Lockheed Martin has begun work on a successor to the supersonic Blackbird SR-71 spy plane.
The unmanned SR-72 will use an engine that combines a turbine and a ramjet to reach its top speed of Mach 6 - about 3,600mph (5,800km/h).
Like its predecessor, the SR-72 will be designed for high-altitude surveillance but might also be fitted with weapons to strike targets.
Lockheed said the aircraft should be operational by 2030.
Jet engines
The SR-72 is being developed at Lockheed Martin's Skunk Works R&D centre in California that designed and built the original Blackbird.
That aircraft first flew in 1964 and was a mainstay of US Air Force spying and surveillance work until 1998. It typically flew at altitudes of 24,000m (80,000ft) and could reach speeds of Mach 3.
In a blogpost about the SR-72, Lockheed Martin said the aircraft would operate at similar altitudes but would fly far faster. At Mach 6 the plane could travel the 3,500 miles (5,500km) from New York to London in less than an hour.
While spy satellites can photograph enemy territory, the relatively long time it takes for them to be moved to a new orbit so they pass over a target can limit their usefulness.
By contrast, wrote Lockheed Martin, the SR-72 "would be so fast, an adversary would have no time to react or hide".
For the SR-72, Lockheed Martin is drawing on work done on the Falcon HTV-2 hypersonic technology vehicle. This is a test-bed for the futuristic technologies needed to support safe hypersonic flight and cope with the extreme conditions encountered by any object flying at such a speed.
For instance, on one test flight of the HTV-2, the aircraft hit a top speed of Mach 20 and its flight surfaces reached 1,927C (3,500F).
To reach Mach 6, the SR-72 will use an engine that acts like a normal jet turbine until speeds of Mach 3 are reached but which then operates like a ramjet to accelerate beyond that.
"Speed is the next aviation advancement to counter emerging threats in the next several decades," said Brad Leland, Lockheed Martin's hypersonic programme manager on the blog. "The technology would be a game-changer in theatre, similar to how stealth is changing the battlespace today."
据英国广播公司等媒体11月4日报道，美国国防工业巨头洛克希德已经着手打造将以六倍音速飞行的新一代无人侦察机“黑鸟之子”——SR－71“黑鸟”间谍飞机的下一代。
洛克希德表示，第二代“黑鸟”将于2030年投入使用，以速度而非隐形能力取胜。与其前任一样，SR－72间谍机既能用于高空侦查和监视，也能装配其他武器用于打击目标。
60年代初，在U-2侦察机在苏联上空被地对空导弹击落后，洛克希德开始研制第一代“黑鸟”。1976年，美国空军飞行员驾驶“黑鸟”不到两个小时便从纽约飞抵伦敦，飞行速度超过3马赫，创下世界纪录。
第一代“黑鸟”直到1998年一直为美国空军侦 查和监视行动的中坚力量。它能翱翔在2.4万米的高空，飞行速度达到3马赫。不仅比地对空导弹飞的更快，“黑鸟”还可以通过低空飞行规避敌方雷达。在建造 的32架“黑鸟”侦察机中，12架因事故折戟沉沙，但无一架毁于敌军火力。
洛克希德·马丁强调，无人驾驶的新一代“黑鸟”继承上一代的飞行高度，但能飞得更快，最高速度可达6马赫“极超音速”，约为5,800公里／小时，为SR-71速度的两倍，堪称美军侦察和突袭奇兵。
“极超音速飞机，外加极超音速导弹，不用一小时即可打击任何跨大洲目标，”洛克希德·马丁公司高超声速经理布拉德·利兰说，“为应对未来数十年将产生的威胁与挑战，我们需要提高飞行速度。正如昨日的隐身技术改变今日的战场一样，今日的技术变革将改变明日的战场规则。”
间谍卫星虽然也能拍摄敌方领土，但由于需要花较长时间将他们移入新轨道以监视整个目标，因此间谍卫星的使用常常受限。SR－72间谍机则不同，其飞行速度之快，以致于敌人没有时间反应或躲藏。