Sci-Fi Planet Generator

Space...

When creating a literal universe to play a role-playing-game in, one can find the work of creating the multitude of star systems and planets exhausting. This series of random tables is meant to speed up that process with every tabletop gamer's favorite tool: dice. Using a series of simple roll-tables you'll be able to come up with a virtually infinite number of unique solar systems for your players to venture through, even on the fly as they sail violently off your rails. I've only played 5th edition Dungeons & Dragons, but these pages are system-agnostic, so you'll find that they work for any tabletop RPG.

Star Stuff

First you must choose a number of solar systems for your players to have access to. You can't very well have planets without having stars now can you? Now, this part can be done manually, and frankly, should be. A nice simple number like 10 or 15 should hold your players over for a very long time. You can always add more as your players venture outside of the area. To give some scientific flavor to your fake corner of the cosmos, use a d8 and the table below to determine the sort of stars at center of these systems. For Binary Systems, roll two more dice, re-rolling 1s and 8s.

Determining Star Type

d8	Star Type
1	Binary System
2	Red Giant
3	White Dwarf
4	Red Dwarf
5	Medium Yellow
6	Medium Orange
7	Blue Giant
8	Supergiant

Counting the Planets

And now that you have the requisite amount of giant fusion balls and loose dust, let's make some planets. First the easy part: how many planets? Well again, this can be manual, but to relieve the pressure, I recommend a simple d10 roll, where you treat the "0" as an actual 0. Some stars might be quite lonely, but there can still be value in the asteroid fields, or adventure on a space station.

Filling The Void

I wish I could fill the void in my soul with a dice roll... Anywho, most star systems will have comets, or one or more systems of asteroids, even if they don't have planets. If a system has 3 or more planets roll a d4 twice, and add the features of the table below to the system to give it more character. For systems with 2 or less planets, only one extra feature should suffice.

Star System Features

d4	Feature
1	Asteroid Belt
2	Artificial Debris Field(s)
3	Frequent Comets
4	Space Station

23 Different Flavors

Finally, the meat of this guide. The many, many, different kinds of planets. After you've figured out how many you have around a particular ball of hot gas, you must then determine what sort of environment is on those planets. Roll 2d12, and consult the table below. In the third column you'll find an example of the type of planet described from some popular sci-fi series, or a real one.

Determining Planet Type

2d12	Planet Type	Example
2	Mega City	Coruscant (Star Wars)
3	Garden World	Eden Prime (Mass Effect)
4	Overgrown Jungle	Kashyyyk (Star Wars)
5	Ocean World	Kamino (Star Wars)
6	Desert	Tatooine, Jakku (Star Wars)
7	Frozen Wasteland	Hoth (Star Wars)
8	Alien Jungle	Pandora (Avatar)
9	Hot/Poison Atmosphere	Venus
10	Radioactive Ruins	Tuchanka (Mass Effect)
11	Lifeless Rock	Mercury, Mars
12	Gas Giant	Jupiter, Neptune
13	Lava Surface	Mustafar (Star Wars)
14	Chemical Atmosphere	Titan
15	Ice, Hiding Ocean	Enceladus, Europa
16	Tidally Locked Rock	Ryloth (Star Wars Legends)
17	Dangerous Swamp	Dagobah (Star Wars)
18	Violent Storms	Hagalaz (Mass Effect)
19	Crystal Planet	Crait (Star Wars)
20	Savannah	Dantooine (SW: KOTOR)
21	Ocean With Islands	Ahch-To (Star Wars)
22	Abandoned Mega City	Feros (Mass Effect)
23	Goldmine Planet	55 Cancri e
24	Profitable Gas Giant	Bespin (Star Wars)

But What Do The Numbers Mean?

What, 2-word descriptors ain't good enough for you? Fine, fine, here's a more detailed summary of each of type of planet. The majority of the finer points are still up to you as the one in charge of the universe, but I'll provide a short paragraph describing the basic conditions on each of the 23 kinds of planets.

