Vocabulary Builder — Essay & Answer Writing
Specific Impulse
A measure of rocket engine efficiency — the thrust produced per unit weight flow of propellant consumed per second; higher specific impulse means more payload can be carried with less fuel.
Latin specificus (particular) + impulsus (a push) — technical aeronautical engineering term
"ISRO's CE20 cryogenic engine achieves approximately 440 seconds of specific impulse in vacuum — the highest of any chemical propellant pair — which is why cryogenic engines are essential for placing heavy satellites in geostationary orbit."
Frequently tested in UPSC Prelims Science & Technology questions on space. The key fact: cryogenic engines have the highest specific impulse (~440 seconds) among chemical propulsion systems; solid fuel has ~250 seconds; liquid storable propellants ~300 seconds. This is why India's Gaganyaan mission uses the CE20 cryogenic engine on LVM3. Also important for understanding why the US denied cryogenic technology to India in 1994 — MTCR concerns about dual-use for ballistic missiles.