xxiii.1. GSLV D5 : The rocket

delete UPSC Sample Notes [English]

xxiii.1. GSLV D5 : The rocket

For beginners : Rocket and Satellite are two different entities. Rocket or launch vehicle is the vehicle used to launch satellites. In other words, launch vehicle will have a rocket engine in it and this rocket engine is fired to launch the satellites into the orbit. Examples of launch vehicles include PSLV, GSLV etc. Examples of satellites include GSAT, INSAT, IRS etc.

GSLV D5: GSLV D5 is a rocket (launch vehicle) used to launch the satellite GSAT 14. The rocket engine used in this launch vehicle was a cryogenic one, which uses cryogenic propellants at low temperature.

What’s special about GSLV D5 launch?	India already had successfully launched many satellites using launch vehicles in the PSLV and GSLV series. But this was for the first time, India successfully launched a satellite using its indigenous developed cryogenic engine. In the previous missions of GSLV, we were using Russian Technology for cryogenic engines. But now, we have mastered cryogenic technology and have emerged as a major space power. GSLV is a three-stage launch vehicle with solid, liquid and cryogenic stages. It is designed to inject 2 Ton class of communication satellites to Geosynchronous Transfer Orbit (GTO). GSLV-D5 vehicle is configured with its first and second stages similar to the ones flown during earlier GSLV missions. The third stage is the indigenous cryogenic stage.
Propellants used in the three stages of GSLV	1 Stage (Strap- Ones) : UH25 & N2O4. 1 Stage (Core Stage) : HTPB. 2 Stage : UH25 & N2O4. 3 Stage : LH2 & LOX. HTPB : Hydroxyl Terminated Poly Butadiene, LH2: Liquid Hydrogen, LOX : Liquid Oxygen. N2O4 : Nitrogen Tetroxide, UH25 : Unsymmetrical Dimethyl Hydrazine + 25% Hydrazine Hydrate. Cryogenic propellants used in this mission: liquid oxygen at minus 183 degrees Celsius and liquid hydrogen at minus 253 degrees’ Celsius.
About the cryogenic engine	India’s indigenous cryogenic engine is named CE-7.5. This cryogenic rocket engine is used to power the upper stage of GSLV. The engine was developed as a part of the Cryogenic Upper Stage Project (CUSP). It will replace the KVD-1 (RD-56) currently powering the upper stage of GSLV. Advantages: Cryogenic rocket stage is more efficient and provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellant rocket stages. Specific impulse (a measure of the efficiency) achievable with cryogenic propellants (liquid Hydrogen and liquid Oxygen) is much higher compared to earth storable liquid and solid propellants, giving it a substantial payload advantage. However, cryogenic stage is technically a very complex system compared to solid or earth-storable liquid propellant stages due to its use of propellants at extremely low temperatures and the associated thermal and structural problems.
GSLV Variants	The main variants are GSLV Mk.I and GSLV Mk.II. GSLV Mk.II variant uses an Indian cryogenic engine, the CE-7.5, and is capable of launching 2500 kg into geostationary transfer orbit. Previous GSLV vehicles (GSLV Mk.I) have used Russian cryogenic engines. GSLV Mk.I had three sub-variants like GSLV Mk.I (a), GSLV Mk.I (b) and GSLV Mk.I (c).