Mapping space

The Traveller mapping system is what I'm using for AD ASTRA... more or less.  The Traveller mapping system, for all of it's awesomeness, comes across as a little nerdy.  Learning to read the hexadecimal code so you can decrypt their shorthand is too much trouble for most; it's not hard to learn, but it's a bit more challenging to memorize and who wants to flip back and forth between a shorthand like A765845F (SoBF) and have to look at a decoder ring that tells you that it means:

• A: Excellent starport
• 7: 11,200 km diameter (nearly twice Earth's, in case you don't remember Earth's diameter in km off hand.  I didn't.)
• 6: Standard atmosphere
• 5: 50% surface water (Traveller calls it a 50% hydrosphere)
• 8: Population of hundreds of millions (400 M)
• 4: Government type is a representative democracy
• 5: Law level (i.e. weapons) means that personal concealable weapons are illegal
• F: Tech level is Imperial maximum
• SoBF: Allegiance to the Solomani Confederation, and the Boötean Federation

There's a bit more about the world and the world generation system is comprehensive enough that you can start playing almost right away.  It's actually kind of fun to randomly generate star systems, but in reality, you can only do so much of that.  Without some guidance, you get a mish-mash of all kinds of weird things, many of which make little sense, and much of which will not very usable for a space opera "sword-fighting on spaceships" type game.  Showing off your technical jargon when it comes to the RPG hobby is a recipe for a game that isn't very fun.  I've had to learn this lesson (somewhat reluctantly) with regards to linguistics and paleontology, and it's equally true for astronomy and exoplanet details.  Remember that first and foremost, AD ASTRA is an ersatz Star Wars style space opera not an ersatz The Martian and you'll be on the right track.  Even when using Traveller as is to generate star systems, you have to "massage" the results somewhat.

So; here is my version of m20 star system generation.  As with Traveller, I'm going to be using hex maps with 8x10 hex subsectors, grouped into sectors of 4x4 subsectors lined up.  The last post is a sample subsector; imagine that as one of 16 in a square, and that's a sector.  The semi-randomly generated subsector I created (years ago) featured in that example has 40 worlds; exactly 50%.  In my survey of the subsectors of the Spinward Marches sector, probably the most well-developed sector of the Traveller setting, there are between 21 and 32 worlds per subsector, averaging about 27.5, or 35%.

Each hex represents one parsec, and for simplicity's sake, it's presumed that there is (potentially) one solar system per parsec, and that the galaxy can be mapped on a flat two dimensional space.  This is obviously an accommodation for convenience rather than reality, but again—not hard sci-fi, and nobody wants to do complicated calculus to play their space opera game.

There are reasons why you may want to vary the density of stars for a given sector.  The Traveller setting has a number of "rifts" both great and small which present serious obstacles to interstellar travel.  Other areas could be considerably more densely populated by stars.  Barring that, depending on how much you plan on generating may influence the density.  If you're only going to do a subsector or two, a more dense population gives you more to work with.  If you're going to do a whole sector, even doing the fairly standard ⅓ chance that any given hex is occupied will give you about 450 worlds to explore—a full sector has 1,280 hexes in it.  For my sector that I'll be doing, I'm going to give each hex as I go through it a random ⅓ chance of being occupied.  But I'll do that in pencil on a paper draft, because as I said, plenty of massaging may be necessary.

After you've determined Y-Occupied or N-Blank for each hex, you need to fill the occupied hexes with solar systems.  You can pick these as needed, but for fun, I've included percentages so you can randomize them with a d% (and massage the randomized results.)  This is not only kinda fun to do, but it gives you more variety and some potentially interesting systems—but as I said, you do need to make sure that it's not absurd or unusable.  I've not necessarily made these percentages equal to what they would be in actual astronomy (for one thing, we'll get tired of three out of every four stars being a red dwarf.)

Anyway, here's the things you need to map a star system for AD ASTRA.  Rather than there being a complicated short-hand code, you're better off creating a small datasheet for each system.  The data sheet should include the following:

• Location on the map: if you're using discreet subsector maps, you need subsector and hex coordinates.  If you have a bigger map with coordinates that cover an entire sector, you can limit this to just the hex coordinates.
• System type:  Is it a single star, or a multiple star system?  If there is more than one star, then for each star, you will need to determine if it's close (30% chance) or distant (70% chance.)  A close relationship means that they are close enough that the main world orbits both of them together, while a distant relationship means that the main world orbits only one of the stars in the system, and the other star has its own orbital relationship with the main world's sun.
• Single star 01-60%
• Double star 61-90%
• Triple star 91-97%
• More 98-00%
• Star type: the full spectral class is probably more nerdy detail than you need.  You don't need to know that the Sun is G2V, for example, although knowing that it's a normal sized yellow star is nice.  You need to roll twice for this one; once for star color, and once for star size.  Getting the brightness within the color can be fun if you're interested, but isn't necessary (just roll a d10 if you want to do that.)  I've changed the percentages from reality to give us a much greater proportion of Sol-like suns, so as to better present Earth-like worlds.  From hottest to coolest:
• O - Blue star 01-02%
• B - Blue white star 03-10%
• A - White star  11-20%
• F - Yellow white star 21-30%
• G - Yellow star 31-60%
• K - Orange star 61-75%
• M - Red star 76-94%
• Brown dwarfs (L and T) - 95-97%
• Exotic (neutron star, black hole, etc.) 98-00%