Mega City

Coruscant, Ilium, Taris

A planet that is entirely covered by a city will always have a population in the tens or hundreds of billions (at least). If this planet is in a space where travel is open and peaceful, then it is likely that the inhabitants of these worlds will be of various races. Planets like this need large, powerful governments, lest they fall into chaos. Markets on such worlds will have just about anything your adventurers need, but simple things like food must be imported and will be expensive. Mega cities make great capitals for large interplanetary empires. For added variety, consider rolling on the "crime level" table below.

Mega City Crime Levels

d4	Crime Level
1-2	Peaceful
3	Moderate
4	Chaotic

Garden World

Earth, Eden Prime, Naboo

"Garden World" is a term used in science fiction to describe a hypothetical planet that has the conditions needed to create its own life. In real life, Earth is the only garden world we know of. When making a garden world for your game's setting, envision a young, idyllic, pre-humanity Earth. The sun shines brightly on a field of brightly-colored grass, and antelope-like aliens prance peacefully surrounded by butterflies. Ugh, gross. Odds are that such perfect places have been settled in some capacity by intelligent life, so consider rolling on the table below to see how much. In high amounts, they may begin to disturb the natural beauty.

Garden World Settlers

d6	Amount of Settlers
1	None
2	>1000
3	1000-10,000
4	10,000-100,000
5	100,000-1,000,000
6	1,000,000- 1,000,000,000

Overgrown Jungle

The Forest Moon of Endor, Kashyyyk

Similar to garden worlds, overgrown jungles are teeming with life. The primary difference is simply that they are more dangerous, and less beautiful. The climate may also not be a perfect Californian 70 °F, but a sweaty 90 °F. Some planets like this will have intelligent natives such as the Ewoks or Wookies of Star Wars. A simple coin flip should suffice to determine the presense of such creatures, if you must leave it up to chance.

Ocean World

Kamino, Mon Cala

Scientists often like to say that if we look for a new home among the stars, we should look for water. Ocean Worlds are overkill, for us humans. We don't have gills, so we'd have a tough time settling down on a planet that is fully covered in liquid water. That said, Earth life began deep underwater, so it's highly likely that such a planet would be teeming with alien life. Modern sea life on Earth is also a common source of medicinal materials, so applying this same concept to your sci-fi setting can be a fun galaxy-building tidbit. For more randomness, I've created a small table of extra features below.

Ocean World Extra Features

d4	Feature
1	Floating Station(s)
2	Underwater Dome City
3	Huge Sea Monsters
4	Poisoned Water

Desert

Tatooine, Jakku, Arrakis

I mean, you HAVE seen A New Hope, right? If not just stop reading this thing and go watch the single most-important science fiction film ever, please. That'll teach you everything you need to know about desert planets. A desert planet is either sparsely inhabited, like Tatooine or Jakku, or empty. That's about it. Oh, also, giant sand worms are a fun addition (read: Dune, 1965). If you happen to be playing the 5th edition of Dungeons & Dragons, then consider using the stats for the Purple Worm found in the Monster Manual for those. Below is a table with a few simple permutations of desert planets.

Desert Planet Options

d4	Features
1	Uninhabited
2	Small Settlement(s)
3	Uninhabited w/ Sand Worms
4	Settlements w/ Sand Worms

Frozen Wasteland

Hoth, Noveria

After you've watched A New Hope, I'm going to assume you watched The Empire Strikes Back, right? If not, please do yourself a huge favor. There's not too much to be said about frozen planets like Hoth, or Mass Effect's Noveria. There's two basic variables: Native life and outside settlers. I'd suggest just flipping a coin for each of those. No matter what both of those will be in small numbers.

Alien Jungle

Pandora, Felucia, Morrowind

Now getting to the weird stuff: Alien jungles. There's really no need for a roll table on this one because such environments are by their very nature, weird. Any arrangement of giant mushrooms, killer plant tentacles, and colorful reptilian predators can make these planets both fun and dangerous to explore. If you happen to be playing Dungeons & Dragons, then consider using the creatures and descriptions of the Feywild for such worlds.

