Reductions in supersonic boom intensity could allow for overland operation of future supersonic civil aircraft, according to a panel of supersonic technology experts at a meeting held on March 1 in Palm Springs, Calif. The session was part of the UC Davis Aviation Noise & Air Quality Symposium.
Representatives from the FAA, NASA, Boeing, Gulfstream Aerospace and Lockheed Martin discussed the ways they are studying to reduce the intensity of the sonic boom. Supersonic Aerospace International CEO Michael Paulson, whose company is located in Las Vegas, was unable to attend the meeting. His company did coordinate some of the information with Lockheed Martin for its presentation, he said. Lockheed Martin has conducted research for Paulson’s company in the past.
Research in sonic boom mitigation “has demonstrated enough progress on reducing impact of sonic booms before they reach the ground for us to revisit this issue,” said Lourdes Maurice, FAA chief scientific and technical advisor for environment. She emphasized that no progress will be made in civil supersonic aircraft development without public involvement to define an “acceptable sonic boom requirement.” One of the goals of the panel session, she added, is “to raise public awareness on advances in supersonic technology, and for the FAA, NASA and industry to get feedback from interested persons.”
NASA’s Peter Coen explained that a sonic boom is not an isolated event–the breaking of the sound barrier by an aircraft–but “is created as long as the aircraft is flying faster than Mach 1.0.” A three-dimensional cone-shaped area impacts people on the ground, exposing a “carpet” of ground to the boom as the aircraft flies overhead. By careful application of aircraft shaping techniques, he explained, the boom signature can be reduced dramatically, “potentially more than 35 dBA of reduction.”
Gulfstream Aerospace envisions a Mach 1.8 quiet supersonic jet (QSJ) that would meet strict airport noise and emissions standards, including a 10-dB margin below Stage 4 airport noise requirements. Gulfstream’s quiet spike research, conducted using an extendable spike mounted on the nose of an F-15, proved the structural integrity of the design and briefly tested the noise-suppression characteristics.
According to Gulfstream’s panel participant, director of supersonic technology development Robbie Cowart, the quiet spike as contemplated on a QSJ would “transform a sharp crack into a quiet whisper.” Adding low-boom design techniques would further cement a QSJ’s acceptance by the public. Research results so far look promising, he said.
Robert Rackl, principal engineer in Boeing’s noise engineering group, summarized his company’s view of supersonic technology in his presentation. “Boeing has a continuing interest in technologies that could eventually enable a next-generation supersonic airliner,” he noted, adding that this means “viable economically, environmentally and operationally.” And while Boeing recognizes that “supersonic business jets are likely a necessary interim step for the industry and regulators…there is no Boeing SSBJ product currently in development and there are no plans to launch such a program. We don’t have all the answers, but we’re systematically tackling key questions and working toward practical solutions.”
“Environmentally compatible quiet supersonic transportation” will reduce sonic booms to “sonic puffs,” according to John Morgenstern, Lockheed Martin specialist in design of low-sonic-boom supersonic aircraft.