Locating and Maneuvering Planets and Starships within a Star System

[flykiller]

(looking for comments, criticisms)

Band/Arc Method of Locating and Maneuvering Planets and Starships within a Star System

Depicting the vastness of space within a star system in a playable manner is difficult. Boards and vector methods are too big, while abstract locality depictions pass over so much detail that vital factors such as differing ship agilities and planetary orbital motion are lost. The Band/Arc method depicts location and movement within the vastness of a star system using only simple numerics.

At the center of the star system is the star. Each band lays outward from the center in numerically ordered rings, starting with 0.

star
band 0
band 1
band 2
band 3
band 4

etc.

Each band is divided into arc sections, the number of which is equal to the band number times 6.

star
band 0, 0 arcs
band 1, 6 arcs
band 2, 12 arcs
band 3, 18 arcs
band 4, 24 arcs

etc.

A location within a star system may be described with two numbers, the band number and the arc number. Thus, 4/18 means 4th band, 18th arc.

Band numbers are equal in distance and do not necessarily correspond to orbit numbers. Using our own solar system for an example:

Sun GV
(band 0 unavailable)
band 1, orbit of Mercury
band 2, orbit of Venus
-(Sun's 100d limit)
band 3, orbit of Earth
band 4
band 5, orbit of Mars
band 6
band 7
band 8, orbit of Asteroid Belt
band 9
band 10
band 11
band 12, orbit of Jupiter
band 13

etc.

Each planet's arc location on a band may be specified, thus.

Sun GV
(band 0 unavailable)
01/03, Mercury
02/12, Venus
-(Sun's 100d limit)
(H)03/02, Earth
04
05/19, Mars
06
07
08/xx, Asteroid Belt
09
10
11
12/56, Jupiter
13

etc.

Mercury in band 1 orbits the Sun in 88 days, thus each of its 6 arcs is traversed in 15 days. Thus, 15 game days after Mercury first enters 01/03, it will then be located in 01/04. Upon traversing 01/06, it will then pass to 01/01. Earth orbits the sun in 365 days, thus each of its 18 arcs is traversed in 20 days, thus 20 game days after entering 03/02 Earth will then pass into 03/03. In 440 game days from first entering 03/02 earth will have traversed 22 arcs, and will then be located in 03/06. And so on.

(Orbital periods may be derived from data from our solar system, or be made up, or be set up however the referee wishes.)

(Advanced topic: this could be used to implement jump masking between star systems.)

Ships with maneuver capability may maneuver from one arc to another and/or from one band to another. The ship's maneuver rating equals the sum of bands and arcs the ship may traverse during a game day.

To maneuver along a band, a ship simply traverses a number of arcs in that band. For example, a ship with maneuver two may transition from 03/05 to 03/06, to 03/07, to 03/04, or to 03/03, in one game day.

To maneuver between bands requires some simple arithmetic, because the ship must specify which arc it winds up in and the number of arcs changes from band to band.

For example, moving starward, a ship at 12/33 is to manuever to band 11. Take the arc number the ship is at (33) and multiply that number by the band number it is going to (11), and then divide that result by the number of the band from which it came (12). 33 * 11 / 12 = 30.25. Since the result is not a whole number the ship may choose which arc number to wind up in, 30 or 31. Thus, from 12/33 and heading starward the ship may maneuver to 11/30 or to 11/31.

For example, moving outward from the star, a ship at 03/09 is maneuvering out to band 04. Take the arc number the ship is at (09) and multiply that number by the band number it is going to (04), and then divide that result by the number of the band from which it came (03). 09 * 04 / 03 = 12. Since the result is a whole number the ship can go from 03/09 only to 04/12 if heading outward.

For example, moving starward, a ship at 07/19 wishes to traverse 5 bands, to band 02. 19 * 02 / 07 = 5.4, meaning the ship may wind up at 02/05 or 02/06, player's choice. Let's say the player chooses 02/06. If the ship has maneuver 5 then it may maneuver no further during that game day since it has traversed 5 bands, but if it has maneuver 6 it may then continue maneuvering to 02/07 if the player desires, or to 02/05, or to an adjacent band, and then be done maneuvering for that game day.

Maneuvering into band 0, there is no arc to pick - the ship simply is in band 0. Maneuvering out of band 0 to any other band, the player may pick any arc number in the destination band he desires.

