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JAXA Successfully Tests Its D-SEND Low-Noise Supersonic Aircraft
AmiMoJo writes: JAXA, the Japanese space agency, has successfully tested its low sonic boom demonstration aircraft D-SEND#2. The unmanned aircraft is floated up to 30,000m by balloon and released, falling back to earth and breaking the sound barrier in the process. The sonic boom created is measured on the ground. The project aims to halve the noise created by sonic booms, paving the way for future supersonic aircraft.
It's similar to how they developed their high speed trains. The government did the basic research and development, and then it grew into a huge business where Japan lead the world for over 50 years.
Interestingly that's the exact opposite to the way the UK works. You see we put in all the risky research money to develop tilting trains. Then because "reasons"[1] it was shut down and sold off and we're now buying tilting trains from Pendolino (a foreign company which bought the rights cheap) at great expense. The original tilting train still holds the speed record on the relevant routes.
Which is a better investment, I shall leave as an exercise to the reader.
[1]The reasons were bogus. Some people claimed it made people feel ill. There was an early problem because the tilting compensation was too good. Dialling it back a bit solved the problem and the trains became no worse than the modern ones in that regard. Basically the reason is that no matter who is in power, parliament hates local industry for some reason.
SJW n. One who posts facts.
i.e. a 6 dB reduction in overall Sound Pressure Level. Just enough to be noticeable, but not really a huge change.
The real issue is that no one has reliably determined what noise levels are "acceptable" for sonic booms. A lot of recent work by NASA and JAXA has focused on which types of noise metrics correlate best with annoyance (in short, Perceived Noise Level seems to do about as well as anything), but it's the politicians who have to decide what levels are allowable for overland flight. For that, you have to identify their constituents that care. Quite honestly, the big boys in the aviation industry aren't that interested in supersonic flight--few will pay much more for their airplane ticket to save a few minutes of flight time, especially with so much extra time now spent in security. In fact, airliners have slowed down in recent years to save fuel and lower ticket prices. The guys pushing for a rules change are the business jet manufacturers, like Gulfstream, who do have customers who care about speed (and can skip the lines at the airports). How much noise are people in "flyover country" willing to accept so that rich CEOs can get from NY to LA an hour sooner?