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Japan starts space elevator experiments

447 points by Futurebot 8y ago

mothsonasloth 8y ago
My favourite Space Elevator concept was from the Halo franchise. There would be multiple elevators on the continents of the planets that were tethered to orbital platforms. They didn't seem to survive the covenant well https://www.youtube.com/watch?v=wfU524OBKhc https://www.youtube.com/watch?v=wfU524OBKhc http://halo.wikia.com/wiki/Space_elevator http://halo.wikia.com/wiki/Space_elevator
sandworm101 8y ago
Carbon nanotubes are cool, but i will believe space elevators possible once someone shows me a carbon nanotube rope i can climb with. I'd settle for a bike or motorcycle chain. A nanotube-based shoelace would be worth a noble prize or two.
- jessaustin 8y ago
  It could be that shoelaces and space elevators turn out to be on the same side of some tipping-point technological breakthrough.
  - TheSpiceIsLife 8y ago
    I’m guessing you mean to say carbon nanotube shoelaces. But it’s amusing to think of it the other way: any society technologically advanced enough to have invented the shoelace will inevitably invent the space elevator.
- Torkel 8y ago
  Given strength and size and other properties that carbon nanotube ropes would need have... Wouldn't a carbon nanotube shoelace be like the worst idea ever? ...strong as a steel cable, but so thin as to be hard to see and handle. And brittle and not so good at bending. => First it slices up your hands when you tighten it and then it breaks when you tie it :)
  - monk_e_boy 8y ago
    Its going to be very interesting when carbon nanotubes are combined with cloth. Ripstop cloth is a mix of plastics and line giving a fexible cloth that is very very strong. Its also airtight so you can inflate it (for a time - its not 100% without a bladder) Inflatables wings. Hulls. https://youtu.be/WgABFvqE8lY https://youtu.be/WgABFvqE8lY
  - eponeponepon 8y ago
    I believe the expectation regarding carbon nanotubes in the sphere of space elevators is that they would be woven and layered into a sheet of human scale; these sheets would be used to construct a curved ribbon for the gondola to climb. You could apply the same principle and weave a bootlace from them, but the limits of current technology would render that an exceedingly expensive bootlace.
    - sandworm101 8y ago
      Given the amount needed for a space elevator, it better be cheap as shoelaces. At 10s of thousands of miles they should have more than enough on hand to disrupt the shoelace market.
- spenczar5 8y ago
  I don’t think rope is a good analogy for nanotubes. I think you want to see it used as a cable, like in suspension bridges or trawling. It should be something that is permanently under tension. A nanotube suspension bridge would be pretty amazing to see.
- onion2k 8y ago
  On a practical note, if you drop something on your foot you need to be able to take your shoe off quickly - cutting the laces is often the best approach. Shoe laces as strong as steel would likely lead to you losing your foot. Same goes for titanium wedding rings...
  - sandworm101 8y ago
    If you can biuld large enough nanotubes that you can weave them into rope, you can engineer in any properties you want. Anything from graphite dust to diamond is an option. Fyi, the military has a specific way to lace boots so the laces can most easily be cut to remove the boot.
- ckemere 8y ago
  We can already make CNT based fibers at scale fairly cheaply. Would happily sell you a shoelace for much less than the $1M that a Nobel prize comes with... http://news.rice.edu/2017/10/16/long-nanotubes-make-strong-fibers/ http://news.rice.edu/2017/10/16/long-nanotubes-make-strong-f... (Though note that this is not one long nanotube, but a macroscale fiber made by extruding micron-scale CNTs in a special way so that they align.)
ourmandave 8y ago
The cars would travel at up to 200kph and arrive at the space station eight days after departure from Earth. These early cable experiments are important, but someone should also be working on the composing an 8 day Elevator Muzak score that won't drive you insane.
- abrowne 8y ago
  I'd pick Max Richter. His Sleep¹, which is nearly 8.5 hours, would be a good start. 1: https://en.wikipedia.org/wiki/Sleep_(album) https://en.wikipedia.org/wiki/Sleep_(album)
- quink 8y ago
  https://en.wikipedia.org/wiki/Law_of_triviality https://en.wikipedia.org/wiki/Law_of_triviality
- sandworm101 8y ago
  Music? The first four days will be safety announcements. The last four will be debates as to who is responsable for cleaning up all the vomit. A week of near-zero-g in a room with 30 people will not be fun.
  - newnewpdro 8y ago
    Is humor against HN rules? I regularly see such posts being downvoted and it doesn't make sense to me.
    - DoreenMichele 8y ago
      Most humor can be categorized as "insubstantive comments" and those are discouraged. It is possible to crack a joke here and get it upvoted, but it's hard to pull it off. I even once had a joke upvoted by quite a lot,* like 50 points or something, but most jokes are downvoted not because humor is forbidden, but because insubstantive comments are discouraged. Some humor is downvoted for being uncivil because a lot of humor is basically poking fun at people or mocking them. A lot of humor is not nice at all. HN tries to meet a very high bar for civility. * Under my old handle and it hit 59 points: https://news.ycombinator.com/item?id=14996229 https://news.ycombinator.com/item?id=14996229
rietta 8y ago
The experiment sounds great. But should this work and a real cable to orbit is built, what happens when the cable snaps!? Can such a structure be made failsafe?
- deleted 8y ago
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- tarzip 8y ago
  That's what safeties are for! We already have a lot of engineering around making elevators safe. TLDR the elevator will clamp on to the rails to slow the free fall. Neat info below on snapping elevator cables and some of the things that would help you. https://science.howstuffworks.com/science-vs-myth/everyday-myths/question730.htm https://science.howstuffworks.com/science-vs-myth/everyday-m...
  - jessaustin 8y ago
    What rails? They're not going to run more than one of these difficult-to-build structures up for each elevator. There will be a single cable, and the car will climb it. What happens if the cable snaps will depend on how far up the car is. Low enough, and it will descend to the surface on a builtin parachute. High enough, and it will perform some portion of an orbit, before descending on its parachute.
    - ghaff 8y ago
      Presumably you could have redundant cables. But two almost adjacent cables would still be exposed to many single points of failure, especially any caused by a deliberate attack on the system. And just a cable falling could be a significant disaster by itself.
    - ben_w 8y ago
      Once you have a space elevator, it’s relatively easy to send up some rockets and demolition explosives that just sit on the cables at appropriate locations and stay there waiting for a disaster; should the cable be broken by malice, accident, or natural causes, the explosives can cut the falling cable into pieces small enough that the rockets can safely guide to the ocean (or orbit, whichever has the lowest delta-v). The travel pods, likewise, can always have rockets on them whose sole purpose is to get the passengers to safely. Yes, it means you’re taking up more mass than you strictly need to, but the great thing about a space elevator is that the mass is no longer a hyper-critical parameter. But yes, no rails here.
yohann305 8y ago
i remember reading here on HN someone explaining why space elevators are not possible. I can't recall why, but he/she had very convincing arguments. Anyone here remember that thread and can link it back here? Thanks
- macspoofing 8y ago
  I'm not sure a space elevator is 'impossible' in the way that faster-than-light communication is. I suspect they argued that the engineering challenges will never be solved - which is a fair argument.
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- pasta 8y ago
  I think the argument was that we don't have materials that are stong enough and light enough and cheap enough at the same time.
  - gnarbarian 8y ago
    IIRC Specifically there are no materials we can currently produce (at that scale) which would be capable of supporting the weight of the cable alone. Let alone cars that ride along it.
    - moby_click 8y ago
      At least we now know the cabin dimensions with a precision of two significant figures.
      - lovemenot 8y ago
        The only other open question is whether it shall be painted in the same colour as the bike-shed.
- 8y ago
pier25 8y ago
I know nothing about physics... but wouldn't the space station need to counter the cable tension?
- ghaff 8y ago
  Most theoretical designs that have been proposed would require a very large counterweight, e.g. a captured asteroid.
  - twic 8y ago
    Or you just build the cable out beyond geosynchronous orbit. The further out your counterweight mass is, the more force it exerts, so, AIUI, the most mass-efficient way to do it is an extension of the cable.
    - jandrese 8y ago
