Two of India's leading scientists spoke to rediff.com about the Columbia space shuttle tragedy.
Indian Space Research Organisation chairman Dr Krishnaswamy Kasturirangan had earlier headed the ISRO Satellite Centre, where he oversaw the launch of the Indian National Satellite (INSAT-2) and the Indian Remote Sensing satellites.
Institute of Strategic Studies and Analyses Director K Santhanam is known for his contributions to the Pokhran nuclear tests in May 1998.
"In our world, we can create near-perfect things. But there is a little difference between a near-perfect system and the perfect system. Space systems are much closer to the perfect system, but still that little difference is always there.
"The space community of the world is a closed one. When something like this happens we communicate and learn important lessons.
"Here, the disaster struck when the shuttle was at a critical juncture. Such a shuttle's speed is 25 times faster than sound, almost 18,000 miles per hour. Its velocity is tremendous when it enters the earth's atmosphere because of the speed.
"We are told when the disaster happened the shuttle was at an altitude of 200,000 feet and was moving 18 times faster than sound. That was a very critical phase. Its thermal and mechanical force was tremendous.
"We don't know much about the personal performance of the systems. So I can't say anything more. But certainly this disaster will become an input for the space agencies all over the world.
"Unfortunately, I have not met Kalpana Chawla in person. I had received her nice letter praising our projects. I could see her heart and feelings for her native town and for India.
"In 1997, I had gone to NASA just after her first space visit. Then, I asked NASA administrator Daniel Goldin what he thought of Kalpana Chawla. He said: 'She is terrific.' "
"I don't think this disaster will affect our spirit. Humans are outward-looking. Our spirit to explore, to move out from land to sea to air and now to space, cannot be defeated.
"We have moved on, learnt and progressed. We will continue to do so. One can't be a chicken-heart in space. The lives that were lost were not just Americans, they were citizens of the earth. But we must rekindle our spirit, it should not deter our future endeavours."
"This news broke my heart. I think in all these missions, including unmanned missions, there is something called reliability factor. Laws of reliability are fairly cruel. In such missions, there is a certain probability. There are no short-cuts; there cannot be, because technology is an unforgiving mistress.
"Many space agencies in the world believe NASA has been an arrogant agency. When the Challenger shuttle crashed, Nobel laureate and distinguished physicist Dr Robert P Feynman demonstrated how NASA had taken short-cuts. It's all right to have remote-sensing and communication shuttles, but when you have manned shuttles, the responsibility increases enormously. India and China, who too want their men in space, should look at such disasters and learn lessons.
"[The speculation that there was sabotage is] absolutely absurd. Do you think if there was an Iraqi on the shuttle the fate could have been any different? Such charges are maybe for the American audience, but I see no possibility of terrorist involvement.
"Columbia was part of the Shuttle Transport Service the US and Russia were jointly working on. This mission can get delayed because of today's disaster."