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More On Silent Supersonic Planes
Reverberant writes "Popular Science describes the latest attempt at developing a supersonic plane designed to minimize sonic booms. The article describes some of the history behind the research, and recent attempts at validating the theory. Also note that researcher Ken Plotkin is a frequent contributer to alt.sci.physics.acoustics."
It's just you being paranoid.
A modern airliner with all the latest gadgets (GPS, EFIS, ILS) can be flown without any sort of external vision at all. Heck, the modern autopilots can take off, fly to the destination, fly the approach, and do all but about the last 50ft onto the runway.
TODO: Something witty here...
...can be found here.
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The word you are probably looking for is declension. Conjugation refers to verbs.
My company's UK office is very close to the flight paths into and out of Heathrow. Work comes to a stop when the Concord flies anywhere near on take off. No one notices the other commercial jets. I didn't notice it until last summer. Most of my time in the UK office was spent while those beasties were grounded. It was quite noticible when they were allowed back in the air.
the growth in cynicism and rebellion has not been without cause
A sonic boom can also be detected at many miles distance by a wired or radio connected listening device, analyzed in a few seconds to get a fairly good idea of what sort of plane emitted it, and that information sent to the potential target, or interceptor forces, at the speed of light or close to it, long before the plane can cross the terrain to get to its target. The Soviet Union was deploying such systems in the early 1960s, and it's a fair bet that even some "third world" countries have their own variants on them today.
Who is John Cabal?
The earliest subway cars had no windows either, since there was nothing worthwhile to see. Windows were added later since they made people more at ease and helped with claustrophobia, even if what is outside isn't that pretty.
Even those who arrange and design shrubberies are under considerable economic stress at this period in history.
a sonic "boom" isn't a one time event. The shockwave is continuous, so long as the aircraft is flying at supersonic speeds. Therefore, people on the ground for the entire flight corridor will hear/feel the boom as the plane flies overhead.
In fact, no kidding the people at the airport the plane lands at dont hear a boom! Obviously, the plane slows down to subsonic speeds prior to landing. But for everyone in between the takeoff and landing airport that the plane flies over, will be subjected to it.
Hence the reason the concorde was banned from flying over the US, but landing on coastal airports isnt a big deal.
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Here's an F-14 creating a sonic boom overhead in some type of airshow.
. mpg
http://users.wpi.edu/~jbendor/F-14%20Sonic%20Boom
I can't find any news article about it any more
The incident occurred on June 17. There's a brief reference to it here.
Generally, the military restricts supersonic speed over land to altitudes above 30,000 feet to limit the intensity of the sonic boom. It is probably a measure of the urgency of that mission that the F-16s broke the sound barrier so soon after take off.
Newsflash: PM is not a scientific or engineering magazine, it's basically the nerdy guy/Redneck mechanic version of supermarket tabloids like News Of The World, or the Star. Try looking at some back issues and you'll figure out pretty soon that this rag is just recycling the same badly written, factually wrong and unrepentantly gush-y articles every year. (Oh, it's June--let's do the supersonic plane again. July--the Navy's next generation invisible war ship. November--flying cars are back in season.)
I've heard rumors that PM was once a serious and useful publication, but that must have been more than 15 years ago. Nowadays, it's crappy reviews, braindead and inaccurate futurology, and 50 Jackass-approved ways of using WD 50.correct, but the Concorde didn't ordinarily use afterburners; it had them only for the greater thrust demands at take-off and during acceleration, not for cruise. it was an expensive plane to run largely because of its low seating capacity and short range, which barred it from many of the lucrative trans-Pacific routes.
(some have also argued that the low-to-nil bypass ratio of the Concorde's Olympus engines made it more expensive to run. that may be true; i don't have any really convincing evidence either way.)
that would have had to depend on what the plane was doing. during landing, i can well believe the difference might have been small; during take-off (under afterburners, natch!) that would very much surprise me; and while supersonic, absolutely not.
Concordes were politically acceptable so long as they stayed subsonic over land, so nobody would complain about the boom. they were also hideously expensive to run, which in a more rational world might have shut them down all by itself, but apparently there were enough eccentric ultra-rich people to keep them flying for decades in spite of that fault. no amount of money, however, would let them reamin at their designed cruise speed above anyplace people lived, and that was as much a political shortcoming as a technical one.
