The failure of the launch of GSLV-D3 on 15th April, is being attributed to the non-ignition of the indigenously developed cryogenic engine that was being tested in this mission. Now the million-dollar question is why did the cryogenic engine fail to ignite? "The cryogenic engine has not ignited, that is for sure. Why it has not ignited, the reasons have to be found out," is what the ISRO spokesman is reported to have said.
The cryogenic engine uses liquid hydrogen (LH2) at 20 kelvin as fuel and liquid oxygen (LOX) at 89 kelvin as oxidizer. Here is a detailed explanation of the working of a cryo-engine.
The GSLV took off at 4:27 p.m. normally. It developed problem only when the cryogenic engine should have ignited at exactly 304 seconds from lift-off. Scientists at ISRO are puzzled as to why the cryogenic engine failed to ignite even though the vehicle had been repeatedly reviewed by experts in cryo-technology and was given a go-ahead. Even though the cryo-engine was required to fire only for 720 seconds on flight, it had been tested on ground for a total of 7,767 seconds. The problem appears to be that the ignition of the cryo-engine taking place in space vacuum cannot be simulated on ground. Apparently, even after passing umpteen number of tests on ground, the cryogenic engine cannot be guaranteed to fire in space.
So until we have mastered the art and science of cryogenic engine technology, Indian Space programme seems to be a gamble in uncertainty!