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Magnetically levitated space elevator to low-earth orbit (2001) [pdf]

125 points by fosk 2y ago

buildbot 2y ago
Cooling a 200km loop with liquid helium sounds more than moderately difficult! Neat idea but not particularly possible given current material science as always seems to be the case with space elevators.
- eppp 2y ago
  How cold would the pipe be in space if it was shaded? Wouldnt that cut the energy needed by a bit?
  - perihelions 2y ago
    It's more or less impossible to shade a space elevator because the (hot, radiant) earth spans a full hemisphere of its field of view and the sun wanders most of the opposite one. No way to passively reach cryogenic temperatures—let alone the deep-cryogenic ones demanded by high current-density superconductors.
- punnerud 2y ago
  What about using Starship or similar to move the coolant up, then let it “fall” down? Once you have the elevator operated some of the transportation could be used for refueling coolant. And you start it from space and gradually lower it down to earth.
  - ben_w 2y ago
    I don't know why you think that would help? If we could build this at all, we could build it on the ground, then just switch it on (gradually) and it would float, and if we needed to get consumables up, they can be pulled up on a winch like any other payload to space. But also, I don't know why you think Starship is the right category for a solution; the structure in this paper is 200 kilometers in size (it says altitude, but for magnetic repulsion the best separation distance is a constant factor of the size before your get performance issues), whereas a fully stacked Starship is about 0.12 - 0.15. It would be like trying to refuel a 747 in flight with an personal selfie drone.
    - punnerud 2y ago
      The Starship was only for moving coolant, not as part of the elevator. I was thinking you probably have to have extra payload to stop the end. And that it then would be better to start from the top, than from bottom
      - ben_w 2y ago
        I can't visualise what you're trying to suggest. "Stop the end"?
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IncreasePosts 2y ago
(2001). I'm curious what has changed in this space since then.
- hinkley 2y ago
  I believe the test tether someone took up burned itself to a crisp. The magnetic flux it experienced from the earth was much more intense than their math predicted. That’s the last I heard.
  - dredmorbius 2y ago
    Do you have any idea which mission that was? Wikipedia has a listing, if that helps: <https://en.wikipedia.org/wiki/Space_tether_missions https://en.wikipedia.org/wiki/Space_tether_missions>
    - throw310822 2y ago
      TSS-1R mission, 1996 "TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation." "Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three"
      - dredmorbius 2y ago
        Thanks, I seem to remember that vaguely. I've also had the idea for a while (probably inspired by that mission) that any actual space elevator would be hugely influenced by magnetic and electrical influences, becoming a tremendously long conductor and/or static-charge accumulator. You'd probably want it to be exceptionally well grounded, and want to take precautions embarking or disembarking.
      - hinkley 2y ago
        What I was never clear on is whether that makes them more interesting or less realistic.
PaulHoule 2y ago
How is this different from https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop ?
- marcosdumay 2y ago
  There's no dynamic exchange of forces between moving objects on this one, just some current flowing through wires.
- datadrivenangel 2y ago
  The Launch loop uses the momentum of a rotating cable to keep the system up. This space elevator uses super conducting magnets to levitate against the earths magnetic field. It's like a gyroscopic force versus an electromagnet: they're both forces, but one is caused by mechanical movement versus the other which is caused by magnet fields.
- ben_w 2y ago
  This is supported by long-range magnetic pressure over the entire structure, with some (but not all) of that pressure coming from Earth's own field, and has no moving parts (other than the charge carriers). A launch loop could be short-range magnetic or electric pressure between the cable and the sheath, Earth's field is not important and it would also work on a body with no magnetic field, and it mostly functions by being a very big moving part surrounded by a vacuum chamber.
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JumpCrisscross 2y ago
NbTi has a critical temperature below 10K and generate fields of around 10 T [1]. The paper contemplates a 2T field. Could CeOFeAs permit cooling with hydrogen [2][3]? [1] https://en.m.wikipedia.org/wiki/Niobium%E2%80%93titanium https://en.m.wikipedia.org/wiki/Niobium%E2%80%93titanium [2] https://www.sciencedirect.com/science/article/abs/pii/S0921453413002529 https://www.sciencedirect.com/science/article/abs/pii/S09214... [3] https://en.m.wikipedia.org/wiki/High-temperature_superconductivity https://en.m.wikipedia.org/wiki/High-temperature_superconduc...
- vinnyvichy 2y ago
