Context: 

Recently, the Indian Space Research Organization (ISRO) successfully conducted the hot test, also known as the Power Head Test Article (PHTA), on a semi-cryogenic engine (SE2000).

About the Semi-Cryogenic Engine (SE2000):

• Semi-cryogenic propellants involve a cryogenic oxidizer (usually liquid oxygen (LOX)) and a non-cryogenic fuel refined kerosene (RP-1).
• This fuel combination provides a balance between the high performance of cryogenic propellants and the easier handling and storage requirements of non-cryogenic propellants like liquid hydrogen.
• It offers advantages like high-density impulse (with respect to cryogenic), less toxic (with respect to storage) and cost-effectiveness.
• This semi-cryogenic engine offers an enhanced thrust of 2,000 kilonewtons (kN).

Power Head Test Article (PHTA):

PHTA is a significant precursor test done to validate the integrated performance of the engine’s critical subsystems, such as the gas generator, turbo pumps, pre-burner and control components.

It is the first hardware test for the development of semi-cryogenic engines.

PHTA involves performing a hot-firing for an extremely brief duration of not more than 4.5 seconds.

This test is instrumental in going a step closer to finalising the crucial cryogenic stage where powering the booster stages of launch vehicles is realised. 

• The cryogenic stage is the last stage of space launch vehicles where they use Cryogenics to store its fuel and oxidiser as liquids instead of gas.
• Cryogenics is the study of the production and behaviour of materials at extremely low temperatures (below -150 degrees Centigrade) to lift and place heavier objects in space.

In July 2023, a similar test attempted at the space agency’s facility at Mahendragiri had to be aborted due to a technical glitch.

Significance of the Semi-cryogenic Engine

• Semi-cryogenic engines enable the successful accomplishment of various missions such as deep space expeditions, upper stages deployment, and launching spacecraft into orbit etc.
• Semi-cryogenic rocket engines are instrumental in propelling a rocket's first stage intended for lifting a spacecraft beyond Earth's atmosphere.
• The higher density of kerosene compared to liquid hydrogen allows for smaller fuel tanks while maintaining high thrust, leading to a more efficient and compact design.
• ISRO is looking to replace the liquid core (L110) engine of the Geosynchronous Satellite Launch Vehicle Mk III (GSLV MK III) with a semi-cryogenic engine to boost the rocket’s payload capacity from four to six tonnes.