Why not put a maglev train into a tunnel that has been sealed at both ends and is a vacuum. The only way to get into the train is via an airlock at the stations. The maglevs stop friction with the track because it floats above the track, the air in the tunnel has been sucked out so it really has no friction.
There would be circular magnets in the tunnel which can accelerate the train to huge velocities for long distances and then half way there the train could begin to slow down.
Why not? Cost (development and construction of the train and development and construction of the tube infrastructure). Unless you could prove that this train would generate huge income, no private company will throw money at it.
The underwater tunnel between England and France will never ever become profitable but they went along and poured money into it. It was a diplomatic thing and a publicity stunt. But hey don’t humans do that all the time? The International Space Station wasn’t firstly designed with science or profitability in mind. The Pyramids had a purpose? Haia Sophia (the most expensive structure in the history of the world) had a purpose other than to prove how marvelous the Christian Church was?
Let’s build my Hypersonic train. It’s a themepark ride, super fast travel and a diplomatic tie all in one.
You’re right. Not everything has a profit-making purpose. But comparing a train to a religious building, or to a research station is comparing apples to oranges. A train is a freight/passenger transport system, and nothing more. NO great technological advances are likely to come from a train, it won’t prove a momentous diplomatic monument and nobody’s going to worship it. It won’t even be a useful transport system unless it provides a service that people want. Nobody builds things for absolutely no purpose anymore. Governments don’t have the cash to flash - and if they did, public outcry would put a swift end to that (cf. the UK’s Millennium Dome debacle). Private companies don’t want to invest in non-profit-making ventures, generally. Research organisations are the only ones likely to be interested, but I’d be surprised to find one with the cash or interest to build a rail network. What would they hope to learn?
Sorry. Don’t mean to disappoint, but someone would have to pay, and these days nobody wants to hand money over for absolutely nothing.
where are you going to build the tunnel? It would have to be in an area of very low geological/volcanic activity.
I suspect that building what is (in effect) an enormously large (enormously strong) pressure vessel is light years (to mix my metaphors) ahead of building, say, the Channel Tunnel, which although very impressive is pretty much a large concrete tube.