  You might be better off with scaling FeSe or waiting for improvements in that class. you can use LN2 (H2 leaks are not just inevitable,large scale deployments of LN2 cooling already exist)
al_borland 2y ago
I seem to remember reading about this in Popular Science around that time. Of all the things I saw in that magazine, the space elevator made of carbon nanotubes was always the one that stuck with me. Though I seem to remember PopSci taking about harnessing an asteroid, or something, and putting it geosynchronous orbit, as a means to create the top anchor point. 25 years later, it seems just as far fetched.
- worldsayshi 2y ago
  Although we have come much further with carbon nanomaterial. I wonder how close we are to achieving continuous fabric.
  - more_corn 2y ago
    We’re about 20 years away. Always will be.
- anytime5704 2y ago
  This seems like a great way to accidentally cause another global extinction event. I’m probably overestimating the size of the anchor.
  - tadfisher 2y ago
    The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.
    - askvictor 2y ago
      Depends where the tether breaks. If it's somewhere along the middle, then the Earth-side section would fall to Earth. KSR's Mars trilogy examines the impacts (pun intended) of this.
      - 2y ago
stretchwithme 2y ago
How is the elevator car in a space elevator accelerated horizontally? That's what reaching orbit is, right? Horizontal acceleration? The car starts out on the ground at 465m/s. It has to accelerate to 11,068 km/h. What makes it accelerate? The cable, without any force applied to it anywhere? Or is there a rocket on that car? To put mass into orbit, you have to accelerate that mass. And do it without decelerating the elevator. There are no free lunches.
- JumpCrisscross 2y ago
  > How is the elevator car in a space elevator accelerated horizontally? Momentum transfer from the cable, which is attached to an orbiting counterweight. In this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field. In general one boosts the counterweight directly or, more practically, by sending things down [1]. [1] https://space.stackexchange.com/questions/22447/how-will-the-angular-momentum-of-a-space-elevator-be-preserved https://space.stackexchange.com/questions/22447/how-will-the...
  - schiffern 2y ago
    This paper's design has no orbiting counterweight, and only reaches an altitude of 200 km. A launch loop can harvest energy and momentum from the rotor to accelerate payloads, but I don't see any such mechanism here.
    - JumpCrisscross 2y ago
      > This paper's design has no orbiting counterweight Which is why I say I “in this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field.” The cable is an electrostatic counterweight because we’re using electromagnetism, not the comparably weak gravitation.
      - schiffern 2y ago
        Problem is "some of the momentum" isn't nearly enough to reach orbit (climbing the tower only gains you 3% of orbital speed, or 0.1% the kinetic energy), and there's no hint of a mechanism that's supposed to accelerate a payload the rest of the way to orbital speed.
lionkor 2y ago
Or, you know, use a rocket...? I dont see an issue with Hydrogen Oxygen rocket propellants at all.
- mlyle 2y ago
  The annoying things with propellants is that you need to use them to lift more propellants. The rocket equation is not kind. Coming up with some way that lets us waste more mass will push aerospace away from such an exotic set of technologies towards more mainstream use. It is only the fact that space flight is barely possible that makes it so hard.
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codesnik 2y ago
somewhat related concepts: Space fountain and and Launch loop https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop
spacebacon 2y ago
Several prompts later … The gap between current material science and the required advancements for constructing a magnetically levitated space elevator is significant. Let's break down the key areas where advancements are needed and assess the current state compared to the required state: 1. Superconducting Materials Current State: NbTi Superconductors: NbTi (Niobium-Titanium) superconductors are among the most common, with critical temperatures around 9-10 K. They are widely used in MRI machines and particle accelerators. NbTi can sustain high current densities and generate substantial magnetic fields, but only at very low temperatures maintained by complex and costly cryogenic systems. Required State: Higher Temperature Superconductors: For a space elevator, superconductors that can operate at higher temperatures would reduce the need for extensive cryogenic cooling, thus making the system more practical and less costly. Currently, high-temperature superconductors (HTS) exist (like YBCO - Yttrium Barium Copper Oxide), which can operate above 77 K (the boiling point of liquid nitrogen), but they are not yet produced in long, high-quality, and affordable lengths suitable for large-scale engineering projects. Gap Analysis: The primary challenge is to develop superconductors that can operate at higher temperatures with sufficient current densities and stability. The current material science has not yet achieved a commercially viable production of long-length HTS with consistent quality and performance required for such applications. 