General > General Technical Chat
The Hyperloop: BUSTED
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Brutte:

--- Quote from: Maxlor on August 03, 2016, 07:18:38 pm ---I'm dubious that's a viable solution. Let's do some back of the envelope calculation:

Let's say there's a 100K temperature differential we need to consider, and our pin points are 1000m apart. The elongation of steel is 12ppm, so our previously 1000m of tube are now 1001.2m long.
--- End quote ---
Or you heat the cold 1000m pipe to that +100K limit and weld that 1001.2m to the rest of the pipe.
Or you can stretch cold 1000m pipe to 250MPa when it reaches 1001.2m and then weld it.
Or heat it to +50K and stretch it to 125MPa and then weld it.
Whatever.

In above cases it would have 1001.2m and 0Pa strain at hot days and 1001.2m and 250MPa in tension at cold days.

No curves or bumpy ride is needed.
EEVblog:

--- Quote from: rs20 on August 03, 2016, 07:49:29 pm ---Obviously keeping the air out of a hyperloop using O-rings is vastly more expensive than that, but I feel like vacuum on Earth is a less precious commodity than air is 400km up where the ISS is.

--- End quote ---

Yes, but the ISS doesn't have a huge object hurtling through it at the speed of sound, it's not 600km long, it's not susceptible to storms and earthquakes and rednecks banging on it, has many orders of magnitude less joints, and it has a predictable thermal and stress environment.
I'd take the ISS any day of the week.
Mark_Of_Sanity:
Btw for the cascading effect in the case of a rupture, surely you could design the tube to
just collapse at that point. Ofcourse it won't shut the tube with a vacuum tight seal but
it would greatly reduce the opening and reduce the inflow.
So at least it won't be destructive.

P.S.

Also why can't they drive a few stakes of steel into the earth underneath as a heat sink every 100 meters or so,
or as needed? Drive a metal rod maybe 5-6 meters into the ground with thermal insulation where needed to protect from
sun light and other sources of heat. And you would reduce some of the thermal expansion.
stj:
i dont know why your all talking about surface-rail.

underground rail is more expensive to build - initially.
*BUT*
surface rail requires years of negiotiations over land leasing / purchase etc.
and you have issues with objects in the way of the route that cant be purchased and leveled,
not to mention the terrain will need to be leveled in places and built-up in others.

it's also more vulnerable to nature, accidents, and sabotage.
edavid:
I don't think we have the technology to dig a 400 mile tunnel :(
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