When a leak nearly grounded Chandrayaan-1

M. Ramesh | | | Updated on: Jul 12, 2019

In a space mission, any thing can go wrong, and often something does. As the Chandrayaan-2 mission gets ready to take to the skies, veterans remember some tense moments with its predecessor.

The Chandrayaan-1 was launched on October 22, 2008. The previous day, liquid propellant was being filled onto the second stage. The propellant consists of a fuel, a chemical called UH25, and oxidiser nitrogen tetroxide. Nitrogen tetroxide is a highly toxic chemical; inhale and you are gone. Twenty-five tonnes of it were to go into the rocket.

The filling, handled by computers, was being supervised by a team headed by Director-operations MYS Prasad some 10 km away. Around 3 pm, the CCTV monitors showed thick, pink-coloured smoke engulfing the rocket.

Braving the toxic fumes, two people — Prasad and Annamalai — drove to the launch pad, and wearing gas masks inspected the rocket. To their relief, they found the problem was a leaky joint in the pipe connecting the oxidiser tank and the rocket. The rocket itself was fine.

It took several hours to repair the coupling. The team also realised that to prevent a leak from recurring, the loading would have to be slowed. They did, yet the coupling sprang a leak.

So, once again a team was sent to do the repair. This set the clock back by some three hours. Worse, a leak occurred a third time, around midnight.

“The entire world was watching us...,” recalls Prasad. If the mission was aborted, it would be a national shame. By that time, 23.5 tonnes of the oxidiser had been loaded. K Sivan (current ISRO Chairman), who was in charge of computer simulations, did some calculations and said the rocket was good to go with this much oxidiser.

At this point, the fuel had to be loaded, raising a dilemma. If a similar leak occurred while loading the fuel, it would come in contact with the oxidiser hanging around, and result in an explosion.

Prasad decided to first blow away the oxidiser cloud, using the compressed air kept for some other purpose. This was done, and fuel loading began.

It was also decided that other operations, such as charging of the satellite batteries, would go on simultaneously, rather than sequentially, to save time. After all the drama,the PSLV-C11 took off carrying Chandrayaan-1, and the mission was a success.

Published on July 12, 2019

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