Space elevator vs space fountain

[todofwar]

So, which one gets built first/should be built first? 

Fountain Pros: 

Can be built with current materials

Can be built to any height 

Fountain Cons:

Active structure, need for constant power

Elevator Pros: 

Passive structure

Elevator Cons:

Currently impossible 

Have to go to geostationary

 

[PB666]

51 minutes ago, todofwar said:

So, which one gets built first/should be built first? 

Fountain Pros: 

Can be built with current materials

Can be built to any height 

Fountain Cons:

Active structure, need for constant power

Elevator Pros: 

Passive structure

Elevator Cons:

Currently impossible 

Have to go to geostationary

 

Where do you folks come up with these ideas

1. Elevator cons

No material
No means of elevaing the mass needed to make it, especially given no sufficiently strong material
The wire would pass through GSO with a counter mass outside to keep it GS, this would interfere with station keep at GSO.
No means of powering the elevator (conductor length exceeds limitation of powering, elevator would need to be self-powered, solar power would elevate very slowly, passengers would suffocate)
No means of stabilizing the wire against resonance created by surface winds.

2. Space fountain.

Completely and totally rediculous.
1. build a mountain about 20,000 feet taller than mount everest
2. build a mass accelerator in the mountain
3. at a 45 degree angle you have 15,000 meters x 1.414 = 21200 meters
4. You have a limitation on human acceleration of 8 g = 78 m/s

21200 =  1/2*78* t^2  t = 23 seconds

(78-9.8)*23 = 1600 meters per second - exact same problem with space planes. you still have another 6500 m/s to go and this only affords you 64,000 km, you still need about 25% more verticel kinetic energy to reach a burn point.

5. No current materials capable of building such a structure. Thestructure would have to be strong enough to contain a partial vacuum.

 

[todofwar]

I agree with your assessment of the elevator, but I don't think we're talking about the same fountain. A space fountain works by shooting a constant stream of magnetic particles that are then redirected by a bending magnet. The bending magnet is kept aloft by the extreme forces of redirecting the magnetic stream. Because of the physics of it, the actual materials encasing all this don't have to support themselves, they couple to the stream of superfast magnets which is what is actually keeping everything aloft. Now, you have a payload that also couples to this magnetic stream accelerate at 4g straight up, and the fountain is just tall enough such that the payload has enough kinetic energy to reach the geostationary point with nothing more than minor correction burns. 

Do both ideas sound ridiculous? Of course, but enough serious scientists and engineers are investigating them because of the incredible savings over current space launches. The elevator gets talked about the most (I'm a chemist and I sit in on so many seminars talking about carbon nanotube space elevators, which is ridiculous because carbon nanotubes are nothing but hype) but really, it's pretty much impossible until a major breakthrough in materials science. 

[fredinno]

Yeah, my favorite concept would be a skyhook https://en.wikipedia.org/wiki/Skyhook_%28structure%29

Combine a non-rotating skyhook with a very high-altitude airship, and you have a cheap way to get to space, at a fraction of a space elevator's cost to build, and is relatively safe, even if it fails (most will burn up the atmosphere).

[PB666]

11 hours ago, todofwar said:

I agree with your assessment of the elevator, but I don't think we're talking about the same fountain. A space fountain works by shooting a constant stream of magnetic particles that are then redirected by a bending magnet. The bending magnet is kept aloft by the extreme forces of redirecting the magnetic stream. Because of the physics of it, the actual materials encasing all this don't have to support themselves, they couple to the stream of superfast magnets which is what is actually keeping everything aloft. Now, you have a payload that also couples to this magnetic stream accelerate at 4g straight up, and the fountain is just tall enough such that the payload has enough kinetic energy to reach the geostationary point with nothing more than minor correction burns. 

Do both ideas sound ridiculous? Of course, but enough serious scientists and engineers are investigating them because of the incredible savings over current space launches. The elevator gets talked about the most (I'm a chemist and I sit in on so many seminars talking about carbon nanotube space elevators, which is ridiculous because carbon nanotubes are nothing but hype) but really, it's pretty much impossible until a major breakthrough in materials science. 

