Better Safe than Sorry
Though the glitch was minor, ISRO scientists are unwilling to take any risk in ensuring a perfect launch for Chandrayaan 2
At the launch of a spacecraft, the most watched are the giant digital countdown clocks fitted in the control room where the scientists are seated as well as in the media gallery. For India’s second moon mission, Chandrayaan 2, the clock began counting down 20 hours before the spacecraft was slated to be launched at 2.51 am on July 15 at the Indian Space Research Organisation (ISRO) facility in Sriharikota in coastal Andhra Pradesh. The 5,000-odd visitors seated in the amphitheatre nearby watched the clock on a giant monitor with anticipation.
For the countdown, ISRO had developed a rigorous review of every critical component of the spacecraft, including its rockets, apart from the communications and tracking facilities.
That’s because space is unforgiving. A slight error in calculation or a malfunctioning valve could cause the
Rs 1,000 crore Chandrayaan 2, which took over a decade to conceive and develop, to break up and tumble ignominiously into the Bay of Bengal.
There was much riding on this launch for India for even President Ram
Nath Kovind to fly down to witness it. Chandrayaan 2 was a quantum leap in technological advancement and mission objectives from the first moon mission India successfully sent up in
2008. Chandrayaan 1 had an orbiter and impact probe. Its successor has not only a far more sophisticated orbiter, but also a robotic lander equipped with a rover designed to traverse a radius of half a kilometre on the lunar surface.
Equally important is the heavy lift GSLV-Mark 3, India’s most powerful launcher, developed just five years ago and which has had only three flights so far. Capable of lifting over 4 tonnes of payload, GSLV-Mark 3 was designed not only to launch heavier communication satellites into geosynchronous orbits but also India’s manned mission Gaganyaan and the probes being planned to visit the moon and other parts of the solar system.
The upper stage of the moon launcher was fitted with an indigenously built cryogenic engine or one that uses super-cooled hydrogen and oxygen as fuel. As compared to the solid motor and the liquid fuel engine in the other two stages, the cryogenic engine proved to be the most difficult
for ISRO to master. That’s because the temperature variation to be handled ranges from minus 253 degrees centigrade in which the hydrogen fuel has to be maintained to a blazing 1,000 degrees centigrade when the engine fires. Apart from the engine being built with special metals to withstand such great temperature fluctuations, it also requires an intricate network of piping to not only fill the fuel tanks before lift-off but also inject the super-cooled fuels into the combustion chamber where these can be ignited.
The first indication that something was wrong came a little less than an hour before lift-off, when the countdown clock stopped. It was followed by a terse announcement from the ISRO spokesperson that the launch had been postponed. While scientists remained tight-lipped about what caused the hold-up, it was reliably learnt that while the cryogenic engine was being fuelled up, the monitors registered an anomaly. The pressure readings from the spherical helium bottles that maintain the requisite pressure and control the valves supplying fuel to the engine were below normal. Scientists have surmised that the leak was mostly likely because of a faulty plumbing in the helium container system.
ISRO scientists could have lived with some variation in the pressure levels in these helium bottles, but preferred to play it safe. The launch was postponed to enable them to detect the source of the problem and rectify it. All indications are that the snag was not that serious, as after the initial review, ISRO scientists were confident of repairing the malfunctioning part without wheeling the spacecraft back into the assembling workshop at the complex. Given the reasons for the hold-up, when the spacecraft is set for launch again, ISRO scientists will watch with great anxiety how GSLV-Mark 3’s rocket engines function. That’s only the first part—it will take another month and a half before the payload reaches the moon and the lander and rover plonk themselves on the lunar surface. K. Sivan, ISRO’s chairman, calls these the most “agonising moments”. If India succeeds, it will be only the fourth nation to do so, next only to the US, Russia and China. It is a status worth waiting for, not just for a week but even for a month or more, before successfully launching Chandrayaan 2.