Brian York's Life

Tachyons and Dark Energy: How to build a Science Fiction Universe

Written on June 19, 2008

Introduction

This document was originally posted to the sfconsim-l mailing list. It’s not the original game design article that I was planning to post, but it should be interesting and, what’s more, fairly close to in line with physics as we know it. This version is somewhat modified, mostly by my including explanations for parts of the article that didn’t make as much sense the first time through as I thought. I’ll very likely eventually be formatting this into LaTeX and posting it in the Files section of my web site. There are a number of reference web sites which would be very useful to anyone reading this. An explanation of the problems with FTL, and their solutions, is found here. A more general introduction is provided by Nyrath the nearly wise on his Atomic Rockets web site here.

As at least some of you know, I’m currently involved in graduate school in the hopes of finding someone willing to pay me to do Astronomy for a living. Since I’ve just started my Masters’ degree, I still have an assortment of coursework to get through, and one of my courses is a course on observational cosmology. Today, we were discussing the cosmic microwave background (CMB), and it was mentioned that one of the big effects the CMB shows (after you mask out the galaxy and an assortment of point sources), is a dipole effect. Specifically, half the field (roughly) is red-shifted, and half is blue-shifted. This is caused by the motion of our local group with respect to the CMB (I should note that the changes in the CMB caused by our motion are ~100 times more intense than the intrinsic changes caused by the way the universe was during recombination, so the dipole is definitely something you have to deal with before getting data out of CMB probes). The result of this is that the CMB can be treated, in a way, as a universal rest frame. There are, of course, caveats to that, but it still started me thinking.

One of the biggest problems with faster-than-light travel is, of course, causality. The standard problem is that, of Causality, Relativity, and FTL travel, you can pick any two. Unfortunately, Relativity has a lot of experimental support, and so does Causality (not to mention that getting rid of it makes things kind of nasty, in that time travel can mess up science fiction settings (especially hard science fiction settings) quite nicely). One of the best ways around it (that doesn’t cause other problems) is to assume that FTL travel happens with respect to some preferred reference frame. Now, this invalidates Relativity, since one of the axioms of Relativity is that all reference frames are equivalent, but it does so in a way that has yet to be tested. As of this moment, no one has ever looked at how faster-than-light travel goes with reference speed, so it’s possible that Relativity, like Newtonian mechanics, is only mostly right, but wrong in areas we haven’t yet tested.

Now, if you introduce a special reference frame, it’s nice to have something to tie it to so that it doesn’t appear to just have been made up. Since the CMB is pretty much universal, and seems to have its own reference frame, it makes a pretty good candidate for that special frame. Now, the rest of this is assuming that FTL travel is possible, tachyons exist, and the CMB reference frame acts as a special reference frame for FTL travel. So, to see where I’m going with this, read on. I won’t guarantee that it doesn’t contradict physics (as experimentally verified) at all, but it shouldn’t contradict it much.

1. Three Types of Particles

One of the tenets of special relativity is that matter and energy are equivalent (E=mc2). Quantum mechanics, among other things, treats EM radiation as particles (photons) with wavelike behaviour. Tachyons, if they exist, would be faster-than-light particles, and the other particles (those in the standard model) move slower-than-light. Table 1, below, shows a quick comparison between these particle types.

Tardyons Bosons Tachyons
Speed v < c v = c v > c
Type Fermion Boson Fermion
Function Matter Force Carrier FTL Matter
Mass Real Zero Imaginary
Low-energy Background Vacuum Energy CMB Tachyon Energy
Cosmological Role ΩM ΩE ΩΛ
Table 1: Different Varieties of Particles

Cosmological role here refers to the role that each particle plays in standard cosmological models. ΩΛ is, in this case, the dark energy (or “cosmological constant”) term introduced because the universe doesn’t behave as a standard Einstein-deSitter universe, but rather as a universe where space-time itself has inherent energy, something that could actually be replicated by tachyons (see this article for details). The “Low-Energy Background” part is, of course, a bit of a reach (pretty much everything else has already been theorized by those who have postulated the existence of tachyons). Still, I figure it holds together pretty well. The bosons form a privileged group in that they move at the speed of light. I posit that each tardyon (quarks, leptons) has its equivalent tachyon, and that you can “flip” between tardyons and tachyons by inverting the sign of log(vc-1) with respect to the CMB reference frame.

