Key Assumptions for a Spacefaring Game

I've been doing more brainstorming about a spacefaring game. These are some key assumptions I'd make about the setting in order to facilitate play.

SUB-LIGHT INTERPLANETARY TRAVEL

ION DRIVES. The characters have access to highly efficient Ion Drive (or similar) technology allowing constant acceleration of typical spaceships from 0.1 to 1 G (or so). This makes interplanetary travel fairly rapid. For example, with constant acceleration at 1G, you can travel from Earth to Mars in a matter of days. This allows you to basically assume that players enter any tactical encounter with any reasonable relative velocity vector that they want. It could also be used in tactical encounters to generate very small thrust (say, 0.5 to 1 or even 1.5 Gs).

Reaction mass expended in an enhanced ion drive for interplanetary travel purposes is essentially negligible because we are assuming an incredibly efficient thruster (many orders of magnitude more powerful than exists today). The downside is that these drives require a lot of energy to function, from, say, a fusion reactor. Less powerful variants might be powered with fission or solar sources.

Here's a useful rule of thumb to calculate travel time: If you accelerate at A gravities to midpoint, then turnover and then decelerate at A gravities to your destination, elapsed time is approximately 4 SQRT (D/A) days, with D in astronomical units.

So to travel from Earth (1 AU) to Mars (1.5 AU) at constant acceleration of 1g, it would take: 4 * SqRt (0.5 / 1) = 2.8 days.

SOLAR SAIL. A less expensive (and lower energy) variant of the ion drive is mature solar sail technology. The advantage to this is that it is theoretically fast. It also requires very little energy and thus is probably less expensive. The downside is that it is not very maneuverable. This could be an option for players on a budget but it would prevent them from entering encounters with whatever velocity they want.

HOHMANN TRANSFERS: Interplanetary Travel without constant acceleration is done on Hohmann Transfers. Generally, for game play purposes, it is not necessary to understand how these work: it is a long time, and you can do it with limited thrust (generally two burns suffice; an initial and a final burn). Hohmann transfers are used for a few gameplay purposes:

• Bulk cargo shipments from one orbit to another often use Hohmann transfers. For example, maybe the PCs get involved in an asteroid mining operation and need to get their bulk wares to somewhere else in the system inexpensively.
  
• Sometimes a system might have a space station or other useful object on a Hohmann transfer orbit.
• The PCs might be absurdly poor or limited on funds/local tech to old-school solid or chemical rocket technology.
• Escape capsules might use Hohmann Transfer Orbits. This is a nice penalty for "death:" if you have to eject from your crippled spaceship, the escape pod has just enough thrust to put you into a transfer orbit. It basically means that the penalty for "death" is weeks or months of inactivity while you sit in your life raft and think about failure (or pay for a lift from an ion-drive equipped salvage ship).
  

You can estimate the time required for one relatively easily, however:

P^2 = A^3 (where P = time in years and A = distance in AUs)
Steps to solve (example is Earth to Mars):

1. Add the distance of the first planet from the sun to the distance of the second planet from the sun (1 AU + ~1.5 AU)
2. Find the semi-major axis of the transfer orbit by dividing this number in half. (2.5 AU / 2 = 1.25 AU)
3. Solve the above equation. Use a calculator... (P = ~1.4 years)
   
4. The equation gives you the time for a full orbit (i.e., Earth to Mars and back). Divide this by two to get the one way travel time. (0.7 years or around 8 months)
   

CHEMICAL DRIVES: Liquid and solid fuel rockets are still useful. They provide very high impulse. They are also cheap. This makes them great for tactical maneuvering on a "fighter" type spacecraft; generating 1G on an Ion Drive is not going to stack up favorably against a fighter maneuvering at 9Gs. Additionally, they are cheap and simple to operate.

The downside is that they require a lot of mass for fuel.

SUB-LIGHT INTERSTELLAR TRAVEL

ION DRIVES. The Ion Drive can also be used for interstellar travel. In general, the amount of time it takes to get from one system to another with constant acceleration at >0.5G is the distance in light years plus one. So, to travel two parcsecs (about 6 LY) takes about 7 years with an ion drive. Mass consumption is significant at these distances and should probably be checked for each parsec of travel.

