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Skyscraper in the Clouds

Analemma seems the perfect name for the proposed ‘floating’ space tower being discussed by the Clouds Architecture Office, an imaginative New York firm whose unusual designs include a Martian habitat made of ice and a concept study of flight into deep space using comets for resources. An analemma is a diagram that traces the movement of the Sun in the sky as seen from a particular location on Earth. Over time, the position changes because of orbital eccentricity and our planet’s axial tilt, so that a slim figure-eight is the result.

That’s relevant to the Analemma tower because it is conceived as a huge construction tethered to an asteroid that would be moved into what the firm describes as ‘an eccentric geosynchronous orbit’ over Earth. The orbit allows the structure to move between the northern and southern hemispheres, tracing out a figure-eight over the surface. With the slowest speed over the ground at the top and bottom of the figure-eight, Clouds Architecture Office suggests that occupants could move back and forth, interacting with ground resources at these points. New York City is suggested as the location for one of the slow parts of the preferred orbit.


Image: Analemma inverts the traditional diagram of an earth-based foundation, instead depending on a space-based supporting foundation from which the tower is suspended. This system is referred to as the Universal Orbital Support System (UOSS). By placing a large asteroid into orbit over earth, a high strength cable can be lowered towards the surface of earth from which a super tall tower can be suspended. Since this new tower typology is suspended in the air, it can be constructed anywhere in the world and transported to its final location. The proposal calls for Analemma to be constructed over Dubai, which has proven to be a specialist in tall building construction at one fifth the cost of New York City construction. Credit (text and image): Clouds Architecture Office.

A skyscraper without a foundation on Earth? The concept makes for a great science fiction backdrop, if nothing else, and calls up images of a building so tall that occupants of its highest floors would look out upon the world from 32000 meters, with near vacuum conditions outside. Solar panels at the top would supply power, with water being supplied and replenished from clouds and rainwater. A transfer station would allow people and goods to move between the orbiting tower and the surface. As for the cost of building such a tower, one prefabricated unit at a time, plugging modules into an extendable core, the firm sees clear skies:

Harnessing the power of planetary design thinking, it taps into the desire for extreme height, seclusion and constant mobility. If the recent boom in residential towers proves that sales price per square foot rises with floor elevation, then Analemma Tower will command record prices, justifying its high cost of construction.

Want to get in on the ground floor? Not me. There’s plenty to question about this operation even if a market did emerge to support it, but the visuals are breathtaking, with spectacular vistas from residential windows aboard the building (craft?) and the futuristic imagery of a skyscraper emerging slowly out of the clouds for those below. Clouds Architecture Office trades off recent space news like the European Space Agency’s study of and landing on Comet 67P/Churyumov–Gerasimenko and NASA efforts at asteroid retrieval, which involve relocating a tiny asteroid to a new orbit. We’re already landing on comets and talking about moving asteroids, right, so why not stretch out the notion that much further? But Analemma Tower is a long, long stretch indeed.


Image: The Analemma Tower as it might appear over New York City. Credit: Clouds Architecture Office.

If it were ever built, the tower would certainly be an unusual place to live. The bottom of the structure is seen as a shopping and dining area. The firm talks about business being conducted above this zone in the lower and middle sections of the tower, with the residential quarters approximately ⅔ of the way up. The sizes and shapes of the windows in the building would change with height because of the pressure and temperature differentials Analemma would experience. Those at the top of the tower would receive an additional 40 minutes of daylight per day because of the curvature of the Earth, says the Clouds Architecture Office website.


Image: Views through the windows of the Analemma tower, their shapes adapting to conditions outside. Credit: Clouds Architecture Office.

Because Dubai is the home of the world’s tallest building, Burj Khalifa, it is the firm’s choice for construction of the modules that would make up the tower. Exactly how building components would be delivered from the ground to the gradually growing core is not clear. Images of people parachuting past the tower’s windows suggest one quick way to the surface, though hardly one the average business person would be likely to take.

Can we create cables to support such a structure? And what about moving a sizeable asteroid into Earth orbit? NASA’s own plans in its Asteroid Redirect Mission have called for nudging a multi-ton boulder and pushing it into a stable orbit around the Moon, where it could be the destination of a manned mission that would bring samples back to Earth. That’s a $1.25 billion project in itself. The size of the asteroid Clouds Architecture Office is talking about isn’t specified, though it would far exceed the small rock NASA hopes to maneuver.

And consider the point that Sara Chodosh brought up in Popular Science in a piece appropriately titled This building hanging from an asteroid is absurd – but let’s take it seriously for a second. What happens to residents in a building this tall when they need an elevator?

