

NASA Claims Supersonic Breakthrough For Biz Jets - yairharel
http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=busav&id=news/avd/2012/04/02/08.xml&headline=NASA%20Claims%20Supersonic%20Breakthrough%20For%20Biz%20Jets

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v3rt
If a big proportion of business-travel-miles are flown over oceans (which
seems reasonable between the most common routes like New York-London, SF-
Tokyo, SF-HK...), would it not be cost and time efficient to use low-drag but
noisy planes and just hit the speed of sound over the ocean? Flying .9 Mach
over the land and 1.5 (or whatever was reasonable) would still save a lot of
time and wouldn't disturb anyone.

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stretchwithme
And that's what they were doing before the demise of the Concorde.

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lysol
Don't editorialize the headline. The article is much more nuanced than the
headline suggests and it belittles an amazing achievement.

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marklabedz
Agree with your analysis, but OP used the original title from Aviation Week.

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_delirium
It's been edited; the original submission was "The end of the sonic boom is in
sight". Though actually that doesn't seem that inaccurate; the "supersonic
breakthrough" discussed in the article is precisely the effective reduction of
sonic booms.

(Incidentally, Twitter is a good source for finding what titles were before
they were edited. In this case I found it at
<https://twitter.com/#!/newsyc20/status/187650762111844353>)

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ChuckMcM
Perhaps we'll officially acknowledge the existence of the Aurora :-).

There has been great progress in the open literature about developing super-
sonic craft which mitigate and possibly eliminate the 'boom' effects. The MIT
paper [1] was worth a read as well.

[1] [http://web.mit.edu/newsoffice/2012/supersonic-
biplane-0319.h...](http://web.mit.edu/newsoffice/2012/supersonic-
biplane-0319.html)

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CountHackulus
At 70PNLdB, I doubt anyone in their car could hear it. In fact pretty much
only rural quiet areas will hear it. Though I'm sure there's going to be some
"concerned citizens" that claim that the sonic booms are causing their
children migraines, or something similar.

Still, living at one end of Canada and having friends at the other end, I'm
excited for the possibility quiet overland supersonic flight.

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Anechoic
_At 70PNLdB, I doubt anyone in their car could hear it. In fact pretty much
only rural quiet areas will hear it._

70 PNL dB is fairly loud, it will be very noticeable in urban areas and
_extremely_ disruptive in rural areas. 65 dB Ldn is the target for normal
aircraft and most experts agree that limit is way too high.

The research represents a significant decrease in noise from supersonic
aircraft, but we're a long way from "quiet."

~~~
CountHackulus
Got any sources for that? I'm interested in reading that research.

Couple anecdotes: I work in a semi rural neighborhood that's 2km from a
regional airport (a bit off to the side of the approach path). I work right
next to a window and haven't once heard an airplane go by. Now, this might be
due to our shielded glass and white noise generators in the ceiling, but
that's not bad.

Second anecdote, there was an airport downtown on the water that was re-
opening with an airline running Bombardier Q400s (Porter Airlines at Billy
Bishop). There was a group of protesters that were claiming that the noise
would ruin the quiet of a nearby spit. So on the launch day, before the sun
rose, they gathered at the spit to protest. Unfortunately for them, they
missed the first flight as their talking had drowned it out.

Maybe it's just because I lived next to the railroad tracks for 20 years, but
I say, bring on the jets.

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Anechoic
_Got any sources for that? I'm interested in reading that research._

Nothing specific off hand, I used to work for a firm that did aviation noise
analysis and this was something I heard a lot from colleagues at the firm and
other firms. A starting point might be a couple of presentations from that
firm that don't discuss the appropriatness of 65 Ldn directly, but discuss how
that criterion is not always adequate:

<http://www.hmmh.com/cmsdocuments/UCD_Mar07_Eagan.pdf>

[http://www.hmmh.com/cmsdocuments/DNL_History_Eagan_FAA_NER20...](http://www.hmmh.com/cmsdocuments/DNL_History_Eagan_FAA_NER2010.pdf)

<http://www.hmmh.com/cmsdocuments/Eagan_Beyond_DNL65.pdf>

 _I work in a semi rural neighborhood that's 2km from a regional airport (a
bit off to the side of the approach path)._

Approaches generally speaking tend to be much quieter than departures. What
airport? Depending on a bunch of factors (noise abatement procedures,
prevailing winds, approach tracks, fleet mix, etc) it's entirely possible it
might not be loud where you are, vs another location. It's also possible that
you're less sensitive to the noise because that you are working rather than
trying to sleep (and also due to possible sound insulation measures as
indicated).

 _Second anecdote, there was an airport downtown on the water [..] So on the
launch day, before the sun rose,_

Key word being "water"and "before the sun rose" - depending on temperature
gradients (which tend to occur near sunrise and sunset) and wind direction
sound propagation over water can have very unusual effects. In particular, if
air temperatures high up in the atmosphere are cooler than air temperatures
just above the water, sound waves can "bend" upwards to that folks on the
ground will experience lower SPL's compared to what they might hear when the
air temperature is more homogeneous.

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fasteddie31003
I assume the reduction in sonic boom is a result of the shape of the aircraft.
Does anyone have any ideas on what these new shapes could look like? Links?

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b_emery
Maybe these? [http://www.wired.com/autopia/2010/07/aerospace-giants-
design...](http://www.wired.com/autopia/2010/07/aerospace-giants-design-
supersonic-jets-with-a-silent-boom/)

This has a small image of a test vehicle:
<http://www.nasa.gov/missions/research/sonic_booms.html>