      The problem is how you keep the tether from dragging behind the orbit when you do that. Space elevators require a fairly delicate balancing act to keep the mass directly over the base of the elevator, otherwise they turn into giant slings.
      - theothermkn 8y ago
        The center of mass of the cable-counterweight system orbits at geosynchronous height. Also, the gradient of gravity will Stabilize the attitude in the desired orientation. None of this should be construed as an endorsement of space elevators, though. They will never happen on Earth as it exists now. Over and above the material science, you have to clean out LEO of all satellites before you even start construction. It’s just a really dumb idea all around.
        Bahamut 8y ago
        The satellite issue is why I don't think a space elevator as currently conceived will ever make it.
blahedo 8y ago
> "...six oval-shaped cars, each measuring 18m x 7.2m holding 30 people, ... eight days ...." Whooooa. Let's think about this for a second. Eight days means people need to sleep (and not just sitting up in a chair, no matter how comfy). At 1m x 2m per bed that would be a 15m x 4m space even without aisles to walk between the beds or down the middle or any sort of privacy separators. Also, a bathroom and actual washing facilities of some sort are mandatory, and a kitchen with at least minimal food-prep capabilities (even if it's mostly pre-made); modern airplane galleys only need to deal with trips in the tens of hours. 18m x 17.2m is really really not a lot of space for all that.
- frenchie4111 8y ago
  Shouldn't we just knock the people out for the 8 day trip?
  - Keyframe 8y ago
    And how exactly do you plan to 'knock out' people safely for eight days, or even just a few? Heck, even for just a few hours without medical equipment and personnel?
    - p1mrx 8y ago
      The medical technology for human stasis doesn't seem particularly unattainable, when compared against building a carbon nanotube tether into orbit. Some mammals are able to hibernate for months.
      - Keyframe 8y ago
        So far, for humans, that lives within same realm that warp drives occupy in science fiction.
        p1mrx 8y ago
        If bears were capable of warp drive, then I would agree with you.
ghaff 8y ago
For those looking for a popular culture examination of space elevators--albeit from a number of decades back--check out Arthur C. Clarke's The Fountains of Paradise. It also deals with some of the engineering issues, though again it's quite old.
- djsumdog 8y ago
  Also the Mars Trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson. Honestly that's my favorite Sci-Fi novel series of all time. Just give Red Mars a try and I prosome you won't be able to put it down.
  - mac01021 8y ago
    Gave it to my father after reading it. He thought it was too slow and didn't have enough of a narrative arc, and he opted not to finish reading. I loved the trilogy, though.
    - anentropic 8y ago
      my Dad totally got into it, we read pretty much everything KSR wrote... :)
    - retromario 8y ago
      It is really slow in places. Robinson loves to flesh out the environment of Mars. Beautiful trilogy, really enjoyed it, but it is an occasional slog.
  - jimmcslim 8y ago
    Given a major plot arc in the trilogy was... (SPOILER!!!) ... the destruction of the space elevator by a terrorist organisation and the consequent destruction on the surface of Mars as the cable, released from its counterweight, wrapped itself around the planet... I’m not sure it’s a great example :-)
    - chris_st 8y ago
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mortenjorck 8y ago
It’s cool that any kind of space elevator experiment is happening at all, but temper your expectations with the numbers: this is a 10m cable. It is literally a 1:9,600,000 scale model of a real space elevator.
- TheSpiceIsLife 8y ago
  This isn't a scale model of a real space elevator at all. From the article: Shizuoka University and contractor Obayashi aim to launch two small (10 sq cm) satellites connected by a 10m steel cable from the International Space Station. I don't see any ways in which this is a space elevator related experiment.
  - cptaj 8y ago
    They're testing the cart pulley system in space. Sure, the cable itself is the core technology needed for this, but you still have to work on the rest of it. These nanosats are a good, cheap way to move the TRL forward a bit.
    - tomatotomato37 8y ago
      I actually wonder if that is the true purpose and not what the media glued together out of "thing moving on cable." It could just as well be a test for a space tether or cable centrifuge, with any space elevator research being a secondary thing
coygui 8y ago
Anyone has watched GUNDAM OO?
yohann305 8y ago
Someone patented space elevators in 2015. http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=9085897 http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=90858... No comments...
- zepearl 8y ago
  Thanks for the link. I'm personally very conflicted about patents. In this specific case I classify it as a "speculative" patent => I'm totally against this it. Patents should be allowed only for something that exists / can be demonstrated (which would ensure that patents are something somebody invested in, and therefore at least believed in).
  - worldsayshi 8y ago
    Yeah, I wonder if anyone has patented human teleportation...
    - skissane 8y ago
      Don't patents only have a 20 year lifespan? If you patent human teleportation, and nobody actually develops it in the 20 year life of your patent (a prediction which is highly likely to be true), then you've simply wasted your filing fees, made a charitable donation to the patent office (and your patent attorney).
      - deleted 8y ago
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      - zepearl 8y ago
        Again, "teleportation" would be a "speculative" patent (you have thought about the concept but didn't present anything that works). If you would/could take ownership of only its "concept" then I would reply "screw you - I would take ownership of [humanity]" and you would become nothing. Yo :)
  - lrem 8y ago
zepearl 8y ago
Thinking about a "counterweight" orbiting a planet to which it is connected by a cable: as the cable offers resistance to the planet's atmosphere, and as the planet's atmosphere is active/changing, the "thing orbiting" would still have to have an excellent aerodynamic shape to survive the planet's atmospheric effects, right? (as e.g. the lower part of its cable would probably soon or later be "pushed" by winds therefore initially speeding up the counterweight but lowering its altitude - and/or later after some iterations of push/pull generating maybe a slingshot-effect, sending it into a potentially full crash-course towards the atmosphere/planet's ground).
- comboy 8y ago
  Centrifugal force would keep straightening it up.
  - zepearl 8y ago
    Yes, but probably only in general (meaning only from a theoretical point of view without considering external forces)? E.g. as soon as the cable has headwind (in the opposite way of the planet's rotation) the cable would slack off, the thing in orbit would slow down & lower its altitude (how much? Would it anyway have to always skim the upper atmosphere?) => then as soon as the cable gets tailwind the opposite would happen, with relative slingshot-effect.
    - jaggederest 8y ago
      For practical purposes the atmosphere ends at 500km altitude. The cable is going to have to be 36,000 kilometers long. Atmospheric effects are pretty much rounding error at that point - imagine trying to swing a 10 foot long pole by blowing on the first inch.
      - zepearl 8y ago
        Ok, you're right from that perspective :)
      - 8y ago
cryptozeus 8y ago
If they build this from japan, how would they deal with earthquakes ? Last thing you want is to be flying off to space in 18 x 7 m car
- black6 8y ago
  FTA: > Obayashi envisages a space elevator using six oval-shaped cars, each measuring 18m x 7.2m holding 30 people, connected by a cable from a platform on the sea to a satellite at 36,000 kilometers above Earth. 36000 km is GEO, so it would be near the equator, away from land and safe from quakes.
- bencompanion 8y ago
  Pretty much all approaches I've read about involve building 'top-down' from orbit, often with the earth end meeting an ocean going platform which would allow for a bit of movement in the cable.
Turbots 8y ago
Orbital rings would be a much better and more feasible option with our current technology, although I would love to see a space elevator in my lifetime as well. Check out the fantastic series called upward bound by Isaac Arthur who goes over the many options on leaving our planet: Upward Bound: https://www.youtube.com/playlist?list=PLIIOUpOge0LsGJI_vni4xvfBQTuryTwlU https://www.youtube.com/playlist?list=PLIIOUpOge0LsGJI_vni4x...
breatheoften 8y ago
I saw a bunch of people throwing out good sci-fi space elevator examples and had to drop a reference to the space elevator in Neal Stephenson’s Seveneves. The descriptions are epic and do a good job of giving a real sense of placiness to the result of truly enormous engineering.
- on_and_off 8y ago
  Then let me drop a reference to Sundiver by David Brin, which is the start of the uplift cycle. The elevator is by far the least interesting idea of these novels which center about a future where we have uplifted (given sapience) monkeys and dolphins. We are also trying to survive in an unkind universe where Earth is a third world political power that is making religious fanatics angry.
