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allenout t1_j8ezuc6 wrote

Reply to comment by mhornberger in 7 international companies have teamed with the EU to form the International Hyperloop Association, the industry's first trade body. by lughnasadh

It's worth mentioning that the partial vacuum you are describing is actually 99% vacuum. Getting a true vacuum is impossible.

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mhornberger t1_j8f1oif wrote

> actually 99% vacuum

I'm not sure what "99% vacuum" means in technical terms.

https://brilliant.org/wiki/hyperloop/

>>it is instead proposed that the Hyperloop tube operate at very low pressure: 100 Pascals, about 1/6 the pressure of the atmosphere of Mars [1]. This pressure is one thousand times less than atmospheric pressure at sea level and as a result air resistance is drastically decreased. After initial acceleration, Hyperloop pods can therefore mostly glide without applying any thrust until the deceleration at the end of the journey.

But I've read other proposals with higher, or variable, levels of pressure in the tubes.

https://hyperloopconnected.org/2019/02/variable-tube-pressure-a-new-concept/

The point was never to champion Musk's specific proposal. He didn't invent the idea of vactrains, and his white paper is just one paper.

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allenout t1_j8g025f wrote

"Let's take expensive maglev and make it more expensive and dangerous by putting a tube around it so we came make a vacuum, but then let's not actually make a vacuum because that's only on 1 white paper".

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king5327 t1_j8g3a59 wrote

A tunnel is a terrible place to have a train, on account of needing enough space around it to pass the air, else you enjoy a pressure bubble at the front of the train. But increasing the cross section of a vacuum tube is a non-negligible nerf to the effectiveness of the vacuum pumps, causing similar drag anyway.

This leads me to believe that even if the technology works perfectly, the numbers alone won't allow for the performance that was promised, unless at extraordinary expense in running the pumps.

Edit: Also, if there are any magnets at all on the car, or along the length of the tunnel, induction is going to be a surprise drag.

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