The fastest elevators in the world are in The Shanghai Tower and move at 20.5 meters per second, so a straight shot to the top of the Analemma would take you just over 20 minutes. And that’s assuming there is a single elevator that goes all the way to the top. One of the logistically challenging things about building very tall structures is how you fit in enough elevators… The easiest way around that is to not require all of the elevators to go all the way to the ground (STRIKETHROUGH), er, first floor. You can stack elevator shafts on top of each other and simply have sky lobbies. So maybe you take an elevator from floor 1 to floor 50, then get off and take another from 50 to 100, and so on. Keep in mind that you’ll have to wait for the elevator to come each time, and with thousands upon thousands of residents you’ll probably be waiting a while.

Indeed. But there’s something to be said for black sky dreaming, and I love the visuals here. So while I’m not expecting to see Analemma appearing in the sky over New York any time soon, I do get some of the same buzz from the concept that I find in good science fiction. In fact, Analemma reminds me of some of Alastair Reynolds’ creations, particularly the world he portrays in novels like Chasm City (in his Revelation Space sequence). Chasm City is packed with mile-high skyscrapers, its planet surrounded by the Glitter Band, thousands of orbital habitats, all of which are threatened in the novel.

The people behind Analemma Tower have to be science fiction buffs. So why keep this idea on Earth? Geoffrey Landis has pointed out that at 50 kilometers above the surface of Venus, the pressure is about 1 bar and temperatures range between 0° and 50° Celsius. Here we wouldn’t need to be tethered to an asteroid, but could set up floating colonies in the Venusian clouds, where a human breathable air mixture is itself a lifting gas. Michael McCollum has likewise envisioned floating cities in the atmospheres of the outer gas giants. A skyscraper emerging out of the clouds may indeed be in our future, but I’m not sure Earth will be where we build it.

A note to the readers: Please help me out with further science fiction references on floating buildings/cities. I’m struggling to remember one recent depiction of a floating structure that moved between planet-bound cities — was it in Stephenson’s Seveneves, in the far future section of the novel? If so, I can’t find it. Your help on this is appreciated.


Comments on this entry are closed.

  • Andrew Higgins March 30, 2017, 11:58

    So, in other words, built a space elevator 99.99% of the way to the ground, but then stop just short of having it do something useful.

  • Scott Guerin March 30, 2017, 11:59

    Correct, Seveneves has a “hammer” that lowers itself to the ground periodically. And of course there is Cloud City in The Empire Strikes Back.

  • RJMeyers March 30, 2017, 12:16

    Since you mentioned Alastair Reynolds, his series of short stories involving Merlin (Merlin’s Gun, Hideaway, Minla’s Flowers, and The Iron Tactician) make reference to a Palace of Eternal Dusk, a small city/large palace structure that races around the equator of a planet at supersonic speeds, keeping pace just behind the sunset. It uses some hand-wavy anti-gravity and other imaginary tech.

    Regarding Analemma Tower, wouldn’t drag from the atmosphere eventually de-orbit the asteroid? You’d have to be constantly adding energy into the system to keep it afloat, right? Seems like a major problem to me.

    • Paul Gilster March 30, 2017, 12:50

      Good point re drag, and I don’t see it considered anywhere in the material we have so far, but this is just a barebones sketch to this point.

      • MGP2001 March 30, 2017, 13:51

        It’s geosynchronous, so no motion with respect to the ground, so no drag. I’d worry more about electro-magnetic effects of running a conductor thru a earth’s mag-field. Of course, there’s the weather. Also, what magical material is this cable going to be made of, carbon nano-tubes? No ones mass produced this material yet.

        • Jens Knudsen March 31, 2017, 12:13

          It should not be too hard to do some preliminary work on the question of materials. Is it so that none of what we have available today can be used? Producing millions of tons of carbon nano tubes sounds exotic. But even if we could, would they do it? Are there other options?

        • Dani Eder April 1, 2017, 13:42

          The design is proposed to be geosynchronous, but not geostationary. The anchor asteroid would be in an inclined orbit, so that the tower traces an analemma patten (figure 8) with respect to the ground. The bottom end would then experience north-south motion, and some amount of drag because of it. I see several problems with this.

          The center of mass is at synchronous orbit, where gravity and centrifugal acceleration are balanced. It can follow an inclined orbit without problems. The lower parts are not in force balance. In order for the bottom to be accelerated north and south, the cable must be inclined. In that case, the distance to the ground changes, and a slender cable is subject to all kinds of dynamic vibrations. The simplistic design also seems to ignore tidal effects of the Moon and Sun

          > what magical material is this cable going to be made of, carbon nano-tubes?

