ISRO advances space tech with SPADEX undocking and cryogenic engine milestone

ISRO advances space tech with SPADEX undocking and cryogenic engine milestone
by Simon Mansfield
Sydney, Australia (SPX) Mar 17, 2025

India's space program marked a significant stride forward in March 2025 with a trio of successful operations that underscore the growing sophistication and efficiency of the Indian Space Research Organisation (ISRO). From a milestone in-orbit maneuver involving its SPADEX satellite duo to innovations in cryogenic engine testing, ISRO's achievements reflect a focused drive to advance indigenous capabilities in space technology.

On March 13, 2025, ISRO completed the critical task of undocking the SPADEX satellites in their first attempt, a maneuver executed in a 460 km circular orbit at a 45-degree inclination. The satellites, which had been docked since January 16, 2025, are now functioning independently, with all systems reported to be in good health. This undocking marks the culmination of a mission designed to demonstrate key spacefaring abilities: rendezvous, docking, and separation of satellites in orbit.

The success of the undocking operation was enabled by exhaustive ground simulations and tests that mimicked real on-orbit conditions. These preparations allowed ISRO to capitalize on a viable operational window between March 10 and March 25, 2025. Ground stations in Bengaluru, Lucknow, and Mauritius provided critical support throughout the process. The agency now plans to conduct additional experiments using the separated satellites.

"ISRO has now successfully demonstrated space docking technology using two small satellites. It is a cost-effective experiment through which, India has achieved space rendezvous, docking and post docking control technologies," ISRO stated. This accomplishment not only enhances India's technological portfolio but also positions the nation for future complex missions, including potential human spaceflight and on-orbit satellite servicing.

In another significant development, ISRO completed the flight acceptance hot test of its CE20 cryogenic engine on March 14, 2025, intended for the sixth mission of its LVM3 launch vehicle, known as LVM3-M6. Conducted at the ISRO Propulsion Complex in Mahendragiri, the test ran for 100 seconds, surpassing previous hot test durations limited to 25 seconds under vacuum conditions. The extended test was made possible by deploying a new Nozzle Protection System, which allows testing under non-vacuum conditions and accelerates engine readiness for missions.

The CE20 engine's performance closely aligned with predictions throughout the test duration, meeting all objectives. This engine is slated to power the Cryogenic Upper Stage of LVM3-M6, a mission scheduled for the latter half of 2025.

Adding to this momentum, on March 15, 2025, ISRO dispatched the Cryogenic Upper Stage (C25) destined for the LVM3-M5 mission to its launch site in Sriharikota. The stage, integrated at Mahendragiri and powered by the CE20 engine with a 28.5-tonne propellant capacity, will support a commercial satellite launch for AST and Science, LLC under a deal with NSIL. This stage exemplifies the ongoing maturation of India's commercial space capabilities, as the nation increasingly engages in global launch services.

Together, these milestones illustrate ISRO's commitment to innovation, self-reliance, and commercial expansion in space technology, reinforcing India's status as a key player in the global space community.