Having seen Al Gore's movie " An Inconvenient Truth" last week I have turned from a sceptic into a grudging believer, however for the same reasons why aviation was left out of the kyoto accords I do not believe aviation is the place to start cutting CO2 emissions.
Aviation was left out of Kyoto for the very reason that it is the one form of transport which has no immediate and practicable alternative to hydrocarbon emission. What I mean is if we as a society converted just 10% of car emissions and 10% of truck emissions, whether by electric, hydrogen fuel cells, or even biofuels, it would more than offset global aviation emissions.
I would be happy to drive a biofuel powered car. Somebody offer me a fuel pump at my local gas station and I'd do it gladly.
I did hear a scary statistic. When USA's aviation fleet was grounded on Sept 11th there was a perceptable 2% drop in CO2 emissions.
There have been attempts to develop soya oil for gas turbine engines with a Rolls Royce Dart. The engine functioned well. the problem was that the fuel gelled above the -40 Celsius minimum required for FAA certification.
Branson's idea to tow aircraft to the start of a runway seems silly to me for various reasons, but towing an aircraft after a landing to the gate might not be so stupid.
CFM-56 engines have acheived extra fuel efficiency by creating two concentric rings of burner cans. At take off, all the cans are used. In cruise and descent only the inner ring is used. That avoids unnecessary fuel burn and inefficient burning.
Next idea coming is Pratt and Whitney's PW6000 & PW8000 geared fans. These are large LP fans driven by a small core always operating at the same power setting. The shaft will have an equivalent of an automatic gearbox shifting gear to change the LP fan speed.
This will be the jet engine equivalent of a constant speed propellor. Then I guess we could always go back to airships using biofule diesels ?
