Explained: Why Gaganyaan's TV-D1 test flight failed to lift off initially

The purpose of the mission was to demonstrate the crew escape system

gaganyaan-pti ISRO's TV-D1 test flight of Mission Gaganyaan lifts off from Satish Dhawan Space Station, in Sriharikota | PTI

The Test Vehicle Abort Mission-1 (TV-D1), a high-altitude abort test within the Gaganyaan human space programme, blasted off from the first launch pad at Sriharikota on its second attempt on Saturday. The lift-off was earlier scheduled for 8am, but bad weather conditions and poor visibility, coupled with technical glitches, had forced it to be rescheduled to 8:45am.

However, it transpired that there was an issue with the Gaganyaan mission’s launch attempt and it finally lifted off at 10am.

The Crew Escape System (CES) and the Crew Module (CM), which the Test Vehicle Abort Mission (TV-D1) launched to an altitude of approximately 17km touched down safely in the sea, roughly 10km from Sriharikota’s eastern coast after the main parachute was successfully deployed.

The mission proposed to demonstrate the functionality of the Crew Escape System in initiating an abort condition, taking the Crew Module away from the vehicle and, subsequently, splashed down safely in the sea at 10:11 am, only 11 minutes after lift-off.

Earlier, although the automatic launch sequence began as planned at 8:30 am, it was halted due to an anomaly detected by the mission’s onboard computers, indicating that something abnormal, or unexpected, had been observed in the pre-launch preparations. The ‘In-flight Abort Demonstration’ had been scheduled to run for 8.8 minutes.

ISRO chief S. Somanath mentioned that the launch was postponed due to weather conditions. The team of ISRO scientists tasked with the mission then busied itself in investigating what went wrong. The mission operators analysed the situation and worked on resolving the issue before setting the new launch time.

Earlier, the automatic launch sequence leading up to the command to lift-off on the first attempt went off smoothly, but the engine lift-off did not happen as expected. The ground checkout computer detected an anomaly, which led to stalling of the launch. An automatic launch sequence refers to a predefined, automated series of steps and procedures that are executed to prepare and initiate the launch of a spacecraft, rocket, or other aerospace vehicle. These sequences are designed to ensure that the various systems and components of the vehicle are properly configured and functioning as expected for a successful launch.

“The on board computer detecting an anomaly in the engine implies that the computer system monitoring the spacecraft’s engines identified something unusual, or unexpected. This could include issues such as irregular engine performance, deviations from expected parameters, or potential problems with the propulsion system. Detecting an anomaly in the engine is a safety measure to ensure that the engine functions correctly and that the launch can proceed without risking the mission or the vehicle. It may trigger an automatic halt in the launch sequence to investigate and address the issue before proceeding,” said space expert Girish Linganna.

Linganna explained that in such a case, the ignition system needs to be physically verified as there is a concern or suspicion regarding the ignition system of the spacecraft. “Under such circumstances, the mission operators, or engineers, need to conduct a hands-on inspection to ensure that the ignition components are in proper working condition. This is done to verify that there are no faults or issues with the system responsible for igniting the rocket engines, as any problems with the ignition system could have serious consequences for the launch. Physical verification involves inspecting, testing and potentially repairing, or replacing, components as needed to ensure a safe and successful ignition for the launch,” added Linganna.

Once the issue was rectified, the mission operators and engineers assessed the readiness of the entire vehicle and its systems, conducted the necessary tests and safety checks and ensured that all conditions were favourable for a safe launch. Following this, the mission control team made a decision on the new launch time based on when they were confident that all systems were functioning correctly and that it was safe to proceed.

Somanath said that the purpose of the mission was to demonstrate the crew escape system. The vehicle went slightly above the speed of sound, before it initiated the crew escape system. He informed that the escape system took the crew module away from the vehicle and subsequent operations including the touch down at the sea had been very well accomplished.

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