Mission of Whirligigity: A History of Whirligig World
The first edition hardback cover of Mission of Gravity.
The 1954 novel Mission of Gravity, is a science fiction story by Hal Clement. It first appeared in Astounding Science Fiction Between April and July in 1953. It describes the misadventures of the alien bug crew of the exploration raft Bree, and how they help the human crew of a starship parked in orbit retrieve the valuable information stored in a space probe on the surface of the rapidly spinning supermassive planet Mesklin.
In 2013, the first planet mod for Kerbal Space Program, Krag's Planet Factory, was released. It added several planets to the system, including the rapidly spinning, extremely dense dwarf planet Inaccessible. Inaccessible was an oblate spheroidal shape, and rotated so rapidly that landing on its equator was impossible--your orbital velocity would be so high you'd escape back off into space. The only way to land was to visit the poles. I, like many others, rushed to play the mod, and I, like many others, went to visit Inaccessible to try to land despite the centrifugal and coriolis forces.
It was in discussions of this object that I believe I first came across descriptions of Mesklin. It would be a couple years later that I found Mesklin again, on the Worldbuilding Page of the Atomic Rockets website. It contained a large chunk of worldbuilding from Hal Clement's essay, Whirligig World. After having read about this strange and incredible planet, I realized I'd love to have one in KSP. A proper one.
I also encountered the idea of a spinning planet through the Star Trek: Voyager episode S6E12 "Blink of an Eye." It's still one of my favorites. Despite featuring a rapidly spinning planet (Kelemane's Planet), the story is more based upon the book Dragon's Egg by Robert Forward. The planet had a tachyon core, and thus due to temporal distortions, everything on the surface was happening at about 90000 times normal speed. One day per second, roughly, and 53 rotation periods in a minute. I had always assumed that the oblate shape of the planet was due to the authors thinking that it should be oblate if it's spinning 53 times a minute, but it occurs to me that perhaps, if you ignore the exact time scale the authors were using, this could explain why Voyager is always in the same part of the sky seen from the planet despite the rapid rotation. If the planet, minus any tachyon effects, actually does spin very rapidly compared to Earth (perhaps once every few hours), it would have that shape, and the altitude that Voyager is stuck at would be in a geostationary orbit. Mumblemumble causes it to match up despite the 100,000x time speed. But I digress.
In late August 2015 I had started work on Alternis Kerbol Rekerjiggered, a reboot using the Kopernicus planetary system modification plugin of one of the earliest planet packs, Alternis Kerbol. It was my first real planet mod, and it still holds an important place in my heart. I got a lot of experience from working with AKR, and eventually I was able to work on other projects, including those with original art assets.
And I was not alone in my desire to see Mesklin in KSP, as it turns out my now-friend NovaSilisko had the same idea. In a comment on the Kerbal Space Program forums in 2015, he described some alterations to the game's default Kerbol System that he'd like to make if he was still working on the game.
New Planet: Mez
- Super-Kerbin with rapid rotation period, somewhat lens-shaped as a result (as later calculations of the properties of good old planet Mesklin suggested)
- Thick atmosphere
- Gravity at poles approaches 10-20g, gravity at equator only ~0.05g
- Scale height of atmosphere varies accordingly, and grows very diffuse and stretched around the equator
- ... which is annoyingly impossible with current systems unless the atmosphere can be rejiggered to work with non-spherical bodies (Dear ferram...)
On the Saturday before Christmas, 2016, I received Heavy Planet: The Classic Mesklin Stories from my cousin at my grandmother's party. Heavy Planet contained Mission of Gravity, Star Light, two short stories, and the essay Whirligig World in full. By that point, Mission of Gravity had been on my wishlist for a while, and I was so happy to receive it that I began reading it on the car ride home. I was immediately pulled into Clement's story, and the whole story was a fantastic read, I can not recommend it enough.