~~~
fasteddie31003
I really want planes to look like the ones in the Wired article.

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swalsh
The jets are aimed to become available around 2025.

On a some what unrelated note, does anyone here know what the evolution of
commercial planes is in terms of fuel sources?

Sources i've seen put non-traditional peak oil at 2030, so it would seem that
by the time this technology is developed the fuel could be prohibitively
expensive. Will alternative energies provide enough power for super sonic
flight?

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ars
There isn't any difference between plane fuel sources vs cars or power plants.

In other words there is no change you can make to the plane. The only change
is to the fuel source and that applies to everything, not just planes.

And don't try to predict peak oil - every single prediction ever made of it
has been wrong. And not just a little bit wrong, wildly incorrect.

Every time we seem to run out of oil or natural gas we find more - known oil
reserves have never been higher.

~~~
mikeash
There's a huge difference between planes and these others. Power plants can
run on a huge variety of other sources, like wind, solar, hydro, or nuclear.
Cars can fairly reasonably run on electricity. Airliners as we know them must
use some kind of high-density liquid fuel.

~~~
cwmccarthy
It sounds like ars was trying to suggest that the fuel we currently use is
very similar to that aircraft use (ie. if you can synthesize oil you kill two
birds with one stone)

The cetane number and the flash point is a little different, but to simplify,
diesel is Jet-A with additives, mainly for lubrication. You can put jet fuel
in a diesel truck and it'll work fine, the military often mixes it in to avoid
two separate fuel supplies. The same thing can be done with piston aircraft
(100LL vs auto gas)

Also, I can only imagine the use of a biomass mix will increase. Last year the
USAF was saying it was roughly 10x the cost, but that's dropping with
production scale while oil obviously is only going up.

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Florin_Andrei
> _it is possible to design configurations that combine low sonic boom with
> low cruise drag, characteristics once thought to be mutually exclusive_

Why mutually exclusive? (just curious) What was the justification previously
offered?

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ajross
One possibility is that static analysis for supersonic waveforms is a whole
lot easier if you have planar shock fronts (i.e. the shock waves coming off
the airframe make simple polygonal shapes). Back when this was done with
pencil and paper it was really the only option short of building and testing
real objects, so if you wanted to do any sort of optimization you had to do it
with airframes that produced big planar shocks.

But those big, single shock waves are, of course, perceived by the listener as
a "boom".

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grannyg00se
"Boom is proportional to weight, and a small supersonic business is likely to
meet that level"

Really? I would expect it to be relaated to size and shape.

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icegreentea
Well, it's proportional to volume of displaced air, which should scale more or
less linearly with the empty weight of an airplane.

