NASA X-59 Supersonic Research Aircraft Begins Taxi Tests

NASA and Lockheed Martin have begun initial taxi tests of the X-59 Quesst quiet supersonic research aircraft, marking another step toward its long-anticipated first flight.

The aircraft moved under its own engine power for the first time on July 10 at Lockheed Martin’s Palmdale, California, facility and conducted a series of low-speed taxi tests, says Brian Griffin, NASA’s X-59 project lead flight test engineer.

“It started with a very slow ramp taxi, just for basic ground handling characteristics of the airplane, and then that proceeded on to a low-speed taxi event, which was on the runway itself, and that was done at 25 kts ground speed,” Griffin says. NASA X-59 lead pilot Nils Larson was in the cockpit for the tests which over the next few weeks will gradually build up to medium speed taxi and high-speed taxi tests. “We’re targeting 50 kts and 75 kts, and then finally, 100 kts ground speed before we finish our initial round of taxi testing, before we proceed into first flight,” Griffin says.

Taxi testing follows the completion of an exhaustive round of ground tests which began in earnest after the X-59 was rolled out in January 2024. Although NASA originally hoped to start flight tests in 2024, these plans were later pushed back to this year after several technical challenges linked to the flight control computer, hydraulic system and other components.

Due to the unconventional configuration of the 99.7 ft.-long X-59, NASA and Lockheed plan to conduct taxi tests with extreme caution. This is partly due to the extreme aft positioning of the aircraft’s short landing gear wheelbase and small 29.7 ft.-span delta wing. Due to these and other factors, the X-59 is expected to rotate at a shallow angle at around 150 kts and lift off at a high speed of around 170 kts.

Test pilots therefore aim to keep maximum taxi speeds well below rotation speed to prevent the aircraft flight control laws from inadvertently transitioning from ground-based to flight-based control algorithms. Plans including taxiing just fast enough to evaluate flight control system loop closures. Taxi tests will also include evaluation of the flutter excitation system which will provide a dynamic force input to stimulate structural vibration modes.

“As we proceed into higher speed taxi testing, some of the objectives will involve evaluating the performance of the air data system, as well the excitation system that can effectively move control surfaces automatically,” Griffin says. “We’re going to be doing that as we proceed into the higher speeds to collect additional data on how that system operates and also characterize some of the aerodynamic effects of those control surfaces as we get to high enough speeds,” he adds.

To compensate for the long nose of the aircraft which obscures the pilot’s forward view, the X-59 is configured with a multi-camera based external vision system. “The vision system is required because there is no traditional windscreen and canopy for the pilot to see out the front. So, those things are being investigated heavily during this initial round of taxi testing, not just the performance of the aircraft systems in terms of the landing gear, engine and brakes and so on, but also the vision systems and what implications that has as to the safe operation of the aircraft,” Griffin says.

The start of taxi tests follows the completion of “aluminum bird” testing, in which data was fed to the aircraft under both normal and failure conditions. These were preceded earlier this year by a series of key engine and electromagnetic interference (EMI) checks which were divided into six main stages—or “decks”—to verify engine and systems performance. Decks one through three were focused on performance validation of the X-59’s single GE Aerospace F414 engine, while decks four through six checked EMI and the electromagnetic compatibility of systems.

The X-59 is designed to gather data on the public response to shaped low sonic booms by conducting supersonic test flights over U.S. cities. The data collected is planned to be provided to the FAA and the International Civil Aviation Organization (ICAO) to enable development of a noise certification standard for sonic booms that will enable the prohibition on civil supersonic flight over land to be lifted.

Although NASA originally planned to provide the data to ICAO in time for the 2028 meeting of its Committee on Aviation Environmental Protection (CAEP), which planned to decide on the boom standard, delays to the start of flight tests have pushed this target back to the CAEP/15 meeting in 2030.

NASA says the low boom mission of the X-59 remains highly relevant despite President Trump’s executive order in June directing the FAA to lift the longstanding ban on overland supersonic flight.