Brown dwarfs and exotics clearly don't have a size classification, but for every other type of star, the percentages should be:

• Hypergiants or supergiants (0, Ia, Ib) 01-05%
• Giants and subgiants (II, III, IV) 06-10%
• Main sequence stars ("dwarfs") and subdwarfs (V, VI) 11-95%
• White dwarfs (VII) 96-00%.  NOTE: If you roll this, it overwrites the color you already rolled up.  White dwarfs are, of course, white.  You can massage the outcomes to give you more white dwarfs as companion stars in binary or other multiple systems rather than as primary stars, which is probably a good idea.
• Number of worlds: I'd just roll 3d6, and massage a few down to less than three or more than 18.
• Gas giants Y/N and how many.  If you have fewer than three worlds, the answer defaults to N, unless you manually adjust it to include one.  Gas giants may also be cold gas giants (as in our solar system) or "hot Jupiters" which orbit extremely close to the sun.  Hot Jupiters are problematic, because they will be extremely difficult to skim for unrefined fuel, and they may wreak havoc with solar winds and the stellar magnetosphere, making life difficult on any other planets in the system.  For this reason, the percentage of hot Jupiters has been significantly reduced if rolling up planets, and you may want to massage the results to make more sense.  Or, you can ignore those problems and just have hot Jupiters be an interesting bit of flavor for a solar system (after all, Star Wars brought us parsec as a unit of time rather than distance, and that doesn't make it any less fun.)  Gas giants are important because they serve as a source for free unrefined fuel, and can save the PC's bacon if they need to refuel to get out of town or correct for a misjump.  We'll want to have plenty of them.  Plus, it seems like in reality there ARE a lot of them anyway.
• Gas Giants N - 01-20%
• Gas Giants Y - 21-00%
• If Yes, hot Jupiter percentage is a separate roll, 01-20% is yes, 21-00% is no.
• If Yes, roll a 2d4 for how many.  Make sure that you don't have more gas giants than you do worlds.  If so, it will require manual GM intervention.
• Asteroid belts are also probably somewhat common.  Technically, our solar system as two planetoid belts; and the arbitrary distinction between what is considered an asteroid and what is considered a comet is wearing away every year with new discoveries.  For the most part, asteroids have more nickel iron, silica and other metal and rock, while comets are more likely to have ice of various types (methane, ammonia, water.)  Both are potentially sources of important resources and often draw miners and corporations looking to extract those resources.  Of course, most solar systems, even without an asteroid or Kuiper belt per se would still have asteroids, centaurs, comets and probably a scattered disk and an Oort cloud.
• Planetoid belt N - 01-10%
• Planetoid belt Y - 11-00%
• Single Kuiper belt - 01-20%
• Kuiper and asteroid belt - 21-80%
• Kuiper belt and more than one asteroid belt 81-00%

After you've done all this to generate your solar system data, you need to focus on the main world of the system; the one that's going to be inhabited and habitable.  In general, although interstellar travel is relatively easy thanks to the bulk drive, travel to various worlds within a single system is sometimes more complicated, because you can't use a bulk jump, and regular drives make it prohibitively time consuming, unless you're looking to set up permanently for some reason.  For this reason, all solar systems really only make a minor note of how many worlds, asteroid belts and gas giants there are in a system for reasons of potential resource extraction—the main world is really what you mostly will focus on.  That said, sometimes you can have worlds that are much closer together than they appear in real life (who doesn't love the dramatic image of a planet hovering in the sky taking up a huge chunk of your view, if nothing else?  Plus, terrestrial "moons" of gas giants make for interesting "planets" as main worlds too.  For the main world, you need to also generate the following data:

