Frequently Asked Questions (FAQ)

1. Which are the liquid propulsion systems used in PSLV, GSLV & LVM3 ?

   In PSLV, the second and fourth stages viz PS2 and PS4 stages are powered by liquid propulsion engines. The PS2 stage is powered by a Vikas engine with 800kN thrust and stage propellant loading of 40 tons. The fourth stage is powered by two PS4 engines delivering 14.7kN thrust with stage propellant loading of 1.6 to 2.6 tons. Besides, PSLV first stage uses liquid propulsion based Control Power Plants namely SITVC and RCS for Pitch, Yaw and Roll control.

   In GSLV, the 4 nos of L40 strapons are liquid propulsion Vikas engine powered stages with propellant loading of 40 tons. Besides, the second stage, GS2 is also Vikas engine based liquid propulsion stage with propellant loading of 40 tons. The third stage uses cryogenic technology with engine delivering 75 kN thrust and stage propellant loading of 15 tons.

   In LVM3, the core stage, L110 is a liquid propulsion stage with twin Vikas engine delivering 1600kN thrust with stage propellant loading of 110 tons. The upper stage is an indigenously developed cryogenic stage C25 powered by CE20 engine developing 200 kN thrust with stage propellant loading of 28 tons.

2. What is cryogenic propulsion?

   Cryogenic propulsion system uses propellants which are stored at low temperatures, below 123K. The commonly used cryogenic propellants are liquid Hydrogen (fuel) and Liquid Oxygen (Oxidiser). The combination of liquid Oxygen (boiling point 90K) and Liquid Hydrogen (boiling point 20K) is used for rocket propulsion. The cryogenic propulsion has a specific impulse of 450s to 460s. This is high compared with 260s to 275 s of solid propellants, 280s to 315s of earth storable propellants and 300s to 350s of semi cryo propulsion. This high performance is the driving factor to use cryogenic engines in terminal stages of launch vehicles.

3. Propulsion system used in spacecrafts?

   The spacecraft is injected by the launch vehicle either in a low earth orbit or in a Geo-transfer orbit. Once injected into orbit, spacecraft require some form of propulsion throughout their operational life for numerous purposes. It is the spacecraft propulsion system that propels the spacecraft precisely in the desired orbit such as polar orbit, geosynchronous orbit etc.

   Moreover, the spacecraft propulsion system enables orienting the spacecraft in the orbit, controls and maintains the orbit and attitude as well as helps in manoeuvring the spacecraft on completion of end-of life.

   Majorly two types of propulsion system configurations, monopropellant system & bipropellant system are being used in various spacecraft missions of ISRO. Electric propulsion system is also being developed for spacecraft propulsion.

4. What is electric propulsion system?

   Electric propulsion system uses electrical energy for heating and/or directly ejecting propellant, utilizing an energy source that is independent of the propellant itself.

5. What are the major advantages of liquid propulsion system over the solid propulsion system?

   The liquid propulsion system offers many advantages compared to solid propulsion viz. a) higher specific impulse b) termination of thrust when desired c) thrust can be controlled through proper thrust management system and d) restart capability.

6. Where are the activities of LPSC undertaken?

   The LPSC activities and facilities are spread across its two campuses viz., LPSC Headquarters and Design Offices at Valiamala/ Thiruvananthapuram and Spacecraft Propulsion Systems development at LPSC, Bengaluru/Karnataka.

   LPSC Valiamala is the Centre Headquarters, primarily responsible for R & D, System Design/Engineering and Project Management functions.

   Various Entities engaged in design, development and realisation of Launch vehicle Earth Storable, Cryogenic and Semi-cryogenic propulsion systems, associated Fluid Control Components design and development, Propulsion research, materials development & manufacturing, mechanical design, system engineering etc. are located here.

   LPSC Bengaluru focuses on satellite propulsion. Design and realization of spacecraft propulsion systems, integration of spacecraft propulsion systems for ISRO's Remote Sensing, Communication, Navigation and Scientific spacecrafts, development and production of transducers / sensors are other major activities at LPSC, Bengaluru. Fabrication of launch vehicle stage tanks and structure at ASD/HAL is also coordinated and managed by LHWC at Bengaluru.