How can NASA’s X-59 fly faster than sound without a boom?

In three steps. The boom is not one event at the moment a jet passes Mach 1; it is the shock pattern the jet drags along the whole time it flies faster than sound.

1. Shocks

   A jet faster than sound can’t warn the air ahead. Each place where it pushes air aside, the nose, canopy, inlet, wings and tail, starts its own shock wave, and all of them trail behind it in a cone.

2. Catch up

   The stronger part of a pressure wave travels a little faster than the weaker part. Over the 17 km from 55,000 feet down to the ground, the shocks at the front overtake each other and merge, and so do the ones at the back.

3. Two jumps

   What reaches the ground is an N-wave: a sudden jump in pressure, a steady fall below normal, and a sudden jump back. You hear the two jumps as a sharp double boom.

Sonic Boom Lab shows the first step: how the sound rings of a speeding jet pile into a cone that sweeps the ground. Quiet Boom Lab picks up from there and follows the shocks on their way down.

A sonic boom is a pressure change, measured in pounds per square foot (psf). In the tool’s model, an ordinary jet the size of the X-59 at Mach 1.4 and 55,000 feet reaches the ground as an N-wave of about 0.8 psf. That is a tiny change, less than a thousandth of the air’s own pressure, but it comes in about a millisecond, and a sudden jump is what the ear hears as a bang.

So loudness depends on how fast the pressure rises, not just how far. NASA rates booms in perceived decibels (PLdB), a scale built for short, sharp sounds. Concorde’s boom was about 105 PLdB, NASA says. Its target for the X-59 is about 75 PLdB, which it has compared to a car door closing. In the model, the X-59 shape’s pressure builds in five small steps over about 15 milliseconds instead of one: a thump, not a bang.

The X-59 is 99.7 feet long, and almost a third of that is nose. A long, slender nose spreads the front of the pressure wave over many meters, so it starts as a ramp of small compressions instead of one strong shock. The single engine sits on top of the jet, which, NASA says, directs its noise away from people below, and the underside is kept smooth. Lift, which also pushes air down, is spread along the jet from the small canard to the T-tail instead of piling up in one place.

The result is a jet whose shocks start weaker and farther apart, too far apart to catch up before they reach the ground. Designers worked backwards: they picked the gentle signature they wanted on the ground and shaped the aircraft to make it. The long nose has a cost. It blocks the view ahead, so the pilot looks forward through a camera and screen instead of a windshield.

NASA and Lockheed Martin Skunk Works built the X-59 for NASA’s Quesst mission. It first flew on October 28, 2025, went supersonic in June 2026 and reached Mach 1.53, about 1,010 mph, during a record six flights in one week in September 2026, NASA says. A year after its first flight, after more than 40 flights, it flew across the country via El Paso and Fort Worth to Kennedy Space Center.

Next come acoustic tests, measuring the thump the jet actually makes, and then flights over US communities to ask people what they hear. That matters because civil supersonic flight over US land has been banned since 1973, after public complaints about booms. In July 2026 the FAA proposed replacing the ban with a limit of 0.11 psf on a boom’s pressure at the ground. The rule is not final, and Quesst’s data is meant to help regulators decide what people will accept.

1. 1 See

   Open Quiet Boom Lab and tap Ordinary jet, same speed. The shock lines merge into two before the ground. Biggest pressure jump reads 0.79 psf, Rise time 1.3 ms and Loudness (model) 92 PLdB.

2. 2 Change

   Drag the jet’s nose, or the Nose slider, all the way out, or tap X-59 design point: Mach 1.4, 55,000 ft. Five small shocks reach the ground. The biggest jump falls to 0.074 psf, the rise time grows to 15 ms, and the loudness reads 75 PLdB.

3. 3 Understand

   Keep the X-59 shape and drag Speed to Mach 2: the wave has longer to age on the way down and the shocks merge again, about 86 PLdB. Then tap Just past Mach 1: the shocks bend back up before they reach the ground, and no boom lands at all.

Quiet Boom Lab uses G. B. Whitham’s theory of supersonic flow: each jet is summed up by how its cross-section and lift grow along its length, and the pressure wave ages on its way down through the standard atmosphere. Both jets weigh an assumed 24,000 lb; Lockheed Martin gives the X-59’s take-off weight as about 25,000 lb, and other sources say up to about 32,300 lb. The ordinary jet is built from its parts. The X-59 end is a designed low-boom shape in the same spirit as NASA’s, not NASA’s own numbers.

The loudness reading is a simpler stand-in for NASA’s PLdB scale, set so the X-59 shape at its design point reads 75. The picture is not to scale: the ground is 17 km below a 30 m jet. The model leaves out wind, turbulence, the exhaust plume and the three-dimensional flow near the jet; NASA designed the real X-59 with computer simulations and wind tunnels. The film uses short, credited clips of the X-59 at Fort Worth by spotter @LensOfMae and NASA’s schlieren image of two T-38s and their shock waves (NASA Armstrong); the jets, shock waves and numbers come from the model.