cstross 8y ago
This isn't the first such experiment (with tethers in space) but previous ones (such as the Shuttle tether experiments from 1996 onwards: https://www-istp.gsfc.nasa.gov/Education/wtether.html https://www-istp.gsfc.nasa.gov/Education/wtether.html ) discovered some unanticipated and terminal problems ... and as they flew aboard a time-limited Shuttle mission there wasn't really any scope for attempting repairs/fixes on orbit. Also, it's arguably obvious with 20/20 hindsight that trying for a 20km long tether on the first experiment was maybe slightly over-ambitious ...
- deleted 8y ago
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scalablenotions 8y ago
This is one day where you REALLY don't want the elevator to jam on the way to the office.
DEADBEEFC0FFEE 8y ago
Google was reported to be looking into this a few years ago. And determined that there was no material strong enough at the time. https://www.extremetech.com/extreme/180682-google-x-admits-its-working-on-a-space-elevator-teleportation-hoverboards https://www.extremetech.com/extreme/180682-google-x-admits-i... That aside, how might adversaries disrupt such an expensive and precarious venture? Seems a very hard to defend machine.
- ObsoleteNerd 8y ago
  99% of the comments about this story online think that they're talking about making one NOW. They don't think they can do it now. They're starting initial research into a few isolated systems required to do it one day in the future when materials science and all the other aspects catch up. It will take decades of R&D, but someone might as well start on the bits we can do now, like a system for climbing the tether (which this is, and it's being done purely in space).
  - DEADBEEFC0FFEE 8y ago
    Fair enough. We have to start somewhere. Perhaps a tether climbing rig will be be useful in future megacity skyscrapers.
    - djsumdog 8y ago
      The base tether point would need to be far away from anything! In the book Red Mars by Kim Stanley Robinson, one is placed in Trinidad and Tobago. The most dangerous part would be slowly dropping the cable; lower it to the point where it could be pulled into a magnetic clamp -- without destroying everything in its path.
stretchwithme 8y ago
I don't understand how a space elevator would be advantageous in terms of the energy required to get something to space. The load still has to reach orbital velocity. Will the station at the end of the tether still need a rocket to deal with the additional mass? Is the fact that this rocket only has to go up once the core advantage? Wouldn't the load going up the elevator pull the tether to one side?
- tartuffe78 8y ago
  The station at the end is in orbit, so it's the difference between trying to climb a ladder to the Moon, and trying to jump to the Moon.
  - usrusr 8y ago
    At the risk of being too pedantic, a rocket is much more like farting yourself to the moon than like jumping. The benefits of ladders remain.
- Filligree 8y ago
  Since rockets lack infinite thrust, they take a finite amount of time to reach space. While they're doing so, they need to fight gravity -- ~all the thrust that's directed downwards, as opposed to horizontally, is wasted energy. There are more reasons to build a space elevator, but that's a big one. It really would be far more energetically efficient.
  - darkmighty 8y ago
    The big problem with rockets is actually that you have to carry your propellant with you, and progressively waste energy accelerating your own propellant. Finite time or limited thrust don't actually affect this (increasing the exhaust velocity does though -- at the cost of energy efficiency). It's the infamous tiranny of the Rocket equation (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) To get near 100% efficiency, it follows from the kinetic energy formula and conservation of momentum the body you're pushing against must have a much larger mass than you[1]. So discounted exotic phenomena, the only way to travel efficiently through space is to push off a very large mass, departing at full velocity, or in the case of near-Earth travel, simply push Earth. The space elevator is essentially an elaborate staircase. It is in a stable equilibrium, and climbing it doesn't steal energy from the counterweight (which in fact doesn't move in fact because it is in constant tension); you're just pushing Earth away. In the grand scheme of things the very low efficiency of maybe 10% (in my guesstimation) to LEO isn't so bad (not even the maybe ~5% interplanetary efficiency); especially considering the costs of space systems in general in comparisson to fuel cost. This small fuel cost makes reusable rockets quite an attractive option near term (as noted by SpaceX). But long term, that's quite a steep inefficiency. If we were to endeavor large scale colonization or exploration of exoplanetary resources it seems to me either a kinetic launch system or at least a space elevator variant would be a necessity. [1] Derivation: M1 v1=M2 v2 => v1^2 = (M2/M1)^2 v2^2; M1 v1^2 + M2 v2^2 = E => M2^2/M1 v2^2 + M2 v2^2 = E; M2 v2^2 (1+M2/M1) = E => K2 = E/(1+M2/M1). As M1->infinity, all the kinetic energy goes to K2 and none to K1 (which is why you don't give Earth any meaningful energy by walking).
zmix 8y ago
> using six oval-shaped cars, each measuring 18m x 7.2m holding 30 people Hmmm...is that 30 people/car or 30 people/6 cars? You will be enclosed with them on 18m x 7.2m, that's 120m², for 8 days! The former case would sound like torture, in the latter case it could be done comfortably, though, but it would still require some good nerves by the travellers...
- aldoushuxley001 8y ago
  30 per car
- dmurray 8y ago
  120 m² is a substantial 3- or 4-bedroom house. People endure a lot worse for much lower payoffs than going to space. In spacecraft, Soyuz is about 6 m³ for three astronauts for two days. Apollo was 6 m³ for three astronauts for two weeks. The Japanese proposal is spacious in comparison.
stcredzero 8y ago
Given enough investment, Stirling engines could beat internal combustion for many applications due to a theoretical efficiency advantage. However, economies of scale and many decades of R&D give internal combustion such a huge advantage, that this probably will never happen. At what point does the 20 year amortized cost of a system involving a space fountain or launch loop acting as the 1st stage of a vastly simplified and downscaled rocket break-even with some small multiple of the 20 year amortized cost of a space elevator? I suspect that this multiple might be small enough that economies of scale and optimizations of other systems could keep space elevators out of the picture forever.
- TeMPOraL 8y ago
  ICEs gave us another boost in civilization, expanded the scale of our economies, which eventually led to enough R&D in electric engines that the latter are slowly but surely replacing ICEs now. Maybe the same thing will happen here? The system you've described could open the Solar System for us, and time + advancements in in-space manufacturing could eventually lead to people building space elevators as an alternative. (Also, Earth is not a good place to get the experience in building space elevators. The Moon is much better, and probably Mars would be a good candidate later on.)
sigmaprimus 8y ago
I'm a bit confused the ISS is only 408km from the earth's surface so why would it take 8 days at 200kph? Unless they are including the speed of orbit in which case the earth is already rotating at 1600 kph. What am I missing here?
- deleted 8y ago
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- sigmaprimus 8y ago
  My bad, missed the explanation below, go synchronization requires a much further distance than the iss. So I guess they will also have to make a new station or shuttle system to get to the iss.
  - bencompanion 8y ago
    Getting from GEO back down to LEO would require pretty serious energy to reduce your altitude. You could possibly get off the elevator early, but you would need to then get up to orbital speed for whatever altitude you're at, which would be non-trivial for LEO. The ISS will almost certainly be decommissioned by 2030 anyway, and we're not going to have a space elevator by then. There'll still be other stuff in LEO that we want to get to though.
- mojomark 8y ago
  They said the tetger would be 36,000 km. 36,000/200kph = 180 hrs... 180hrs/24hrs/day = 7.5 days. Why the tether needs to be 36,000km long wasn't mentioned.
  - chriswarbo 8y ago
    In terms of angular speed (e.g. revolutions per minute), lower orbits are faster, higher orbits are slower (think of a Mercury year versus a Neptune year). The ISS circles the Earth every 92 minutes. If we dropped a cable from the ISS (or another satellite at the same height), the anchoring point (e.g. something like a floating oil platform) would also have to circle the Earth roughly every 92 minutes. That's not feasible. Satellites at 36,000km circle the Earth every 24 hours, which is the same speed that the Earth rotates. If the satellite is orbiting around the equator, going the same direction as the Earth's rotation, then we would not have to move the anchor (the Earth's rotation would do it for us)
