Magnetically levitated space elevator to low-earth orbit (2001) [pdf] | Hacker News Reader

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

publications.anl.gov

125 pointsfosk104 comments

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.

Although we have come much further with carbon nanomaterial. I wonder how close we are to achieving continuous fabric.

We’re about 20 years away. Always will be.

This seems like a great way to accidentally cause another global extinction event.

I’m probably overestimating the size of the anchor.

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.

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.

Even an optimal space elevator needs to support a sizable portion of its own tether weight with the tether itself.

For a solid non-magnetic tether to be at all realistic, the tether material would likely be so light relative to it's length/volume, it'll never be at all dangerous regardless of how high you drop it from - its terminal velocity would be tiny.

I can drop some yarn, fishing line, whatever, from whichever height I want and it will never be dangerous to anything on the ground. Same principle.

I dont know about magnets, but I suppose the same applies here: If your tether isn't light, its own weight will add a stupid amount of stresses that would likely deform any load-bearing metal. Probably the magnets themselves in this case.

But I thought the whole point of an elevator is you elevate things. Which means the line falling wouldn't be the biggest problem- that would be the payload falling to earth surely?

The falling line would be a problem still - using fishing line as an example ignores scaling. The seed cable for example in some designs is 20 tons by itself: https://en.wikipedia.org/wiki/Space_elevator_construction

So possible 100s to thousands of tons falling for 5+ days…

Spread out over some drop area that's still just a nuisance. Even falling on one area chances of loss of life are minimal, since due to the gradient of gravity accelerating the top end of the wire the least. It should experience way too much drag to have some sort of whip effect on the ground rather than entering a stable configuration before arrival. You'll see it more-or-less neatly arriving in the right order. The first few grams of material landing on your house is maybe a good warning to get out of the way before the remaining 20 tons are done arriving in a few days.

If you have some thin wire design you could also consider just spooling it up as it drops, either at the base or with portable infrastructure you'll have plenty of time to deploy. If you do that you're just dealing with grams of material/second that you can deal with piecewise. Do this faster than terminal velocity and it'll land exactly where you want it to.

That part is not exactly an engineering challenge if you consider what other other stuff humanity likes to get up to with kilometers of much heavier cables and chains.

There shouldn't be much of an issue with designing the the payload as an entry vehicle. Give it the ability to destructively remove itself from the tether, then parachute down. Or just build your tether next to a body of water and have the payload steer into that.

That is if your payload wasn't so high up, it's now on its way to an orbit around earth. I think physically the place of departure should be the periapsis of its orbit, so even with orbital decay through atmospheric drag you'll have long enough to figure where to steer it.

But if you break the tether halfway down the bottom half falls at 16,000 mph right? And then it’s burning and then it cracks like a whip. I don’t know about extinction, but not a fun time for anyone.

might be a good idea to have it (explosively?) disconnect it's segments if it's found to be broken. You'll spread the impact but avoid something like a whip crack.

Aren’t they talking about a mess up on the asteroid trajectory? There is no way a space elevator cable snapping wipes out all life on earth, although I’m sure any populated areas it hits would be quite devastated.

A falling elevator would not wipe anyone out. They would place a protective balloon containing approximately 5 quadrillion tons of gas beneath it. The elevator would be paper thin and a couple of meters wide in the middle where it needs to be strongest. The parts that don’t burn will flutter and slowly fall to the ground.

Not 16,000 mph. A very lightweight tether (thing tie down straps) will drift down and land softly.

If you use an asteroid as an anchor, then you are doing it wrong. You made your space elevator half as long as it could be!

A longer elevator can fling you into the outer solar system. Just climb to the correct height, wait until the right phase angle, and let go.

Light Foundation TV series spoilers below -

In the first episode, a space elevator is bombed. It’s pretty catastrophic! I think a lot of people underestimate the forces involved in something of this scale collapsing.

“ The tether wrapped around the planet like a garrote.

It cut 50 levels down.”

This is obviously fiction, but so is this research and the general concept of space elevators.

What would the mass of said asteroid have to be to accommodate such a design?

