The Ringworld is unstable!

I didn’t want to hijack the GQ thread about ringworlds/Dyson spheres, but it reminded me of some thought on the book that have always bugged me.

In the thread, it was noted that Ringworlds are inherently unstable. They are not in orbit, so they can drift off center very easily. In the novels, Niven posited that even a large solar flare from the laser defense system could knock it noticeably off center within 20 years, and woe! things must be done NOW!

But he ignored several other causes.

I wonder what effect a No 2 GP hull smashing into the ring at a speed high enough to remove the top soil down to the scrith would have?

Or what was the effect of the solar flare that was used to shoot down the Needle?

Or from the impact of a large object that had enough energy to stretch the scrith into a mountain more than 1000 miles high? Ya think that would have had an impact (heh heh) on the stability?

But nope, those were ignored completely. That always bugged me.

As a secondary question, I wonder how many people were killed when the Needle slammed into the ring? Hundreds of thousands? Millions? That didn’t even cause a thought to the author nor the characters.

It’s been awhile since I’ve read a few of the Ringworld novels, but weren’t there some kind of stabilizing thrusters mounted at points all around the outside of the ring to keep it in position? My thinking was they would also compensate for any impacts or other external forces by nudging it back where it belonged.

Maybe the thrusters were added in later books to address the complaints, I can’t recall offhand.

Yes, the later books put Bussard ramjets on the edge walls/mountains for attitude control.

These would have worked OK, if the City Builders hadn’t discovered these ramjets up there and dismounted some of them as ready-built starship engines. So the instability in the Ringworld started to build up and the remaining engines weren’t enough to keep the ring stable. This is why they had to induce a giant solar flare at exactly the right time to hit the part of the ring that had the most preserved jets to give them enough fuel to correct the imbalance.

As for their tiny spaceship impacting the inside, that would be insignificant compared to the mass of the Ringworld. Larger impacts like Fist of God would create much more severe imbalances, but in ordinary operation those could be handled by the ramjets. Too bad so many of those got dismantled.

Sure, it could have smashed through a city like a nuclear bomb, but it didn’t. Most of the Ringworld wasn’t densely inhabited, and even where it was the population was limited because the materials for an industrial revolution weren’t there. No coal, no iron ore, no minerals, no petrochemicals. So everything must be done through wind, water, solar, or biomass energy. And even stuff like stone is in short supply because there’s only a thin layer of material over the Scrith.

I don’t think we’re ever told how long ago Fist of God was. It might have hit while the stabilization system was fully intact, before the City-Builders, in which case they were presumably enough to fix the perturbation (though they might have been working overtime for centuries to do so).

Spoiled, cause The Ringworld Throne is not a good book and therefore, you might not have read it. What condemns Bram, the vampire Protector, in Louis Wu’s eyes, is that he let Fist-Of-God hit because it worked with the assassination ‘game’ Bram and others were playing with the elder protector (Whose name I forget.) So, about a 1000 years ago. I don’t know when it happened in relation to the Fall of The Cities. I think before.

God, that was an awful book. Larry and Jerry did not have many good collaborations as they went on, although I did very much like The California Voodoo Game and Burning Tower

Off the top of our heads, what’s the KE (and momentum, which is probably more important) difference between Lyin’ Bastard smacking the Ring at 770 mi/s or so, and a flare powerful enough to run the Laser Defense?

I think the OP’s complaint was that Niven didn’t think about it when he was writing the first book, not how the stabilization issue was retconned into later books.

Niven fully admits that he didn’t think about the problems with the Ringworld when he wrote the original book, which is why he retconned them into later books.

Although the “attitude jets” address the orbital instability issue, they fail to address numerous other problems. For one, even with the density of scrith with its nuclear-matter-like tensile strength, it would still experience vibrational resonances both in the circumferential and lateral directions. Without some system of active stabilization, the Ringworld should be resonating like a bell, especially with attitude jets firing at irregular intervals. The ecology of Ringworld is also problematic, as addressed in The Ringworld Engineers, but that just scratches the surface. The biggest problem, however, it its existence; its size makes it impossible to conceal and despite its strength it is highly vulnerable to attack. It seems unlikely that Pak would be interested in constructing such a large habitat notwithstanding that the timeline for building and populating it makes little sense in the continuity of Protector. (I refuse to acknowledge Ringworld’s Children and its poor attempt to retcon an explanation for the existence of the Ringworld.)

