Of the four satellites that were launched on Wednesday, one — the 550-kg Space Capsule Recovery Equipment (SRE-1) — blasted off, carrying with it the burden of India’s hopes of a successful moon mission.
As ISRO chairman Madhavan Nair says, “This is the first time that we are planning to bring back a space capsule to Earth after launching it. A lot of new technologies have gone into it and it will perform experiments in microgravity conditions before being de-orbited and recovered from a precise landing spot. This technology will help us in future manned missions.”
It is crucial for the country’s moon mission ‘Chandrayaan’ — that is on course for a 2008 launch date — that the space capsule successfully orbits Earth for about a fortnight before reentering the atmosphere and splashing down in the Bay of Bengal.
India’s chances of making it to an elite club of countries with satellite reentry technology depend on the SRE’s successful orbiting, deorbiting, reentry and recovery.
The problem of reentry into Earth's atmosphere — that of overcoming the heat generated by friction as a spacecraft slows in the atmosphere — was always a big challenge for space-flight researchers.
Not that all early reentry vehicles were spacecraft. Some, like atomic warheads launched atop ballistic missiles, had no choice but to scrape through the atmosphere. They would fly up in a cannonball arc above most of the atmosphere and then come screaming back through it at some 20 times the speed of sound, heating up tremendously.
In the early 1950s, scientists discovered that increasing the drag on it could reduce the heat generated by a spacecraft. Which is why the best designs are still ‘blunt body’ ones. Instead of the needle-noses, the blunt noses form a thick shockwave ahead of them to deflect the heat and slow them more quickly. Even with the current raft of new technologies, atmospheric reentry remains a tricky manoeuvre. Come in too steeply, and you burn up; approach at too shallow an angle and you skid off the atmosphere.