دانلود کتاب اف-۳۵ در خدمت نیروهای هوایی سراسر جهان

During the 1980s the United Kingdom and the USA had co-operated on supersonic Short-Take-Off-and-Vertical-Landing (STOVL) fighter studies to replace the Harrier. In 1986 NASA and the USMC, among others, asked if DARPA could help out the stalled programme. DARPA got involved and the work performed from 1986 till 1992 is considered phase 1. DARPA (Defense Advanced Research Projects Agency) issued a request for proposals (Rf P) for the ASTOVL (advanced-short-take-off-and-verticallanding) aircraft technology demonstration programme in 1992. The aim was to build a supersonic STOVL fighter with an empty weight of 24,000lb, similar to the F-18C, to keep weight and cost in check. The cost of a fighter was its weight in gold, US$1,500 per pound in 1993. Since then the cost of gold has increased As the United States Marine Corps (USMC) had trouble with the Bell Boeing V-22 Osprey which was under attack by US Vice President Dick Cheney, they could not afford another high-profile programme on their own. United States Air Force (USAF) Brigadier General George Muellner, deputy chief of staff for requirements, Headquarters Air Combat Command, Langley Air Force Base, received a presentation from Lockheed/ DARPA about a replacement for the F-16 with more range, the kind of range the USAF craved, after he objected that the USAF had no money to start another project since they had the F-22 just about selected. The financial situation was tight: everyone expected a peace dividend after the collapse of the USSR just a couple of years before and did not want to put budgetary pressure on the F-22 programme. DARPA pointed out that the USMC had a similar problem and that there could be a possibility of co-operation as the extra fuel tank could be replaced by a lift fan offering a supersonic capability for which the USMC yearned. The USAF was interested in this DARPA programme to provide the technology by the end of the 1990s. Many had tried to develop a supersonic STOVL fighter but had failed. The history books are full of examples of experiments that were imaginative, but problems such as hot-gas ingestion, suck-down forces and the fountain forces made them unsuccessful. Hot-gas ingestion and the transition from conventional flight to hover and lifting its weight had proved to be the three biggest problems in developing a successful supersonic STOVL fighter. For this reason, DARPA assigned an experimental X designation to the prototype, the X-32. General Dynamics had been testing a full-scale E-7 ejector propulsion model in the NASA 80 x 120-feet wind tunnel but, in the end, offered a fanin- wing propulsion concept similar to that of the Ryan XV-5A. McDonnell Douglas went in with an offer for both shaft-driven-lift-fan (SDLF) and gas-coupled-lift-fan (GCLF) propulsion systems. Northrop offered a similar propulsion system as used in the Russian Yakovlev Yak-38, the lift+liftcruise propulsion system. Boeing offered the Harrier propulsion system called direct lift. The Lockheed and McDonnell Douglas designs could remove the lift fan for the conventional fighter and Northrop could do the same with the lift engine. Only Boeing did not have this advantage and, for that reason, selected a delta wing which can hold a larger fuel volume. A requirement set by DARPA was that a full-scale model had to be developed to prove that a design could carry its weight in the STOVL flight regime to prevent a repeat of the Rockwell International XVF-12A.