Maybe you could have a HALO of THORNS (Telemetry homogeneous orbital restrainer nano-lattice stabilizer) - that have 13 satellite thrusters that can maintain the alignment of the nano-pillars... and have them sectionaly distributed as rings on the Z -- with tethered lattice of tubes tying it all together like a Chinese finger trap.

https://www.youtube.com/watch?v=RnofCyaWhI0 <-- These things... https://i.imgur.com/O9eWZnH.jpeg

and the carbon lattice is also a fuel-capillary system - that feed like a live thing...

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

[2] https://www.sciencedirect.com/science/article/abs/pii/S09214...

[3] https://en.m.wikipedia.org/wiki/High-temperature_superconduc...

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)

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.

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.

This?

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?

You can just let go of it when it's high enough, it picks up (ground) speed on the way up.

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.

thats what the railgun is for. Altitude is to reduce friction and energy needed.

> thats what the railgun is for

A railgun that can provide a delta-v of 8 kilometers per second?

You sent me down a fun rabbit hole for rail-guns, nano-tubes, super conductors, velocity requirements, megajoules required to launch 1,000KG payload into space:

Imagine a U/C channel of carbon nano tube and corresponding super conducting magnets that act as the rail-gun in the same way an aircraft carrier does...

(The maths in this thread are pretty cool):

You may enjoy this fun short read:

https://chatgpt.com/share/616a4cfb-d091-4d09-97a9-e3e7d3e850...

When it's free-floating above the atmosphere and can be as long as you want... sure, why not?

Yes, that would be the proposal.

Existing ship mounted railguns already shoot projectiles around 3km/s. It is generally thought that they could be scaled up to 8 km/s and larger size. The main problem is that if you fire human sized objects that fast at sea level you end up with a plasma ball due to air friction. This isn't an issue with chemical rockets because they start at 0 and accelerate to Vmax, whereas the railgun projectiles start at Vmax and decelerate.

Higher altitude would remove much of the friction problem.

Existing light gas guns can already hit 8 km/s: https://en.wikipedia.org/wiki/Light-gas_gun

The biggest advantage of very high altitude reducing the friction problem isn't just that it stops your projectile from turning into plasma, it is that the size of the minimum viable projectile is reduced. People keep focusing on getting people or vehicles into orbit, but the main advantage of a gun-to-orbit system is that the packet size can be made very small. Think machine gun instead of cannon. This means a smaller gun and thus smaller capital investment.

Instead of the balloon-supported long gun that mikewarot suggested, imagine a balloon at 30 km altitude supporting a 5 meter long gun and a few tons of both propellant and <1 gram pellets. A target satellite is shot in a long continuous burst, leaving the satellite with a lot more mass and a slightly disturbed orbit. Later shots from a different location and direction can be used to compensate for the added impulse to the satellite's orbit.

This could be a cheap way to get a bunch of metal into orbit, or possibly even fuel and oxidizer.

You want to fire thousands of bullet size pieces of metal into low earth orbit? Holy Kessler Cascade, Batman!

While that's not my intention, if you actually wanted to damage satellites and cause a Kessler Syndrome scenario, it's hard to find a system that would have a bigger bang-for-your-buck.

I was rather envisioning a target satellite that is designed to absorb the pellet as an inelastic collision. It would probably resemble something like this: https://en.wikipedia.org/wiki/Black_body#/media/File:Black_b... . Of course, if it didn't work as designed, then it could be a problem.

The point was that a high altitude low-mass-per-shot gun system could get mass into orbit with a similar energy cost as a space elevator with significantly less upfront capital cost and no need for miracle materials.

> Existing ship mounted railguns already shoot projectiles around 3km/s.

Projectiles of what mass? And with what acceleration? As I understand it, with feasible railgun lengths the acceleration is well above the limit of human tolerance, and the projectile mass is significantly smaller than a typical payload put into LEO by conventional rockets.

Yeah, why not? Even if the railgun described was perfectly vertical, it would have 20km of length (vs presumably ~10m max for a military railgun that hits mach 3+). If I'm doing the math right, at 20km of length you need an acceleration of about 160 Gs to reach 8 km/s over that length. Survivable for some payloads.

If the railgun is sloped at a 1% grade, it has ~2,000km of length. On that track, a comfy 1.6 Gs of acceleration for 500 seconds gets you up to 8 km/s.

Doesn't the fact that you don't need to deal with as much air at higher altitude make it much easier to increase the extra amount of delta v needed?

