The nuance about "Elon making Hyperloop just to oppose high speed rail" is that he isn't intrinsically opposed to high speed rail itself. He's just opposed to t

The nuance about "Elon making Hyperloop just to oppose high speed rail" is that he isn't intrinsically opposed to high speed rail itself. He's just opposed to the fact that California high speed rail is way more expensive and way slower than high speed rail elsewhere. If we could build high speed rail that's as fast as the ones in China, Japan, and Europe and cost the same amount, then that would truly be amazing and there would be no need for hyperloops. Anyway, a lot of these "hyperloops are scams" articles just talk about how Elon hates high speed rail and never delve into the technical details of why hyperloops don't work (so far, anyway). The main idea of hyperloop is to use a compressor in the front of the pod to send air to the back, avoiding the inefficiency of pushing a lot of air in front of it like a syringe. This would allow the tube to contain some air, making it cheaper to maintain than a truly vacuum tube. The idea was explored in the 1990s for the similarly ill-fated SwissMetro project. However, aerodynamic simulations showed that the Hyperloop pod design would need to be redesigned to avoid supersonic flow, and the tube would need to be much bigger. I'm not sure if anyone has actually managed to make an active bypass pod that uses a compressor in front to improve efficiency in a tunnel and would be very curious to learn more.