2. Tachyons

Tachyons, of course, have somewhat paradoxical properties. As they gain energy, they slow down, eventually approaching the speed of light. Conversely, as they lose energy they speed up. In addition to a tachyon background, equivalent to vacuum energy or the CMB, I also posit that there are tachyons even in a vacuum, just as there are particles there. The net effect of this is that a tachyon “particle beam” will eventually decay as parts of it collide with the “tachyon interstellar medium” and lose energy (gaining speed). This means that, unlike a normal particle beam, a tachyon particle beam would have lower-energy particles arriving ahead of the main beam, and giving some warning that you’re about to be hit with something.

This has implications for space combat (obviously), since it means that you can dodge incoming fire (if you detect it early enough). It also has implications for communications, detection, and pretty much everything else (including actual FTL travel). I’ll be covering all of this in the next few subsections.

2.1. FTL Communications

In order to communicate at faster-than-light speeds, it’s necessary to get a message to travel at those speeds. Now, since the only FTL I have here is tachyons, I’m going to have to use them. Unfortunately, they’re more like particles than like EM radiation, so FTL communications is going to resemble firing a particle beam at the destination. Now, of course, very little work has been done with respect to communicating in this way, so everything I offer here is pretty much pure hand-waving.

I’m assuming that communications range (and bandwidth) depend on the power you put into the beam, and that (for reasons mentioned above), beam power degrades as the beam travels farther. Now this isn’t nearly as important for communications as for weapons (I’m assuming), but over long ranges it will make some difference. In particular, there’s a trade-off between range (using a high-powered beam) and speed (a low-energy beam goes faster). This has the interesting effect of, at least potentially, making long-distance communications faster than local communications (assuming, that is, that the long-range detector is more sensitive). It also means that having a ship/station with dedicated communications arrays (much like the comm ships in the Renegade Legion universe) can be really useful — with a comm ship, you can signal your home base (and get a reply) much faster than you could do without a dedicated set of sensors looking for low-powered (but fast) tachyon particle beams.

I won’t even touch on how you get a particle beam to convey information. I’m going to leave it as there’s probably a way, but I don’t know what it is. Alternately, you could use “message torpedoes” or “news travels by ship” if you’d prefer.

2.2. FTL Travel

The easiest way to go FTL would be to transform your ship into its Tachyon equivalent (by inverting log(v/c) through some handwavy means). Once again, you have a question of how fast you’re going. Since higher speeds correspond to lower energies, but higher speeds also correspond to more chance of getting lost in the background, there’s probably the same trade-off here that you have with communications. You now have a role for scout ships — ships designed to go faster, by being able to hold together at lower energies.

Manoeuvring in the Tachyon universe might also be strange. The crew might perceive things as being normal, and working in the same way, or they might not. Would accelerating actually increase or decrease your “real-world” speed? Could you manoeuvre at all? These are useful questions to ask, and any particular answer gives you a different universe. As always, the trick is to pick your assumptions and stay with them.

2.3. FTL Detection

Well, a tachyon ship would probably emit tachyons, which could be detected. Tachyon-based equipment might also be detectable in this way. The tachyon background might give you a way of detecting ships (now this is getting into an area which might mean violating quantum mechanics, as applied to tachyons, but the hand-wave might be worthwhile). You might also just say that a ship moving slower than light simply can’t be detected through tachyons (which is reasonable, since after all if the ship is moving STL you’ll be able to detect it ahead of time just by looking at the light it emits).

Of course, since tachyons are particles, this would be more like detecting cosmic rays (or particle accelerator experiments) than detecting light. If you assume that whatever drive ships use in tachyon space emits particles, then these could probably be detected. I’m not sure what the detectors would look like (cloud chambers? magnetic traps?), but there’s probably a way, and if it’s needed, it will be found.

