4 ms·

I love this concept! My main concern is the air-bearing suspension system. Barring very high flow rates, the fly-height of an air-bearing system is very small.

I love this concept! My main concern is the air-bearing suspension system. Barring very high flow rates, the fly-height of an air-bearing system is very small. Some systems[1] fly at 5 microns, for instance. That being the case, any sort of particulate or imperfections in the tube will cause the air-bearing to 'land' with a large amount of friction. Perhaps this is alright if you're already going 700mph, but it would reduce the overall coasting efficiency of the system. The engineer in me sees this as the most important design consideration of the project. As an aside, I would like to see trade studies done on filling the tube with other gasses whose speed of sound is much higher than air's, allowing the capsules to travel even faster before shocks begin to form. [1] http://www.newwayairbearings.com/products/flat-rectangular-air-bearings/air-bearings-flat-rectangular-150mm-x-300mm http://www.newwayairbearings.com/products/flat-rectangular-a...

ansible 13y ago
As an aside, I would like to see trade studies done on filling the tube with other gasses whose speed of sound is much higher than air's, allowing the capsules to travel even faster before shocks begin to form. I don't think this is a good idea for production use, because then you have to worry about air leaks to/from the passenger compartment. As it is, you still have to guard against explosive decompression for the passengers.
- clarkmoody 13y ago
  Well that's the point of a trade study: look at the cost/benefit of different gasses. Obviously one of the costs would be the increased engineering um...pressure put on the capsule design. Your gut feeling is probably right, though, at least for this length of trip. The increased cost of a different tube gas probably won't outweigh the benefits of arriving 5-10 minutes earlier. Now if there were a cross-continent Hyperloop system, then for segments of the trip it might be much better to have a different gas. But again, it might simply be better to invest in better vacuum pumps for certain legs of the journey to get lower drags and higher speeds.
  - Turing_Machine 13y ago
    http://www.phy.mtu.edu/~suits/SpeedofSoundOther.html http://www.phy.mtu.edu/~suits/SpeedofSoundOther.html The only ones I see that are significantly higher than nitrogen/oxygen are methane, hydrogen, and helium. Helium is mondo-expensive. It's not cheap even in welding-tank quantities, much less in the amounts you'd need here. Hydrogen is flammable and/or explosive (depending on mixture) and is a huge pain in the butt to keep confined (so is helium). Methane is cheap (but not as cheap as air :-)), and we have lots of experience with keeping it confined in big pipes. However, it's also flammable or explosive. Using anything but air is going to require some sort of complicated replenishment/purging system and an air lock at both ends, whereas air leaks just require pumping it out again.
    - nardi 13y ago
      Neon -> 2,090mph Krypton -> 2505mph Xenon -> 2,438mph http://www.wolframalpha.com/input/?i=speed+of+sound+in+neon http://www.wolframalpha.com/input/?i=speed+of+sound+in+neon http://www.wolframalpha.com/input/?i=speed+of+sound+in+krypton http://www.wolframalpha.com/input/?i=speed+of+sound+in+krypt... http://www.wolframalpha.com/input/?i=speed+of+sound+in+xenon http://www.wolframalpha.com/input/?i=speed+of+sound+in+xenon But even Neon (which is more abundant in the atmosphere than Helium) would cost ridiculous amounts of money to use.

ansible 13y ago

As an aside, I would like to see trade studies done on filling the tube with other gasses whose speed of sound is much higher than air's, allowing the capsules to travel even faster before shocks begin to form. I don't think this is a good idea for production use, because then you have to worry about air leaks to/from the passenger compartment. As it is, you still have to guard against explosive decompression for the passengers.

clarkmoody 13y ago
Well that's the point of a trade study: look at the cost/benefit of different gasses. Obviously one of the costs would be the increased engineering um...pressure put on the capsule design. Your gut feeling is probably right, though, at least for this length of trip. The increased cost of a different tube gas probably won't outweigh the benefits of arriving 5-10 minutes earlier. Now if there were a cross-continent Hyperloop system, then for segments of the trip it might be much better to have a different gas. But again, it might simply be better to invest in better vacuum pumps for certain legs of the journey to get lower drags and higher speeds.
- Turing_Machine 13y ago
  http://www.phy.mtu.edu/~suits/SpeedofSoundOther.html http://www.phy.mtu.edu/~suits/SpeedofSoundOther.html The only ones I see that are significantly higher than nitrogen/oxygen are methane, hydrogen, and helium. Helium is mondo-expensive. It's not cheap even in welding-tank quantities, much less in the amounts you'd need here. Hydrogen is flammable and/or explosive (depending on mixture) and is a huge pain in the butt to keep confined (so is helium). Methane is cheap (but not as cheap as air :-)), and we have lots of experience with keeping it confined in big pipes. However, it's also flammable or explosive. Using anything but air is going to require some sort of complicated replenishment/purging system and an air lock at both ends, whereas air leaks just require pumping it out again.
  - nardi 13y ago
    Neon -> 2,090mph Krypton -> 2505mph Xenon -> 2,438mph http://www.wolframalpha.com/input/?i=speed+of+sound+in+neon http://www.wolframalpha.com/input/?i=speed+of+sound+in+neon http://www.wolframalpha.com/input/?i=speed+of+sound+in+krypton http://www.wolframalpha.com/input/?i=speed+of+sound+in+krypt... http://www.wolframalpha.com/input/?i=speed+of+sound+in+xenon http://www.wolframalpha.com/input/?i=speed+of+sound+in+xenon But even Neon (which is more abundant in the atmosphere than Helium) would cost ridiculous amounts of money to use.