ISRO Successfully Conducts Hot Tests of Gaganyaan Propulsion System

On July 3, 2025, the Indian Space Research Organisation (ISRO) successfully carried out two hot tests of the Gaganyaan Service Module Propulsion System (SMPS) at its Propulsion Complex in Mahendragiri, Tamil Nadu. These tests mark a vital progression toward the realization of India’s first crewed space mission, the Gaganyaan Programme.

The tests were publicly disclosed by ISRO on July 8, highlighting the space agency’s technical preparedness and the operational integrity of the propulsion module.

What Is the Gaganyaan Service Module Propulsion System (SMPS)?

The Service Module Propulsion System (SMPS) is one of the core components of the Gaganyaan Orbital Module. It plays a crucial role in orbital maneuvers, trajectory corrections, and abort scenarios where crew safety is paramount.

Key Features of SMPS:

• 5 Liquid Apogee Motors (LAMs), each with 440 Newton (N) thrust.

• 16 Reaction Control System (RCS) thrusters, each delivering 100N thrust.

• Designed to operate in both steady-state and pulsed modes.

Details of the Hot Tests

ISRO conducted two hot tests on July 3:

• A 30-second short-duration test

• A 100-second extended test

These tests were performed to validate the SMPS test article configuration under conditions that closely mimic real flight scenarios. According to ISRO, all parameters performed normally, and the results matched pre-test predictions, confirming the robustness and reliability of the system.

Highlights of the 100-Second Test

The 100-second hot test was particularly significant. During this test, ISRO demonstrated:

• Simultaneous operation of all RCS thrusters in both steady-state and pulsed firing modes.

• Concurrent activation of all LAM engines, effectively simulating in-orbit maneuvering conditions.

This kind of integrated operation is vital to ensuring the system functions flawlessly under crew-carrying mission stress.

Technical Oversight and Development

The development of the SMPS is being spearheaded by ISRO’s Liquid Propulsion Systems Centre (LPSC). Over multiple stages of development and testing, the propulsion system has undergone incremental improvements based on insights from previous test cycles.

For this round of tests, the test article incorporated design refinements to more closely replicate actual flight conditions—a move that enhances the confidence level for full-duration qualification testing, which is expected shortly.

Why This Matters: The Gaganyaan Context

The Gaganyaan mission aims to demonstrate India’s capability to send humans into space and return them safely. It will be the first crewed spaceflight mission undertaken by India, targeting low Earth orbit (LEO) with an Indian crew onboard.

The SMPS is vital not just for keeping the spacecraft on course, but also for executing emergency abort sequences, if needed. A malfunction or delay in this system during flight could endanger the entire mission—making these successful hot tests a critical validation step.