Monday, February 17, 2014

FTL PROPULSION

As a space opera setting, Frontier needs to have the tools available for its wayward characters to traverse the stars reasonably freely. After all, one of the themes is exploring strange new worlds, which isn’t going to mean much if we can’t get our characters to those strange new worlds in question! However, here we hit a snag, depending on how ‘hard’ we want the science in our setting to be. For those who don’t know, ‘hardness’ in a science fiction setting refers to how scientifically plausible it is. Settings which stick to slight iterations on current technology and use rocket propulsion for space travel are considered to be ‘harder’ than settings which hand wave away gross details of amazing teleportation and feats of incredible engineering. A TVTropes entry (link) goes into more detail than I will here. For those who went and read that, though ( sorry for the time sink! I’m sure you’ll escape TVTropes eventually! ), the aim for Frontier is to try for a three, be happy to settle for a two, and avoid a one on the hardness scale that TVTropes is using.

As a side-note, I actually am not pursuing hardness for the sake of some level of scientific purity. As a budding engineer type, I appreciate science and its applications, and I do keep up on new discoveries in many fields. I am also not anti-science, by any stretch of the imagination, and I recognize it as a useful tool to help humanity interpret new data and make progress in our search for knowledge. However, Frontier is a setting for telling stories, and I will bend the laws of physics to get to my goals for the setting. So why bother with hardness? I feel that it helps build an internally self-consistent setting to set rules, and to start by trying to derive them from already existing rules. So going forward, I will try to break as few rules as possible on the path to telling my stories.
But wait! The title of this week’s post in propulsion. What does that have to do science fiction ‘hardness’? Well, like I said to start with, my space opera setting needs a way to deliver its characters to strange, new worlds. And so we run into problems with the hardness scale, namely thus:

We don’t know of a way to go faster than light.
Worse, given our current understanding of the universe, traveling faster than light requires us to travel backwards in time in a way that breaks causality. I don’t want to travel back in time, and I definitely don’t want to mess with causality.

However, the ability to travel faster than light is kind of important when traversing distances best described using units such as ‘light-years’, or the distance light covers in a year. In these units, it’s about 4 light years to the nearest star to earth ( besides our very own sun ), Proxima Centauri. At the speed of light, the maximum speed limit of the universe, that means it will take four years for our intrepid space crew to get there from Earth. That’s a helluva road trip. The amount of time it’d take to visit other planets that might have life? Forget it. So when planning travel in Frontier, one of the things I had to keep in mind was how to get around that pesky speed of light limit, and since I’m breaking the known laws of physics, taking the extra step to make sure my method maintains internal consistency with the rest of the setting and with itself.

The other problem of propulsion is one perhaps a bit more important for storytelling purposes, and that is not just why it works ( the question science fiction hardness deals with ) but also how it works, the details of what it does. Various other science fiction properties deal with the matter in different ways. Hyperdrive and warp drives abound, with varying levels of explanation, speed, and effectiveness. Less frequent but still common methods include various wormhole or portal gate methods, transporters, and the like. One of the tropes of the Frontier setting that I would like to maintain is that of using space ships, vehicles, to travel between the stars, allowing crews to spend some time in between star systems looking at the depths of space. Given this, some ideas for propulsion seem to naturally fall out.
The teleportation ideas are right out. Even if a ship is required, they bypass the middle step of any given voyage, which can be a rich place for accidents in space to happen. As well as being a good excuse to listen to a ship’s crew talk to each other some. Or even for a loner to see how long it’ll take before the voices in his head truly catch up to him. The other reason teleportation is out is because it makes certain kinds of military maneuvers that I may want to work with very difficult to write for. Part of combat in space is getting the combatants into the same space long enough to shoot at each other. This is hard to do if one side or the other can simply blink out of existence at the drop of a hat. While there are ways around this, they feel like patches on top of a system that I didn’t want to begin with, and so I shall give interstellar teleportation a miss. ( As a side-note, my setting gives teleportation a miss altogether, but that’s a topic to be covered at some other time )

So, what are we left with? I wrestled with some other systems, of course, and wind up with a multiple method approach. In many sci-fi stories, it is not uncommon for a writer to pick -a- way of FTL and stick with it. I’ve picked two, and left room open for more should my imagine come up with them. Unlike teleportation, I am not going to delve deeply into the methods I didn’t choose. Instead, I am going to talk deeply about the two methods I did use, their in-universe basis, and their out-of-universe justifications.

First, a brief overview of what the systems do. One method of FTL will be a gate system, similar to that used in EVE Online and early Schlock Mercenary. Giant hoops in space that were built at great expense ( or, in some cases, left behind by now-dead cultures ) will generate wormholes that connect one gate to another. By sending a ship in through one side of the gate, it will spend some short time in transit, and come out the other side at the destination gate. The gates will be one-way, but they can be cycled off and on to re-establish the link in the other direction or to a different wormhole gate. Out of universe, this system provides me with some very nice characteristics. One, they provide obvious military chokepoints. Two, they’re meant to be very, very fast for those times when I need the characters to get somewhere in a hurry. Also, when coupled with the next FTL system, these wormhole gates can be seen in-universe as a sign that society has really settled into the system where they’ve been made. Gate means traffic means civilization.

Of course, this leads nicely into talking about the other system. The gate system has a problem built into it. In order to have a gate to a system, you have to have travelled to that system in the first place. Which means that in order to use FTL, you have to already have FTL to get the gate in place in the first place. The second FTL system solves this particular problem. This second system does not need gates of any kind. Any ship can use it from anywhere to anywhere. By design, it will be slower than the wormhole gates. By how much, I haven’t determined yet. It also requires the expenditure of energy from the ship, which means fuel. However, as a benefit, it does not rely solely on the point to point characteristics of the gates.

There are other factors to consider when creating an FTL system from scratch. For example, how to get around the pesky relativity problem, and how to avoid making dirt-cheap planet crackers. For the former problem, I’ve simply defined a universal static special frame of reference called the ‘intrinsic field’ that all FTL technologies rely on. If that sentence made no sense to you, don’t worry about it. I basically waved my hands and made up a plot device to ‘get around’ some of the consequences of relativity. For the latter, this same system is used. Basically, a ship at FTL is not able to really interact with real space. It can be detected from real space, and it can see real space, again through the intrinsic field. But you can’t take advantage of the F=mv^2 law to skid your faster than light spaceship into a planet at ridiculous energies. If that was allowed, then every starship would essentially be a planet-ending missile as well. In addition, the manipulation of the intrinsic field necessary to make the jump to FTL speeds simply won’t work well in the presence of strong gravity fields. I haven’t yet decided if this means within a star’s gravity well or close to a planet’s gravity well, but the end goal is the same. Prevent easy planet crackers. Of course, all of this is likely to change as I flesh it out more.

I was planning on covering sublight propulsion this week as well, but I ran out of time. So that’ll be next blog.

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