yters 8y ago
So many dumb major tech projects. Don't take your ideas from sci fi authors.
- dang 8y ago
  Maybe so, but can you please not post unsubstantive comments to HN?
  - yters 8y ago
    It's substantive, pointing out there are many major tech projects these days based on pipe dreams born of sci fi books. The fact there are so many means either our tech leaders are not very smart, are scamming the government funds, and/or are out of good ideas. Which leads to the bigger question, what has happened to our vision for the future?
    - dang 8y ago
      I believe you that you had those words in mind, but they're not what you posted.
      - yters 8y ago
        Well, I appreciate you civilly correcting me, which you seem to have a good history of doing, so I apologize for my tone.
snowmaker 8y ago
It's unclear to me if this is real or the continuation of a publicity stunt from Obayashi (who has been getting press about their plans to build a space elevator for years). I'm as excited about the theoretical concept of a space elevator as anyone. But the problem remains that no one can produce a cable even close to strong enough. This article has a good description of the material science problem: http://www.spaceward.org/elevator-when http://www.spaceward.org/elevator-when. Basically, we would need to find a material that is at least 10x, probably 25x as strong as any cable today. Carbon Nanotubes are theoretically strong enough, but no one knows how to manufacture them. The longest carbon nanotube tether that has ever been manufactured is only a few inches long, a millimeter in width, and not particularly strong due to imperfections in the manufacturing process. Obayashi is planning a 10m cable. Even building a 10m cable made of carbon nanotubes would require a Nobel Prize worthy breakthrough.
- dmurray 8y ago
  We're only 1 to 1.5 orders of magnitude away from having a material strong enough? Maybe I've been working with computers for too long, but that sounds excitingly achievable.
  - titanomachy 8y ago
    Yeah, just wait 6-7 years and Moore's law should take care of it.
    - Latteland 8y ago
      Okay, that's a joke people. There's no moore's law for carbon nanotube extension (that I know of). There is an analog of electric battery price reduction over time, about 15-30% per year. Here's a graph of it - https://electrek.co/2017/01/30/electric-vehicle-battery-cost-dropped-80-6-years-227kwh-tesla-190kwh/ https://electrek.co/2017/01/30/electric-vehicle-battery-cost....
      - wallace_f 8y ago
ridgeguy 8y ago
I'm curious about space elevator phenomena related to lateral ∆V. At Earth's equator (zero altitude - i.e., on the ground), an object moves spinward at about 0.46 km/sec. In geosynchronous orbit, an object has to move at about 3.07 km/sec. A space elevator car ascending from stationary on the equator to a terminal at geo altitude would require a tangential (lateral) ∆V of 2.61 km/sec. This is in addition to the energy needed for ∆ altitude-related potential energy change. Am I thinking about this right? The faster the ascent, the greater the lateral reaction force on the elevator because ∆V/time increases. Has anybody done that model? I didn't find anything in a brief search. The lateral ∆V also suggests it could get windy on ascent because the atmosphere rotates with the earth on a macroscopic basis. Maybe later tonight, I'll calculate lateral wind velocity as F(altitude) and see if I can fold in pressure drop to get wind pressures as F(altitude). I would love to see even a prototype attempt in my lifetime.
- WtfRuSerious 8y ago
  What about at the poles? Seems like that would negate the lateral problems, but maybe I'm just introducing a twisting one instead...?
  - zamadatix 8y ago
    Then you have an enormously large tower held up by nothing but its own strength instead of being naturally pulled into space. Also takes additional delta-v to get satteliges into common orbits post release.
    - angel_j 8y ago
      This is arguably more doable than cables. I've been told that it's completely possible to build steel structures several miles tall (and the main reason we don't is b/c elevators become a problem).
      - chriswarbo 8y ago
        We can build massive steel towers (e.g. https://en.wikipedia.org/wiki/X-Seed_4000 https://en.wikipedia.org/wiki/X-Seed_4000 would be 4km tall), but they would still be nowhere near space (one common definition of reaching space is https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line which is at 100km). A space elevator would reach at least 36,000km to hit geostationary orbit ( https://en.wikipedia.org/wiki/Geostationary_orbit https://en.wikipedia.org/wiki/Geostationary_orbit ). Most designs are even longer, to provide a counterweight. No known material could support a tower that tall (towers need compressive strength; elevators need tensile strength). It would need to rely on 'active support' or 'dynamic structures', like a space fountain ( http://www.orbitalvector.com/Orbital%20Travel/Space%20Fountains/Space%20Fountains.htm http://www.orbitalvector.com/Orbital%20Travel/Space%20Founta... )
jonthepirate 8y ago
How can the forces exerted by weather patterns still make this viable?
mtgx 8y ago
Isaac Arthur thinks an orbital ring is a better idea: https://www.youtube.com/watch?v=LMbI6sk-62E&index=9&list=PLIIOUpOge0LsGJI_vni4xvfBQTuryTwlU https://www.youtube.com/watch?v=LMbI6sk-62E&index=9&list=PLI... He has other videos on ways we could get into space more cheaply, including by space elevators (which he basically doesn't think are feasible).
avmich 8y ago
Let me quote Pyotr Makovetskii, the book "See the root cause" ("Zri v koren'" in Russian), from chapter 28: (http://n-t.ru/ri/mk/sk028.htm http://n-t.ru/ri/mk/sk028.htm) "And overall, such a tower is a diabolical invention. Rotating in equatorial plane it will knock off everything it encounters. And since any satellite orbit intersect the equatorial plane, sooner or later all satellites with orbit lower than the tower height will be knocked down. At the base of the tower will lay remnants of almost the whole cosmonautics." I'd assume this closes naive discussions about space elevator, at least until the proponents will explain what they are going to do with the problem of hitting satellites. Yet I see this problem again and again with hardly any progress in this area...
pankajdoharey 8y ago
If they could do it would be so cool, and another one of Arthur Clarkes ideas turned to reality after Geo Stationary satellite.
timonoko 8y ago
The Giant Space Wheel (of Seveneves) is so much more attractive than space elevator. That is a large mass on geostationary orbit having smaller pods rotating at the end of ropes. Those pods can be lowered to atmosphere and synchronized with earth rotation. Elevator pod comes down and can stay down maybe couple of hours and then jerked back to heavens. All energy comes from the sun - collected at the center station. Safe because pods can be quickly reeled back to space and stay out of atmosphere until conditions are optimal.
- jimmcslim 8y ago
  Also known as a skyhook.[1] [1] https://en.m.wikipedia.org/wiki/Skyhook_(structure) https://en.m.wikipedia.org/wiki/Skyhook_(structure)
- chris_st 8y ago
  Does it need similar cable strength as the space elevator (as mentioned elsewhere in this discussion), or are its requirements easier to hit?
  - timonoko 8y ago
    The mass of the pod is much less than the end-station of the space elevator. So the cable can be very thin at the far end. If the cable is tapering smoothly it weights 1/4, but it need not to do that, I think it tapers in some kind of exponential curve. So 1/16 might be quite reasonable assumption, but one needs recent college education to calculate that. On the other hand there are strong centrifugal forces, as the pod speeds up from standstill, which is also vividly described in Seveneves book.
    - marcosdumay 8y ago
      There is an exponential relation between the length of the cable and how strong a material you need for it. It comes from the cable needing to support itself, not unlike the rocket equation that comes from the rocket having to propel its own fuel.
- 8y ago
somegraypoupon 8y ago
There was an interesting talk about space elevators at the 33rd chaos communication congress https://youtu.be/EtMJgEggVWQ https://youtu.be/EtMJgEggVWQ
chriswarbo 8y ago
I really like the space fountain concept: it's utterly ridiculous, but completely feasible. It also doesn't need to be as big as a space elevator to be useful (a partial space elevator wouldn't work); space fountains can be as big or small as desired, and applications like radio towers have been mentioned. It would be nice to see even a metre long demo, which I imagine might be possible as something like a student project (4 coil guns exchanging ball bearings).
bariswheel 8y ago
I will file this next to graphene, where these pursuits do everything in our wildest dreams except exit the lab.
m3kw9 8y ago
I like the start the small and ramp up method they are using. This should get plenty of investors mouth watering if they can prove it works and can scale
BenJahman 8y ago
I wouldn't like being stuck in that elevator!
snarfybarfy 8y ago
All this talk about nanotubes, when the real question is: What kind of music are they going to play on the way up???

