Around 9:30 this morning, the Space Capsule Recovery Experiment (SRE) satellite made a safe 'splashing' somewhere in the Bay of Bengal [Update: ISRO's press release is here]. And with that, the Indian Space Research Organization (ISRO) has taken yet another big step towards an important capability: sending a module up, getting a bunch of things done inside this module up in space, and guiding it to a safe-splashing site for recovery. All of these tricky steps required development of critical technologies, and it's a big day for ISRO.
It's also a big day for Prof. Kamanio Chattopadhyay, Chairman of the Department of Materials Engineering at IISc. Yes, he coordinated a couple of scientific experiments that went on under microgravity conditions -- while the SRE capsule was in a free fall over the last ten days or so. [In today's Hindu, Gopal Raj has an article on these experiments.]
Kamanio told me about the long and tortuous journey that culminated in this morning's successful recovery of the SRE capsule from the Bay of Bengal. His own involvement started in the late seventies, when he accompanied his Ph.D. thesis advisor Prof. Ramachandra Rao (who was then at IT-BHU) to a meeting organized by Prof. S. Ramaseshan to brainstorm microgravity research. This round of efforts led to solidification experiments designed by Prof. Rao and conducted by Rakesh Sharma -- the first Indian in space -- aboard the Salyut 7 space station in 1984. I still remember -- as an undergrad at BHU -- all the excitement caused by the 'Rakesh Sharma experiments', because the brain behind them -- Prof. Rao -- was 'one of us' in the Department of Metallurgical Engineering.
[A quick aside, with this quote from Wikipedia: "In a famous incident, he was asked by the then Prime Minister Indira Gandhi how India looked from the space and he replied, Saare Jahan Se Achcha, (translates to better than all the world) which was from the first line of a famous poem by Muhammad Iqbal."]
A few years later, another team was put together to plan microgravity research -- this time on ISRO's own vehicles. After an initial flurry of activity, these plans didn't go anywhere because of the financial crunch of the early nineties. The ideas were revived in late nineties, some of them were firmed up in 2005, and implemented last fortnight. A bigger, better and fancier mission is planned for 2008.
Just a few words about some of the challenges posed by the design of the SRE capsule. On the inside, the experimental payload needed to be small -- some forty kilograms for all the experiments put together (including a tiny furnace)! The choice of material was constrained by the maximum temperature that Kamanio's team could work with -- about 500 degrees Celsius. As for the capsule's outside, an important achievement from a materials viewpoint is the development of heat shield tiles which protect the SRE capsule from the intense heat generated by friction between the capsule the earth's atmosphere.
All in all, the SRE capability is yet another milestone for ISRO, and I'm sure everyone there is proud of pulling it off.
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Kamanio also told me about the experiment he directed with immense help from S.C. Sharma, an engineer at the Vikram Sarabhai Space Centre at Thiruvananthapuram. It is on the growth of quasicrystals in an alloy containing gallium, zinc and magnesium. In the same chamber, he also had another experiment on the solidification of an alloy of bismuth and tellurium.
Think of a solution of salt in water. At room temperature, there is a certain limit -- called the solubility limit -- to how much of salt you can dissolve in water. This solubility limit is higher at higher temperatures. Imagine now a salt solution prepared at, say, 70 degrees Celsius, right upto the solubility limit. If this solution is cooled to room temperature, you would expect the excess salt to come out of the solution, and you would be right. If you wait a while, you will find tiny salt particles at the bottom of the vessel.
There are two things to notice: first, the solid that comes out is almost 100 percent salt, whereas the solution it came from has a far smaller salt content. Second, earth's gravitational pull makes the salt particles (which come out the solution through a process called "precipitation") sink to the bottom because they are heavier than the surrounding solution.
In a solidification experiment, you keep cooling the solution down until the whole thing -- including water -- becomes a solid. Such a solid would have mostly salt at the bottom and mostly ice at the top. In other words, it is segregated. It is this segregation -- and associated complexities -- that one hopes to avoid (or, slow down tremendously) by going to space where the gravitational pull is far smaller (Microgravity!) than on earth.
The second experiment, designed by scientists at the National Metallurgical Laboratory at Jamshedpur, was on the growth of a kind of calcium phosphate (found in bone) called hydroxyapatite. I don't know much about this experiment, though.