Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, jet engines and aircraft achieve maximum efficiency (see specific impulse) at speeds close to or even well above the speed of sound. Jet aircraft generally cruise at faster than about M 0.8 (609mph, 981km/h or 273m/s) at altitudes around 10,000–15,000 metres (33,000–49,000ft) or more.
Frank Whittle, an English inventor and RAF officer, developed the concept of the jet engine in 1928,Hans von Ohain in Germany, a decade later developed the concept independently at the end of the 1930s. He wrote in February 1936 to Ernst Heinkel, telling him of the design and its possibilities. However, it can be argued that the English engineer A. A. Griffith, who published a paper in July 1926 on compressors and turbines, also deserves credit.
Vanuatu (English i/ˌvɑːnuːˈɑːtuː/vah-noo-AH-too or /vænˈwɑːtuː/van-WAH-too; Bislama IPA:[vanuaˈtu]), officially the Republic of Vanuatu (French:République de Vanuatu, Bislama: Ripablik blong Vanuatu), is a Pacificisland nation located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is some 1,750 kilometres (1,090mi) east of northern Australia, 500 kilometres (310mi) northeast of New Caledonia, east of New Guinea, southeast of the Solomon Islands, and west of Fiji.
Vanuatu was first inhabited by Melanesian people. The first Europeans to visit the islands were a Spanish expedition led by Portuguese navigator Fernandes de Queirós, who arrived on the largest island in 1606. He then claimed the archipelago for Spain, as part of the colonial Spanish East Indies, and named it Austrialia del Espiritu Santo.
In the 1880s, France and Great Britain claimed parts of the archipelago, and in 1906 they agreed on a framework for jointly managing the archipelago as the New Hebrides through a British–French Condominium. An independence movement arose in the 1970s, and the Republic of Vanuatu was founded in 1980.