447 points by Futurebot 8y ago

My favourite Space Elevator concept was from the Halo franchise. There would be multiple elevators on the continents of the planets that were tethered to orbital platforms. They didn't seem to survive the covenant well https://www.youtube.com/watch?v=wfU524OBKhc https://www.youtube.com/watch?v=wfU524OBKhc http://halo.wikia.com/wiki/Space_elevator http://halo.wikia.com/wiki/Space_elevator

sandworm101 8y ago

Carbon nanotubes are cool, but i will believe space elevators possible once someone shows me a carbon nanotube rope i can climb with. I'd settle for a bike or motorcycle chain. A nanotube-based shoelace would be worth a noble prize or two.

jessaustin 8y ago
It could be that shoelaces and space elevators turn out to be on the same side of some tipping-point technological breakthrough.
- TheSpiceIsLife 8y ago
  I’m guessing you mean to say carbon nanotube shoelaces. But it’s amusing to think of it the other way: any society technologically advanced enough to have invented the shoelace will inevitably invent the space elevator.
Torkel 8y ago
Given strength and size and other properties that carbon nanotube ropes would need have... Wouldn't a carbon nanotube shoelace be like the worst idea ever? ...strong as a steel cable, but so thin as to be hard to see and handle. And brittle and not so good at bending. => First it slices up your hands when you tighten it and then it breaks when you tie it :)
- monk_e_boy 8y ago
  Its going to be very interesting when carbon nanotubes are combined with cloth. Ripstop cloth is a mix of plastics and line giving a fexible cloth that is very very strong. Its also airtight so you can inflate it (for a time - its not 100% without a bladder) Inflatables wings. Hulls. https://youtu.be/WgABFvqE8lY https://youtu.be/WgABFvqE8lY
- eponeponepon 8y ago
  I believe the expectation regarding carbon nanotubes in the sphere of space elevators is that they would be woven and layered into a sheet of human scale; these sheets would be used to construct a curved ribbon for the gondola to climb. You could apply the same principle and weave a bootlace from them, but the limits of current technology would render that an exceedingly expensive bootlace.
  - sandworm101 8y ago
    Given the amount needed for a space elevator, it better be cheap as shoelaces. At 10s of thousands of miles they should have more than enough on hand to disrupt the shoelace market.
spenczar5 8y ago
I don’t think rope is a good analogy for nanotubes. I think you want to see it used as a cable, like in suspension bridges or trawling. It should be something that is permanently under tension. A nanotube suspension bridge would be pretty amazing to see.
onion2k 8y ago
On a practical note, if you drop something on your foot you need to be able to take your shoe off quickly - cutting the laces is often the best approach. Shoe laces as strong as steel would likely lead to you losing your foot. Same goes for titanium wedding rings...
- sandworm101 8y ago
  If you can biuld large enough nanotubes that you can weave them into rope, you can engineer in any properties you want. Anything from graphite dust to diamond is an option. Fyi, the military has a specific way to lace boots so the laces can most easily be cut to remove the boot.
ckemere 8y ago
We can already make CNT based fibers at scale fairly cheaply. Would happily sell you a shoelace for much less than the $1M that a Nobel prize comes with... http://news.rice.edu/2017/10/16/long-nanotubes-make-strong-fibers/ http://news.rice.edu/2017/10/16/long-nanotubes-make-strong-f... (Though note that this is not one long nanotube, but a macroscale fiber made by extruding micron-scale CNTs in a special way so that they align.)

ourmandave 8y ago

The cars would travel at up to 200kph and arrive at the space station eight days after departure from Earth. These early cable experiments are important, but someone should also be working on the composing an 8 day Elevator Muzak score that won't drive you insane.

abrowne 8y ago
I'd pick Max Richter. His Sleep¹, which is nearly 8.5 hours, would be a good start. 1: https://en.wikipedia.org/wiki/Sleep_(album) https://en.wikipedia.org/wiki/Sleep_(album)
quink 8y ago
https://en.wikipedia.org/wiki/Law_of_triviality https://en.wikipedia.org/wiki/Law_of_triviality
sandworm101 8y ago
Music? The first four days will be safety announcements. The last four will be debates as to who is responsable for cleaning up all the vomit. A week of near-zero-g in a room with 30 people will not be fun.
- newnewpdro 8y ago
  Is humor against HN rules? I regularly see such posts being downvoted and it doesn't make sense to me.
  - DoreenMichele 8y ago
    Most humor can be categorized as "insubstantive comments" and those are discouraged. It is possible to crack a joke here and get it upvoted, but it's hard to pull it off. I even once had a joke upvoted by quite a lot,* like 50 points or something, but most jokes are downvoted not because humor is forbidden, but because insubstantive comments are discouraged. Some humor is downvoted for being uncivil because a lot of humor is basically poking fun at people or mocking them. A lot of humor is not nice at all. HN tries to meet a very high bar for civility. * Under my old handle and it hit 59 points: https://news.ycombinator.com/item?id=14996229 https://news.ycombinator.com/item?id=14996229

rietta 8y ago

The experiment sounds great. But should this work and a real cable to orbit is built, what happens when the cable snaps!? Can such a structure be made failsafe?

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tarzip 8y ago
That's what safeties are for! We already have a lot of engineering around making elevators safe. TLDR the elevator will clamp on to the rails to slow the free fall. Neat info below on snapping elevator cables and some of the things that would help you. https://science.howstuffworks.com/science-vs-myth/everyday-myths/question730.htm https://science.howstuffworks.com/science-vs-myth/everyday-m...
- jessaustin 8y ago
  What rails? They're not going to run more than one of these difficult-to-build structures up for each elevator. There will be a single cable, and the car will climb it. What happens if the cable snaps will depend on how far up the car is. Low enough, and it will descend to the surface on a builtin parachute. High enough, and it will perform some portion of an orbit, before descending on its parachute.
  - ghaff 8y ago
    Presumably you could have redundant cables. But two almost adjacent cables would still be exposed to many single points of failure, especially any caused by a deliberate attack on the system. And just a cable falling could be a significant disaster by itself.
  - ben_w 8y ago
    Once you have a space elevator, it’s relatively easy to send up some rockets and demolition explosives that just sit on the cables at appropriate locations and stay there waiting for a disaster; should the cable be broken by malice, accident, or natural causes, the explosives can cut the falling cable into pieces small enough that the rockets can safely guide to the ocean (or orbit, whichever has the lowest delta-v). The travel pods, likewise, can always have rockets on them whose sole purpose is to get the passengers to safely. Yes, it means you’re taking up more mass than you strictly need to, but the great thing about a space elevator is that the mass is no longer a hyper-critical parameter. But yes, no rails here.

yohann305 8y ago

i remember reading here on HN someone explaining why space elevators are not possible. I can't recall why, but he/she had very convincing arguments. Anyone here remember that thread and can link it back here? Thanks

macspoofing 8y ago
I'm not sure a space elevator is 'impossible' in the way that faster-than-light communication is. I suspect they argued that the engineering challenges will never be solved - which is a fair argument.
- deleted 8y ago
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pasta 8y ago
I think the argument was that we don't have materials that are stong enough and light enough and cheap enough at the same time.
- gnarbarian 8y ago
  IIRC Specifically there are no materials we can currently produce (at that scale) which would be capable of supporting the weight of the cable alone. Let alone cars that ride along it.
  - moby_click 8y ago
    At least we now know the cabin dimensions with a precision of two significant figures.
    - lovemenot 8y ago
      The only other open question is whether it shall be painted in the same colour as the bike-shed.
8y ago

pier25 8y ago

I know nothing about physics... but wouldn't the space station need to counter the cable tension?