2. Carbon Nanotubes and Advanced Fibers Current State: Carbon Nanotubes (CNTs): CNTs are known for their extraordinary tensile strength and low density, making them ideal candidates for space elevator cables. However, the production of long, defect-free CNTs with consistent properties remains a significant challenge. Current production techniques yield short lengths with varying qualities, and scaling up these methods while maintaining material integrity is difficult. Required State: Mass Production of High-Quality CNTs: For a space elevator, extremely long CNTs or similarly strong materials are required to construct a cable that can withstand the enormous stresses involved. These materials must be lightweight yet possess ultra-high tensile strength and stability over long periods. Gap Analysis: The major hurdle is the ability to produce continuous lengths of high-quality CNTs or alternative advanced fibers at a commercial scale. The technology for producing and manipulating these materials at the necessary scale is still in its infancy. 3. Structural Materials and Stability Current State: Composite Materials: Current composite materials, including carbon fiber composites, offer high strength-to-weight ratios. However, they are not yet capable of withstanding the specific stress and environmental conditions required for a space elevator, particularly in terms of radiation resistance and thermal stability. Required State: Advanced Composites and Alloys: Materials need to be developed that can endure the harsh conditions of space, including temperature extremes, radiation, and micrometeorite impacts, while maintaining structural integrity over potentially very long periods. Gap Analysis: Development is needed in creating materials that not only provide the necessary strength and durability but also can be manufactured and maintained at a reasonable cost. Improvements in radiation shielding and thermal management materials are also required. 4. Cooling and Power Systems Current State: Cryogenic Cooling: Current cryogenic systems can maintain superconductors at low temperatures, but they are heavy, complex, and energy-intensive. They are impractical for continuous, large-scale applications like a space elevator. Required State: Efficient Cooling Solutions: More efficient and lightweight cooling systems are required to maintain superconductors at operational temperatures without prohibitive power consumption. Alternatively, development of superconductors that operate at higher temperatures, requiring less intensive cooling, would be beneficial. Gap Analysis: Significant innovation is needed in both cooling technology and power systems to make a space elevator feasible. The challenge is to achieve efficient, reliable, and cost-effective solutions that can be integrated into the elevator structure. Summary The gap between current capabilities and the required advancements is substantial. While we have foundational materials and technologies, such as NbTi superconductors and carbon nanotubes, they are not yet developed to the extent necessary for practical use in a space elevator. Advances in high-temperature superconductors, scalable production of high-quality carbon nanotubes, and the development of lightweight yet strong structural materials are critical. Material science must progress significantly in these areas to move closer to realizing the concept of a magnetically levitated space elevator. This will require substantial research, development, and potentially novel breakthroughs in materials engineering and related technologies. The timeline for achieving these advancements is uncertain, and it could span several decades.
la64710 2y ago
What about the birds and the planes flying into the elevator cables? Is any othe thinking about it? Where do these crazy ideas come from? And what happens when they break and the cables fall to the earth? time we start thinking long term impact on the planet and its life for our ideas.
- kimixa 2y ago
  There's already plenty of other things of a similar scale in the path of birds and planes currently. Such as other planes. But these being stationary probably makes them even easier to avoid.
- tadfisher 2y ago
  A Starship produces 76,000 metric tons of CO2-equivalent per launch, which is going to be far more dangerous to the birds in the long term.
mikewarot 2y ago
If we're pushing "out of the box" ideas, why not just use hydrogen balloons to hold up a railgun for the first 20,000 meters of altitude? The ambient pressure at the end would be about 1/10th of that at sea level. You could have outriggers with a very thin high voltage power line to enable station keeping via thrusters (repurposed quadrotor parts?) I wouldn't be surprised it the ambient electrostatic field from the atmosphere were sufficient to power station keeping, or at least some of the instrumentation. If that works, I'm sure they could extend it to twice as long, almost into space.
- monkeyfun 2y ago
  Relatedly, have you ever heard of skyhook? Not the CIA one but the orbital infrastructure concept -- lets you literally just take a supersonic capable plane with no rocket engines whatsoever into space. Always love that concept with how it's actually engineer-able with current materials and sounds like it shouldn't work until you look closely.