I think there might with the balloons blocking the entire sky.

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://digital.library.unt.edu/ark:/67531/metadc173309/

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

There's no dynamic exchange of forces between moving objects on this one, just some current flowing through wires.

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.

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.

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.

How cold would the pipe be in space if it was shaded? Wouldnt that cut the energy needed by a bit?

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.

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.

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.

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

I can't visualise what you're trying to suggest. "Stop the end"?

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.

> 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...

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.

> 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.

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.

> 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)

Where is your math?

The top of the elevator is travelling at orbital velocity. This is trivial to show in designs with a counterweight. (Here, the magnetic coupling makes it less intuitive.) If you are on an orbiting object, i.e. the top of a space elevator, you’ve achieved orbital velocity.

Sorry, just returned to correct my error -- I drastically overestimated the velocity gain. In truth you only gain about 2.3 m/s (i.e. 0.03% orbital velocity) when climbing to the top of the elevator. Math is simply final velocity minus initial velocity: https://futureboy.us/fsp/frink.fsp?fromVal=%28earthradius+%2...

>The top of the elevator is travelling at orbital velocity. This is trivial to show in designs with a counterweight.

Per the paper this design only reaches 200 km in altitude, therefore it has no counterweight (a counterweight would need to be somewhere above 35,786 km altitude). Speed at the top is far below orbital velocity, so it requires a method of acceleration.

The paper acknowledges this. From the abstract:

"At the top of the loop, vehicles may be accelerated to orbital velocity or higher by rocket motors, electromagnetic propulsion, or hybrid methods."

Probably need that factor of tau. Don't math tired, folks! :)

https://futureboy.us/fsp/frink.fsp?fromVal=2+pi+%28+%28earth...

The top of a space elevator, by definition, is not an orbiting object.

Depending on the height of the space elevator, the speed of its top will be smaller, equal or greater than the speed required at that height for a stable circular orbit.

The top of a space elevator will have the same angular velocity as the Earth. The angular velocity of an orbiting object is equal to that of the Earth only when it is on a geosynchronous orbit (i.e. an extremely high orbit in comparison with those of most satellites or in comparison with the height of the space elevator from this proposal).

In order to launch a satellite from a space elevator without additional acceleration, it is not necessary for its height to be that of a geosynchronous orbit.

For smaller heights, any object released from the top will fall towards the Earth on an elliptical orbit. If the height is big enough, the elliptical orbit will not intersect the solid Earth or the atmosphere of the Earth. Nevertheless, the minimum height for this is still on the order of a few tens of thousands of km, i.e. at least 100 times the height of the space elevator from this proposal.

One thing with a space elevator that makes it so much more efficient than rockets is precisely because you don't necessarily need the payload itself to supply this horizontal acceleration. The space elevator is attached to the ground at one end, and the other is way up in orbit. There must be forces in play _already_ for the entire thing to stay standing, before you get to any concept of a payload/car. Part of the idea of building the elevator in the first place is to solve for these orbital forces in a generalized way independent of the payloads themselves. It's like strapping various sized rockets to your various specific payloads, versus building a generalized model of a rocket ship, and then just putting the various payloads inside the generalized rocket ship. Space elevator is a further evolution of the concept. You don't even need to use the rocket ship abstraction anymore. You're generalizing/abstracting the orbital transition itself into the structure of the elevator, and then just send things up and down it. The payload now only needs to worry about moving along the elevator, the elevator itself has already "solved" for the orbital horizontal acceleration by nature of its structure existing in the first place.

In terms specifically of mass/energy conservation, as the other reply said, energy is borrowed from either the earth's rotation and/or kinetic energy from a counterweight at the end of the elevator up in orbit.

>you don't necessarily need the payload itself to supply this horizontal acceleration. The space elevator is attached to the ground at one end, and the other is way up in orbit.

On a conventional space elevator this is true. You just go up to 35,786 km altitude (AKA geostationary orbit) and let go.

However the structure described in this paper only goes up to 200 km altitude, so it still needs a horizontal acceleration system.

If we are talking space elevators, we should consider using 'there ain't no such thing as a free lunch' with regards to Larry Niven

An oldie but a goodie

https://boingboing.net/2005/02/01/brooklyn-residents-j.html

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

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.

Do you have any idea which mission that was?

