Jumpship (BattleTech)

In the Battletech universe, the term Jumpship refers to a ship capable of interstellar travel, but which lacks the large thrusters necessary for travel within a star system. General construction consists of a bulbous bridge and living quarters section at the front, a spinal section housing dropship docking rings and a capacitor bank, and the engineering section, which houses the Kearny-Fuchida FTL drive (KF Drive) and the fusion engine. In order to generate the enormous amount of power the K-F drive needs to execute an FTL jump, the jumpship deploys a thin metallic solar array, known as a "jump sail." The jump sail is only about a milimeter thick, but can have a diameter of several kilometers. During a jump, the sail is retracted and stored in the engineering section. The crew section usually has at least one spinning centrifuge used to create artificial gravity, referred to as a "gravity deck" or "grav deck" for short. Larger jumpships also sometimes carry hydroponic gardens in domes attached to the crew section.

Operation
The K-F drive's maximum jump range is approximately 30 light years. Generally, jumpships arrive in a solar system at either its zenith or nadir points, a point at the very edge of a star's gravational influence, directly above one of the star's two poles. A skilled navigator can also enter a system at a "pirate point", much closer to the system's planets. Due to the complexity of calculating pirate points, this can be a dangerous procedure, but one which offers an invading fleet a greater chance to catch a system's defenders by surprise.

Because they only carry station-keeping drives, jumpships rely on dropships to ferry cargo between the jumpship and planets within a system. The number of dropship docking rings a jumpship has varies from one to nine, depending on the size of the jumpship. Depending on the size of a system, the time needed for a trip from a the zenith or nadir jump point to the system's habitable zone can be anywhere from a few days to a month.

Typically, during this "turn-around" time, a jumpship will deploy its jump sail to recharge its K-F drive using the local system's star. Some more advanced jumpships carry lithium-fusion batteries which can store an extra charge for the K-F drive, allowing a jumpship to either make a round-trip between two systems without recharging or make two FTL jumps in rapid succession, effectively extending the ship's range to 60 light years. Unfortunately, recharging the lithium fusion battery doubles the amount of recharge time a jumpship requires, limiting its flexibility somewhat.

Scarcity
The Succession Wars created a shortage of jumpships in the Inner Sphere, directly threatening the backbone of interstellar transportation. During the 1st and 2nd Succession Wars, most of the orbital construction facilities used to build jumpships were destroyed, and the fragile, slow, poorly armored jumpships were vulnerable targets.

Because of the difficulty of constructing new jumpships to destroy those lost in combat, and the important role they play in holding interstellar civilization together, the powers of the Inner Sphere came to regard Jumpships as lostech as the Succession Wars dragged on. This meant that they were protected by the code of combat which gradually arose to protect the Inner Sphere's fragile technology base, and generally regarded as off limits during combat. This protection has some limits. While destruction of a jumpship in combat is frowned upon, boarding actions and weapons fire directed at the solar sail with the intention of immobilizing a jumpship is permitted under the rules of warfare in the Inner Sphere in the 31st century.