Propellant

noun (countable/uncountable); also adjective

/prəˈpɛlənt/

Any substance used to generate thrust in a rocket, missile, or projectile — either by controlled combustion (producing hot gas that expands through a nozzle to produce thrust per Newton's third law) or by direct expulsion. Rocket propellants are classified as solid (e.g., HTPB-based composite propellants used in ISRO's PSLV's strap-on boosters and DRDO's missile stages), liquid (e.g., cryogenic liquid hydrogen/liquid oxygen used in ISRO's GSLV Mk III C25 upper stage), or cryogenic/semi-cryogenic. In UPSC context, ISRO's indigenously developed cryogenic engine (CE-20) powering the LVM3/GSLV Mk III was critical to operational independence following the withdrawal of Russian cryogenic technology transfer in the 1990s under US pressure — a prominent GS3 case study in technology denial and self-reliance.

✍️ Usage in a UPSC answer

ISRO's decade-long development of the indigenous CE-20 cryogenic engine — burning liquid oxygen and liquid hydrogen at temperatures approaching minus 253°C — eliminated India's strategic dependence on imported cryogenic propellant technology and enabled the LVM3 to become a commercially competitive launch vehicle for global satellite missions.

Synonyms

fuelrocket fuelthrust agentcombustibleoxidiser (component)charge

Antonyms

retardantsuppressantinhibitor (in combustion context)

🌱 Word Family

propellant (n/adj), propel (v), propeller (n), propulsion (n), propulsive (adj), propellant grain (n phrase), cryogenic propellant (n phrase), solid propellant (n phrase)

🔡 Root

Latin propellere = to drive forward (pro- = forward + pellere = to drive/push); suffix -ant = one that performs the action

📜 Etymology

Derived from Latin propellere ('to drive forward'), with the agent suffix -ant (via French -ant). The word entered English in the 17th century in a general sense of 'something that propels'; its specific application to rocket fuels dates from the 19th century in early rocketry literature, and became standard with modern rocketry from the 1930s (Goddard, von Braun).

🧠 Memory Hook

PRO-PELLANT: pro- = forward, pellere = push. A propellant is a substance that pushes a rocket forward by pushing gas backwards — Newton's Third Law in a fuel canister. Remember ISRO's CE-20: the cryogenic propellant story is one of technology denial (US blocked Russia's transfer) and triumph through self-reliance.

📝 Seen in UPSC Question Papers

Prelims 2022 — Space Technology
Prelims 2014 — Defence Technology

Real UPSC previous-year questions whose text uses “Propellant” — proof this word earns its place on your list.

🔬 Science & Technology 📖 Seen in: Emerging Technologies — AI, Quantum Co...

Tip: press Alt+S to hear pronunciation