RAS question
Which fuel combination does the Cryogenic Upper Stage of GSLV Mk III use?
Correct answer: (B) Liquid hydrogen and liquid oxygen.
The Cryogenic Upper Stage (C25) of GSLV Mk III uses liquid hydrogen as fuel and liquid oxygen as oxidiser.
Explanation
GSLV Mk III's cryogenic upper stage is the C25 stage. ISRO describes it as its most powerful upper stage and states that it uses a Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) propellant combination. In this pairing, liquid hydrogen is the fuel and liquid oxygen is the oxidiser. This cryogenic combination gives the highest specific impulse among chemical propellants, which is why it is used in the upper stage rather than a solid or earth-storable propellant system. ISRO also identifies C25 as the cryogenic upper stage of GSLV Mk III, so the fuel combination is not a generic cryogenic fact but the specific C25 configuration.
Why the other options are wrong
- (A) Kerosene and liquid oxygen is associated with launch vehicles such as Falcon 9, not with GSLV Mk III's C25 cryogenic upper stage.
- (C) UDMH and nitrogen tetroxide are used in the Vikas engine core-stage context, while ISRO identifies the C25 upper stage as LOX-LH2.
- (D) Solid hydroxyl-terminated polybutadiene is a solid booster propellant, whereas the C25 stage is a liquid oxygen and liquid hydrogen cryogenic stage.
Concept
Launch-vehicle propulsion depends on the distinction between solid, earth-storable liquid and cryogenic stages. RAS Science and Technology often requires stage-wise ISRO propellant matching as the key factual check.