Engine Technology

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Handwavium can do many interesting and useful things, but perhaps the most useful as far as the Fen are concerned is that it lets us slip the surly bonds of gravity and escape the Well. Applied to mundane engines, and occasionally other things, the 'wave usually produces space craft drives of many different types.

There are two main types of engines in Fenspace. Slower Than Light (STL) drives which are used to tool around inside the Limit, and Faster Than Light (FTL) drives which let you get away from it all.

Faster Than Light

FTL drives all operate on the same basic principle, although it may be expressed in different ways. The thing you need to know about interstellar travel is that it takes forever to do. Given that a lightweight vehicle can make the Earth-Mars run in less than six hours even during opposition, a lot of fen don't realize that making a jump outside the Solar System is a very long haul.

Part of that is the Limit. Once you're over the Limit there's a ceiling on FTL travel speed. Much like nobody's ever managed to get a speed drive to exceed 25% lightspeed inside the Limit, outside the Limit nobody's managed to exceed a top speed of 500c, or five hundred times the speed of light. Now that's nothing to sneeze at, 500c is a hell of a lot faster than any mundane scientist would've ever expected us to travel, but at the same time it's tiny compared to the scale of the galaxy. For example, if you wanted to go to the galactic core, at 500c it'd take you 50 years of nonstop travel to get there.

At least one thing seems to be working in our favor: the mass/speed curve for FTL travel is flat. So instead of larger=slower like in STL travel, everybody can move FTL at the same speed. This is useful to know when planning an interstellar expedition because while a large ship may take longer getting to the Limit, it'll spend the same amount of time in FTL as a smaller ship.

Navigating in interstellar travel is a little tricky. You can't just point your ship at the star and hope for the best. Everything in the galaxy is moving, and that point of light you see doesn't mark where the star is, it marks where the star was however many years ago. Thankfully, most stars don't move that fast, and a half-decent computer armed with shareware science programs can figure out where a particular star's going to be at any point. This is one of those "forewarned is forearmed" situations; get a navigational program built for FTL work off the internet before you start out, otherwise you might end up in the middle of a whole lot of nothing.

Slower Than Light

STL drives, while slower than light, are much faster than anything current state of the rat hardtech will let us do. They typically fall into one of two categories: Acceleration drives and Speed drives.

Acceleration drives do not have a maximum speed that they can achieve[1][2], they do however have a maximum acceleration which limits how fast they can gain speed. All hardtech engines are acceleration drives and as far as we know this will always be so. Acceleration drives are rated by giving their acceleration in Gravities (Gs).

Speed drives have a maximum speed, which is inversely related to the mass of the ship. In layman's terms the larger the ship, the slower it is. Speed drives are generally described by giving their maximum speed in terms of a percentage of c[3].

Based on the ship's class there are some general guidelines about how fast it should be, more or less:

  • Space Port: very slow, typically between 0.01c and 0.02c or worse.
  • Space Vessel: generally from between 0.02c to 0.04c but can be higher, or lower.
  • Space Ship: from around 0.04c to 0.08c.
  • Space Craft: typically between 0.09c and 0.11c.
  • Safety: We have no idea, and we're kind of scared to find out.[4]

Known Drive Types


  1. Assuming you don't run out of fuel or remass
  2. Also, don't forget to turn around when you're halfway there so you can start to brake
  3. Which should give you some idea of how far beyond hardtech we're talking about.
  4. But that's okay, because so is she.