• Starport type.  Keep in mind that these percentages represent a frontier "scramble for Africa" type sector, so the percentage of higher quality ports is considerably lower.  Another sector in more established space would look very different:
• A - high class, have star ship shipyards where you can commission the building of a ship (if you can afford it) and can do complete overhaul and any repair.  Sells refined fuel. 01-15%
• B - same as A, except without shipyards. That doesn't mean that it may not have star ship dealers, though—but you cannot commission custom jobs, only buy what is on site. 16-30%
• C - routine star port; can repair some damage, but does not have shipyards or dealers, and cannot customize, or overhaul ships.  You may still be able to buy a ship on a "For Sale by Owner" basis at C, D, and maybe even E type star ports.  31-50%
• D - Poor quality port; offers only supplies and technicians for minor repairs, and does not stock refined fuel. 51-65%
• E - Frontier star port.  Offers no services other than a place to park and unrefined fuel. 66-90%
• X - No star port at all.  No services.  No fuel.  Just a bare patch of ground to park your ship.  You can potentially extract hydrogen from water on the surface to fill up your tanks with poor quality unrefined fuel, but otherwise, you're out of luck.  91-00%
• World size.  Rather than roll up diameters in kilometers, I've allowed for a few "types" of world sizes.  Anything more exotic than what's listed here needs to be manually entered.  The GM decides what (if any) effects of world size has on people operating there (penalties or bonuses to STR and DEX sound obvious, but in reality, get tedious dealing with for long periods of time.)  Partly because of that, I've lowered the percentages of non-Earth-sized planets, so they should appear a bit less frequently.
• An artificial, ship-sized "world".  The Death Star notwithstanding, these are going to be quite small as a world.  01-05%
• An asteroid sized world.  It doesn't have to be an actual asteroid, it could be a moon such as one of Mars'.  These are small enough that some of them could have had gravity increased by warlocks in the past, and can therefore potentially support an atmosphere, etc. although this would be a rare thing.  06-10%
• Moon-sized.  Typically will have light gravity and a thin atmosphere if it has one at all. 11-20%
• Mars-sized.  Big enough to have an atmosphere, weather, etc.—although the atmosphere is often thin.  21-30%
• Earth-sized.  31-90%
• Larger than Earth.  Will probably have high gravity.  Natives of heavy worlds such as these tend to be powerfully muscled and robustly built; they are often collectively called hulks.  91-00%
• Atmosphere type.  Given that this is space opera, this is not meant to be nearly as punitive as the Traveller default.  Most worlds allow characters to wander about on the surface without taking extraordinary pains to protect themselves from the elements.  But we don't want to completely eliminate the more exotic types.  This may require re-rolling or massaging more than normal, especially to harmonize your expectations for atmosphere with the world size.  But odd ones that don't seem to match can often inspire an interesting backstory in terms of how it got that way, or what special conditions exist on the planet. 
• None - 01-10%
• Thin - temperatures will tend to be colder, and characters may be out of breath after extreme exertion.  Characters may become fatigued and suffer penalties more rapidly.  11-40%
• Earth-like - 41-85%
• Dangerous - 86-00% can mean a variety of things. Roll an additional percentage if you get this result:
• Effects take hours or even days to manifest, and start with only mild sickness.  Unless you're planning on settling here, or spending quite a bit of time, you only need a filter face-mask, or maybe not even that, to operate safely. 01-20%
• Effects are immediate, but not life-threatening.  Unless operating with a filter or breath mask, you will be immediately sick.  21-45%
• Effects are immediate and may be life-threatening.  Must use a filter, or be at risk of being poisoned and dying.  46-65%
• Atmosphere is completely unbreathable.  A filter won't cut it, because there's not enough oxygen in the atmosphere.  Requires, if not a complete space suit, at least portable airtanks; a scuba-like system.  66-90%
• As above, except atmosphere is also corrosive, and will damage equipment.  Requires complete protection for any except robots, and even equipment will fail over an amount of time determined by the GM.
• Surface water.  Does not necessarily mean that such water is in liquid form; a planet could be made primarily of ice, for instance, or it could have super-thick water vapor clouds miles thick.  Roll d%; probably round to the nearest 10% for simplicity.
• Population.  Colonial worlds often have a much smaller population than one would expect.  Think of the population of North America during the period of American settlement.  Think of the population of Africa during the Scramble for Africa (it was nearly ten times less than it is now.)  So, if some of these population numbers seem small for a science fiction setting, keep that in mind.  Not every world has to be a teeming metropolis.  Population can include both settlers from off-world as well as natives.
• Tiny Outpost: less than 100,000 people on the whole planet.  01-05%
• Small settlements: 100,000-1 million people on the whole planet. 06-15%
• Medium sized population: 1 million-1 billion people on the whole planet. 16-50%
• Large population world: 1 billion to 10 billion people. 51-80%
• Superpopulated world: 10 billion+ 81-00%
• Political affiliation.  This should never be randomly assigned, it should be hand-picked by the GM.
• The Monarchy
• The Revanchist Republic
• The Seraean Empire
• The Cilindan Arm
• The Dhagetan Cartel
• Corporate
• Other "local" confederation (the Altairan Ascendency, etc.
• Independent

I'll put all of this together to create data cards (minus—for now—hex location notation, since I haven't made the map yet) for all of the worlds discussed in the setting overview.  These mostly be assigned rather than randomized details, though—after all, I've already described them in brief.