 "GSLV-D5 to take off on Sunday")
The vehicle will carry GSAT-14 satellite, which will provide India with communication services, including tele-education and telemedicine. The mission will be the first launch in 2014 by any space agency in the world; if it succeeds, GSAT-14 will be the first satellite to reach space this year.
After three continuous failures of GSLV, this is Isro’s first attempt to flight test its indigenously-developed cryogenic engine. A 29-hour countdown will start on Saturday at 11.20 hrs (IST). Isro had successfully completed the rehearsal for the launch on Thursday.
The 50-metre high GSLV-D5, which is equal to a 15-storey building, was chosen for this mission because the satellite, GSAT-14, weighs about two tonnes and it cannot be taken up by Isro’s tried and tested Polar Satellite Launch Vehicle (PSLV), which can carry only about 1.4 tonnes.
GSAT-14 will augment the in-orbit capacity of Extended C- and Ku-band transponders and provide a platform for new experiments. On December 28, 2013, Isro’s Mission Readiness Review (MRR) team and the Launch Authorisation Board (LAB) had cleared the launch at 16:18 hrs (IST) on January 5, 2014 from the Sriharikota. The vehicle was moved from its assembly building to the umbilical tower (launch pad) on the same day.
Upper stage
GSLV is a three-stage launch vehicle with solid, liquid and cryogenic stages. The GSLV-D5 is configured with its first and second stages similar to the ones flown during the earlier GSLV missions. The third stage is the indigenous cryogenic stage. Isro explains that a cryogenic rocket stage is more efficient compared to solid and earth-storable liquid propellant rocket stages.
Specific impulse (a measure of efficiency) achievable with cryogenic propellants (liquid hydrogen and liquid oxygen) is much higher than earth storable liquid and solid propellants.
However, cryogenic stage is a very complex system compared with solid or earth-storable liquid propellant stages due to its use of propellants at extremely low temperatures and the associated thermal and structural problems.
Design improvements
Based on its performance during the earlier missions, end-to-end design of GSLV and indigenous cryogenic stage systems have been re-examined, Isro said.
Design modifications are implemented wherever required along with rigorous ground testing. These include redesign of ‘Lower Shroud’, which protects the cryogenic engine during atmospheric flight and redesign of the wire tunnel of the cryo stage to withstand larger forces during flight, among others.
In addition, indigenisation of many critical systems, including Liquid Hydrogen Propellant Acquisition System (to prevent the possibility of contamination), polyimide pipelines and Liquid Oxygen and Liquid Hydrogen Level Sensors, has been successfully accomplished.
“All the improvements have been thoroughly reviewed by expert committees including eminent national experts,” said Isro.
Previous Missions
The GSLV-D5 was scheduled for launch at 16.50 hrs on August 19, 2013, from Sriharikota; this was, however, called off at the last minute after Isro identified a leak during the pre-launch pressurisation process in the fuel system of the liquid second stage.
The GSLV was first launched with GSAT-1 on April 18, 2001, which was successful.
Out of the seven GSLV launches earlier, three were unsuccessful.