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.
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.
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.
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."
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.
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:
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.
More anecdotes, but, I lived 1 1/2 miles perpendicular to the most frequent runway of an airport. If you were outside, you could hear every plane take off and it disturbed an otherwise perfect place to live. However, with zero noise considerations in building, couldn't hear a thing inside. On the other hand, I now live within 2 miles of a medium sized metro area and the normal sound of traffic is louder than the planes were. So while I never took db readings, environment is going to play a huge impact, but even minimal insulation will make it inaudible.
Indeed - a sudden boom is more disturbing than a rumble.
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.
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.
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?
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?
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.
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.
>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.
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.
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".
