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(詳細はLockheed Martin RQ-3 DarkStarを参照) The Gnat 750 and Predator were the first in a series of "Tier UAVs" considered by the US Air Force. In the USAF plan, the Gnat 750 was known as "Tier 1", while the Predator was known as "Tier 2". The original expectation was that the series would then move on to a very large and powerful long-range UAV known as "Tier 3", something along the lines of a B-2 Stealth bomber, but Tier 3 proved overambitious and was cancelled. In place of Tier 3, the USAF decided to develop a smaller "Tier 3-" UAV designated the "Darkstar", and a "Tier 2+" UAV, something like a "super Predator", the Teledyne-Ryan "Global Hawk". The Lockheed Martin / Boeing Tier 3- Darkstar was a stealthy design that resembled a big pumpkin seed with a long straight wing at the rear. It was to send real-time still images produced by either SAR or EO sensors, though it didn't have the capacity to carry both sensors at the same time. Data was to be returned using a satellite communications link with a bandwidth of 1.5 megabits per second. The Darkstar was intended to penetrate protected airspace to observe high-value targets for a limited amount of time. Range and endurance were intended to be similar to that of the Predator, though the Darkstar's sensor suite could cover over twice the area, and of course it was harder to detect. The Darkstar was powered by a Williams Research FJ-44-1A turbofan engine with 8.46 kN (862 kgf / 1,900 lbf) thrust, and could carry a 450 kilogram (1,000 pound) payload. The UAV was to cost about $10 million USD each. The Darkstar was unlucky. On its second takeoff in the spring of 1996, it stood up on one wing and slammed into the runway, bursting into fire and smoke. An analysis of the failure showed flight software and takeoff procedures to be faulty. The Air Force and the contractors didn't give up right away, and a redesigned Darkstar, now formally designated "RQ-3A", flew in the early summer of 1998. However, the program was still unhealthy, and the Darkstar was cancelled in early 1999. Although flight tests were generally satisfactory, the Darkstar was by no means close to being a useful operational system. Building an actual operational UAV based on the Darkstar would have required major redesign and improvement, and the costs were more than the Air Force was willing to spend. * At least that was what the official line was. In the summer of 2003, confirming rumors that had been in circulation for some time, Air Force officials announced that Lockheed Martin's "Skunk Works" had developed several prototypes of a stealthy reconnaissance UAV similar to the DarkStar but larger, and that this machine had been used in an operational evaluation over Iraq during the American invasion of that country in the spring of 2003. The unnamed UAV's payload was described as less than that of a Lockheed U-2, featuring a "low probability of intercept (LPI)" SAR and electro-optic sensors, along with a satcom datalink. Range was less than that of the Global Hawk, described below, though cost is described as several times greater. The Air Force wanted to conduct the operational evaluation to see if putting the new machine into production was worthwhile. The most likely operational base for the UAV was Al Udeid Air Base in Qatar, which has extensive and well-developed facilities, is near to Iraq, and was off-limits to reporters during the invasion of Iraq. Sources have also leaked information about a roughly comparable Boeing effort to develop a stealth UAV test bed. This particular machine is said to have been flown in a wide range of configurations, with different tails, noses, and wings, to validate stealth concepts. This UAV was declassified in 2006 as the Lockheed Martin Polecat. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Modern US endurance UAVs」の詳細全文を読む スポンサード リンク
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