Author Topic: Global vactrain launch  (Read 8646 times)

Offline docmordrid

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Re: Global vactrain launch
« Reply #20 on: 01/21/2011 09:41 PM »
There are 3 maglev systems. The one NASA is looking at is Inductrack, which uses Halbach arrays for levitation. Inductrack I is for high speeds.

AIP Industrial Physicist article (PDF)
« Last Edit: 01/21/2011 10:02 PM by docmordrid »
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Offline go4mars

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Re: Global vactrain launch
« Reply #21 on: 01/21/2011 09:54 PM »
There are 3 maglev systems. The one NASA is looking at is Inductrack, which uses Halbach arrays for levitation. Inductrack I is for high speeds.

AIP Industrial Physicist article (PDF)

I wonder if this would be less expensive than designing a big, flyback 1st stage. 
Elasmotherium; hurlyburly Doggerlandic Jentilak steeds insouciantly gallop in viridescent taiga, eluding deluginal Burckle's abyssal excavation.

Offline docmordrid

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Re: Global vactrain launch
« Reply #22 on: 01/21/2011 10:08 PM »
As the article says - levitation is passive & propulsion could be either electronic or turbofan to get the payload well past suprrsonic, at which time a presumably smaller booster than normal could take over. How well this would work in the really-real world is up for grabs.

Personally, I think something like a SABRE powered flyback would be better, if for no other reason than the smaller infrastructure and the flexibility of taking off/landing most anywhere there's a long enough runway.
« Last Edit: 01/21/2011 10:11 PM by docmordrid »
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Offline space_man

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Re: Global vactrain launch
« Reply #23 on: 01/25/2011 02:58 PM »
Exactly the same way it gets today to maglev trains.

Panograph?

Pantograph would be "a bit" :D difficult to make work at these speeds.

In this case, it makes sense to install active magnets on the tube, leaving the train with passive coils. IOW: the tube pushes the passive train, not train propelling itself along the passive tube.

This way you dont need to supply the current to the train, you only need to supply it to the tube, which is stationary.

There are a few things I dont understand...

If the train pushes tube into space, while circling the tube at the same time, does it push magnetically on the tube, or does it do it by friction?

If it does so using magnets, then do you need flex-magnets?

If it does it using wheels and friction, then how much energy is lost to train rubbing against the tube?

How much tension force is in the flex piping once you extend it by 4.3%? You must account for elastic effects.

Offline gospacex

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Re: Global vactrain launch
« Reply #24 on: 01/25/2011 05:24 PM »
Exactly the same way it gets today to maglev trains.

Panograph?

Pantograph would be "a bit" :D difficult to make work at these speeds.

In this case, it makes sense to install active magnets on the tube, leaving the train with passive coils. IOW: the tube pushes the passive train, not train propelling itself along the passive tube.

This way you dont need to supply the current to the train, you only need to supply it to the tube, which is stationary.

There are a few things I dont understand...

If the train pushes tube into space, while circling the tube at the same time, does it push magnetically on the tube, or does it do it by friction?

Magnets. It's a maglev train.

Quote
If it does so using magnets, then do you need flex-magnets?

What are flex-magnets?

Quote
How much tension force is in the flex piping once you extend it by 4.3%? You must account for elastic effects.

Steel can't be stretched by that much. It needs to have extending sections.

Much more detailed engineering research is needed to figure out whether it is beneficial or detrimental to also keep the tube ring under a bit of tension.

Offline space_man

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Re: Global vactrain launch
« Reply #25 on: 01/25/2011 07:02 PM »
Exactly the same way it gets today to maglev trains.

Panograph?

Pantograph would be "a bit" :D difficult to make work at these speeds.

In this case, it makes sense to install active magnets on the tube, leaving the train with passive coils. IOW: the tube pushes the passive train, not train propelling itself along the passive tube.

This way you dont need to supply the current to the train, you only need to supply it to the tube, which is stationary.

There are a few things I dont understand...

If the train pushes tube into space, while circling the tube at the same time, does it push magnetically on the tube, or does it do it by friction?

Magnets. It's a maglev train.

Quote
If it does so using magnets, then do you need flex-magnets?

What are flex-magnets?

Quote
How much tension force is in the flex piping once you extend it by 4.3%? You must account for elastic effects.

Steel can't be stretched by that much. It needs to have extending sections.

Much more detailed engineering research is needed to figure out whether it is beneficial or detrimental to also keep the tube ring under a bit of tension.

It is this very "detailed engineering" or in other words "big red button to make it work" that concerns me the most.


You ask about flex magnets? Simple assume in your maglev every 4 meters is one superconducting magnet 10 meters in diameter through which your train passes, what happenes when we increase the separation distance by 4.3%? We lose confinement of the train, and especially since the train will be moving at higher and higher speeds this will be detrimental. A flex magnet would also increase by 4.3% to maintain stability.

Offline gospacex

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Re: Global vactrain launch
« Reply #26 on: 01/25/2011 07:50 PM »
Quote
Much more detailed engineering research is needed to figure out whether it is beneficial or detrimental to also keep the tube ring under a bit of tension.

It is this very "detailed engineering" or in other words "big red button to make it work" that concerns me the most.

Well, all "far into future" ideas are like this, be it space elevator, interstellar ships, or this proposal. If a proposal has no big problems to be overcome before it can be realized, then we'd be doing it already.

I am not pushing the global vactrain thing because I think it would be easier than space elevator, but because, unlike space elevator, it is not predicated on invention of super-strong materials. If such materials will be discovered, great. My position is, what if they will not be discovered? I want to play with idea which does not not need them.

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You ask about flex magnets? Simple assume in your maglev every 4 meters is one superconducting magnet 10 meters in diameter through which your train passes, what happenes when we increase the separation distance by 4.3%?

By this time the whole thing will be in orbit, and train can slow down relative to the tube. Actually, it can start slowing down much earlier, when tube just left dense air (say, at 10 km). At this height, the required growth is only 0.14%.

BTW, why "superconducting"? Inductrack, for example, uses ordinary Halbach arrays on one side, and metal coils on another (only some of them are powered, to propel the train).

Why "10 meters in diameter"? Haven't you seen maglev trains? They have nothing even close to such monster magnets, because they don't need them.

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