ghaff 8y ago
Most theoretical designs that have been proposed would require a very large counterweight, e.g. a captured asteroid.
- twic 8y ago
  Or you just build the cable out beyond geosynchronous orbit. The further out your counterweight mass is, the more force it exerts, so, AIUI, the most mass-efficient way to do it is an extension of the cable.
  - jandrese 8y ago
    The problem is how you keep the tether from dragging behind the orbit when you do that. Space elevators require a fairly delicate balancing act to keep the mass directly over the base of the elevator, otherwise they turn into giant slings.
    - theothermkn 8y ago
      The center of mass of the cable-counterweight system orbits at geosynchronous height. Also, the gradient of gravity will Stabilize the attitude in the desired orientation. None of this should be construed as an endorsement of space elevators, though. They will never happen on Earth as it exists now. Over and above the material science, you have to clean out LEO of all satellites before you even start construction. It’s just a really dumb idea all around.
      - Bahamut 8y ago
        The satellite issue is why I don't think a space elevator as currently conceived will ever make it.

blahedo 8y ago

> "...six oval-shaped cars, each measuring 18m x 7.2m holding 30 people, ... eight days ...." Whooooa. Let's think about this for a second. Eight days means people need to sleep (and not just sitting up in a chair, no matter how comfy). At 1m x 2m per bed that would be a 15m x 4m space even without aisles to walk between the beds or down the middle or any sort of privacy separators. Also, a bathroom and actual washing facilities of some sort are mandatory, and a kitchen with at least minimal food-prep capabilities (even if it's mostly pre-made); modern airplane galleys only need to deal with trips in the tens of hours. 18m x 17.2m is really really not a lot of space for all that.

frenchie4111 8y ago
Shouldn't we just knock the people out for the 8 day trip?
- Keyframe 8y ago
  And how exactly do you plan to 'knock out' people safely for eight days, or even just a few? Heck, even for just a few hours without medical equipment and personnel?
  - p1mrx 8y ago
    The medical technology for human stasis doesn't seem particularly unattainable, when compared against building a carbon nanotube tether into orbit. Some mammals are able to hibernate for months.
    - Keyframe 8y ago
      So far, for humans, that lives within same realm that warp drives occupy in science fiction.
      - p1mrx 8y ago
        If bears were capable of warp drive, then I would agree with you.

ghaff 8y ago

For those looking for a popular culture examination of space elevators--albeit from a number of decades back--check out Arthur C. Clarke's The Fountains of Paradise. It also deals with some of the engineering issues, though again it's quite old.

djsumdog 8y ago
Also the Mars Trilogy (Red Mars, Green Mars, Blue Mars) by Kim Stanley Robinson. Honestly that's my favorite Sci-Fi novel series of all time. Just give Red Mars a try and I prosome you won't be able to put it down.
- mac01021 8y ago
  Gave it to my father after reading it. He thought it was too slow and didn't have enough of a narrative arc, and he opted not to finish reading. I loved the trilogy, though.
  - anentropic 8y ago
    my Dad totally got into it, we read pretty much everything KSR wrote... :)
  - retromario 8y ago
    It is really slow in places. Robinson loves to flesh out the environment of Mars. Beautiful trilogy, really enjoyed it, but it is an occasional slog.
- jimmcslim 8y ago
  Given a major plot arc in the trilogy was... (SPOILER!!!) ... the destruction of the space elevator by a terrorist organisation and the consequent destruction on the surface of Mars as the cable, released from its counterweight, wrapped itself around the planet... I’m not sure it’s a great example :-)
  - chris_st 8y ago

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mortenjorck 8y ago

It’s cool that any kind of space elevator experiment is happening at all, but temper your expectations with the numbers: this is a 10m cable. It is literally a 1:9,600,000 scale model of a real space elevator.

TheSpiceIsLife 8y ago
This isn't a scale model of a real space elevator at all. From the article: Shizuoka University and contractor Obayashi aim to launch two small (10 sq cm) satellites connected by a 10m steel cable from the International Space Station. I don't see any ways in which this is a space elevator related experiment.
- cptaj 8y ago
  They're testing the cart pulley system in space. Sure, the cable itself is the core technology needed for this, but you still have to work on the rest of it. These nanosats are a good, cheap way to move the TRL forward a bit.
  - tomatotomato37 8y ago
    I actually wonder if that is the true purpose and not what the media glued together out of "thing moving on cable." It could just as well be a test for a space tether or cable centrifuge, with any space elevator research being a secondary thing

coygui 8y ago

Anyone has watched GUNDAM OO?

yohann305 8y ago

Someone patented space elevators in 2015. http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=9085897 http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=90858... No comments...

zepearl 8y ago
Thanks for the link. I'm personally very conflicted about patents. In this specific case I classify it as a "speculative" patent => I'm totally against this it. Patents should be allowed only for something that exists / can be demonstrated (which would ensure that patents are something somebody invested in, and therefore at least believed in).
- worldsayshi 8y ago
  Yeah, I wonder if anyone has patented human teleportation...
  - skissane 8y ago
    Don't patents only have a 20 year lifespan? If you patent human teleportation, and nobody actually develops it in the 20 year life of your patent (a prediction which is highly likely to be true), then you've simply wasted your filing fees, made a charitable donation to the patent office (and your patent attorney).
    - deleted 8y ago
      [deleted]
    - zepearl 8y ago
      Again, "teleportation" would be a "speculative" patent (you have thought about the concept but didn't present anything that works). If you would/could take ownership of only its "concept" then I would reply "screw you - I would take ownership of [humanity]" and you would become nothing. Yo :)
- lrem 8y ago

zepearl 8y ago

Thinking about a "counterweight" orbiting a planet to which it is connected by a cable: as the cable offers resistance to the planet's atmosphere, and as the planet's atmosphere is active/changing, the "thing orbiting" would still have to have an excellent aerodynamic shape to survive the planet's atmospheric effects, right? (as e.g. the lower part of its cable would probably soon or later be "pushed" by winds therefore initially speeding up the counterweight but lowering its altitude - and/or later after some iterations of push/pull generating maybe a slingshot-effect, sending it into a potentially full crash-course towards the atmosphere/planet's ground).

comboy 8y ago
Centrifugal force would keep straightening it up.
- zepearl 8y ago
  Yes, but probably only in general (meaning only from a theoretical point of view without considering external forces)? E.g. as soon as the cable has headwind (in the opposite way of the planet's rotation) the cable would slack off, the thing in orbit would slow down & lower its altitude (how much? Would it anyway have to always skim the upper atmosphere?) => then as soon as the cable gets tailwind the opposite would happen, with relative slingshot-effect.
  - jaggederest 8y ago
    For practical purposes the atmosphere ends at 500km altitude. The cable is going to have to be 36,000 kilometers long. Atmospheric effects are pretty much rounding error at that point - imagine trying to swing a 10 foot long pole by blowing on the first inch.
    - zepearl 8y ago
      Ok, you're right from that perspective :)
    - 8y ago

cryptozeus 8y ago

If they build this from japan, how would they deal with earthquakes ? Last thing you want is to be flying off to space in 18 x 7 m car

black6 8y ago
FTA: > Obayashi envisages a space elevator using six oval-shaped cars, each measuring 18m x 7.2m holding 30 people, connected by a cable from a platform on the sea to a satellite at 36,000 kilometers above Earth. 36000 km is GEO, so it would be near the equator, away from land and safe from quakes.
bencompanion 8y ago
Pretty much all approaches I've read about involve building 'top-down' from orbit, often with the earth end meeting an ocean going platform which would allow for a bit of movement in the cable.

Turbots 8y ago

Orbital rings would be a much better and more feasible option with our current technology, although I would love to see a space elevator in my lifetime as well. Check out the fantastic series called upward bound by Isaac Arthur who goes over the many options on leaving our planet: Upward Bound: https://www.youtube.com/playlist?list=PLIIOUpOge0LsGJI_vni4xvfBQTuryTwlU https://www.youtube.com/playlist?list=PLIIOUpOge0LsGJI_vni4x...

breatheoften 8y ago

I saw a bunch of people throwing out good sci-fi space elevator examples and had to drop a reference to the space elevator in Neal Stephenson’s Seveneves. The descriptions are epic and do a good job of giving a real sense of placiness to the result of truly enormous engineering.

on_and_off 8y ago
Then let me drop a reference to Sundiver by David Brin, which is the start of the uplift cycle. The elevator is by far the least interesting idea of these novels which center about a future where we have uplifted (given sapience) monkeys and dolphins. We are also trying to survive in an unkind universe where Earth is a third world political power that is making religious fanatics angry.

cstross 8y ago

This isn't the first such experiment (with tethers in space) but previous ones (such as the Shuttle tether experiments from 1996 onwards: https://www-istp.gsfc.nasa.gov/Education/wtether.html https://www-istp.gsfc.nasa.gov/Education/wtether.html ) discovered some unanticipated and terminal problems ... and as they flew aboard a time-limited Shuttle mission there wasn't really any scope for attempting repairs/fixes on orbit. Also, it's arguably obvious with 20/20 hindsight that trying for a 20km long tether on the first experiment was maybe slightly over-ambitious ...

