3 ms·
I don’t understand why a Hyperloop is the next logical step. Making a low pressure tube is probably pretty hard at scale. Every design is trying to minimize ai
by elamje 7y ago
I don’t understand why a Hyperloop is the next logical step. Making a low pressure tube is probably pretty hard at scale.
Every design is trying to minimize air resistance. Why not wrap already existing high speed rail lines with a cheap air barrier then create a wind tunnel inside rather than a vacuum? If you could move air at a similar speed to the train you could achieve wind resistance that is effectively negligible or even negative.
Am I thinking about this wrong? Is the energy required to remove all air from a tube significantly lower than pushing air through the tube while a train moves?
- AlbertoGP 7y agoI guess that the air resistance against the air barrier would be even higher: if the air is moving at the speed of the train, you have the same friction per surface unit than you would have with static air against the moving train, only your area is now much bigger. You do save the energy needed to part the air aside as the train moves forward, since the air barrier would have a constant cross-section. I don’t know how that compares to the increase in friction due to greater surface. Finally, other aspect I just realized: when you try to stop the train, you have a rush of air pushing you at several hundred Km/h, and that would be an enormous mass. You could enter a side branch which would then close behind the train and have a smaller mass of air to slow down. I’m not an engineer and have no experience on the subject, but my hunch is that it could easily end up being even more difficult.
- Faint 7y agoI bet air rushing through 100 mile tunnel has _much_ more resistance than half a mile long train rushing through air at same speed. There is much more interface between a wall and moving air at the former case.