Aiming High – Will We Ever See a Space Elevator?

[Cripplecreek]

Artist rendering of Space Elevator. (Image courtesy of Japan Space Elevator Association.)

The space elevator concept relies on tethering an object to the ground and letting the rotation of the earth keep it up. Way up. Over 20 miles up.

The “elevators,” or climbing pods, would ride up and down the tether, taking cargo and people from the earth’s surface through the atmosphere and into the realm of near-zero gravity. From there, the payloads and people could launch into deep space to colonize other planets, mine for minerals—or snap some awesome selfies.

Talk about a lofty goal.

The space elevator concept has been around for over a hundred years and was more recently popularized by the venerable Arthur C. Clarke in Fountains of Paradise. However, it continues to be a dream.

But for every sci-fi reader who has twirled a weight around his or her head to mimic the seemingly simple concept of a space elevator and wondered why not, there may be an engineer shaking his or her head because that isn’t how it works.

 
Why an Elevator?

Leading the most recent initiative to bring the space elevator to life is Shuichi Ohno, chairman of the Japan Space Elevator Association (JSEA). Ohno, who presented at SOLIDWORKS World 2016, leads with what he considers the compelling economic reason for the space elevator. Rockets are such a waste, he said.

“If we are going to travel to space on a regular basis, we need a reliable and economic form of transportation,” said Ohno. “Anywhere from 75-90 percent of the weight of a rocket is consumed by fuel. Physics places a limit on how efficient a rocket can be, so we cannot rely on them as transportation.”

“But if we have a space elevator, we can travel to geosynchronous orbit or high-earth orbit relatively economically,” Ohno added. “If we were to build a space station there, flights to more distant destinations like Mars can be launched without having to overcome the gravitational pull of the earth.”

http://www.engineersrule.com/aiming-high-will-we-ever-see-a-space-elevator/

Interesting read.

In my opinion the engineering is different but not really tougher than engineering a rocket launch to mars and land a craft within a target area using a system of parachutes, rockets, and winches.

However as with many of these things, I think they're far more likely to come into being on mars or the moon or something.

[Elderberry]

Has any one calculated how much EMF will be generated by a Space Elevator/Tether?

Shuttle TSS missions

TSS-1R mission

Four years later, as a follow-up mission to TSS-1, the TSS-1R satellite was released in latter February 1996 from the Space Shuttle Columbia on the STS-75 mission.[6] The TSS-1R mission objective was to deploy the tether 20.7 km above the orbiter and remain there collecting data. The TSS-1R mission was to conduct exploratory experiments in space plasma physics. Projections indicated that the motion of the long conducting tether through the Earth’s magnetic field would produce an EMF that would drive a current through the tether system.

TSS-1R was deployed to 19.7 km when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation.[7]

Despite the termination of the tether deployment before full extension, the extension achieved was long enough to verify numerous scientific speculations. These findings included the measurements of the motional EMF,[8] the satellite potential,[9] the orbiter potential,[10] the current in the tether,[11] the changing resistance in the tether,[12] the charged particle distributions around a highly charged spherical satellite,[13] and the ambient electric field.[8] In addition, a significant finding concerns the current collection at different potentials on a spherical endmass. Measured currents on the tether far exceeded predictions of previous numerical models[14] by up to a factor of three. A more descriptive explanation of these results can be found in Thompson, et al..[15] Improvements have been made in modeling the electron charging of the shuttle and how it affects current collection,[11] and in the interaction of bodies with surrounding plasma, as well as the production of electrical power.[16]

[Oceander]

Has any one calculated how much EMF will be generated by a Space Elevator/Tether?

Shuttle TSS missions

TSS-1R mission

Four years later, as a follow-up mission to TSS-1, the TSS-1R satellite was released in latter February 1996 from the Space Shuttle Columbia on the STS-75 mission.[6] The TSS-1R mission objective was to deploy the tether 20.7 km above the orbiter and remain there collecting data. The TSS-1R mission was to conduct exploratory experiments in space plasma physics. Projections indicated that the motion of the long conducting tether through the Earth’s magnetic field would produce an EMF that would drive a current through the tether system.

TSS-1R was deployed to 19.7 km when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation.[7]

Despite the termination of the tether deployment before full extension, the extension achieved was long enough to verify numerous scientific speculations. These findings included the measurements of the motional EMF,[8] the satellite potential,[9] the orbiter potential,[10] the current in the tether,[11] the changing resistance in the tether,[12] the charged particle distributions around a highly charged spherical satellite,[13] and the ambient electric field.[8] In addition, a significant finding concerns the current collection at different potentials on a spherical endmass. Measured currents on the tether far exceeded predictions of previous numerical models[14] by up to a factor of three. A more descriptive explanation of these results can be found in Thompson, et al..[15] Improvements have been made in modeling the electron charging of the shuttle and how it affects current collection,[11] and in the interaction of bodies with surrounding plasma, as well as the production of electrical power.[16]

@Elderberry

What about nonconducting tethers?  Or tether systems designed to take advantage of these currents?

[Cripplecreek]

@Elderberry

What about nonconducting tethers?  Or tether systems designed to take advantage of these currents?