          The carbon-carbon bond, in the form of diamond or nanotubes, is theoretically strong enough. But in practice, macroscopic objects are never perfect. Imperfections arise either in manufacture, handling and shipping, or exposure once in use. Thus, current carbon fiber is about 55-85% carbon crystals, whose internal structure is the C-C bond. The remainder is other forms of carbon and other elements. Carbon nanotubes are individually strong, but they have finite size and the bonds are not as strong between them.

          It is estimated that well-made macroscopic carbon nanotube threads or cables will ultimately reach three times the strength of current carbon fiber, but this is still 5-10 times less than theoretical strength, and not enough for a practical space-elevator type structure around the Earth.

          • Jens Knudsen April 2, 2017, 8:51

            In my ears, that basically means we can’t do it?

  • Zack Russell March 30, 2017, 12:31

    Paul, you are indeed correct about SEVENEVES depicting a city suspended from space and tethered to a “Big Rock” counterweight. It was called Cradle, but was configured a little different than the Analemma concept. Cradle (first appearing around p.602) was a city built into an large rock (rather than a slim tower), hanging just above Earth’s surface. It would “land” at several points around the map.

  • Tom Pliska March 30, 2017, 12:35

    Obviously, there’s Cloud City in the Star Wars epics. Uses fantasy tech, though.

  • mlockmoore March 30, 2017, 12:38

    Probably not the first to post, but how about:
    Cloud City / Bespin / Star Wars V: The Empire Strikes Back.

  • Paul Gilster March 30, 2017, 12:49

    Thanks to all for the suggestions so far, and Zack for the Seveneves confirmation. The book is long enough that I couldn’t put my hands on the reference!

  • Ron S March 30, 2017, 13:07

    Lots of floating cities in fiction. I remember them in Niven’s Ringworld and in Adam’s Hitchhiker’s Guide to the Galaxy. Other examples I can’t specifically place off hand.

  • off-nexus March 30, 2017, 13:20

    Am I the only one seeing that the orbital mechanics don’t work. How do you hang over New York city which is a long way from the equator? If the asteroid is in an inclined equatorial orbit you’re over New York city for a few seconds every 24 hours.

  • Charley March 30, 2017, 13:20

    You mean to tell me that this silly thing would be a floating skyscraper that would actually dips into the Earth’s atmosphere ? That’s the most ridiculous thing I ever heard; there would be enormous drag on the object which would eventually cause it to de-orbit both itself and the asteroid it was attached to. That’s just simple physics, so anybody who think this thing would work doesn’t know anything about practical mechanics. When it was first suggested I thought they meant that it was going to be above the Earth’s atmosphere, which would have gravitational perturbations to have to deal with. I’m definitely not going to buy into that real estate option…

  • Charley March 30, 2017, 13:26

    That got me to thinking about one other thing – Paul, do you or any of your readers happen to know what the force would be on a per square foot basis for a structure that would start on the surface of the earth and reach up into the vacuum of space say about 230 miles ? I’m wondering what would be the stress on the footpad that such a skyscraper would exert on the earth, and whether or not such a force would exceed the material strength of all known materials that we now possess

    • Larry Kennedy March 30, 2017, 15:03

      NASA did some study on a structure built into space some years back. I think they were only talking about around half the height you mentioned. I don’t remember what they called it and not sure where you could find specifics.

      • Alexander Tolley March 30, 2017, 16:57

        There is the 15 km high tower being research at ASU as part of the Hieroglyph project initiated by Neal Stephenson.

        • Larry Kennedy March 30, 2017, 19:07

          This was more like 100 miles + as I remember. A serious look quite a few years ago.

        • Patient Observer March 30, 2017, 22:29

          Thanks for the link. He was struggling to find a root cause of the loss of “thinking/imagining big” since the 1960’s. I offer an explanation: the triumph of financial capitalism over industrial capitalism.

          • David April 1, 2017, 23:45

            Yes….check out Rise and fall of American growth

    • Larry Kennedy March 30, 2017, 15:58
      • Dani Eder April 1, 2017, 14:09

        Oh, hey, in one of the references (Smitherman, “Space Elevators”), I contributed the “Space tower” portion of the work.

        I was at Boeing’s space systems division at the time, and my efforts were directed at towers up to 20 km tall. This was because (a) Boeing had a lot of experience with carbon fiber structures that operate in the 0-20km environment, (b) there are near-term practical applications for towers this size, and (c) before you attempt anything taller, you want to get experience with intermediate size towers.

