Pictured left is an artist's rendering of Deep Space 1, a space probe launched by NASA in 1998. Its purpose was to test a number of high risk technologies in order to prove more than one new space faring technology, including navigational and propulsion equipment.
When I was setting out to write science fiction for the first time I did a lot of research on propulsion. As I waded deeper and deeper into the history of rocketry, space travel and theoretical deep space travel I kept coming back to the ion engine.
Why? Well, it's not a glamorous type of propulsion, so that wasn't the reason. In fact, Deep Space 1's engine can hold roughly one piece of paper aloft in our gravity, and to get into space it had to be loaded onto a conventional rocket. On the plus side it's incredibly efficient, able to run for years without stopping. The major difference (aside from raw power), between a chemical rocket and an Ion Engine is simple. The Ion Engine is electrical type propulsion. I won't go too deeply into the science of it since the JPL (Jet Propulsion Laboratory), and NASA explain things much better here.
Pushing the Ion Engine into the future:
It's been done before, but I wanted to make sure that it could be done feasibly. Star Wars, Silent Running and many other films refer to Ion Engines as common forms of propulsion in their universes, but that didn't mean I thought I was off the hook for proving that the technology would evolve into a powerhouse of an engine in the distant future. If I were writing a film script, I could get away with it, but not in a book, even one as small as The First Light Chronicles: Freeground.
I decided to look at some of the existing theories that real rocket scientists, electrical engineers and other researchers had as to where they might be able to take the technology. That led me to some interesting notions and futuristic materials that are in play today, on smaller and larger scales. Some of those materials and miniature super-forces included antimatter, new synthetic compounds, and even the creation of short lived miniature black holes.
Astrophysicists can be a fantastic source of information when you ask them a question like; "do you think you could create an engine that uses the force of artificially created miniature black holes to drive a ship across the galaxy?" Surprisingly, the answer was; "yes, possibly, but the energy required to create and contain a black hole would negate the benefits of using it as a means of propulsion. Not to mention you'd be trying to ride something that could have a massive gravitational effect that could bend time, and endanger the ship." Some of the questions I asked sound crazy now, but I was looking to either prove the usefulness of technology derived from what we have today or invent some new kind of super-amazing-futuristic propulsion that would make people stop and think, well, that's super-amazing-and-futuristic! (The black hole drive is not off the table, by the way).
In the end, after doing an obscene amount of reading on super colliders, research into deep space travel, and even more on the proposed future of the ion engine, I made my decision. It was just in time too, considering it was nearly Christmas 2007 and I was going to make the resolution to write every day starting on January 1, 2008.
So, what kind of engines do they have in the Spinward Fringe Universe?
There are a few different kinds, actually, but the most notable ones in the first books are futuristic Ion Engines that are enhanced by highly efficient field technology. They're also assisted by thrusters using High Energy Composites (HEC). The Triton's Ion Engines are assisted by an antimatter injector that provides annihilation type thrust right along side the main thrusters. This costs a great deal of energy and was offline for most of her service with Captain Wheeler.
Smaller ships most often use different explosive propellants to suppliment their thrust, but it becomes expensive for any ship without materialization technology aboard. Xetima, a patented, unduplicatable fuel used on the Clever Dream is a high quality synthetic form of combustible fuel that is used in the ship's high efficiency power plant and propulsion system. The reason why an advanced ship like the Clever Dream would use this kind of fuel is because it allows the vessel to generate more power while using much less space. A rule that has quietly been placed in the Spinward Fringe universe dictates that the more efficient an energy or travel technology is, the more space it takes. On the flip side, technology like Ion Engines take much less wear and tear than the conventional thrusters that provide the extra acceleration for the Clever Dream.
Though Xetima is fictional, it's quite likely that it will exist in some form one day. As we drain the planet dry of petrol, more and more synthetic compounds are being developed. New, patented variations of different ethanol based fuels are created every year. I made the decision that there would be a number of fuels just like that in the universe since there would always be pilots looking for more acceleration.
At the core of the sub-light travel theories is the idea that all the means of transport would be probable, and even antimatter falls into the realm of probability in the far future. Though antimatter is far too expensive, volatile and difficult to contain to be practical now, there's every chance that it will become more practical in the distant future.
So, much like in our own world, the answer to what kind of propulsion is used in the Spinward Fringe universe isn't short or simple. There are a number of different kinds. I even included a couple solid rocket boosters so a certain pilot could get a rush on more than one occasion. An email from a couple readers from MIT patted me on the back for acknowledging that some technologies, though dangerous and out of date, are just too thrilling to leave behind.
I hope you enjoyed this little trip through my brain, leave a comment and tell me how I'm doing!