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.

Less boom

[invictusvoyd]

My window pane is so happy to hear that .

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[invictusvoyd]

Anonymous coward

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[invictusvoyd]

Anonymous idiot

Hmmmmmmm

[NoNonAlphaCharsHere]

Ya know, I'll bet that if we didn't have so many science haters and pork barrelers in Congress playing games with the budget, that the National Aeronautics and Space Administration could do similar research.

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[thinkwaitfast]

They do and there was a demonstration of this about ten years ago.

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[Gravis Zero]

Ya know, I'll bet that if we didn't have so many science haters and pork barrelers in Congress playing games with the budget, that the National Aeronautics and Space Administration could do similar research.

do you really think NASA should be wasting any brainpower on this corporate horseshit? if companies want to make supersonic jets quiet, let them do/pay for the research. frankly, i would prefer NASA stay on the task of helping humanity, not corporations.

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[NoNonAlphaCharsHere]

I'm just gonna take your sig at face value.

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[AmiMoJo]

Actually this is exactly the kind of research governments should be doing. Stuff that is commercially risky but could have massive pay-offs. If Japan can build a reasonably quiet and efficient supersonic passenger jet they could really boost their aircraft industry. Currently they focus on smaller regional jets, but this could be a big new opportunity.

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

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[serviscope_minor]

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.

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[MoarSauce123]

Parliaments pay attention to those who write the biggest checks. Research labs rarely do that unless they are convinced that their 'research' will gain a lot of commercial success and they just need the tax payer for initial funding rather than go through the trouble of seeking private investment.

Less noise

[rossdee]

"falling back to earth and breaking the sound barrier in the process."

So it wasn't powered by a jet engine, meaning less noise to begin with.

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[Gravis Zero]

"falling back to earth and breaking the sound barrier in the process."

So it wasn't powered by a jet engine, meaning less noise to begin with.

the point is to reduce the sound from a sonic boom, not the engine, genius.

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[wonkey_monkey]

Yeees. And?

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[Anonymous Coward]

Of course, Mr. Coward! You should write those dumb fucks at JAXA explaining their glaring mistake in simple terms. Don't forget to attach your contact information since they'll need you to step in after they're done smacking their foreheads and resigning in shame.

Sonic Booms

[Trax3001BBS]

With my Dad in the Air Force sonic booms were common place, the SST (Super Sonic Transport) battle made them stop entirely (only certain situations are they allowed anymore). It's rare to hear them anymore. I've even a story that shows one can even be accused of firing a weapon when one happens, people just aren't used to them, or never heard one before.

Wow

[rsilvergun]

And with those robot arms he'll be able to go even faster! (looks) Oh, _JAXA_. Drat. Well then. Carry on I suppose.

Measured how?

[ChrisMaple]

Halving the noise is not a scientific description. Half the noise power? Half the peak pressure? Half the average pressure? Half the perceived noise?

Half the noise power (3 dB) is so small a difference that an untrained listener couldn't reliably tell the difference between tests performed a day apart.

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[arielCo]

It's in TFA (2nd link). The peak positive pressure of the N-shaped waveform was reduced to less than half and the peak underpressure to about 2/3 compared to a conventional cone.

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[PhloppyPhallus]

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

Terminated

[rh2600]

TFA mentions that the craft was successfully terminated after the test, which I assume means it was somehow destroyed in-flight or directed to the ground/sea in a fatal fashion.

It's incidents like these that we will regret when SKYNET finally rises and calls us to account.