Detection might occur simply because pieces of the ship will spontaneously decay into lower-energy (and hence faster) tachyons, as whatever field is holding the ship together fails for that particle. In that case, there might be maximum tachyon space endurances for both ships and crew (again, like Renegade Legion’s “shimmer heat”), because longer stays increase the risk of enough particles being lost to cause serious damage. Ships might require maintenance after a certain duration, and crews might require enough time for their bodies to “replenish” lost particles through natural processes. This would also have another effect, in that more massive ships (and possibly ships moving faster) would be easier to detect. Again, this has a parallel in the Renegade Legion universe.

Tachyon weapons will also be detectable, as I mentioned in the introduction to this section. That removes one of the biggest features of most space combat games — lasers work unlike almost any other weapons, because by the time you know a laser is on its way, it’s already hit you, and there’s no possible way, even in theory, to get advance warning. In the case of tachyons, however, you can get warning. And that seems like a useful thing, at least for some genres. After all, you can’t dodge what you can’t see, but you can see a tachyon pulse coming before it hits. All of which, of course, brings us to

2.4. Tachyon Weaponry

In the FTL travel subsection, I’ve assumed that you can flip things from tardyons to tachyons and back. Now, assume that you can do the same thing with a particle beam. Further assume that you can flip it back when it gets to its target (or just use tachyon torpedoes, and forget about beam weapons entirely. Alternately, have combat take place in tachyon space, and you don’t have to worry). You now have weaponry which can hunt down and kill ships, but which has the same trade-off as both communications and travel — the more energetic it is, the slower it goes.

One effect of this principle is that the most powerful weapons will give the most warning time. This could easily lead to a big-ships-dominate style of game, because the bigger weapons are better. It could also lead to a fighters-dominate style, because they can dodge big weapons while still carrying useful weapons. Finally, the game could track the change from battleships to fighters, as engineers figure out how to mount the big guns on small frames.

Of course, for more of an age-of-sail feel, you could install Tachyon-tardyon converters on shells (you can even rate them by mass if you want), and use those as your primary weapons. If your battles happen in normal space, that then becomes extremely interesting. You have to accelerate your shells fast enough to do damage without moving them fast enough that their velocity will decline while in tachyon space.

Another interesting effect is that a ship may actually be able to outrun incoming weaponry. It might be possible for a ship to be “lower-energy” than a damaging weapon, in which case it would move faster. If you want to avoid this, the obvious response is that a ship at low energies is vulnerable to low-energy (and thus faster) weapons. Of course, that doesn’t mean that a brave (or foolish) captain couldn’t try to gain the advantage by pushing the limits of his/her engines….

2.5. Symmetry

Now, so far, things sound pretty symmetrical. Tachyons are exact equivalents to tardyons, just on the other side of the v=c divide. However, things actually aren’t quite symmetrical. Just as matter and antimatter are almost perfectly symmetrical, but not quite (as you can see — we live in a matter-dominated universe), so are Tachyons and Tardyons. I assume that large-scale structure (as in galaxies, stars, planets, and even big molecules) doesn’t exist naturally with respect to tachyons. There are a lot of tachyons (ΩM~0.3, whereas ΩΛ~0.7), but they don’t form structure.

This means that it’s difficult to turn a ship (or a message) into tachyons. Really difficult. Or, more accurately, it’s difficult to make the ship stay a ship, instead of dispersing as a cloud of T-protons, T-neutrons, etc. This both gives a real reason for things falling apart at low energies (otherwise I’m saying the equivalent of “you’ll fall apart if your velocity goes to zero”), and keeps me from having to deal with tachyon galaxies, planets, life, etc.

3. Implications

This is the hardest part to write, because there are so many ways to play this universe. As a result, I’m going to mention a few points, and give them a brief discussion, and then move on offer a worked example to close things out.