Exactly what I was thinking. Sounds like a great source of energy to me. If not it can be safely dissipated.

As far as non conductive material is concerned I'm not sure what non conducting material has the needed strength. Carbon has the strength but I believe its also a high resistance conductor.

[Elderberry]

Diamond tethers

A leading contender is a cable made of carbon nanotubes (CNTs), which have been produced in a lab with a tensile strength of 63 gigapascal (GPa) – about 13 times stronger than the toughest steel.

The maximum length of CNTs has been growing steadily since their discovery in 1991, with Chinese researchers reporting having produced one measuring half-a-metre long in 2013. The authors of the IAA report predict kilometre-long CNTs by 2022 and lengths sufficient for their concept design by the 2030s.

Meanwhile a new contender emerged in September when a team led by John Badding, a professor of chemistry at Penn State University in Pennsylvania, revealed in a paper published in the journal Nature Materials that they had created ultra-thin, “diamond nanothreads" that could prove even stronger and stiffer than CNTs.

(Nasa) (Credit: Nasa)

(Nasa)

His group began by compressing benzene to 200,000 times atmospheric pressure. When the pressure was then released very slowly the atoms appeared to re-form themselves into a new, highly ordered structure of pyramid-like tetrahedrons.

These shapes linked together to form ultra-thin threads highly similar in structure to diamond. While it is not possible to measure their strength directly because of their size, theoretical calculations suggest they could be harder and stronger than today’s hardest, strongest synthetic materials.

‘Reducing the risks’

“If we could learn to make materials based on diamond nanothreads or on carbon nanotubes perfect enough and long enough, science tells us they almost certainly have the strength necessary for a space elevator,” says Badding.

http://www.bbc.com/future/story/20150211-space-elevators-a-lift-too-far

[Cripplecreek]

Diamond tethers

A leading contender is a cable made of carbon nanotubes (CNTs), which have been produced in a lab with a tensile strength of 63 gigapascal (GPa) – about 13 times stronger than the toughest steel.

The maximum length of CNTs has been growing steadily since their discovery in 1991, with Chinese researchers reporting having produced one measuring half-a-metre long in 2013. The authors of the IAA report predict kilometre-long CNTs by 2022 and lengths sufficient for their concept design by the 2030s.

Meanwhile a new contender emerged in September when a team led by John Badding, a professor of chemistry at Penn State University in Pennsylvania, revealed in a paper published in the journal Nature Materials that they had created ultra-thin, “diamond nanothreads" that could prove even stronger and stiffer than CNTs.

(Nasa) (Credit: Nasa)

(Nasa)

His group began by compressing benzene to 200,000 times atmospheric pressure. When the pressure was then released very slowly the atoms appeared to re-form themselves into a new, highly ordered structure of pyramid-like tetrahedrons.

These shapes linked together to form ultra-thin threads highly similar in structure to diamond. While it is not possible to measure their strength directly because of their size, theoretical calculations suggest they could be harder and stronger than today’s hardest, strongest synthetic materials.

‘Reducing the risks’

“If we could learn to make materials based on diamond nanothreads or on carbon nanotubes perfect enough and long enough, science tells us they almost certainly have the strength necessary for a space elevator,” says Badding.

http://www.bbc.com/future/story/20150211-space-elevators-a-lift-too-far

American physicist and science fiction writer Robert L Forward described carbon nanofiber hextube in great detail in his sci fi novel "Saturn Rukh". He even introduced the company he co-founded "Tethers unlimited" http://www.tethers.com/ before his death in 02.

[Oceander]

Perhaps nanotubes do not have to be single stranded the entire length, but can be woven together like rope.  That way, the failure of a single strand will not automatically compromise the entire structure. 

[Idiot]

Perhaps nanotubes do not have to be single stranded the entire length, but can be woven together like rope.  That way, the failure of a single strand will not automatically compromise the entire structure.

I can't even imagine the stress on that thing.  Atmospheric winds, etc.

Ok....you go first. 

[Oceander]

I can't even imagine the stress on that thing.  Atmospheric winds, etc.

Ok....you go first. 

Just keep running em up the flagpole to see what happens!

[Cripplecreek]

Perhaps nanotubes do not have to be single stranded the entire length, but can be woven together like rope.  That way, the failure of a single strand will not automatically compromise the entire structure.

Exactly how Robert Forward described it.

As an indication of the kind of stresses he wanted his carbon fiber "Hexcord" to endure he was using it in his sci fi as a means of steering and braking for spacecraft. Basically they would fire an anchor into a small moon and the hextube working in conjunction with a reel and drag system. It allowed much sharper turns and faster deceleration than rockets will allow. It could also be used for acceleration.

In fact a drag system could be used with the space elevator concept. Anyone who has ever done any fishing understands how drag works with a fishing line. Your elevator would probably never be a static height. As a payload approached the top the centripetal force would be increasing and you could allow the elevator drag to slip and prevent reaching the breaking strain.

