Massive engineering projects?

[LordZarglif]

I am creating a hard-science SF campaign (a somewhat more optimistic one than my last dismal failure), in the vein of KSR's Mars Trilogy. I am looking for really massive feats of engineering for the setting, stuff like the space elevators, the Gibraltar bridge, O'Neill colonies, mass drivers, all the Martian Terraformation stuff, etc., that are achievable with (mostly) hard science, a couple centuries from now. any suggestions?

[Dr. Anomaly]

Well, let's see...by 'massive' do you just mean "huge" in size, or do you mean 'massive' as in 'big returns'? In any case:

1) Create "Larder" Asteroids. The need for food is never likely to decrease, and people will likely always be happier with "real" food rather than vat-grown yeast with flavoring added. To that end, moving agriculture off-planet (where you can maximize growing surface vs. volume ratios) isn't a bad idea. Dropping the results to the surface is essentially "free" in terms of energy budget, and solar power can provide the power to run the "larder" asteroids as well as of course providing the means for plants to grow.

There are several ways this could be done:

a) Hollow out asteroids to leave them as a (relatively) thin shell, perhaps a few hundred feet thick, then set them spinning (slowly) to give a modest gravity (say, 25% to 30%), spread soil, bring in water from a comet, and begin planting. Upsides: simplest and most 'realistic' in terms of 'hard' science. Downsides: expensive, time-consuming, and once operational it will take a long time to recover its start-up cost.

b) Bore a shaft into the center of an asteroid, fill it with volitiles (like water ice), and seal it back up. Give it a modest spin. Build giant solar mirrors (miles across but thin as mylar film, relatively cheap) to focus sunlight on the asteroid. Increase the temperature to the point were the rock becomes soft, but not molten. Both the spin of the asteroid and the expansion of the volitiles inside the core will combine to "blow up" the asteroid like a balloon. When it reaches the desired size and thickness of skin, turn the mirrors away and let it cool, then make an opening and set up housekeeping. Very cheap, relatively fast, and the mirrors can be recycled into use to provide sunlight for the plants inside (focus sunlight on huge froptic cable receptor bundles to "pipe" sunlight inside). Downside: due to cracks, etc. in the rock, the volitiles inside might cause a "blowout" during expansion, ruining the asteroid's structural integrity and setting it wobbling (possibly to the point of break-up).

c) Capture comets and cover them completely with an airtight, water-tight self-sealing membrane (some kind of specially-engineered plant would probably work best). Use giant, cheap mirrors to focus sunlight on the comets until they melt. The solids (rock, dust, etc.) will sink to the center, leaving a huge volume of water available for turning into a cultured biosphere in which you plant your choice of genetically-engineered plants and animals. Relatively cheap, but calls for a lot of genetic engineering skill, as well as potential problems with contaminants in the water (poisonous trace metals, etc.)

d) Actually build huge agro-stations from the "ground" up by traditional methods: girders, beams, panels, etc. Upside: most realistic. Downsides: time consuming, expensive, vulnerable (to meteor strikes), requires an entire manufacturing infrastructure to be set up in space to produce the structural materials.


2) Create Planetary "Slingshots". One problem with interplanetary travel is the necessity of carrying reaction mass with you for thrust. Then of course you must spend more reaction mass (energy) to move the as-yet-unused reaction mass...it can be a feedback spiral that results in relatively small payloads traveling slowly between worlds at a massive cost in energy. Even with fusion power and/or drives, you've moving a lot of mass simply for the sake of having that mass available at a later point to use as fuel then. An alternative would be a relative of the mass driver.

Picture a superconducting cable a few hundred kilometers long, spinning very slowly...just enough to keep it taught. Near the center sits the power station (either solar or nuclear, take your pick). To send something to another planet, you put the capsule at one end of the cable and, using power from the power station, create a tremendous magnetic field that pulls the capsule along the length of the cable. At an acceleration of, say, 3G over a distance of a few hundred km, you build up a very nice velocity, and the capsule is almost "pure" payload...no reaction mass for engines (since there are no engines on-board) and you leave your "engine" behind to be used by the next capsule. Of course this must be timed just right (so the spin will have the cable pointing at the destination at the time of release) and there must be another "tether" system at the destination to catch and slow the capules. Result: fast, relatively cheap transit between planets. Downside: you can't go anywhere that doesn't have a tether station, so the tether station must be either built on-site (by a construction crew that got there "the old fashioned way", in a reaction-drive rocket) or built at a construction yard and then boosted to the destination point by a reaction-drive rocket "tugboat".


