NASA boom comes to Galveston: is the test well timed?

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Galveston sound tests could herald new generation of supersonic flight

Sonic Boom tests when airport neighbors hate Stage IV

Well designed Test

Define Acceptable Boom standard

Andrea Leinfelder of the Houston Chronicle covered a NASA news conference at which it unveiled plans to conduct a series of supersonic technology research flights over the Galveston, Texas, area, in support of the agency’s Commercial Supersonic Technology Project. Her article did an excellent job of reporting about the Sonic Boom tests and more of that briefing will be reviewed below.

But first, might this NASA effort to define maximum acceptable loudness of a sonic boom cause collateral damage? While the FAA and industry are planning for a more stringent Stage 5 standard, the Stage 4 aircraft—a marked improvement over the previous measurements—draws significant negative community response. It may be that NextGen and RNP have created corridors with more impact, or that citizen expectations exceed measurable noise, but whatever the source of the problem needs to be addressed soon.

With that storm brewing, is it the best public policy strategy to be assessing the citizens’ response to sonic boom NOW ? Yes, the lead times for research of a new generation of SSTs points to early definition of a boom standard, but the Galveston flights may create a shock wave beyond the Texas coast.

The Why?

 

 

 

 

 

Low Boom Flight Demonstration X-plane, or LBFD.

NASA ‘s mission is to “perform flight research and technology integration to revolutionize aviation and pioneer aerospace technology.” To explore the possibility of supersonic flight, it awarded. Lockheed Martin Aeronautics Company a $247.5 million contract to build a faster-than-sound X-plane — now with the official designation of X-59 “QueSST”.

As a predicate to the design, NASA needs a boom impact standard, because the existing maximum acceptable loudness of a sonic boom is not specifically defined under the current FAA regulation. The Galveston research is designed to identify a loudness level that is acceptable to both the FAA and the public, and to reduce the noise created by supersonic aircraft.

“We’ll never know exactly what everyone heard. We won’t have a noise monitor on their shoulder inside their home,” Alexandra Loubeau, NASA’s team lead for sonic boom community response research at Langley, Virginia, said in a statement. “But we’d like to at least have an estimate of the range of noise levels that they actually heard.”

It will be two to three years before the NASA SST model will be ready for flight; so, the F/A-18 Hornet will be used to measure how receptive (or not) Galvestonians will be. It’s basically a test for NASA to learn the best way to survey communities once the X-plane is flying.

What’s a Sonic Boom?

Peter Coen[1], manager for the Commercial Supersonic Technology Project in NASA’s aeronautics mission directorate, simplification of this phenomenon. “A sonic boom happens because the air doesn’t know the airplane is coming.” Most of the aircraft in the civilian fleet generates a sound wave which is moving faster that the plane and is heard on the ground before it reaches that point.

“When a plane travels toward you at speeds below the speed of sound, you can hear it coming because the sound wave is moving faster than the plane. But when the plane breaks the sound barrier, it slams into the air without any warning. This creates multiple shockwaves.

Those shockwaves converge as they travel to the ground, causing what sounds like a bang. But by making small adjustments in the shape of the nose or canopy or wings, you can smear out that shockwave, “so instead of a bang, you just hear a thump,” he says.

The main feature of this new, supersonic test plane will be a long pointy nose. “Supersonic aircraft tend to be long and slender,” says Coen. “Low boom supersonic aircraft is that to an extreme.”

[1] Peter Coen is the manager for the Commercial Supersonic Technology Project in NASA’s Aeronautics Research Mission. In this role he leads a team from four of NASA’s Research Centers in the development of tools and technologies for a new generation of quiet and efficient supersonic civil transport aircraft. Peter has worked at NASA for 35 years. During his career he has studied technology integration in practical designs for many different types of aircraft and has made technical and management contributions to all of NASA’s supersonics related programs for over 25 years. As Project Manager, he has led these efforts for 12 years. Peter is a licensed private pilot who has amassed nearly 30 seconds of supersonic flight time.

The Test

 

NASA research pilot Jim “Clue” Less is putting his flying skills to the test while supporting low-boomflight research. Credits: NASA / Maria Werries

The test flights will start in November 2018 with Ellington Airport as the point of origin. The booms will be experienced for a total of 10 days over the course of 14-21 November days. The typical daily test–between one and eight of these reduced sonic booms each day.

The “quiet supersonic dive maneuver”: the NASA F/A-18 will reach about 50,000 feet in altitude at about five miles in the Gulf. Then, Pilot Less will set his dive at a 53-degree angle. The energy generated by the thrust and dive will bring the F/A-18 to the desired supersonic speeds. shuts down his F/A-18’s afterburners moving just shy of Mach 1, the speed of sound, or about 630 mph at this altitude.

Most of that sound will be directed at the Gulf. Pilot Less will continue at supersonic speeds after it starts to pull out of the dive at 8,000 feet lower. This maneuver will direct some of the sound toward Galveston. The goal is for the jet to be producing a sound level near the NASA’s expected noise parameters. If all goes as planned, a thump noise will be projected towards Galveston and islanders will hear it.

NASA will enlist 500 Galvestonians to participate in the research and they will send postcards to the agency collection of data via postcards which will record their perception of the noise.

Hear the difference between the booms and thumps in the video above. You can hear a double boom at 43 seconds and a thump at 2:34.

Peter Coen explained that “If a traditional sonic boom is hearing a thunderstorm directly overhead, then the new reduced sonic boom will be like hearing a storm rumble far in the distance. The noise has also been described as a neighbor down the street slamming a car door.

Hard data will be gathered by remote sensor devices positioned across Galveston to record the sound. The two sets of numbers will be correlated to determine if the responses show a significant threshold at which a regulatory standard could be set.

An engineer, calibrates one of several microphones which are used for gathering community response to sonic booms..

 

 

 

 

Credits: NASA / Lauren Hughes

According to Coen, the sound will not harm pets, animals or homes. The main purpose of this test is to help NASA better collect data from people so that they can continue in developing supersonic airplanes that will not cause a lot of noise. NASA will reach out to the mariner community in advance of the test flights to help alert everyone who might be out on the Gulf waters during the exercises. The noise level over the Gulf will be louder than what is heard in Galveston, but future planes will not have the same level of noise.

Engineers, pilots, and researchers are enthusiastic about reaching this milestone in development of supersonic airliners. “The ability of everyday people to fly at supersonic levels is a promise overdue,” commented Coen.

Mayor of Galveston’s Reaction

Mayor of Galveston, Jim Yarbrough thanked NASA for selecting Galveston. When asked by a reporter what the benefit would be to Galveston he responded, “This is about being part of a bigger picture, of something that will change aviation dynamics,”  and “I can’t think of a significant event or a significant project in world history that didn’t start with a crazy idea (such as) commercial flights faster than the speed of sound.”

NASA hopes that the “quiet supersonic dive maneuver” is well received by the Galveston public and hopefully it does not create a boom among the anti-noise community.



 

 

 

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