Supersonic Propulsion Research Focuses On Environment

Minimizing airport noise and sonic boom are key for supersonic business-jet engines

Printed headline: Key Developments

Prospects for a supersonic business jet look slim after the steepest decline in corporate aircraft sales in history, but research continues and when the market recovers, provided demand is sufficient, at least one aircraft could enter development this decade. NASA plans wind-tunnel tests on a low-boom supersonic inlet designed by Gulfstream.Credit: NASA CONCEPT For now, research is centered on maximizing the efficiency and minimizing the environmental impact of supersonic transports. Reducing both airport noise and sonic boom are seen as more feasible if the aircraft is small, so studies on both sides of the Atlantic are focusing on a business jet as the first step. Propulsion plays a key role, as no commercial engine exists that can meet the efficiency and environmental goals with the durability required for sustained supersonic cruise. And with the near-term emphasis on reducing sonic boom sufficiently to permit supersonic flight over land, inlet and nozzle design has emerged as a key factor. NASA is focusing research on minimizing boom, and plans wind-tunnel tests of a Gulfstream-designed low-boom external-compression inlet. Other projects will investigate the jet plume impact on sonic boom and the design of 2D nozzles that can help reduce airport noise below Stage 4 levels. In Europe, Russia and the U.S., propulsion research is focusing on engines that can vary cycles from higher bypass-ratio to minimize airport noise to lower bypass for improved supersonic efficiency. Advances in materials and cooling to handle long dwells at high temperatures are also essential.