3.1. Tachyons are particles

This is a really important one, and probably something I’ve forgotten at several points in the above description. Tachyons are not like light, radio, etc. They’re like matter. There’s a few asymmetries, but mostly if you exchanged us with tachyons there wouldn’t be any difference. This has far-reaching implications, some of which have already been mentioned, and some of which I probably haven’t thought of yet.

Incidentally, as a bit of background flavour I posit that the current CPT symmetry is imperfect, but CPTN symmetry works. Or, at least, that’s the assumption, so people are looking for CPT violations in the same way that they’re searching for CP violations now. That is, if you flipped the charge of every particle, made time run backwards, changed the parity (reflected everything in a mirror), and exchanged all tachyons with tardyons (and vice versa) everything would be the same, but any of these symmetries, individually, doesn’t hold. That’s why I can do a “no large-scale structure” — because of a minor asymmetry, the same reason that a minor asymmetry in C (charge) leads to a matter-dominated universe.

3.2. There are now two different places to fight

Battles in tachyon space are likely to be very different from battles in normal space. What they’ll look like exactly isn’t known, but there will be differences. For one thing, speed-of-light weapons will be almost like terrain — since they move more slowly than anything else, the principal thing is to avoid running into them. Note, of course, that you still can’t see light until you hit it, so lasers and such are almost like minefields. Given the way that low-energy tachyon matter tends to come apart into fundamental particles, tachyon space is also likely to be a more dangerous place to fight. Whether or not this is a good thing depends on what you want your universe to look like.

Of course, you can always forbid all tachyon-space combat by making it simply not work (choose your assumptions), and that will give the universe its own flavour as well. That’s really the neat part of all this — you can do anything you want as long as you pick the right assumptions.

4. Worked Example

This section is intended mainly to flesh out all the ideas above. This is a worked out example of the engineering and society that might go along with the physics above, but it’s far from the only such example possible. In picking my assumptions, I find that my main inspirations are FASA’s Renegade Legion universe, ancient Greece (because they tend to be my general inspiration, and are often overlooked in favour of the Romans), the age of sail and the earlier age of galley warfare (because they offer a good parallel in many ways, and are much less overdone than the Roman empire), and finally a number of universes which I have developed myself but which aren’t yet worthy of publication (even in this form).

There are two reasons that the Renegade Legion universe is, in many ways, so similar to the example below. The first is that the physical and technological background of the RL universe is, in many ways, extremely similar to the physics above. That the system above, which was actually designed to be at least minimally compatible with physics as we know it today should be so similar to a game system developed by FASA back when it would not have been compatible with known physics is certainly an interesting coincidence, but I don’t think there’s anything deeper to it. When I was looking at a universe to design, I was at least as interested in game (and story) potential as I was in plausible physics (and, where there was a conflict, I decided in favour of game potential), so I suppose it’s not that strange that a universe designed entirely for game potential would be similar in many ways.

The second reason that Renegade Legion has such a presence here is that I’ve always admired the work that went into its background, even though I remain vastly disappointed with the quality of the actual games produced. I liked the background, and the thought that went into it (especially gems like the Prefect “Operational Briefing” manual), but I found the games to be very disappointing. Not only did the space games use a pseudo-vector movement that was more complicated (and less realistic) than actual vector movement, they also placed extremely artificial limits on their ship classes, seemingly only for the purpose of having limits. Finally, the games weren’t very much fun to play, at least for me, which is the real problem, especially since the background was so interesting.

That said, there are definite differences between what I’m doing and the Renegade Legion background. For one thing, I’m not introducing faster-than-light communications (which is a considerable change). I’m also emphasizing different weapons and tactics, and using different assumptions for combat and manoeuvre (one of the biggest changes is that a lower speed in normal space turns into a higher speed in tachyon space, which will definitely change things considerably). My background is also much less epic. Instead of having a completely inhabited galaxy with tens of billions of soldiers, I have two dozen or so inhabitable worlds with a total population less than ten billion. Instead of an “evil” pseudo-Roman (albeit consciously so) society facing off against a “good” pseudo-British society, I have a number of different groups with an overall feel of classical Greece (small, independent, and squabbling) and a few larger powers, none of which (I hope) are either good or evil. Finally, I think I bring a different feel to the universe, which provides a perfect example of the idea that physics and setting are entirely different things, and that a vast number of very different universes could be built from the physics I have above.

