Chennai: After a gap of several decades, the Indian space agency has reverted to fibre reinforced plastic (FRP) heat shield for its geosynchronous launch vehicle - development 3 (GSLV-D3) rocket expected to blast off Thursday evening.
The GSLV-D3 rocket has a bigger heat shield - four metre diameter - as compared to the earlier rocket versions whose heat shield were of 3.4 metre diameter and were made of aluminium alloy metal.
The rocket will carry communication satellite geostationary experimental satellite (GSAT-4) weighing two tonne.
"In order to reduce the rocket weight, the Indian Space Research Organisation (ISRO) has decided to use a FRP heat shield. A bigger heat shield will provide more space for carrying a bigger payload," an ISRO official told IANS on the condition of anonymity.
According to him, a bigger equipment bay will not constrict ISRO`s satellite building team in their ventures.
Heat shield made of FRP is not new to ISRO as it was used in its satellite launch vehicles (SLV) earlier.
However, the space agency changed to metallic heat shield when it designed its workhorse rocket polar satellite launch vehicle (PSLV) and also in GSLV.
"The increase in heat shield size is made with future launches in mind. While the heat shield of SLV was just one metre diameter, here it is four metre. The challenge was to make the mould," the ISRO official said.
Meanwhile, the GSLV-D3 completed the "pyro arming activity" Tuesday. This means all its circuits are ready to fire except the critical circuit on-board the rocket.
Countdown for the launch started at 11.27 a.m. Wednesday - 29 hours
before the blast-off - with all related activity progressing smoothly.
Filling of the liquid propellant in the four strap-on motors (40 tonne each) that will be hugging the rocket and the second stage (40 tonne) will happen Wednesday. The whole process is expected to take around 12 hours.
The propellant filling for the Indian designed cryogenic stage (15 tonne) will start five hours before the rocket launch and will get over minutes before the actual blast-off. The first stage with solid fuel is all ready to be fired.
The rocket is expected to blast off at 4.27 pm Thursday to deliver the GSAT-4 into the geosynchronous transfer orbit (GTO).