ISRO's CE20 Cryogenic Engine Passed Its Flight Acceptance Test at the Uprated 220 kN Thrust on 9 September 2026, Ahead of the LVM3-M7 Launch

ISRO fired a CE20 cryogenic engine at its uprated thrust of 220 kilonewtons (22 tonnes of force) on 9 September 2026 at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu, and its release of 10 September says the engine met all the test objectives. The test was a flight acceptance hot test of the engine identified for LVM3-M7, the seventh operational mission of India’s heaviest launch vehicle, which ISRO schedules for the fourth quarter of 2026.

The same firing demonstrated the LOX Tank Pressurization Module, the part meant for the C32 stages that will fly on Gaganyaan, India’s human spaceflight programme. ISRO’s release says the engine will now be refurbished and assembled to the C32 flight stage.

What a flight acceptance test checks

The release says the cryogenic engine for every mission goes through a hot test (a real firing on a test stand) as part of its acceptance for flight. The CE20 burns liquid hydrogen and liquid oxygen on the gas generator cycle, ISRO’s engine page says, and it powers the upper stage of the LVM3 rocket.

Its nozzle is built for the near-vacuum of high altitude, which makes a firing at sea level hard. ISRO’s March 2026 release puts the nozzle’s exit pressure at about 50 millibar and names the risk: the flow can separate from the nozzle wall inside it, causing severe vibration and thermal problems at the separation point and possible mechanical damage. ISRO’s answer is a Nozzle Protection System, which its September release says was proven in several qualification tests and which cut the time and effort of acceptance testing compared with simulating vacuum in the High Altitude Test Facility.

Three tests at 22 tonnes in six months

Before March 2026, ISRO’s sea-level tests with the protection system ran at 19 tonnes of thrust. The 22-tonne level came in three steps this year, all at Mahendragiri.

On 10 March, a sea-level hot test at 22 tonnes ran for 165 seconds, which ISRO’s release of 12 March says qualified the engine for sea-level testing at that level. The engine used had gone through 20 hot tests, which ISRO calls a record maximum number for one of its cryogenic engines.

On 6 July, ISRO’s release of 7 July says, a flight acceptance test of an engine earmarked for LVM3-M7 used the protection system at 22 tonnes for the first time. The engine ran at 19.5 tonnes for 45 seconds and at 22 tonnes for 25 seconds.

The 9 September test then repeated the flight acceptance check at 22 tonnes, and ISRO reports it met all objectives. ISRO’s release does not give the length of the September run. A few news reports of that test carry the 165-second figure, but ISRO’s pages tie that run to 10 March. Both the July and September releases link the tested engine to LVM3-M7; neither says whether it was the same piece of hardware. The cryogenic engine article on tuput covers the July test in the longer history of the engine.

The tank module for Gaganyaan

The release says the LOX Tank Pressurization Module for the C32 stages “for Gaganyaan was also successfully demonstrated”. The Daily Pioneer describes the module’s job as keeping the pressure inside the liquid oxygen tank at the level needed during flight. No performance figures for it appear in the releases checked here.

On its Gaganyaan page, ISRO names the LVM3 as the launch vehicle for the programme, with its systems reconfigured to meet human-rating requirements. The July release adds that the CE20 has accomplished the human-rating qualification requirements for Gaganyaan.

Speaking to ETV Bharat on 11 September, ISRO Chairman V. Narayanan said the test succeeded in all aspects. He said the first crewed flight would go in December 2027 or early 2028, after three uncrewed flights. The dated record of those uncrewed flights is in our Gaganyaan G1 article, and the crew itself is in the piece on India’s astronauts.

Why 22 tonnes matters

Both the March and September releases give the reason: the higher thrust is meant to enhance the payload capability of LVM3. The rocket’s current cryogenic stage, the C25, carries 28 tonnes of propellant and has an engine of 200 kN nominal thrust, according to ISRO’s LVM3 page. The uprated engine runs at 220 kN, 10 per cent higher. ISRO’s launcher overview describes the LVM3 as able to launch 4-tonne-class communication satellites and 10-tonne-class payloads to low Earth orbit.

No payload figure for the C32 stage alone appears in the pages checked. The one number ISRO gives is for the uprated stage combined with a new core stage. In March 2025 ISRO said that a semi-cryogenic core stage, the SC120, together with an uprated cryogenic stage would raise LVM3’s capacity to geosynchronous transfer orbit from 4 tonnes to 5 tonnes. Four days before the CE20 test, on 5 September 2026, ISRO fired the power head of the semi-cryogenic engine at its full 200 tonnes of thrust for 5 seconds inside a 35-second test, the ninth in that series. That release says the SC120 is being developed to replace the LVM3’s current core stage.

A separate piece of CE20 work concerns restarts. On 7 November 2025 ISRO fired the engine for 10 seconds under vacuum conditions and started its turbopumps without the usual start-up gas system, a step ISRO says is needed for multiple restarts in flight on multi-orbit missions. In its release of 19 November 2025, ISRO says the engine is already qualified for 19 to 22 tonnes in flight with a single start.

What is scheduled, as of 29 October 2026

For LVM3-M7, the September release gives the fourth quarter of 2026. The pages checked here name no launch date and no payload for that mission.

The engine type has a flight record. According to the July release, the CE20 has performed in eight successive LVM3 missions, among them Chandrayaan-2, Chandrayaan-3 and three commercial missions.