4.1. Travel

Travel in normal space will be figured out once ΔV requirements have been determined. Ships will presumably carry some sort of reactor to provide them with power (I’m assuming that tachyon technology allows cleaner reactors to be built, specifically that neutral particles can be inverted before they have a chance to irradiate things much, and that the coulomb barrier can (possibly) be overcome with the help of inversion technology. In any case, warships are likely to require more drive energy than merchant ships.

Once in tachyon space, it is effectively impossible to manoeuvre at all. Your exact velocity and heading when entering tachyon space determine your velocity and heading while in tachyon space. This means that ships will generally have to correct their course several times during an interstellar journey, because their pointing is unlikely to be exact. This has the effect of making navigation loosely similar to the age of sail, with the need to get fairly frequent reference points, and change your course by them. This also makes the tachyon drive tactically useful, since ships can manoeuvre around using it even while quite close to one another.

The power required to keep a ship intact is proportional to the ship’s mass, to the cube of the ship’s major axis, and proportional to the square of its velocity, so P=Kr3v2. This applies, however, only in the domain where the ship’s speed is significantly less than that of the tachyon background. The background is important at many energy levels, but begins to dominate at log(vc-1) > 4 (which translates to 10,000 c, or a trip from Earth to Alpha Centauri in a bit less than 4 hours). This is the practical limit to velocity, as above it field power increases exponentially with velocity in addition to the above dependence. If less power is available for the field, it will still offer some protection. Given the power requirement above (for an optimal field), the particle decay rate is multiplied by the square of the absolute value of the actual field strength subtracted from the optimal field strength, and normalized to the optimal field strength. That is, D=K(|Fo-Fa|/Fo)2. So supplying additional power to the field as as bad as supplying too little.

Ships moving faster-than-light may be detected through tachyon decay, which is directly proportional to mass of the ship. If the ship’s field is not optimal, the decay rate is increased as in the equation above. Rather than a standard decay process (such as a half life), this decay process is linear with mass, something which has yet to be explained. The rate is such that, with an optimally tuned protection field, a person may safely spend no more than fifteen consecutive days inside tachyon space, and must spend at least one day in normal space for each three days in tachyon space in order to avoid progressive degradation. It is possible, but unlikely, for serious damage to occur before the fifteen day threshold. Most equipment is designed with this degradation in mind, and is deliberately made modular to compensate for the degradation. In general, a particular module is good for 180 days of tachyon space, which converts to roughly three years of normal operations. Modules are normally replaced every year and maintained in duplicate (or, for warships, in triplicate), with replacement staggered so that any particular component is replaced reasonably often. Of course tramp merchants may make due with only one of any given module, and that one may be “a little bit over its rated age, but it should still be fine for another hundred light-years”.

When a ship is inverted into tachyon space, its speed is inverted in a logarithmic sense. This means that log(vc-1)Tachyon=-log(vc-1)Tardyon. So an original speed of 0.1 c (30,000 km/s) would turn into 10 c, and 0.0001 c (30 km/s) would turn into 10,000 c. As the initial velocity approaches zero, the tachyon velocity approaches infinity, making an entrance at 29 km/s significantly more hazardous than an entry at 30 km/s. In addition, the Earth (and the local group of galaxies) are moving at ~300 km/s with respect to the cosmic microwave background, which translates into a velocity of 1000 c, so it would be (by default) considerably easier to move in the direction of the CMB rather than against it. In order to deal with this rather inconvenient physical fact, I introduce one arbitrary technological (and physical) shortcut — the velocity at which you enter tachyon space is handled relative to the CMB, but the direction is decided based on the direction your inverter is pointing in (generally aligned with the direction of the ship, for obvious reasons). This also allows merchant ships to use tachyon space safely without having to have massive ΔV reserves, which may just mean the difference between economic survival and starvation.