Hot / Poison Atmosphere

Venus

Getting real for a moment, consider our neighbor Venus. About the same size, similar gravity, not too much closer to the sun... and covered in an atmosphere made almost entirely of acid, with an average surface temperature of 462 °C. Not a fun place, but great background for your planetary adventures. It could be an interesting challenge for your party to have to retrieve something from the surface of such a world.

Radioactive Ruins

Tuchanka, Earth in the Fallout series

Imagine if the cold war had actually kicked off. Hundreds, if not thousands, of nuclear detonations in the space of hours. Needless to say, humanity would not have fared very well. In the Mass Effect series this happened to a hardy species called the Krogan, and it left their planet forever scarred. Plant life became unheard of for generations, and whole sections of the planet were rendered uninhabitable. Such worlds might actually be quite common. The only real variable to consider with these planets is whether or not anything still lives there, which you might decide with a coin flip. If your game prefers magic to science then consider re-flavoring the radiation as lingering dark magic.

Lifeless Rock

Mercury, Mars, Pluto, The Moon

I shouldn't have to explain this one too much. Just a big 'ol rock orbiting a star with little-to-no atmosphere and no water. There might be valuable minerals or chemicals on such a planet however, so mining operations might be common, depending on the technology levels of your universe. For a fun plot twist, maybe have one of these planets have a ton of life living underground, sheltered from the elements.

Gas Giant

Jupiter, Saturn, Neptune, Uranus, Yavin

Another simple one. These huge planets are quite common, cosmically speaking. How the players interact with these planets, if it all, is up to the technology level of your game, but odds are the crushing pressure and powerful gravity will make even getting near them a dangerous prospect. Flip a coin for pretty rings.

Lava Surface

Mustafar

Now what good is a game without the token lava-based level? Not too much to say here. The whole surface of these planets will be either black stone or running lava. Generally the lava comes in slow, constant flows, rather than rare, powerful eruptions. The heat will generally be survivable in short bursts, but an atmosphere is likely to be smokey with sulfur. Or you could go the Star Wars route and have it be perfectly safe to breathe next to an active lava river. For Dungeons & Dragons, consult readings on the Elemental Plane of Fire for inspiration.

Chemical Atmosphere

Titan

Consulting our own solar system again, we come to Titan, the largest moon of Saturn. The weird thing about Titan is that it is so cold that methane there behaves like water does for us. It exists in all three states of matter, and makes up lakes as well as clouds and rain. Such a planet is completely hostile to life as we know it, but imagining life that bases itself on a liquid other than water is a fun thought. Whatever RPG gaming system you use, remember that if you put life on one of these planets that you should use the most absurd and alien creatures your game offers.

Ice, Hiding Ocean

Enceladus, Europa

And if you look to your left, you'll see two more objects from our solar system. Both Saturn's moon Enceladus and Jupiter's moon Europa are just big balls of ice at a glance, but popular theory states that they might contain a layer of liquid water deep below the icy surface, heated either by being bent by their gas giant's gravity, or radioactive minerals further down. Could such an ocean contain life? Well in your crazy sci-fi setting, why not? Most RPG systems offer plenty of aquatic creatures to discover in the depths. Maybe even a whole civilitazion down there. Flip a coin for intellegent life.

Tidally Locked Rock

Ryloth

For a planet to experience "tidal lock" its orbital period must be exactly as long as its day. In other words, one side of the planet always faces its sun. This means that one half of the planet will be boiling hot, while the other will be completely frozen. Such a planet might have a thin ring (about 50-100 miles wide) of constant twilight that is actually quite pleasant, with plains or even jungles. You can roll on the following table to determine the condition of a locked planet's habitable zone.

Locked Planet Habitable Zone Type

d4	Feature
1	Oceans and Lakes
2	Alien Jungle
3	Cities
4	Garden World

Dangerous Swamp

Dagobah

A dark cousin of the Garden World archetype, the swamp planet is most famously seen in The Empire Strikes Back as the home of Yoda. There is generally little solid ground that isn't heavily saturated mud, and lakes and rivers are everywhere. Fog affects visibility frequently, and reptilian creatures make traveling there very dangerous. For Dungeons & Dragons, swamp planets make great homes for bullywugs, kuo-toa, and yuan-ti, among others.

