F is for Faster Than Light

Remember that moment in Star Wars when the Millennium Falcon went into hyperspace?  When Harrison Ford shouted “go strap yourselves in, I’m going to make the jump to light speed,” and the sky lit up as the stars streaked by?  That was my first introduction to faster-than-light (FTL) travel, and I haven’t looked back since.

FTL is a major recurring trope in space opera, and not just because of how cool it is.  If you’re going to have a galactic empire, you need some way to get around that empire–or at least some way to transmit information without too much difficulty.  The distance between star systems is measured not in miles or kilometers, but light years–that is, the distance that a particle of light can travel in one year.  Considering how the nearest star to Earth, Proxima Centauri, is ~4.24 ly away, you can see the need for some sort of magical technology to bridge the distance.

FTL travel comes in four basic flavors:

• Warp Drives — The ship breaks the speed of light as easily as our modern fighter jets break the speed of sound.  Impossible to justify, except through hand-waving.  The most prominent example of this is Star Trek.
• Jump Drives — The ship disappears from its current position and reappears somewhere else.  Also requires hand-waving, but is at least a little easier to justify.  Battlestar Galactica is a good example of this, as is Schlock Mercenary.
• Hyperspace Drives — The ship enters an alternate dimension which allows it to travel faster through our own.  The alternate dimension is called ____space, usually “hyper” but also “quasi,” “x,” etc.  Star Wars is the classic example, though Star Control II took things a step further by having a hyperspace dimension within hyperspace.
• Wormgate Network — The ship (or maybe just the passengers) enters a portal which transports it to a portal somewhere else.  A network of these portals allows travel throughout the galaxy.  Stargate and Babylon 5 use this method.

An alternate way to do it is to make FTL travel impossible, but hold the galactic empire together through FTL communication.  This technology, known as the ansible, features prominently in Ursula K. Le Guin’s books and the Ender’s Game universe.  It has some really interesting implications: for example, even though planets can communicate instantaneously with each other, it takes almost 40 or 50 years to go from one to another, but at near-light speeds, it feels as if only a few months have gone by.  Thus, if you’re going to travel to another world, you have to leave everything behind, including your family and loved ones.  By traveling from world to world, you can skip entire generations, spreading your natural lifespan across thousands of years of normal time.

In writing FTL, one thing you have to be really careful about is to keep in mind ways in which the system can be abused.  For example, if jump drive technology makes it possible to instantaneously transport anything anywhere in the universe, then you can bet that someone is going to send a bomb into the White House (or whatever the equivalent is in your fictional universe).  Thus, the invention of unrestricted jump drive technology will lead to a very short and brutal war.

This actually happened in Schlock Mercenary, and the solution was Terraport Area Denial (TAD) zones, or broad areas of space where a force field prevents anyone from either jumping in or out.  Thus, anyone who wants to visit a planet in a TAD zone has to jump to the edge of the field and travel the rest of the way at sublight speeds.

FTL isn’t always appropriate for a science fiction story.  If the story is supposed to lean more toward hard sf, then it’s probably better to stick with our current understanding of the rules of physics, which state that nothing can travel faster than the speed of light.  Still, with things like quantum entanglement and other recent discoveries, if you know the science well enough, even the speed of light might not be an upper limit.  But for the rest of us mortals, FTL is basically just magic–a sufficiently explained magic, perhaps, but magic nonetheless.

Personally, I’m a fan of the jump drive form of FTL.  That’s the one I use the most in my own books.  The cost is that the further distance you try to jump, the harder it is to pinpoint exactly where you’ll end up.  To overcome this, you can use jump beacons to draw out anyone trying to jump into your particular sector and have them exit jumpspace next to the beacon.  This comes in handy in combat, when the enemy tries to jump a nuke onto your ship.

In the later Gaia Nova books, FTL is facilitated by jump stations spread out in a line across space, with reactors powerful enough to jump ships rapidly to the next point along the line.  In the earlier Star Wanderers books, that technology hasn’t been invented yet, so there’s still an Outworld frontier.

It gets kind of complicated, but it’s lots and lots of fun to world build.  For example, how does a particular change in the FTL tech alter the galactic balance of power?  When settlers try to colonize a new system, what do they establish first–starlanes, jump beacons, Lagrange outposts, or what? As with any magic, changing one thing affects everything else, which also affects everything else, which … yeah, you get the picture.