It’s Time to Let Supersonic Flight Soar Again

Before he became the first American to orbit the Earth, John Glenn was famous for another pioneering achievement.

In 1957, he became the first man to fly across the country faster than the speed of sound, traveling from California to New York in just three hours and 23 minutes.

Glenn’s aptly named “Project Bullet” seemed at the time to herald a new age of supersonic flight, in which passengers could cross the globe in an afternoon, thanks to American ingenuity and technological prowess.

Yet, 61 years later, supersonic commercial aviation remains an unrealized dream.

Beginning in 1969, the Concorde proved that routine commercial supersonic flight was technically feasible. It carried passengers at an altitude high enough to see the curvature of the Earth and flew them fast enough to outrun a sunset.

But for all its splendor, the Concorde had problems. It was an expensive, government-subsidized gas guzzler that flew just one commercially viable route—shuttling wealthy passengers back and forth between New York and London.

When it was retired from service in 2003, it left a void. Today, no commercial supersonic transport exists.

Now, a new generation of engineers and entrepreneurs at companies such as Boom, Aerion, and Spike are trying to change all that.

In the half-century since the Concorde was designed, aerospace engineering has made tremendous advancements. Carbon composites are making it possible to build lighter, more heat-resistant aircraft. Today’s jet engine technology permits aircraft to reach supersonic speeds without the need for Concorde’s inefficient afterburners.

If these entrepreneurs succeed, their efforts would constitute a giant leap forward toward the goal of routine, inexpensive supersonic travel.

Frequent fliers may be surprised to learn that one of the biggest barriers these companies face is neither economic, nor technological; it is regulatory. In 1973, the Federal Aviation Administration banned flights exceeding Mach 1—the speed of sound—over the United States.

The FAA indicated it adopted an overland speed limit to protect the public from sonic booms, the shockwaves generated as aircraft push through the air faster than sound.

In the late 1960s, before the Concorde even took flight, there was considerable concern that frequent booms could frighten livestock, shatter windows, or damage physical structures.

Those fears were overblown, and had less to do with science than with hype generated by anti-Concorde activists, whose stated goal was to kill the technology by stirring up public opposition.

In fact, beginning in the late 1950s, the U.S. government conducted a series of tests on the effects of sonic booms. One study in Oklahoma City subjected residents to daily, frequent sonic booms for six months and found that “an overwhelming majority (73 percent) of the public felt they could live with” them. The public, it seemed, hardly considered sonic booms to be intolerable.

Nor were frequent booms found to be damaging to physical structures. In a 1964-65 test at the White Sands Missile Range in New Mexico, investigators subjected a small artificial community to 30 booms a day. The results: Houses constructed of typical materials experienced only the slightest damage when subjected to booms far more intense than those generated by the Concorde.

The investigators found, for example, that paint may chip on plasterboard ceilings when subjected to “repeated booms” with an overpressure of 5 pounds per square foot, the measurement of a sonic boom. Poorly mounted glass chipped at an overpressure of 12.1 pounds per square foot. Items began to fall off walls at 10.4 pounds per square foot.

But NASA data shows that the Concorde, cruising at 52,000 feet at Mach 2 (about 1,500 miles per hour), had a sonic boom of only 1.94 pounds per square foot.

The ill effects of overland supersonic flight seem to have been exaggerated. So, why did the U.S. government ban it? While the FAA’s rule appeared to be a noise abatement measure, it might have had more to do with saving face than saving the public from sonic booms.

Britain and France launched their joint Concorde project to much fanfare in 1962. That same year, the Soviet Union announced development of its own SST, the Tu-144.

Not to be outdone, President John F. Kennedy wanted an American-made supersonic transport aircraft that outdid them both. The result was the Boeing 2707, a government-funded Mach 3 giant that could carry 300 people. But the program foundered and was canceled in 1971.

Perhaps not coincidentally, the ban on overland supersonic flights went into effect two years later and closed the vast majority of the U.S. market to Concorde operations.

Photo: jamesteohart/Getty Images

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