Violent Storms

Hagalaz

In Mass Effect 2, there was a planet with a day equal to 98 Earth days. This meant that one side would get very hot, and the other would be cold, much like a tidally locked planet. However, thanks to the slow rotation the hot and cold zones were constantly mixing at sunset/sunrise, meaning that instead of having a ring of pleasant, calm twilight, this planet had a ring of constant killer storms. Animal life is pretty much impossible on such a planet, but it may still have a breathable atmosphere and hardy plant species. Much like lifeless rock planets there may be valuable materials to be found here, and the storms make great hiding places for strong enough ships.

Crystal Planet

Crait

Instead of a lifeless rock, imagine a lifeless crystal. A whole planet made mostly of quartz, malachite, or opal, instead of granite or sandstone. Such planets would be hostile to most conceivable forms of plant life, but The Last Jedi's Crait is home to some animals. A planet like this might be a good source of wealth for some creative miners, but typically the stones aren't especially valuable. Instead, such planets make great tourist spots thanks to the excellent views and stunning caves.

Savannah

Dantooine

Another type of near-garden world, savannah planets are home to a great deal of life. Trees are sparse, and grasses dominate the landscape. The climate could be described as "a dry heat" year-round. On Earth, the African savannah is home to lions, elephants, rhinos and other desert-adjacent creatures. Such planets would actually be decent places to settle down, so I reccomend using the same population table as the one given for garden worlds, but re-roll 6s since these planets are a step down. Make sure water is present, but not abundant.

Ocean With Islands

Ach-To

Imagine an ocean world that is 99% water instead of 100%, and this is the sort of planet you get. The islands here are usually the result of volcanic eruptions, or tectonic pressure that pushes up rock spires. The best example of this in recent sci-fi is Luke's planet from The Force Awakens and The Last Jedi, Ach-To. The island are typically of a tall, rocky makeup, with only simple plant life. Animal life on such planets would be interesting. Birds would do well by flying from island to island and hunting fish, but non-flying land life might be completely unique to each island, or at least each group (See: the Galapagos Islands). Settlements from off-worlders would be unlikely, just because of the lack of space.

Abandoned Mega City

Feros

Here's an interesting question for you: what happens when a planet like Coruscant is abandoned? The answer: a huge amount of money and resources is left behind. But, in order for such a large population to be killed or forced out, some great catastrophe must have occured. Roll on the table below to determine exactly what brand of apocalypse ended life on your planet. What happened will determine the state your players find it in, and how dangerous it is for them to loot it.

Cause of Abandonment

d6	Apocalypse Type
1	Zombie Plague
2	War
3	War (interplanetary)
4	Sun Got Hotter
5	Sun Got Colder
6	Meteor Impact

Goldmine Planet

55 Cancri e

Goldmine planets are typically not too different from lifeless rocks. The key difference is that they are made almost entirely out of some sort of valuable material. Consider the implications of such materials on your universe's economy, and consider choosing this material yourself. If you still want to leave it up to chance, I have presented a few options below.

Valuable Materials

d4	Material
1	Diamond
2	Gold
3	Special Metal (ex: mithril)
4	Fuel

Profitable Gas Giant

Bespin

The last, and least common type of planet will appear to be a standard gas giant at a glance, but is actually more like a goldmine planet. Every space-based setting needs a fuel source, and a common one in science fiction is helium-3, a gas. Perhaps the fuel in your universe has a more exotic sounding name, but nonetheless a gas giant with a thick layer of it will be highly sought after. The only variable to consider is whether the gas is mined by small ships, or large installations like The Empire Strikes Back's Cloud City. Flip a coin if you'd like to leave it to chance.

Moons, Moons, Moons!

We've got stars, we've got planets, let's get even smaller now. Every good science fiction universe has moons almost as well fleshed out as its planets. Moons follow different rules depending on whether they're orbiting a rocky planet or a huge gas giant.