  - metadat 2y ago
    This? https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure) Interesting idea, but if I'm understanding correctly, how do you stop the thing you hooked from swinging around and back down? Would you need to reel in 50 miles or whatever of cable?
    - ben_w 2y ago
      You can just let go of it when it's high enough, it picks up (ground) speed on the way up.
- pdonis 2y ago
  The main cost of getting to low Earth orbit isn't gaining altitude, it's gaining speed. Even if you could levitate a spacecraft to, say, 200 km altitude at zero cost in energy, you would still need about 97% of the energy to get it to orbital speed, that you would have needed to launch it from the Earth's surface.
anonu 2y ago
this was a nice idea 20+ years ago but never materialized - literally. I don't think the materials required - specifically carbon nanotubes - were created that could support the tensions needed for such an idea.
dekhn 2y ago
There's a simple point about space elevators that most people ignore. We would only build a space elevator if it made economic sense. Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. Even more importantly, if we had access to the materials necessary to build space elevators, there are other, much more pressing terrestrial needs that would use up all those materials long before somebody tried to build an elevator. No matter how much fun it is to contemplate their existence, nobody has come up with a justification for the necessary investment required to build and operate one.
- darby_nine 2y ago
  > Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. This doesn't seem that difficult given the potential value of mining. I suspect terrestrial politics would dominate this conversation—access to said elevator is far more interesting than any collective concern, and humans as they stand are not capable of resolving collective concerns on any level.
  - dekhn 2y ago
    Trillions+ in mining value? What exactly are you proposing mining (platinum seems the most likely, IIRC my D&D)? remember that new sources affect the supply, which changes prices significantly, so it would have to be basically unobtanium to be worth it. And remember, since you developed all that tech just to make the space elevator... most of the mining you did is probably obsolete.
    - ben_w 2y ago
      Even aluminium gets you to a trillion dollars in 6 years. https://en.wikipedia.org/wiki/List_of_countries_by_aluminium_production https://en.wikipedia.org/wiki/List_of_countries_by_aluminium... * Calculation: http://www.wolframalpha.com/input/?i=1%20trillion%20USD%20%2F%20%28aluminium%20price%20%2A%2064%20million%20tons%20per%20year%29 http://www.wolframalpha.com/input/?i=1%20trillion%20USD%20%2... * Old data, China has rapid growth in this sector and is now about 42 megatons/y, but that just changes the result from rounding down to 6 years to rounding up to 6 years: https://www.reuters.com/markets/commodities/china-2023-aluminium-output-hits-record-high-growth-rate-slows-2024-01-17/ https://www.reuters.com/markets/commodities/china-2023-alumi...
Animats 2y ago
Superconducting tapes have become much better since 2001. Can you levitate a superconducting tape against the earth's magnetic field right now? A small scale demo should be possible.
vinnyvichy 2y ago
https://youtu.be/gQjbzuOA2mU https://youtu.be/gQjbzuOA2mU (2024) Why physics favor Mass Drivers over heavy lift rockets guy's voice similar to Bret Victor, (R&Deployment) economics slightly better than space elevator-- you can also use SC magnets but in easier config, repurpose Hyperloop research etc
pfdietz 2y ago
This was an extension of the MCKESR (Magnetically Confined Kinetic Energy Storage Ring) concept Hull was exploring at ANL. The idea here is a ring-shaped flywheel where the centripetal force is supplied by magnetic forces rather than strength of the rotating ring. The advantage is that the stored energy per mass of ring + magnets scales linearly with radius, unlike in a conventional flywheel where (by the virial theorem) the ratio is limited by a constant factor proportional to the strength of the flywheel material divided by its density. The original MCKESR concept had a ring-shaped conductor orbiting in a magnetic field, but a later concept had a chain of ferromagnetic objects being attracted magnetically. The latter was kept passively stable by alternating segments of magnets, one segment where the attraction was stable radially and unstable vertically, the next the opposite. If the ring was moving in the right speed range this would cause dynamic stability in both directions. This Alternating Gradient principle is used (via magnetic forces on moving charged particles) to focus beams in most modern particle accelerators. https://ieeexplore.ieee.org/document/4765896 https://ieeexplore.ieee.org/document/4765896 https://digital.library.unt.edu/ark:/67531/metadc173309/ https://digital.library.unt.edu/ark:/67531/metadc173309/
wizardforhire 2y ago
An oldie but a goodie https://boingboing.net/2005/02/01/brooklyn-residents-j.html https://boingboing.net/2005/02/01/brooklyn-residents-j.html

