In this game, the two players represent two groups of Catanians who wish to return home to the Catan star system after getting lost through a wormhole.
Like Starfarers, there are five basic resources in the game -- ore, wheat, fuel, trade goods, and Carbon.
Each player is also given 25 Astro, the local currency, from the Scientists, another alien race.
At the start of the game, each player begins with two trade goods and one science point.
At the start of each turn, the player to move rolls a single die, and, like Settlers or Starfarers, any colony planet with a production number matching the number shown on the die produces a single resource of the card's specified type.
During this phase, players may elect to explore (or fly to) any one of four different sectors, each being represented by ten cards.
Once a sector is selected, the combined levels of the boosters on the starship is added to the roll from the production die to determine the maximum number of cards that may be explored.
There are a number of possibilities as to what may be explored: There are four Adventure Planets in the four sectors, named Pallas, Hades, Picasso, and Poseidon.
These allow the player to undertake missions and receive rewards for their completion.
Each mission states the planet that the player must encounter, as well as any other additional requirements.
If the requirements are met (and if it consists of Astro or resources, paid as a cost), then the mission is completed.
Colonies allow a player to produce resources on a specific roll of the dice during the production phase.
However, if the player instead chooses to fight, the player rolls a blue combat die, and adds its value to the combined levels of the player's cannons to form its combat value, while the opponent rolls the blue die and adds its value to the value printed on the pirate card (which may be anywhere between 2 and 7) to determine the pirates' combat value.
If the pirates' strength is strictly greater, the flight immediately ends, and boosters, cannons, or modules may be lost as a result.
If the player wins by having an equal or greater combat strength, however, the pirate is removed from the sector, and as a reward the player may select any single resource of their choice as well as a Fame Point.
A player may also choose to build a trading post on any planet where three Astro are exchanged for the resource.
The two players may also trade resources, science points, and Astro on any agreeable terms.
A Victory Point is awarded for each colony and Level II module, as well as from certain missions (Monument and Plague).
In addition, there are two special victory points that may be obtained, akin to the Largest Army and Longest Trade Route from Settlers: A simpler, one-player version of Starship Catan can be played online after registration (which is free) on Playcatan.
If a fourth booster or cannon is bought, two of them become level II boosters/cannons and the third disappears; it is impossible to buy more than five of either.
(Of course, like in the two-player version, the stack through which the player has flown is mixed after each turn).