Wikipedia has a listing, if that helps: <https://en.wikipedia.org/wiki/Space_tether_missions>

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"

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.

What I was never clear on is whether that makes them more interesting or less realistic.

The one thing that's clear is that this makes tethers a more challenging engineering problem than a naive / uninformed view might have suggested.

This is almost always the situation in engineering applications. The simple approach based on first principles turns out to be massively influenced by second- and higher-order effects. See Admiral Hyman Rickover's "Paper Reactors" for a classic take on this:

<https://whatisnuclear.com/rickover.html>

Reminds me of a futurist I read years ago who was sure super critical water oxidation would solve all of our pollution problems. Ceramics are a “Pick two” material. You can handle heat, pressure or corrosion. SCWO requires all three. Some clever team invented composite ceramics trying to fix the problem, but that was a decade or two ago and still it’s a niche solution used for truly pernicious toxins and that’s about it, so I’m guessing it either didn’t work long term or was made out of unobtanium.

What's the role of ceramics in SCWO?

My only familiarity with that is a quick skim of the Wikipedia article, though that makes no mention of ceramics.

somewhat related concepts: Space fountain and and Launch loop

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

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

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.

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.

> 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.

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.

Even aluminium gets you to a trillion dollars in 6 years.

https://en.wikipedia.org/wiki/List_of_countries_by_aluminium... *

Calculation: 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-alumi...

Aluminum is widely available in the earth and if you approached earth with a new delivery at scale, prices would fall through the floor.

So would the cost of building space elevators. I'm betting there wouldn't be a single part of society unaffected by an explosion of raw materials at much lower cost. It's just an insanely high investment cost to kick off the industrialization of space.

Besides, mining on earth has many externalities that aren't reflected in the commodity price. Some of the most brutal and inhumane conditions on earth right now are tied directly to market demand for rare or difficult to aggregate minerals. The sooner we can shut that down the sooner we can claim social progress without ten asterisks trailing it.

That aluminium is widely available on earth was necessary to my point that it is trivial to find existing examples in the trillion-dollar scale.

Aluminium prices would only fall if you were selling the whole thing in one go for instant delivery — unusually for most supplies this form of delivery would be technically possible, but RFGs are normally considered "weapons" rather than "shipping". Look at how much supply has increased this century vs. price: production has seen near-continuous growth while the price has been spiky rather than a consistent downward trend, this is because aluminium is *really useful*.

Given that orbital dynamics makes it more like a months-to-years process just to get to the asteroid in the first place, who knows how long to capture it and stabilise for mining etc., and that mining itself would not be an instant process even if we happen to get a convenient pile of purely metallic (non-oxidised) rubble, it won't be all on the market for instant delivery.

I get similar values for copper: https://www.wolframalpha.com/input?i=1+trillion+USD+%2F+%28%...

Zinc is ~ 30 years of global production at current prices, which would be pushing it for a corporate investment but not totally implausible: https://www.wolframalpha.com/input?i=1+trillion+USD+%2F+%28%...

Just under 4 years for iron ore: https://www.wolframalpha.com/input?i=1+trillion+USD+%2F+%28%...

Just over 4 years for gold: https://www.wolframalpha.com/input?i=1+trillion+USD+%2F+%28%...

I think aiming for a trillion USD of platinum would indeed crash the market, as the same formula gives me 180 years for that: https://www.wolframalpha.com/input?i=1+trillion+USD+%2F+%28%...

I am willing to bet that Elon Musk and SpaceX are doing the calculations very carefully and will build a space elevator if technology advances make it more cost effective than reusable rockets to get to Mars.

Many technologies are developed long before they are viable because they have military value. Access to space is currently a major national security issue, so a space elevator could be a manhattan project.

Some technologies are developed by the free market before they are economically viable too. LEO constellations for instance (both the original - iridium, and starlink).

>developed by the free market

>iridium

For some reason I was skeptical of this (suspiciously tidy) myth-making, and the more I look into it the more I'm convinced I was right to be skeptical.