        The biggest problem to deal with is wind loading. Wind velocities generally increase with altitude (no ground friction or obstructions to slow them down), and the bending moment becomes larger the taller you build. My solution was to use a fractal truss (The Eiffel Tower is an example), to minimize cross section area, and mount pivoting airfoils around the tubular truss elements. The airfoils reduce drag forces on the structure by about a factor of ten.

        The next problem is construction workers in space suits. That didn’t seem very practical, so my approach was to build the tower “from the top down”. You assemble the top section of the tower at ground level, jack it up one structural bay, then assemble the next section under it. Repeat as many times as needed. Hydraulic jacks are amazingly strong, and this way all the work happens near ground level.

    • Dani Eder April 1, 2017, 13:48

      Footpad stress is not a problem, since you can distribute the load over a larger area in a short transition region. Thus, a 1 meter wide column can be tapered into a cone in the bottom 50 meters, becoming 5 meters wide, and reducing the stress by a factor of 25. A succession of steel plates and concrete footings can then further distribute the load until the bedrock can support it.

      • Michael April 1, 2017, 16:14

        There is also ice, ice can exert a huge mass load to a structure over a certain height, I personally find the idea in dreamland, too many lives dangling by a thread. Better to build from the floor with a wide base than from a thin vulnerable cable.

  • Alexander Tolley March 30, 2017, 13:47

    Robert McCall’s speculative art had quite a few floating cities as a theme.

    SciFi includes the Star Trek TOS episode “The Cloud Minders” with the floating city, Stratos.

    Clarke’s “3001: The Final Odyssey” depicts the interiors of the vertical towers that anchor the geosynch structure and are built out elevators.

    The gods have always lived in the skies or on inaccessible mountain tops, high enough to stay out of reach, yet close enough to descend and mix with humankind. The Analemma Tower seems to be this design studio’s latest version of that (see their cloud cities on their website). Unlike the space structure, Elysium, this tower is far more accessible from the ground, allowing our super-wealthy gods of tomorrow to cavort upon the Earth.

    Such a tower would be an easy target of terrorism. Ground or air-launched projectiles would be devastating. Cutting the support cable would see the whole massive structure crash to the surface. It might look like those movie train wrecks where everything collapses from the point of impact. Would there need to be escape pods everywhere to allow for such an eventuality?

    Like so much fanciful, speculative architecture, there seems to be no obvious commercial viability. Even is te unobtanium was available to build such a structure, what is the advantage of such a tower over other, simpler structures, even floating or hovering ones? It seems to achieve nothing other than provide a view. A ground-based building showing high resolution wall screen views from floating cameras would be much simpler and achievable with technology that is already near commercial availability. Isolation from humanity? A gated or island community would be more suitable. Even the Burj Khalifa is not fully occupied (Wikipedia) despite the huge amount of oligarch money looking for real estate to hide in.

  • George King March 30, 2017, 13:58

    The skyscrapers were grounded rather than floating, but it reminds me of I think it was The World Inside by Robert Silverberg.




    I can’t be sure because it’s been over four decades since I read it. We lived for a year in Danvers, Massachusetts, and the library there had an excellent science fiction section. It was in an old house. I remember many an afternoon perusing the stacks with the wood floor creaking and the lengthening shadows of the trees visible through the windows, before transporting myself to the far reaches of imagination in their collected works.

    • Paul Gilster March 30, 2017, 14:47

      Your library memories are so similar to my own, George. A magical time!

  • Bynaus March 30, 2017, 14:14

    This is essentially a building built onto a space elevator. Its cool-looking, but it suffers from the same problem as the space elevator: you need a material of sufficient strength to support it all. The additional weight of the tower makes that even harder.

    Apart from the drag, another problem I can see is the eccentric orbit they suggest: so this means that when it moves slowest, it will also be highest up. And with only the slightest eccentricity, at a semimajor axis of 36000 km you will be dipping that tower in and out of the atmosphere (so one would need a re-adjustable tether?).

    But I agree that we should think more about floating cities. After all, we have five worlds in the solar system with close to one Ge of surface gravity – and on four of them, we can never touch the ground.

  • Stave March 30, 2017, 14:24

    Larry Niven’s Ringworld has a derelict floating city, or at least a city of floating buildings (those that have not crashed). I don’t recall how he tap dances around the mechanism though.

    • Ralph March 30, 2017, 22:49

      Niven postulated a Ringworld made out of ‘scrith’ and IIRC there were superconducting grids and magnetic fields involved, or some kind of field that repelled scrith.

    • ajay March 31, 2017, 7:36

      Magic, basically. Thrusters which somehow repel the ringworld foundation material.