Over long journeys, relativistic effects can occur; for example, it traveling 3 LY (1 parsec), people on the planets age 5 years but those on the ship age only 4. if traveling 6 LY (2 parsecs), planet dwellers age 13 years and those on the ship experience only 13. The bottom line is that I don't expect PCs to travel this way most of the time, so it isn't a factor other than to understand abstractly; there may be "gypsies" that travel from system to system with ion drives at velocities which are high percentages of C that essentially accept that everything they once knew on a planet will be left behind.

SLEEPER SHIPS. Cryogenic technology allows passengers to be put into suspended animation. This allows a ship to burn up to a significant fraction of C (say, 0.05 to 0.1) but only twice (to accelerate then decelerate). Travel in this method takes decades or centuries to go even a few parsecs. The PCs might occasionally come across an old sleeper ship. Under very rare circumstances they might be forced to travel this way due to limited technology or funds. Travel in this manner might be a good way to basically start a new campaign.

FASTER-THAN-LIGHT INTERSTELLAR TRAVEL

There are three FTL technologies available for interstellar travel. Any or all of these may be unavailable in any given campaign. In particular, jump drives and warp drives work in a very similar manner and could easily be combined, i.e., there could be man-made wormholes. These technologies are useful within a globular cluster of systems or a spiral arm, about 20-30 parsecs in diameter.

JUMP DRIVES. Special jump drives allow travel between systems by exploiting "temporary" wormholes. The wormholes link nearby systems forming "space lanes." While temporary in astronomical terms, they generally remain stable for long durations in human terms. This allows the GM to add or remove space lanes occasionally. The wormhole is great because it allows travel that might normally be measured in parsecs to be completed in days. The downside is that both ends must be charted in order to safely jump. Additionally, these routes are predictable, which means that pirates and others often prey on them. Finally, the jump points are not always conveniently located.

More powerful jump drives allow longer jumps to occur, on the order of 1-9 parsecs. Regardless of the length of the jump, travel time is always the same (around a week). Ships in the wormhole cannot generally interact with anything outside the wormhole, and interactions within wormholes are very rare and unpredictable.

WARP DRIVE. This is based on the Alcubierre Drive. It works just like a wormhole except that the infrastructure to travel is man-made, not reliant on natural phenomena. Ships in warp drive cannot interact with the outside universe outside their warp bubbles.

HYPER DRIVES. Hyper drives allow a ship to "sidestep" into an alternative dimension (hyperspace) where travel at FTL speeds is possible. The advantage of hyperdrives is that unlike Jump or Warp drives, one can travel anywhere independently of Wormhole entrances or Warp Drive infrastructure. With a hyperdrive, it takes a number of days to travel somewhere equal to the number of lightyears + 1 (thus to go two parsecs takes a week). Hyper drive is popular with scouts and explorers (as well as pirates, recluses, or others who want to travel to obscure backwaters or avoid chokepoints and checkpoints). There are several downsides to hyperdrives:

• Expense.
• Fuel consumption; the vessel is constantly accelerating within the hyperspace bubble, requiring fuel expenditure.
• Limited mass. There should be a non-linear energy cost to bring objects into hyperspace, preventing it from being useful for mass commerce.
  
• Need for precise calculations. There is a significant chance, especially over longer jumps, that the ship will not end up exactly where intended. This effectively caps safe travel ranges at 1-9 parsecs per jump. The ship will likely need to drop out of hyperspace for navigational fixes on a regular basis.
  
• Gravity Well sensitivity: Hyper Drives cannot be safely used close to stars or other major gravity wells. While some systems have Warp infrastructure or Wormholes at more convenient locations, a hyper-drive equipped vessel always needs to navigate to the outer edges of a system in order to safely jump. Of course, under extreme circumstances, a hyper jump can occur (for example, to escape), with unpredictable results...
• Time. Hyperdrives can be faster for short trips of 1-2 parsecs, but anything longer is faster to do with a Jump or Warp drive.
  

FASTER-THAN-LIGHT INTRAGALACTIC TRAVEL

The three technologies above are ideal for travelling distances of 1-9 parsecs at a go. They are good for traveling within one spiral arm or globular cluster of a galaxy. Travel across a galaxy requires movement rates in Kiloparsecs. Some obscure, rare, and expensive technology might allow such travel. As an example, the milky way is 30 kpc in diameter.

This technology should be rare and expensive with perhaps limited usage or requiring highly specialized ships. Alternatively, very rare natural phenomena such as the Deep Space Nine wormhole might allow such travel.