3) Jovian Power Plant. Jupiter has a huge and intense magnetic field. You could make a very efficient power plant by running a superconducting cable entirely around Jupiter, in orbit, so it makes a complete, closed circuit. Set it spinning so the cable repeatedly crosses through the lines of Jupiter's magnetic field, and you'll set up fantastic electrical currents in the cable. Viola! A "clean", "simple" generator of such proportions that it could easily supply the power needs of the entire solar system, provided you have a way to efficiently "beam" the power to where it's needed.


If I think of any more, I'll let you know.

[Snarf]

Have you ever heard of Ringworlds? These are from the Ringworld series of books and I think there was one in the game Halo. It's like a big ring you can live on that encircles a sun and is spun to create fake gravity. It has the habitable area of a couple million Earths or something like that. Simalar to space elevators, it's realistically possible once you can make loads of super strong material cheaply.

picture: http://chemphys.phys.boun.edu.tr/~se.../ringworld.jpg

The inner ring blocks the sun sometimes to simulate nightime.

[DocMan]

And then you have the father of the Ringworld, the Dyson's Sphere.

Instead of having just a 1 AU radius ring around a star, Dyson said "Who cares about the stars! I want to catch all that sunlight!" He envisioned a hollow sphere (again, 1 AU in radius) completely encircling a star. Again, the sphere is spun to produce gravity, however, unlike the Ringworld, the gravity varies depending on where one is on the sphere. Full gravity is available at the equator and slowly decreases until one encounters zero gravity at the poles. This naturally causes problems with keeping the soil evenly distributed on the inside of the sphere.

Civilizations living inside a Dyson Sphere have LOTS of room to expand and unlimited solar energy. But they tend to lose sight of the rest of the universe because they can't see it in their day to day lives. Great for Xenophobic races. Especially since interloping star-faring races can't see your sun in the sky. An external defense system is imperitive to prevent the Sphere from being punctured by the odd roving asteroid, comet, or planet. But don't make enemies if you live on a Dyson Sphere as you live in a target so big it's impossible to miss.

Biggest problem is finding the resources and engineering expertise to actually build the shere. It must be built spinning (in orbit), and must be perfectly balanced in all phases of construction.

Doc

[Dr. Anomaly]

Dyson Spheres have a lot more trouble that just those hurdles. For example, if you set it spinning so you have "gravity", that only applies at the "equator" (where the plane of spin intersects the sphere). As you follow the inside of the sphere around toward the poles (where the axis of spin intersects the sphere) the "gravity" gets less and less until at the "poles" you have effective free-fall, and the atmosphere will start venting itself into the vacuum between the shell and the star. This will set up fantastic windstorms all across the inner surface as the atmosphere tries to empty itself via the poles.

In order for a Dyson Sphere to be habitable in the way usually envisioned (living on the inner surface) you've got to invoke true artificial (generated) gravity, not spin.

The reason I didn't mention either ringworlds or Dyson Spheres is that he requested ideas for things that could be realistically expected to be possible, using mostly 'hard' science, within a couple of centuries, and I don't think that either ringworlds or Dyson Spheres are realisitic possibilities just a couple of centuries from now.

[Agemegos]

I suggest that you not walk but run to your library to borrow a copy of Robert L Forward's Indistinguishable from Magic (ISBN 0671876864). Or buy it second-hand through Amazon.

This book will tell you all you need to know about beanstalks, rotorvators, magnetically-levitated towers, fountains, pellet streams, antimatter-powered rockets, using antimatter for explosive materials forming, interstellar lightsail vessls, starwisps, and lots of other ambitious concepts that are currently in the realm of hard SF. It also contains some of Forward's fiction: but you have read worse.

I can also recommend that you try a bit of Google research on "Stanford torus", "Bernal sphere", and "O'Neill cylinder". There is a bit of an overview at http://www.l5news.org/index.html

[LordZarglif]

I suggest that you not walk but run to your library to borrow a copy of Robert L Forward's Indistinguishable from Magic (ISBN 0671876864). Or buy it second-hand through Amazon.

This book will tell you all you need to know about beanstalks, rotorvators, magnetically-levitated towers, fountains, pellet streams, antimatter-powered rockets, using antimatter for explosive materials forming, interstellar lightsail vessls, starwisps, and lots of other ambitious concepts that are currently in the realm of hard SF. It also contains some of Forward's fiction: but you have read worse.

