Wednesday, April 3, 2019

A Layman's Guide to Hard Sci-Fi and 200 POSTS!

Listening to the recent Mothership episode of gg no re, I thought it might be useful to provide a helping hand for people who are interested in running a sci-fi game but don't have the time or inclination to do a research deep-dive.

I will be linking to the videos of Isaac Arthur throughout this post. If you want more in-depth exploration of any of the topics here (and many more besides), absolutely listen to him. 

Light is Law

299,792,458 meters per second through vacuum. Round up to 300,000 km/s. Nothing goes faster. (Except, perhaps, monarchy)

Information and radiation travel at light speed. Getting anything made of matter even close to that speed takes a whole lot of energy and is subject to all manner of weird effects like time dilation.

Space is Big

In short:
  • Interstellar travel is not a casual affair. Interplanetary travel isn't either, but interstellar travel is always a big deal.
  • Interstellar travel takes a long goddamn time. Long enough that cryo, digital storage, or life extension will be more or less required.
  • Interplanetary travel can still take days, weeks, months. 
  • Rerouting a ship in transit is not a lightly-taken endeavor.
  • News travels at light speed. Long-distance communication will have lag.  
  • Don't expect big interstellar empires to form. Communication lag and travel time will put hard limits on that quickly. Expect to see a lot of small alliances and confederacies, getting smaller as you go up from habitat to planet to system scale.
  • If you use space habitats a lot a single solar system can contain trillions of people and more places to visit than you can actively comprehend.

It's the Great Filter, Charlie Brown!

The apparent discrepancy between the size and age of the universe and the total lack of detectable alien life (for an interstellar civilization would get HUGE in a relatively short amount of time) is called the Fermi Paradox. The reasons offered to explain why this might be are many, ranging from the plain (the physical conditions for life are rare, intelligent life is rare) to the more elaborate (the aliens are all just really, really good at hiding from us) and among all of these proposals are and a category of them are called Great Filters: factors that prevent life from reaching an interplanetary or interstellar civilization.

There are a whole lot of them. The most plain are just that the physical conditions for life as we know it are rare or that intelligent life is rare. Sensible, but less gameable. Other options include but are not limited to:
  • They died off from nuclear war / catastrophic climate change / plague / etc.
  • They are trapped by high gravity, icy crusts, hyperdense atmospheres, etc.
  • They are intelligent, but lack the ability to make tools. 
  • They aren't intelligent, and their tools don't have proper analogs to normal technology.
  • They're not going to progress past simple tools for a few hundred thousand years.
Skerples  also offers the following: "Planets do not all have 1 earth gravity, a breathable atmosphere, life we can eat or understand, etc." (Check out his full post on the matter), but a solid summary is that the most human aliens are still nothing like us, and the most Earthlike worlds are nothing like Earth. Anything that resembles humans or Earth was probably designed as such (metahumans and space habitats can come into play here.)

Every Gram Counts

Mass needs energy to move it. Fuel and propellant have mass. The more mass you have the more fuel and propellant you need.

Space aboard a ship is at a premium. You've got to balance everything for your specific trip, because you are trying to hit one moving object with another moving object launched from a third moving object all while trying to keep some fragile bags of mostly water and meat from dying. 

It's Not Easy Getting Into Space 

Gravity is fighting you the entire way up and rockets are inefficient. So there are a lot of better ways to get up there. Including but not limited to!
  • Space elevators - A hugeass cable stung up to a space station in geosynchronous orbit. 
  • Skyhooks - A rotating cable that dangles down into the atmosphere and swings a ship up and around to launch them into orbit.
  • Mass drivers - A fucking huge railgun. Great for launching raw materials off of whatever airless rock you're mining them out of, and if it's long enough you can just make a launch loop.

O'Neill Cylinders are the Shit

Imagine a cylinder 20 miles long and 5 miles across. You can make it bigger if you have better materials. Rotate it so that the interior walls have 1 G of gravity, while the caps and central axis will have none. String some together in a chain or cluster, embed them into an asteroid, surround it with all the support systems you might need.

Congratulations, you have just made where most of the population in a space-faring society will live and the easiest way to do a classical space opera. Now you can hop between radically different environments and cultures in a couple hours, in a spaceship that's more like the family RV.

The important thing to remember is that space habitats like these are better for human habitation than planets: you don't need to fight a gravity well to leave, you can tailor the interior environment much more easily, you can churn them out by the dozens or hundreds from single asteroids. 

Stellar Laser Highways are the Shit

Imagine a laser. Now imagine that it is so fucking huge that it can push a spaceship. Build an entire network of them. Now you have a means of accelerating (and slowing) your ships that doesn't require them to spend fuel, thus allowing them to carry more stuff and more people.

