If there's a pantheon of great airplanes, the X-planes deserve an entire wing of the place. Since the Chuck Yeager-toting Bell X-1 broke the sound barrier in 1947, these experimental aircraft have pushed up against, and burst through, the boundaries of flight. The X-15 was the first plane to demonstrate hypersonic flight—over Mach 5—and set a manned speed record in 1967. In the early 2000s, the X-35 evolved into the F-35 fighter jet. The latest in the line, the X-57, is working to prove electric power can work as well in the air as on the ground.

NASA, which runs the X-plane program, has just announced the newest member of this vaunted club. The space and aeronautics agency is giving Lockheed Martin a $247.5 million contract to build a supersonic aircraft. Now, flying faster than sound is the easy part. The real trick is doing it without creating the eardrum-battering sonic boom, a key hurdle to reviving supersonic flight for civilians.

The goal is to clear the way for a successor to the supersonic Concorde, which started service in 1976. That plane created such a loud crack as it blasted overhead that regulators banned it from flying at supersonic speeds over people in the US and Europe. Effectively relegated to a few transatlantic routes, the Concorde struggled financially, and was retired in 2003. A quieter plane, the thinking goes, could ease those restrictions, and allow more profitable flights of rich, important, businesspeople from New York to LA and San Francisco, as well as across the ocean.

“This X-plane is a critical step closer to that exciting future,” says Jaiwon Shin, who runs NASA's aeronautics research. “People enjoying affordable, quiet, supersonic flights in the future will say April 3rd, 2018 is the day it all began.”

Lockheed Martin's task is to build a one-off, manned, flying example of a prototype it has been developing for a couple of years: the Low Boom Flight Demonstrator. The aircraft doesn’t have an official X designation yet—NASA will apply to the US Air Force for that in the next few months—but the logical guess is X-58. It would be the first manned X-plane in a generation, after a series of remote controlled demonstrators.

The Low Boom Flight Demonstrator takes the Concorde's long pointy nose and swept back wings to an extreme. The result looks like a missile with small wings, which should minimize the pressure waves that come off the plane in supersonic flight—they’re what make all the noise. The plane is designed to hit 940 mph and cruise at around 55,000 feet, far higher than the typical 35,000 for subsonic airliners. For people on the ground, Lockheed says, the shockwaves should sound more like a car door closing than the Concorde's canon-like boom. The jet will be propelled by one General Electric F414 engine, the sort used in F/A-18 fighters. The cockpit design will be the same as the rear seat in the T-38 training jet.

“A supersonic manned X-plane—this is probably going to be a once-in-a-lifetime opportunity for me," said Jim Less, one of two NASA pilots lined up to fly the plane from NASA's Armstrong Flight Research Center in California. "We’re all pretty excited.”

If you too are excited about the idea of Yeager-ing your way across the country, get ready to wait. Although NASA hopes the technology will eventually lead to civilian airliners, this plane will be just 96 feet long, with room for a solo pilot. “This airplane, like the Bell X1, or the X15, is a purpose built experimental research aircraft,” says Dave Richardson, the director for air vehicle designs and technologies at Lockheed Martin. He says he fields a lot of questions about where the passengers or missiles go, but that this isn’t a prototype business jet or weapons system. Its mission isn't carrying CEOs or taking out enemies—it's defeating the boom.

NASA hopes to start flying the plane in 2021, if Lockheed meets its production targets. To date, the contractor has tested scale models in a wind tunnel. (“I’ll lose a lot more hair in the time between now and then,” says Richardson.) It will operate over test ranges first, to make sure it’s safe, then start flying over select US cities in 2022, accompanied by surveys of the people on the ground. If all goes according to plane, those folks won't be bothered—and eventually, they'll be able to join in on the fun.

Such Great Heights