This page was last updated on 1 January 1998.

Stellar Conquest/Triplanetary

by Brian McCue. (c)1993 Permission granted to copy for non-commercial use.

[Note: This is adapted from the instructions Brian wrote for his game group. I've tried to edit out all the references to submitting your turns on Monday, etc., but I may have missed a few.]


The basic idea is to play Avalon Hill's Stellar Conquest by mail and then fight out the ensuing space battles face-to-face using GDW's Triplanetary. Stellar Conquest portrays the grand sweep of galactic exploration and technical development. Originally created by Metagaming and later bought by Avalon Hill, it is known to computer gamers as Reach for the Stars. Triplanetary, unlike most space combat games, simulates the physics of space movement in an elegant vector formulation. The in-system Triplanetary battles will be fought out on solar system maps created to match the solar systems generated in Stellar Conquest. The fusion of these two classics promises a gaming experience second to none.

Players will need their own copies of the Stellar Conquest rules, and should be familiar with Triplanetary. They should be well-acquainted with the characteristics of the deck of star cards in Stellar Conquest. A non-player will be needed to serve as the umpire.

A complete turn consists of photocopies of the latest Stellar Conquest map and Player Record Sheet, and a listing of contents and destination for each task force if these have changed since the last turn. Most of the time all you will get back from the umpire is a phone call saying that nothing happened to you and that you should send in another turn on the appropriate. When one of your task forces makes systemfall someplace, you will be told of the outcome (ships lost in exploration, the details of the new system, or maybe even the presence of another player's forces). You will also get a phone call if another player's ships arrive in one of your systems. If combat is to be the result, you and the other player will schedule a game of Triplanetary to resolve it. (Except in the case of especially boring combats, which will, at the referee's discretion, be resolved otherwise.)

Relationship Between Stellar Conquest and Triplanetary

Each Triplanetary board is a Stellar Conquest star hex.

Each Triplanetary battle occurs during the combat phase of a Stellar Conquest turn. Exceptionally long Triplanetary battles (those greater than 90 turns) are carried over into the next Stellar Conquest turn. Exceptionally unpromising Triplanetary battles will be resolved using the Stellar Conquest combat rules or referee fiat.

Each Triplanetary Megacredit is 1/10th of a Stellar Conquest industrial point.

In Triplanetary terms, basic Stellar Conquest ships are as shown in the table below. Note that extra armament, limited by cargo capacity, may be bought according to the prices listed in Table 2 of the Triplanetary rules, and that doing so brings the total cost of the ships into line with the ratio that 1 Stellar Conquest IP = 10 Triplanetary MC. The exceptions are the transport and the tanker. The tanker is an addition to Stellar Conquest, made necessary by the use of Triplanetary rules to resolve combat Strictly speaking, the transport isn't Stellar Conquest's transport either, though it can be used as such to transport a colony. It can also be used to carry extra weapons for the warships to use and, consistent with the Triplanetary rules, it may drop mines but not torpedos.

See also the Appendix for a derivation of the Stellar Conquest ships in Triplanetary terms.

Table 1: Ship Equivalents
Ship Type Combat Fuel Cargo Warship
TP Cost Weapon Total SC Cost Ratio
Transport 1D 10 50 0 (10) 0 (10) 1 10
Tanker 1D 50 0 0 22 0 22 (1) --
Scout 1D 20 0 1000 32 0 32 3 11
Corvette 3 20 20 1000 58 20 78 8 10
Missile Base 3 0 20 0 25 20 45 4 11
Fighter 8 20 40 1000 154 40 194 20 10
Advanced MB 8 0 40 0 66 40 106 10 11
Deathstar 12 15 50 1000 333 50 383 40 10
The "warship engine" is that which allows the warships the "overload" maneuver, unavailable to commercial ships.

Diplomacy and Inter-Player Relations

The original Stellar Conquest, especially the Metagaming version, was set up so as to preclude diplomacy as much as possible. The present game is wide-open for diplomacy, back-stabbing, and the like.

Players may buy and sell things among themselves, subject to some limitations. A player cannot sell his own colony, but conquered colonies may be sold. For sale to take place, the selling player must take the item to a planet or a ship of the buying player, and the buying player must take the money to a planet or ship of the selling player. The referee is then notified of the sale, and it takes place.

Players may buy and sell intangibles (promises, co-operation, peace, undying amity), subject to almost no limitations. The buying player must get his money to a ship or planet of the selling player, and notify the referee of the transaction.

