Supersonic air travel might again be a possibility as NASA and Lockheed Martin cooperate to design a plane that can break the sound barrier with almost no sonic boom.
Supersonic passenger planes were banned in the United States in 1973 because of complaints about the sonic boom, pressure waves that caused shocks, and shaking up to 30 miles away.
Between the advent of supersonic flight in the 1950s and through the 1960s, Lockheed Martin reported that citizens filed some 40,000 claims against the Air Force for damage and disturbances caused by sonic booms. In 1973, the Federal Aviation Administration (FAA) banned overland supersonic air travel to avoid future problems.
Because of this rule, the supersonic Concorde airliner was limited to flying across the Atlantic, between New York and Europe.
Supersonic commercial travel is starting to take shape! Our Skunk Works® team started manufacturing of the X-59 QueSST. pic.twitter.com/PZq9f7mxZ6
— Lockheed Martin (@LockheedMartin) November 16, 2018
Now NASA has hired Lockheed to build a supersonic plane quiet enough to cause the FAA to revisit its 1973 ruling. Lockheed began initial production on Nov. 16.
Design work begun by NASA in conjunction with Lockheed’s aeronautics branch will eventually lead to the next-generation supersonic airliner—one designed to produce sonic shock waves no louder than the slamming of a car door.
The new plane, named the X-59 QueSST, (QuiEt SuperSonic Transport) is projected to have a cruising speed of Mach 1.4, or over 1,000 mph, at an altitude of 55,000 feet. This will mean three to four hour flights across the country, or across the Atlantic.
Building the Boom-less SST
On April 2, Lockheed Martin announced that it had been awarded a $247.5 million contract to produce a test plane that would fly at supersonic speeds with minimal sonic disturbances to people on the ground below, Space.com reported.
Lockheed’s famous Skunk Works team was selected to design, build, and flight-test the Low-Boom Flight Demonstrator (LBFD), a miniature, 94-foot version of what will eventually be the X-59 QueSST quiet supersonic airliner.
In fact, there is no supersonic plane that will not produce sonic booms, explained Thomas Corke, professor of engineering at the University of Notre Dame.
“The idea is that there is no way to avoid a shock wave supersonically,” Corke, who directs Notre Dame’s Institute for Flow Physics and Control. “The [X-plane] design doesn’t eliminate shock, it just minimizes it, so what’s perceived on the ground is almost imperceptible.”
Lockheed Martin will spend the next 17 months designing and building its prototype, which is scheduled for a 2021 delivery date.
— Lockheed Martin (@LockheedMartin) November 16, 2018
The program began in 2010 with NASA’s with the N+2 Supersonic Validations Program.
“We worked with NASA to develop the necessary design tools and experimental techniques to accurately shape the vehicle so that its sonic-boom signature will be perceived as a sonic heartbeat sound rather than the typical loud double-bang that today’s supersonic aircraft produce,” said Michael Buonanno, chief engineer for NASA’s Quiet Supersonic Technology (QueSST) X-plane program.
“In order to have low sonic boom, you need to specifically design to have it,” Buonanno continued. “It’s a nuanced and detail-oriented task to set up the shape of the vehicle so that the shock waves that result from supersonic flight don’t coalesce and result in that loud double-bang.”
According to Lockheed, modern planes, which are all basically tubes with wings, cause shock waves to roll along the fuselage and collect into a single large sonic explosion behind the plane.
The QueSST plane will look more like a lawn dart crossed with a stealth fighter—a very long, sharply pointed nose, flat planes, sharp angles, and a large triangular wing.
The design is intended to scatter the multiple shock waves that form when the plane’s leading surfaces hit the atmosphere, rather than concentrating them.
Public Testing Might Help Change the Law
Even if the plane is built on schedule and performs to specification, air travelers might not be taking supersonic flights in 2021. The FAA ruling is still in place.
NASA has been over Texas to determine how loud a noise a plane can produce without unduly disturbing residents below.
A modified F-18 fighter jet flew over Galveston, Texas, on Nov. 19, diving at supersonic speed to create a series of sonic booms of different decibel levels.
NASA recruited 500 Galvestonians to listen for the booms and rate how unsettling they were.
Jerry Baker, 46, is one of the chosen respondents. He told the Daily Mail that he heard ‘several loud bangs’ during the test flights.
“The first one was the loudest,” said Baker. “It rattled the windows.”
Later tests got gradually quieter.
“I just heard one, right at eleven o’clock,” Baker said. “Very small, two tiny bumps.”
The LBFD test plane will perform a similar set of tests over populated areas.
The prototype will fly over select U.S. cities. After the fly-overs, residents will be polled to see how they responded—or if they even noticed.
At a news conference on April 3, Jaiwon Shin, associate administrator of NASA’s Aeronautics Research Mission Directorate, said that NASA would send the polling data to the FAA and the International Civil Aviation Organization (ICAO) “so they can use the data to change the current rule that completely bans civil supersonic flights over land.”
“When the rule is changed, the door will open to an aviation industry ready to enter [a] new supersonic market in our country and around the world,” Shin said. “This X-plane is a critical step closer to that exciting future.”