FASTER-THAN-LIGHT INTERGALACTIC TRAVEL

Travel between galaxies is exceedingly rare. Intergalactic travel should be a one-time event leading to dramatic changes in the campaign. Intergalactic travel is measured in megaparsecs. For example, the nearest other galaxy to the Milky Way, the Andromeda Galaxy, is 0.77 mega parsecs (770 kpc).

ALIENS ARE RARE OR NONEXISTANT

There are not many sentient alien life forms. The explored systems are decidedly humanocentric. As humanity has spread out, some humans have adapted to different local conditions, such as high or low gravity, but they are still decidedly homo sapiens. The exact reason for this is unknown.

EARTH IS DISTANT

The game occurs in a different "neighborhood" of the galaxy than Earth. Maybe it is a different spiral arm or globular cluster. In any event, due to the travel limitations described above, each globular cluster is fairly isolated with limited travel between them.

Alternatively, Earth has been destroyed by some cataclysmic disaster.

In any event, the theme should either be one of a fallen empire or of an isolated backwater sector.

MOORE'S LAW IS DEAD

Moore's Law states that computing power doubles every 18 months. Starting in the early 21st century, computing technology rapidly leveled off as in an S-curve. While it has advanced since that time, computing power is not exceedingly greater.

Additionally, there are strong taboos against various forms of artificial intelligence, especially AI for controlling weapons or other potentially lethal systems as well as any sort of interstellar FTL travel. Perhaps there is a history of Earth being destroyed by rogue Unmanned Systems. There is a chance that AI used for FTL travel pilotage will for some reason malfunction with potentially disastrous consequences.

PLANETARY LIFT IS LIMITED

There are a few ways to get stuff from the surface of a planet into orbit. They are limited. Generally, player spacecraft are not great at operating freely in an atmosphere or strong gravity well. The purpose of this is to keep the focus of action in space, not on planets. Travel to planetary surfaces should be the exception, not the rule.

• Space Elevators: Very developed planets that regularly move large masses to orbit may have a space elevator established. This allows the PCs to pick up and drop off cargos from orbit.
• Mass Drivers: Lower gravity planets may have large mass drivers to launch objects violently into orbit. While not good for fragile cargos, this method is highly efficient for bulk materials. A mass driver might even be able to place cargo into a Hohmann Transfer orbit.
  
• Space Stations: Many planets may establish space stations as way points. For example, if traveling from a planet to its moon, it would make sense to have a station in Earth Orbit and another in Lunar orbit. Shuttles to and from the earth are designed to operate in atmosphere; those between the stations can be designed for pure vacuum operations; the final link to the lunar surface can be designed for lunar landing. If regular commerce occurs it is more viable to have a station, even a small one, and specialized rockets than to try and build a multipurpose space vehicle. Heck, even Earth today has a small manned station in low orbit.
  
• Occasional orbital shuttles: The least populous and most backwards planets may just run an occasional shuttle to orbit. Cargoes might be launched with single-use rockets as needed.

FTL COMMUNICATIONS DON'T EXIST

In general, there are no faster than light communications. Interstellar FTL comms are limited to mail runs on FTL-drive equipped ships. Due to the prohibition on AI FTL drive operation, generally mail runs are carried on manned ships. This means that systems are relatively isolated from one another, making decisive local action important, and gives the PCs something important to do (carry mail and act as couriers). It also limits the scope/size of any sort of interstellar authority and forces decentralization.

G-Limits

I just had a lecture on human G-limits and some training. I'm not an aviator but I have flown in some high performance aircraft and pulled significant Gs. It isn't easy, and equipment/training helps.

Here's some rules of thumb for sustained Gs:

1-3 Gs: Generally no problem for people in average health
4-6 Gs: Gray out occurs. Untrained personnel or unprepared people can black out or suffer G-LOC.
7-9 Gs: Without G-training and equipment, blackout or G-LOC is likely. Even trained people will find this challenging.
10+ Gs: Generally leads to G-LOC

Partial G Suit: +1.5G
Full G Suit: Add +2.5G
Anti-G Straining: Add +3G
Adjusting seat tilt from 30 degrees to 65 degrees: +2G

Negative G is much harder to deal with; humans can handle about 1/2 that G-Load.

What this means for a Game?

