Star clusters are huge collections of densly packed stars which can not be navigated by ships. Star clusters range in size, mass and temperature and have the following effects:
Ships that fly into or through a star cluster are destroyed.
Ships can not hyper jump through a star cluster. Ships which attempt to hyper jump through a star cluster will be destroyed.
Star clusters emit radiation which kills crew and colonists in starships. Ships which start in, or pass through a radiation halo will lose crew and colonists clans equal to the highest point of radiation passed through. The amount of radiation emitted is a function of the temperature of the star cluster and the distance to which it is emitted is a based on its mass.
A ship which runs out of crew due to radiation will become a "ghost ship" and can be captured by any ship which tows it. Its warp speed will be set to 0 and it will be unable to fight.
When capturing a ghost ship 10 crew members will be sent over to the other ship to capture it. If the ship is still inside the radiation halo those crew members may be killed. A ship must have at least 20 crew and two engines to capture a ghost ship.
Because of their glory devices most Fascist starship designs are equipped with radiation shielding. With radiation sheilding a ship will not lose crew or colonists when inside a radiation halo. The following ship hulls have radiation shielding:
D7a Painmaker Class Cruiser
Little Pest Class Escort
D7 Coldpain Class Cruiser
Ill Wind Class Battlecruiser
D3 Thorn Class Destroyer
Deth Specula Class Frigate
D19b Nefarious Class Destroyer
Saber Class Frigate
Victorious Class Battleship
Banshee Class Destroyer (Federation)
Moscow Class Star Escort (Evil Empire)
Armored Transport (Rebels)
The Robots are not affected by star cluster radiation.
Colonists and natives on planets inside a radiation halo are protected by the planet's atmosphere.
Special starbases must be built inside a radiation halo with radiation shielding and more docking space. These starbases cost slightly more minerals and megacredits to build. The heavy shielding automatically increases the starbase combat mass by 200kt and the extra space allows up to 250 defense posts and 80 fighters. If a friendly starbase exists on a planet (yours or an ally) then ships at that planet are protected from the radiation while at the planet (they are docked at the station). The Robots build normal bases.
Cloaked ships will only lose 1/2 the normal crew and colonists while cloaked advanced cloaking ships will only lose 1/3.
Normal minefield hits and glory devices hits to enemy ships which occur inside a radiation halo will kill crew equal to the radiation level at the point of impact due to the sudden large hull breach.
It is not possible to lay mines over a star cluster or within 10 ly of it. A minefield which is layed over a star cluster will automatically be reduced in size so that it does not come within 10 ly of the star cluster. Any additional mines will be lost (sucked in by the gravity well of the star cluster). It is possible to lay mines within the radiation halo.
Ion Storms which enter a radiation halo gain strength. Ion storms that touch a star cluster are immediately destroyed.
Ships can not be towed into a star cluster. The tow lock is lost as the towing ship enters the star cluster stopping both ships.