Dawn of a new supersonic era

According to official records, the first attested supersonic flight in history took place 75 years ago on October 14, 1947. The pilot was 24-year-old U.S. Air Force pilot Charles Elwood “Chuck” Yeager. The Germans, however, had presumably already broken the sound barrier a few times in April 1945 during the final phase of World War II. They achieved this with the Messerschmitt Me 262, the world’s first production jet fighter, which debuted in 1943. Yeager was in a Bell X-1, a single-seat rocket-powered plane specifically designed to break the sound barrier for the first time in level flight, not in a dive as had been done before.

Measuring less than ten meters long, the aircraft was painted a striking orange to be more visible in the air or, in the worst-case scenario, on the ground after an accident. It was simple in design and didn’t even have an ejection seat—unthinkable in military testing today. The X-1’s mothership, a Boeing B-29, took off from Muroc Air Force Base (renamed Edwards Air Force Base in 1950) in California’s Mojave Desert east of Los Angeles. After the Boeing reached an altitude of about 6,000 meters, Yeager climbed into the test aircraft through the empty bomb bay and the X-1 was then released. Once he was far enough away from the mothership, he ignited the four-chamber rocket motor, which was based on German rocket technology.
 
The X-1 rapidly climbed to 12,800 meters. Its fuselage was patterned after a standard bullet because this shape was known to have a stable flight attitude at supersonic speeds, even though it was rather ill-suited to the aerodynamics of ordinary aircraft. At cruising altitude, Yeager accelerated the aircraft to Mach 1.06, equivalent to 1,079 kilometers per hour (km/h). Observers on the ground heard a dull double bang, as would happen from then on whenever the sound barrier was broken over Edwards—the sonic boom that is still unavoidable today. Just 14 minutes after disengaging and successfully completing his pioneering feat, Yeager landed the X-1 back at Muroc.

A victory for the Soviet Union: The Tupolev Tu-144

While supersonic flight was a purely military domain in its early decades, by the late 1960s a race was developing between East and West to see who would be the first to get supersonic passenger aircraft into the air. It was the Soviet Union that achieved this on the last day of 1968 with the Tupolev Tu-144. The elegant aircraft with the white delta wings was a world sensation that could carry as many as 140 passengers at speeds of up to Mach 1.88. The French-British Concorde, the competitor from the West, did not celebrate its maiden flight until March 2, 1969; but then it managed Mach 2.02, twice the speed of sound. At that time, the industry assumed that, within a few years, at least the longer passenger flights would be flown solely by supersonic jets. The Boeing 747, which was developed at the same time, was intended primarily for cargo transport.
 
But things turned out differently: the 1973 oil crisis made kerosene extremely expensive, and concerns grew about noise and sonic booms. The Tupolev Tu-144 performed only pro forma “regular” flights through the end of 1978. Although the Concorde remained a commercial flop, its scheduled service proved to be a thoroughly popular means of transport between 1976 and 2003 for passengers in a hurry. This was especially true on the route from Paris or London to New York, which could be completed in just about three hours. But with round-trip ticket prices of around 7,000 euros in today’s currency, this remained a pleasure for an exclusive group.

60 years after the Concorde’s maiden flight—a new supersonic era?

Some 20 years after the Concorde was retired, Boom Supersonic is venturing into a new supersonic era. The company is currently developing a new jet in the U.S. called Overture. Debuting 60 years after the Concorde’s maiden flight, it is expected to carry between 65 and 80 passengers and reach Mach 1.7 over water as early as 2029. Over land, however, where supersonic flights have been banned to date because of the sonic booms, Overture will stay just below the sound limit at Mach 0.94.

In its QueSST project, NASA is currently researching shapes for supersonic aircraft that should reduce the bang to such an extent that fast flights could also be possible over land in the future (see interview "Research on how to achieve a quieter sonic boom"). Three major carriers—Japan Airlines, United Airlines and American Airlines—have already ordered a total of 55 Overtures with options for more.

Supersonic flight in the 2030s is expected to have far less impact on the environment than the Concorde did. For example, the Overture engineers are aiming to reduce the noise of both the takeoff and the sonic boom—each of these is to be lower than the Concorde’s values by a factor of 30. At the same time, the plan is for the engines to run exclusively on Sustainable Aviation Fuels (SAFs). The whole thing is calculated such that a ticket should cost no more than a trip today on the same route in business class. After 75 years, the stage is set for a new era of supersonic travel.