Veritastech Pilot Academy

How NASA Is Using F-15s to Unlock Supersonic Flight

A pair of retired U.S. Air Force F-15 Eagles could be instrumental in the effort to lift the FAA’s nearly 53-year ban on supersonic flight over land.

The F-15s are slated to partake in groundbreaking research at NASA’s Armstrong Flight Research Center in California, where the experimental X-59—codeveloped by NASA and Lockheed Martin—landed in October following its debut test flight. They will support the X-59, which is designed to reduce the noise of sonic booms to quieter “sonic thumps,” as it continues testing over the deserts of California this year.

“The priority is for them to successfully support the X-59 through completion of that mission,” said Troy Asher, director of flight operations at Armstrong. “And over the longer term, these aircraft will help position NASA to continue supporting advanced aeronautics research and partnerships.”

The F-15s arrived at Armstrong from the Oregon Air National Guard’s 173rd Fighter Wing at Kingsley Field on December 22 after completing their final military flights. One will continue flying as a NASA research aircraft. The other will be used for parts to sustain the program.

NASA deploys chase planes to accompany X-59 flights, using them to monitor weather conditions, collect imagery, and help the aircraft communicate with air traffic control (ATC). They typically fly about 500 to 1,000 feet apart. But during the X-59’s maiden voyage, chase pilot Jim “Clue” Less flew within one wingspan to compare airspeed and altitude indicators.

The space agency has flown F-15s for a variety of purposes since the early 1970s. The model’s high speed—approaching Mach 2.5—makes it ideal for keeping pace with the X-59, which is expected to cruise at about Mach 1.4, or 925 mph. NASA previously modified a pair of F-15s with life support systems so that pilots could fly them as high as 60,000 feet, just above the supersonic test plane’s 55,000-foot cruise altitude. The two new additions will get the same modifications, it said.

F-15 Eagle fighter jet arrives at NASA Armstrong in California
Oregon Air National Guard ground crews welcome an F-15 Eagle to NASA’s Armstrong Flight Research Center in California on December 22. [Credit: NASA/Christopher LC Clark]

The F-15s are also capable of carrying external hardware beneath their wings or slung below the fuselage, such as instrumentation that will later be installed to measure the X-59’s shock waves.

“These two aircraft will enable successful data collection and chase plane capabilities for the X-59,” said Asher.

NASA also chases the aircraft with F/A-18 Super Hornets, which are more agile at lower speeds than the F-15s. One of them has a two-seat cockpit and wide field of view that is preferred for collecting imagery.

“The choice for which chase aircraft we will use for any given X-59 test flight could go either way depending on other mission needs and if any scheduled maintenance requires the airplane to be grounded for a while,” Less said in a blog post on Tuesday.

NASA’s Supersonic QUESST

The X-59 is the centerpiece of NASA’s Quiet SuperSonic Technology, or QUESST, program—a mission to demonstrate supersonic flight over land while generating about the same amount of noise as a car door shutting in the distance.

The FAA since 1973 has limited these operations to noncommercial aircraft. But there is a growing push by supersonic aircraft developers, lawmakers, and even President Donald Trump to reverse the ban.

“Basically, [the rule] says ‘thou shalt not exceed Mach 1. And what it should say is, ‘thou shalt not make loud noises,’” Blake Scholl, CEO of Boom Supersonic, told FLYING in February following the debut test flight of the company’s XB-1 demonstrator, an early version of its planned 60-80-seat Overture.

On subsequent tests, the company achieved what it dubbed “boomless cruise,” using microphones on the ground to confirm the XB-1’s low noise signature. NASA has similar plans for QUESST.

The X-59’s most striking feature is its Pinocchio-like nose, which stretches about one-third of the aircraft’s 100-foot length. It is designed to break up shock waves in front of the aircraft. A top-mounted F414-GE-100 engine, meanwhile, gives it a smooth underside and redirects airflows upward.

Because pilots’ views are obstructed by the long nose, the X-59’s cockpit, located in the middle of the fuselage, lacks forward-facing windows. Replacing them is an eXternal Vision System comprising cameras and high-definition displays that let the pilot see ahead and below the aircraft.

In addition to the F414 engine, which comes from the F/A-18, other flight-proven components include life support systems from the F-15; landing gear from the F-16 Fighting Falcon; control stick from the F-117 Nighthawk; and cockpit canopy from the T-38 Talon.

The aircraft’s maiden sortie in October lasted about 67 minutes, taking off from Lockheed’s Skunk Works facility in Palmdale, California, and landing about 30 miles away at Armstrong. It reached about 230 mph and 12,000 feet, well short of its intended specifications. But subsequent tests will validate airworthiness and expand the envelope.

In the coming months, NASA will fly the X-59 over the California desert to gauge its handling and ability to break up shock waves. It will aim to achieve target speed and altitude during this phase. NASA would then conduct further testing at the supersonic test range at Edwards Air Force Base (KEDW) before moving to the ultimate test—community survey flights.

Researchers will fly the X-59 over densely populated areas, gauging the population’s perception of noise using ground measurements and surveys. The data collected will be shared with the FAA and other regulators to help inform new standards for commercial supersonic flight over land.

Commercial developers could also look to re-create aspects of the X-59 if it proves successful. Some, such as Exosonic and Aerion, have gone under before their concepts came to fruition. But others such as Boom and Spike Aerospace, which is developing the S-512 supersonic business jet, are still angling to field a successor to Concorde.

Scroll to Top