4 ms·

One feature of classical mechanics is that the world must abide by it. With transportation, the vehicle must start and stop at a speed of zero. The energy requi

One feature of classical mechanics is that the world must abide by it. With transportation, the vehicle must start and stop at a speed of zero. The energy required to accelerate the vehicle to its top speed and then decelerate it to back to zero increases quadratically as the top speed increases. Another feature of classical mechanics is, of course, that Aristotelian concept of kenophobia, or horror vacui, or resintenza del vacuo, or natura abhorret vaccum, or nature abhors a vacuum. Of course we now know we can produce vacuums these days... but it's not easy to make one. The largest is in Sandusky, OH, and it's 122 feet high and 100 feet wide. It takes 8-12 hours to achieve vacuum conditions. https://en.wikipedia.org/wiki/Space_Power_Facility https://en.wikipedia.org/wiki/Space_Power_Facility

dalbasal 9y ago
That's a supply problem.
grecy 9y ago
> With transportation, the vehicle must start and stop at a speed of zero. The energy required to accelerate the vehicle to its top speed and then decelerate it to back to zero increases quadratically as the top speed increases. Don't be so sure. The vehicle could move continuously at cruising speed while individual people are brought to/from it and then "dock".
- tintor 9y ago
  Those people still have to accelerate / decelerate.
nickparker 9y ago
The energy required only grows quadratically if you stay on one technology. Simultaneously switching from internal combustion to linear electric motors with efficient regen. braking and bumping the speed up 10x turns out to be a wash.
- wolfram74 9y ago
  To clarify, you are stipulating that electric engines and regenerative breaking are ~100 times more efficient than a combustion engine? Because mv^2 means a 10 fold increase in speed is a 100 fold increase in kinetic energy.
  - nickparker 9y ago
    Thanks for the catch, I wrote that comment a little too flippantly and left out important factors, the motors/regen alone certainly don't get you there. Adding in the reduced drag of levitation vs soft tires combined with central control to avoid stop-n-go intersections/traffic gets you to 100x more efficient. Edit: Also, I should just drop this link to some envelope math I did last Fall: https://medium.com/@nickparkerprint/why-im-still-excited-about-hyperloop-ef66a58aeca8 https://medium.com/@nickparkerprint/why-im-still-excited-abo... And since I didn't think of this either before the first comment: I'm currently an employee of Hyperloop One, but none of the statements made in this thread are at all based on H1's design or proprietary info. They're based on the envelope math above, which was done before I started working there. I don't actually know H1's efficiency numbers because it's not my department.
- deleted 9y ago
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Turing_Machine 9y ago
> The energy required to accelerate the vehicle to its top speed and then decelerate it to back to zero increases quadratically as the top speed increases. What? No. You can, in fact, recover a substantial portion of the energy used to accelerate the vehicle when you decelerate it (quite a lot of it, if it's running in a vacuum with minimal frictional losses). The track would act as a linear motor during acceleration, and a linear generator during deceleration. > Of course we now know we can produce vacuums these days... but it's not easy to make one. You don't need a vacuum anywhere near as hard as the Sandusky facility for a transportation system. That operates at 10e-6 torr, while the Hyperloop will operate at 100 Pascals (about 0.75 torr, or 75,000 times higher).
deleted 9y ago
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dalbasal 9y ago

That's a supply problem.

grecy 9y ago

> With transportation, the vehicle must start and stop at a speed of zero. The energy required to accelerate the vehicle to its top speed and then decelerate it to back to zero increases quadratically as the top speed increases. Don't be so sure. The vehicle could move continuously at cruising speed while individual people are brought to/from it and then "dock".

tintor 9y ago
Those people still have to accelerate / decelerate.

nickparker 9y ago

The energy required only grows quadratically if you stay on one technology. Simultaneously switching from internal combustion to linear electric motors with efficient regen. braking and bumping the speed up 10x turns out to be a wash.

wolfram74 9y ago
To clarify, you are stipulating that electric engines and regenerative breaking are ~100 times more efficient than a combustion engine? Because mv^2 means a 10 fold increase in speed is a 100 fold increase in kinetic energy.
- nickparker 9y ago
  Thanks for the catch, I wrote that comment a little too flippantly and left out important factors, the motors/regen alone certainly don't get you there. Adding in the reduced drag of levitation vs soft tires combined with central control to avoid stop-n-go intersections/traffic gets you to 100x more efficient. Edit: Also, I should just drop this link to some envelope math I did last Fall: https://medium.com/@nickparkerprint/why-im-still-excited-about-hyperloop-ef66a58aeca8 https://medium.com/@nickparkerprint/why-im-still-excited-abo... And since I didn't think of this either before the first comment: I'm currently an employee of Hyperloop One, but none of the statements made in this thread are at all based on H1's design or proprietary info. They're based on the envelope math above, which was done before I started working there. I don't actually know H1's efficiency numbers because it's not my department.
deleted 9y ago
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Turing_Machine 9y ago

> The energy required to accelerate the vehicle to its top speed and then decelerate it to back to zero increases quadratically as the top speed increases. What? No. You can, in fact, recover a substantial portion of the energy used to accelerate the vehicle when you decelerate it (quite a lot of it, if it's running in a vacuum with minimal frictional losses). The track would act as a linear motor during acceleration, and a linear generator during deceleration. > Of course we now know we can produce vacuums these days... but it's not easy to make one. You don't need a vacuum anywhere near as hard as the Sandusky facility for a transportation system. That operates at 10e-6 torr, while the Hyperloop will operate at 100 Pascals (about 0.75 torr, or 75,000 times higher).

deleted 9y ago

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