NASA PLANS SONIC BOOM FLIGHT TESTS GOAL IS TO MAKE AIRCRAFT MORE ECO- AND COMMUNITY FRIENDLY.

Byline: JIM SKEEN

Staff Writer

EDWARDS AIR FORCE BASE -- NASA is continuing its research into sonic booms this week to glean information that can be used to make future supersonic aircraft more environmentally and community friendly.

NASA Dryden Flight Research Center will be conducting a series of sonic boom tests beginning Wednesday to examine the structural response of modern housing construction to sonic booms. The testing will run from 8 a.m. to 3 p.m. through July 20.

The data will be compared with similar testing done last year using an older home.

"That was a rickety house that was to be demolished," said Ed Haering, a Dryden sonic-boom researcher. "This is a modern house. We expect it will be a lot quieter."

The experiment consists of NASA F-18 research aircraft flying unique profiles to present sonic booms to an Edwards base house instrumented to measure both pressure and vibration. These flight profiles are designed to keep focused sonic booms away from surrounding communities, NASA officials said.

Called the Housing Structural Response to Sonic Booms Test, the effort will look at how two different kinds of sonic booms -- normal and low-amplitude -- affect the house.

Four low-boom and two normal-intensity-boom missions are scheduled, with up to six sonic booms on each mission. Booms may occur six minutes apart. No more than two missions will be flown on one day.

Normal sonic booms have 1 to 2 pounds per square foot of air pressure. Low-amplitude, or "quiet" sonic booms, have one-tenth of a pound per square foot of pressure, Haering said.

Sonic booms occur as supersonic aircraft push aside air molecules with great force. This forms a shock wave, much as a boat creates a bow wave. The bigger and heavier the aircraft, the more air it displaces, NASA officials said.

The shock wave creates a cone of pressurized air molecules that move outward in all directions and extend to the ground. As the cone spreads across the landscape along the flight path, there is a continuous sonic boom along the full width of the cone's base.

For now, supersonic aircraft are restricted to flying over certain test ranges in the United States. Developing technologies to lessen the impact of the booms could open the national airspace to supersonic business and commercial flights.

Engineers from NASA's Langley Research Center in Hampton, Va., are providing and operating more than 100 sensors inside and outside the house, including a microphone 250 feet from the house, NASA officials said.

NASA Dryden will mount microphones on a 35-foot tower in a field adjacent to the house, with additional microphones on the ground up to 35 feet from the tower. A Boom Amplitude and Direction Sensor, or BADS, and a ground weather station will also be operated by Dryden personnel.

An Air Force Test Pilot School L-23 Blanik sailplane outfitted with NASA Dryden microphone equipment will also fly during the experiments to gather airborne sonic-boom data.

The sailplane records the sonic booms before the booms enter the more turbulent air that exists a few thousand feet above the ground because turbulence can greatly influence sonic boom intensity.

Dryden has conducted a number of sonic-boom research projects in recent years, including a 2003 effort with Northrop Grumman and the Defense Advanced Projects Research Agency that examined whether altering an aircraft's shape could affect the intensity of a sonic boom. That research showed sonic booms could be made quieter.

Dryden also provided support to an effort last year by business jet maker Gulfstream to test whether the use of a telescoping pole could break up pressure waves to soften sonic booms.

Noise-related questions should be forwarded to Air Force Flight Test Center public affairs at [phone].

james.skeen(at)dailynews

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