In a significant milestone for India’s human spaceflight ambitions, the Indian Space Research Organisation (ISRO) has successfully conducted a series of critical hot-fire tests on the Gaganyaan Service Module Propulsion System (SMPS). These tests were conducted at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu, marking a major step towards the planned uncrewed and crewed Gaganyaan missions.
Overview of the Gaganyaan hot-fire tests
The tests, conducted over the last week, aimed to evaluate the integrated performance of the propulsion system that will be responsible for crucial orbit-raising, maneuvering, and de-boosting operations of the Gaganyaan module. ISRO officials confirmed that the SMPS, which comprises five main engines and sixteen Reaction Control System (RCS) thrusters, performed as expected under various mission scenarios.
| Key Test Details | Parameters |
|---|---|
| Test conducted by | ISRO Propulsion Complex (IPRC), Mahendragiri |
| Objective | Validate integrated performance of Service Module Propulsion System |
| Engines tested | 5 x 440N engines + 16 x 100N RCS thrusters |
| Duration of tests | Multiple hot-firings over integrated mission durations |
| Outcome | Successful performance validation for planned uncrewed and crewed missions |
Significance of SMPS hot-fire tests
The SMPS is the heart of the Service Module, which provides:
- Orbital maneuvering capability: For raising or adjusting orbits post-launch.
- Attitude control: For orienting the module during operations.
- De-boost capability: For safe re-entry and module separation.
The success of these hot-fire tests validates ISRO’s indigenous engineering in creating a reliable propulsion system that can meet human safety requirements.
Recent propulsion test timeline under Gaganyaan programme
| Month-Year | Test conducted | Location | Outcome |
|---|---|---|---|
| April 2024 | CE-20 engine long-duration hot test for LVM3 upper stage | IPRC Mahendragiri | Qualified for human rating |
| July 2024 | Integrated SMPS hot-fire (partial system) | IPRC Mahendragiri | Successful ignition and shutdown validation |
| March 2025 | Abort test propulsion system firing | SDSC SHAR | Cleared for emergency abort scenarios |
| July 2025 | Full-duration integrated SMPS hot-fire tests | IPRC Mahendragiri | Successful; clears milestone for uncrewed mission |
Gaganyaan mission roadmap ahead
With the propulsion tests cleared, ISRO will focus on final integration, astronaut training, and abort system validation before India’s maiden crewed spaceflight.
| Mission | Planned timeline | Purpose |
|---|---|---|
| TV-D1 (Test Vehicle Demonstration-1) | Completed October 2023 | Abort system and crew module re-entry test |
| Uncrewed Mission-1 | Late 2025 | Orbital qualification of systems without crew |
| Uncrewed Mission-2 | Mid 2026 | Advanced system validation with payloads |
| Crewed Gaganyaan Mission | Late 2026 or early 2027 | First Indian human spaceflight |
Role of Gaganyaan Service Module Propulsion System
The Service Module Propulsion System will ensure:
- Safe orbital insertion: After the crew module separates from the launch vehicle.
- Orbital adjustments: For maneuvering during mission operations.
- Controlled de-orbiting: Enabling re-entry at precise angles to ensure crew safety.
The system uses five 440 Newton engines for main propulsion and sixteen 100 Newton thrusters for reaction control, operating on a bipropellant combination of MMH (Mono Methyl Hydrazine) and MON-3 (Mixed Oxides of Nitrogen), tested and validated across ISRO’s prior PSLV and GSLV programmes.
Statements from ISRO leadership
Dr S Somanath, Chairman, ISRO, praised the propulsion and integration teams:
“Successful completion of these hot-fire tests is a critical achievement, showcasing India’s indigenous capabilities to build and validate a human-rated propulsion system. We are moving steadily towards realising the honourable Prime Minister’s vision of sending Indian astronauts from Indian soil using Indian technology.”
Technical insights into hot-fire testing
| Parameter | Details |
|---|---|
| Test type | Integrated hot-fire |
| Duration | Mission-specific burn durations covering orbital maneuvers and re-entry de-boost sequences |
| Chamber pressure stability | Within nominal parameters across engines |
| Thruster performance | Verified for attitude control, rapid ignition, and shutdown reliability |
Hot-fire testing involves firing the engine in a controlled ground test setup to simulate operational conditions in space, ensuring:
- Propellant flow consistency
- Combustion chamber integrity under mission loads
- Thermal and vibration endurance across the integrated propulsion bay
International relevance of Gaganyaan
India’s Gaganyaan mission positions it among the few nations with human spaceflight capability. ISRO’s achievements complement global space partnerships and establish indigenous expertise in:
- Human-rated launch vehicles (LVM3)
- Life support and crew safety systems
- Re-entry and recovery modules
- Orbital propulsion systems for human missions
This capability paves the way for India’s proposed space station plans in the 2030s and potential contributions to global lunar or Mars missions.
Industry and global reactions
A leading aerospace analyst stated:
“ISRO’s propulsion system hot-fire success validates the robustness of its engineering pipeline. As SpaceX and NASA prepare for Mars technologies, India’s Gaganyaan propels it into the critical group of human spaceflight capable nations.”
Future propulsion tests and system integration
ISRO will continue:
- End-to-end integrated module testing at IPRC and SDSC SHAR
- Crew module environmental control and life support (ECLSS) qualification
- Astronaut training for mission simulations in collaboration with Indian Air Force and Russian facilities
Conclusion
The successful hot-fire testing of the Gaganyaan Service Module Propulsion System is a historic milestone, reinforcing ISRO’s readiness to send Indian astronauts into space using indigenous technology. As the mission progresses towards uncrewed and crewed flights, these propulsion validations assure the safety, reliability, and performance excellence needed for human spaceflight.
Disclaimer
This article is prepared for readers of science, technology, and national affairs platforms. All technical and mission timelines are based on current official and industry inputs as of July 2025. For regulatory updates, final mission authorisations, or official statements, please refer to ISRO’s formal communications.
