Additional factors that led to its demise:
- it was a very loud aircraft, and couldn't go supersonic over populated areas due to sonic booms. This led to significant limitations on viable routes.
- it didn't have the fuel capacity to make trans-pacific flights. This also led to limitations on viable routes.
- Concorde required specialized pilot training, specialized maintenance, and even a flight engineer (which more modern jets don't require).
- supersonic flight wears out airframes. I worked in a museum with Concorde G-BOAG, and could see several spots where the airframe had been patched in more substantial ways than our other similarly-aged or older airliners (Eisenhower's 707-based Air Force One and the prototype 727, 737, and 747's.) Airbus didn't want to keep maintaining the airframes given the condition they were already in.
http://en.wikipedia.org/wiki/Lockheed_L-2000
http://en.wikipedia.org/wiki/Boeing_2707
The Soviets also had a design that supposedly incorporated stolen Concorde blueprints.
From what I understand, the Tu-144 didn't really incorporate anything of significance from Concorde -- the plans they had access to were more like sketches than fully fleshed out blueprints, and they only had usable details on a few minor components. The Tu-144 shares mostly superficial similarities with Concorde, with only a couple of similarities that might possibly have been the result of espionage.
As a rule of thumb, going supersonic triples fuel consumption. There's some research on improving that, and also reducing the sonic boom, but nothing flying yet. The aircraft geometries proposed are exotic. Angled flying wings, aircraft that transition from long/narrow to short/wide, and double inline wings have been considered.
http://www6.miami.edu/acfdlab/projects/AIAA2010-1013_slides_...
http://aero.stanford.edu/reports/vki_kroo_supersonics.pdf
Meanwhile, there's a startup proposing to build a supersonic bizjet.
http://www.aerionsupersonic.com
If you have to ask how much it costs, you can't afford it. It's only Mach 1.4 to Mach 1.6, though. The Concorde cruised just above Mach 2.
Given conventional materials. The SR-71's skin is reported to get harder with all those heating cycles.
Urban transit systems and airport security/boarding procedures will need to get a lot more efficient before supersonic flight will be commercially viable.
(Unless we're talking about Europe; in that case 15 minutes should usually suffice^; at least last time I was there, a few years back. It was great.)
^ Although I'd give it 45 to be safe.
Some materials about a short-lived Hindenburg airship (http://www.retronaut.com/2011/04/inside-the-hindenburg-in-co...) mention its travel time between Europe and North America to be 40+ hours. I wonder, if they were available today, would there be a demand for this type of travel? For me the choice between a seat in 8 hour flight or a comfortable cabin in 40 hour is often not in favour of speed.
I read an article in a magazine sometime back as well, talking about the possibility of luxury flights like London -> New York, but boarding in a nice piece of park land instead of an airport. The flight would be much longer, but there would be essentially no jet lag, much nicer quarters to sleep in, five star restaurant food, etc. It certainly seemed to me there is potentially a niche market there somewhere.
EDIT - all I can find is a DailyMail(!) article - http://www.dailymail.co.uk/home/moslive/article-1357747/Airs...
EDIT 2 - seems to be this company - http://www.hybridairship.net
1 - http://m.ibtimes.com/zeppelins-making-comeback-aeroscraft-ai...
I don't see this happening in the current climate of hysteria.
Checking now, round-trip FRA - JFK on Lufthansa, "First Flex", is $4,500.
If you have the time, freighter travel is a possibility. http://cargoshipvoyages.com/VoyageDetails/?SCID=54&VID=143&S... shows a Europe/US route at $2,300, for 2 weeks at sea.
Airship travel is left with a limited market. It's not fast. It's not cheap.
For businesses that cost would be a no-brainer: landing and being able to actually function, would be amazing.
50 years of commercial airline operations have been hard for niche aircrafts. I'm not bullish on the hopes of a LEO commercial plane in our lifespan. It's a tough equation:
- a LEO plane won't be developed without presales that warrant safe funding (ie. from flagship airlines)
- incumbents are all about kerosene and do not want to add a significantly different tech to their already complex operations.
- new comers will not get access to enough capital to secure the development of a disruptive engine technology
Airlines make cash by moving a diversified mix of people and cargo. I just don't see anyone moving to the (super volatile) premium-only market with a supersonic high fixed cost jet.