  • Dave Moore March 30, 2017, 14:31

    Let’s do some basic math here: If you have an orbiting object in an inclined 24 hour orbit, it traces a figure 8 path over 24 hours with the Northern and Southern most points at the latitude of its inclination.

    New York’s latitude 40 North. This means the skyscraper will cycle between 40 N and 40 S every 12 hours or 80 degrees. A degree is approximately 60 miles wide. 4800 miles in 12 hours is an average speed of 400 mph. The velocity, however, follows a sinusoidal curve slowing to zero at its Northernmost and Southernmost points. So we may have problems with a sonic bang over the equator.

  • Larry Kennedy March 30, 2017, 14:40

    Sounds like real blue sky speculation(:
    Yeah, I know.

  • Paul Gilster March 30, 2017, 14:48

    Had forgotten about the Ringworld reference — been a long time, though I do remember most of the novel pretty well. Also 3001, another one I’ve read but had not called to mind.

  • LuigiG March 30, 2017, 15:51

    I find that the first image alone is enough is enough to sell the non-extant product, in a shut up and take my money sort of way.

    Does anybody remember the Trade Authority Handbook(s)? These floating cities depicted by non other than the maestro Angus McKie


    can be found in the first volume.

  • Tom Baty March 30, 2017, 16:09

    What happens if a piece of space junk slices the cable up near the asteroid anchor???. If I remember in the Red, Green and Blue Mars series was there not a skyhook cable that was severed and it came down on the planet Mars with disastrous results. For as long as this cable is stated to be it seems the cable could wrap around the entire Earth at supersonic speeds crashing down who knows where. To idealist (even if the technology existed) not at all useful as a space elevator could possibly be. No thanks..I’ll pass!!!!

    • Dani Eder April 1, 2017, 14:29

      In real life engineering, as opposed to artist’s concepts and science fiction stories, we take human life and property damage seriously. Space debris and meteoroids are fairly well understood hazards, and we know how to design “Whipple shields” to provide partial protection. They are basically a layer of material stood off a distance from the load or pressure bearing structure.

      The kinetic energy due to typical orbit impact velocities greatly exceeds the melting or boiling point of all materials. So pretty much anything that hits will vaporize itself, and some of what it hits. The Whipple shield causes this to happen away from the structure, and the spray of vaporized material doesn’t damage the structure. This doesn’t protect you from a enough large object, which punches through the shield without completely vaporizing, but large objects are less common than small ones, typically with a 3.5 power law vs diameter.

      For large structures, that have a lot of exposed area to hit, the solution is to use multiple redundant cables, with load transfer around a break. Bridges and skyscraper columns are designed this way, so it is not a new idea. Loss of single structural element, or even several, does not cause the whole structure to fail.

  • Douglas Loss March 30, 2017, 16:38
  • Greg Hullender March 30, 2017, 16:47

    Two things constrain the orbit of the asteroid: it has a 24-hour period, and it must be stationary once a day directly above New York City at apogee. This lets us compute the orbit, and it has an eccentricity of 0.1428. This means at apogee it’ll be 41,900 km above New York. At perigee, it’ll be just 29,800 km above the ground and moving 624 m/s relative to it.

    So even if the skyscraper touches the ground at perigee, it’ll still be 12,000 km about NYC at apogee. I don’t think this idea works out at all.

  • Geoffrey Hillend March 30, 2017, 18:17

    The physics of the idea is that it is impossible since it’s own weight would not support itself, and the time it would take to make it, and the cost is astronomical. We could build an interstellar spacecraft for cheaper and less time, a fiasco.

  • Michael Fidler March 30, 2017, 19:48

    Has no one noticed that this would work as a tower crane with the pivot at the geosynchronous orbit point. Just put on the ion rockets at the asteroid and in the opposite direction below the pivot point and it will swing the lower end up to GSO! Now you have a nice crane to build a GSO ring-world. You could also bring asteroids into a factory on the counterweight asteroid and process the load for the main structure of the ring-world with the more advance materials and equipment being brought up from earth when the skyscraper is lowered. The whole process would be automated with AI and the ring-world would be laid out from the crane like you would lay a road out or a bridge, sections at a time, all being joined together. The question I’m wondering about, when you finish this ring-world would the centrifuge effect of this spinning mass moving at 6900 MPH create artificial gravity and at what G force. If it is a high G force it could tear the ring-world apart! Or would there be no centrifuge gravity at all???