Navigation example. A maneuver 4 warship at 05/17 wishes to refuel at a gas giant located at 07/27. The ship first maneuvers from 05/17 to 05/19 - this uses 2 of its 4/day maneuver factors. It then maneuvers straight out from 05/19 to band 07. 19 * 07 / 05 = 26.6, thus the ship may choose to enter either 07/26 or 07/27. It chooses 07/27 to reach the gas giant and refuel. Thus the maneuver factor 4 warship transits from 05/17 to 07/27 in one game day.

Ships may jump into or out of any band/arc that is not inside the local star's 100d limit and not occupied by a planet. Band/arc's occupied by planets are also considered to consist of that planet's 100d limit, and also to contain any moons orbiting it.

Ships may engage in combat only if they are located in the same band/arc.

Any star system generated by Book 6 may be readily expressed using this method.

Example Battlespace Depiction:

GV Jewell System
01/02 Signet
02/12 Ring
-(star 100d limit)
03/12 Jewell, Imperial Fleet 12
04/16, Imperial Fleet 03
07/41, Large Gas Giant, Imperial Fleet 04, Zhodani Fleet 17
07/30, Zhodani Fleet 18, Zhodani Fleet 19

etc.

(Conceived with HG2/TCS in mind, but I suppose it could be used with other systems. Also useful for bulletin board and email games, since the star system depiction only requires a few lines of text.)

 

[aramis]

A similar approach is used in Starfire.

Starfire, however, uses a % rating rather than number of hexes.

Also, each hex in starfire (on the system map) is given a specified size.

But, for inner solar system use, I'd use 1 LM hexes; for deep, 8LM hexes (which puts earth in band 1, mars in 2...)

 

[flykiller]

A similar approach is used in Starfire.

I'm fairly ignorant of other games, I suppose some duplication is to be expected.

Starfire, however, uses a % rating rather than number of hexes.

that sounds great for a vector system, but I wanted something that didn't have to account for every possible distance factor. I'm looking for something that has discreet macro locations where the referee can say, "ok, you're in the same hex, you can fight/trade/whatever" or "you're not in the same hex, can't interact yet" or "you're in the same hex as the planet, you're at the planet."

Also, each hex in starfire (on the system map) is given a specified size.

actually, the numeration system I specified does in fact describe a hex system. didn't quite realize it.

(among other things this allows easy translation between text descriptions and physical gameboard placement.)

But, for inner solar system use, I'd use 1 LM hexes; for deep, 8LM hexes (which puts earth in band 1, mars in 2...)

(with 1 LM hexes, earth would be in band 9, yes?) well I'm trying to create a gamespace where maneuver factor plays a role, where the difference between M2 and M4 and M6 matters. rigorous astronomical depiction is secondary. the hexes would not represent any specific distance, but rather a relationship between the various maneuver ratings. for example, mars is 750 LS from the sun, while jupiter is 2500 LS out. but in a hex system that is based not on distance but on travel times that doesn't mean that mars should be in (say) band 5 while jupiter is in band 17 - band 10-12 may be more appropriate for jupiter.

 

[aramis]

In 8lm hexes, earth is in 1.

with 1 lm, it's in 8, not 9, as earth is 8.333 LM orbital distance (aka, 1 AU)

If your movement units are not consistent size, they they are meaningless... as you can't make transverse motions.

 

[flykiller]

yeah, you're right ....

 

[BetterThanLife]

If you want to get serious you also have to take into account gravitational fields, especially when you get fairly close to the planet. You also have to be able to figure orbital velocity of all the bodies, not just the planets, but also their moons.

If you don't know how fast they are traveling about their star and how fast they are rotating. This is important for things like Matching vectors, orbital insertion, stable orbits, altitude of geosynchronous orbit, location of High Ports, etc. Heaven forbid that their highport is over the equator in Geosynchronous Orbit with a elevator running down to the surface and you happen to be in a low altitude polar orbit doing a survey or SAR operation. Space Traffic Control might get a bit miffed.

In all fairness it isn't all that important, from a RPG standpoint. You know where you are going, you know about how far it is, you can calculate travel time. The only time that, in an RPG, where the Maneuver Drive rating is important to calculations other than simple time vs. distance is when you are in relatively close proximity to something and have to interact with it. Otherwise a Star system is a fairly empty place and nothing really cares how fast you are going.