It's still slower than light, but it's damn effective. Can be used as communication hubs too.

Spaceships are not Boats

James Cameron's Avatar was not a good movie. But it has one thing going for it: The Venture Star.

Missing the solar sail, alas.

This is a proper spaceship. Just look at this beaut, this sheila, this absolute unit. Mwah! Look at those radiators! See that little bit by the debris shield, with the two rotating arms? That tiny thing there? That's the crew capsule.

This thing has a maximum cargo capacity of 350 tons, a max speed of 0.7 C, and can get you to Alpha Centauri in six and three quarters years flat.

What I'm getting at here is that this is what a hard sci-fi ship will end up looking like: a tiny little submarine attached to a whole hell of a lot of propulsion.

You Will Not Explode and or Immediately Freeze in a Vacuum

You can survive in open space for as long as you can hold your breath (get the air out of your lungs first, lack of pressure will make it expand and that's no good at all). Still likely to get a nasty dose of radiation but having no air is the big danger.

In Knowing the Rules, You May Now Break Them

Arguments over the relative hardness / softness of any given science fiction media are both stupid and dumb. You're making a story or running a game, and that's the most important thing. Do what works for you, do what makes sense - I like aliens, so I tend to be looser on them than I am with, say, FTL communication. Tweak what you want, gloss over what bores you. The opposite is also true - if there's something that really gets you interested, embrace it and see where it can take you.

Bonus: 200 Posts!

I was going to have post 200 be announcing my Patreon, but that's taking its time and I want to keep making things. So this is post 200 (and the first of the post-G+ era).

Holy shit. 200 posts in just a scrape (month and a week) under two years. I can't say much else besides thank you. I certainly wouldn't have kept it up this long without all of you out there reading and commenting and providing feedback.

There's so much yet to do, and I have barely begun.


  1. Seriously, guys and gals - thank you so much.

  2. This is awesome! Good stuff, and congrats on 200!

  3. But seriously though, what is monarchy and why does it travel so fast?

    1. Well you see if a king and his son are one light-year away and the king dies the son will immediately become the new king regardless of his awareness of the fact.

      Also: A joke swiped from Terry Pratchett.

  4. Fun stuff, thanks for sharing/summarizing, and I'll check out some of the links over the weekend!


  5. Good post. Sensible points, well made, and very useful. Also, concise. Congrats on the 200th post, too. Well done.

  6. For anyone wanting more, particularly for those coming from a science fiction background, Atomic Rockets is the go-to resource. Here's the Venture Star:

  7. Technically, when in space without a space suit you're supposed to empty your lungs to prevent the air in your chest from expanding and hurting you. Both the Expanse and 2001 depicted this correctly.

    Honestly, The Expanse, The Martian, and 2001 should be your "hard scifi cinema" references.

  8. Congrats on 200 posts!

    I still haven't read/played mothership but I hear only good things. I've been wanting to do a mech game for forever, and had considered Stars Without Numbers, but I read it recently and... I dunno, at best it felt like an over-written scifi re-flavored OSR, and at worst it felt like it wanted to be D&D 3e. I can see why it was so popular for a while, but it already feels dated, in terms of the game design itself but even in terms of the writing and layout. Definitely has me even more interested in Mothership, although I have no idea if Mothership would work for mechs anyway.

    1. SWN 2nd edition is very much my go-to scifi game still. Mothership is very different in its scope. SWN can handle most things very well, as the rules are plug n play modular, and the system is very well supported with quality additional systems to pick n mix from.

      I'd pick Mothership for "shit goes down in a closed environment" good times and SWN for "you have a ship, now go do whatever in this system" times.

  9. Neatly and efficiently done. This post is deemed worthy of on-board inclusion. It should report for its space shots at 0600.


  10. Oh no! The big 2-0-0!

    2017 was a different world; we've come a ways. Glad that you're still making!

  11. This is a good guide. Hard Scifi is not my cup of tea really. I find it boring in a lot of ways but it can be done well. I'm into super Soft Scifi: silliness, aliens, and the fantastic abound!

  12. Really helpful and interesting post, thank you!

  13. I'm ten days late, but this is really cool shit. Personally, I think planetary-scale sci-fi is kinda lacking--we've got soft sci-fi with easy FTL, and harder sci-fi with cryo-sleep, but some soft sci-fi tropes make a lot more hard sense if the whole setting takes place in a single solar system or even planetary system, like one gas giant.

    1. I agree. More depth, less breadth, still all the fun.