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Hyperloop

spacex.com

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Re: Hyperloop

#931

Post by DonPedro »

eru wrote: post #916
jholman wrote: post #884

Earlier quoted context omitted.

> it doesn't seem to require tight tolerances for operation Well, it's true that the top and sides of the tube don't get too close to the capsule, so those parts seem relatively low-tolerance, as you say. But the load-bearing skis ride on an air bearing of 0.5mm to 1.3mm (see page 20), moving at over 1000km/h. As rossjudson notes, the skis are on mechanical suspension, to smooth out shocks to the riders, but it's not…

You could just build the tubes bending upwards slightly, so that the sag will pull them straight.

No you could not. The steel tube will expand and contract as temperatures change. Along most of the route, that longitudinal movement of the tube will be in the 10s and 100s of feet, which means that the "valley" could be anywhere on the tube according to temperature.

Re: Hyperloop

#932

Post by mhandley »

krschultz wrote: post #459

This is very serious first proposal. As a professional mechanical engineer I have worked on high quality steel tubes (nuclear submarines) before. The immediate thing that sticks out to me in this proposal are the tight mechanical tolerances that have to be maintained. Talking about tens of thousandths of an inch tolerances on a 10' diameter tube is not to be dismissed lightly. That is going to be tough to maintain -…

The tube is considerably larger than the vehicle, so really it's only the smoothness of the bottom part of the tube that is important, not the precise dimensions. And the surface the vehicle flies over doesn't need to be steel - you could line the bottom half of the tube with a wax, or something similar, and that would be much easier to smooth to the tolerances needed, and re-smooth if it suffers any damage.

In fact you might be able to handle some thermal expansion (at least seasonal, not daily) that way - release some clamps on a telescopic section, adjust, reclamp, melt and re-smooth the wax.

Re: Hyperloop

#933

Post by DonPedro »

willyt wrote: post #927
krschultz wrote: post #459

This is very serious first proposal. As a professional mechanical engineer I have worked on high quality steel tubes (nuclear submarines) before. The immediate thing that sticks out to me in this proposal are the tight mechanical tolerances that have to be maintained. Talking about tens of thousandths of an inch tolerances on a 10' diameter tube is not to be dismissed lightly. That is going to be tough to maintain -…

Back of the envelope, SI units. 13 × 10^-6 thermal expansion coefficient of steel 45 - -40 max temp difference 570k length of tube in meters line1 × line2 × line3 = 629m (~1890') of thermal expansion over a 570 km tube. Did I read it right that they will take out all that expansion at the ends? To get that down to say 30m between pylons you have to have about 30 expansion joints. Can they go full speed through an exp…

They are taking it out at the ends. Assume a fixed point in the middle, and you have some 1000' of movement at either end. That should be feasible, but the tube needs to be designed for very significant longitudinal movement through the pylons, and the design needs to take into account the possible lateral loads on pylons from having to bend the tube away from the geometry it has at the baseline temperature.

Re: Hyperloop

#935

Post by DonPedro »

goodcanadian wrote: post #188

I am intrigued, but not overwhelmed. Many of his reasons why his hyperloop is superior to high speed rail are not specific to the hyperloop. For example, you can put railway tracks up on pylons, too, with very little impact on the ground. It is common to do this in urban areas, but it is rarely done in rural areas because it is flat out cheaper to put it on the ground. I don't believe that an experimental tube is goi…

The basic issue the hyperloop overcomes is the energy waste in train transportation, especially at high speeds. This is primarily about aerodynamics, and secondarily about carrying with you the propulsion system. Third, it overcomes the "chunkiness" of the rail system, where passangers needs to be assembled and grouped into train-sized lots for transportation, rather than being able to depart continuously. You get superior energy economics, speed and convenience. I cannot see how that would be disappointing.

Re: Hyperloop

#936

Post by dllthomas »

jarek wrote: post #900
MAGZine wrote: post #897

Earlier quoted context omitted.

I somehow think that if people wanted it, it would come faster than 2040. We're working towards fusion power faster than that!

If people wanting it made technology feasible, we'd have had flying cars in 1990

If it's technologically possible, economically profitable, and people want it, then. Flying cars have difficulties this doesn't (seem to) on all three counts.

Re: Hyperloop

#937

Post by DonPedro »

omegant wrote: post #702
ricardobeat wrote: post #525

Earlier quoted context omitted.

From the linked article: At or above the Armstrong limit, exposed bodily liquids such as saliva, tears, and the liquids wetting the alveoli within the lungs — but not vascular blood (blood within the circulatory system) — will boil away without a pressure suit As mentioned above, we have been boarding planes without pressure suits for decades, and the hyperloop has two security advantages: it has a large supply of co…

A dedicated hypoxia document by the FAA: http://www.google.be/url?sa=t&rct=j&q=&esrc=s&source=web&cd=... You got to think that a decompression will happen. Something traveling that fast inside a tube is probable to develope vibrations and material fatigue if something is not working properly (like the compressor or a air cushion), also there can be small parts released from the front pod impacting on the next one. It…

Obvious engineering issues for further investigation. I would just point out that fatal failure mechanisms can be pointed out in any transportation system. The acceptance criterion is a sufficiently low fatality rate.

Re: Hyperloop

#939

Post by DonPedro »

toble wrote: post #112
toddmorey wrote: post #92

Earlier quoted context omitted.

How is that any worse than standard commercial air travel? Plus, really, you are talking about a thirty-minute journey.

You can get up and walk around on a plane.

I'd rather be stuck in my seat for 35 minutes than to travel to an airport, go through security, check-in, waiting and boarding, fly for 90 minutes and then apply all the logistics in the other end. Your point is valid, but I would contend that the total package is still superior.

Re: Hyperloop

#940

Post by acqq »

rtkwe wrote: post #928
tinco wrote: post #926

Earlier quoted context omitted.

You can't stand up in a car either. In any case the ride is going to get you to qualified medical personnel within half an hour :)

You're in control of your car though so if you need to you can stop and get out to deal with any bodily functions or sickness. You can't do that in this train. There's a lot to be said for the effect of just having the option even if you don't exercise it. Control is very comforting to people.

Not only comforting, the seemingly "rare" cases actually happen all the time and the advantages of being able to stop, go out, help the person etc. are effectively used all the time.

Designing mass transportation while ignoring such aspects is like programming without handling the limit cases "it works for N between 2 and 100 but not for 0, 1 and MAX_INT, even if these are allowed inputs." It's bad, very bad for the user, only an "astronaut developer" can love such a solution.

The first time a kid dies because it got sick the first minute of a 30-minute ride, the project is dead for good. Imagine the press, imagine the public response.

I can imagine entering the capsule to reach the international space station, preparing a whole year before. I can't imagine doing the same preparations for the ride between SF and LA. Give me the real train, thank you.

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