Orbital
An orbital weapon is cumbersome yet powerful, designed to devastate immense targets or bombard planetary surfaces. During starship combat, attacks using an orbital weapon take a –4 penalty to the gunnery check if the target is a Medium or smaller vessel, or a –2 penalty if it’s a Large, Huge, or Gargantuan vessel.
A gunner can also fire an orbital weapon at a large, stationary target, such as a settlement or battlefield. The effects follow the guidelines below. These guidelines are somewhat flexible so as to limit the degree to which a PC’s starship might obliterate a key site or to allow an NPC starship’s strike to deal the necessary structural damage without outright annihilating the PCs.
Orbital attacks have an immense range: orbital weapons with short range can strike large targets from low orbit (approximately 1,000 miles for a Golarion-sized planet), medium range orbital weapons are effective from high orbit (approximately 20,000 miles), and long-range orbital weapons can strike from extraordinary ranges of 100,000 miles or more. When an orbital weapon strikes an area, it damages everything in a 100-foot radius for a light weapon, 500-foot radius for a heavy weapon, 2,500-foot radius for a capital weapon, or a mile radius or larger for a spinal-mount weapon. Orbital weapons rarely fire faster than once every 10 minutes during bombardments, and spinal-mount weapons can rarely fire more than once per hour.
Orbital weapons deal 10 × their listed damage to inanimate objects in the affected area, damaging or outright destroying many structures. Against vehicles, living creatures, and other smaller targets in the affected area, an orbital weapon’s damage, effects, and other statistics are best approximated using the trap creation guidelines for a trap with a CR equal to the value listed with the weapon’s orbital special property.
Orbital weapons require additional features to function properly on most ships. Any starship modified by the colony ship framework or space station framework is sufficiently fortified to mount orbital weapons without needing such extra features, reducing an orbital weapon’s BP cost by one-third.
Source
Starship Operations Manual pg. 15