Separators are five parts that can be used to separate stages from one another vertically. The differences between the five are their size, mass and separation force.
Separators must be adjacent to anything connected to their underside or sides (which will also drop away with them). Their top side can be used in the same way (but detaching from everything connected on activation). Connecting can be connected to fuel tanks, separators, probes, capsules and capsules with space between them will create an interstage between the Separator and compatible part. This space has non-collidable fairings that can house parts aerodynamically, but won't prevent them from falling out.
When attaching to a part by this method, they have the same width adaptation range as fuel tanks have to each other, but 6-wide separators are the widest that can adapt to parachutes or two wide parts, not 8. 4-wide ones can connect to fuel tanks with up to 8 squares between them, 6-wide up to 9, 8-wide up to 10, 10-wide up to 11 and 12-wide up to 12.
It is usually placed between stages, usually with an engine on top and a fuel tank beneath. When the stage below runs out of fuel, it can be decoupled to decrease the remaining vehicle's mass. After detachment, the whole separator remains on the lower stage.
Side Separators can be used to separate SRBs, though vertical ones can be rotated 90º to fulfill the same function (less aerodynamically, but with more force, for instance to clear the boosters from colliding with lower protrusions).
- Rocket scientists know of separators as stack separators.
- The empty space between a separator and another stage is called an interstage.
- Usually you can replicate the game Space agency by putting 2 separators in rockets.