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scalablenotions 8y ago

This is one day where you REALLY don't want the elevator to jam on the way to the office.

DEADBEEFC0FFEE 8y ago

Google was reported to be looking into this a few years ago. And determined that there was no material strong enough at the time. https://www.extremetech.com/extreme/180682-google-x-admits-its-working-on-a-space-elevator-teleportation-hoverboards https://www.extremetech.com/extreme/180682-google-x-admits-i... That aside, how might adversaries disrupt such an expensive and precarious venture? Seems a very hard to defend machine.

ObsoleteNerd 8y ago
99% of the comments about this story online think that they're talking about making one NOW. They don't think they can do it now. They're starting initial research into a few isolated systems required to do it one day in the future when materials science and all the other aspects catch up. It will take decades of R&D, but someone might as well start on the bits we can do now, like a system for climbing the tether (which this is, and it's being done purely in space).
- DEADBEEFC0FFEE 8y ago
  Fair enough. We have to start somewhere. Perhaps a tether climbing rig will be be useful in future megacity skyscrapers.
  - djsumdog 8y ago
    The base tether point would need to be far away from anything! In the book Red Mars by Kim Stanley Robinson, one is placed in Trinidad and Tobago. The most dangerous part would be slowly dropping the cable; lower it to the point where it could be pulled into a magnetic clamp -- without destroying everything in its path.

stretchwithme 8y ago

I don't understand how a space elevator would be advantageous in terms of the energy required to get something to space. The load still has to reach orbital velocity. Will the station at the end of the tether still need a rocket to deal with the additional mass? Is the fact that this rocket only has to go up once the core advantage? Wouldn't the load going up the elevator pull the tether to one side?

tartuffe78 8y ago
The station at the end is in orbit, so it's the difference between trying to climb a ladder to the Moon, and trying to jump to the Moon.
- usrusr 8y ago
  At the risk of being too pedantic, a rocket is much more like farting yourself to the moon than like jumping. The benefits of ladders remain.
Filligree 8y ago
Since rockets lack infinite thrust, they take a finite amount of time to reach space. While they're doing so, they need to fight gravity -- ~all the thrust that's directed downwards, as opposed to horizontally, is wasted energy. There are more reasons to build a space elevator, but that's a big one. It really would be far more energetically efficient.
- darkmighty 8y ago
  The big problem with rockets is actually that you have to carry your propellant with you, and progressively waste energy accelerating your own propellant. Finite time or limited thrust don't actually affect this (increasing the exhaust velocity does though -- at the cost of energy efficiency). It's the infamous tiranny of the Rocket equation (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) To get near 100% efficiency, it follows from the kinetic energy formula and conservation of momentum the body you're pushing against must have a much larger mass than you[1]. So discounted exotic phenomena, the only way to travel efficiently through space is to push off a very large mass, departing at full velocity, or in the case of near-Earth travel, simply push Earth. The space elevator is essentially an elaborate staircase. It is in a stable equilibrium, and climbing it doesn't steal energy from the counterweight (which in fact doesn't move in fact because it is in constant tension); you're just pushing Earth away. In the grand scheme of things the very low efficiency of maybe 10% (in my guesstimation) to LEO isn't so bad (not even the maybe ~5% interplanetary efficiency); especially considering the costs of space systems in general in comparisson to fuel cost. This small fuel cost makes reusable rockets quite an attractive option near term (as noted by SpaceX). But long term, that's quite a steep inefficiency. If we were to endeavor large scale colonization or exploration of exoplanetary resources it seems to me either a kinetic launch system or at least a space elevator variant would be a necessity. [1] Derivation: M1 v1=M2 v2 => v1^2 = (M2/M1)^2 v2^2; M1 v1^2 + M2 v2^2 = E => M2^2/M1 v2^2 + M2 v2^2 = E; M2 v2^2 (1+M2/M1) = E => K2 = E/(1+M2/M1). As M1->infinity, all the kinetic energy goes to K2 and none to K1 (which is why you don't give Earth any meaningful energy by walking).

zmix 8y ago

> using six oval-shaped cars, each measuring 18m x 7.2m holding 30 people Hmmm...is that 30 people/car or 30 people/6 cars? You will be enclosed with them on 18m x 7.2m, that's 120m², for 8 days! The former case would sound like torture, in the latter case it could be done comfortably, though, but it would still require some good nerves by the travellers...

aldoushuxley001 8y ago
30 per car
dmurray 8y ago
120 m² is a substantial 3- or 4-bedroom house. People endure a lot worse for much lower payoffs than going to space. In spacecraft, Soyuz is about 6 m³ for three astronauts for two days. Apollo was 6 m³ for three astronauts for two weeks. The Japanese proposal is spacious in comparison.

stcredzero 8y ago

Given enough investment, Stirling engines could beat internal combustion for many applications due to a theoretical efficiency advantage. However, economies of scale and many decades of R&D give internal combustion such a huge advantage, that this probably will never happen. At what point does the 20 year amortized cost of a system involving a space fountain or launch loop acting as the 1st stage of a vastly simplified and downscaled rocket break-even with some small multiple of the 20 year amortized cost of a space elevator? I suspect that this multiple might be small enough that economies of scale and optimizations of other systems could keep space elevators out of the picture forever.

TeMPOraL 8y ago
ICEs gave us another boost in civilization, expanded the scale of our economies, which eventually led to enough R&D in electric engines that the latter are slowly but surely replacing ICEs now. Maybe the same thing will happen here? The system you've described could open the Solar System for us, and time + advancements in in-space manufacturing could eventually lead to people building space elevators as an alternative. (Also, Earth is not a good place to get the experience in building space elevators. The Moon is much better, and probably Mars would be a good candidate later on.)

sigmaprimus 8y ago

I'm a bit confused the ISS is only 408km from the earth's surface so why would it take 8 days at 200kph? Unless they are including the speed of orbit in which case the earth is already rotating at 1600 kph. What am I missing here?

deleted 8y ago
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sigmaprimus 8y ago
My bad, missed the explanation below, go synchronization requires a much further distance than the iss. So I guess they will also have to make a new station or shuttle system to get to the iss.
- bencompanion 8y ago
  Getting from GEO back down to LEO would require pretty serious energy to reduce your altitude. You could possibly get off the elevator early, but you would need to then get up to orbital speed for whatever altitude you're at, which would be non-trivial for LEO. The ISS will almost certainly be decommissioned by 2030 anyway, and we're not going to have a space elevator by then. There'll still be other stuff in LEO that we want to get to though.
mojomark 8y ago
They said the tetger would be 36,000 km. 36,000/200kph = 180 hrs... 180hrs/24hrs/day = 7.5 days. Why the tether needs to be 36,000km long wasn't mentioned.
- chriswarbo 8y ago
  In terms of angular speed (e.g. revolutions per minute), lower orbits are faster, higher orbits are slower (think of a Mercury year versus a Neptune year). The ISS circles the Earth every 92 minutes. If we dropped a cable from the ISS (or another satellite at the same height), the anchoring point (e.g. something like a floating oil platform) would also have to circle the Earth roughly every 92 minutes. That's not feasible. Satellites at 36,000km circle the Earth every 24 hours, which is the same speed that the Earth rotates. If the satellite is orbiting around the equator, going the same direction as the Earth's rotation, then we would not have to move the anchor (the Earth's rotation would do it for us)

yters 8y ago

So many dumb major tech projects. Don't take your ideas from sci fi authors.

