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Bring the vacuum to you...

Posted by: Eivhen - Tue Aug 24, 2004 6:34 am
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Bring the vacuum to you... 
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Post Bring the vacuum to you...   Posted on: Tue Aug 24, 2004 6:34 am
Hey guys! I haven't posted here or anything for some time but I did come up with an interesting idea a few days ago that I thought I might run past the experts here at X Prize.

The idea is simple enough: bring space to you in order to bring you to space.

Let me illistrate with this image. (please excuse my lack of artistic talent! :oops: )

Image

The idea is that if you could suck out all the air in a.....straw if you will...into space that you could launch spacecraft with total disregard to the friction that air causes on a craft lifting off into space thus dramatically lessening the energy cost required to exit earth's atmosphere. Recapture mechinisims could even be installed to allow eaiser re-entry without having to worry about protective (and usually expencive) heat shielding.

You could even utilize a varity of launch platforms. From Magnetic Repulsion to standard chemical based rockets. But what I wanted to know besides it's workability was if compressed air could be used to thust the vehicle (inside the "straw") into space in the way a cannon propells lead balls. Would the Air push the craft as it attempts to exit into the vacuum?

It's just, I have never ever heard about anyone else proposing anything like this before and wanted to know what you people thought.
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Post    Posted on: Tue Aug 24, 2004 7:05 am
You seem to need a tower having an altitude of 100 km - that may be a problem of statics. And gravity may cause the tower to collapse before it's ready.

But your idea seems to include another idea - shooting a spacecraft to space like a bullet is shot by a gun or a cannon. It's stimulating the question too wether it will increase the thrust and is possible to launche a spacecraft conventionally out of a tube-like tower of an altitude of let's say 100 meters. Partly it may be underground.

Magnetic and electromagnetic launch - what thrust realistically is to be expected?



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Post    Posted on: Tue Aug 24, 2004 10:52 am
Something vaguely similar has already been designed by Startram for magnetically accelerating vehicles to orbital velocities:-

http://www.startram.com/file/str-1.pdf

A 1000km long evacuated tunnel, terminated by a 30km-high magnetically levitated ramp. Talk about mega-engineering!! :shock:


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Post    Posted on: Tue Aug 24, 2004 11:03 am
When I was little, we used to go to a chain store (C&A) that kept all of its money locked upstairs for security. The cashier in the store stuffed your money in a little capsule which was shot up a vacuum tube to the staff upstairs. Your change was then fired back down to you in another capsule. I used to think it was cool. Sadly I still do and had a similar idea to Eivhen. Unfortunately I think it would take far more energy to pump out the tube than to launch a rocket :lol:

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Post    Posted on: Tue Aug 24, 2004 5:30 pm
Yeah....I was thinking about how gravitational stresses would probably bring it down. One way to counter-act that possibly would be to have a coupple weights attached to the space-end of the tube by very long cable. The centripetal force of Earth spinning would pull the weights out away from Earth thus pulling the Tube up aswell holding it errect.

And in regards to luke.r :


Quote:
Unfortunately I think it would take far more energy to pump out the tube than to launch a rocket


You could use a number of ways (aka solar, nuclear, wind) to power the air pump that are impossible to employ in rocketry.(more specificly, leaving earth's atmosphere.) So even if it did take as much energy as a normal rocket, the energy would be vastly cheeper then that of a chemical rocket.

So does anyone know how much air pressure it would take to launch a vehicle of lets say....a moddest 2 tons?


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Post    Posted on: Tue Aug 24, 2004 9:32 pm
There was a loooong discussion about this type of open pipe on the New Mars forums (Mars Society messageboards)

Long story short: very probably impossible to do... Stresses are too big, gas doesn't behave that way etc.

It was a rather drawn-out discussion, the originater of the idea kept asking: 'but what if...'
A guy with a physics-degree repeated again and again why he thought it was not feasible, almost 'till he got crazy :)

I'll try and find the link.


Last edited by Rxke on Tue Aug 24, 2004 9:42 pm, edited 2 times in total.



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Post    Posted on: Tue Aug 24, 2004 9:40 pm
http://www.newmars.com/cgi-bin/ikonboard/ikonboard.cgi?s=c5be9c0e94ca4b516483a5841f0fc04d;act=ST;f=5;t=96

Hmmm.. Not quite the same thing, but similar no-go's.

