Afterburner

Afterburner (pronounced af-ter-bur-ner)

(1) In aviation, a device placed within, or attached to the exit of, a jet-engine exhaust pipe to produce afterburning.

(2) In engineering, a device in the exhaust system of an internal-combustion engine for removing or rendering harmless potentially dangerous components in the exhaust gases.

1948: A compound word, the construct being after + burn +-er.  The verb after developed from its use as an adverb and preposition, from the Middle English after-, efter- & æfter-, from the Old English æfter- (after, behind, against; later in time; in pursuit, following with intent to overtake), the idea being off + -ter (a comparative suffix), the original formation meant "more away, farther off”.  It was cognate with the Scots efter-, the Old Frisian & West Frisian efter-, the Dutch achter-, the German after-, the Swedish efter, the Old Norse eptir, the Old High German aftar, the Gothic aftra (behind), the Greek apotero (farther off) and the Old Persian apataram (further).  From circa 1300 it assumed the meaning "in imitation of; in the style of" while, as a conjunction in the sense of "subsequent to the time that" the use was inherited from the late Old English.  The phrase “after hours” (hours after regular working hours) dates from 1814 although the exact purpose has always proved elusive but it’s assumed by most to relate to retail commerce rather than terms of employment.  Afterwit was from circa 1500 and deconstructs literally as "wisdom that comes too late" but is familiar feeling of one for whom a perfect piece of repartee comes to mind only after the moment has passed; it’s perhaps surprising afterwit didn’t endure in the language.  The phrase “after you” an element in etiquette meaning “yielding precedence to another” dates from 1650.

Burn was from the Middle English bernen & birnen, from the Old English birnan (to burn), a metathesis from the Proto-West Germanic brinnan, from the Proto-Germanic brinnaną (to burn), from the primitive Indo-European bhrenw- and related to the Middle Irish brennim (drink up) & bruinnim (bubble up), the present stem from bhrewh- & bhru- (linked to the Middle Irish bréo (flame), the Albanian burth, the Cyclamen hederifolium (mouth burning) and the Sanskrit भुरति (bhurati) (moves quickly, twitches, fidgets).  The verb was from the early twelfth century brennen (be on fire, be consumed by fire; be inflamed with passion or desire, be ardent; destroy (something) with fire, expose to the action of fire, roast, broil, toast; burn (something) in cooking) which when applied to objects imparted the sense of “to shine, glitter, sparkle, glow like fire”, the form from both the Old Norse brenna (to burn, light) an two originally distinct Old English verbs: the transitive bærnan (to kindle) and the intransitive beornan (be on fire).  All of these were from the Proto-Germanic brennanan (causative brannjanan), source also of the Middle Dutch bernen, the Dutch branden, the Old High German brinnan, the German brennen, the Gothic brannjan (to set on fire); the ultimate etymology uncertain.  The noun burn dates from circa 1300 in the sense of "act or operation of burning” and was from the Old English bryne, the etymology identical to the verb and prior to the mid-sixteenth century, the usual spelling was brenne.

The Figurative use of burn (of passion, conflict etc.) was in Old English and survives to this day while the literal sense of "be hot, radiate heat" was from the later thirteenth century, the meaning "produce a burning sensation, sting" from a hundred years later.  A further figurative sense, that of "being cheated, swindled or victimized" emerged in the 1650s on the notion that whatever one lost “may as well have been burned”.  The slang use of burned from the late eighteenth century meaning "infected with venereal disease" referred to the sensation which was one of the symptoms.  To “burn one's bridges (behind one)” meant "behave so as to destroy any chance of returning to a status quo" and was used in the late nineteenth century, perhaps because of some of the reckless cavalry operations documented during the US Civil War although it’s a variation on the “burn the boats” (so one’s soldiers have no alternative but to fight, there being no chance of escape) approach known since Antiquity.  To have money “burn a hole in (one's) pocket” was a critique from the 1850s of those with an irresistible propensity to spend whatever money was in one’s possession; the modern expression of economists is of “expenditure rising to meet income”.  The meaning "mark or injury made by burning" is from 1520s while “slow burn” dates from 1938 and refers to a technique in acting.

The –er suffix was from the Middle English –er & -ere, from the Old English -ere, from the Proto-Germanic -ārijaz, thought usually to have been borrowed from Latin –ārius and reinforced by the synonymous but unrelated Old French –or & -eor (the Anglo-Norman variant was -our), from the Latin -(ā)tor, from the primitive Indo-European -tōr.  The –er suffix was added to verbs to create a person or thing that does an action indicated by the root verb; used to form an agent noun.  If added to a noun it usually denoted an occupation.

The afterburner

Attracted by theoretical work which hinted at improved thrust, Rolls-Royce began ground tests on one of their early jet engines in 1944 although the war ended before the technology was ready for production.  By the early 1950s, most advanced jet fighters had adopted afterburners and they continue generally to be used mostly in military aircraft although a few civilian applications have existed including the now defunct Tupolev Tu-144 and Concorde.

An afterburner’s purpose is to provide an increase in thrust, usually for supersonic flight, takeoff and in combat. Afterburning is achieved by injecting additional fuel downstream of the turbine and produces significantly increased thrust; the trade-off being very high fuel consumption and inefficiency, though this is considered acceptable for the short periods during which it is usually used.  The quantum of a jet-engine’s thrust is determined by the general principle of mass flow rate and thrust depends on two things: the velocity of the exhaust gas and the mass of that gas. A jet engine can produce more thrust by either accelerating the gas to a higher velocity or by having a greater mass of gas exit the engine.  Designing a basic turbojet engine around the second principle produces the turbofan engine, which creates slower gas but more of it. Turbofans are highly fuel efficient and can deliver high thrust for long periods, but the design trade-off is a large size relative to the power output. To generate increased power with a more compact engine for short periods, an engine requires an afterburner. The afterburner increases thrust primarily by accelerating the exhaust gas to a higher velocity.

Lockheed SR-71 Blackbird afterburning for additional thrust during take-off (left) and Royal Australian Air Force (RAAF) General Dynamics F-111 Aardvark performing a dump-and-burn (right).

What many people think of as afterburners are actually displays of dump-and-burn at air shows, a procedure where dumped fuel is intentionally ignited using the plane's afterburner. A spectacular flame combined with high speed makes this an interesting sight but it’s just for entertainment.  Fuel dumping is used to reduce the mass of an aircraft about to undertake emergency landings and thus, for other than for safety reasons, dump and burn has no practical use.  In the slang of pilots who flew the early generation of fighters with afterburners the phrase was "lit up the burners" while the dump and burn is also called a "torching" or a "zippo".

Lighting up the burners: Lindsay Lohan in The Canyons (2013).