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Okay, so it's not useful for fighter jets to get any faster. But it sure as heck is useful for my airliner to get faster.

1. I suspect it's engineering, simply because there are few cases in which economic reasons, outside path dependency, cripple our use of available technology in an existing market.
2. Singularity believers seem to also believe in exponential technological growth. How true is this belief? (Not among nations as a whole, but growth in the total available technology, i.e. in America/Japan/Europe.)

Presumably we won't have commercial supersonic planes until we develop a much cheaper/more efficient/lighter power source for them.

there's an excellent discussion on ( on what are the constraints to faster airliners. The focus is on the fact that the speed of sound is a formidable physical barrier to surmount, and that simply more powerful power plants or cheaper fuel are not the primary constraints. The sonic boom over populated areas is an engineering challenge we have yet to even begin to overcome.

One thing to consider is the impact of pollution, of vehicles like Concorde. It's one of the reasons I am quite skeptical of Richard Branson's space tourism project. It seems like a massive carbon and pollution footprint for essentially pure leisure purposes, and something difficult to swallow by a third worlders like me, being asked by wealthy hyper-prolific polluters of the world to sacrifice my development curve for our shared future.

At a certain Mach number (I don't remember exactly, but it's in the low hypersonic range, probably 5-7), there is no point in going any faster for commercial terrestrial travel, because even a London - Tokyo journey, you'd have to spend half the journey accelerating and then the other half decelerating without ever reaching your maximum speed. NASA has broken some speed records in recent years-- notably, the X-43A, which broke Mach 9 in 2004.

Well, you can get from anywhere to anywhere else on the earth in just 45 minutes if you dig a straight tunnel between the two points, pump out all the air and line it with a frictionless material...

ohwilleke - respectfully disagree with point number one, except for distances of less than 300 miles. One place I frequently fly to is 350 road miles away but 50 jet minutes away. Even with 1 1/2 hours from office to airplane and 1/2 hour from airplane to destination, I save at least 3 hours in each direction compared to driving. I can easily fly there for a meeting in the morning and be back in my office in the afternoon. Driving, it would be a two day trip.

Longer trips increase the advantage of flying. But they are still very long - I do not enjoy 6 or 8 or 10 hour plane rides. Anyway, speed is indeed a big deal.

Ak Mike: Obviously, planes are not always slower than cars. But, the waste time that goes into getting onto and off a plane has a very large effect on the benefits of plane speed and the economic choices that make sense to impact trip time.

Let's look at your flight. It is five hours each way by car, give or take. It is 2 hours and 50 minutes each way by plane. Suppose that you have a supersonic plane. Your trip would be 2 hours and 25 minutes. If one has the will to improve the system, it is easier to cut 25 minutes out of 90 minutes of pre-flight time (perhaps with a frequent flier express pass system, or a high speed rail line from downtown to the airport, or a chartered air taxi) than it is to invest in supersonic planes. And, when the marginal benefit of a supersonic plane is 25 minutes, and supersonic planes typically fly less often, because there is less of a demand for them, the benefit may be negligable.

For very long trips, for example, a direct flight from Los Angeles to Tokoyo, the time savings from a faster flight do start to look material, and the small amount of time spent overland makes the sonic boom problem that plagued the Concorde (and its Russian counterpart) far less serious.

But, the fact that the Concorde failed commercially on routes from New York to London and Paris, and the timidity of pressure on the TSA and airlines to speed up boarding processes, suggest that the economic need for high speed commercial plane travel is not very great. The barrier that sonic boom issues place on long overland trips like New York to Los Angeles, also puts real limits on the scale of investment that it makes sense to put into faster jet transportation. Is the market so big that it can afford to invest a new and more expensive than usual to develop plane for a small part of the traffic on a tiny number of routes?

My view is that we need to improve technologies for getting people from the front door of the airport to the tarmac before anyone, public or private, invests money in supersonic jet planes. A 50% savings in boarding time on your trip is equivalent to building a Mach 3 plane to take you there, and might cost little or nothing to implement.

What about the need to transport military personnel quickly, where very high costs to get someone to the scene are acceptable? Supersonic military personnel transports are proposed every few years like clockwork.

Even then, it is almost certainly cheaper to have fast, but not supersonic speed transports in a dozen or so locations around the globe, and to deal with the need for speed by having key personnel based in a dispersed way, reducing trip size, rather than making a very fast vehicle. Very few jobs are both irreplacable and require a personal physical presence. While the pitches for these vehicles inevitably involve highly trained commandos, people with those skills simply aren't so rare than you can't have them in a dozen locations and one rarely has a compelling need to have them in some non-military setting. If one did need to get someone irreplacable to the scene in a hurry, that person would probably be an elite specialist surgeon or a hand's on repairman for high tech equipment. In these rare cases, simply having that person sit in a co-pilot's seat in a jet fighter might be the most sensible solution.

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