undocking

Undocking is the deliberate separation of two spacecraft or vessels that have been connected through a docking interface or moored at a port. In spaceflight, undocking refers to the release of two orbiting spacecraft, such as a crewed vehicle and a space station module or a cargo freighter, after a period of linked operation. In maritime contexts, undocking describes the release of a vessel from a dock or berth after mooring.

In spaceflight, undocking requires a docking mechanism and an attitude and propulsion system on both vehicles. The process begins with checks, hatch closure, and isolation of the docking interface. The docking latches are released, and a controlled separation maneuver is executed using thrusters or a mechanical release. Initial separation is followed by reorientation away from the partner and a deliberate departure burn to set a safe distance and trajectory.

Procedural details vary by vehicle and mission. Some systems use automatic or semi-automatic undocking commands; others require crew input. After separation, the spacecraft perform collision avoidance maneuvers, adjust their orbit if needed, and communicate status to ground controllers. The partner vehicle may remain in a stable post-undocking configuration or prepare for a subsequent maneuver.

Safety and risk management are central to undocking operations. Sequencing must prevent premature recontact, and procedures address debris, propellant venting, and crew safety. Notable examples include International Space Station docking/undocking operations and historical missions such as Shuttle–Mir, which demonstrated the complexity of vehicle separation in a crowded orbital environment.