>>1762878Drag is approximately proportional to air pressure. If you take the pressure down from 760 mmHg to 1 mmHg, you've reduced drag by four orders of magnitude. At that point you're losing incomparably more energy to braking, etc: it might as well be a perfect vacuum.
>>1762854no material is air tight so the vacuum will need constant pumping to be kept
How much gas do you think is going to diffuse into a tunnel, say, 10 meters underground? If you seal the doors that's perfectly viable.
Consider the Large Hadron Collider - ignoring all the magnets and shit, it's a 26 km long tunnel. It can be evacuated to 10^-11 mmHg in a couple of days - a far higher vacuum than would be needed for a hyperloop. Even if those pumps have to run at capacity constantly to keep the vacuum they can't be pumping much more than 50 L/s (at ambient conditions) for those numbers to work out. If not for the high vacuum they need - and, again, you don't need that for a hyperloop - that would be achievable with large commercial HVAC system.