    • Michael Fidler March 31, 2017, 10:14

      Just realized something, bringing in asteroids for the structural part of the ring-world may be the way to pay for the whole thing, all the precious metals in the asteroids could be brought down to earth and could sell in the trillions to $10,000 quadrillion dollars! And there’s more, what if a miniature black hole was at the center of one of them!!!! You guys need to start thinking on a planetary scale, this could be like the Spanish and the gold, jewels and who knows what else that they brought back from the new world, only this would be a real New Age!

      • Alexander Tolley March 31, 2017, 15:54

        (…) this could be like the Spanish and the gold, jewels and who knows what else that they brought back from the new world, only this would be a real New Age

        The gold from the New World caused inflation in Spain. It did them little good. Within a century, the defeat of their Armada against England put their empire in jeopardy and they were surpassed by the Dutch and then later, Britain, as major naval powers.

        When you supply huge amounts of anything, the price rapidly declines. The low cost of diamond was one of the economic background ideas in Stephenson’s “The Diamond Age”. Space resources are best used in space, where the high cost of delivery from earth keeps their value (at least initially).

        • Michael Fidler April 1, 2017, 2:12

          Yes, you are absolutely right, and it caused a major depression in new world that the natives have still not recovered from!!! This is a matter of perspective and it will be 50 to a 100 years before any of this could take place with a ring-world taking possible that long to build. That said and with the problems of a ununified Earth the best place to build a ring-world is Mars, you already have two asteroids in orbit around it and a huge number nearby, plus a smaller orbital radius. “The Martian geostationary orbit altitude is only 13,634 kilometers (so an orbital radius of 20,428 kilometers, or about 3,000 kilometers inside the orbit of Deimos).” (From Stationkeeping in Mars orbit, Planetary Society) So will the Mars Ring-world become the new Mecca?


          • Michael C. Fidler April 1, 2017, 19:27

            The correct altitude above the Martian surface would be 17200 kilometers for geostationary orbit. With a decrease in orbital speed of Deimos it would be brought closer to Mars and could be used to build a monolith to the Martian surface.

            • Michael Fidler April 2, 2017, 9:25

              Or you could make Deimos into a prison and send all the terrorist there to build it. ;- }

            • Michael Fidler April 2, 2017, 23:05

              In Emily Lakdawalla article on Stationkeeping in Mars orbit she bings out the problem of the high deltaV do to the volcanic regions on Mars. How would these effect the stabability of a ringworld in GSO around Mars? How about trying these problems on making these structures on binary asteriods near to Earth? Especially a small ringworld that could be spun up for gravity like in every sci-fi film! ( 2001, etc. )

      • Dani Eder April 1, 2017, 14:43

        The Platinum Group Metals (PGM) are located below Iron, Nickel, and Cobalt on the Periodic Table, and hence chemically compatible. They will sink to the core of any protoplanet with enough Iron and enough heating, since Iron is the densest common element. Metallic asteroids come from the cores of such protoplanets, which later got smashed up in collisions. The large asteroid 16 Psyche is thought to be the bare iron core from such a protoplanet.

        Typical metallic asteroid composition is 90% Iron, 9% Nickel, ~1% Cobalt, and trace amounts of the heavier elements like the PGMs, because that is their relative abundance when formed in supernova explosions and radioactive decay afterwards. In particular the PGMs occur at up to 50 parts per million, although the exact amounts vary across meteorite samples.

        So the problem with precious metals mining from metallic asteroids, is the metals are mixed with more than 20,000 times as much base metals. The Iron-Nickel-Cobalt alloy is worth much more than the PGM component, because currently *anything* in high orbit is worth $6000/kg, because that’s what it costs to launch it from Earth. The PGM component of the asteroid ore is only worth $1.50/kg. That’s $30,000/kg average price of precious metals x the ore concentration of 50 ppm. It’s not currently worth the bother of extracting.

  • john walker March 30, 2017, 22:05

    My immediate reaction to this story was that it was an April Fools joke erroneously published a couple days too early. It’s a classic half baked idea that ignores numerous physical realities. The true joke in my opinion is that this preposterous idea has repeatedly been headlined for days despite its laughable errors. Reminds me of the recent wave of reports claiming potatoes could and had been grown in a Mars like atmosphere. No. They weren’t. And no they can’t.

  • Patient Observer March 30, 2017, 22:34

    The idea of a sky tower floating majestically above the peons was painfully stupid. A much more plausible scenario of the wealthy looking down on 99.999% is the movie Elysium.


  • Morti March 31, 2017, 2:17

    It could be a decent alternative to space elevators especially if it doesn’t require any materials we don’t yet have.

  • The Questioner March 31, 2017, 2:53

    This idea is stupid and dangerous. One well-placed missile will drop a kilometer-sized bomb across a megalopolis and kill millions. Sheer idiocy.