As previously discussed, acceleration is the key thing for a space game that should determine scales, not velocity. Let's assume a system where 3 Gs = 1 square of movement, 6 is 2 squares, and so on. If you are accelerating at less than 3 Gs (say, a gentle 1G push) then you have a 2/6 chance of accelerating one square. A super-gentle 1/2 G push would be but a 1/6 chance.

If you assume a one minute turn, then 3G acceleration gets your velocity increased by about 1800 meters. Round it off to two clicks to make the math easy, or down to 1 click and use ~30 second turns instead of one minute turns.

With this sort of system, you'd be able to make a light burn to add 1 hex to your velocity, a moderate burn to add 2 hexes, and a strong burn to add 3. We could postulate some sort of enhancements to human physiology/g-suit technology that might make burns of10-12 G's possible that would allow adding 4 hexes to your velocity.

Alternatively, you can use an alternate G-scale (perhaps going in units of four or six instead of three). This would allow much higher velocities to be rapidly attained, and basically assume that a combination of properly reclined seats, improved G-suits, and perhaps sci-fi tech is in play to allow those greater accelerations. This would basically require hexes of 3 or 4 KM in size rather than 2 KM.

Modeling G-LOC

You could say that 1-3 Gs is no problem. Once you hit 4Gs, then you need to start making some sort of check or take damage. Bonuses to the check could be obtained from a hardy constitution/good health and high-G training (G-straining maneuvers). Moreover, appropriate equipment could give bonuses to the G's you can handle without trouble. For example, maybe having a G-Suit gives you another +3Gs of tolerance and having an acceleration couch designed for high G gives you another +3G. That would let a pilot of an optimized high-G spacecraft to pull up to 9Gs (3 hexes) without making a single check.

The G-LOC "damage" track might have three hits, or combined with some sort of "stunning" damage:

• First Strike: Greyout. Minor impairment.
  
• Second Strike: Blackout. Vision severely impaired. Other functions severely impaired.
  
• Third Strike: G-LOC. You're out.

You could require folks to make one save for each category of acceleration they're exceeding their safe threshold by. So, say you are just an average Joe in a Space Civic. You have no G-protection devices. Your safe max G is 3. You initiate a maneuver that pumps you up to 9 Gs. You're going to go from just fine to "blackout" if you fail your tolerance checks. So, an experienced high-G pilot who knows how to G-strain and is in good shape might be able to take it, but the average Joe is going to be mighty close to passing out. Heck, even that simulation is pretty generous I think because most folks would actually pass out if rapidly accelerated to 9G with no protection.

Character Builder is Dead... Long live Character Builder!

I've got a DDI subscription which I got for a web based campaign that is stuttering off the runway. One of the tools I appreciated most is the Character Builder application. For those who are unfamiliar, it is a standalone little program WOTC put together which lets you easily and quickly build PCs. It actually works pretty well and is basically the only way short of reviewing the 4E Char Op boards to build a character in 4E. It honestly makes buying splat books irrelevant, which is nice.

Of course, I'm sure I'm not the only one that realized that you could get a short subscription, download Char Builder, and then cancel your DDI subscription. Every few months you could get a new subscription to download new updates. WOTC tried to crush this by limiting updates to a handful per month (so you can't spam it to a bunch of computers) and by scaling their pricing scheme to reward you for longer quarterly or annual subscriptions.

However, WOTC has announced an "upgrade," in that the old standalone character builder will now be dead. Instead, you get an internet based application. There are some actual improvements. However, I have mixed feelings about getting rid of the standalone application. I liked the utility of being able to build a character anywhere: on an airplane, while deployed, or just generally away from the internet. Now, you can only use DDI when there is internet handy. I suppose as wifi becomes more and more prevalent this is less of an issue but still, I don't love it.

From the business side, they now lock you into a continious subscription as you have no standalone option anymore. You can't pay for a one-month subscription to get the jewel in DDI's crown. You need to pay for an annual subscription to keep access to your character sheet.

I'm also concerned that they will freak out on me for sharing an account with Mrs. Nittany. If I'm traveling for work and log on from some random place and she logs on at home, will WOTC get upset at us? Who knows!

Anyways, we'll see. I'm not sure I love this new release. I think that WOTC should consider two tier pricing: a DM price that gives access to all content and a player price that just gives you the Compendium and Character Builder. I don't know if I'm willing to pay $60/year to play 4E D&D.