125 points by fosk 2y ago

Cooling a 200km loop with liquid helium sounds more than moderately difficult! Neat idea but not particularly possible given current material science as always seems to be the case with space elevators.

eppp 2y ago
How cold would the pipe be in space if it was shaded? Wouldnt that cut the energy needed by a bit?
- perihelions 2y ago
  It's more or less impossible to shade a space elevator because the (hot, radiant) earth spans a full hemisphere of its field of view and the sun wanders most of the opposite one. No way to passively reach cryogenic temperatures—let alone the deep-cryogenic ones demanded by high current-density superconductors.
punnerud 2y ago
What about using Starship or similar to move the coolant up, then let it “fall” down? Once you have the elevator operated some of the transportation could be used for refueling coolant. And you start it from space and gradually lower it down to earth.
- ben_w 2y ago
  I don't know why you think that would help? If we could build this at all, we could build it on the ground, then just switch it on (gradually) and it would float, and if we needed to get consumables up, they can be pulled up on a winch like any other payload to space. But also, I don't know why you think Starship is the right category for a solution; the structure in this paper is 200 kilometers in size (it says altitude, but for magnetic repulsion the best separation distance is a constant factor of the size before your get performance issues), whereas a fully stacked Starship is about 0.12 - 0.15. It would be like trying to refuel a 747 in flight with an personal selfie drone.
  - punnerud 2y ago
    The Starship was only for moving coolant, not as part of the elevator. I was thinking you probably have to have extra payload to stop the end. And that it then would be better to start from the top, than from bottom
    - ben_w 2y ago
      I can't visualise what you're trying to suggest. "Stop the end"?
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IncreasePosts 2y ago

(2001). I'm curious what has changed in this space since then.

hinkley 2y ago
I believe the test tether someone took up burned itself to a crisp. The magnetic flux it experienced from the earth was much more intense than their math predicted. That’s the last I heard.
- dredmorbius 2y ago
  Do you have any idea which mission that was? Wikipedia has a listing, if that helps: <https://en.wikipedia.org/wiki/Space_tether_missions https://en.wikipedia.org/wiki/Space_tether_missions>
  - throw310822 2y ago
    TSS-1R mission, 1996 "TSS-1R was deployed (over a period of five hours) to 19.7 km (12.2 mi) when the tether broke. The break was attributed to an electrical discharge through a broken place in the insulation." "Measured currents on the tether far exceeded predictions of previous numerical models by up to a factor of three"
    - dredmorbius 2y ago
      Thanks, I seem to remember that vaguely. I've also had the idea for a while (probably inspired by that mission) that any actual space elevator would be hugely influenced by magnetic and electrical influences, becoming a tremendously long conductor and/or static-charge accumulator. You'd probably want it to be exceptionally well grounded, and want to take precautions embarking or disembarking.
    - hinkley 2y ago
      What I was never clear on is whether that makes them more interesting or less realistic.

PaulHoule 2y ago

How is this different from https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop ?

marcosdumay 2y ago
There's no dynamic exchange of forces between moving objects on this one, just some current flowing through wires.
datadrivenangel 2y ago
The Launch loop uses the momentum of a rotating cable to keep the system up. This space elevator uses super conducting magnets to levitate against the earths magnetic field. It's like a gyroscopic force versus an electromagnet: they're both forces, but one is caused by mechanical movement versus the other which is caused by magnet fields.
ben_w 2y ago
This is supported by long-range magnetic pressure over the entire structure, with some (but not all) of that pressure coming from Earth's own field, and has no moving parts (other than the charge carriers). A launch loop could be short-range magnetic or electric pressure between the cable and the sheath, Earth's field is not important and it would also work on a body with no magnetic field, and it mostly functions by being a very big moving part surrounded by a vacuum chamber.

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JumpCrisscross 2y ago

NbTi has a critical temperature below 10K and generate fields of around 10 T [1]. The paper contemplates a 2T field. Could CeOFeAs permit cooling with hydrogen [2][3]? [1] https://en.m.wikipedia.org/wiki/Niobium%E2%80%93titanium https://en.m.wikipedia.org/wiki/Niobium%E2%80%93titanium [2] https://www.sciencedirect.com/science/article/abs/pii/S0921453413002529 https://www.sciencedirect.com/science/article/abs/pii/S09214... [3] https://en.m.wikipedia.org/wiki/High-temperature_superconductivity https://en.m.wikipedia.org/wiki/High-temperature_superconduc...

vinnyvichy 2y ago
You might be better off with scaling FeSe or waiting for improvements in that class. you can use LN2 (H2 leaks are not just inevitable,large scale deployments of LN2 cooling already exist)

al_borland 2y ago

I seem to remember reading about this in Popular Science around that time. Of all the things I saw in that magazine, the space elevator made of carbon nanotubes was always the one that stuck with me. Though I seem to remember PopSci taking about harnessing an asteroid, or something, and putting it geosynchronous orbit, as a means to create the top anchor point. 25 years later, it seems just as far fetched.

