Primarily for general aviation discussion, but other aviation topics are also welcome.
By johnm
FLYER Club Member  FLYER Club Member
#1885058
Given that water vapour is a serious greenhouse gas then sustainable avtur and avgas might well be a manageable answer alongside hydrogen fuel cells and multiple electric motors maybe???

The production of hydrogen from paraffin wax using microwaves (powered from renewable energy sources) has been demonstrated as has combining hydrogen with atmospheric CO2 so there are some promising avenues which could develop very quickly if the investment is there.
By johnm
FLYER Club Member  FLYER Club Member
#1885128
Genghis the Engineer wrote:Water isn't much of an issue as a greenhouse gas so long as it's well below the tropopause.

G


However long haul jets regularly reach the stratosphere don't they??
#1885138
johnm wrote:
Genghis the Engineer wrote:Water isn't much of an issue as a greenhouse gas so long as it's well below the tropopause.

G


However long haul jets regularly reach the stratosphere don't they??


They do, but this is all quite complex.

The arctic winter tropopause can get as low as 25,000ft - and flying below it in a jet is highly unlikely. The equatorial tropopause can get above 55,000ft - and flying above it in a jet is highly unlikely.

Most hydrogen technologies in current consideration involve fuel cells, driving electric props - and that technology hasn't really been proven very high yet (although as compared to anything breathing air, performance should be much more constant with altitude, so there may well be reasons to operate fuel cell / electric aircraft into the lower stratosphere - even if the only people doing that so far have been a tiny number of research aircraft and spyplanes.

My gut feeling on this is that in the short to medium term, electric / hydrogen aircraft will be regional and operating below around FL250 - so the water issue will be fairly trivial. Longer term, who knows what the trajectory is, but water may become a significant consideration.

G
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