Players may buy and sell technological know-how (see also Stellar Conquest rules) for whatever prices they can agree on. The seller must have the technology he is selling, and the buyer must get the money to him. A level of technology that has been bought in this way may be used and sold, but it cannot serve as a predecessor technology for the purposes of later research on the part of the buyer.

WARNING: Experience has shown that some players, upon exposure to a referee, instantly snap into D & D mode, i.e. they skip all the rules and assume that they can do whatever they can weedle the referee into lettng them do. This game is not D & D: it is Stellar Conquest with Triplanetary used to resolve the combats.

Section-by-Section Rules Details Pertaining to Stellar Conquest

Mapboard: The board used in this game is the Avalon Hill Stellar Conquest board.

Star Cards: The star card deck will be used by the referee to determine the contents of star systems. At last, the orbit information on the cards will be useful!

Stellar Conquest orbits translate roughly into Triplanetary orbital radii as follows:

Stellar Conquest
Orbit Number
Orbit Radius (in hexes)
1 4
2 8
3 13
4 20
5 36

Terran planets will generally have a large moon. A system with a terran planet will generally have a gas giant in Orbit 5 or farther out. Unfilled orbits bounded by filled orbits will contain asteroid belts.

Spaceship Counters and Markers: Unchanged, except that tanker counters have been added. The original Stellar Conquest countermix constrains players' builds. One cannot have more than the 15 task forces and the 7 Command Posts provided to each player in the countermix. No task force may contain more warships than are in the original countermix. Players designing their own ships (using the Flexible Ship Design technology) are responsible for making their own counters for the new ships and may do so without limit. A task force may contain unlimited tankers and transports. Players may avail themselves of each other's command posts provided that they have permission and that one player has a command post within eight hexes of one of the other player's command posts.

Player Record Sheet: Unchanged. Players will submit to the referee a photocopy of their Player Record Sheet each turn.

Task Force Card: Unchanged. Each turn, players will submit to the referee a listing of task forces, their contents, and their destinations.

How to Win: Unchanged. In later games, a choose-your-own mix of victory conditions like that in Reach for the Stars may be used.

Setting Up the Game: The referee will set up the game.

Preparing for Play: Unchanged.

Sequence of Play: Unchanged.

Spaceship Movement: Unchanged.

First Turn Entry: Unlike in original Stellar Conquest, players choose their own first turn entry locations. Each entry location must be on an edge of the mapboard, but it needn't be at a corner. Mark your entry hex clearly. Each player may have only one entry hex.

Gas/Dust Clouds: Unchanged.

Command Posts: Command Posts will be used, even though we will be using Hidden Movement, because of their additional role in this game as Triplanetary refueling stops: command posts can refuel ships. The fuel must be bought on the planet inhabited by the command post (see production) or brought to the command post by tanker. Command posts cannot be voluntarily destroyed during a Triplanetary battle. When a command post is captured, the captor can avail himself of any fuel stored there, but the not Stellar Conquest capabilities of the command post.

Ship Communications: This rule will be used. Players will inform the referee of their task forces' destinations.

Spaceship Interaction: The original version of this rule provides for instant combat to the death whenever different players' ships meet at a star, precluding coalition warfare. In this game, combat is voluntary, and deals can be made (and broken) at any time. (Ideally, players would not be allowed to communicate when they do not have ships in the same system, but this rule is impossible to enforce in a play-by-mail game.)

Task Forces: Unchanged.

Hidden Forces: This optional rule will be used.

Exploration: Unchanged.

Combat, Colony Attack and Conquest, and Besieged Colonies: The combat rules are replaced by the use of Triplanetary to resolve combat. There is no distinction between ship-vs.-ship combat and ship-vs.-planetary defenses combat: they both happen during the Triplanetary battles. The way in which ships enter the combat hex is described below, in the section on changes to Triplanetary.

To beseige a colony, a player must have a surviving, unopposed, armed ship orbiting the colony world on the Triplanetary board.

Conquered Colonies: Unchanged, except for the rules on attacking population, which should be with the combat rules anyway. Population and industry can be attacked during Triplanetary combat and have, in Triplanetary terms, has a defense factor of 3. The attacker rolls on the Combat Odds table and destroys 1 million population OR 1 industrial point on any D or E result. Nukes can be used against planetary targets as well: a nuke hit destroys one sixth of the planet's population AND one-sixth of its industry, stored fuel, and money.

Colonizing Planets: Unchanged.

