Space Elevator

[Agent11]

If the main hindrance to this sort of project is that no material is strong enough to sustain its own weight at this scale why not use a free floating segmented system?

It would be like thousands of zeppelins in a row, all could maintain position with gps and laser guidance, and you could use powerful magnetic fields and high speed catapults similar to the system on aircraft carriers for the delivery system.

The car accelerates and is 'passed' to the next where it then accelerates for the next pass.

 

[dawp]

I don't think it's so much we don't have the material, it's that we can't produce it in long enough lengths or in quantities needed.

I believe carbon nanotubes would is the material that will fit the bill.

 

[DominionSeraph]

Hydrogen/helium leaks, so it's not maintainable. Lifting capacity also depends on temperature, so you're going to have wild fluctuations vertically. You'd also never be able to maintain anything even close to the millimeter precision needed horizontally.

 

[Eureka]

Manufacturability. Those electric catapults are extremely expensive and heavy. You're not going to lift those with helium.

Carbon nanotubes are the most likely candidate. Even then we're limited by cost and objective; what's the point, especially with these costs?

 

[moonbogg]

Graphene ribbon could be used. After some googling, it seems that its just not economically feasible right now. You would need a lot of thick, expensive cable and current technology would allow a safety factor of 2 for the cable. Maybe thats good enough, but I wouldn't want to ride it.

 

[pandemonium]

This proposition, about having a segmented elevator, actually alleviates the issues I have with the highly sought after theory of a space elevator.

The issues currently with space elevator theories, aren't so much with regards to the capable materials that are strong enough, but are that they assume the amount of mass (e.g. the station) at, near, or beyond geostationary orbit, would be able to maintain gravitational force proportions against not only the weight of the descending cabling but it would need to maintain a strong, taught balance, for fluctuating atmospheric conditions, solar winds, radiation pressures, fluctuations in the Earth's and Moon's gravitational forces, and the Moon's traversing gravitational force changes. The financial magnitude at which to make this reasonable will be astronomically beyond any budget available, publicly or privately, I think.

I'd love to figure out the force required behind maintaining such a balance, but I'm stuck in equations with declination of gravitational force applied to the mass of the cabling with altitude changes. Once that's figured out, the altitude of geostationary orbit and mass for the station can be calculated and from there we can determine the requirements of cabling needed. If anyone can figure that out, be my guest, because I've been curious about this for a long, long time.

 

[Agent11]

I don't think payload would really be much of a concern at all. You could build an airship to carry any payload, it just would be expensive and large. Altitude would be, but it wouldn't be impossible to overcome I don't think.

Each segment itself would be modular as well, so very easy to maintain. Also could have portions of it tethered and powered from the ground, and from space. In the middle would be the tricky bits but I don't see any reason why it couldn't work.

The biggest problem would be surface area that is exposed to the jetstream I would think.. But I can imagine ways of working around that as well.

 

[gorobei]

oddly enough science fiction anime has addressed a couple of the main space elevator issues. gundam 00 has 3 elevators/towers connected to an orbital ring around earth.

solar power from the ring is used to power everything on earth as well as the high speed rail cars for the elevator. magneto hydrodynamic fluid in tubes running the length of the ring circulate at high speed to maintain centrifugal force and maintain ring orbit. counter weights and ballasts with adjustable lengths maintain the elevators cables connection to earth.

the main issue that comes up in the series is that any accident can result in a massive deluge of material and debris if the cables fail. therefore any elevator will likely have to be built in the middle of an ocean.

 

[yhelothar]

If the space elevator is docked to a satellite that's in geosynchronous orbit with the Earth, I would imagine that would take significant load off of the elevator.

 

[balsa model]

If the space elevator is docked to a satellite that's in geosynchronous orbit with the Earth, I would imagine that would take significant load off of the elevator.

If you imagine a little farther, you'll see that that satellite will be quickly pulled down from its geosynchronous orbit.
Geosynchronous orbit is the place where any mass with angular velocity matching Earth rotation will have its local weight (m*gloc) balanced by the centrifugal force (m*R*w^2). You can't upset this balance without upsetting the orbit.
Your space elevator has to be anchored to a satellite in an orbit *above* geostationary level. The part of the space elevator that is above this level will be pulling outwards.

Rocket science is easy: it's just a few Newton's laws.
Rocket engineering: now there is a challenge.
I don't want to sound pessimistic but.... the engineering issues are staggering, so... not in my lifetime.

 

[pandemonium]

If the space elevator is docked to a satellite that's in geosynchronous orbit with the Earth, I would imagine that would take significant load off of the elevator.

If you imagine a little farther, you'll see that that satellite will be quickly pulled down from its geosynchronous orbit.
Geosynchronous orbit is the place where any mass with angular velocity matching Earth rotation will have its local weight (m*gloc) balanced by the centrifugal force (m*R*w^2). You can't upset this balance without upsetting the orbit.
Your space elevator has to be anchored to a satellite in an orbit *above* geostationary level. The part of the space elevator that is above this level will be pulling outwards.

Rocket science is easy: it's just a few Newton's laws.
Rocket engineering: now there is a challenge.
I don't want to sound pessimistic but.... the engineering issues are staggering, so... not in my lifetime.

This is exactly what I was pointing out as being an inherent flaw with the theory of a space elevator.

 

[RobDickinson]

A space elevator plan I think has the earth end 'floating' and anchored to a counter weight outside of geosynch orbit.

 

[Agent11]

Imagine if instead of a station in orbit you had a massive airship above the jetstream at say 60+kilometers. You take the elevator to the air ship and then get catapulted off toward space.

The amount of energy needed to leave orbit at 60+ kilometers would be much less than the amount required to leave from sea level. You would only have another 40 or so kilometers left to go and gravity would be much weaker as you went.

Given that they are saving over half the fuel required to enter space they could even re enter at lower speeds and land directly on the high altitude airship base for refueling and resupplying.

This would probably be more feasible with current technology.. I wonder how lite you could build a nuclear reactor?

 

[harrkev]

The REAL reasons a space elevator will never happen...

1) Begin stuck next to strangers in an elevator for a couple of hours. The awkward silence to the 10th floor is NOTHING compared to this baby.

2) Hours of elevator music would cause anybody to kill themselves.

 

[balsa model]

... and then Health and Safety review panel would come back with a report that you also need a set of stairs, in case there is a fire.

 

[JTsyo]

Opposite and equal reaction. For the airship, it would be at equilibrium between weight and buoyancy, now you push something large up at a high velocity and your airship is going to break apart under the load. You make it strong enough to take it and it wouldn't lift off the ground.

 

[kevinsbane]

Geosync orbit is ~35,786 km above mean sea level. Atmosphere is approximately ~100km thick. Proposals to support the elevator with in-atmosphere means would support at most 100km, or about 0.3% of the mass of the space elevator.

The entire point of a space elevator is finding a way to hang a 36 000 KM strand of wire in place.

Any feasible proposals to "support" said strand up to 100km defeats the entire point of the space elevator - might as well build a "space tower". Build up towards space as opposed to coming down from space.