Megastructures by Starbrat (printer friendly) discuss (15 posts)

While most SF stories and adventures are based on or around spacecraft, planetary colonies or even space colonies, a few make use of structures on a scale currently unheard of. It is these megastructures and their possibilities I want to take a look at this month.

The Possibilities

The airless, microgravity environment of space is often seen as a hindrance to be overcome, but it can also provide unique environments. The lack of stress over large distances will allow the engineers of the future to design and build structures we can barely dream of. Large, delicate components don't need to support their own weight, so extremely fine structures can cover tens or even hundreds of kilometres without undue stress.


We looked at some possibilities of nanotechnology in the "Interstellar Trade" and "Future Medicine" article, but perhaps they will shine the brightest in the arena of space construction. Rather than laboriously processing raw material into large structures by hand, nano-assemblers could be programmed to reduce ores and produce simple structures on large scales (such as the turning of an asteroidal mass into a viable colony structure). Given the limtiations of nanite programming, simple tasks such as this are tailor-made for them. Taking this idea far into the future, perhaps hordes of correctly-programmed self-replicating technology could, given enough time, re-work an entire solar system into new shapes and purposes.

Allen Steele's "Labyrinth of Night" and Stephen Baxter's "Moonseed" have some fine examples of construction nanites in action.


Below are some literary examples of megastructures that you could use to spice up your campaign:

The Space Elevator

An idea first looked at at the turn of the twentieth century, Arthur Clarke's calculations regarding geosynchronous orbits allowed this idea to take full shape. A space elevator (sometimes called a "beanstalk") would consist of a vast length (tens of thousands of kiklometres in length) of immensely strong cable, running from the surface of the Earth to a space station in geosynchronous orbit (the station would act as a counterweight, preventing the beanstalk from toppling). Using only electrical energy (some of which could be generated just by the beanstalk's passage through the Earth's magnetic field), payloads and luxury lift-cabins could be hoisted to geosynchronous orbit at a fraction of the cost of a free-launch. Alternatively, the cable could stand free if it was twice as long, since the masses at either side of the geosynchronous mid-point would balance each other. Payloads launched from the far end of a "long" beanstalk could reach the asteroid belt without expending a gram of rocket fuel!

In fact, if two worlds were in a fully locked orbit with each other (such as Pluto and Charon in our solar system), a beanstalk could be constructed to form a permanent bridge between tham. In Charles Sheffield's "Summertide", the tidally-locked twin worlds of Quake and Opal are linked by a beanstalk structure left behind by an ancient culture whose bizarre and gigantic artifacts litter the galaxy.

The Ring-Structure

The artificial planetary ring is an extension of the beanstalk idea. Rather than relying on just a single beanstalk, an sufficiently advanced culture could construct several of these structures. To help them to maintain balance with a minimum of energy, a framework could be built to link the tops of these structures together, creating an artificial ring in orbit. Such a structure, simple but strong at first, could then be augmented with inustrial and agricultural structures, orbital habitats and even planetary defence systems. The sheer scale of living area and workspace opened up is staggering (a simple structure no more than hundred metres or so in width could provide as much floor-space as the island of Madagascar!).

Even Bigger Rings; The Ringworld

The author Larry Niven came up with an incredible idea. If an advanced culture needed more living room and couldn't find it easily, they would resort to creating their own. While most ideas are limited to the kinds of structures we talked about in the "Space Colonies" article, this structure is a whole order of magnitude greater. Taking the mass of a world like jupiter, one could create an artificial ring 2AU in diamater and a kilometre thick. It could be spun to provide constant centripetal gravity (and the disorienting coriolis forces would be undetectable in a structure this size). Put walls a thousand kilometres high at the edges of the ring and it will be airtight. Setting immense rectangular plates in an inner orbit would allow sectors of day and night to circle the ringworld, creating a day/night cycle. This kind of design would produce something with the same surface area as many hundreds of thousands of earths!

Of course, whatever material the ringworld was made of, it would have to have a strength many orders of magnitude greater than anything currently known, or else it would fly apart.

Lock Up the Stars

The engineer and visionary Freeman Dyson dreamed up a structure even more impressive than the Ringworld. He surmised that an energy-hungry civilisation would want to trap as much free energyn -in the form of sunlight- as possible. He envisaged a network of megastructures and vast, orbiting collectors that would be efective enough to essentially block off all of the star's light in order to produce energy. It would require the mass of all or most of a system's planetary bodies to produce this network, but it is at least thoroughy possible. the only way to detect such a system would be to look for a solar-mass star that only radiated in the infrared part of the spectrum (the captured energy would eventually be re-radiated as heat.

Successive ideas have even gone so far as to propose an SOLID spherical structure to totally encase a star. the mass of more than one system would probably be required for this enterprise, but it would create an enclosed environment in which literally hundreds of civilisations could flourish for millions of years or more. Assuming spin-induced gravity, the structure would be rather like a vast Bernal sphere, perhaps with open gaps at the "poles" to make for easy egress for spaceships of any and all sizes. The sphere's spin would keep the atmosphere concentrated around the equatorial regions.