Rocky Planet Moons

First of all, we have to figure out how many moons orbit each of your planets. For small planets I recommend 1d4 - 1 moons. This leaves the possibility of having no moons, which both saves you work as the DM, and is scientifically plausible. The second thing to consider is what planet type each moon's environment is most like. Consult the table below, and remember that moons of this size have about 10-20% of Earth's gravity. Also remeber that goldmine moons are smaller than planets, and therefore contain less total value.

Small Planet Moon Type

d8	Moon Type
1-4	Lifeless Rock
5	Lava Surface
6	Ice, Hiding Ocean
7	Crystal Planet
8	Goldmine Planet

Gas Giant Moons

Gas giants have more moons on average, and with more variation. A good realistic number is 2d10, but to keep things reasonable as DM, perhaps just do 2d6 or 2d4. Another note to remember is that these moons are the same size as normal planets, and will act just like planets in every way.

Gas Giant Moon Type

d20	Moon Type
1-4	Lifeless Rock
5	Lava Surface
6	Ice, Hiding Ocean
7	Crystal Planet

Gas Giant Moon Type (cont.)

d20	Moon Type
8	Goldmine Planet
9	Overgrown Jungle
10	Alien Jungle
11	Frozen Wasteland
12	Desert
13	Ocean World
14	Hot/Poison Atmosphere
15	Radioactive Ruins
16	Chemical Atmosphere
17	Dangerous Swamp
18	Violent Storms
19	Ocean With Islands
20	Mega City

Enter Your Name

And now for everyone's favorite part of RPGs: naming things! If we're being frank I think that this works way better when you just make them up yourself. That said, I totally get that writer's block happens, so I've created a system of tables to help you name stars, planets, and moons.

You could choose to just name each star system, and refer to the planets with names like Tarmoz I, Tarmoz II and Tarmoz III, or you could roll up names for each planet individually. Personally I prefer the second system in most cases, but the first is good for star systems that are newly discovered or sparsely inhabited. Moons could be individually named, or just referred to with names like “the third moon of Simik V”, if they're not particualarly interesting.

The tables below present two sets of 100 single-syllable sounds. First, roll a d4 or d6 to determine how many syllables your planet or star's name has, then roll d100s for each, stringing together your results. You can go back and forth between the tables randomly for even more variety. If you happen to roll up a planet with a name too similar to something that exists in established sci-fi, consider using syllables from the other table to get rid of the ripoff names.

Let's run a quick example. Say you rolled a 3 for the number of syllables. Roll 3 d100s. If you rolled a 24, 65, and 39, your planet or would be named "Gorrenla", once you get rid of the capital letters. If you use the second table instead, then this planet would be named "Gerrukleph". You could also then mix and match the two tables, getting something like "Gorrukla" or "Gerrenleph". You could even reverse the order of the syllables for a completely different name like "Larengor". Either way, there's no way you'll ever have to struggle to name a celestial body ever again.

Syllables Table I

d100	Syllable
000	Aa
01	Ac
02	Ach
03	Ad
04	Ae
05	Ag
06	Ar
07	Arn
08	Ap
09	At
10	Az
11	Ba
12	Bo
13	Bun
14	Cer
15	Cot
16	Cyt
17	Do
18	Dut
19	El
20	Er
21	Eum
22	Fo
23	Gha
24	Gor
25	Hon
26	Him
27	Ik
28	In
29	Ip
30	Ir
31	Iz
32	Jak
33	Jot
34	Jun
35	Kah
36	Ker
37	Kun
38	Kul
39	La
40	Le

Syllables Table I (cont.)

d100	Syllable
41	Lor
42	Maa
43	Mar
44	Min
45	Moth
46	Mok
47	Must
48	Na
49	Nok
50	Niif
51	Nus
52	Oo
53	Ok
54	Or
55	Oz
56	Par
57	Pat
58	Pol
59	Puz
60	Qun
61	Quo
62	Qur
63	Raa
64	Rann
65	Ren
66	Ryg
67	Sal
68	Sim
69	Sin
70	Sol
71	Sor
72	Sur
73	Sym
74	Tat
75	Tol
76	Tu
77	Tun
78	Tyr
79	Ub
80	Uk
81	Un

