Discussion in 'Architecture & Engineering' started by Walter L. Wagner, Jun 5, 2007.
Unless they are in a tube, of course.
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If it's a vacuum tube can you actually go supersonic?
well if you made it extremely stable...and vacuumed it...why not? There want be any shockwaves...cause there is no air.
And you wouldn't be supersonic either since supersonic, by definition, is exceeding the local speed of sound in the surrounding air. Vacuum tube = no air to have a speed of sound in.
oh come on silly...Please Register or Log in to view the hidden image! ....suPersonic sPeed that is, faster than sound
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Faster than the speed of sound in the surrounding air.
Which is why "supersonic" has different mile/ kilometre per hour values at different altitudes and different air temperatures/ pressures.
Supersonic only has meaning when in air.
No-one ever claimed that the Apollo capsules travelled at supersonic speeds while journeying to the moon did they? That's because they were in vacuum.
well ok than faster than 343 m/s in relation to meters of the PiPe wall.
But no sound transmission through the vacuum.
Unless you want to work out the propagation rate through the metallic structure of the rails and body of the train? Please Register or Log in to view the hidden image!
ok genius...if theres no air ,what will the passengers breathe??
what about earthquakes?they do happen every day, thousands times a year if not more,
me thinks Maglev is better idea the latest one in China runs 400 klicks/hr plenty fast imo.also you can watch the country side go by,unlike being locked up tight inside some tube.
Thanks for the compliment, I quote below.
As for the second part of that sentence:
"if theres no air ,what will the passengers breathe??"
The passengers would be in pressurized passenger cars, at normal atmosphere pressure. The cars would be in a 'train' that would travel through the evacuated tube.
Passengers would have a video-screen that would give a view of the passing scenery, I would imagine. They would know where they were at all times, if they chose. I would imagine, since they would be reclining, that they would choose to nap, instead, for an hour or so.
As for earthquakes and landslides, if you are unfortunate enough to be buried by one, you die. Same is true for conventional transportation. Of course, earthquake engineering would allow for stopping of the train, automatic closure of the tube at various points [to protect the vacuum], emergency evacuation, etc.
Ya' know, ....that really has to be a giant sucking machine to pull a vacuum in a tube that large and that long! ...and that fast, too! I wonder how much power would be required to suck that vacuum? Scary, ain't it?
Engineers I've asked to look at that have considered that that would be one of the single largest expenses - expending the energy to evacuate the tube of air, down to about 0.1% or less. It might take months, or even years! It would require a large battery of vacuum pumps, I would imagine. It would be something well engineered to maintain, once obtained. Accidental air leaks would be very costly. That's why it's suggested that initially it would be set-up for mail/parcel delivery, e.g. across the continental US.
I've enjoyed your incisive wit on numerous of your other posts!
Cost per passenger mile/km is certainly an important consideration.
Science fiction includes a subway line that is a chord (straight line between two points on a circle or globe) between two cities. The idea is that gravity makes the subway fall to the midpoint (deepest point) of the tube, where it has the highest speed, and then inertial plus a little energy gets it to the surface. I have a fondness for these counterbalance-type ideas.
Of course there’s the little matter of digging and magma to contend with. My impractical idea is to put the tube above ground, with the midpoint touching the ground and the ends a few stories above the ground. Then connect tubes like this to make a network.
I’ve had some kick-ass very realistic dreams of the future. In two of them I checked out the transportation system. One was an unidentified mid-sized city that had gondolas similar to those at fancy ski resorts. Each gondola held maybe ten people. They crisscrossed all over the city, passing each other at different levels up to about ten stories high and coming down to ground or second-story level stations. One of the pylons was in the corner of a backyard in a residential neighborhood.
The other city was Seattle in 2736. I saw no cars, but there were moving walkways everywhere outdoors. I was fascinated at how they could accelerate from human walking speed at the stations to about 25 mph / 40 kph. The tracks looked just like chain mail. Later I thought maybe a chain mail track can accelerate because it can compress / stretch somewhat (to see this interlink two okay signs made by your fingers).
What I like about these two transportation systems is that they seem relatively cheap to build (unlike the $billion tunnels Seattle is building now for light rail) and there was little-to-no waiting for a ride. When there’s little waiting, you can move slower yet still get to your destination faster. When the system is cheaper to build, the public can afford more lines, which can also get you to your destination faster. The gondola system in particular appeals to me because you’d get a nice view and lots of people would probably be willing to accept a pylon in their yards in return for easement payments, so the system would seem to be among the cheapest to build. It could be built without tearing down existing structures. Of course there are some disadvantages like rescue access and unsightliness.
My thinking is, the cheapness of a transportation system is somewhat self-fulfilling, because if it’s cheap, then more people ride, which makes it cheaper per person.
I've thought of this too. The best bet is to make two protective layers - one rectangular in cross-section, built with cinderblocks and a cheap roof, and a elliptical inside with a concrete shell, buried halfway into the ground. The concrete itself will have a recycled polyethylene exterior (as concrete is porous), and on top of that a thin layer of steel. The steel is constructed by helical wrapping around the elliptical tube, and welded together.
But still, it would be prohibitively expensive. However the pressure differential doesn't have to satisfy a vacuum - a near-vacuum condition is acceptable. 2-3% atmosphere is easy to maintain with smaller pumps, and would still lower drag by 97%.
Here's a take on the vac-train concept from OA; this particular example accelerates so rapidly I've added a gimbal system for the comfort of the passengers.
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Many thanks for the excellent post. That is exactly what I have been envisioning, put into words and drawing quite nicely.
Tethering to the sea floor would remove such a tube from wave-action; though ship-wrecks sinking on top of it could pose a potential problem.
I also envisioned the passenger compartments as being more cigar-shaped, with the passengers lying in a prone position. Wouldn't it be fun for a two-some to take a private trip to Europe from the East Coast, lasting maybe an hour, inside their own private passenger compartment where they are required to be lying down!
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