By any measure, Concorde was a remarkable aircraft. Ahead of its time when it first took to the skies in 1969, it was sleek, graceful and extremely fast. It was also notoriously noisy, a drawback that halted the evolution of supersonic commercial aircraft in its tracks. Until now. The Japan Aerospace Exploration Agency is working on the design of a next-generation supersonic commercial aircraft that is expected to produce a sonic shock wave 75 per cent smaller - and therefore quieter - than the one produced by Concorde. That would theoretically permit this new aircraft to be operated on overland routes without disturbing the sleep of people on the ground. The D-Send project - the full name is Drop test for Simplified Evaluation of Non-symmetrically Distributed sonic boom - dates back to 2006, but scientists working on the programme have now progressed to releasing scale models of the future aircraft to confirm that the low sonic boom design actually works. The most recent drop test was conducted at the Esrange Space Centre in Sweden in July 2015, with the Silent SuperSonic Concept Model lifted into the sky suspended by a hot air balloon. The aircraft was released at an altitude of 30.5km and guided remotely to pass over measurement equipment. Travelling at a speed of Mach 1.39, the 7.9-metre-long aircraft created 32 per cent less pressure than a Concorde model of the same size. And that, said Kenji Yoshida, principal researcher in JAXA’s Aeronautical Technology Directorate, is a major achievement. “The test was a world first flight in which a low-boom concept demonstrator, that is one tailored to reduce nose and tail sonic boom, was successfully flown while maintaining the stability of aircraft,” Yoshida told the South China Morning Post. “We have learned a lot from the flight tests, in particular the difficulties in developing an actual aircraft and making it fly. I’m relieved to have achieved the goal of the D-Send project.” An object that moves faster than the speed of sound compresses the air in front of it, creating an area of high pressure that spreads out as a shock wave that can be heard as an explosion. Concorde’s shock wave is intensified by its trademark swept wings, which cause significantly greater air compression than the slender nose and make the boom louder. Also, the opposite process takes part at the tail of the aircraft when it vacates air space, with air rushing back in to fill the void and create another boom. And while entirely eliminating the boom caused by a supersonic aircraft is impossible, JAXA is reducing the scale of the waves by designing a nose that is flat and rounded and therefore creates more powerful shock waves that travel fast enough to stay ahead of the waves caused by the wings. By avoiding merging, the boom is significantly reduced. Similarly, the tail is engineered to decompress the air and create shock waves that then cancel out the waves that have been generated at the nose of the aircraft. The lessons JAXA has learned are now protected by two patents on the low-boom design concept. Yet there are plenty more hurdles to be overcome, Yoshida said. “The next-generation supersonic transport designed by JAXA would be a relatively small aeroplane with a capacity of around 50 passengers,” he said. “It would be flown no sooner than 2030. “Through the success of the D-Send project, we have managed to devise a key technology for reducing sonic boom, but there are lots more technical obstacles to be overcome.” Nevertheless, the plan is to have a 70-ton, Mach 1.6 aircraft that will link Tokyo and Singapore in a little over three hours by 2030. And Yoshida acknowledges the debt that his team of scientists owes to their predecessors on the Concorde, which cut the flight time from London to New York to 3 hours and 45 minutes and could hit Mach 2.04 - a breathtaking 1,354 mph. “Concorde was built with the cutting-edge technologies of the time, which provided me with lots of inspiration,” said Yoshida. “I have a great deal of respect for the engineers who designed and built an entire supersonic aircraft system with such intensive efforts. “What we should learn from Concorde is the importance of taking a balanced approach to designing this aircraft, taking into account today’s technologies, markets and environmental and social climates,” he added.