The base is a kind of craft installed on the surface of a celestial body, and most cases cannot move independently. A smaller one can be taken to orbit as a whole with a single launch vehicle, and deliver to he surface with a special lander, but the bigger ones built by docking different modules together. The difficulties of the delivery and the construction give a real challenge for the experienced players.
The bases can work as fuel depot/refinery or a science station. As a fuel depot helps to refuel the landers for returning to orbit, and planes for the next mission. A special base can have a much greater capacity than a mobile craft, but the refueling usually more practical at a space station, as those orbital craft easier to reach and resupply. These bases can be profitable only using the rovers, planes and landers extensively - and connected exploitation of the raw materials (for example ore), and conversion of the collected materials.
Beyond the fuel, Kerbals also can be stored in bases. The PPD-10 Hitchhiker Storage Container is especially useful for this purpose, as it can hold four Kerbals and its ladders are arranged to stack on top of each other. The PPD-12 Cupola Module is meant to be incorporated into stations, both because it is unsuitable for most other mission profiles and because it deliberately is an iconic component. The kerbonauts do not require any consumable resources and may be left alone indefinitely.
Bases can also be used for scientific measuring using the various sensors. However, it can be more efficient to perform these tasks with smaller and more maneuverable probes and rovers. One can also use the Mobile Processing Lab MPL-LG-2 on a space station to convert the results of experiments to science points (⚛) and clean the Mystery Goo™ Containment Unit and SC-9001 Science Jr.. Multiple science labs can be docked at a station. Duplicate experiments will be assigned to the first lab which will accept them. So touring labs can dock at a station, use up all the experiments, then travel to the next station.
Design and construction
A simple base may be launched as a single unit, and will differ from other craft only in minor ways. The most significant of these is a lack of propulsion. While bases may possess wheels for basic mobility, and remaining landing legs, they typically lack rocket engines. Other than that, a base may possess electrical systems, one or more command modules, environmental sensors, electric lights, or any other structure.
A modular base composed of multiple components generally requires surface-side construction to dock the components together. There are three known methods to achieve this:
- Crawler Rover - each base component is equipped with a bottom facing docking port, a very flat rover with a matching upward facing docking port is then driven under the component so that the base component docks to the rover. The component's landing legs are then retracted and the crawler is then free to move the base component
- Crane Rover - a large rover with a long arm with downward facing docking mechanism can dock to base components from above. The crane arm is usually quipped with a fuel tank to act as a counterweight. Once docking is complete a suitable amount of fuel is pumped into the crane arm counterweight and the base component can then retract its landing legs and be moved around by the rover
- Skycrane - for base components that are stacked vertically a skycrane might be used to dock with the component from above. The skycrane then lifts the component by firing its engines and maneuver the component above another existing base component to stack the two vertically
In order for a base to act as a fuel depot or refinery, it must be equipped with clamps for docking. A base will often have several clamps of different sizes on it, to accommodate multiple visiting craft or craft of different designs. Generous space should be allowed around the clamp for visitors - mainly the rovers - to maneuver without colliding with other parts of the base. For converting the collected raw materials like ore, installation of an Converter also neccessary.
An incrementally constructed base has no practical limit to its size; it may contain as many components as the designer cares to launch. The only cap on extremely large bases is the number of parts they contain, as eventually the user's computer will be unable to simulate the station's physics in real time. Hitting this limit can be staved off by careful choice of the contents of each station module. Module complexity can be decreased by leaving out not essential systems, and using the parts of greatest capacity.
Most bases include more than one module. A complete space station usually has: A science module, a crew module, a communications module, an electricity module (a module that has batteries and solar arrays, generators, etc. ), and converter module with fuel tanks.