Space RPGS: Flight Models II

In my previous post I wrote about some considerations for spaceflight models, and identified the key variable as acceleration rather than velocity. I did some more thinking and research and came up with a few implementable options. Adding vectors is fun!

• Ignore Momentum. I don't like this as it is totally unrealistic and makes a space RPG feel like any other wargame or token-based RPG.
• Abstract Movement. You could go with a early CRPG style representation: one side lines up on the left side of the board, the other on the right, and they fight in a very abstract manner. You could have rules for maneuvering which could help for dodging attacks, or maybe range categories ("Close, Far, Disengaged...").
• Track Each Vector's Values: You can track the speed associated with each vector for each token. For example, you could represent something's velocity as follows: "North 2, East 1, West 0, South 0." If the vehicle accelerated to the North 2 and West 1, then you'd modify the numbers to 3/0/0/0. Each turn the vessel moves in the appropriate number of squares. This works great for a small number of tokens. However, if you have multiple tokens it gets troublesome to keep track of as you basically need a separate worksheet for each vessel. Additionally, I think it is necessary to go for at least a hex based system to smooth things out. However, it is probably the easiest way to deal with 3-D movement. It is also easier to deal with higher speeds as you can just subtract X from everyone's speed in a certain direction without changing any of the relative velocities.
  
• Use Two Tokens for Each Vessel: You can also use two tokens to represent velocity. In my previous example, you'd have one token representing where the ship is and a second representing where it is going, two squares to the North and one to the West. After acceleration, you'd move the second token one space to the East and one space to the North. Before moving the ship, drop a third token 3 squares to the north of the second one. The advantage of this system is that you can keep track of larger numbers of vessels with relatively little difficulty. The trouble is that you need multiple tokens/minis to run it all and as velocities get larger there is a greater chance for error to occur.
• Trigonometry: You could use trigonometric functions to add vectors. I think this would likely require a table of look up values. It would allow you to play without minis, however.
  

Space RPGs: Flight Models

I've been thinking a lot about a space RPG lately. I never played Traveller, but I've reviewed it, and it is far too complicated. I know that Traveller spawned Elite, which in turn spawned Privateer (which was a childhood favorite game of mine), but it is just too much for me to want to run as far as rules go these days.

One problem that I've been putting some brain bytes towards is how to handle space combat. There are two approaches: realistic physics or arcade style. Video games had to deal with this too. Arcade style is popular because it is easier to grok, even if it is unrealistic. An example would be violating the law of conservation of momentum, capping maximum speeds in a vacuum at something significantly less than C (speed of light), and so on.

An RPG could go with the same sort of idea: each turn, a sub-light ship moves X squares and can make Y changes in direction. This effectively taps maximum speed at X squares. You could even justify it by saying that the sub-light technology has some sort of special property that perhaps cancels out inertia or momentum (converting velocity to heat or something).

However, this totally disregards some unique aspects of spaceflight. For example, if a ship continually accelerates at 1 MPH, its velocity will eventually get to be significantly greater than 1 MPH! One of the advantages of traveling in a vacuum is that you can get up to a great speed, especially if you have enough fuel/energy to generate thrust for 1/2 your trip. I think the solution is somewhere in between: use pseudo-newtonian rules that feel unique and space-shipish but are easy to implement.

I think the key is to focus on acceleration, not velocity. After all, if the relative velocity of the combatants is zero, you might as well be stationary.

The two things that help a lot as far as limiting factors go are:

• Limited Acceleration due to Gs: The human body can take about 9 Gs before G-LOC occurs. Much equipment may not be able to handle that much. For example, a spindly vacuum-only ship may only be able to take 1/2 to 1 G. While that is not a limit on velocity, it does significantly limit acceleration. 1 G is about 10 m/s^2, or approx 22 MPH (so if you could accelerate from 0 to 65 MPH in one second you'd feel three gees). In another example, the Apollo trans-lunar velocity was something like 25K MPH, which is about 11,000 M/S. A 3G (30 m/s^2) burn would have to burn for something like 6 minutes to get you up to that speed.
  
  Note that a human body can take something like 45Gs without breaking under certain conditions. However, if you're talking about sustained, fighting capability -- 9 Gs is a good rule of thumb.
  