There was an even more elaborate follow-up...

http://www.newmars.com/cgi-bin/ikonboard/ikonboard.cgi?s=c5be9c0e94ca4b516483a5841f0fc04d;act=ST;f=5;t=100


Read if you got *plenty* of time! :D


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Post    Posted on: Wed Aug 25, 2004 3:09 am
:evil: I thought that I finally had an idea of my own! Arrrg!

But isn't it funey how multiple people can have the same random idea?

Oh well...I guess I did have my doubts. And even if something could be built like it, it's not like it ever would with the many other already-though-of-and-brainstormed-about ideas theory-ized or otherwise that are much more realistic in terms of today's (general term) global economy.

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Post    Posted on: Wed Aug 25, 2004 5:41 am
Don't get too discouraged. Even if you don't have a brilliant idea, you can still find ways to change the world. ;)


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Post    Posted on: Wed Aug 25, 2004 8:26 am
It's good to have big ideas. Let the boffins worry about the details, they are always looking for reasons why things can't be done. I suspect sometimes they can't see the wood for the trees! Science often lags decades behind what fiction writers prophesise (is that right!?).

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Post    Posted on: Fri Aug 27, 2004 1:26 pm
The idea is reminding me a little bit to one of the water-launch concept of one of the XPRIZE teams - may be it was Interorbital who has left the competition.

I didn't completely understand their explanation. They are talking about a big bubble created at ignition beneath the rocket but I don't know wether they are using this bubble to get additional thrust.

The very small similarity to Eivhen's idea is that there is a kind of pressure reducing process - the bubble of gases created at ignition removes the water that is causing pressure.

But there is another academical possibility. The tube Eivhen is thinking of could be a tube in the water going down to the ground. The water can easyly be removed. Then the spacecraft might perhaps be launched like a bullet is shot out of a gun. Perhaps water can assist if it is beneath the rocket at launch.

Sounds ridiculous to me myself but might be a realistic derivative of Eivhen's thoughts.

What to think about this?



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Post    Posted on: Fri Aug 27, 2004 1:58 pm
It seems to me a space elevator would be easier. :)


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Post    Posted on: Fri Aug 27, 2004 3:42 pm
Why?

The difficulties to build a "tube" within water are depending on the location. If oit is somewhere on the shelf of a continent the tube won't be longer than 200 meters, I think. Grounds as deep as 4000 meters are found ouside the continental shelf only. There it might be possible to use tubes having large extra-tubes filled with air or light gases. The tubes might be anchored at the ground.

I didN#t find out yet if Interorbital has in mind what I am thinking too but the water is cooling the spacecraft. So if at ignition water is allowed to fill the tube it might giv additional thrust - especially if the flame of the nozzels are evaporting it to gas immediately. The water also would be cooling the tube and reduce any damages caused by the flames.

The major question to me seems to be if a rocket can be launched sufficient exactly to use a tube without destruction, loss of acceleration and if a tube really might have advantages - to repeat my former words: I'm trying to derive something realistic from Eivhen's idea only but I don't say that it is advantageous.



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Post    Posted on: Sat Aug 28, 2004 5:34 am
If you could build the tube.... You could build a lot of things.

Last time I checked a rocket loses about 1/4 of its acceleration to atmopheric drag. That is a lot of rocketfuel.

The height of the exit of your tube limits how fast you can exit it. If its under 10km you can't be travelling at more than a mach or two.

If the exit is really high, then build an elevator.

Anything that got rid of the air would be a big advantage.

On the other hand the tube could be created by some sort of laser that made the air want to be somewhere else. The rocket would have to stay inside that beam very carefully, but you would already have an excellent guidance laser.

If the atmosphere drag issue could be dealt with a meaningful (large payload) SSTO could be born. The atmosperic drag is precisely the massive loss that makes useful SSTO's to hard at the moment.

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Post    Posted on: Sat Aug 28, 2004 5:44 pm
idiom wrote:
On the other hand the tube could be created by some sort of laser that made the air want to be somewhere else. The rocket would have to stay inside that beam very carefully, but you would already have an excellent guidance laser.


...and a nice big hole running the length of your ship. Any laser that's powerful enough to push air out of the way:
1) sucks more energy than we could get ahold of without building a Dyson Sphere (which would eliminate the entire problem) and
2) can melt even the highest grade mirrors (which are the only things that are relatively impervious to a laser beam).

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