I had by that point become friends with NovaSilisko and we would occasionally discuss the possibility of using the Kopernicus plugin to recreate Mesklin in KSP, or even simulating it in other projects. I would also discuss the problem quite often on the Kopernicus IRC chat, (this was before we had a Discord community). The biggest problem was the atmosphere, you can't make an oblate atmosphere in Kerbal Space Program, so the atmosphere would have to be a sphere surrounding the entire planet or limited to the polar region. The other problem is getting the shape right. As hinted at earlier, the shape of a real rapidly spinning body isn't an oblate spheroid (which is only the case for bodies with uniform density). In reality, the shape will be more lens like, with a sharp edge at the equator. In principle this edge should be more pronounced the further
Ignoring the atmosphere problem and hoping it could one day be solved, on February 26th, 2017, I attempted to create Mesklin in KSP, dubbing the experiment "Whirligig World."
The results were not pretty, but it didn't matter as long as it was functional!
It was not functional.
As far as I was concerned, I'd failed.
I hadn't really worked as hard on it as I should have, though. There were a few bugs with it that are obvious in retrospect and the shape could have been fixed with a different heightmap. All was not lost.
Alas, I do not remember what drove me to create the real initial version of the Whirligig World planet mod. Those chatlogs are lost. What I do know is that some time during October 2017, I decided to try again at Whirligig World. I started from scratch, and instead of trying to replicate Mesklin faithfully, I had a better idea. If you can't make an atmosphere work, why bother with it at all?
I built Mesbin for the first time on October 9th, 2017. It was cloned from my Tylo Space Program mod, which modified Kerbin to be exactly the same as Tylo, but with a space center.
This is the first screenshot of Mesbin, taken at 1:27 PM, October 9th, 2017. Its name is a portmonteau of Mesklin and Kerbin. It replaced Kerbin with an extremely large, massive super-Tylo with an equatorial bulge defined by a new heightmap. The first version of Mesbin's physical characteristics are quite different from their current version, with a different radius, oblateness, polar and equatorial gravities, and rotation period. It was after playing around with this thing, orbiting it a few times, and getting it to work graphically and physically at its most basic, that I first realized this planet could really work as a mod. (In retrospect I am very glad I didn't discover the SOI explosion bug this early, as I probably would have cancelled the project as a result.)
I gave it a new heightmap, new texture, and procedural craters, and the first version of Mesbin was complete! The original Mesbin was harder to get into orbit around (requiring nearly 4500 m/s of delta-v), but its larger radius meant that, since you started at a higher altitude, you'd be able to escape Mesbin from low orbit more easily.
At this point, Mesbin orbited Kerbol where Kerbin used to, and still had both of Kerbin's moons. Whirligig World was still a side project at this point, as I had been focusing on updates to Alternis Kerbol Rekerjiggered.
I soon decided to customize the Mesbin system further. By 9 O'clock at night I had the Derbin system (Derbin = Kerbin + Dirt or Durr or whatever) mocked up, with "Dermun" and "Derminmus," mere clones of Kerbin's moons orbiting it, and with two moons orbiting Mesbin as well. The Mercury-sized "Gramun" and the Kerbin clone "Kerbmun."
At first, Kerbmun was a clone of Kerbin with all the foliage removed, orbiting Mesbin at about 0.1 Lunar Distances. I later changed Kerbmun's terrain to a procedural "Billows" noise, but kept the land control coloration settings.
Kerbmun, in more or less its current form, was built on the first day.
One of the interesting early developments of Whirligig World was the rings of Mesbin. I had initially given Mesbin some rings below the orbit of Statmun, thin little things really. I ended up having to remove them due to graphical issues but... the strangest thing happened the very next day
The very day after I added and then removed rings from Mesbin, the headlines about Haumea, our own solar system's whirligig world, and the result from a stellar occultation that shows that it has a thin little ring system, not too different in appearance from the thin rings of Mesbin. I was so surprised by that stunning coincidence that it really stuck with me the past year+.
Derminmus, which has also not been significantly changed since its first conception, is a browner, dirtier Minmus.