  • Brett Bellmore March 31, 2017, 5:58

    There’s the floating city of Tiphares in the manga “Battle Angel Alita” (Gunnm in Japan.) Underneath is a slum called “the scrapyard”, living off junk the Tiphararians toss over the side. Originally a fully functional skyhook, they’d cut off the bottom segment due to a war with the surface.

  • Robert G March 31, 2017, 6:09

    I vaguely remember some sort of earth-space spanning structure in Benford’s sequel to Clarke’s ‘Against the Fall of Night’. Can’t remember the details as it was a long time ago I read it.

  • Robert G March 31, 2017, 6:10

    Benford’s book was ‘Beyond the Fall of Night’.

  • Robert G March 31, 2017, 6:24

    If we had a floaty balloon city like this on Venus, it wouldn’t need a cable to keep it aloft, as you mention, but a cable would be useful as a way of connecting it to space for transport. Seeing as there would be no need or point in aiming for a geosynchronous orbit/positioning, the question then becomes, if we had a floaty city at an appropriate altitude for the right temperature/air pressure, and if this city was keeping pace with the equatorial winds around it at that altitude, do we get any sort of sane/usable orbit for the tether and the rock at the end of it? Similar calculations to the Earth-space elevator, but with maybe different results. Also, given Venus’ gravity is around .9g requiring less from the cable material, there are no natural satellites and the amount of human-built space junk objects can at present probably be counted on the fingers of one hand, this might be an idea with legs!

  • Paul Gilster March 31, 2017, 8:22

    Thanks to all for the science fiction references — had forgotten some of these, while others were new to me. I’m surprised no one has mentioned the four Blish novels, later published together as Cities in Flight. Love that spindizzy… ;-)

    • Larry Kennedy March 31, 2017, 10:24

      Good point. I think the spindizzy would compare nicely to the present subject.

  • Jeff Wright March 31, 2017, 13:28

    The towers of Thalarion were said to be visible days before arrival:

  • Daniel Suggs March 31, 2017, 14:21

    This idea reminds me a little of the ‘starscrapers’ in the ‘Night’s Dawn’ trilogy by Peter F. Hamilton. They were like spikes sticking out from the surface of hollow asteroids. The starscrapers were living spaces and the asteroids were spinning to provide artificial gravity for them and park lands inside the hollows. Probably much safer and even cheaper than this.

  • Pasander March 31, 2017, 15:37

    The tallest building on Earth is nearly a kilometer high. If you build much taller than that, you will need airlocks for every 2-3 kilometers of height. Maybe the elevators could serve that purpose. But you certainly wouldn’t have staircases extending all the way from the top to the bottom of the building. So, in case of fire, use the elevators!

  • Wojciech J March 31, 2017, 18:15

    I actually like this idea, people have criticized it for being unrealistic and but I think it is important to have grand visions of tomorrow. Otherwise we would be drowned by banality.
    Also fans of Reynolds can rejoice, since he recently announced that new novel in Revelation Space Universe will be published. It will be a sequel to The Prefect.

    • Patient Observer April 2, 2017, 9:52

      Yes, a grand vision for the elite of the elites. It probably won’t inspire most kids to do anything other than to throw stones at it (assuming that in an alternate reality alternate physics it could be built).

      My take on grand visions would include the colonization of Mars and space habitats with its population drawn by lottery of those that meet health and skills requirements.

  • Geoffrey Hillend March 31, 2017, 18:58

    The airlocks would not be the main problem which would be the foundations not being strong enough to support the enormous weight if one wants to build a skyscraper like the one depicted in this article Skyscraper in the Clouds. The foundation would have to be much wider. I don’t think we would build a skyscraper with ordinary steel such as one depicted in this article. It would collapse under its own weight. Physicists have yet to calculate the limits of how tall we can build a skyscraper and I speculate that a 100 mile tall skyscraper is not possible at least with today’s technology. We don’t have the technology and what we do have makes the cost and time in building such a skyscraper completely impracticable. It is too imaginary and is science fiction. Watch out for the rotation! The skyscraper follows the rotation of the Earth and sweeps up meteoroids and micro-meteoroids along its length which collide at Earth’s rotational speed plus whatever kinetic orbital energy and momentum they have depending on their direction and angle. Better hope they are not too big.

  • Mike Runyan March 31, 2017, 20:01

    I think the earth-side termination should be more airship-friendly – landing pads would be needed.

  • xcalibur April 1, 2017, 5:32

    There’s no arguing with the ‘coolness’ of this.