As a pilot, it is my responsibility to see-and-avoid other traffic during my entire flight. But it becomes the controller's responsibility to maintain seperation in controlled airspace.
I'm a low time pilot, but I can tell you that most of the time in controlled airspace, the controllers do their job well. The problem is on the weekends at uncontrolled airports...
FAA Certified Flight Instructor
...is nothing new. The Tridents, BAC 1-11s and VC10s (all British!) of the early 1960s had it. Don't try and pretend Boeing invented everything - they are the Microsoft of the skies - not much invented here....
The review by N. Geffen of "Analysis of Transonic Airfoils", Comm. Pure Appl. Math. 24 (1971), 841--851 by Garabedian, P. R.; Korn, D. G.
"Calculation of inviscid, subsonic-supercritical flow around prescribed airfoils is described. This supplements the authors' previous design of a shockless transonic wing using real and complex characteristics in the hodograph plane. The flow about the designed wing is calculated for a range of off-design conditions.
"Neumann's problem for the flow-potential equation is solved numerically in a plane where the exterior of the airfoil is conformally (also numerically) mapped onto the interior of the unit circle. Following E. M. Murman and J. D. Cole [AIAA J. 9 (1971), 114--121], a second-order finite-difference scheme is used in the subsonic region, while an implicit second-order scheme is used in the hyperbolic zone, introducing artificial viscosity of the right sign. The Kutta condition is satisfied by an iterative scheme. Results with relatively narrow shocks (i.e., steep gradients) are given and compared with wind-tunnel experiments."
PM was once a serious and useful publication, but that must have been more than 15 years ago.
Way more than that. As early as the late 60's (the oldest issues in my memory) PS was pretty much a gee-whiz magazine not intended for actual practitioners of science or engineering. But if you look at pre-WWII reprints, it has the flavor of a trade rag, with actual practical knowlege for projects (homebuilt radio sets were common, I think this was before a separate Popular Electronics) The premiere ussue was in the 19-teens I think, and has a newsletter appearance to it. I think one of the feature articles was on telegraph sets.
I disagree--laser tech can pinpoint the distance to within a centimeter or less with ease. I would think it possible for the instruments to be much more accurate than a pilot who can't even see his landing gear as far as the distance from wheel to ground (which is the important figure).
Sorry, but instruments can be much more accurate--but I would still want a window--despite how irrational it is!
"We don't know what we are doing, but we are doing it very carefully,..." Wherry, R.J. Personnel Psychology (1995)
" loved Beyond 2000! What ever happened to that show and why don't they bring it back."
Maybe because it is already beyond 2000... They would have to rename the show Beyond 2010 or something...
"The english accents and the just-over-the-horizon tech was great stuff!"
Beyond 2000 was an Australian show, with Aussie presenters. Maybe you can't tell the difference between an Aussie accent and an english one, but they are quite different.
It is a matter of what is making the "boom" and how far off it is. As another poster notes, the crack of a whip is a tiny sonic "boom." The kind caused by jets vary in intensity depending on distance. From a distance of a mile or more they sound like thunder, which oin a sense is a sonic boom as well. The sound is caused by the abrupt displacement of surrounding air by intensely heated air along the course of the lightening. Close up they can be painful and structurally damaging. I think the Israelis made low-level (near roof-top) supersonic passes over Cairo during one of the Arab-Israeli conflicts.
------ The only greater hazard to your liberty than n politicians is n+1 politicians.
The Concorde was profitable on an operating basis (or so BA/Air France claimed), but it never recovered its development costs. The economic case for SST's doesn't look promising though. In the 1960's, jets supplanted piston-driven aircraft because, even though they costed much more, they flew much faster and required less maintenence so they returned more passenger miles in a day. Jets burn more fuel, but jet fuel is cheaper than aviation gas. An SST burns more of the same type of fuel and turn-around time on the ground limits how much you gain in utilization rate. To be profitable, an SST must command a Concorde-sized ticket price. Now if somebody figures out how to make a fuel-efficient SST, then the cost goes down and trans-pacific (and trans-asian if you solve the sonic boom) flights become possible, allowing the aircraft to spend a greater fraction of the time in the air making money.