ISRO-Roscosmos Discuss Semi-Cryogenic Engine Delivery for Heavy-Lift Launches

The annual report said ISRO officials visited Moscow for detailed technical talks, and a draft contract for the engines is currently under approval process.

The semi-cryogenic engine is a key technology for India's future heavy-lift launch vehicles. It uses a combination of refined kerosene and liquid oxygen, offering higher efficiency and thrust compared to existing systems.

The development and induction of such engines are expected to strengthen India's launch capabilities for heavier payloads and deep space missions.

The engagement with Russia comes as ISRO continues to expand its international partnerships in space technology and exploration. While India has been working on its own semi-cryogenic engine programme, collaboration with Roscosmos could help accelerate timelines and address critical technological gaps.

The Annual Report did not specify timelines for the finalisation of the contract or the delivery schedule of the engines. However, the ongoing approval process indicates that discussions have moved beyond initial stages.

ISRO, in a statement from March 28 last year, had said that it was "achieving progress in the design & development of a semicryogenic engine or Liquid Oxygen / Kerosene engine with a high thrust of 2000 kN that will power the semicryogenic booster stage of the LVM3 launch vehicle. The first major breakthrough in the semicryogenic engine development programme was achieved on March 28, 2025, when the first successful hot test of Engine Power Head Test Article (PHTA) was carried out at ISRO Propulsion Complex, Mahendragiri, Tamil Nadu."

The Liquid Propulsion Systems Centre (LPSC) of ISRO is developing the semi-cryogenic propulsion engine and stage. The SC120 stage, powered by the 2000 kN semi-cryogenic engine (SE2000), will replace the present core liquid stage (L110) of LVM3 for payload enhancement and will also power booster stages of future launch vehicles.

ISRO, in its statement had added, "Non toxic and non hazardous propellants (Liquid Oxygen and Kerosene) are employed in semi cryogenic propulsion and this will deliver higher performance compared to existing L110 stage. Induction of semi cryogenic propulsion system along with uprated cryogenic stage in the LVM3 vehicle enhances its payload capability from 4 tonne to 5 tonne in GTO."

"Major subsystems of SE-2000 engine include thrust chamber, pre-burner, turbo pump system, control components and start up system. The SE2000 engine works with a complex oxidizer rich staged combustion cycle with high chamber pressure of 180 bar (with propellant feed system delivering pressures up to 600 bar) & specific impulse of 335s," the agency said.

"The development of this engine in these high thrust levels is highly challenging and this technology is available with only very few nations," ISRO said.

The Moscow visit is part of a broader set of international engagements by ISRO in the past year. The report noted that the space agency has been in talks with multiple countries and agencies on areas such as human spaceflight, satellite navigation, earth observation and capacity building.

ISRO's cooperation with Russia also extends to planetary missions. The report highlighted that Russia's Space Research Institute has been selected as a partner payload provider for India's planned Venus Orbiter Mission, with technical discussions underway.

"The objectives of the Venus Orbiter Mission (VOM) encompass studying the Venusian atmosphere, ionosphere, surface, subsurface, and its interaction with the Sun. International collaboration efforts have been formalised, with approval granted for MoUs related to key international payloads. The Science Working Group (SWG) has been constituted to maximise the science returns from the payloads, and the Principal Scientist of the mission has also been declared. The Preliminary Design Review (PDR) of the mission has also been completed," the Annual Report said.

For the Venus Orbiter Mission, ISRO secured approvals in April 2025 to advance international collaboration, including initiating an MoU with Roscosmos for the Venus InfraRed Atmospheric gases Linker ( VIRAL) payload and formalising an MoU with the Swedish Institute of Space Physics for the VNA payload.

Further details are expected once the contract for the semi-cryogenic engines receives formal approval.

- ANI