Now one of the interesting things about rapidly rotating planets like Mesklin and Mesbin is that their geostationary orbit altitude is very close to their surface. In Mesklin's case it's perhaps a few hundred kilometers high. And what better way to represent that than by putting a new little moon right in mesbin-stationary orbit. That was the early version of Statmun, made at 9 in the morning on the 10th.
Ah, this view never gets old.
I posted this picture to the KSP Subreddit, the first public unveil of Mesbin and Whirligig World to the world.
Dermun, which we now know as Graymun, is a body I was and still am quite proud of. It's a thing I had been meaning to do for some time by that point: a moon-like body that mimicked the flat maria of the Earth's Moon, with flatter dark regions and cratered light regions.
Gramun, whose terrain would later form the basis of Etrograd and whose orbit would be taken over by Dermun to become Graymun, was built on the night of October 10th.
I was doing some of the first play-testing of the planet and its moons, flying rockets between the planets, and I realized that this system was genuinely a lot of fun to play with. Several large bodies, several moons to fly between, but lots of delta-v between them. That was when I decided to make this an entire solar system mod, not just a little side project.
The weekend before, I had visited the beach with my family and for some reason I asked my mother what a good name for a star would be. She said "Kaywell." And despite that being for a totally different project, I remembered that when naming the star of Whirligig World.
The star was specially designed to allow Mesbin and Derbin to exist. They had to orbit far apart, so as not to disturb each other's moons, but they couldn't go flying off into deep space. I chose to base it off of an F-type star with a higher-than-average radius for its mass. The mass would be higher than the stock sun, but the luminosity would be even higher, and thus the habitable zone and thus Mesbin's orbit could be pushed far enough out that Mesbin's sphere of influence would be nice and big and it would support a distant Derbin.
I also created the first new kaywell-orbiting planet, the Hot Jupiter "Shol" and its eccentric orbiting ball of salt and sand, Yeerbor.
At this point in the worldbuilding process, I was somewhat intentionally thinking unrealistically, because since I had not yet reconciled the Mesbin system with scientific accuracy or stability I figured I might as well not care. This is a viewpoint that I never really liked and was glad to get rid of it. (And when I did, I also had to get rid of the unrealistic old Yeerbor. Yeerbor's name lives on as the eccentric moon of Egad in the current versions).
Reander was named after Meander, the original name for Jool. Its three moons were Yalthe, Mally, and Lito. It orbited at about twice the distance of Mesbin. Reander was secretly a solid planet with only the appearance of clouds for a few versions, and had an oxygen atmosphere, until that feature was quietly removed.
Yalthe was originally the same mass and atmosphere as Laythe, which explains the name. It's meant to represent this system's version of Io.
Yawer, so named because it "yaws" like spacecrafts do quite quickly, was devised as a haumea analogue and it was little more than a reshaped stock Eeloo.
Adjar was named after Egar, the original name for Duna, which would have orbited Meander and would have had larger ice caps. It no longer orbits Reander in the current version of the game, and for a while its orbit was moved to be an eccentric very distant capture orbit of Reander.
Lito was originally a slight variation on Tylo. It would have been HUGE, at the same mass as Kerbin but with a density of only 1 g/cm^3 (due to pure icy composition). As I recall, it was 1,000 km in radius. And all airless, just like Tylo.
By this point I had started really playtesting the game in sandbox mode and career mode, building rockets and trying to fly them around. And I realized that I could make the game just a bit easier on players, by adding fuel stations to low orbit. Not literally--but I did add a scattered diffuse ring of random asteroids to Mesbin orbit, below the orbit of Statmun.
On October 15th, after just 6 days of development, I was preparing to release Whirligig World. I came up with a backstory--that the interstellar colony ship K.S.S. Untitled Space Craft was going to try to colonize Kerbmun, but crashed into Mesbin instead, and I put up a faux-interstellar starship into orbit to photograph a pretend interstellar approach
I released the mod on GitHub and the KSP forums with the first demo of the system. It was pretty barebones. Just Shol, (and Yeerbor,) the Mesbin system, Reander (Yalthe, Mally, Lito, yawer, and Adjar), and an asteroid on a hyperbolic orbit called Hypervelocity Rock (later called Fasteroid).
