NASA’s quest to reshape the landscape for supersonic aircraft remains on track as assembly progresses on the X-59 Quiet SuperSonic Technology (QueSST) demonstrator. Developed by Lockheed Martin under contract with NASA, the partners will use the X-plane to test public perception of a sonic “thud” that new supersonic designs create.
In recent months Lockheed Martin had begun to build the wing and flight deck sections of the X-59 QueSST at its Skunk Works factory in Palmdale, California, and program officials say the aircraft is on schedule to fly toward the end of 2021.
“The aircraft is looking like the X-59,” said Peter Iosifidis, who recently retired as Lockheed Martin’s program manager for X-59 QueSST, at the American Institute of Aeronautics and Astronautics (AIAA) Aviation Forum in June. The forward fuselage and empennage were “coming together,” he said, adding that all the structure was completely installed on the wings, including some of the skins.
“We’re very far along with the aircraft,” Iosifidis said. “Everything has gone pretty much as we had planned—nothing has happened thus far on this effort that has jeopardized any of our critical milestones.”
Once complete, the X-59 will measure 96 feet long, have a span of 29.5 feet, reach speeds of Mach 1.4, and fly at an altitude of 55,000 feet. A key design requirement of the X-59 is to replicate the noise effects of larger supersonic aircraft so that it can be used to conduct a series of trials over communities in the U.S. to assess the public’s sense of noise.
But unlike the Concorde, the X-59 will not emit what is commonly known as a sonic boom. Instead, the partners hope to demonstrate that new designs and technologies will result in a softer, quieter sonic “thud,” or low boom, that might prove more acceptable to the public and pave the way for supersonic flight over land.
The effort is “all about” the ban on supersonic flight over land, Iosifidis said. “All of us are flying commercially slower today than we were decades ago,” he said. “Across the globe...technology has moved forward and faster, but we seem to have gone backward.”
“The idea is a future where simple supersonic flight contributes to the transformation and the decrease in the time required to travel to distant places around the globe,” added Peter Coen, the low boom flight demonstration mission manager for NASA’s Aeronautics Research Mission Directorate.
NASA’s vision is to research possibilities to make supersonic available to all segments, Coen said. But such travel suffers a perception issue. “We hear often that supersonic aircraft…being described as the son of the Concorde. That fuels a misconception on some people’s part that future aircraft will be like the Concorde.”
While like the Concorde, future supersonic aircraft will represent “amazing technological achievements,” Coen added. “They will be very unlike the Concorde in their impact on the environment and their impact on the communities in which they operate.”
The developers envision supersonic travel that is not only fast, he said, “but available to a broad spectrum of people and that is also efficient, affordable, and environmentally responsible.” However, to get there, the aviation community must overcome public perception barriers.
If successful, the X-59 would prove that low boom does exist and at levels that will be acceptable to the general public, Iosifidis said.
“We’ve been working on this type of technology—low-boom technology—for decades now,” he said, noting the “aha moment” came in 2011 when a joint effort with NASA demonstrated the feasibility of design methods to move forward with an aircraft that could meet the necessary noise requirements. “We found results of [wind-tunnel tests] were in lockstep with predictions we had made for that design,” Iosifidis said. “Having that knowledge and our confidence in those design methods is what really started the wheels of full-scale effort to go build what ultimately is known as X-59 now.”
X-59's Aggressive Schedule
NASA awarded the contract in April of 2018 and Lockheed Martin has worked on a “very aggressive schedule” since then, said Iosifidis. A lot of factors have played into the ability to keep a quick turn-time from contract to first flight in 2021.
They include taking unusual approaches to the manufacturing of a one-off vehicle. Lockheed Martin began cutting metal on its first parts by November 2018 and loaded the first parts into the jig by June 2019. But the company has been doing concurrent engineering and manufacturing, Iosifidis said. “You have to start building a lot of your parts before the final design is complete," he explained. "Otherwise, the program could take an additional few years to bring it to completion. That is really not the kind of program NASA wanted. That increases cost.”
In addition, Lockheed Martin has applied technologies typically used in large-scale manufacturing efforts, such as the use of robots capable of drilling thousands of holes rapidly, to gain cost and schedule benefits. The robots are “not typically used on one-off aircraft,” he added.
In an effort to further help with the timeline, NASA established the requirements early on for the X-59 and has “remained steadfast on those requirements," Iosifidis added. "We have not had a lot of changes and certainly no major change in requirements for the aircraft since the actual beginning of X-59.”
Substantial high- and low-speed wind tunnel testing, conducted in advance, also kept the program on schedule. “All these tests validated the fact that the design was sound and the aircraft was safe and it was going to achieve all the performance requirements that were established for the program,” Iosifidis. “It reduces risk as you move forward through the design and the manufacturing cycle of the aircraft.”
Work has continued despite the complexities involved with operating during the Covid-19 pandemic, he added. Although Lockheed Martin has encountered some delays, particularly in some parts delivery, none have affected any of the critical milestones, he said. “Every delay we’ve been able to accommodate by shifting work around.”
Once the airplane takes to the air, it will undergo a series of flight tests to expand the envelope. Those tests will take place initially out of the Palmdale facility and then at NASA’s Armstrong Flight Research Center at Edwards Air Force Base in California, Coen said. Once the aircraft has demonstrated it has met the performance characteristics, it will undergo tests for acoustics to ensure the noise signals are as expected in various atmospheric conditions. This is important for the validity of the planned community trials, he said.
The partners expect those tests to last between 15 to 18 months. Plans call for initial noise trials to begin near Armstrong by late 2022 or early 2023, before the vehicle flies trials over different communities throughout the U.S. The trials will involve general public surveys to measure response to sound exposure. NASA has staged a “dry run” in Galveston, Texas, using an F-18 jet to test its survey and data collection methods.
The goal is to complete the trials before the end of Fiscal Year 2026, in time to have data prepared for delivery to the International Civil Aviation Organization (ICAO) by early 2027, Coen said. The partners hope ICAO would be ready for offering a proposal on supersonic flight by early 2028.
The effort fits with the central role that national research agencies and policy agencies play in developing new markets, he said, “providing fundamental data—scientifically validated fundamental data that can underlie the development of new rules and new standards that enable innovation in the market but also protect the public both traveling and on the ground.”
That’s why NASA chose the X-plane approach, he said. “[Validation] could only be achieved through flight," noted Coen. "By using an X-plane, we can focus our efforts on defining a minimum set of requirements so we can achieve our goals in a cost-effective, timely fashion.”