[lyner]

Should we have a forum titled "Usage"?
We could really stretch our grumpy old pedant muscles there. (I'd be second in the queue)

[Chemistry4me]

Whose going to be first?

[DoctorBeaver]

ME!

[survivalist13]

I have also thought about this subject and with a little research the best answer seems to be the Lapcat A2, already mentioned (http://www.reactionengines.co.uk/lapcat.html [nofollow]). In short, it is a concept plane which could fly at mack 5 (5 times the speed of sound, over twice as fast as Concorde), it would have to be really big (to make it economical and fly really high up, 25Km. The project is 50% EU funded but is very expensive at €22,600 million. However estimations of ticket prices are relatively low (about the normal price of business class). The reason for all of these amazing figures is the scimitar engines. They are hydrogen fueled, so potentially zero carbon emissions. Hydrogen is one of the lightest fuels which is an obvious advantage, furthermore the liquid hydrogen used means the engines can be substantially more efficient. It is the temperature which is crucial. This is because the engine can be lighter because it doesn't have to withstand so much heat and the low temperature can be used to cool the air down, meaning more power (like an intercooler, the air becomes more dense). The engines also have the ability to run as a turbo prop to cut down on noise pollution when landing and taking off.

All in all this seems amazing and what's more the company is British.