aerobd.news : Lockheed Martin is to build and flight test a quieter supersonic aircraft in 2021, after it was awarded a US$248m contract by NASA. The Low-Boom Flight Demonstrator will be a piloted, full-scale experimental aircraft, known as an X-plane, and will prove the quiet sonic boom design required for supersonic passenger air travel.

The aircraft will be built at the Lockheed Martin Skunk Works facility in Palmdale, California, and will be based on a design developed under NASA’s Quiet Supersonic Technology (QueSST) project, which ran between February 2016 and June 2017.

The proposed aircraft will be 94ft long with a wingspan of 29.5ft and have a fully-fueled take-off weight of 32,300 lb.

The design research speed of the X-plane at a cruising altitude of 55,000ft is Mach 1.42 (940mph) and its top speed will be Mach 1.5 (990mph). The jet will be propelled by a single General Electric F414 engine, the powerplant used by F/A-18E/F fighters.

Jaiwon Shin, NASA’s associate administrator for aeronautics, said, “It is super exciting to be back designing and flying X-planes at this scale. Our long tradition of solving the technical barriers of supersonic flight to benefit everyone continues.”

The X-plane will help NASA establish an acceptable commercial supersonic noise standard to overturn current regulations banning commercial supersonic travel over land.

“We’re honored to continue our partnership with NASA to enable a new generation of supersonic travel,” said Peter Iosifidis, Low-Boom Flight Demonstrator program manager, Lockheed Martin Skunk Works.

“We look forward to applying the extensive work completed under QueSST to the design, build and flight test of the X-plane, providing NASA with a demonstrator to make supersonic commercial travel possible for passengers around the globe.”

Current regulations, which are based on aircraft speed, ban supersonic flight over land. With the low-boom flights, NASA intends to gather data on how effective the quiet supersonic technology is in terms of public acceptance by flying over a handful of US cities, which have yet to be selected.

The complete set of community response data is targeted for delivery in 2025 to the Federal Aviation Administration (FAA) and the International Civil Aviation Organization (ICAO) from which they can develop and adopt new rules based on perceived sound levels to allow commercial supersonic flight over land.

In a conventional aircraft the shockwaves generated when the sound barrier is broken coalesce as they expand away from the airplane’s nose and tail, resulting in two distinct and thunderous sonic booms.

The X-plane’s hull sends those shockwaves away from the aircraft in a way that prevents them from coming together in two loud booms. Instead, the weaker shockwaves reach the ground still separated and will be heard as a quick series of soft thumps.

The initial ideas for the design can be traced back to the 1960s. However, recent research using wind-tunnel testing, computer simulation and flight testing has improved the aerodynamic efficiency of supersonic aircraft wings, and improved the understanding of sonic boom propagation through the atmosphere.