Building such a structure around a sun-like star would be an utterly incredible feat, but maybe the use of smaller bodies would make the task easier. White dwarf stars in particular are very stable, since they radiate only by means of their residual heat energy ather than fusion reactions. The sphere structure could also be much smaller (say 0.05 AU in diameter), though still large enough to be utterly awe-inspiring to visitors from a more conventional civilisation.

Perhaps it is in structures like these that the last intelligent inhabitants of the Universe will stave off extinction when the last stars die a hundred trillion years from now.

One Ring to Rule Them All...

In his novel "Ring", an incredible story spanning the next five million years, Stephen Baxter created a structure simply called the Ring. It's a classic example of an astronomical puzzle watered with the imagination of a science-fiction writer.

Many tens of millions of lightyears from our own galaxy is a structure of galactic clusters known as the Great Wall. Some distance beyond this is a concentration of mass that is slowly but steadily pulling all the neighbouring galactic clusters (including our own local cluster) towards itself. Cosmologists refer to it as the Great Attractor. Baxter took this cosmological oddity and turned it into the most incredible structure I have ever come across.

Constructed by a highly advanced species called the Xeelee, its purpose was to create a spinning black hole so powerful it could create a stable gateway to other universes (they wished to flee this one since they had lost a struggle with another lifeform who were destroying the stars themselves). It was many lightyears in diameter, and the masses of several galactic clusters (!!!) had been compressed into the most massive singularity in the Universe. The whole thing was spinning at a good fraction of the speed of light, and it remained stable for at least a million years. Despite originally pitting itself against the Xeelee, Humanity was eventually also able to escape through it.

Of course, these splendid ideas aren't all the possibilities of megastructures. try to let your imagination go, and think on scales we normally apply to astronomy. Maybe a cluster of hot, powerful stars has been surrounded by a flower-like network of photocells that beam the energy through jump-gates or the like to every planet in a civilisation's control. Turning up the power a little, what about a power-collector array poised "above" a polar jet from an active black hole (it would need incredibly powerful engined to remain in place, of course). The energy such a structure could collect would be more than worth the cost of producing it.

The keyword when dealing with megastructures is "big". The usual scales and consideration don't apply.

I have seen the future, and it's large.

© Mark Peoples 2000.

Discussion forum

Ringworld problems and alternatives

Author: on Date : 16-06-2001

Reading your article, it's obvious that you've done a fair amount of the same reading I have... most likely a sign that one is getting up there in years. ;-) However, I did notice that you, like most others I've talked to over the years simply accepted Niven's math and physics regarding a Ringworld structure. The problem with his idea is twofold: first is that the distance of travel between the air at ground level and the air at 20-30 miles or so is miniscule on the scale of the Ringworld... but massive in regards to humans. Think about it - on Earth we rotate 1 time in 24 hours... and travel a distance of slightly less than 25,000 miles in that time. Our atmosphere creates jet streams of 300 MPH winds from a rotational speed of 1,000 MPH. Yet, in order to create a 1.00g pull on a 1.00au Ringworld, you end up with a speed of (I don't have the book in front of me but I do think the number is correct) of 77,000 miles per SECOND!!! With this being the case, and even taking air's relatively low retention of inertia into account, the windstorms whipping over a Ringworld would make it uninhabitable. The second problem is that anything not tied down loses inertia MUCH more rapidly than does the Ringworld as a whole... thus simply tossing something into the air (like Niven's famous floating cities) would make it shoot anti-spinward at a fantastic rate though it wouldn't be moving so much as it wouldn't be keeping pace with everything around it. I believe much the same problems would result from the ever-popular solid sphere version of a Dyson Sphere (as per the one in Star Trek:TNG) with the additional messes created by differing gravitational zones if you spun it to create gravity (for starters, all the air would pool around the 'equator' of such a Sphere) and the fact that it would likely soon explode from the massive amounts of solar exgassing which would be trapped. If you've comments on this, I would appreciate some knowing and constructive conversation on ways around these problems. The best alternative I have come up with is what I term a JoveRing (a small Ringworld built around a super-Jovian brown dwarf, with wall structures built across it every 50-100 miles (preferably with cities in them) to prevent the massive windstorm problems on a larger Ringworld). A second is the "String of Pearls" concept whereby one takes a series of sausage-like habitats and links them via flexible connectors around some astrophysical object.

post reply next »

Threads (list topics)

 Ringworld problems and alternatives by Dirkbert on 16-06-2001
RE: Ringworld problems and alternatives by TerroX on 16-06-2001
RE: Ringworld problems and alternatives by Starbrat on 16-06-2001
RE: Ringworld problems and alternatives by Dirkbert on 21-06-2001
RE: Ringworld problems and alternatives by ucntcme on 25-06-2001
RE: Ringworld problems and alternatives by Simon_Jester on 01-09-2004
RE: Ringworld problems and alternatives by Simon_Jester on 01-09-2004


login required to post to the discussion forum

you are not logged in
Register - Password Reminder

© Alternity.Net & AlternityRPG.Net 1999 to 2019. All Rights Reserved. Alternity™ owned by WotC.