Saturday, April 30, 2011

The Big Cheat

As Rob points out, interstellar SF is hard to write with without FTL travel.  Not impossible, as L. Sprague de Camp showed with the Viagens Interplanetarias, but hard.  For military SF, or for a coherent game system, close enough to impossible that I'm not going to try it.  And without interstellar SF, both aliens and desirable real estate basicly drop out of the pictures.

Now, I believe in Einstein.  My Physics 110 professors made sure of it; I remember the nearly religious experience of working through the derivations of the Lorentz contractions from the Michelson–Morley experiment,  learning to read a Minkowski diagram, and realizing that the speed of light limit must be true.  I do realize that there are some people who do physics above my pay grade who are prepared to dispute this, but I am not buying any at the moment.  I do believe that FTL is a cheat, but it is one I am willing to make.

The good side of making up a law of nature is that we get to decide what it's effects are.  Not the operating principles -- they matter no more to the reader than Maxwell's equations matter to a four-year-old when she turns on a light.

So, how do we make up our FTL travel rules?  Some good guidance can be found on the Atomic Rockets FLT page.  Haven't seen Atomic Rockets?  There's good stuff there.  Take a few minutes, I'll wait.

So, what constitutes an FTL drive for the purposes of SF?  To my mind, several things:
  • Physical plant - the FTL analog of the motive engine, which may be internal to the traveling ship (as in  Traveller or Star Trek) or external (as in Stargate or Babylon 5).  Is the technology cheap and replicable, or does it require rare lements and rarer fabrication techniques?  The "drive" may even be telepaths folding space with their minds (Dune, Starfleet Alpha Centauri).  After all, any sufficiently advanced magic is indistinguishable from technology.
  • Inputs - what does the drive to consume to make trick work?  Energy sources, like the purified hydrogen in Traveller?  Lots?  Little?  How about environmental inputs, like "sufficiently flat" space (the Traveller 100 diameter limit) or being at a particular point in the system (Mote in God's Eye, Lost Fleet)?  
  • Outputs - How far do I go, how long does it take and where do I come out?  Are there side-effect (detectable "Hyperspace emergencies" from Piper's Terrohuman future, dizzyness and disorentation from Mote in God's Eye)?
  • Procedure - "Travel by normal-space drive to a point 100 diameters from any planetary body, activate drive, wait a week, look out window".
Logistics - game effects, economics, ship construction and operating costs - come from physical plant, inputs and outputs.  Story comes from procedure.  Both have to work.

Atomic Rockets quotes a "making of" piece for "Mote in God's Eye" that appeared in Galaxy back in the 70's

"If the Drive allowed ships to sneak up on planets, materializing without warning out of hyperspace, then there could be no Empire even with the Field. There'd be no Empire because belonging to the empire wouldn't protect you. Instead there might be populations of planet-bound serfs ruled at random by successive hordes of of space pirates. Upward mobility would consist of getting your own ship and turning pirate."

Still, there is a lot of gap between not letting folks pop out on one-another's doorstep and having a working FTL concept.  What do I want from FTL?
  • I want technology base hard SF (Somewhere between 1.5 and 2.5 on this scale).  I want the drive to be a machine that the engineer can kick, and I want it to run on power measured in Watts not brain wave energy.
  • I want it to be sufficiently expensive to not be all that common, but cheap enough that spacecraft without it are fantastically cheaper to build than spacecraft with.
  • I want it to need, or at least only be at its best, with people.  This is the fundamental problem of Rocketpunk, and while I do not want to disown future progress in AI, I do want people deeply involved in the process.
  • I want spacedrive to be for interstellar travel, so no bopping from Earth to Jupiter.
  • I want to be different.   Point-to-point systems inspired directly or otherwise inspired by the Alderson Drive has become the staple of Military SF, so out the airlock with them.  I also don't like most hyperspace-oriented system such as Babylon 5 or the Honor Harrington books.  Too much happens in a space that has different and unusual physical laws.  Shall I read them some of my poetry first?
So, what does that leave.  Well, here (also from Atomic Rockets) is another stardrive classification system:
The EMF classification
Erik Max Francis <>

Type 0; realdrive:  A drive which uses tricks of spacetime geometry
(a la general relativity) to travel faster than light.

Type I; hyperdrive:  The ships enters some different space during the
trip, whether or not time passes for the crew while in this space.

Type II; warpdrive:  A bubble of different space is projected around
the ship so that the ship can travel faster-than-light while still in

Type III; jumpdrive:  The ship travels from one point to another,
possibly in multiple jumps, without occupying the intervening space
and without the use of a different space to assist the travel.

Type X; fakedrive:  Assume that special relativity or general
relativity are incorrect in part or in whole, or just ignore them.
Now you can just accelerate at constant gravity until you go faster
than light.
Type 0 is above my Physics level; in my hands it would look like Type X which is also out. Fundamentally, some sort of warpdrive or jumpdrive looks like "it".  Still, some reasonable limitations have to be wrapped around it.  In effects terms this boils down to two things:
  • There should be some limit to how far you can travel in one go.  If you do not have to stop at star systems from time to time, then your ability to penetrate anywhere with ease becomes to great.  This is not analogous to the 19th Century where the Royal Navy could intrude on any coastline in cared to; Paris or Berlin was not going to burn because of it.  This is more like the late 20th century, where any reasonably competent boomer could annihilate a modestly-sized nation state.  There have to be boundaries to have frontiers, otherwise military operations become short and ultimately boring.
  • There should be some requirement to travel for at least some time in plain sight of your destination to allow the local population to panic defenders to respond.  
I have some thoughts on this, but I need to crunch numbers first.  In my next post, I'll look at some somewhat simpler decisions -- what laws of nature are "in" as opposed to "out" and what assumptions am I making?

1 comment:

  1. I never liked the Traveller 100 planetary diameter jump rule. Jump safety should be related to mass of nearby objets, and lets face it I would think that sometimes planetary mass would be overwritten by stellar mass. As you pointed in another posting out all a problem for the astrogator.