Colony Transports: Changed. Transports are, when built, designated either as colony transports or reqular transports. Note that colony transports disappear after use, because the colony cannibalizes them upon landing. Tranports not constructed for colonization (for example, to carry spare torpedoes) do not disappear after use. The two kinds of transport do not cost the same. Tankers and transports that are not colony transports cost 2 i.p. to build, not 1. (Colony transports still cost 1, presumably because the colonists contribute their own labor to the construction.) An existing non-colony transport (bought to carry weapons), may be used at no additional cost as colony transport if desired. However, it will, like any colony transport, be consumed upon disembarkation (and the owner does not get a rebate of 1 i.p. from the colonists for having given them a transport that cost 2 i.p. when they could have constructed one for 1 i.p.!) The purpose of this rule is to allow a cash-strapped player to get his starving millions into space for free. As in Triplanetary, non-colony transports can drop mines and nukes: colony transports cannot.

Production Turn: Unchanged, except that i.p.'s can be saved at their planet of origin or transported by ship to other planets. The production rule contains a rare hint as to the scale of Stellar Conquest, implying as it does that four turns are a quarter. However, a check of the original Metagaming rules makes it quite clear that each turn is a quarter, so that after each 90 turns of Triplanetary (in the unlikely event that in-system combat takes that long), there ensues a turn of Stellar Conquest.

Population Growth: Unchanged.

Industrial Output: Unchanged.

Emigration: Unchanged.

Industrial Expenditure: Elaborated. Ships and planetary defenses are bought at the prices shown in Table 1. A free load of mines and torpedoes comes with each newly-constructed warship or missile base capable of carrying them. (Not with each transport!) Keep track of each ship and its weapons load. Reloads must be bought and paid for. Weapons and fuel are bought at the Triplanetary prices, keeping in mind that one Stellar Conquest i.p. is worth ten Triplanetary megacredits. Fuel is consumed only during Triplanetary battles, not during Stellar Conquest interstellar travel. One full load of fuel is included in the price of new ships, except that tankers and transports do not come with a free full load of fuel. They come with 10 fuel points.

Technology: Elaborated. "Improved ship weaponry" consists -- in Triplanetary terms -- of nukes, of torpedoes that can make an additional acceleration (normal or overload) in any of the launching player's turns after the original launch, and of mines that can make an acceleration (normal or overload) in any of the launching player's turns after the original launch. "Unlimited ship range" confers the ability to build ships as Triplanetary torch ships. These ships also have "unlimited ship range" in the Stellar Conquest sense. However, acquisition of the unlimited ship range step does not--as it apparently does in original Stellar Conquest--retroactively confer unlimited ship range on existing ships. It only applies to ships built after the new technology was acquired. An additional 3rd-level Weapons Research item, Flexible Ship Design, allows players to design their own ships as described in the Appendix. It costs 130, and replaces the Planetary Shield, which is NOT AVAILABLE in this game. A new Research track, Sensor Research, is added as shown in Table 2. Improved Ship Weaponry technology immediately spreads throughout the fleet. Unlimited Ship Range applies only to ships built after its introduction, and the sensors created on the Sensor Research track must be bought and put in place for 2 i.p per sensor. They consume no space aboard the ships carrying them, but a ship can be retrofitted with a sensor only at a friendly planet.

Table 2: Sensor Research
Level Title Development Cost w/ Pred. Normal Cost
1 Planetary Radar Identifies ship types within 15 Triplanetary hexes of any occupied planet or command post. - 10
1 Neutrino Spectroscopy Shows color of last star visited by a captured ship or wreck. - 10
2 Shipborne Radar Identifies ship types within 15 Triplanetary hexes of any ship, occupied planet or command post. Sees planetary installations from within 15 hexes. 10 w/ Planetary
2 Neutrino Chromatography Identifies last star visited by a captured ship or wreck. 10 w/Neutrino Spectroscopy 25
3 Lasar Radar Detects exact ship contents within 15 Triplanetary hexes of any ship, occupied planet or command post. 40 75
3 Tachyon Chromatography Identifies approaching ships and tells how many SC turns until they arrive 70w/Neutrino Chromatography 100

As in the case of the other technology tracks, acquisition of a level of Sensor Technology does not provide the sensor items, only the ability to build them. Once the technology is acquired, individual sensors can be built for 2 i.p. each. When resolving combat with Stellar Conquest rules, the effects of lack of radar will be simulated by the use of inverted ship counters.

Optional Victory Scenarios: We will play a 44-turn game, nominally taking a year to do so.

Section-by-Section Rules Details Pertaining to Triplanetary

Game Components: Instead of the original Triplanetary mapboard showing the Earth's solar system, special mapboards will be used for each different system encountered in the Stellar Conquest part of the game. These will be provided by the referee. The Stellar Conquest ship counters will be used in Triplanetary combat.

