NASA Claims Supersonic Breakthrough For Biz Jets(aviationweek.com) |
NASA Claims Supersonic Breakthrough For Biz Jets(aviationweek.com) |
(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)
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...
Still, living at one end of Canada and having friends at the other end, I'm excited for the possibility quiet overland supersonic flight.
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."
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.
This has a small image of a test vehicle: http://www.nasa.gov/missions/research/sonic_booms.html
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?
Why mutually exclusive? (just curious) What was the justification previously offered?
But those big, single shock waves are, of course, perceived by the listener as a "boom".
Really? I would expect it to be relaated to size and shape.
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.
Leaving aside that that's a terrible reason to stop even trying to predict something, I haven't found this to be the case at all.
Since about 2000 the date that's been put out was 2004-2006. The recession did indeed delay that a couple years, but we've still never extracted more oil than we did in 2008 despite continued high prices (vs. say the 1979 peak, after which oil prices collapsed).
>Every time we seem to run out of oil or natural gas we find more - known oil reserves have never been higher.
Helped in part by the fact that the OPEC nations (which account for ~80% of those reserves) allocates daily production limits in proportion to known reserves. So the more oil you claim to have, the more oil they let you produce! When the rules changed in the 1980 there was a gold rush of "revisions" that increased global oil reserves by 33%.
Peak oil is not "running out of oil," so the fact that that hasn't happened is not a real argument.
If you honestly believe that a global economy in which oil production has been flat for 4 years despite high prices, in which only 14 of the 54 oil-producing nations are growing production, in which another 30 are in active decline–forcing them to import more oil and more every year just to maintain current consumption (let alone fuel growth)–is a global economy in which peak oil isn't taking place, then I honestly don't know what to say.
http://atwonline.com/eco-aviation/news/ten-airlines-agree-pu...
http://motherjones.com/environment/2008/01/virgin-airlines-p...
Still, if it can be made quiet enough not to scare people, it could be inspiring. You hear a bang in time see a man-made object traveling above Mach 2.
Or 3, 4, 5...
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/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.
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.