worldsayshi 2y ago
Although we have come much further with carbon nanomaterial. I wonder how close we are to achieving continuous fabric.
- more_corn 2y ago
  We’re about 20 years away. Always will be.
anytime5704 2y ago
This seems like a great way to accidentally cause another global extinction event. I’m probably overestimating the size of the anchor.
- tadfisher 2y ago
  The anchor would need to be beyond geostationary orbit to keep the center of mass geostationary, so a broken tether would result in the anchor departing "outward". The reason to use an anchor is to avoid creating a tether that's twice as long as it needs to be.
  - askvictor 2y ago
    Depends where the tether breaks. If it's somewhere along the middle, then the Earth-side section would fall to Earth. KSR's Mars trilogy examines the impacts (pun intended) of this.
    - 2y ago

stretchwithme 2y ago

How is the elevator car in a space elevator accelerated horizontally? That's what reaching orbit is, right? Horizontal acceleration? The car starts out on the ground at 465m/s. It has to accelerate to 11,068 km/h. What makes it accelerate? The cable, without any force applied to it anywhere? Or is there a rocket on that car? To put mass into orbit, you have to accelerate that mass. And do it without decelerating the elevator. There are no free lunches.

JumpCrisscross 2y ago
> How is the elevator car in a space elevator accelerated horizontally? Momentum transfer from the cable, which is attached to an orbiting counterweight. In this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field. In general one boosts the counterweight directly or, more practically, by sending things down [1]. [1] https://space.stackexchange.com/questions/22447/how-will-the-angular-momentum-of-a-space-elevator-be-preserved https://space.stackexchange.com/questions/22447/how-will-the...
- schiffern 2y ago
  This paper's design has no orbiting counterweight, and only reaches an altitude of 200 km. A launch loop can harvest energy and momentum from the rotor to accelerate payloads, but I don't see any such mechanism here.
  - JumpCrisscross 2y ago
    > This paper's design has no orbiting counterweight Which is why I say I “in this design, some of that momentum would be borrowed from the Earth’s rotation via the cable’s coupling to its magnetic field.” The cable is an electrostatic counterweight because we’re using electromagnetism, not the comparably weak gravitation.
    - schiffern 2y ago
      Problem is "some of the momentum" isn't nearly enough to reach orbit (climbing the tower only gains you 3% of orbital speed, or 0.1% the kinetic energy), and there's no hint of a mechanism that's supposed to accelerate a payload the rest of the way to orbital speed.

lionkor 2y ago

Or, you know, use a rocket...? I dont see an issue with Hydrogen Oxygen rocket propellants at all.

mlyle 2y ago
The annoying things with propellants is that you need to use them to lift more propellants. The rocket equation is not kind. Coming up with some way that lets us waste more mass will push aerospace away from such an exotic set of technologies towards more mainstream use. It is only the fact that space flight is barely possible that makes it so hard.
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codesnik 2y ago

somewhat related concepts: Space fountain and and Launch loop https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Space_fountain https://en.wikipedia.org/wiki/Launch_loop https://en.wikipedia.org/wiki/Launch_loop