For a few months I was somewhat at a loss with what exactly to do with this system. It was still pretty empty at that point, and even after having added the asteroids Wolda, Wers, and Vizea, I didn't know what to do. I knew I wanted to have a red star (Called Kaywell B, then later called Primstell, and finally called Gememma)
So I mocked the whole system up as a Space Engine mod, and prototyped a totally new system with a new gas giant, a super-earth based off of the works of Chris Wayan at Planetocopia, I moved Adjar onto its own kaywellian orbit, and I moved Reander outwards. I had also mocked up the red dwarf's system in-game, but since they still had placeholder textures I disabled the config files for each release.
I made the Tyepolbynar System. It was a superjupiter system designed to showcase what happens to the icy moons of planets that migrate inwards. Three cases were shown: Jifgif, the tiny minor ice moon turned comet; Imterril, the earth-mass ice moon turned boiling water world, and Tannor, the icy moon that was white and reflective enough not to melt. (Each of the names of these moons were decided in advance before I knew they would be moons).
I had to change Derbin's satellite system when I was first running tests with Principia. Derbin, despite by best efforts, would still get lost to kaywell orbit, and if I moved Derbin closer I'd also have to move its moons closer. I decided to just get rid of Dermun, and move Derminmus down to a lower orbit. The body that had been Dermun was renamed Graymun, and the body which was named Gramun would be moved to Tyepolbynar as Etrograd, a retrograde-orbiting moon.
I later decided to revamp Mesbin. First came the physical revamp, where its density was increased, resulting in a much smaller planet with a much faster rotation period. Its gravity was set to what is now the standard: 1.28 gee at the equator, 13 at the poles. I would often go on long spiels on the Kopernicus discord about lore and worldbuilding and the science of the system. You can read some of them here.
I also wanted to revamp its physical appearance. Mesbin, being tectonically active would have continents and tectonic rifts and volcanoes, and it would have a polar basin with an atmosphere. 1 atmosphere of pressure, but crushed into the space of just a few kilometers by the immense gravity.
I kept a few of the original terrain features on this Mesbin, like some of the large craters and tectonic rifts that were already there, but the continents were based upon ones generated with the tectonics.js program.
That lasted two versions before I decided to implement that polar atmosphere, and completely redid Mesbin again, using a new tectonics map and using none of the original heightmap features.
A lot has happened since release and I've skipped over a lot of things. I haven't described my tech tree modifications, or how I designed the Gememma system, or how Gememma got to where it is. Perhaps I'll come back and explain that--but I've been writing for nearly two hours now and I'm getting a bit tired.
Whirligig World is, as I type this, getting closer and closer to a 1.0 release. 0.9 will likely be released before the end of March, and it won't be too long after that before 1.0 is ready.
I've recently started to play Whirligig World in a sandbox save (I've played a lot of early career mode off and on since the beginning of the mod's development), and I can't help but feel really proud of what I've built. I never really played it very much before now because I was tired of playing KSP. But Whirligig World breathed new life into KSP for me. It's really a different way of playing the game, and it's so much fun.
As of February 2022, Dermun has been re-added. I hadn't realized just how much moving the original Dermun to become Graymun had made the system worse. When I first played Whirligig World with a basic Mesbin System layout, I had had a lot of fun flying between the moons of the binary planets Mesbin and Derbin. But since removing Dermun, I rarely found the need to travel out to Derminmus, and Derbin was often too hard. Now that Derbin has two satellites, I think we'll find much more reason to visit it. The new Dermun is superficially similar to Graymun, but has its own weird geological history. Graymun is also like a Mun-sized Mercury--quite dense--whereas Dermun is a slightly smaller The Moon.