WASHINGTON – NASA is set to publicly demonstrate and test a flightmanoeuvre that allows jets to travel faster than sound without generatingthe characteristic sonic boom.
Supersonic flight over land was banned in the US because they generatedcharacteristic loud sonic booms, that could sometimes damage buildings.
Using a repurposed fighter jet F/A-18, NASA showed that a diving manoeuvrecan be used to generate quiet sonic thumps over a specific area.
An initial test of the research methodology using the F/A-18 was conductedin 2011 with the help of the US military community that lives on base atEdwards Air Force Base in California.
Researchers want to take the show on the road and try the same thing over acommunity that is not used to sonic booms regularly sounding on any givenday the way the Edwards community is.
Using the F/A-18 and its ability to aim quiet sonic thumps at a specificarea, teams from Armstrong, Langley Research Center in Virginia, andJohnson Space Center in Texas plan to conduct a series of data-gatheringflights over Galveston, Texas, in November 2018.
The Gulf Coast city was chosen because it was next to the Gulf of Mexico,which enables the F/A-18 to keep its louder sonic booms (near the divepoint) out to sea, while throwing the quieter sonic thumps (far forward ofthe dive point) at Galveston.
At least 500 resident volunteers will be solicited to provide input to asecure web site about what they have heard, if anything, and what they feltabout the sound.
At the same time, audio sensors strategically placed around the city willprovide researchers a measure of scientific ground truth about how loud thenoise really was.
“We’ll never know exactly what everyone heard. We won’t have a noisemonitor on their shoulder inside their home. But we’d like to at least havean estimate of the range of noise levels that they actually heard,” saidAlexandra Loubeau, NASA’s team lead for sonic boom community responseresearch at Langley.
NASA recently awarded Lockheed Martin Aeronautics Company a USD 247.5million contract to build a faster-than-sound X-plane – official designatedX-59 “QueSST” – that will demonstrate quiet supersonic technologies instraight and level flight over a large area.
Part of the Low-Boom Flight Demonstration mission, the X-59 is shaped sothat supersonic shockwaves do not coalesce together to create thecharacteristic sonic booms, which prompted the government to ban supersonicflight over land years ago.
“With the X-59 you’re still going to have multiple shockwaves because ofthe wings on the aircraft that create lift and the volume of the plane. Butthe airplane’s shape is carefully tailored such that those shockwaves donot combine,” said Ed Haering, an aerospace engineer at NASA ArmstrongFlight Research Center.
“Instead of getting a loud boom-boom, you’re going to get at least twoquiet thump-thump sounds, if you even hear them at all,” Haering said.
NASA intends to fly the X-59 over several towns or cities and gather datafrom residents on the ground about their perception of the sound thesupersonic aircraft generates.