spacebacon 2y ago

Several prompts later … The gap between current material science and the required advancements for constructing a magnetically levitated space elevator is significant. Let's break down the key areas where advancements are needed and assess the current state compared to the required state: 1. Superconducting Materials Current State: NbTi Superconductors: NbTi (Niobium-Titanium) superconductors are among the most common, with critical temperatures around 9-10 K. They are widely used in MRI machines and particle accelerators. NbTi can sustain high current densities and generate substantial magnetic fields, but only at very low temperatures maintained by complex and costly cryogenic systems. Required State: Higher Temperature Superconductors: For a space elevator, superconductors that can operate at higher temperatures would reduce the need for extensive cryogenic cooling, thus making the system more practical and less costly. Currently, high-temperature superconductors (HTS) exist (like YBCO - Yttrium Barium Copper Oxide), which can operate above 77 K (the boiling point of liquid nitrogen), but they are not yet produced in long, high-quality, and affordable lengths suitable for large-scale engineering projects. Gap Analysis: The primary challenge is to develop superconductors that can operate at higher temperatures with sufficient current densities and stability. The current material science has not yet achieved a commercially viable production of long-length HTS with consistent quality and performance required for such applications. 2. Carbon Nanotubes and Advanced Fibers Current State: Carbon Nanotubes (CNTs): CNTs are known for their extraordinary tensile strength and low density, making them ideal candidates for space elevator cables. However, the production of long, defect-free CNTs with consistent properties remains a significant challenge. Current production techniques yield short lengths with varying qualities, and scaling up these methods while maintaining material integrity is difficult. Required State: Mass Production of High-Quality CNTs: For a space elevator, extremely long CNTs or similarly strong materials are required to construct a cable that can withstand the enormous stresses involved. These materials must be lightweight yet possess ultra-high tensile strength and stability over long periods. Gap Analysis: The major hurdle is the ability to produce continuous lengths of high-quality CNTs or alternative advanced fibers at a commercial scale. The technology for producing and manipulating these materials at the necessary scale is still in its infancy. 3. Structural Materials and Stability Current State: Composite Materials: Current composite materials, including carbon fiber composites, offer high strength-to-weight ratios. However, they are not yet capable of withstanding the specific stress and environmental conditions required for a space elevator, particularly in terms of radiation resistance and thermal stability. Required State: Advanced Composites and Alloys: Materials need to be developed that can endure the harsh conditions of space, including temperature extremes, radiation, and micrometeorite impacts, while maintaining structural integrity over potentially very long periods. Gap Analysis: Development is needed in creating materials that not only provide the necessary strength and durability but also can be manufactured and maintained at a reasonable cost. Improvements in radiation shielding and thermal management materials are also required. 4. Cooling and Power Systems Current State: Cryogenic Cooling: Current cryogenic systems can maintain superconductors at low temperatures, but they are heavy, complex, and energy-intensive. They are impractical for continuous, large-scale applications like a space elevator. Required State: Efficient Cooling Solutions: More efficient and lightweight cooling systems are required to maintain superconductors at operational temperatures without prohibitive power consumption. Alternatively, development of superconductors that operate at higher temperatures, requiring less intensive cooling, would be beneficial. Gap Analysis: Significant innovation is needed in both cooling technology and power systems to make a space elevator feasible. The challenge is to achieve efficient, reliable, and cost-effective solutions that can be integrated into the elevator structure. Summary The gap between current capabilities and the required advancements is substantial. While we have foundational materials and technologies, such as NbTi superconductors and carbon nanotubes, they are not yet developed to the extent necessary for practical use in a space elevator. Advances in high-temperature superconductors, scalable production of high-quality carbon nanotubes, and the development of lightweight yet strong structural materials are critical. Material science must progress significantly in these areas to move closer to realizing the concept of a magnetically levitated space elevator. This will require substantial research, development, and potentially novel breakthroughs in materials engineering and related technologies. The timeline for achieving these advancements is uncertain, and it could span several decades.

la64710 2y ago

What about the birds and the planes flying into the elevator cables? Is any othe thinking about it? Where do these crazy ideas come from? And what happens when they break and the cables fall to the earth? time we start thinking long term impact on the planet and its life for our ideas.

kimixa 2y ago
There's already plenty of other things of a similar scale in the path of birds and planes currently. Such as other planes. But these being stationary probably makes them even easier to avoid.
tadfisher 2y ago
A Starship produces 76,000 metric tons of CO2-equivalent per launch, which is going to be far more dangerous to the birds in the long term.

mikewarot 2y ago

If we're pushing "out of the box" ideas, why not just use hydrogen balloons to hold up a railgun for the first 20,000 meters of altitude? The ambient pressure at the end would be about 1/10th of that at sea level. You could have outriggers with a very thin high voltage power line to enable station keeping via thrusters (repurposed quadrotor parts?) I wouldn't be surprised it the ambient electrostatic field from the atmosphere were sufficient to power station keeping, or at least some of the instrumentation. If that works, I'm sure they could extend it to twice as long, almost into space.

monkeyfun 2y ago
Relatedly, have you ever heard of skyhook? Not the CIA one but the orbital infrastructure concept -- lets you literally just take a supersonic capable plane with no rocket engines whatsoever into space. Always love that concept with how it's actually engineer-able with current materials and sounds like it shouldn't work until you look closely.
- metadat 2y ago
  This? https://en.wikipedia.org/wiki/Skyhook_(structure) https://en.wikipedia.org/wiki/Skyhook_(structure) Interesting idea, but if I'm understanding correctly, how do you stop the thing you hooked from swinging around and back down? Would you need to reel in 50 miles or whatever of cable?
  - ben_w 2y ago
    You can just let go of it when it's high enough, it picks up (ground) speed on the way up.
pdonis 2y ago
The main cost of getting to low Earth orbit isn't gaining altitude, it's gaining speed. Even if you could levitate a spacecraft to, say, 200 km altitude at zero cost in energy, you would still need about 97% of the energy to get it to orbital speed, that you would have needed to launch it from the Earth's surface.

