spread out as a 30-nautical-mile-long ground microphone array. This will be part of the next rounds of the CarpetDIEM.
- These flights will simulate the acoustic validation phase for the X-59 by deploying an aircraft from NASA Armstrong, which will fly over the array at supersonic speeds, testing the units' ability to record sonic boom data, before they capture the X-59's quiet sonic thumps.
- The lessons learned from the CarpetDIEM tests will facilitate any necessary updates and modifications for the final CI-GRS design, which will then be used in the same method for the X-59 with as many as 70 ground recording stations.
- Another requirement NASA will need the CI-GRS to meet will be its ability to operate remotely. In previous, similar supersonic acoustic research efforts, NASA deployed sonic boom recorders in the field, and collected the sensors at the end of each test day. A 30-mile-long microphone array in the Mojave Desert, however, presents a logistical challenge.
- "This ground recording system will be more robust and ruggedized when it comes to its operational use, and that's what we anticipate, with the ability to deploy for several days at a time," said Cliatt. "These will also incorporate two-way communications so that they can be deployed over a large area when the X-59 flies over communities starting in 2024, so the ultimate total of 175 of these can be controlled from a single remote host."
- The next CarpetDIEM flights are expected for late 2021.
- "The CI-GRS is going to be a first of its kind, much like the X-59, and I think there will be a lot of firsts in a new age of potential commercial supersonic travel," said Fraser. "We think this will set the stage for the future, and I think that's what everybody wants to look toward."
• December 16, 2019: NASA's first large scale, piloted X-plane in more than three decades is cleared for final assembly and integration of its systems following a major project review by senior managers held Thursday at NASA Headquarters in Washington. 5)
The management review, known as Key Decision Point-D (KDP-D), was the last programmatic hurdle for the X-59 Quiet SuperSonic Technology (QueSST) aircraft to clear before officials meet again in late 2020 to approve the airplane's first flight in 2021.
Figure 10: Illustration of the completed X-59 QueSST landing on a runway (image credit: Lockheed Martin)
"With the completion of KDP-D we've shown the project is on schedule, it's well planned and on track. We have everything in place to continue this historic research mission for the nation's air-traveling public," said Bob Pearce, NASA's associate administrator for Aeronautics.
The X-59 is shaped to reduce the loudness of a sonic boom reaching the ground to that of a gentle thump, if it is heard at all. It will be flown above select U.S. communities to generate data from sensors and people on the ground in order to gauge public perception. That data will help regulators establish new rules to enable commercial supersonic air travel over land.
Three major work areas are actively set up for building the airplane's main fuselage, wing and empennage. Final assembly and integration of the airplane's systems – including an innovative cockpit eXternal Visibility System – is targeted for late 2020.
1) "Low-Boom Flight Demonstration," NASA, 26 April 2018, URL: https://www.nasa.gov/mission_pages/lowboom/science
2) Jimi Russell, "A Probing Question: How Do You Fly the X-59 Accurately?," NASA Feature, 15 June 2021, URL: https://www.nasa.gov/feature/glenn/2021/NASA-fine-tunes-air-data-system-on-supersonic-X-plane
3) J. D. Harrington, Sasha Ellis, "NASA Selects Contractor for Quiet Supersonic Flight Community Testing," NASA Press Release 21-057, 07 May 2021, URL: https://www.nasa.gov/press-release/nasa-selects-contractor-for-quiet-supersonic-flight-community-testing
4) Matt Kamlet, "Cutting Edge Ground Recorders to Measure Acoustics of NASA X-59 Quiet Supersonic Flights," SciTechDaily, 22 March 2021, URL: https://scitechdaily.com/cutting-edge-ground-recorders-to-measure-acoustics-of-nasa-x-59-quiet-supersonic-flights/
5) J. D. Harrington, "NASA's X-59 Quiet Supersonic Research Aircraft Cleared for Final Assembly," NASA Press Release 19-098, 16 December 2019, URL: https://www.nasa.gov/press-release/nasa-s-x-59-quiet-supersonic-research-aircraft-cleared-for-final-assembly
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).