I can also recommend that you try a bit of Google research on "Stanford torus", "Bernal sphere", and "O'Neill cylinder". There is a bit of an overview at http://www.l5news.org/index.html

Wow! thanks, I'll be sure to get this. I know about the O'Neill Islands, I did mention them. Oh, and thanks, Dr. Anomaly.

I know about Ringworlds and Dyson Spheres. The Ringworld would take a material with tensile strength on the order of strong nuclear force (scrith), and that's pure rubber science. Anyways, I want the planets and asteroids to be there, and they require those to be cleared out. Anyways, you can plainly tell nobody's ever built one: if they did, it would be observable out to the curve of the universe.

[DocMan]

Sorry, reflex. Someone brings up Ringworlds, I just have to bring up Dyson Spheres to point out all the flaws in the idea.

Actually the mass driver idea is pretty good, but it's partially mis-stated. By using a mass driver for launch, instead of carrying no fuel, you only have to carry fuel for breaking and manuvering. Now, since the craft is most massive at launch, this is a significant fuel savings.

To establish a new nexus in your transport system, you send out constructor ships with enough fuel to slow themselves down into their desired orbit. The first few constructor ships are sent with the materiels to create a deceleration net to "catch" items. Once the decelerator is built, additional materials can be thrown and a new drive station can be built. Once the project is complete, the empty constructor ships can be thrown back home for refueling and redepoyment.

Doc

[keithcurtis]

Freeman Dyson did not propose a unified continuous sphere, but a collection of over a hundred thousand independant objects. While this is still pure fantasy in terms of our understanding of engineering, it is not the flat out impossibility of the common mis-perceived notion of the Dyson Sphere.

More info here .

Keith "How about a vast Europan Fishery?" Curtis

[Dr. Anomaly]

Freeman Dyson did not propose a unified continuous sphere, but a collection of over a hundred thousand independant objects.

Quite correct. But when someone brings up the idea of a unified sphere (as is usually done when someone talks about "Dyson Spheres") and suggests spinning them for artificial G, I just have to point out why that won't work.

[keithcurtis]

Beyond that, those few authors who use them have no appreciation for their A) incomprehensible scale, and B) Unimaginable engineering expertise to create.
I remember a intergalactic thief in some X-Men comic had a Dyson Sphere as her headquarters. If you have a Dyson Sphere (the bogus kind), what in the world would you ever need to steal!?!

I mean, the entire surface area of the earth could fit in there many millions of times over. And they are often portrayed as having miles(!) of levels. You could lose the entire population of a large space opera galaxy in one tiny pocket of that.

Keith "In my day we had Skylab, dangit, and we <i>liked</i> it!" Curtis

[keithcurtis]

How about permanent shuttles? KSR had one in the Mars trilogy, I believe. A shuttle with all of the living quarters, life support and such is on a permanent Hohman transfer orbit between any two planets. Then you only have to accelerate the people to speed. All of your life support payload is already there.

Keith "Or maybe just flying cars?" Curtis

[LordZarglif]

How about permanent shuttles? KSR had one in the Mars trilogy, I believe. A shuttle with all of the living quarters, life support and such is on a permanent Hohman transfer orbit between any two planets. Then you only have to accelerate the people to speed. All of your life support payload is already there.

yah, got those. IIRC, it started at Earth spinning at 1 Terran G, then gradually went down to .38 G, Martian Gravity.

[DocMan]

I remember a intergalactic thief in some X-Men comic had a Dyson Sphere as her headquarters. If you have a Dyson Sphere (the bogus kind), what in the world would you ever need to steal!?!

The character was Lila Cheyney. She was a mutant teleporter who couldn't teleport less than intersteller distances. She didn't OWN the Dyson Sphere as much as she found it. As far as she could tell, it was abandond. She never had the opportunity to fully explore it (WAY too big). It was a place to stash her loot and plan the next job. But there was no one around to deliver groceries.

Doc

[keithcurtis]

The character was Lila Cheyney. She was a mutant teleporter who couldn't teleport less than intersteller distances. She didn't OWN the Dyson Sphere as much as she found it. As far as she could tell, it was abandond. She never had the opportunity to fully explore it (WAY too big). It was a place to stash her loot and plan the next job. But there was no one around to deliver groceries.

Doc

That's pretty much what I remembered. I just thought it was a total waste and dismissal of such a huge concept. The Dyson Sphere should have been the story, not a throwaway teleporter character.

It's kind of like having a James Bond story where he briefly meets extraterrestrials for two paragraphs on page 58, and then they are barely mentioned afterward. You would read the book and say, "when the heck are they gonna get back to the ET's? What the heck was that all about?"

Keith "King of the so-so metaphors" Curtis