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Jack Rupert, PE
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Platinum
Who's to Blame?
Jack Rupert, PE   8/14/2012 4:45:28 PM
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What's getting in the way of speed?  Is it just cost or is it, like usual, government regulation?  Even in its heyday, the Concorde was only allowed to fly at its advertised speed over open ocean.  I think it was "illegal" for them to fly a New York to LA route at those speeds.

Rob Spiegel
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Blogger
West to East in less than an hour
Rob Spiegel   8/14/2012 4:51:22 PM
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Yes, Rich, I also saw that CNN article, andI too was surprised. I was under the (perhaps mistaken) impression that speeds exceeding 600 mph would cause sonic booms that would be unacceptable to residents. And thus, there was a wall against faster speeds. Yet at 4,500 mph, why no sonic booms?

richnass
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Blogger
Re: West to East in less than an hour
richnass   8/14/2012 4:56:38 PM
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I believe you are correct about the sonic booms. They had to be over the ocean before going to hyperspeed. The test run by the Pentagon today was also over the ocean.

Rob Spiegel
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Blogger
Re: West to East in less than an hour
Rob Spiegel   8/14/2012 4:59:49 PM
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OK, that explains a lot. When I read the article -- which didn't address sonic booms -- I wondered whether the small size of the craft negated the sonic booms. Maybe they just take the boom over the ocean and move on.

Rob Spiegel
User Rank
Blogger
Re: West to East in less than an hour
Rob Spiegel   8/14/2012 5:23:12 PM
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Yes, it's the sonic boom that limits air speed over land:

http://www.discovery.com/area/skinnyon/skinnyon.html

Exceeding 660 miles per hour above sea level creates the boom. Once an aircraft breaks the sound barrier, it creats an extended boom that is heard by anyone who is near the supersonic craft. So it isn't just one single boom -- it's continuous as long as the craft is exceeding the the sound barrier, even if those on the ground experience it as a single boom. So, on a flight from L.A. to N.Y that exceeds the sound barrier, everyone on the ground between the two cities would experience the window-shaking (and sometimes window-breaking) boom.

NASA, however, is looking at strategies for taking the boom out of high speed aircraft:

http://www.nasa.gov/connect/chat/sonic_boom_chat.html

NadineJ
User Rank
Platinum
different world today
NadineJ   8/14/2012 5:44:09 PM
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From my understanding, faster speed = high fuel consumption.  During the days of the Concorde, high fuel consumption wasn't seen as a problem.  Today, consumers and the market are more focused on things that, at least, appear to be good for the environment.

Jon Titus
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Blogger
Acceleration?
Jon Titus   8/14/2012 6:42:57 PM
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Perhaps the rapid acceleration would kill the passengers and crew. Not a good way to start a new airline.

notarboca
User Rank
Gold
Re: Acceleration?
notarboca   8/14/2012 10:53:14 PM
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@Jon Titus--I, too, have questions about acceleration.  Would this require pressure suits for passengers, or perhaps some sort of encapsulated seat that would react to the G-forces?

TJ McDermott
User Rank
Blogger
Where is the time wasted?
TJ McDermott   8/15/2012 1:12:36 AM
A transcontinental flight takes about five hours, wheels up to wheels down.  Five hours to go 3000 miles is not too shabby, and there's no shock wave to be of concern.

I am constantly dismayed at the amount of time it takes, when using air travel, that is not actually in the air.

The airlines tell you to arrive 75 to 90 minutes before your departure, and you could spend up to 45 minutes waiting for your luggage at the other end.  Tack on an additional 20 minutes or so taxiing to and from the gate.  Call it 2-3/4 hours going effectively ZERO miles per hour.

Your average speed for your transcontinental flight isn't 600 miles per hour, it's 387, just two thirds the real speed of the plane.

Think about it.  Sure the speed is the same as it was 40 years ago. The passenger loading process hasn't changed one bit for almost a century!  It seems insane to load everyone single file through ONE door!  The time a passenger jet spends on the ground not moving people is wasted revenue to an airline.  An airline should be able to cut the turnaround time by at least 40% if more than one door is used.  Sometimes that's done on jumbos, but it's still from ONE SIDE ONLY!

A widebody has two aisles.  Why not load from both sides of the plane?  And why not load from the rear as well?  A jumbo could effectively be loaded from a four doors on two aisles.

Even a single aisle aircraft could be loaded from front and back.  I've seen a single aisle aircraft unloaded a few times in this manner at the San Jose airport in California (Alaska Air), and that gets the plane empty fast.

Time is money.  Cut the load / unload time, and make millions.

naperlou
User Rank
Blogger
Re: Who's to Blame?
naperlou   8/15/2012 9:09:18 AM
NO RATINGS
Jack, in this case there is a reason for the regulation.  The sonic boom will break windows and cause lots of other problems when flown over land, unless you are at a very high altitude (think SR-71).  The military also has to be careful when doing that.  Frankly, supersonic speed is great for catching up to someone or getting away from someone  (I am thinking military jets).  On the other hand, you can't shoot or turn very tightly at supersonic speed.  For transport it would be great, but the cost is very high.  Those safety and other regulations are important in this case.

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