• Limited Fuel: Unless you posit a never-ending energy source for your sci-fi world, then fuel will not be unlimited. Say your spaceship is 2000 tons, about the size of the space shuttle. Kinetic Energy = (1/2) mass * velocity ^2. A mass of 2000 tons is close to 2,000,000 kg, and the desired velocity for a 3-day moon shot is 11,000 m/s, so the energy wrapped up in that enterprise is 121,000,000,000,000 joules. By my rough reckoning that's about the amount of energy in a million gallons of gasoline, 7.5 million lbs of coal, -- assuming 100% perfect efficiency in the engine! If you could assume that you can crack uranium-235, it'd be much less (about 7.5 lbs), but the mass of the reactor would have to get added to your 2000 ton spaceship! With the exception of drives like Ion Drives or Solar Rocket Engines which are highly efficient as far as propellent usage goes (but provide very low thrust -- and thus are not tactically interesting for most PCs...), most of the other options use a ton of fuel and are propellant inefficient (TANSTAAFL). So, the bottom line is that if you limit fuel, then it will limit the "burns" that a ship can do, which limits maneuvering and acceleration.
  

Here's my rough estimate of how to figure out "useful" scales for tactical ship-to-ship combat. Let's assume that primary weapons are energy weapons, mass drivers/cannons, and missiles/rockets.

• Energy: A light-second is 300,000 km. Particle weapons would travel much more slowly than C, but for lasers, 300,000 km is probably a reasonable maximum range. Anything longer than that and you'll start to have aiming problems. Note that this is a problem with sensors, too; a radar or lidar pulse needs to travel two ways (out and back), and the maximum unambigious range is likely going to be much less depending on waveforms and whatnot. There are also problems with sensor range due to the formula for a sphere; the returning energy pulse is reduced by a power of 4*PI*R^2 so you need VERY sensitive receivers to detect a returning pulse from extremely distant targets, even without atmospheric attenuation.
  
  I also imagine that you'd have trouble with dispersal reducing the power level of the beam as it spreads over distance. You'd need a very tight, focused beam and the power will attenuate over distance. The YAL-1, a megawatt class laser, has range of ~600 KM vs. thin skinned targets in an atmosphere. Here's a quick back of the envelope calculation:
  
  Power Density = Transmitted Power / 4 * Pi * R^2
  Power Density = 1 megawatt / 12.56 * 600 KM^2
  Power Density = 1 megawatt / 4,521,600 KM
  
  So, I think something on the order of ~1000 KM is reasonable for desired weapons effects with a megawatt-class laser weapon in a vacuum. If you assumed that a sci fi laser would be a giga-watt class system (1000 times more powerful than the YAL-1), then perhaps closer to 20,000 KM as a WAG, although I'm sure an engineer would tell me how far off I am.
  
  Power Density = Transmitted Power / 4 * Pi * R^2
  1 megawatt / 4,521,600 KM = 1000 megawatts / 12.56 * R^2
  12.56 megawatts / 4,521,600 KM = 1000 megawatts / R^2
  R^2 * 2.7777777777777777777777777777778e-6 = 1000 megawatts
  R^2 = 360000000
  R = 18973
  (Sorry I got lazy and dropped the units... this is a WAG anyways...)
  
  Likewise, if you went DOWN to a kilowatt laser, then range would shrink to something like 50 KM vs. a thin skinned target.
  
  
• Projectiles: Range is effectively infinite due to Newton's First Law. However, against a maneuvering target, there might be problems with anything at longer ranges. If you assume a mid-case 6G manuevering target, then in one second that target can change velocity by 60 meters/second^2. A bullet usually goes at a velocity on the order of 1500 meters/second; artillery shells are much slower (hundreds of m/s) but we're in the ballpark. If you want to be able to hit a 10 meter sized "kill zone" on a maneuvering target, then your projectile needs to arrive in 1/6 of a second or you need to really be able to guess where it will be. That makes the effective range about 250 meters! That makes sense, though; ~750 feet is the heart of the envelope for a fighter aircraft trying to gun another fighter, which has similar acceleration and size issues; atmospherics don't even really come into it.
  
  If you're going after a 100 meter vital zone on a 3G target, then your bullet has 3.3 seconds, so max effective range would be ~4000 meters.
  
  
• Missiles: Like mass drivers/projectiles, range is effectively unlimited. In fact, it is greater because a missile (A) accelerates after launch and (B) can correct its course with terminal guidance. The only issue is how long it takes to get to the target, and if it has sufficient maneuvering ability to catch a maneuvering target.
  

