In the broadest sense, a Docking Collar is a standardized structure that can be used for docking in space, i.e. to connect to the Docking Collar of another spaceship or space station, allowing for the transfer of data, power, supplies, cargo and passengers between the vessels involved.
Beyond this defining function, the concept of a Docking Collar in the BattleTech universe includes Kearny-Fuchida field conducting (KFFC) capabilities which enable a DropShip to safely attach itself to a JumpShip Hardpoint so that the JumpShip can move both of them to another star system by means of its Kearny-Fuchida FTL jump drive. Invented in ca. 2470, coupling DropShips to a JumpShip in this way has become the almost exclusive method of FTL travel over cargo or equipment carried directly by the JumpShip.
A regular Docking Collar costs 10,000 C-Bills in construction. It does not require extra mass to be allocated during construction, being an integral part of every DropShip's structure.
Docking Collars on JumpShips are called (Docking) Hardpoints or JumpShip (Docking) Collars. They differ from regular Docking Collars in that they include Kearny-Fuchida field conducting (KFFC-)booms and other special equipment to ensure that the JumpShip's jump field completely extends to and encompasses all docked ships, something that is not necessary on other ships. JumpShips typically have several Hardpoints, enabling them to jump with several DropShips (up to 9 on the civilian Monolith class and up to 25 on the Potemkin class troop cruiser).
Hardpoints have a base cost of 100,000 C-Bills and have a mass of 1,000 tons each, and also dramatically increase the cost of the Kearny-Fuchida drive core to which they belong.
The construction rules assume that all DropShips automatically have at least one Docking Collar because they need to dock with JumpShips for interstellar travel; accordingly, no mass is indicated for DropShip Collars.
According to the BattleSpace construction rules, DropShips massing over 60,000 tons required a second Hardpoint on JumpShips, which means they could not be carried by JumpShips with only one Hardpoint. This ruling has been abandoned in newer rulebooks that take precedence over Battlespace.
A JumpShip with a standard K-F core can have one Hardpoint for every 50,000 tons of ship mass (95% of which is taken by the drive core), or fraction thereof.
- Mercenaries Supplemental II, p. 85