Gaganyaan: Bringing spacecraft back to earth safely; Why is it challenging?
New Delhi, Oct 06: India's first manned mission to space, presents a massive technological challenge to ISRO. A setback or failure are not an option as there would be human lives involved. All ISRO missions so far involved sending satellites/spacecraft out of the earth's atmosphere, but in Gaganyaan the humans launched into the space must be brought back and brought back safely.
Among many technologies that ought to be perfected for a manned mission, two most important are the ability to bring the spacecraft back to Earth after the flight, and to build a spacecraft in which astronauts can live in Earth-like conditions in space.
Gaganyaan or for that matter any space mission that involves human beings presents a massive technological challenge because there is absolutely no room for any error or even a small malfunction when safety of astronauts is concerned. Re-entry of the spacecraft into earth's atmosphere is a complex challenge.
Why is Re-entry a challenge?
When a spacecraft re-enters earth's atmosphere, it would have to withstand high temperatures, thousands of degrees, due to friction with the air. Even when a meteorites enter the atmosphere, earth's gravity speeds up its descent which causes friction with the air. This friction increases the temperature so much that most of the meteorites just vapourise before reaching the earth's surface. This is the reason we see shooting stars.
The spacecraft's re-entry into the atmosphere also has to be very precise both in terms of speed and angle, and even the slightest deviation could end in disaster. For this, a heat shield that can withstand thousands of degrees needs to be developed. After, re-entry, the spacecraft would land at a precise spot in the sea from where Navy or Coast Guard would bring it back to the mainland. So that is why speed and angle are important, the re-entry vehicle has to return in a pre-planned path in an accurate manner.
What is CARE or Crew Module Atmospheric Re-entry Experiment:
The Crew Module Atmospheric Re-entry Experiment (CARE) is an experimental test vehicle for the Indian Space Research Organisation's future ISRO orbital vehicle called Gaganyaan. It was launched successfully on 18 December 2014 from the Second Launch Pad of the Satish Dhawan Space Centre, by a GSLV Mk III designated by ISRO as the LVM 3X CARE mission.
The crew module was mounted upside-down inside the payload fairing of the GSLV Mk III. CARE was made of aluminium alloy and had a lift-off mass of 3,735 kg. Its diameter was 3100 mm and its height was 2698 mm. The module had an ablative thermal protection. The side panels were covered with Medium Density Ablative (MDA) tiles and the forward heat shield was made of carbon phenolic tiles. It was powered by batteries and was equipped with six liquid-propellant (MMH/MON3) 100 N thrusters.
CARE splashed down into the Bay of Bengal about 600 km from Port Blair in the Andaman Islands and about 1600 km from the Sriharikota launch site. This experiment was carried out to test the re-entry capability of the spacecraft that would bring the Gaganyaan crew back to earth.