There are several kinds of maintenance drone. One is the PSMD (Pressurized Space Maintenance Drone), a flying trirotor robot (similar broadly in its configuration to the DCD but larger) for pressurized spaces. Another is the CSMD (Confined Space Maintenance Drone), a versatile telefactor using a pair of articulated "trunks" with modular tooling to perform maintenance tasks in physically restricted spaces. For use outside the ship and in unpressurized spaces, there are the VMD (Vacuum Maintenance Drone) and its heavier variant, the HMD (Heavy Multipurpose Drone). These latter two types move with resistojet thrusters.
Maintenance drones can perform a variety of simple maintenance and inspection tasks autonomously, and have the most complex behavioural repertoire of all common shipboard drones. However, they lack the flexibility of sentient beings, and are also the type of drone which most frequently requires manual (remote) control by technicians. They are equipped with a simplified programming interface with which they can be "taught" new tasks once they have been performed manually using the remote control interface. The drones can also assist humans in repairs, for example by automatically gathering parts and tools (within their weight limits if applicable) and bringing them to the job site.
Data from drone inspections is aggregated and fed into pattern-recognition computers to bring signs of trouble to human attention.