In April, NASA took another major step toward reintroducing supersonic flight with an award to Lockheed Martin Aeronautics Company to design, build, and test a supersonic aircraft to reduce sonic boom.
 
This Low-Boom Flight Demonstration (LBFD) mission, set for 2021 completion followed by testing, is leading a government-industry team collecting data that could make supersonic flight over land possible for the first time since the 1973 Federal Aviation Administration ban—and dramatically reducing travel time anywhere in the world.
 
The LBFD X-plane, could be a key contributor in changing sound-based rules prohibiting supersonic flight over land, opening doors for new commercial cargo and passenger markets to provide faster-than-sound air travel.
 
“It is super exciting to be back designing and flying X-planes at this scale,” said Jaiwon Shin, NASA’s associate administrator for aeronautics. “Our long tradition of solving the technical barriers of supersonic flight to benefit everyone continues.”
 
Sonic boom is created when a conventional aircraft reaches the speed of sound, which at 68 °F is approximately 767 miles per hour. A series of shockwaves of different strengths coalesce as they expand away from the aircraft’s nose and tail, resulting in two distinct and thunderous sonic booms that travel to the ground and are loud enough to break windows or cause minor structural damage.
 
In a cost-plus-incentive-fee contract valued at $247.5 million, Lockheed Martin’s proposed 94-foot-long X-plane, with a wingspan of 29.5 feet, will cruise at an altitude of 55,000 feet at a speed of about 940 miles per hour, and reduce sonic boom to 75 Perceived Level decibel.
 
The new X-plane design quiets sonic boom with a uniquely-shaped hull that generates supersonic shockwaves but prevents them from coalescing, or coming together, as they move away from the aircraft. When these shockwaves weaken and reach the ground separately they’ll be heard only as a quick series of soft thumps (as quiet as a car door closing) if at all.
 
“This careful shaping of the aircraft cross-sectional area and lift distribution prevents the shockwave emanating from the aircraft from merging with other shockwaves in the atmosphere below the aircraft,” says J.D. Harrington, Public Affairs Officer for NASA.
 
The LBFD mission is the culmination of years of testing to reduce sonic boom by NASA and others, stretching back to 1947 when an aircraft first broke the sound barrier. More recently, NASA’s wind-tunnel testing, advanced computer simulation tools, and actual flight test investigations continued to improve aerodynamic efficiency of supersonic aircraft wings and understanding of sonic boom propagation through the atmosphere.
 
NASA isn’t the only organization focused on supersonics these days. In a move that shaped research and development in the aerospace industry, the DOD’s Defense Advanced Research Projects Agency (DARPA) requested a 136-percent budget increase over last year in the field of hypersonics.
 
Hypersonic aircraft cruise at speeds of at least five times the speed of sound, or Mach 5. DARPA is undergoing an effort to promote a National Hypersonics Initiative with the Pentagon, to answer strides made in hypersonics by China.

Lockheed Martin named hypersonics one of four growing transformative technologies (which also included lasers, artificial intelligence, and electronic warfare) that will radically alter armed conflict. Hypersonics could allow combat forces to quickly address threats before an adversary has time to react, creating significant tactical and strategic advantages equivalent to how stealth technology first thwarted radar.
 
If NASA accepts Lockheed Martin’s X-plane, the agency will perform additional flight tests to prove the low-boom technology works, aircraft performance is robust, and it’s safe to operate in the National Airspace System in mid-2022. NASA plans to test the X-plane over select U.S. cities and collect data about human responses to the low-boom flights before delivering it to U.S. and international regulators.
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