Er, yes, quite. 😁

But you know what rocketeer are like. Turbo pump sounds so much more exotic.

Been a while since I studied chemistry, but you can create H2 from CO2 and CH4. However this isn't so simple. H2 as the H2 produced has a nasty habit of reacting with the CO2 at low energies. Good for power stations etc,not so good as a fuel source. At a push (although I've never seen it) I'm guessing you could use Sabatier reaction conditions. and end up with CH4 but use a load of CO2 in the process. Not very efficient though.

Why on earth not? It's self-evident to all but the plane-crazy that aeroplanes make an unpleasant noise and mess up the sky with their exhausts. Take a walk in the "World Heritage Site" that is the British Lake District one day. You go for peace, quiet and tremendous views, and return having experienced the continuous daily racket of the Manchester to Glasgow, Paris to New York etc etc flights and the azure sky criss-crossed with numerous trails. Not ideal, although doubtless the people off on their jollies abroad will have a great time, perhaps in turn having their own peace and quiet ruined by the thunder overhead. And so it goes, man handing on misery to man. Planes may have ther good points too, but the noise and the sky-graffiti should be, and in the case of the noise, are being, addressed.

Is this a wind-up? What us unpleasant about an aircraft noise? I find lawnmowers far more annoying, shall we ban them? Oh, and if you can hear Paris - NYC departures in the Lake Ditrict, you mut have bloody good hearing. It would be so quiet (if audible at all). Do ticking clocks 100 yards away annoy you as well.

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Who cares how much volume is used by the hydrogen? The lift of the hydrogen easily overcomes the weight of the any structure needed to contain it.

Fake Pilot
No lift from hydrogen in its liquid form. If you use gaseous hydrogen as the fuel, you couldn't store enough to fly any distance, energy density is too low.

I withdraw....

Someone please close this thread. It's been invaded by loonies.

Personally I'd go for tractor beams, never mind discussing why hydrocarbon fuels have a vastly higher energy density than H2.

Can someone quickly comment on the proposed (re)use of CO2 in making aviation fuel?
https://www3.nhk.or.jp/nhkworld/en/news/20201202_27/

Major Japanese air carrier All Nippon Airways will begin developing fuel made from carbon dioxide in cooperation with several other firms.
The group, including Toshiba, Toyo Engineering and Idemitsu Kosan, aims to put the new fuel into practical use in the latter half of the 2020s. The group plans to produce the fuel by chemically treating CO2 emitted from factories and other sources through technologies owned by Toshiba and Toyo Engineering.
The developers will work to clear several challenges. They include fuel quality and profitability, and whether the fuel can be produced and supplied steadily. ANA started passenger flights using fuel made from food waste in November. The company says the CO2-derived fuel is expected to be able to reduce net emissions further. The aviation industry is in a difficult position on environmental issues, especially in Europe, as aircraft produce more CO2 emissions than trains and other transportation means.

Air carriers are rushing to take action as CO2 emission restrictions on international flights will be introduced next year.

And last year discussed in the BBC
https://www.bbc.com/news/business-49...o%20jet%20fuel.​​​​​​​

It's either a cynical PR exercise, or (more worrying) some idiot has scammed a politician/business person without any idea of science.

Plant a tree - much more efficient way to take CO2 out of the air. Trees are solar-powered CO2 capture machines.

If you're going to make CH2-polymer fuels from CO2 then you have to put in as much energy into that process as burning the fuel gives you for the reverse reaction. It's called the law of conservation of energy. In that sense, liquid fuel is just a "battery" for energy - oil is years of solar energy, stored in CH2 bonds.

If you're going to "make" fuel from CO2 - where is the energy you're going to need to do that coming from? The local coal powerplant? That's on top of the energy cost of collecting the CO2 in the first place, when it only makes up 0.04% of the atmosphere. (So, if you have a 100% efficient collection process, getting a ton of CO2 will need you to pass 2500 tons of air through your collector - and those pumps and whatnot are lost cost - you haven't even started trying to reduce the CO2 to hydrocarbon fuel yet.)

And the (cold) reality pours in. Thank you!

Carbon capture may be the next big thing although it might double the energy cost for fossil fuel plants. It could be that a power station would pay you to capture the CO2 (although unless the facility was burning biomass the exercise would not be carbon neutral once the jet fuel was burnt). Its like cryogenic storage of hydrogen, very useful as a demonstration exercise but certainly not practicable in the short term. If you want to make fuel from CO2 I would grow seaweed and work out how to convert that to jet fuel - although the work so far hasn't been that successful, there could be a breakthrough in the future.

Maybe there could be a synergy between nuclear energy, cement production and aviation.

Build a small modular reactor (such as Moltex) on the same site as cement works.
Reactor provides heat for the cement making process as well as producing hydrogen from water.
CO2 is captured from the cement making process and combined with the hydrogen to make liquid hydrocarbon fuel for long haul aviation.

CO2 is emitted when the fuel is burnt, but...
Cement is made into concrete structures which absorb CO2 during their lifetime.

Your objection about the aesthetics of contrails brings to mind the obvious eventual result of "carbon free" electricity production using wind turbines, solar farms, and battery storage.

The physical installations needed to provide replacement for power that is now produced with fossil fuels will eventually cover practically every ridgeline, prairie, and desert on earth. The adoption of nuclear powered generation would provide an alternative whose footprint would compare favorably with current fossil fueled powerplants, but that is, of course, out of the question.

It appears that so far this has not occurred to the proponents of green energy production.
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The idea of 'making' hydrocarbon fuels is not new (think of the synthetic petroleum the Germans used during WW II) - although the rational is changed. The Germans used coal to make petroleum - the new plan is to make petroleum from CO2 and hydrogen using excess electricity. It won't be cheap, and it's dependent on a plentiful supply of 'green' electricity, but it's far from pie in the sky. One of the problems with most 'green' electrical production is that it isn't consistent (solar) or reliably predictable (wind), meaning sometimes you're going to have large surpluses or large shortages. Using those periods of large surplus to manufacture hydrocarbon type fuels is one way to balance out the peaks and valleys.

Personally I think bio (algae) based hydrocarbon fuels are the future of aviation, but assuming we can create large scale 'green' electrical electrical generation, manufacturing hydrocarbon fuels is certainly a viable option.