Rhrosty, magnetrons are not a mode of transport.

If you mean maglevs, none has yet reached anywhere near 900km/h. It might be technically possible but due to the huge air resistance at ground level, they'd end up using far more energy than aviation. Fast ferries aren't particularly efficient, but submarines are extraordinarily inefficient. Not only do they need to push a lot of water out of the way, but there's little room for payload as most of their bulk is dedicated to bouyancy control equipment.

Planes are never "forced to stop" though they are sometimes forced to circle, turn back or divert. And they have wings and control surfaces, so if they lose power they don't "fall like a stone"; they glide and can be landed safely.

And if you want to use nuclear power for transport that can't be electrified, it's more sensible to use electrical power to synthesise fuel from air or seawater than to carry a nuclear reactor on board.

Aidan, the magnetron is I understand, what the magnetic drive that propels maglevs are called. And given vastly reduced friction, use less energy than almost any other mode of transport. And moreover, are therefore not subject to bearing failures, that have derailed other fast trains!?

And for your information the Chinese have already built one, and years ago, capable of the quoted 900+ klicks! [Obviously you rely on extremely dated information for that and the nuclear option?]

And therefore a critical candidate for replacing much slower less safe air travel.

And if a plane loses motive power and say faces a mountain range, gliding is limited and soon overtaken by the stall factor, and then terminal velocity straight down!

Using nuclear to create hydrogen results in an 20% minimum loss of energy; lost in the conversion process; and that's where the most efficient means of using the hydrogen (fuel cells) are incorporated!

And anyway, nuclear options are far safer than they once were and likely far safer than any volatile fuel; and in the case of hydrogen needing vastly more storage space, and likely to cause huge flotation problems in subs unless stored as a subzero liquid!

Which then creates other new problems including the huge amount of energy just to compress it!

Yes water presents friction problems, always has! But then oceans also have huge rivers or currents that can be utilized to assist transport.

Indeed, there is a narrow waterway approaching the aforementioned Turkey, that has strong currents going both ways at different levels.

And subs will still be able to travel when conditions are just too hostile (including nuclear fallout) for any other form of transport! And if your life depended on getting in or out? And nuclear fuel only needs to be replaced around every 25 years? And what will current conventional fuels cost then?

And if the option to use rapid rail were the universally preferred option, then one would likely need to connect various land masses with tunnels or very fast roll on roll of ferries; many of which are already semi submersible!?
Rhrosty.

Rhrosty, maglev (magnetically levitated) trains are supported by a magnetic field that is generated within electromagnets. They are propelled by linear induction motors. Although it is possible that with appropriate rotation of the coils the two functions can be combined, in many cases it is more practical to separate them into two separate functions.

Linear induction motors are actually not very energy efficient, but this is acceptable if the purpose is to go fast. They have much better tractive efficiency than steel wheels on steel rails and it is the loss of traction that ultimately limits the speed of conventionally-driven trains.

The Chinese are really leading the world in the development of high speed rail. The rate they are rolling out the infrastructure is astonishing.

Elon Musk's "hyperloop" is another form of high-speed rail which doesn't use magnetic levitation, but air-cushioning, although propulsion is still linear induction. The efficiency is enhanced by careful management of the airflow around the train, including pumping air from in front to behind the train and partially evacuating the tube it runs in. It will be a great project to watch unfold.

Rhosty, you misunderstand. The magnetic drives that propels maglevs are called linear induction motors.

Magnetrons are something completely different: they're a device for generating microwaves.

The Chinese Maglev has barely exceeded 500km/h. The world record, held by the Japanese, is 603km/h.

And if a plane loses motive power and say faces a mountain range, the pilot turns the aircraft away from the mountain range and looks for somewhere to land.

I was not suggesting using hydrogen to power submarines (though AIUI this has actually been tried). I was saying synthesis of hydrocarbon fuel to power conventional aircraft would be much much much much more efficient than using submarines in their place, despite a lower conversion efficiency.

Hydrogen may be a good aviation fuel source in some circumstances, because its light weight outweighs at least some of the disadvantage of its bulk. It has been tried, but I think it's safe to assume that most, if not all, aircraft will stick with hydrocarbons for the foreseeable future.

Submarines are too expensive as well as too inefficient to be viable for public transport. As for ocean currents, they're generally much slower than the wind, so if minimising energy consumption is the objective, sailing ships are the best option!

I suppose it's conceivable if there's a nuclear war that submarines could become the best transport option, but I certainly wouldn't want to waste resources planning for that situation.

Yes Craig and thanks for that!

However, as it was explained to me, the magnetron utilizes the fact that same pole magnets want to do anything but remain perfectly aligned?

So by sequentially switching on and off some of the electric magnets, force them to propel the magnetically suspended train forward?

And given the repulsive force of each repelling (N to N, S to S) pair, of around 9 tons of repelling/opposing force per pair, [say a thousand pairs,] considerable forward momentum?

I also wonder why the walls containing an underground or tubed train couldn't be similarly utilized, to keep the train centred and provide even more forward momentum?

The novel idea of something floating on air and driven by partially created forward vacuum and increased rear pressure inside a tube, sounds as if it might include considerable speed?

And aren't we operating some tube lifts like that now with compressors/vacuum pumps?

Perhaps something like hydrogen powered scram jets could be utilized to move the air fore and aft?

And given inertia rather than friction/air resistance, the only thing then needed to be overcome? Possibly the fastest means of moving people and or things?

And given a tall enough tower, [an air-locked and endlessly reusable tunnel inside a conveniently located mountain, say], able to build up to an escape velocity for the purpose of mass launching of satellites i.e.? Not entirely dissimilar to K.G. Well's lunar launch cannon?

Except the only thing needing to be explosively ejected, would be the final air lock door?
Rhrosty.

The third comment in this trail was about potential high tech transport options. From there on they were the main topic, mixed with a bit of old-fashioned AGW denial. The original article was trying to make the point that Australians are taking an extraordinary number of short overseas holidays and making a significant contribution to global greenhouse gases.
Interestingly, this closely mirrors an actual conversation recorded in Kari Marie Norgaard's book 'Living in Denial'. Young Norwegians are asked if climate change is something they think or talk about. Almost immediately they are talking about electricity prices, and not climate change.
Norgaard suggests that we are all subject to 'socially organised denial (in) which individuals collectively distance themselves from knowledge because of norms of emotion, conversation and attention'.
Climate change makes us uncomfortable. We lack clear knowledge and are frightened by the problem with no solution. We are reluctant to give up the pleasures that we feel entitled to and want to continue to enjoy, without the disapproval of peers. We prefer to talk about almost anything else.
High tech transport is great and I'm happy that the future will provide new and interesting ways to get around. I also hope that we can get emissions down soon so that the destinations are not distressingly hot and dry, burnt, blown away or flooded.