Same thing, magnetic particles have mass, very low mass btw which means they have alot of drag. So you still have to have a very high structure.

And BTW, ozone in the atmosphere is quite polar, it will accelerate in a magnetic feild.

https://en.wikipedia.org/wiki/File:Ozone_molecule.svg

ONce the ozone reaches the upper layers of the atmosphere it will react with hydrogen, nice fireworks but that completely destroyes the stream and the ozone, which would have the environmentalist at your doorstep. Oh, and you have another problem.. . . . . https://en.wikipedia.org/wiki/Ozone#Production....There is no such thing as a purely magnetic particles, throwing a stream of magnetic particles in motion would create electromagnetism and there would be an electrical component.

Serious engineers, I think not, may as a hobby. Carbon nanotubes are not hype, they have their place in nanomedicine and similar applications.

Don't forget the laws of energy conservation, if you have a payload of a ton you need something that produces 10,000 newtons of force (1 ton of weight) to keep it up against gravity. If you are going to accelerate against gravity you need 20000 newtons of force applied against a 2-D object, how big is that plate going to be a football field, 10 football fields, 100 football fields.

 

Edited April 6, 2016 by PB666

[Darnok]

I was thinking about https://en.wikipedia.org/wiki/Vactrain tunnel/cannon over Everest

In vacuum tunnel you could sped up and the higher this tunnel ends the better.

[todofwar]

Never said they were being paid to look into it, just that enough of the physics makes sense for it to be looked at academically. Ozone is magentic yes, but so is oxygen, yet you don't see people running particle accelerators concerned about accidentally concentrating oxygen close to their magnets. The electrical field that would be produced by the rapidly moving magnets is what you use to power the components of the structure at higher altitudes actually, so not a problem that they will produce electrical currents. We are not talking about atoms here, by the way, but micro scale particles. 

And not related but nanotubes have had no real use yet, or graphene, or bucky balls. Interesting forms of carbon, good fodder for grant money, but so far useless. I might be very bitter about this because of how much press they get despite no payoff, but seriously all that is much further away from real applications then people think. 

11 minutes ago, Darnok said:

I was thinking about https://en.wikipedia.org/wiki/Vactrain tunnel/cannon over Everest

In vacuum tunnel you could sped up and the higher this tunnel ends the better.

I was talking about https://en.wikipedia.org/wiki/Space_fountain. One of the other useful things about it, is that you can slowly raise its height, and once you are above a certain altitude it looks very promising as a high altitude launch platform, to avoid fighting the lower atmosphere. So you start charging enough to slowly raise the height further. 

[fredinno]

3 hours ago, Darnok said:

I was thinking about https://en.wikipedia.org/wiki/Vactrain tunnel/cannon over Everest

In vacuum tunnel you could sped up and the higher this tunnel ends the better.

Only problem is that when it hit the atmosphere, you get very high G-forces and atmospheric heating. That is, without building superstructures.

[PB666]

1 hour ago, fredinno said:

Only problem is that when it hit the atmosphere, you get very high G-forces and atmospheric heating. That is, without building superstructures.

Theoretically you could use rf before the object ejects and lasers afterwards to creat a vacuum hole in the atmosphere, the point however is the ship is limited to1600 m/s. So whats the point of doing it. Just by launch at 5000 meters affords a reduction in drag and demunition of the thermodynamic energy required tonreach orbit.

[fredinno]

On 4/6/2016 at 0:18 PM, PB666 said:

Theoretically you could use rf before the object ejects and lasers afterwards to creat a vacuum hole in the atmosphere, the point however is the ship is limited to1600 m/s. So whats the point of doing it. Just by launch at 5000 meters affords a reduction in drag and demunition of the thermodynamic energy required tonreach orbit.

It still limits you to hardened cargo. Which might actually make the savings from this system pointless, as the satellites will be more expensive, and have reduced capability.

Also, the diameter of the tunnel is also a serious limiting factor.

[Spaceception]

 

[fredinno]

35 minutes ago, Spaceception said:

 

Ooo, a new Kursesght Video! 

[lude]

What about mass drivers to get payload into or out of orbit?

Obviously not for passenger transport, but nuclear waste or stuff like that.