Have you actually read Ringworld? It covers just a tiny fraction of the world. A couple thousand miles from the point of impact, the remnant of a city, some isolated communities that don’t know they are on a ring, and a drag up Fist of God mountain. The main characters didn’t even realize there were “maps” of planets in the great ocean in the first book. There’s nothing about the Puppeteers engineering the superconductor virus, or Pak protectors, that is in Ringworld Engineers. They never get near the edges, no idea of the sludge pumps, spill mountains, or the effects of erosion on an artificial world, nothing about stolen attitude jets.
Also, the Ring is “a million miles wide”, wider than the diameter of the star. You could definitely see it all the way up and around, most likely only as slowly moving dashes with the naked eye near the zenith, but even a small telescope would show it. It really would look like a handle on a basket.
I know you like to appear infallible, but my opinion stands.
Or at least, that’s their story. In one of the later books, officially co-authored by Niven but basically officially-endorsed fanfiction, it’s pointed out that the flight of the Fleet of Worlds can’t possibly be a response to the core explosion, because at their current speed, they’re already facing a radiation hazard greater than what they’d get from the core, just from blueshifted light coming from in front of them, and have thus needed to develop means to protect against it. Their actual reason for fleeing, that they don’t even share with their own population, is to flee us, because they can’t predict our response to their meddling, and fear that it’ll be violent.
At least this explanation is consistent with what we know of the Puppeteers! I think Louis Wu’s being allowed to visit their homeworld(s) was considered a very rare privilege.
And that’s the key to all of these issues. You pretty much need complete control of all the fundamental forces of nature, control on a par with how we control electromagnetism. If you can shield, focus or switch off gravity, a lot more things become possible.
One of the later books explains that they bought world-moving engines off another race (The Outsiders, I think?) and installed them in the planets. Sort-of “safe”, until someone figured out how to make one explode.
And if your empire consists of a million planets, you can afford to lose one or two for the sake of a vanity engineering project. The thing about these massive constructions is that they are usually the product of civilizations vastly larger than ours.
It’s Star Wars canon that the energy cost of a single hyperspace jump of a single Star Destroyer is greater than the GDP of an average planet. It’s just that the Empire has lots of planets.
Not sure if I’ll get around to reading Ringworld, but quite a few of these answers seem to be getting quite far afield from my questions. Maybe another thread?
I’m not quite sure I was talking abut BDOs. Sure some - like the planet killer from Star Trek TOS - qualify. Others, like the Star Wars Death Star is moon-sized, but the operators definitely know who built it and why. The portal in the Dune movie was far smaller than moon size, but would sure seem to require considerable material and energy to construct and bring on line.
I guess that is a bit of an issue I have with some SF - that I basically need to ignore the issues with how things are afforded/built. If the story is good enough, I’m generally happy to just go along for the ride. But too often some little detail will catch my attention and I can’t get it out of my mind, leading me to question more and more details.
If you’re looking at the economics of building things in space that are big, but not world-sized big, you might want to read this book: Mining The Sky.
To illustrate this potential, Lewis includes an order-of-magnitude estimate of the economic value of the smallest known metallic (M-type ) near-Earth asteroid: 3554 Amun. With its diameter of 2 kilometers and assumed composition similar to typical iron-type meteorites, he calculated a mass of 3×1010 (30 billion) tons and a 1996 market value of $8 trillion for its iron and nickel alone, another $6 trillion for its cobalt, and $6 trillion more for its platinum-group metals.[1]: 112
If you have the technology and energy to move about a solar system at will, there’s lots of material out there to build things with. Cost of materials will be the least important element. The energy to process and move the materials is the limiting factor. So if you have cheap fusion, or some more exotic energy source, this is the least of your problems. As others have mentioned, at some point, the labor costs become the biggest issue.
Getting back to the original question, I think, in context of the series, that Star Destroyers and Death Stars are built the old-fashioned way. Someone makes components and others join them together.
While the Death Star is big, the Empire likes building big. They seem to love large open spaces (without railings!) in their constructions.
It most likely took 17 years to build the original Death Star, and longer for the unfinished but fully functional second one. That’s consistent with assembling it from parts. There seems to be no evidence of “nanotech” (which is just the current technobabble buzzword) used in building it. I’d bet construction droids were a big part, and I wouldn’t put it past the Empire to use slave labor. Though of course that’s just stupid. Would you fly in a plane made by slave labor? me neither.
Borg ships are entirely hand built by the collective, and they are probably constantly changed.
There was a short story, which I can’t remember the title of right now, where 21-22nd century humans made a large space station/colony by finding a miles-long iron rich asteroid, giving it a spin, and hitting it with lasers. The lasers heated it up, and the spin formed it into a giant hollow balloon, like blowing glass. When it cooled it was ready for habitation, and the spin gave it “gravity” on the inner surface.
