Cryogenic engine for India's next GSLV launch passes its acceptance test, ISRO says

The Indian Space Research Organisation has test-fired the cryogenic engine for its next Geosynchronous Satellite Launch Vehicle. In a release dated November 10, ISRO said the cryogenic engine chosen for GSLV-F19 went through its flight acceptance test on November 5 at the ISRO Propulsion Complex in Mahendragiri. The firing lasted 200 seconds. ISRO said the main engine and the gas generator both ignited as expected, and that the engine ran normally, in line with the predictions made before the test.

The engine will now be fitted into the rocket's cryogenic stage. According to ISRO, GSLV-F19 is to launch the NVS-04 navigation satellite. The release gives no launch date or window.

The stage the engine powers

ISRO's brochure for the previous flight, GSLV-F18, shows only one stage burning liquid hydrogen and liquid oxygen: the third, listed as CUS15, which was 9.8 meters long, 2.8 meters wide and carrying 14.4 metric tons of propellant. The whole rocket stood about 50 meters tall and weighed about 420 metric tons at liftoff, and its satellite weighed about 2,250 kilograms. ISRO's home page links no brochure for GSLV-F19 yet, so the new rocket's figures may differ.

Days after NVS-03

The test came within a week of the last GSLV launch. GSLV-F18, the rocket's 20th flight, lifted off from the Second Launch Pad at the Satish Dhawan Space Centre and, ISRO said, injected the NVS-03 satellite into an elongated orbit of 170.3 by 38,080 kilometers on October 30.

From there the satellite climbed on its own engine. ISRO reported a first burn of 2,174.8 seconds on October 31. On November 4 it said four burns, totaling 6,164 seconds, had taken NVS-03 to geosynchronous orbit, with the satellite in normal health. ISRO plans to station it at 111.75 degrees East.

Why the NVS satellites matter

NVS-03 is the third of ISRO's next-generation navigation satellites, which ISRO intends to carry on the services of its IRNSS series. They serve NavIC, India's independent regional system for position, navigation and timing, whose primary service area ISRO gives as India and a region reaching about 1,500 kilometers beyond the Indian landmass. NVS-03 carries an atomic clock made in India alongside procured clocks, and adds an L1 signal to the L5 and S-band signals the system already broadcasts.

The setback before NVS-03

Its predecessor did not get that far. NVS-02 reached its transfer orbit on January 29, 2025, after launch on GSLV-F15, but could not be raised from that elliptical orbit to a circular one. An ISRO review committee, whose findings ISRO published in February 2026, concluded that the signal to fire a pyro-operated valve in the oxidizer line of the orbit-raising engine never arrived. It judged the likeliest cause to be a connector in which at least one contact had disengaged, in both the main path and the backup.

ISRO said the committee's fixes were built into the CMS-03 satellite, launched by LVM3-M5 on November 2, 2025, whose pyro systems worked, and would be followed on future missions. Read together, ISRO's two reports show NVS-03 completing the orbit raising that NVS-02 could not; that comparison is ours.

What comes next

Neither the release nor ISRO's home page gives a date for GSLV-F19. The engine tested on November 5 still has to be built into the cryogenic stage. For GSLV-F18, ISRO published a brochure with the rocket's specifications before the launch.