dang 8y ago
Maybe so, but can you please not post unsubstantive comments to HN?
- yters 8y ago
  It's substantive, pointing out there are many major tech projects these days based on pipe dreams born of sci fi books. The fact there are so many means either our tech leaders are not very smart, are scamming the government funds, and/or are out of good ideas. Which leads to the bigger question, what has happened to our vision for the future?
  - dang 8y ago
    I believe you that you had those words in mind, but they're not what you posted.
    - yters 8y ago
      Well, I appreciate you civilly correcting me, which you seem to have a good history of doing, so I apologize for my tone.

snowmaker 8y ago

It's unclear to me if this is real or the continuation of a publicity stunt from Obayashi (who has been getting press about their plans to build a space elevator for years). I'm as excited about the theoretical concept of a space elevator as anyone. But the problem remains that no one can produce a cable even close to strong enough. This article has a good description of the material science problem: http://www.spaceward.org/elevator-when http://www.spaceward.org/elevator-when. Basically, we would need to find a material that is at least 10x, probably 25x as strong as any cable today. Carbon Nanotubes are theoretically strong enough, but no one knows how to manufacture them. The longest carbon nanotube tether that has ever been manufactured is only a few inches long, a millimeter in width, and not particularly strong due to imperfections in the manufacturing process. Obayashi is planning a 10m cable. Even building a 10m cable made of carbon nanotubes would require a Nobel Prize worthy breakthrough.

dmurray 8y ago
We're only 1 to 1.5 orders of magnitude away from having a material strong enough? Maybe I've been working with computers for too long, but that sounds excitingly achievable.
- titanomachy 8y ago
  Yeah, just wait 6-7 years and Moore's law should take care of it.
  - Latteland 8y ago
    Okay, that's a joke people. There's no moore's law for carbon nanotube extension (that I know of). There is an analog of electric battery price reduction over time, about 15-30% per year. Here's a graph of it - https://electrek.co/2017/01/30/electric-vehicle-battery-cost-dropped-80-6-years-227kwh-tesla-190kwh/ https://electrek.co/2017/01/30/electric-vehicle-battery-cost....
    - wallace_f 8y ago

ridgeguy 8y ago

I'm curious about space elevator phenomena related to lateral ∆V. At Earth's equator (zero altitude - i.e., on the ground), an object moves spinward at about 0.46 km/sec. In geosynchronous orbit, an object has to move at about 3.07 km/sec. A space elevator car ascending from stationary on the equator to a terminal at geo altitude would require a tangential (lateral) ∆V of 2.61 km/sec. This is in addition to the energy needed for ∆ altitude-related potential energy change. Am I thinking about this right? The faster the ascent, the greater the lateral reaction force on the elevator because ∆V/time increases. Has anybody done that model? I didn't find anything in a brief search. The lateral ∆V also suggests it could get windy on ascent because the atmosphere rotates with the earth on a macroscopic basis. Maybe later tonight, I'll calculate lateral wind velocity as F(altitude) and see if I can fold in pressure drop to get wind pressures as F(altitude). I would love to see even a prototype attempt in my lifetime.

WtfRuSerious 8y ago
What about at the poles? Seems like that would negate the lateral problems, but maybe I'm just introducing a twisting one instead...?
- zamadatix 8y ago
  Then you have an enormously large tower held up by nothing but its own strength instead of being naturally pulled into space. Also takes additional delta-v to get satteliges into common orbits post release.
  - angel_j 8y ago
    This is arguably more doable than cables. I've been told that it's completely possible to build steel structures several miles tall (and the main reason we don't is b/c elevators become a problem).
    - chriswarbo 8y ago
      We can build massive steel towers (e.g. https://en.wikipedia.org/wiki/X-Seed_4000 https://en.wikipedia.org/wiki/X-Seed_4000 would be 4km tall), but they would still be nowhere near space (one common definition of reaching space is https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line https://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line which is at 100km). A space elevator would reach at least 36,000km to hit geostationary orbit ( https://en.wikipedia.org/wiki/Geostationary_orbit https://en.wikipedia.org/wiki/Geostationary_orbit ). Most designs are even longer, to provide a counterweight. No known material could support a tower that tall (towers need compressive strength; elevators need tensile strength). It would need to rely on 'active support' or 'dynamic structures', like a space fountain ( http://www.orbitalvector.com/Orbital%20Travel/Space%20Fountains/Space%20Fountains.htm http://www.orbitalvector.com/Orbital%20Travel/Space%20Founta... )

jonthepirate 8y ago

How can the forces exerted by weather patterns still make this viable?

mtgx 8y ago

Isaac Arthur thinks an orbital ring is a better idea: https://www.youtube.com/watch?v=LMbI6sk-62E&index=9&list=PLIIOUpOge0LsGJI_vni4xvfBQTuryTwlU https://www.youtube.com/watch?v=LMbI6sk-62E&index=9&list=PLI... He has other videos on ways we could get into space more cheaply, including by space elevators (which he basically doesn't think are feasible).

avmich 8y ago

Let me quote Pyotr Makovetskii, the book "See the root cause" ("Zri v koren'" in Russian), from chapter 28: (http://n-t.ru/ri/mk/sk028.htm http://n-t.ru/ri/mk/sk028.htm) "And overall, such a tower is a diabolical invention. Rotating in equatorial plane it will knock off everything it encounters. And since any satellite orbit intersect the equatorial plane, sooner or later all satellites with orbit lower than the tower height will be knocked down. At the base of the tower will lay remnants of almost the whole cosmonautics." I'd assume this closes naive discussions about space elevator, at least until the proponents will explain what they are going to do with the problem of hitting satellites. Yet I see this problem again and again with hardly any progress in this area...

pankajdoharey 8y ago

If they could do it would be so cool, and another one of Arthur Clarkes ideas turned to reality after Geo Stationary satellite.

timonoko 8y ago

The Giant Space Wheel (of Seveneves) is so much more attractive than space elevator. That is a large mass on geostationary orbit having smaller pods rotating at the end of ropes. Those pods can be lowered to atmosphere and synchronized with earth rotation. Elevator pod comes down and can stay down maybe couple of hours and then jerked back to heavens. All energy comes from the sun - collected at the center station. Safe because pods can be quickly reeled back to space and stay out of atmosphere until conditions are optimal.

jimmcslim 8y ago
Also known as a skyhook.[1] [1] https://en.m.wikipedia.org/wiki/Skyhook_(structure) https://en.m.wikipedia.org/wiki/Skyhook_(structure)
chris_st 8y ago
Does it need similar cable strength as the space elevator (as mentioned elsewhere in this discussion), or are its requirements easier to hit?
- timonoko 8y ago
  The mass of the pod is much less than the end-station of the space elevator. So the cable can be very thin at the far end. If the cable is tapering smoothly it weights 1/4, but it need not to do that, I think it tapers in some kind of exponential curve. So 1/16 might be quite reasonable assumption, but one needs recent college education to calculate that. On the other hand there are strong centrifugal forces, as the pod speeds up from standstill, which is also vividly described in Seveneves book.
  - marcosdumay 8y ago
    There is an exponential relation between the length of the cable and how strong a material you need for it. It comes from the cable needing to support itself, not unlike the rocket equation that comes from the rocket having to propel its own fuel.
8y ago

somegraypoupon 8y ago

There was an interesting talk about space elevators at the 33rd chaos communication congress https://youtu.be/EtMJgEggVWQ https://youtu.be/EtMJgEggVWQ

chriswarbo 8y ago

I really like the space fountain concept: it's utterly ridiculous, but completely feasible. It also doesn't need to be as big as a space elevator to be useful (a partial space elevator wouldn't work); space fountains can be as big or small as desired, and applications like radio towers have been mentioned. It would be nice to see even a metre long demo, which I imagine might be possible as something like a student project (4 coil guns exchanging ball bearings).

bariswheel 8y ago

I will file this next to graphene, where these pursuits do everything in our wildest dreams except exit the lab.

m3kw9 8y ago

I like the start the small and ramp up method they are using. This should get plenty of investors mouth watering if they can prove it works and can scale

BenJahman 8y ago

I wouldn't like being stuck in that elevator!

snarfybarfy 8y ago

All this talk about nanotubes, when the real question is: What kind of music are they going to play on the way up???