ROCKET

any of the 90 species of the genus Sisymbrium, of the mustard family (Brassicaceae), weedy plants with yellow flowers that are common in waste areas and fields of the Northern Hemisphere and mountains in the Southern Hemisphere. Rockets have long, thin seedpods and usually coarse, deeply cut, dandelion-like leaves. Eastern rocket (S. orientale), a European annual 30 to 60 cm (1 to 2 feet) tall, has long pods and clusters of small flowers at the stem tip. Hedge mustard (S. officinale), a Eurasian species with pods close to the stem, is naturalized in North America. The name rocket is also given to Barbarea vulgaris (see winter cress). any of a type of jet-propulsion device carrying either solid or liquid propellants that provide both the fuel and oxidizer required for combustion. The term is also commonly applied to any of various vehicles, including firework skyrockets, guided missiles, and spacecraft launch vehicles, driven by such a propulsive device. any of a type of jet-propulsion device that carries either solid or liquid propellants that provide both the fuel and oxidizer required for combustion. The term is also commonly applied to any of various vehicles, including firework skyrockets, guided missiles, and spacecraft launch vehicles, driven by such a propulsive device. Typically, thrust (i.e., forward motion) is produced by reaction to a rearward expulsion of hot gases at extremely high velocity. Rockets are treated in a number of articles in the Macropaedia. For treatment of rocket propulsion, see Energy Conversion: Rockets; for treatment of spacecraft launch vehicles, see Exploration: Space exploration; for treatment of military rockets and guided missiles, see War, The Technology of: Rockets and missile systems.