Given the above, it seems that the only main requirement for ships will be enough ΔV to match velocities between different solar systems. This will require a ΔV of somewhere around 40-60 km/s. Since I’m postulating that inversion will assist with fusion, a fusion drive ought to have enough ΔV, while still allowing merchant ships to carry a reasonable cargo. Since 3He-D fusion will give a ΔV of 100 km/s even with a mass ratio of 1.01, making a merchant ship 25% fuel and drive seems a reasonable balance, while a warship would have roughly 50% of its mass devoted to fuel and drive, giving it both greater ΔV and higher thrust.

4.2. Communications

The only way to communicate faster-than-light is to send a ship. Specialized message ships (which may also be used as scout ships) are spherical in shape (to minimize the volume effect on field power), small (to minimize the mass effect) and have high fuel fractions (so that most decays will, statistically, affect the fuel reserves rather than important components). This not only allows such ships to attain higher velocities, it also allows them have a higher ΔV. Since high thrust is usually obtained at the expense of high efficiency, having a higher fuel fraction also lets the mail ship increase its velocity up to safe speeds (velocities high enough to allow it to enter tachyon space without going too fast, and disintegrating) more quickly, since enough %Delta;V will be available even at high thrust.

4.3. Weaponry

Because ships are unable to manoeuvre in tachyon space, battles take place exclusively in normal space. The primary weapon used is the tachyon cannon, which fires a shell (usually a field generator, capacitor, inverter, and (occasionally) a fragmentation warhead) at a high enough speed so that the kinetic energy of the impact will cause damage to the target. These shells are necessarily almost completely unguided, but since they spend most of their time travelling at approximately 4,000 c this doesn’t much matter (4,000 c corresponds to a normal space velocity of 75 km/s, giving the impactor 625 Ricks of impact energy). Different ships are able to fire shells at different speeds, trading off flight speed for damage. Shells range as high as 60 kg in mass, of which 5/6 act as an impactor while 1/6 is consumed in the tachyon transitions and intermediate decay. Of course, if the shell spends longer in tachyon space (or isn’t charged as well), it will lose more mass more quickly.

The range of a tachyon cannon is 600 million km (the included field generator lasts for a maximum of 0.5 seconds), but the accurate range is far shorter (~150,000 km). Nelson’s advice that no captain will go wrong by laying his ship alongside his enemy is also well founded here. This is a short enough range that light speed lag is not particularly relevant, especially since the tachyon drive is the usual combat drive. The range is also short enough that, while a shot can in theory be detected before it hits, in practice this is close to impossible, since the travel time is only 0.000125 seconds. While the internal computer on a shell is more than capable of measuring this time, it is shorter than the effective reaction (or response) time of essentially any ship.

One obvious question is why no nuclear weapons are included. The primary reason for this is the effect of tachyon disintegration — a nuclear weapon is complex and delicate, and they don’t tend to survive the transition through tachyon space except on extremely large and expensive shells, which tend to be more difficult to employ, less accurate, and generally not cost effective. The same applies to lasers and particle beams, especially in faster-than-light battlefields. In general, even fragmentation warheads aren’t worth the effort, since too much can go wrong with them. While the inverter can also fail, the shell can’t work at all without it, so that risk is considered cost effective.

With respect to ground combat, the same weapons are used, although they are less effective. Trying to invert out of tachyon space inside an atmosphere is difficult, and tends to cause considerable problems, including much greater disintegration. As such, the shells used for planetary bombardment are not fitted with inverters, but rely instead simply on their kinetic energy. Inverter-equipped shells could be used to bombard planets from a safe distance, but they would have to be more massive in order to avoid burning up in the planetary atmosphere, which would require specialized bombardment ships. The net result of this is that spacecraft, except for specialized ground-support craft, are not especially good at attacking ground targets.