So, really, tactical space combat scales can be smaller than you might think. Hexes as small as 250 meters might make sense! Remember, velocity doesn't matter; the only thing that matters is DELTA V (the difference in velocity between combatants). If you went with a 500 meter hex then you'd get the following:

• Guns vs. Maneuvering Point Targets: 1 hex range
• Guns vs. Non-Maneuvering Area Target: 8 hex range
• Megawatt Class Laser vs. Thin Skin Target: 2000 hex range (effectively infinite)
  
• Megawatt Class Laser vs. Medium Skin Target: 1000 hex range (still effectively infinite)
• Kilowatt Class Laser vs. Thin Skin Target: 100 hex range (still effectively infinite)
• Kilowatt Class Laser vs. Medium Skin Target: 50 hex range
  Note that if you posit armored targets, or better yet, some sort of energy shields, then you could shrink the ranges significantly, especially for a kilowatt class laser. The YAL-1 takes up an entire 747. I understand that sci-tech will make major strides in a sci-fi setting, but if you're talking about a laser that can sit inside a turret like you see in Star Wars, that's a LOT of miniaturization. So saying that small turret-based weapons are kilowatt class is reasonable. A megawatt class laser might be something like a mining cutting laser or a destroyer (not fighter) class weapon.
  
• 1G acceleration over a one minute period of time: ~1 hex delta vee (and this relationship holds fairly steady, so 9Gs = 9 hexes of delta vee)
  
  

The last bullet there is actually a good argument for using a 600 meter hex for tactical spaceship combat. It would basically create a 1G acceleration = 1 hex movement direct relationship, which is pretty sweet; it wouldn't really affect the maximum weapons ranges much, except that the guns vs. maneuvering targets is getting a bit optimistic. I can also think of some cool things you could do with a D6 and 600 meter hexes. The 500 meter hex is easier to extrapolate to greater ranges, however, and you could assume there are some inefficiencies in the burn or something that keeps acceleration from being perfect.

Alternatively, you could go with some multiple (2-3G) for the hex, which would lead you to 1200 or 1800 meter hexes. You could just round to 1KM, 1.5KM, or 2KM. That basically reduces movement rates for very rapidly accelerating objects such as guided missiles, but it also reduces movement rates for the typical player-controlled ship. If you think that a 3-5G rated ship is "typical" with 9-10Gs being a peak manned combat vehicle, then using 1800 meter hexes means that the typical ship only moves 1-2 hexes, which may not be very satisfying.

Remember, the key is acceleration capability in a fight, not velocity. Assuming that the combatants are intentionally getting into a fight, then one of them has matched velocity with the other. The aggressor in that case should basically be able to enter the fight with whatever starting relative velocity they want. For example, if they enter the fight with an advantage of +3600 KM/HR, then they'll have a velocity delta of 60,000 m/s, or 100 hexes. So, they'll blow through the engagement and only get one pass, which may be what they want. They'll have to do a long ~10 plus minute burn after blowing through to come around for another run which burns a lot of fuel.

It is much more fuel efficient to basically match velocities and enter the fight with manageable Delta Vee. That way you're not burning a bunch of mass to get up to high speed then burning yet more to rapidly decelerate. So letting the aggressor pick their starting relative Delta Vee advantage makes a lot of sense. In a more reasonable and tactical scenario, the aggressor could enter the engagement with a delta vee of +260 KM/HR, which gives them 10 hexes of movement. They could then make a pass on the victim, do a 9G braking burn, and be drifting along one hex faster than the target for round two of the fight -- a manageable place to be! It is a little more complicated than that because they could apply angular delta vee but still, you could come up with rules of thumb to keep it simple and manageable.

I'm going to stop now before I embarrass myself further. It has been a long time since I took physics. But I think that with some careful thought you can create a pseudo-Newtonian feel to the system fairly easily.

Correspondences of Seven

I've been coming up with a table of correspondences for the number seven, which is core to "Septimus." This is what I have thus far.

• Quality of Associated Signs: Each planet is associated with astrological signs as a "ruler." I've extracted the quality (fixed, mutable, or cardinal) of those signs.
• Elements of Associated Signs: Each planet is associated with astrological signs. I've extracted the element (air, earth, water, fire) of those signs.
• Humour: Each planet is often aligned with one of the four humours.
• Roman Deity: Each planet is associated with a Roman deity.
  
