NASA announced that Lockheed Martin’s X-59 Quiet Supersonic Technology (X-59 QueSST) experimental aircraft reached a critical development milestone with its first engine run at Lockheed Martin’s Skunk Works facility in Palmdale, California. This milestone marks the beginning of engine-run tests, which commenced on October 30, 2024, allowing the X-59 team to confirm that the aircraft’s systems function effectively when powered by its own engine.
During earlier stages, the team used external power sources to conduct preliminary tests. These tests are integral to NASA’s X-59 QueSST mission, aimed at reducing the noise impact of supersonic flight over land, potentially informing future regulations for commercial supersonic travel as well as leading to improvements in stealth aircraft.
Engine-run tests are being conducted in phases. In the initial phase, the X-59’s engine was rotated at a low speed without ignition to detect any leaks and confirm that systems were synchronized and operating correctly. Subsequently, the team fueled the aircraft and conducted low-power engine tests, ensuring that the engine, along with hydraulic, electrical, and environmental control systems, operated without malfunctions or leaks when powered directly by the engine. Jay Brandon, NASA’s X-59 chief engineer, described this stage as preliminary verification to ensure that all systems were operational before advancing to full-engine operation.
Designed to mitigate sonic booms, the X-59 is intended to produce a quieter sonic effect, which NASA describes as a “thump,” even at supersonic speeds. This feature is central to the X-59 QueSST mission’s goal of assessing the public perception of reduced noise, with data that could eventually help regulators review current restrictions on supersonic flight over land.
The X-59’s engine, a modified F414-GE-100, generates 98 kN of thrust and is positioned atop the aircraft to reduce noise impact. This design enables the X-59 to reach Mach 1.4, or roughly 1,488 kilometers per hour, at an altitude of approximately 16,764 meters. The engine’s placement and thrust facilitate meeting mission objectives by enabling supersonic flight with reduced noise impact at ground level.
These tests are part of a series of ground evaluations required for the aircraft’s safe progression toward flight. Following initial engine tests, the team will proceed with more rigorous evaluations, including high-power tests, rapid throttle changes, and flight condition simulations. This phase will lead to aluminum bird testing, during which the aircraft’s systems are monitored under various operating scenarios, including normal and failure conditions. The team will conduct taxi tests, during which the X-59 will move on the ground to verify its handling capabilities.
The X-59, measuring approximately 30.4 meters in length with a wingspan of 9 meters, has been in development since NASA awarded Lockheed Martin a preliminary design contract in 2016. Although initially projected to begin flight tests in 2021, the schedule has been adjusted, with the first flight now expected in early 2025. The X-59’s design includes an enhanced flight vision system (EVS) with an external vision system (XVS) that provides a forward view to compensate for the limited visibility due to the aircraft’s extended nose. Supplied by Collins Aerospace, this visibility technology integrates multispectral imaging systems to enhance situational awareness, particularly during landing.
With a target cruising speed of Mach 1.42 (around 1,510 kilometers per hour), the X-59 aims to reach a ground noise level of 75 effective perceived noise decibels (EPNdB), comparable to the sound of a car door closing. This would be significantly quieter than the Concorde’s supersonic boom, estimated between 105 and 110 EPNdB. By using a long, narrow airframe and a top-mounted engine intake, the X-59’s design is intended to reduce the intensity of the sonic boom experienced on the ground. In addition to its primary noise reduction features, the aircraft is equipped with components such as a cockpit, canopy, and ejection seat from a Northrop T-38, and landing gear from an F-16.
The X-59 QueSST mission’s testing phase will include community evaluations across U.S. cities from 2023 to 2025. These tests will collect feedback on noise perception from residents, contributing data that will be submitted to the International Civil Aviation Organization (ICAO) and the Federal Aviation Administration (FAA) by 2027. These findings could inform regulatory discussions regarding commercial supersonic flight over land, potentially opening new supersonic travel routes by 2028.
The X-59 development has comprised multiple stages, including wind tunnel testing, structural assembly, and system integration conducted over recent years. With its 98 kN of thrust, the aircraft is projected to reach a maximum speed of Mach 1.5 or 1,593 kilometers per hour, with a cruise speed of Mach 1.42 or 1,510 kilometers per hour at 16,764 meters. Further evaluations will proceed as NASA continues toward the planned first flight, currently targeted for early 2025.
Curiously, the engine-run tests of the X-59 are taking place at Lockheed Martin’s Skunk Works facility in Palmdale, California, a site also linked to the development of another high-profile and highly classified project: the SR-72 hypersonic aircraft. The X-59, which seeks to achieve quieter supersonic flight, involves advanced noise-reduction technologies, a modified engine configuration, and complex system integrations—features that are also pertinent to hypersonic and high-speed aircraft design. As the SR-72 aims to reach speeds of up to Mach 6, insights into high-speed aerodynamics, minimizing ground-level impact, and integrating advanced propulsion systems will be crucial. Observations from the X-59’s testing could support approaches to challenges anticipated in the SR-72 program, such as maintaining structural integrity at high speeds and managing the thermal and acoustic effects associated with hypersonic flight. The X-59’s tests, therefore, may contribute valuable data and engineering insights for the SR-72’s development trajectory.