Sonic booms happen in the trail of a jet airplane breaking the sound barrier, at around 1200 kilometers an hour. The noise often provokes complaints, and when it was in service there were many protests and lawsuits aimed at the supersonic passenger plane Concorde because of the sonic booms it caused,
Now the Japanese Aerospace Exploration Agency Jaxa is working to reduce the noise caused by aircraft breaking the sound barrier, and they’re carrying out their experiments in Esrange, the Swedish space base outside Kiruna above the Arctic Circle.
Mikael Töyrä is the project manager for the program from the Swedish Space Corporation. He tells Swedish Radio P4 Norrbotten that Jaxa is developing a concept to develop quieter passenger planes that can fly faster than the speed of sound. He points out that Concorde was not allowed to fly faster than sound over land because it was too noisy.
The two eight meter long pilotless test drones are in a hangar at Esrange. The project manager from Jaxa, Masahisa Honda, says they’ve used advanced computers to design the new planes, which he says has halved the noise from the faster-than-sound shockwave.
So why come all the way to northern Sweden to carry out the tests? Masahisa Honda says it was for the wide open spaces available here.
The tests involve large helium balloons which will carry the drones up to an altitude of 30 kilometers, where they will be released. Not only do they not have pilots, they don’t have engines. The fall from the stratosphere will push them to supersonic speeds. The sound measuring equipment, as Mikael Töyrä explains, is also in the sky.
"There are three measuring stations hanging from blimps," he says, " with microphones at altitudes of 750, 500, and 250 meters. There are also microphones on the ground. Together they will measure the strength of the sonic shockwave and how it spreads in the air."