The Natural Philosopher wrote:
On Fri, 06 Jan 2006 19:05:11 +0000, Steve Firth wrote:

The Natural Philosopher wrote:
On 04 Jan 2006 14:41:11 GMT, Adrian wrote:

Doctor Drivel ) gurgled happily, sounding much like
they were saying :

As 90% plus of us live in towns and cities our lungs matter.
Doesn't "North London" count as a "town or city", then?

Because you've already claimed that pollution from an industrial accident
arising from the generation/transmission/storage of energy for
transportation will drift over North London.

The fact that Buncefield's fire was primarily aviation fuel seems to have
slipped you by, too.

Or will your utopia have electric planes, too?
I already fly them :-)

However no, energy density is not and will never be enough for commercial
planes...those will lilely be repalced by high speed trains for overland
routes, and by biofuel or hydrogen for intercontinental flight.
[snip]

If hydrogen were to be used for commercial flight, the body of the jet
would have to be the fuel tank and the number of passengers carried
would be the limited to whoever could crowd into the back of the cockpit
and the lavatory.

http://xtronics.com/reference/energy_density.htm

Looks like liquid hydrogen is about one third the weight of equivalent
kerosene...

Correct, it's also incredibly leaky and boils off from the tank very
quickly. Even the best insulation available will not stop it from
boiling off. This is why they fuel at the last possible moment.

guess thats why they power raockets with hydrogen, and not
diesel..

Bzzt, wrong: http://www.astronautix.com/props/loxosene.htm

....as far as volume goes, at 150 bar liquid hydrogen is bulky.

Umm you cannot liquefy hydrogen by pressurising to as little as 150bar,
think again. If you could liquefy hydrogen that easily then storage
wouldn't be the problem that it currently is.

20 times as bulky as kerosene.

Which means that storage is going to be one **** of a problem, as I
pointed out previously. To store that much hydrogen is going to take a
tank about the size of a current

However weight is ultimately what limits flight performance, not bulk. Sure
the plane would be different, but it wouldn't be impossible. There are
planes on drawimng boards of a lifting body/flying wing shape that by
integrateting body and wing achieve a very good lift to drag ratio and
hugely increased internal volumes.

yawn

Yes, at this point I should perhaps highlight that my address was once
c/o RAE Farnborough. Flying wings have been on the drawing board for
decades, and that's mostly where they tend to stay. The last time I
saw/heard mention of one, it was beign considered by an aircraft
designer I have considerable respect for (Hi McP if you're reading this,
or if PC Paul contacts you). He discarded the idea as well, because it
all falls apart once you get into embarking and disembarking passengers,
housing landing gear and engines and designing control surfaces. Also
the "huge internal volume" tends to be in a form that's largely
unusable. Unless you are going to insist that the passengers are
strapped horizontal all the way to the USA.

Planes to date have not actually been particularly optimised for fuel
efficiency alone: Other factors like serviceability, and overall cost of
running - of which maintenance and capital depreciation are very large
components - are dominant. Hence the hugely aerodynamically poor design of
engine pods slung under the wings.

Umm it's not "hugely aerodynamically poor design", HTH.

They are there, because its easy to
replace them in a matter of hours.

And because the alternatives were tried and were no better.