NASA To Test 'Quiet' Supersonic Flights Over Texas (cnn.com)

NASA announced it will publicly demonstrate a quiet supersonic aircraft near the coastal resort city of Galveston, Texas, to ensure that its prototype really will be barely audible when it crosses the sound barrier. CNN reports: If NASA's experimental project -- formerly known as the X-plane or "Low-Flight Flight Demonstrator" but recently renamed X-59 QueSST -- works, it should help make supersonic flight more economical. From November, NASA will use supersonic F/A-18 Hornet jets over Galveston to mimic the sonic profile of the X-59 while a group of around 500 residents document the noise levels -- if there are any. By performing dives at the speed of sound, the jets will produce two types of sonic boom in order to truly determine the sound they produce on the ground.

According to NASA, Galveston was chosen as the testing area as it's located near the Gulf of Mexico, allowing the fighter jets keep louder sonic booms out to sea, while hurling quieter sonic "thumps" into the city. The secret to the plane's noise-reducing ability is its uniquely shaped structure, designed so that supersonic shockwaves don't build up into powerful sonic booms.

Comments

Re:Huh?

[rednip]

I had to read that again as well. I'd guess that the F-18 (perhaps modified) is expected to make a sound wave similar to what's been modeled, but only under specific conditions. e.g. diving once already above the speed of sound. This is a survey to see if it's really at an acceptable level.

Sonic booms are not caused by crossing the barrier

[students]

"its prototype really will be barely audible when it crosses the sound barrier."

Sonic booms are caused by going faster than the speed of sound. They are not caused by reaching the speed of sound. This is why the boom is a potential problem - it is heard along the entire supersonic flight path, not just at the beginning.

Re:Scope creep

[Anonymous Coward]

*sigh*

The first A in NASA stands for Aeronautics (The study, design & manufacturing of flying machines).

Re:Huh?

[mikael]

Current jets can make sonic booms. That's due to the shape of the aircraft and the wings so that there are two sonic booms due to areas of high air pressure. They can reduce that by a small amount by making minor changes to the airframe and wings:

https://www.youtube.com/watch?...

With the X-59, they completely redesign the airframe and wings so that the pressure waves cancel each other out rather than reinforce each other.

Still not economical

[Pollux]

It should help make supersonic flight more economical.

Supersonic flight still will not be more economical. As this video by Wendover Productions explains, the biggest cost of supersonic flights is the fuel. The Concorde flies 14 miles per gallon of fuel, while the Boeing 787 flies 104 miles per gallon. Also consider the Concorde only carried 128 passengers, while the 787-9 can carry 290. Doing the math, on a 3,470 mile flight from New York to London, a Concorde would consume 1.936 gallons of fuel per passenger, while a 787-9 would consume only 0.115 gallons per customer. That's almost 17 times greater fuel efficiency.

And that's not even beginning to mention the much higher building and maintenance costs of supersonic planes and engines.

Permitting cross-continental flights with a supersonic plane isn't going to matter one bit in the economics of supersonic flight.

Re:Still not economical

[Anubis IV]

The Concorde flies 14 miles per gallon of fuel, while the Boeing 787 flies 104 miles per gallon. Also consider the Concorde only carried 128 passengers, while the 787-9 can carry 290. Doing the math, on a 3,470 mile flight from New York to London, a Concorde would consume 1.936 gallons of fuel per passenger, while a 787-9 would consume only 0.115 gallons per customer.

You’ve misunderstood the fuel economy numbers you quoted, which should have been readily apparent as soon as you tried to suggest that a Concorde got similar fuel economy (14 mpg) to an older car. The original numbers you gave were already on a miles per gallon per passenger basis, so dividing them again by the number of passengers gives you a useless number.