Sequence of Play: Unchanged.

Movement: Clarified. The description of gravity's effect on movement in second-edition Triplanetary rules is less well-worded than that in the first, which says that a gravity hex "affects any ship passing [through] it on the Turn after the Turn the ship entered that hex. The second edition does not specify how disabled ships interact with hollow gravity arrows. In this game, they are affected by every other hollow arrow, starting with the second that they encounter.

Combat: Unchanged, except that for greater realism, i.e. more fun, nukes, mines and torpedos persist forever, not just for five turns.

Astrogation Hazards: Unchanged. In general, habitable worlds will, at the discretion of the referee, have at least one large moon. Asteroid belts are relatively common. Novel astrogation hazards, such as gravitational anomalies, may be encountered from time to time.

Bases: Missile bases and advanced missile bases orbit the planets they planets--they are constructed in orbit and have no engines or fuel. Command posts act as sources of fuel. Hostile ships making landfall at a command post may expropriate the fuel. The command post may not self-destruct, but it and its fuel are considered to have a defensive value of 1 when targeted by Triplanetary gunfire.

Special Rules: These are all used, with the following exceptions. The Detectors rule is expanded upon by the new Sensors Research track. Even without the shipborne radar, the industry and population of a planet can be detected by a ship that completes one orbit. The Heroism rule applies, except that a ship CAN "become heroic more than once," simply adding +1 to its gun combat die rolls for each level of heroism. (This is the Luke Skywalker Rule.)

Prices: Ships are bought and paid for in terms of Stellar Conquest money and prices. Weapons are bought at Triplanetary prices. Again, one Triplanetary Megacredit equals one 10th of a Stellar Conquest industrial point.

Scenarios: These are, of course, replaced by the scenarios generated in the course of playing Stellar Conquest when a player's ships enter a system occupied by another player. This player is termed the Attacker, and the player(s) with ships in the system will be termed the Defender. The Defenders, after seeing the mapboard as created by the referee, write down the locations of their ships. These must be on planets or moons, in orbit, or stationary in space. They cannot be moving in space. The Attacker then draws a reference fleet velocity vector on the map, showing the velocity his ships will have upon leaving hyperspace (i.e., Stellar Conquest) movement and places his ships. Each ship's position is then scattered TWICE in the customary manner: one six-sided die is rolled to determine the direction of the first scatter and another to determine the distance, and then two more dice are rolled to determine the direction and distance of the second scatter. These scattered positions are the initial positions of the ships: their initial velocity is the fleet velocity vector drawn as described above. Ships scattered into planets, suns, moons, or asteroids are destroyed. Ships scattered into asteroid hexes must make the usual Triplanetary disablement roll if they are travelling at a speed greater than one hex per turn. Ships scattered off the map are considered to be disabled unless and until they coast onto the map. They will not participate in the Triplantary combat (though they survive in Stellar Conquest terms) UNLESS the fleet's velocity vector is such that it will bring them onto the map. Triplanetary play then begins, with the Defender having the first move.

Appendix: The Theory and Practice of Triplanetary Ship Design

Triplanetary ship prices can be rationalized as the weighted sum of the following: a weapons pod, the outer hull, and paperwork. The weapons pod and the outer hull are both shielded by the ships armor, represented by its defensive combat strength.

The cost of the weapons pod is the 1/130th of product of the defensive strength, the cube of the offensive strength.

The cost of the hull is the 4/33rds of the product of the defensive strength, the surface area of the hull: the surface area of the hull is the 2/3rds power of the sum 20 + fuel capacity + cargo capacity + 1000 (if a warship engine engine is present).

The paperwork costs 20, regardless of the size of the ship.

As shown in the table below, ship costs computed according to these formulas closely approximate those given in Table 1 of the rules, with the exception of the transport ship and the liner. The extra cost of the liner is presumably accounted for by the posh accomodations made available for the pleasure of the pampered passengers. The high cost of the transport is ignored: letting it cost 10 as stated in the Triplanetary rules brings it back into line with the 1:10 exchange rate between Stellar Conquest and Triplanetary prices.

Table 3: Ship Calculations
Ships Attack Defense Fuel Cargo Engine Cost
Transport 0 1 10 50 0 10 22
Liner 0 2 10 50 0 50 25
Corvette 2 2 20 20 1000 40 45
Coursair 4 4 20 20 1000 80 72
Frigate 8 8 20 40 1000 150 154
Dreadnaught 15 15 15 50 1000 600 601

Brian McCue can be reached at