Turns out the relevant engineers -- Ken Peterson and Ray Leopold -- both worked on military and government communications systems immediately prior to being hired at Motorola and starting the Iridium project. Peterson's bio is rather vague on timelines[0], but available information on Leopold indicates he joined Motorola in 1987[1] (directly from the Air Force Electronic Systems Division,[2] which develops communication systems), which is the same year he and Peterson started work on Iridium.[3]

This has all the hallmarks of one of those nice neat (and of course plausibly deniable) tech transfers from military/taxpayer dollars, complete with the cute official origin story featuring a C-suite executive's wife.

[0] https://www.tributearchive.com/obituaries/25954530/ken-peter...

[1] https://ocw.mit.edu/courses/16-886-air-transportation-system...

[2] https://en.wikipedia.org/wiki/Electronic_Systems_Center

[3] https://www.laits.utexas.edu/~anorman/long.extra/Student.F98...

Pretty much everything that has to do with space was first developed by governments for military purposes. Rockets, satellites, communications, imaging, etc.

I think your point supports the general thesis that many technologies are developed before they are economically viable.

Definitely agree! Just observing that when the credit line is "some technologies are developed by the free market," people seem inclined to forget that part. Cheers

> Pretty much everything that has to do with space was first developed by governments for military purposes. Rockets, satellites, communications, imaging, etc.

No. First works on rockets was conduct by free market, even British Interplanetary Society designed flight to Moon (1938) and Lunar Space Suit (1940), unfortunately these works stay plans. BIS said, this is because too strict British regulations. https://www.bis-space.com/technical-projects/

It is just coincidence, in Germany made first space scale rocket (A-4) and Soviets made first satellite.

Planned first satellite was Vanguard, born in civilian American Rocket Society and used civilian sounding rockets rather than military missiles. https://en.wikipedia.org/wiki/Project_Vanguard https://en.wikipedia.org/wiki/American_Rocket_Society

Just after Soviets demonstrate first satellite launch and huge for that time ICBM R-7, US government joined space race and participated in it until Russians shown interest fall

After Russians avoid to show something similar to Apollo program, US government cancelled next launches and switched to minimalist space program, just to support lead in space, because of military considerations.

BTW Elon Musk space program was not first commercial program. Before him exists at least one program with sounding rockets and one with mega-cannon.

Unfortunately, Western governments for understandable reasons fear to accept 3rd world countries to develop such programs, because of non-proliferation of mass destruction weapons. So, when programs eventually moved to 3rd world countries (due to lack of interest in developed countries), Western governments used brute force to cancel them.

https://en.wikipedia.org/wiki/OTRAG https://en.wikipedia.org/wiki/Gerald_Bull

Iridium considered to be viable, it's just late for few years, when already appear affordable global GSM roaming, when Iridium literally made to be very similar to satellite GSM.

Starlink is totally different beast, as it is magnitudes faster than GSM and literally belongs to broadband Internet, when have virtually global coverage (yes, exists 4G and even 5G, but they don't have global coverage now).

These are somewhere similar to cryptocurrencies, which lose 1st world (and most important market), because created by scientists of 1st world, to solve problems which are not important for first world, and 2nd/3rd worlds are not capable to maintain sustainable development/support of crypto-technologies.

So from first look could appear as cryptocurrencies are not economically viable at all, but I think, their real problem, that 2nd/3rd worlds are too fragmented to gather resources need to develop solution of their problems, not just be involved in works of 1st world developers.

How's laser launch research come since the 1970s? It's probably limited to launching metal hardware, but when the cost of a space elevator is compared to making a bunch really big lasers and putting them radially around some mirrors, it's something to think about. Is it an overheating problem? The mirrors and optics would just get fried?

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.

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.

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.

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.

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.

> major hurdle is the ability to produce continuous lengths of high-quality CNTs

What is an intermediate market for medium-length high-quality CNTs?

Presumably anything that wants a "medium"* length very strong cable; civil infrastructure comes to mind, might be useful for suspension bridges?

* quotes because all things are relative, by "medium" in the context of a space elevator you may have meant "continent sized"?

Current maximum continuous length is about a foot.

At present. From context, I infer the question is "we know what we can use 1cm long carbon nanotubes for, and what we can use 36,000 km long carbon nanotubes for, but what economic value is there for stuff between such that we may try to monetise the R&D pathway to the latter?"

Quality focused monetized solutions that reward increasing the continuous length but work at shorter lengths as well. Everyday materials come to mind.

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

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.

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

Reply on news.ycombinator.com