SpaDeX: approach, dock, separate and share power

SpaDeX, the Space Docking Experiment, used two small spacecraft launched by PSLV-C60 on December 30, 2024. The archive identifies them as SPADEX-A and SPADEX-B; mission descriptions also use SDX-01 and SDX-02. The objective was to demonstrate rendezvous, docking, undocking and associated technologies through a dedicated orbital experiment.

Approaching another spacecraft requires information about relative position and velocity, as well as control of orientation and motion. Sharing a broad orbital region does not mean two vehicles can simply point at each other and connect. Sensors, communications, propulsion, guidance software and the mechanical docking interface — open definition must work together under the conditions of the encounter.

ISRO reported the first docking on January 16, 2025. The spacecraft subsequently undocked on March 13, allowing them to operate separately again. Docking and undocking are related operations, but a successful connection does not automatically demonstrate that the connection can be released in the required sequence. Each operation supplies its own evidence.

A second docking occurred on April 20, followed by power-transfer tests on April 21. In that experiment, one spacecraft powered a heater on the other, and transfer was exercised in both directions. The report describes approximately four minutes of power transfer. That bounded result should not become a claim of indefinite operation or of transferring every possible resource between spacecraft.

SpaDeX: separate the milestones

The second approach used autonomy from a separation of 15 meters through docking, while the first included an additional manually exercised hold at three meters. This illustrates how ground review, simulation and flight experience can support a changed procedure. It does not mean people disappeared from mission planning, monitoring or the validation of the autonomous system.

For a fictional future assembly mission, list which SpaDeX results are relevant and what must be qualified again for different mass, geometry, interfaces and environment. A small-satellite demonstration contributes valuable knowledge, while docking a crew vehicle or operating far from Earth can impose different requirements. Keep the demonstrated capability, its conditions and the proposed next application as separate entries in the engineering argument.