Ahead of Gaganyaan, ISRO’s CE-20 engine already has a notable legacy
- February 26, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
Ahead of Gaganyaan, ISRO’s CE-20 engine already has a notable legacy
Subject: Science and tech
Section: Space Sector
What is Gaganyaan: The Gaganyaan Mission is India’s ongoing project to send a 3-day manned mission to the Low Earth Orbit (LEO) of 400 km with a crew of 3 members and bring them safely back to Earth.
Preferred fuels for rocket motors:
- Engineers prefer to use liquid fuels because they are less bulky and flow better than solid fuels.
- Hydrogen as fuel is also desirable because on combustion it generates the highest exhaust velocity.
Comparison:
- For example, combusting hydrogen with oxygen results in an exhaust velocity of 4.5 km/s.
- With unsymmetrical di methyl hydrazine and nitrogen tetroxide — the combination used by the second stage of the PSLV rocket, e.g. — is around 3.4 km/s.
- Thus, hydrogen is a desirable fuel for rocket motors.
Cryogenic engine:
- It uses propellants at extremely low temperatures.
- It uses liquid fuels (Oxygen liquifies at -183 deg C and Hydrogen at -253 deg C) that are cooled to very low temperatures.
- A 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.
- It requires special equipment to store and transport liquid hydrogen and special engines to power a rocket.
Three Cryogenic Engines of ISRO:
- KVD-1, CE-7.5, and CE-20.
- CE-7.5 and CE-20 are India-made. Although the design of the CE-7.5 is based on the KVD-1 supplied by Russia (as the Soviet Union) in the early 1980s.
- The GSLV Mk lII launch vehicle uses CE-7.5 engines to power the third stage of its ascent.
A cryogenic engine operation requires a cryopump, special storage tanks and turbopumps.
Cryopump is a device to trap and cool the hydrogen and oxygen to liquid form.
Turbopump is required to move the cooled fuel and oxidiser to the engine.
The CE-7.5 engine:
- It uses the staged-combustion cycle.
- In a pre-burner, a small amount of the fuel is combusted.
- The resulting heat drive the turbine to power the turbopump.
- Once the turbopump brings the rest of the fuel and oxidiser to combustion chamber
- Then hydrogen is combusted to power main engine plus two vernier thrusters.
- The exhaust from the pre-burner is also routed to the combustion chamber.
CE-20 Engine:
- It uses the gas-generator cycle
- It discards the exhaust from the pre-burner instead of sending it to the combustion chamber.
- This reduces fuel efficiency
- The CE-20 engine is easier to build and test.
- ISRO has dropped vernier allowing the engine’s nozzle to make small rotations or gimbal to adjust the rocket’s flight path.
- Thus, CE-7.5 engine is lighter and have higher fuel-use efficiency.
- The CE-20 engine achieves a higher maximum thrust (~200 kilonewton v. 73.5 kilonewton) with a shorter burn duration.
Mission using CE-20 Engine:
- LVM-3 rockets using the CE-20 in the third stage (the first stage: two solid-fuel boosters and the second stage: two liquid-fuelled Vikas 2 engines ) have already launched
- Chandrayaan-2 mission
- Chandrayaan-3 missions
- The 5.8-tonne payload of the commercial One Web mission in 2022.
- Upcoming: The first uncrewed Gaganyaan test flight (G1) which is tentatively scheduled for mid-2024.
LVM-3: Launch Vehicle Mark-3
- The LVM-3 has 3 stages:
- The first stage is in the form of 2 S200 boosters straps to the sides of the rocket body; combust a solid fuel called hydroxyl-terminated polybutadiene.
- The second stage is powered by Vikas Engines (combust a liquid fuel) either nitrogen tetroxide or unsymmetrical dimethylhydrazine.
- The final stage is Powered by a cryogenic engine. It combusts liquified hydrogen with liquified oxygen.
LVM-3 capabilities:
- It can lift up to eight tonnes.
- It is launched in low-earth orbit
- It is the vehicle of choice for the first Gaganyaan mission,
- It improves India’s self-sufficiency vis-à-vis launch capabilities
- Its launch costs are low.
What is human-rating:
Human-rating entails processes to verify particular errors like the failure of a particular component, happen at less than a particular rate.
ISRO’s human-rating tests:
- to ISRO -The four CE-20 engines had been hot-fire tested for a cumulative 8,810 seconds against the minimum human rating qualification standard requirement of 6,350 seconds.
- In a cold-flow test, fluids flow through the engine but have no combustion or exhaust, whereas combustion or exhaust is present in hot-fire test.