India Launches SpaDex Mission Successfully—A Key Mile Stone For Future Bharatiya Antariksha Station, Chandrayan-4 & Space Flights

December 30, 2024 will be marked a historic day in Indian space research as Indian space agency ISRO launched its first ever SpaDex Mission successfully from Satish Dhawan Space Centre SHAR Sri Harikota, Andhra Pradesh. With this launch India in subsequent days may join an elite club of USA, Russia, China, European Union and Japan, who have proven technology of space docking. Success of India’s SpaDex mission will be leveraged in future space assignments like having India’s own space station, Bharatiya Antariksha Station mission and Chandrayan -4 mission, which compulsorily require docking mechanism.

Shailesh Kumar, National Defence
New Delhi, 31 December 2024

Space docking is a highly advanced capability that involves the precise maneuvering and connection of spacecraft in orbit. According to ISRO scientists, two spacecraft will be separated in the circular orbit around Earth. They will be kept apart around 20 km in a circular orbit and gradually after a few days, they will be brought closer and closer… finally, both will be joined together…if we succeed in this experiment, India will become 6th nation in the world after Russia, China and USA, EU and Japan to successfully conduct space docking.

Russia (formerly the Soviet Union) was the first to perform a successful docking in 1966 with the Cosmos 186 and Cosmos 188 missions. It continues to use the Soyuz and Progress spacecraft for docking with the ISS.

NASA did docking in Apollo program and later with the Space Shuttle and International Space Station… Elon Musk’s SpaceX, also achieved autonomous docking with the ISS using its Crew Dragon spacecraft.

China achieved autonomous docking capabilities with its Tiangong space laboratories using the Shenzhou spacecraft. It has further developed this technology for its Tiangong space station.

European Union through the European Space Agency, the Automated Transfer Vehicle (ATV) demonstrated autonomous docking capabilities with the ISS.

Japan’s HTV (H-II Transfer Vehicle) is designed for resupply missions to the ISS. Although it relies on robotic arms for final capture, it also mastered advanced rendezvous technologies.

India is actively developing docking and rendezvous technologies for its Gaganyaan human spaceflight program and potential future space stations.

The SpaDex mission has Rendezvous: Approach each other in orbit with precision; Docking i.e. Physically connect in a controlled manner. Undock and Re-dock: Separate and reconnect multiple times. For the success of SPADEX, India had to develop core technologies like creating advanced sensors, propulsion system, control systems, and algorithms for autonomous docking.

This will lay the groundwork for India’s future space station, planned to be operational by the 2030s. The capability will enable India for refueling satellites and assembling structures in orbit. To conduct Space Docking, there are two kind of spacecraft used.

One is Chaser SDX01, which is the active spacecraft that performs the maneuvers to rendezvous and dock; and second one is target spacecraft SDX 02, which is the passive spacecraft that acts as the docking target.

During Proximity Operations, the chaser approaches the target spacecraft within a few meters. Autonomous docking is achieved Using sensors, cameras, and algorithms to achieve precise docking without human intervention.

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