Niven’s Belters do this for major bases, such as Farmer’s Asteroid and Confinement Asteroid (“Confinement” being the old-fashioned word for a woman taking to bed to deliver and nurse a baby. I guess the theory is that childbearing and early child rearing needed 1G, even if a Belter could otherwise live 24/7 in their vacuum suit and nothing else.)
For another, slightly more recent take on how such asteroid based systems work, you could read John Ringo’s Troy Rising series, which is set basically in the early days of Earth’s introduction to the Schlock Mercenary Universe.
It spends quite a lot of time talking about how human and alien tech are integrated, and tries to make the science vaguely plausible, but it does use a lot of alien anti-grav, FTL, and AI as granted, although humans take different takes on it that the originators do.
It has, like a lot of Ringo’s books, an unfortunate tendency to lionize strong, “independent” thinkers who can get stuff done if people don’t interfere (read Libertarian / Republican heros) which in the case of one of his novels was dreadfully ironic during Covid, but it’s still a fun read. Just be aware, it ends at the third book and nothing is fully resolved.
But you’ll get to see an inflated asteroid made into a multi-kilometer wide battlestation using an Orion drive for minimal acceleration, so, there’s that.
In David Weber’s Honor Harrington series, there are orbital platforms that are essentially cities. There main functions are to operate as spaceports, naval stations, and for spaceship building, and as military targets, but they also have other industry plus retail establishments to support the resident population. The biggest station, Hephaestus, was 110 kilometers long and had 750,000 residents.
In the books they have fusion energy and very advanced artificial gravity that enables the space construction and infrastructure. Most of the raw materials come from asteroid mining, but they use planetary supplies as well.
And that spoiler is the biggest problem with the Honor Harrington Universe, and really any of these universes where battles are a common event. It’s dead easy to blow the crap out of a station that can’t move, and replacing that shit every time it gets blown up wouldn’t be cheap!
SPOILER ALERT
The series gets into that issue a little bit. I’m extrapolating somewhat, but the basic idea is that it’s most economically effective to have the orbital platforms orbiting the home planet. And although they are military targets, there are treaties and conventions that they’ll only be attacked by short-range weapons, and the platforms will be allowed to evacuate first. There’s a danger that long range weapons, meaning multi-ton missiles travelling at over half the speed of light, could miss the orbital platform and hit the home planet instead. Space forts exist in the series’ universe and are used to guard points in space away from planets, which are mainly wormhole termini. However, those space forts are legitimate missile targets. So instead of having a dispersed fortified orbital infrastructure, they have large undefended ones. Instead, the planetary systems rely on a home fleet for protection. So an attacking space navy is met in space by the defending space navy and a dramatic ship against ship battle ensues.
You need complete control of the fundamental forces, on a level far beyond what we currently have of electromagnetism. Fundamentally, the way we control electromagnetism is by moving charged particles around. An analogous level of control of gravity would be achieved by moving masses around. But where electromagnetism is strong enough that you can achieve the desired effects by moving electrons, gravity is so weak that to get the same kinds of effects, you’d need to move planets.
As for the recent spoilers, keep in mind that cities on the surface of a planet are just as vulnerable as cities in orbit. In either case, you have to hope that military forces and international conventions are sufficient to protect them. And of course, in some cases, both fail (such as during the Haven civil war).
I don’t want this to be a hijack into discussing a specific fictional universe. On the other hand, the Ringworld subthread hasn’t been complained about.
Weber, especially after the first few books, was trying to set up space-fleet against space-fleet engagements. Whoever won the space naval battle won decisively and was in command of the system. If it was the enemy, they could then go around ordering whatever space platforms existed to surrender, evacuate and be destroyed, or even ordering the planet to surrender or face tactical orbital bombardment. So having dispersed undefended platforms wouldn’t be an advantage. It would simply be a case of taking a little longer to blow everything up.
Having defended dispersed space platforms wasn’t ever discussed in the series. It might make sense. Having space infrastructure around the next planet out and its moons and defended by forts, or even fortified, could be a good idea. Or just doing that for military bases and naval shipbuilding. However, there would be two factors working against that idea. The first would be cost. Operating several distant space platforms would be somewhat more expensive than a nearby congregated platform. Throughout the Honor Harrington series, Weber explores how military interests are impacted by economic and budgetary constraints. The second is the navy’s preferences. The navy of the series is focused on ships. Forts are unglamourous. So while there’s a definite argument that the undefended platforms orbiting the home planet are a poor long-term strategic decision - many did get blown up after all - their development as massive constructions is reasonable within that fictional universe.
