NASA researchers are on a quest to take the boom out of sonic booms, a development that could lead to a new generation of supersonic aircraft and perhaps even usher in a new era of supersonic passenger flight.

Researchers at Dryden Flight Research Center in California are wrapping up a test program called Lift and Nozzle Change Effects on Tail Shock, which is a wordy way of saying they're studying the impact that wing lift and exhaust plumes have on shock waves. It's an early step toward building aircraft that can break the sound barrier without the telltale boom people on the ground so often object to.

"Big picture: We want to learn how to build a plane with a low sonic boom," project manager Tim Moes told Wired.com. "Understanding shock waves is going to help get us there."

Airplanes create pressure waves as they move through the air, much like boats create a wake in the water. When supersonic airplanes exceed the speed of sound — 343.14 meters per second or 767.58 mph (in dry air at 68 degrees Fahrenheit) — these waves form shock waves that create a boom when they hit the ground. Public opposition to the racket is one reason supersonic passenger travel never really caught on in America.

NASA's attempt to stifle sonic booms is focused on changing the shape of the shock waves — a technique called boom-shaping — to spread them out over a larger area so they sound more like distant thunder. Earlier experiments focused on shaping the shock wave at the front of the craft; now NASA is focusing on the rear by experimenting with different wing shapes and air flow over the jet engines.

The tests, known by the acronym LANCETS, uses two F-15 fighter jets. The first, shown in the picture above, has been fitted with canards, or small wings, just ahead of the main wings. "It's the only F-15 in the world that has canards," Moes says. The canards and engine nozzles can be adjusted in flight, allowing NASA to better understand the role they play in the strength of a shock wave. Trying to accomplish similar results in conventional aircraft would be impossible without major modifications to the wings. A second F-15 outfitted with a nose-cone spike and specialized instrumentation follows close behind, measuring shock waves produced by the lead aircraft. This "real world" data will help calibrate computer models of how shock waves form.

Once NASA has crunched all the data, the next step is modifying a jet to make its sonic boom more of a sonic rumble. Such a craft would cost as much as $100 million, Moes told New Scientist, and could be airborne within four or five years.

New York to L.A. in two-and-a-half hours? Someday, it just might happen.

Photo: NASA/Dryden Flight Research Center