India’s ambitious space missions in the years ahead include the Chandrayaan-4 lunar sample-return mission, officially scheduled for launch in 2028. Beyond that are India’s maiden space station, expected to be operational by 2035, and the goal of sending its first astronauts to the Moon by 2040. However, such ventures need crucial support technologies to be successfully tested beforehand. One of the most crucial is docking spacecraft modules in orbit, without which these missions cannot be accomplished.
The Indian Space Research Organisation did well by scheduling the space docking experiment, or SpaDeX, in January 2025. But almost two years later, there is no word from the organisation on scheduling SpaDeX-2 to test docking requirements in an elliptical orbit, as required for Chandrayaan-4, and SpaDeX-3 for space station assembly operations. Experimental docking missions are considered crucial for sample-return missions from celestial bodies, operating a space station without hiccups, and safely sending humans to and from the Moon.
The January 2025 SpaDeX mission involved the autonomous docking of two small spacecraft models, each weighing 220 kg and measuring only a metre in length and half a metre in width, with dual solar panels about 2.5 metres long. These were far smaller than the actual spacecraft modules that would need to dock in orbit. Even in that mission, progress was not smooth, as delays occurred because the complex autonomous procedure required algorithms and calibration steps to be completed before the final docking could be accomplished.
Chandrayaan-4 aims to land near the lunar south pole, collect up to 3 kg of soil and rocks, and return with the samples to Earth. It will involve five modules assembled in lunar orbit using at least two LVM3 heavy-lift rocket launches, and will have to demonstrate lift-off from the lunar surface, orbital docking and re-entry into Earth’s atmosphere. Even more challenging would be assembling the 27-metre-long, 20-metre-wide Bharatiya Antariksh Station in space. Its five components, each weighing about 10 tonnes, would need to be assembled in orbit for the station to become operational by 2035. All these manoeuvres require accurate docking and undocking capabilities.
Currently, SpaDeX-2 and SpaDeX-3 are ‘under study’. But time is running out to master these complex capabilities, and delays could have a telling effect on mission costs and the schedule of India’s space programme.