The Ringworld was a visionary setting in 1970, but it makes little sense upon deeper reflection. Many other of Niven’s literary conceits (stasis fields, psionics) also deviate from the physically plausible despite his reputation as a “hard SF” writer, but he could write some cracking short fiction when on his game.


And now that I look back, Throne was only Larry’s to blame. Guess I took my feelings towards The Gripping Hand and added them to Throne.

As to Ringworld instability, AIUI, didn’t it take MIT graduate (maybe undergrads) students in physics to figure out that it would be? At least he didn’t say that it was all handled with ‘fields.’

Many people could have figured it out–it took MIT students wandering around chanting the title phrase at a WorldCom to make it nerd legend.

To clarify - my OP was not that Niven missed the instability, but that in RE he said the ring became unstable simply from the solar flare used to fire the defense system, while ignoring the larger impact from the Lying Bastard (not the Hot Needle of Inquiry, as I mistakenly identified it. I should have checked.), which I think would have been significantly larger, considering the level of destruction.

And I believe the Fist of God impact would have driven the ring into the star in short order. If it occurred before the engines were removed, maybe they would have stabilized the impact. Either way, all it would have taken is that Niven address why either impact didn’t do the damage.

I thought it would have made a better story if the drift seen in RE was actually due to the LB impact. It would have made it more dramatic if Louis and company had been responsible for nearly destroying the ring. They thought they were just having a jolly adventure, and then they’d find out they nearly killed 15 trillion people (or whatever the pop was). It could have driven the conflict between Teela Protector and Louis, with both of them trying to take responsibility and trying to fix the problem, but disagreeing on methods.

I disagree about the estimation of the number of people killed. RE showed that there were people living everywhere, in every ecological niche, even underwater. The impact blew off the topsoil down to the scrith. (going by memory) The scar had to be a mile wide, and probably hundreds of miles long. Aside from the immediate impact damage, that much dirt blown into the air, and the air blast damage, and likely air superheated to plasma, would have effects well beyond the impact area. The ship probably impacted with a relative speed in the 10s of thousands of miles per hour. The impact would have been…spectacular.

And that scar is never going to heal.

And despite it being his creation, Niven is wrong about Protectors building it. Even if scrith is twing, judging by the similar properties, that doesn’t clinch it. Everything we know about Protectors says they would never have made the island worlds. They wouldn’t have moved several populations of aliens to their new home - they would have exterminated them. Especially Kzin.

To say that Protectors built it means you have to dismiss Protector. It’s not good writing to say “you know all that info I told you? The characters were all lying.”

Well, the Pak couldn’t have built it because they can’t build anything

Quoting Brennan-monster:

To be fair, dismissing Protector is a good idea, anyway. My biggest gripe with the sequels is that they reference the Pak, making it that much harder to excise them from Known Space.

And you can prove the instability using high-school-level math and physics. Gauss’s Law works just as well for gravity as it does for electromagnetism, and that’s all you need. Multivariate calculus is needed to calculate just how bad the instability is, but even that is undergraduate level.

Oh, and apparently in Ringworld’s Children (which I have not read), they turn the entire Ringworld into a hyper-capable vehicle. Which makes no sense at all, because where would you go? To within a very small rounding error, the Ringworld itself is already every destination in the known universe.

They’re not moving the Ring to somewhere - they’re moving the Ring to get the Ring away from the species of Known Space, who have discovered the Ring and are fighting a war over it (entirely too close to the Ring for comfort).

The book also made the myth of hyperspace creatures that eat spaceships into a reality, so the whole book should be tossed.

Can an author screw up his own universe so much that his own books should be removed from canon?


Who would you think actually built the ring? (The Pak is an acceptable answer.)

It seems so…excessive. It must have taken centuries to build, unless there was some never-before-seen-and-not-seen-since way of “growing” it. It would be about the only way, because I can’t see any team with trowels shaping all the mountains and rivers and whatnot. How do you fab shadow squares? The machinery to make them would be bigger than worlds.

It’s all well and good to talk about tearing up planets for raw material, but the details, man! You can’t make the ring out of iron, so there has to be some way to transmute elements on a planetary scale. Where does that energy come from? And if you can do that, why make a ring?

Obviously it was made by humans (or God), otherwise why are the humans the dominant species, and the other Known Space species relegated to islands? Why are they even there at all?

One could write a book exploring just the planet islands. If you can tell how far apart the species diverged (like having sentient female Kzin) you can tell when it was built. But to do that, Niven would actually have to answer questions that I don’t think can be answered.