ISRO is preparing to launch the NVS-03 navigation satellite while facing a tricky engineering question about its oxidiser-line pyro valve. The previous NVS-02 mission failed because a signal did not reach this valve. Experts now wonder if keeping the valve open during launch is safer to avoid another orbit failure.
As ISRO readies to launch the NVS-03, an unusual engineering question hangs in the air
It is a small valve carrying a big responsibility. As ISRO prepares to launch the navigation satellite NVS-03, the successor to the NVS-02, an unusual engineering question has come into focus: Should the spacecraft be launched with its oxidiser-line pyro valve kept open?
This follows the failure of the NVS-02 to raise itself into its intended orbit. Its propulsion system did not function as expected because the drive signal failed to reach the oxidiser-line pyro valve, which had to open for orbit raising.
ISRO's investigation concluded that the most likely cause of the failure was the disengagement of at least one contact in each of the main and redundant connector paths. Corrective measures were subsequently implemented in CMS-03, launched on November 2, 2025, and its pyro systems performed satisfactorily.
A pyro valve is a one-shot mechanism: Once activated, it cannot be reset. The failure of the signal path in the NVS-02, therefore, raised the question of whether the NVS-03 should adopt a different configuration.
One option is to launch the satellite with the oxidiser-line pyro valve kept open. This would remove the need for the activation signal to open the valve after launch, avoiding a repeat of the suspected failure sequence in the NVS-02.
But removing one risk may introduce another.
With the pyro valve already open, the downstream latch valve would have to provide the needed isolation. If it were to leak due to the vibrations or pressure conditions during launch, the consequences could be serious. Additionally, the corrective measures on CMS-03 do not automatically settle every question concerning the NVS-03's configuration.
Wider implications
NavIC, India's regional navigation satellite system, is operating with limited redundancy. In a written reply to Parliament in July, the government said only three satellites -- IRNSS-1B, IRNSS-1I and NVS-01 -- were providing positioning, navigation and timing services.
Four operational satellites are needed for basic positioning. The NVS-03 is, therefore, more than the next satellite in the replacement programme. Its performance matters to the restoration and continuity of NavIC services. NVS-04 and NVS-05 are the other planned replacements over the coming 15-18 months. The newer NVS satellites bring additional capabilities, including signals in the L1 band, which can improve compatibility with navigation receivers.
Would a delay in the NVS-03 launch be justified if the engineering team remains uncertain about the safest valve configuration?
For ISRO, the 'open' or 'closed' debate is ultimately not about a valve alone. It is about how engineers balance one known failure mode against the possible risks of an alternative design.
Every engineering practice has a first time. Perhaps this could be India's first -- with NVS-03.