Gurtsler Engine

KAYLEE: You wanna shake, sail the PARAGON there. Guarantee you'll barf before you break atmo.
BOOK: They can dress her up pretty, but a Gurtsler engine's always gonna get twitchy on ya.
-- Serenity Pilot

A type of propulsion engine used on space ships. The company apparently makes its profit through government contracts, as Kaylee mentions in Bushwhacked that the Alliance cruisers use a number of these types of engines. (A half-dozen mounted under each Cooling Drive, in fact.)