anonu 2y ago

this was a nice idea 20+ years ago but never materialized - literally. I don't think the materials required - specifically carbon nanotubes - were created that could support the tensions needed for such an idea.

dekhn 2y ago

There's a simple point about space elevators that most people ignore. We would only build a space elevator if it made economic sense. Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. Even more importantly, if we had access to the materials necessary to build space elevators, there are other, much more pressing terrestrial needs that would use up all those materials long before somebody tried to build an elevator. No matter how much fun it is to contemplate their existence, nobody has come up with a justification for the necessary investment required to build and operate one.

darby_nine 2y ago
> Given the reality of construction costs, even if we had the materials, it would like cost many trillions of dollars (at least) so whatever we used it for would have to produce much more value than that. This doesn't seem that difficult given the potential value of mining. I suspect terrestrial politics would dominate this conversation—access to said elevator is far more interesting than any collective concern, and humans as they stand are not capable of resolving collective concerns on any level.
- dekhn 2y ago
  Trillions+ in mining value? What exactly are you proposing mining (platinum seems the most likely, IIRC my D&D)? remember that new sources affect the supply, which changes prices significantly, so it would have to be basically unobtanium to be worth it. And remember, since you developed all that tech just to make the space elevator... most of the mining you did is probably obsolete.
  - ben_w 2y ago
    Even aluminium gets you to a trillion dollars in 6 years. https://en.wikipedia.org/wiki/List_of_countries_by_aluminium_production https://en.wikipedia.org/wiki/List_of_countries_by_aluminium... * Calculation: http://www.wolframalpha.com/input/?i=1%20trillion%20USD%20%2F%20%28aluminium%20price%20%2A%2064%20million%20tons%20per%20year%29 http://www.wolframalpha.com/input/?i=1%20trillion%20USD%20%2... * Old data, China has rapid growth in this sector and is now about 42 megatons/y, but that just changes the result from rounding down to 6 years to rounding up to 6 years: https://www.reuters.com/markets/commodities/china-2023-aluminium-output-hits-record-high-growth-rate-slows-2024-01-17/ https://www.reuters.com/markets/commodities/china-2023-alumi...

Animats 2y ago

Superconducting tapes have become much better since 2001. Can you levitate a superconducting tape against the earth's magnetic field right now? A small scale demo should be possible.

vinnyvichy 2y ago

https://youtu.be/gQjbzuOA2mU https://youtu.be/gQjbzuOA2mU (2024) Why physics favor Mass Drivers over heavy lift rockets guy's voice similar to Bret Victor, (R&Deployment) economics slightly better than space elevator-- you can also use SC magnets but in easier config, repurpose Hyperloop research etc

pfdietz 2y ago

This was an extension of the MCKESR (Magnetically Confined Kinetic Energy Storage Ring) concept Hull was exploring at ANL. The idea here is a ring-shaped flywheel where the centripetal force is supplied by magnetic forces rather than strength of the rotating ring. The advantage is that the stored energy per mass of ring + magnets scales linearly with radius, unlike in a conventional flywheel where (by the virial theorem) the ratio is limited by a constant factor proportional to the strength of the flywheel material divided by its density. The original MCKESR concept had a ring-shaped conductor orbiting in a magnetic field, but a later concept had a chain of ferromagnetic objects being attracted magnetically. The latter was kept passively stable by alternating segments of magnets, one segment where the attraction was stable radially and unstable vertically, the next the opposite. If the ring was moving in the right speed range this would cause dynamic stability in both directions. This Alternating Gradient principle is used (via magnetic forces on moving charged particles) to focus beams in most modern particle accelerators. https://ieeexplore.ieee.org/document/4765896 https://ieeexplore.ieee.org/document/4765896 https://digital.library.unt.edu/ark:/67531/metadc173309/ https://digital.library.unt.edu/ark:/67531/metadc173309/

wizardforhire 2y ago

An oldie but a goodie https://boingboing.net/2005/02/01/brooklyn-residents-j.html https://boingboing.net/2005/02/01/brooklyn-residents-j.html