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.
Yemen (i/ˈjɛmən/; Arabic:اليَمَنal-Yaman), officially known as the Republic of Yemen (الجمهورية اليمنيةal-Jumhūrīyah al-Yamanīyah), is an Arab country in Western Asia, occupying the southwestern to the southern end of the Arabian Peninsula. Yemen is the second largest country in the peninsula, occupying 527,970km2 (203,850sqmi). The coastline stretches for about 2,000km (1,200mi). It is bordered by Saudi Arabia to the north, the Red Sea to the west, the Gulf of Aden and Arabian Sea to the south, and Oman to the east. Although Yemen's constitutionally stated capital is the city of Sana'a, the city has been under rebel control since February 2015. Because of this, Yemen's capital has been temporarily relocated to the port city of Aden, on the southern coast. Yemen's territory includes more than 200 islands; the largest of these is Socotra.
Yemen was the home of the Sabaeans (biblical Sheba), a trading state that flourished for over a thousand years and probably also included parts of modern-day Ethiopia and Eritrea. In 275 AD, the region came under the rule of the later Jewish influenced Himyarite Kingdom. Christianity arrived in the 4th century AD whereas Judaism and local paganism were already established. Islam spread quickly in the 7th century and Yemenite troops were crucial in the expansion of the early Islamic conquests. Administration of Yemen has long been notoriously difficult. Several dynasties emerged from the 9th to 16th century, the Rasulid being the strongest and most prosperous. The country was divided between the Ottoman and British empires in the early 20th century. The ZaydiMutawakkilite Kingdom of Yemen was established after World War I in North Yemen before the creation of Yemen Arab Republic in 1962. South Yemen remained a British protectorate until 1967. The two Yemeni states united to form the modern republic of Yemen in 1990.
The Yemen Arab Republic (YAR; Arabic:الجمهورية العربية اليمنيةal-Jumhūrīyah al-‘Arabīyah al-Yamanīyah), also known as North Yemen or Yemen (Sana'a), was a country from 1962 to 1990 in the northwestern part of what is now Yemen. Its capital was at Sana'a. It united with the People's Democratic Republic of Yemen, commonly known as South Yemen, on May 22, 1990, to form the current Republic of Yemen.
... against Yemen ... Saudi fighter jets also struck a water tanker as it was travelling on the road linking Saqin and Haidan districts of Yemen39;s northwestern province of Sa'ada ... Yemen has been under military strikes by Saudi Arabia on a daily basis since March 26.
Embassy in Yemen has forced the CIA to significantly scale back its counterterrorism presence in the country, according to current and former U.S ... counterterrorism operations in Yemen ... Embassy staffers left Yemen on private jets provided by Oman, flying to the Omani capital, Muscat, before traveling Wednesday to Washington.
Travel deals. SANAA, Yemen - (AP) -- A Yemeni military jet hit three trucks packed with weapons in a restive southern region on Tuesday, killing eight people including suspected al-Qaida militants, military and local officials said ...Washington considers Yemen's al-Qaida in the ...
Many of the passengers were travelling to the Comoros, but had begun their journey in Paris or Marseille on another jet operated by the national airline of Yemen, before boarding flight IY626 in Sanaa. 'Great relief' ...Officials from Yemen have previously said the plane had undergone a thorough inspection and conformed to international standards. .
Now scientists may have found the answer - a robotic jet ski that can see underwater and travel at speeds of up to 40mph ...Scientists hope a robotic jet ski that can see underwater and travel at speeds of up to 40mph will protect moored ships from terrorist attacks ... More problematic was redesigning the jet ski so that it can travel at a slow speed.
WASHINGTON—The foiled mail bombing plot by suspected al Qaeda militants in Yemen has added urgency to an Obama administration review of expanded military options that include putting elite U.S ... The other had traveled from San'a to Doha, Qatar, and then to Dubai aboard two separate passenger jets without detection ... Yemen's Jews From the Archive.
One of the two bombs mailed from Yemen and found on cargo jets in Dubai and Britain travelled on two passenger jets in the Middle East, according to a spokesman for Qatar Airways... Weather Forecasthttp.//www.telegraph.co.uk/news/uknews/terrorism-in-the-uk/8099937/Yemen-cargo-plane-plot-one-of-the-bombs-travelled-on-two-passenger-jets.html .
While the men might instead have been innocent victims of heightened suspicion about people traveling to Yemen, the incident is a reminder that more attention is now being paid to what is loaded in the cargo holds of American passenger jets than ever before ... cargo loaded onto jets ...
The prime suspect in the murder of a Norwegian student could be flushed from his Yemen hideout by international political pressure, her family said today ... Mrs Wadsworth said Abdulhak does have access to a private jet and there have been reports he has travelled outside Yemen.
Her friend Farouk Abdulhak, 22, is the prime suspect in the case, but he later flew to his native Yemen which has no extradition agreement with the UK ...Jet-set lifestyle ... The officer said Mr Abdulhak, who enjoyed a jet-set lifestyle, may be uncomfortable in Yemen where he is now effectively trapped.