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Aircraft built to break sound barrier with sonic 'thump'

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Designed to cruise at Mach 1.4 at altitude of 55,000 feet

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First test flight appears to have been subsonic

By David Swanson and Steve Gorman

PALMDALE, California, Oct 28 (Reuters) - NASA's X-59

supersonic-but-quiet jet airplane soared over the Southern

California desert on Tuesday in the first test flight of an

experimental aircraft designed to break the sound barrier

without all the noise.

The sleek aircraft, measuring just under 100 feet (30

meters) from nose to tail, took off about an hour after sunrise

from a runway at Plant 42 of the Lockheed Martin Skunk Works

facility in Palmdale, about 60 miles (100 km) north of Los

Angeles.

After a steep climb over sod fields just east of the runway,

the plane was seen banking to the north on a trajectory toward

Edwards Air Force Base, about a dozen miles away, where it was

expected to land. It was accompanied by a NASA chase plane.

The single-engine X-59 appeared to fly at subsonic speeds,

as was expected for its initial test flight.

A crowd of about 200 aerospace workers and their families

watched the takeoff from a safe distance parked along a nearby

highway.

A Lockheed Martin ( LMT ) spokesperson, Candis Roussel, told Reuters

in a brief email statement that the "X-59 successfully completed

its first flight this morning" and hailed it as a "significant

aviation milestone." She said the company would provide details

later.

The X-59, a one-of-a-kind experimental aircraft, is built to

reach a cruising speed of 925 mph (1,490 kph), or Mach 1.4, at

an altitude of 55,000 feet (16,764 meters), more than twice as

high and roughly 60% faster than typical airliners fly.

The plane's unique shape is designed to greatly reduce the

explosive-like sonic boom normally produced when an aircraft

breaks the sound barrier, lowering the volume to a muffled

"sonic thump" no louder than slamming a car door.

Perfection of such low-decibel flight technology could make

supersonic aircraft more conducive to commercial aviation

service, especially over populated areas.

The supersonic Concorde aircraft began scheduled

transatlantic flights with British Airways and Air France in

1976. But the plane was retired in 2003 due to high operating

costs, limited seating and sluggish passenger numbers following

a fatal crash in July 2000 and the September 11 attacks in 2001.

In press materials posted online last month, NASA said the

X-59's first flight would be a "lower-altitude loop at about 240

mph (386 kph) to check system integration, kicking off a phase

of flight testing focused on verifying the aircraft's

airworthiness and safety."

During subsequent test flights, the X-59 will travel higher

and faster, eventually exceeding the speed of sound -

approximately 761 mph (1,225 kph) at sea level.

The California Manufacturers & Technology Association

earlier this month named the X-59 as 2025's "Coolest Thing Made

in California" in its annual statewide technology contest.