    However, I see space elevators and spacescrapers as impractical. The wind-shear would be formidable, especially since the wind is stronger at higher altitudes. Any structure spanning such a height would have to cope with winds pushing and pulling at different intensities and directions along its length. Then when you’re out in vacuum, there’s hard radiation, micrometeroids, and space junk to deal with.

    While this is not viable, brainstorming and thought experiments can still be useful.

    As for Venus: while we could build floating cities there, I think terraforming is a reasonable prospect. It would mainly require bombarding the planet with enough hydrogen + a catalyst for the Bosch reaction (iron, cobalt and/or nickel). From there, you would just need to add oxygen, stabilize the climate, and generate magnetic fields.

    There are a number of fictional floating cities. Others have mentioned Cloud City from Star Wars — I’d like to add that it was in the atmosphere of a gas giant. Younger people who grew up playing video games are familiar with floating constructs from Final Fantasy, Chrono Trigger, and other games.

    • Dani Eder April 1, 2017, 14:53

      The least expensive way to start terraforming Venus is to build lots of orbiting sunshades to block out the Sun. They can be quite thin compared to the 900m equivalent thickness of the Venusian atmosphere. A 1 km metallic asteroid might be sufficient if formed into sub-mm thick sheets.

      Once the Sun is blocked, the atmosphere will start to cool, and eventually the CO2 will combine with surface basalts to form carbonates. Since the scale height of the atmosphere will decrease with temperature, the surface pressure and temperature of the high spots will go down faster than the low-lying areas, so those could be the first places for sending down robots, followed by crew habitats. We might build tall towers to start with, to gain more height advantage. There is no shortage of carbon on Venus to make carbon fiber out of.

      • Michael April 1, 2017, 16:02

        Might be better to have an asteroid at the Venus-Sun Lagrange point that is made into a reflective swarm of nano-reflectors to block the light from the Sun. Each nano-reflector uses energy and the Suns reflective light to move it about this neutral point, those that are damaged are replaced.

      • xcalibur April 1, 2017, 17:21

        Those are good ideas. However, hydrogen bombardment has the advantages of being quick and dramatic, as well as forming oceans.

        I could say much more on this topic, but I don’t want to go too far off on a tangent. If a future article focuses on Venus and/or terraforming, then I’ll go in-depth.

  • Steve Bowers April 1, 2017, 12:40

    Instead of a skyscraper, you should put a scoop at the bottom of this tether to collect air for export to space habitats. If there were thousands of habitats in Earth orbit they would need significant amounts of oxygen and nitrogen for pressurisation purposes; the closest source of these materials would be Earth’s atmosphere. Maybe water vapour and carbon dioxide would be worth harvesting too. Of course you’d need solar power collectors somewhere on the tether to counteract the drag.

    As a nod to the original idea, maybe a hotel somewhere on the tether would make a bit of income- but it would be a challenging place to visit.

  • LocalFluff April 2, 2017, 15:20

    Maybe the millions of tons launched to orbit in order to construct that thing could be put to better use, such as exploring space instead of building flying skyscrapers? And when the elevator suddenly stops half way, again, all transportation is off? A single lane is not logistically very attractive. Compare car with train. You need a car to get to and from the stations anyway, and taking it all the way relieves you of time tables.

    Maybe this kind of concept somehow makes sense in a distant future. But it does nothing at all for getting us there from here (which ironically is what one would expect a transportation system to do).

  • Geoffrey Hillend April 2, 2017, 17:00

    32000 meters is actually only 19.88 miles, so it does not sweep up micro-meteoroids. I am sorry for the miscalculation, but it still might not be able to support it’s own weight. I would like to see the calculations that show it could support its own weight.

  • ljk April 25, 2017, 20:09

    Lots of cool images and video:


  • ljk August 15, 2017, 22:57

    Building Huge Structures in Space: ‘Archinaut’ Takes Another Step

    By Mike Wall, Space.com Senior Writer | August 14, 2017 06:30 am ET

    MOFFETT FIELD, Calif. — Made In Space just took another step toward its goal of building telescopes and other large structures off Earth.

    A 3D printer built by the California-based company churned out multiple polymer-alloy objects — the largest of which was a 33.5-inch-long (85 centimeters) beam — during a 24-day test inside a thermal vacuum chamber (TVAC) here in Silicon Valley at NASA’s Ames Research Center in June.

    The milestone marks the first time a 3D printer has created “extended structures” in a space-like environment, Made In Space representatives said here Thursday (Aug. 10) during a press event announcing the success of the June test. (The TVAC imposed the temperatures and vacuum of space, though standard Earth gravity remained.)