this post was submitted on 12 Aug 2025
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Sure. And now the question is if halving the travel time is worth whatever it costs to double the speed.
In some cases, it is. There's a grand total of one ocean liner left in the Western world, for example, despite the energy efficiency. If we include communications, doubling speed has been profitable tens of times.
The Concord had problems with energy use getting ridiculously higher right after the sound barrier, which made it not worthwhile, and which is why 21st century passenger jets fly just below the speed of sound. That's a straight example, but I guess I just take issue with it being represented as mathematically inevitable and not situation-dependent.
I read an article about China's HSR that stated that a line with a top speed of 350km/h was 90% more expensive to build than a line built for 250km/h. The trains don't spend much time at top speed during short journeys either. https://www.economist.com/china/2017/01/13/china-has-built-the-worlds-largest-bullet-train-network
A cubic meter of air weighs 1kg according to a Big, Bigger, Biggest episode about France's TGV. Japan's new Maglev is significantly smaller than the Shinkansen and the tunnels it runs through are 20% bigger since standard HSR already has problems with tunnel boom that can be mitigated at the tunnel entrance and exit. I also wonder how trains traveling in opposite directions will handle passing each other at 1000km/h given China is already working on next gen trains with that speed as a goal.
Yeah, journey length is a huge factor. Over, like, a block or two walking is as dominant as a million years ago. Over continental distances airplanes are the thing to beat. Ordinary rail is promising, and vactrain concepts seem like the best very-long-term option. I did some napkin math that shows for an antipodal trip, even orbital travel can be energy-competitive, given one of a couple improvements beyond existing rocketry.
You have to adjust for Chinese truth in advertising a bit, so we might not find out, although apparently their rail infrastructure is a notable bright spot. You have to think the shockwaves would be loud, and potentially damaging to the trains, and the solution would be preventing them from ever passing close by, either with barriers and a wider allowance or careful scheduling.