Leak stops launch

Print edition : September 20, 2013

The GSLV-D5 on the launchpad. Photo: ISRO

ON August 19, the launch of India’s GSLV-D5, the latest of the trouble-prone Geosynchronous Satellite Launch Vehicle, suffered a snag in the most unexpected of places—its liquid propellants-powered second stage. A leak developed in the propellant tank and fuel rained down, forcing the launch to be called off. This is the very stage that has worked with aplomb in all the Indian Space Research Organisation’s (ISRO) GSLV and Polar Satellite Launch Vehicles (PSLV) missions so far; the second stage in the GSLV is identical to the two liquid stages used in the PSLV. It has worked with no trouble whatsoever in PSLV’s 23 successful missions in a row (two liquid stages) and in seven GSLV missions.

The GSLV-D5 was a mission the ISRO was looking forward to, for it had an indigenously developed cryogenic stage. This was only the second time that the cryogenic stage developed at the Liquid Propulsion Systems Centre (LPSC) in Mahendragiri, near Nagercoil, Tamil Nadu, was being used. The first flight with the India-made cryogenic engine in April 2010 failed after the fuel booster turbo pump (FBTP) in the cryogenic stage stopped working.

ISRO rocket engineers had analysed all the seven GSLV flights and made modifications in the GSLV-D5.

So ISRO was looking forward to the three-stage, 414-tonne, 49-metre-tall GSLV-D5’s lift-off at 4-50 p.m. on August 19 after a 29-hour countdown. The rocket was to put into orbit a 1,982-kg communication satellite GSAT-14. The countdown hit a snag one hour, 14 minutes and 20 seconds before blast-off. The liquid fuel in the second stage started raining down and dripped over the trellis-like inter-stage between the second and first stages. Soon thick fumes engulfed the second and first stages. About 10 minutes later, an announcement was made at the mission control centre calling off the launch.

ISRO Chairman K. Radhakrishnan told reporters that “a leak in the fuel system of the second stage” had forced ISRO to call off the launch. M.Y.S. Prasad, Director, SDSC, told Frontline that after the launch was aborted, the toxic properties of the propellants were neutralised by diluting and dispersing them with water and chemicals. “It takes a lot of time,” he said. Then the umbilicals/the filling lines on the launch tower were disconnected and the rocket was wheeled back to the Vehicle Assembly Building (VAB) on August 26, Prasad said. Soon the destacking of the three-stage vehicle began and it was done without hiccups.

M.C. Dathan, Director, LPSC, told Frontline on August 27: “At the VAB, we removed the satellite along with the heat-shield without any problem. We have transported the satellite to the clean room. We have destacked the cryogenic upper stage and the GS-2 liquid stage.” He added that the exact location of the leak was yet to be found. There were several lines in the tank for feeding the liquid fuel into or draining it from the tank and “a crack” could have developed in any of the lines or even the plumbing in the tank.

“By September 15 we will have a new second stage and it will be delivered to Sriharikota a week later,” he said. The launch of the GSLV-D5 will be some time in December.

Asked whether the delay would affect ISRO’s mission in October/November 2013 to send an orbiter to Mars, both Dathan and Prasad asserted separately that the delay would “absolutely have no effect” on the Mars mission. A PSLV-XL from the first launch pad in Sriharikota will put the Mars spacecraft into orbit.

T.S. Subramanian