4.4. Ship Types

Since there are now great advantages to small ships, beyond a smaller cross section, this setting favours larger ships for pretty much any combat duty. The volume dependence on field strength also encourages large ships, although scout ships and couriers may be made smaller for reasons of cost. Larger ships will also offer more stable firing platforms, and will be able to supply more power to their tachyon cannon, an important consideration (I have the shells powered by capacitors rather than batteries, so they can’t be carried charged for long periods of time). A larger ship will thus be able to fire more rounds, heavier rounds, and more accurately than a smaller ship. Thus, while a small ship might be able to mount short-ranged (due to faster degradation) “carronades”, the big cannon are found almost exclusively on larger ships. While this is not quite as extreme as the age of sail, in which frigates essentially couldn’t harm ships of the line, it does tend to favour large ships. This, again, tends towards the age of sail, although it’s also a fairly common extrapolation in science fiction settings that apply rigourous consistency.

Due to weaponry being based around kinetics and, in particular, solid-shot kinetics with relatively slow closing velocities, ships will actually be able to survive a fair pounding before being taken out of action. One-shot one-kill weapons do not exist in this setting (as intended, although there may be unintended consequences that I haven’t explored), allowing combat to be an exciting affair, and suggesting that armour (another advantage of large ships) is an excellent investment, even if it will (also) be prey to tachyon disintegration.

A few sample ships are included below, to give an idea of what I see as being the likely ship types in this universe. One ship of the line, one patrol ship, one courier, and one merchant ship, to give a broad idea of the capabilities and limitations of this setting. Note that the “Rating” is a general assessment of combat ability — numbered ratings are for warships, and the higher the better, while lesser ships are assumed not to be able to seriously threaten warships. The rating refers to the ship’s throw rate of shot — a rating of 1 means that the ship can, in theory, throw 1-500kg of cannonfire forward, while a rating of 2 means 501-1000kg, etc.

The ships here are presented with the statistics that would be considered relevant by people in the setting. They were not designed by any sort of program or spreadsheet, they just reflect my idea of reasonable capabilities for the setting. The flavour text is just that, and serves more as an idea of the environment than as a serious indication of the history and deployment of a particular class.

4.4.1. The Archon’s Own Warship Polydeukes

The Polydeukes is the first of a new hull design, intended to serve the Hellenikan League for many years to come. Advanced automation systems allow the Polydeukes to function on a considerably smaller crew than most ships of the line, although the effectiveness of the automation has been questioned when it comes to damage control. While the Polydeukes does reduce shiphandling and technical crew considerably (the earlier Kastor class required 30 shiphandling and 50 technical crew), the League has never had difficulties in supplying maintenance or technical crew, and the requirements for staff and prediction have actually increased with the presence of a full Strategos on most missions.

Able to accurately fire all of its forward battery guns at once, the Polydeukes makes the most of its seventh generation reactor and drive. A maximum thrust of one gravity, however, is not sufficient for the Polydeukes to match the speed of the earlier Kleisthenes or Lysander designs. The smaller crew requirement and lower effective maximum speed may signal a shift in League tactics from central reserves towards dispersing forces through individual systems. Alternately the League may be assembling a heavy core to its expeditionary fleet, something which would increase its leverage against the League of Theros.

Given League regulations about inversion times, the Polydeukes class will have a maximum range of 550 light-years in a single cruise during normal circumstances, while the maximum possible distance that the Polydeukes can cover without resupply would be just over 1,200 light-years. This would allow the Polydeukes to cover the distance between the farthest separated League poleis (Magna Gaia and Neue Bremen) in slightly less than three weeks. While impressive, this might still allow a more concentrated power, such as the Kingdom of Therennis, to attack separated League systems before reserve forces can respond.

4.4.2. The League Patrol Ship Odysseus

The Odysseus is the tenth ship built to the same hull as the Ajax. The type has proven successful enough for the League of Theros to consider building an additional production run to be divided between export markets, defence of the Magna Gaia system, and raids against the neighbouring Boetican Alliance and Hellenikan League. Although interest exists in exported versions of the Odysseus, the use of patrol rated ships by single-polis governments is on the decline, and the League of Theros has somewhat strained relations with the other large governments.

