Pressure on ISRO to produce winner, after 2 failures in 2010
The flight of the Geosynchronous Satellite Launch
Vehicle (GSLV-D5) — at 4.18 p.m. on Sunday — from Sriharikota will be an
acid test for India as it seeks to prove the design, realisation and
sustained firing of its indigenously built cryogenic engine. There is
pressure on the Indian Space Research Organisation (ISRO) to produce a
winner because of two back-to-back failures of the GSLV flights in 2010 —
the first, with an indigenous cryogenic engine, on April 15 and the
next, with a Russian cryogenic engine, on December 25.
ISRO’s
next GSLV flight, with an indigenous cryogenic engine, on August 19,
2013, was called off 75 minutes before lift-off: the liquid fuel from
the rocket’s second stage had leaked, wetting the first stage and the
four strap-on boosters around it. So ISRO dismantled the 49-metre tall
vehicle, weighing 415 tonnes and built a refurbished GSLV-D5, with new
first and second stages and four new strap-on booster motors. It has
used a new propellant tank in the second stage, made of an aluminium
alloy different from the one used in August.
Cryogenic engines are essential for rockets to put communication satellites, weighing more than two tonnes, into orbit.
The
Chandrayaan-2 mission, scheduled for 2016, will use a GSLV with an
indigenous cryogenic stage. ISRO has to produce two winners in a row
with GSLVs with India-built cryogenic stages before it can confidently
send up the Chandrayaan-2, which will deploy an India-made lander and
rover on the moon.
So Sunday’s mission is a crucial
one and expectations are, therefore, high from ISRO to deliver. The
three-stage GSLV-D5 will put into orbit a 1982-kg communication
satellite called GSAT-14.
“We have done our best,” K.
Radhakrishnan, ISRO Chairman, said on Saturday evening from
Sriharikota. “The countdown for the [GSLV-D5] flight began at 11.18 a.m.
The rocket’s second stage has already been filled with the liquid fuel
and oxidiser.” Fuel-filling for the four strap-on booster motors began
after 6 p.m. “Things are progressing smoothly and the weather is fine,”
he said.
M.C. Dathan, Director, Liquid Propulsion
Systems Centre (LPSC), ISRO, said: “We have done everything humanly
possible” to ensure the success of the mission. “We have drawn on all
the expertise available,” he said. The LPSC at Mahendragiri, Tamil Nadu,
is the architect of not only the cryogenic stage for this mission but
also the second stage and the four strap-on motors. The second stage and
the strap-on motors use liquid fuel.
The Launch
Authorisation Board met on Friday and gave the green signal for the
launch. “Everything is fine,” the LPSC Director said. The filling of the
cryogenic propellants in the third, uppermost stage of the vehicle
would begin around 1 p.m. on Sunday.
ISRO rocket
engineers said cryogenic technology is extremely complex and difficult
to master. It uses liquid oxygen at minus 183 degrees Centigrade and
liquid hydrogen at minus 253 degrees Centigrade. An engineer said: “The
turbo-pump in the cryogenic engine should supply the fuel to the
combustion chamber at high pressure. This injection should take place
with the right proportion of the fuel and the oxidiser. Then the fuel
has to be ignited. This is unlike the liquid engine where you mix the
propellants and they ignite spontaneously.” There were challenges
involved in developing the insulation to keep the liquid oxygen and
liquid hydrogen at their low temperatures. “They should not boil off.”
The
combustion of the propellants in the cryogenic engine should be proper.
Otherwise, liquid oxygen and liquid hydrogen will explode. “It is not
enough if you start the combustion. You have to sustain it,” the rocket
technologist said.
If the GSLV-D5 mission lasts about
17 minutes, the cryogenic engine itself will fire for a full twelve
minutes. At the end of seventeen minutes, the rocket will put the
GSAT-14 satellite into orbit. GSAT-14 will be used for telecasting,
telecommunication, tele-medicine and tele-education.
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