 

[flykiller]

In all fairness it isn't all that important, from a RPG standpoint. You know where you are going, you know about how far it is, you can calculate travel time. The only time that, in an RPG, where the Maneuver Drive rating is important to calculations other than simple time vs. distance is when you are in relatively close proximity to something and have to interact with it. Otherwise a Star system is a fairly empty place and nothing really cares how fast you are going.

from an rpg standpoint, agreed - but I was thinking in terms of wargame, or when the rpg becomes a wargame. in that case it matters a great deal how fast a fleet moves, how long it takes to get from one location to another, whether anyone is in weapons range or not, where a fleet should jump in, where the convoy supply ships need to be in order for their escorts to intercept in time anything that attacks them. yes, a system is mostly empty - but not when the ships arrive. if someone jumps into a system some distance from a gas giant, I'd like to say 1) oh, you arrived in hex 09/44, and there just happens to be an SDB squadron in hex 09/43, stand by for combat, or 2) oh, you arrived in hex 09/44 and there just happens to be an SDB squadron in hex 08/34, it'll be a day before they arrive to fight you. and I want to say it with individual ships and with fleets, in a bulletin board game, without relying on huge physical game boards or involved vector math.

 

[BetterThanLife]

Originally posted by flykiller:
</font><blockquote>quote:</font><hr />In all fairness it isn't all that important, from a RPG standpoint. You know where you are going, you know about how far it is, you can calculate travel time. The only time that, in an RPG, where the Maneuver Drive rating is important to calculations other than simple time vs. distance is when you are in relatively close proximity to something and have to interact with it. Otherwise a Star system is a fairly empty place and nothing really cares how fast you are going.

from an rpg standpoint, agreed - but I was thinking in terms of wargame, or when the rpg becomes a wargame. in that case it matters a great deal how fast a fleet moves, how long it takes to get from one location to another, whether anyone is in weapons range or not, where a fleet should jump in, where the convoy supply ships need to be in order for their escorts to intercept in time anything that attacks them. yes, a system is mostly empty - but not when the ships arrive. if someone jumps into a system some distance from a gas giant, I'd like to say 1) oh, you arrived in hex 09/44, and there just happens to be an SDB squadron in hex 09/43, stand by for combat, or 2) oh, you arrived in hex 09/44 and there just happens to be an SDB squadron in hex 08/34, it'll be a day before they arrive to fight you. and I want to say it with individual ships and with fleets, in a bulletin board game, without relying on huge physical game boards or involved vector math. </font>[/QUOTE]whne you jump into a system the SDB squadron can either generate an intercept vector or it can't. The convoy is going to arrive over the space of 4-6 hours or so in a fairly small volume of space and the escorts are going to camp on that volume until the last of the convoy arrives.

There is no real need to mark out hexes for an entire star system, just what is local to what is going on. And Mayday is about right for handling that. Besides the average sector has over 400 systems. Each system generation, using this work would take days to map and a degreee in Physics to compute all the orbital mechanics. Then tracking everything in a star system would take way to much time for the little use you will get out of it. Further hexes only really are good at representing 2D space. Who says everyone, every planet, moon, comet, companion star, etc. will be on the ecliptic? It is too much to keep track of for little real impact on game play.

Don't sweat that much number crunching. Fight your battles, or interact locally using a system like Mayday and don't sweat the rest.

 

[aramis]

BTL: You STILL being a pessimist?

Mapping it out in starfire is based upon a reference date, with one extra roll per world: the %.

Multiply the % * 6 * ring to find starting hex, and then add 1 per x days, from a table lookup.

Quite playable.

 

[BetterThanLife]

Originally posted by Aramis:
BTL: You STILL being a pessimist?

Mapping it out in starfire is based upon a reference date, with one extra roll per world: the %.

Multiply the % * 6 * ring to find starting hex, and then add 1 per x days, from a table lookup.

Quite playable.

It just seems like an awful lot of work for very little return. While I have had some of the physics for orbital mechanics, and it has definitely been a while ago, to do this right, requires quite a bit of work. If you aren't going to do it right then there is actually little point in doing it at all.

A small system with a low tech base and limited traffic wouldn't be difficult to do, but there is nothing there to really interact with in the first place so little point in going into this kind of detail. A High Traffic system on the other hand wit its orbital infrastructure, heavenly bodies, small craft, normal intersystem and interstellar traffic would be extremely time consuming to generate anything close to realistic, and players being what they are, would likely go unnoticed as they simply pop over to the Highport, tank up, swap out cargo and passengers and leave. A system like Glisten would be impossible to get anywhere near close to correct.

Hell without serious interplanetary traffic, scientists still don't have this system mapped with anything but the large bodies and the orbital traffic in relatively close orbit around Earth reasonably covered.