Syllables Table I (cont.)

d100	Syllable
82	Ur
83	Vaa
84	Val
85	Vex
86	Ver
87	Vu
88	Wa
89	Wan
90	Wii
91	Wik
92	Wun
93	Xo
94	Xur
95	Yar
96	Yul
97	Za
98	Zil
99	Zun

Syllables Table II

d100	Syllable
000	Ab
01	Aff
02	Ak
03	Al
04	Ao
05	Arg
06	Ash
07	Ath
08	Att
09	Ay
10	Bann
11	Bit
12	Borr
13	Bu
14	Cir
15	Cop
16	Cu
17	Da
18	Dit
19	Eeth

Syllables Table II (cont.)

d100	Syllable
20	Eph
21	Ez
22	Fa
23	Fin
24	Ger
25	Gi
26	Gol
27	Haa
28	Heg
29	Ip
30	Ium
31	Ix
32	Jaal
33	Jok
34	Jut
35	Kap
36	Kel
37	Laath
38	Lar
39	Leph
40	Ler
41	Luo
42	Mas
43	Mak
44	Mith
45	Mor
46	Moz
47	Nar
48	Nak
49	No
50	Nul
51	Nuk
52	Oa
53	Ob
54	Og
55	Ov
56	Paal
57	Pak
58	Pod
59	Put

Syllables Table II (cont.)

d100	Syllable
60	Qua
61	Qul
62	Rag
63	Rath
64	Reg
65	Ruk
66	Saap
67	Sar
68	Sigg
69	Sis
70	Soth
71	Sud
72	Sul
73	Sym
74	Tar
75	Tog
76	Ty
77	Tyg
78	Uar
79	Uff
80	Uth
81	Um
82	Uz
83	Vas
84	Vax
85	Ven
86	Verg
87	Vyn
88	Wak
89	Waz
90	Wid
91	Wiv
92	Wyn
93	Xar
94	Xul
95	Yag
96	Yur
97	Ze
98	Zul
99	Zuth

Putting the Pieces Together

Well you've done it. you've written down the locations of stars, planets, and moons, and determined what happens on all of them (and even named them). But what happens between them, and around them? Remember to look at the types of planets you have near each other and how they interact. Got a mega city all alone in a system with 4 lifeless rocks? Then make sure the peoples of the mega city are mining those lifeless rocks. Got an ocean world in the same system as a desert planet? Then consider that the inhabitants of the desert planet will probably scoop up huge amounts of water from the ocean world and have it purified for consumption. The way planets interact with each other is what really makes your universe seem like a real lived-in space, and not just a random sampler platter of space-stuff.

Consider fleshing out your universe's interstellar trade and travel routes as well. Star Wars has a complex system of hyperspace lanes that are great to see for inspiration. Make sure the lines follow some logical system based on either trade or war. Another way to do this is to copy Mass Effect and say that interstellar travel relies on getting assistance from huge structures that act as accelerants, and so trade routes are built around them. Traveling on these routes would be a lot like traveling between towns in a medieval RPG, and is a great time for random encounters with space pirates or enemy military scouts.

Another thing to look at after you've rolled all the planets in a sector is how they've interacted with each other in the past. What have they fought over? Are they still holding grudges? Is there a war going on right now? What exactly happened to that abandoned mega city, or that radioactive wasteland? You don't need to write novels on this stuff, but a basic timeline of events to put your whole universe into perspective is a great idea, for any world builder. You also don't have to make all this information easy to get for your players. Finding out what happened to a place that's been ravaged by disaster is always a fun mystery to solve. Be sure to make regions currently experiencing peacetime interesting as well. Maybe there's a problem with wildlife or a resource shortage for the players to tackle, instead of interplanetary war.

If you find yourself stuck, remember to think on smaller terms. Imagine each planet as a country or region, and you'll find the work of fleshing out a galaxy much less intimidating. If you've ever built a world for a fantasy setting like Dungeons & Dragons, then don't approach this too much differently.

I do hope you've found these pages entertaining and helpful, and I wish you good luck in your game.