• Liberal Art: Dante Alleghri (yes, that Dante) associated each planet with a liberal art.
• Mechanical Art: I've matched up the planets with the mechanical arts.
• Probitate: I've also matched up each planet with a probitate.
• Metal: Each planet has an alchemical association to a metal.
• Primacy of Matter, Mind, and Spirit: Each planet has one of these three over another. For example, "Matter over Mind." You can extract it from the symbol for the planet.
  

	SATURN	JUPITER	SUN	MARS	VENUS	MERCURY	MOON
Sign	Capricorn	Sagittarius	Leo	Aries	Taurus	Gemini	Cancer
Sign	Aquarius	Pisces		Scorpio	Libra	Virgo
Humour	Melancholic	Sanguine	Choleric	Choleric	Phlegmatic	Variable (Melancholic)	Melancholic
Dante's Virtue	Contemplatives	Kings	Theologians	Warriors	Love & Friendship	Good for Fame	Virtue
Vice	Sloth	Pride	Greed	Wrath	Lust	Lying	Envy
Metal	Lead	Tin	Gold	Iron	Copper	Quicksilver	Silver
Roman God	Saturn	Jupiter	Apollo	Mars	Venus	Mercury	Diana
Greek God	Cronus	Zeus	Helios	Ares	Aphrodite	Hermes	Selene
Quality: FIXED	X		X	X	X
Quality: CARDINAL	X			X	X		X
Quality: MUTABLE		X				X
Element: EARTH	X				X	X
Element: WATER		X		X			X
Element: AIR	X				X	X
Element: FIRE		X	X	X
Primacy (Over)	Matter	Mind	Spirit	Matter	Spirit	Mind	Mind
Primacy (Under)	Mind	Matter		Spirit	Matter	Spirit
Primacy (Not Present)	Spirit	Spirit		Mind	Mind	Matter
Liberal Art	Astronomy	Geometry	Arithmetic	Music	Rhetoric	Dialectic	Grammar
Mechanical Art	Agriculture	Architecture	Medicine	Armament	Fabric Making	Commerce	Hunting
Probitate	Riding	Jousting	Climbing	Fighting	Swimming	Dancing	Shooting

Most of the linkages are straightforward. I'll explain the ones that aren't directly from the classical sources.

The mechanical arts:

• Agriculture: Saturn has a clear link to Agriculture. Heck, Saturn's symbol even looks like a scythe. This one is easy.
• Medicine: The sun is associated with Apollo, the god of the sun. Historically, the sun has been associated with positive, healthful things like the healing arts.
• Armament: This one wasn't perfect, but I thought a correspondence to Mars was appropriate. Traditionally, Hephaestus was the god of smiths. However, given the martial bent of Mars and the strong association with Fire, Mars is appropriate enough. I would prefer Fire + Earth.
• Commerce: Mercury is traditionally associated with Mercatura.
• Hunting: Diana, the huntress, is the patron of hunting. Easy.
• Fabric Making: Traditionally, Athena is the goddess of weaving. However, she doesn't have a planetary association, although she is sometimes linked to Venus. I ended up linking it to Venus almost by default.
• Architecture: This, like Fabric Making, was "left over" after I matched up all the other arts with their obvious associations. I paired it with Jupiter as Jupiter is associated with kingship, mind, and matter.

The probitates:

• Riding: I linked this with Saturn due to the agricultural association. However, the Roman God of horses was Neptune which could lead to a weak linkage with the element of water, which would be a reason to put riding elsewhere.
• Jousting: Linked with Jupiter. This was a "left over" as well and I dropped it here due to the linkage with kings. I thought about replacing it with Chess (tactics) as well.
• Climbing: Linked with sun. This was also a weak association, based solely on the idea of vertical ascent. It isn't bad, though, as Helios was known for climbing across the sky in his chariot every day. It would also be appropriate to use "Poetry & Music" here as Apollo was well regarded as a patron of both.
  
• Fighting: An easy linkage to Mars.
• Swimming: I paired this with Venus primarily based on the strong presence of the element water. Venus is the only Phlegmatic planet and has the strongest association with water.
  
• Dancing: This was matched with Mercury. Mercury was known for being fleet of foot as well as being very social, which is a nice match with dancing.
• Shooting: The link between archery and the huntress seems straightforward and natural.