[Elderberry]

The physics of the space elevator
P. K. Aravind
Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609

Received 1 May 2006; accepted 10 November 2006

https://pdfs.semanticscholar.org/d402/ba5f97884b7398ae2a1ff79136f9c1a03993.pdf

[Oceander]

The physics of the space elevator
P. K. Aravind
Department of Physics, Worcester Polytechnic Institute, Worcester, Massachusetts 01609

Received 1 May 2006; accepted 10 November 2006

https://pdfs.semanticscholar.org/d402/ba5f97884b7398ae2a1ff79136f9c1a03993.pdf

Any chance of getting the Cook's tour version?

[Elderberry]

Any chance of getting the Cook's tour version?

If this, and that,an that,and also that, then mathermaticicully serpozudley dewable. Oh! and I fergot to include dat.

So some group will probably convince our gullible government officials to give them gobs of our hard earned tax money, and even more. To squander, and eventually give up.
@Oceander

[Oceander]

If this, and that,an that,and also that, then mathermaticicully serpozudley dewable. Oh! and I fergot to include dat.

So some group will probably convince our gullible government officials to give them gobs of our hard earned tax money, and even more. To squander, and eventually give up.
@Oceander

Seems to me that proof of concept might be doable by a private company, without government money.  The bigger issue might be whose palms need greasing to get launch and construction permission, and where would the damned thing come down if it failed.

[Oceander]

There's also the issue of space debris in orbit. One unfortunately aimed nut from a burned up second stage and that tether might be cut in half. 

[Suppressed]

Ever since 9/11, I've begun to think that the huge investment would be extremely vulnerable.

[Oceander]

Ever since 9/11, I've begun to think that the huge investment would be extremely vulnerable.

At what point?  Ground facilities can be secured, so the threat would be to the tether itself, but hitting that would require resources that only an established nation-state - like Iran - could field.  A permanent no-fly Zone at least 50 miles wide, with immediate shoot down for any aircraft inside the zone should take care of 9/11 type attacks.

[Joe Wooten]

At what point?  Ground facilities can be secured, so the threat would be to the tether itself, but hitting that would require resources that only an established nation-state - like Iran - could field.  A permanent no-fly Zone at least 50 miles wide, with immediate shoot down for any aircraft inside the zone should take care of 9/11 type attacks.

A missile could also take it out. Bad actor nation states would have to be credibly told an attack on the tether would bring a retaliation that would lay their country to waste.

[Cripplecreek]

At what point?  Ground facilities can be secured, so the threat would be to the tether itself, but hitting that would require resources that only an established nation-state - like Iran - could field.  A permanent no-fly Zone at least 50 miles wide, with immediate shoot down for any aircraft inside the zone should take care of 9/11 type attacks.

Yeah I was thinking the same. It would certainly be no less secure than any other rocket launch facilities. It would be a multinational project with many nations with a vested interest in securing it.

I think the greatest danger is space junk. It will be alleviated eventually but unfortunately I doubt it will be taken seriously till we lose a crew.

[Oceander]

Yeah I was thinking the same. It would certainly be no less secure than any other rocket launch facilities. It would be a multinational project with many nations with a vested interest in securing it.

I think the greatest danger is space junk. It will be alleviated eventually but unfortunately I doubt it will be taken seriously till we lose a crew.

I was thinking about that.  Any thoughts on whether it might be possible to use something like a huge block of aerogel to catch the small space junk (the stuff that's really dangerous because you can't see it until it punches a hole in you) and then once a block is sufficiently full, deorbit it so that the block and all the captured junk burns up on reentry. 

[Elderberry]

Perhaps nanotubes do not have to be single stranded the entire length, but can be woven together like rope.  That way, the failure of a single strand will not automatically compromise the entire structure.

The first seed cable may need to be a single strand, or at least, a very finely wound cable.

Cable seeding design

Bradley C. Edwards, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia proposed that, if nanotubes with sufficient strength could be made in bulk, a space elevator could be built in little more than a decade, rather than the far future. He proposed that a single hair-like 20-ton 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity. Then, progressively heavier cables would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass and strength. This is much the same technique used to build suspension bridges. The length of this cable is 35,786 km or 35,786,000 m. A 20-ton cable would weigh about 1.12 grams per m.

https://en.wikipedia.org/wiki/Space_elevator_construction

[Smokin Joe]

Exactly how Robert Forward described it.

As an indication of the kind of stresses he wanted his carbon fiber "Hexcord" to endure he was using it in his sci fi as a means of steering and braking for spacecraft. Basically they would fire an anchor into a small moon and the hextube working in conjunction with a reel and drag system. It allowed much sharper turns and faster deceleration than rockets will allow. It could also be used for acceleration.

In fact a drag system could be used with the space elevator concept. Anyone who has ever done any fishing understands how drag works with a fishing line. Your elevator would probably never be a static height. As a payload approached the top the centripetal force would be increasing and you could allow the elevator drag to slip and prevent reaching the breaking strain.

Wouldn't the structure accelerate on the sunward part of the orbit and decelerate on the outbound segment? Instead of being at a truly stable orbit, it would be leading or trailing it's anchor point depending on which part of the orbit it was in.

[Elderberry]

Also carbon nanotubes are electrostrictive. Their lengths are changed by electric fields.