Although it has a complement of 60-kg cannon, and a theoretical throw-weight of over 900 kg (equivalent to a Warship of rating 2), the Odysseus is no match for any actual warship. It is unable to fire its full complement of weapons accurately, and lacks the reactor power to maintain a high rate of fire. Additionally, it’s main weapons have only 45% as much power as warship-level guns (100 km/s vs. 150 km/s). Were the Odysseus to engage a warship, it would likely do only light damage, but a single on-target shot from a warship could cripple or destroy the Odysseus.

The greatest weakness of the Odysseus is its disappointing ΔV — although the fuel fraction was designed to supply a ΔV of 2,000 km/s in cruise mode, the Ajax had only half that, and even the Odysseus, which was refitted with a different drive system, has only 75% of its rated ΔV. Problems seem to exist with the Hellenikan League’s sixth generation 3He-D reactors when scaled down in size for patrol ships.

4.4.3. Her Majesty’s Courier Hermes

The Hermes is the first of over thirty couriers designed on the same basic hull plan. While most of the class server as couriers, some are instead used as scouts and intelligence-gathering ships. The combination of a reliable and fuel-efficient drive, a generous ΔV, and a long cruise endurance make the Hermes a favourite in both roles.

As a single-polis government, the Kingdom of Nea Korkyra has little need of the Hermes in its role as a courier, instead making most of the production run available for export. The major customers have been the Hellenikan League and the Boetican Alliance, both of which see the advantage in a fast courier which can easily be refitted for spying. The standard refit involves the removal of most of the cannon and the addition of a 3-person intelligence team, along with additional sensors.

The Hermes has also, for whatever reason, become extremely popular with entertainment producers, with several running series set onboard such ships. Although the Hermes of entertainment fame can take on and defeat warships in open combat, the actual courier lacks even the ability to accurately fire its small weapons complement at targets farther away than 30,000 km. If spotted by opponents, the only recourse of the Hermes is to run away as quickly as possible.

4.4.4. The Merchant Ship Tyre

The Tyre is a typical merchant ship, equipped with a generous payload fraction (50%), and barely enough fuel to match velocities between stars. The Tyre’s low thrust level also means relatively long journeys, typically averaging three weeks between systems. This long travel time requires the Tyre to carry a large crew, especially if passengers are onboard. The Tyre design was first used by Natashira Polis, but has been licensed to many other poleis.

The Tyre uses a once military-grade fourth-generation torch drive, the Herakles Brightstar IV. Since its operation and maintenance requirements are extremely similar to those of the current top-of-the-line Herakles torch (used in several rated warships), some poleis have been accused of co-opting engineering crews from Tyre-type ships in orbit in order to man their warships. With the increased use of older military-grade torch drives in merchant ships, this problem may grow with time.

4.5. Society

Since this article is much more about the physics than about the society of my universe, I’m going to provide only a general overview. After all, any number of societies could evolve to fill even such a specific setting as this example. The society here, however, is one that I’ve been developing for some time, which I believe would fit in well in this universe.

I posit roughly 20 known inhabitable planets, spread through a rough sphere of radius ~600 light-years. Most planets have a large number of small islands, but no actual continental groupings. As a result, individual settlements tend to be fairly small, and the average unit of government is the Polis, taking up one island or island group. Most planets thus have many different small nations on them.

Each polis is recognized as independent, even if it happens to belong to (or have been subjugated by) a larger government. As a result, large governments are closer to being loose alliances (like the Hellenikan League), single planets with large continental land masses (like the Boetican Alliance), or small groups of poleis holding hegemony over a larger number of clients (like the League of Theros). The feel is consciously Greek, particularly maritime Greek (Athens, the League of Delos, etc.), although there are definitely differences.

Warfare is also a much different matter from today. Wars are expected and commonplace, but extremely limited. Small groups of elite soldiers fight on the ground (especially given the costs of transporting large groups between star systems), as do small fleets of ships in space. Due to the physics of the setting, ground attacks by starships are difficult and largely ineffective, so most battles remain extremely limited affairs, and the involvement of the civilian population in warfare is rare.

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Entry last updated March 4, 2005

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