挂载于B-52H轰炸机下的X-51A试验飞行器
据美国《航空周刊》网站2013年5月2日报道，美国空军研究实验室(AFRL)、波音公司X-51A“乘波者”试验飞行器5月1日成功进行最后一次试飞，实现了以吸气式超燃冲压发动机为动力的马赫数5持续高超声速飞行目标。
尽管空军没有提及飞行细节，X-51A被认为是产生了正向加速度并加速至马赫数5以上，而且持续完成了试验计划的有动力飞行阶段。本次飞行可能持续了300秒，随后在500秒左右飞行器开始无动力滑行下降，坠落在加州西部太平洋试验场的海域中。如果这些时间和速度数据被确认，这将是持续吸气式高超声速飞行的新记录。
X-51A目的是为了验证一种自由飞行、超燃冲压发动机驱动的飞行器的可行性，这被认为是高超声速武器和其它高速平台发展必须突破的阶段。然而，除了2010年5月份首飞取得部分成功，达到马赫数4.88之外，2011年3月和2012年8月进行的两次飞行都因出现故障而过早结束。因此，本次飞行成功对于空军继续开展后续研究以实现高超声速能力建设的长期目标至关重要。本次试验采用的是波音公司制造的四架飞行器中的最后一架，动力采用普?惠洛克达因SJX61双模态亚燃/超燃冲压发动机，发动机根据前三次飞行试验的经验和教训进行了改进。这些改进包括在发动机流道截面处采用更好的密封，防止重蹈首次飞行时燃气侵入到飞行器内部导致飞行过早结束的覆辙；此外，针对第二次试飞进气道未启动的故障进行了软硬件改进；最后，针对第三次试飞时飞行器控制翼面故障进行了改进。本次试验仍然采用了之前的任务模式，X-51A和改进的火箭助推器一起在B-52H飞行过程中释放，助推器完成任务后与X-51A分离，然后超燃冲压发动机点火工作。(中国航空工业发展研究中心 张东宝)
此次试验X-51A首次实现超过5马赫的持续飞行，速度达到5.1马赫，4分钟飞行了230海里（426 km）。
X-51A Waverider Achieves Hypersonic Goal On Final FlightBy Guy Norris
May 02, 2013
The U.S. Air Force Research Laboratory’s (AFRL) Boeing X-51A Waverider demonstrator successfully achieved sustained, scramjet-powered, air-breathing hypersonic flight above Mach 5 in its final test flight on May 1.
Although the Air Force is not yet commenting on details of the flight, the X-51A is thought to have experienced positive acceleration to speeds in excess of Mach 5 and run for the full duration of the planned powered phase of the test. Based on targets established for the previous test attempt, this could have been as long as 300 sec., followed by an unpowered gliding descent of around 500 sec. prior to impacting the sea in the Pacific Test range west of California. If these times and speeds are confirmed, they will represent new records for sustained, air-breathing hypersonic flight.
The X-51A is intended to prove the viability of a free-flying, scramjet-powered vehicle and is considered an essential building block toward the long-anticipated development of hypersonic weapons and other high-speed platforms. However, despite the partial success of the first flight, which reached Mach 4.88 under scramjet power in May 2010, that mission ended prematurely after a malfunction, as did the second flight in March 2011 and third in August 2012.
Coming in the wake of these disappointing prior tests, the success of the May 1 flight could therefore be pivotal in helping drive further research and development to meet the Air Force’s long-term goal of hypersonic capability. The test involved the last of the four vehicles to be built by Boeing and configured with a Pratt & Whitney Rocketdyne SJX61 dual-mode ramjet/scramjet engine, and incorporated improvements and lessons learned from the three former flights.
These included better sealing between interfaces in the engine flow-path that are thought to have suffered “burn-through” on the first flight, allowing hot gases to penetrate the vehicle’s interior and prematurely ending the flight. Additionally, it incorporated hardware and software changes to counter issues that brought the second flight to a premature end after only 9.5 sec. of powered flight at around Mach 5. On this flight, the vehicle experienced an inlet un-start during the switch to hydrocarbon fuel, effectively blocking flow through the engine and shutting it down. Finally, the mission also included changes to the hypersonic cruiser’s control fins, one of which failed on the third mission, causing it to go out of control only 16 sec. into the test while still under boost.
For the final test, as with previous missions, the X-51A, attached to a modified Atacms missile booster, was launched from a B-52H mother ship over the Pacific. The stack separated from the B-52 and the booster fired as planned before the Atacms burned out and detached, and the scramjet ignited.
X-51A由B-52H轰炸机载至太平洋上空进行测试
X-51A's Record-breaking Hypersonic MilestonePosted by Guy Norris 12:30 PM on May 03, 2013
The U.S. Air Force has released new details of the record-breaking hypersonic test flight conducted by the Boeing-built X-51A Waverider demonstrator on May 1. The diminutive scramjet-powered vehicle achieved a blistering Mach 5.1, covering 230 naut. miles in just over six minutes over the Point Mugu Naval Air Warfare Center Sea Range in the Pacific.
The success of the flight, which included 240-seconds of powered flight in scramjet mode – the longest ever achieved by an air-breather, is particularly important to the Air Force as it seeks to develop a hypersonic capability. Interest in high-speed, long range strike weapons which can fly at hypersonic speeds grew in the 2000s with the requirement to prosecute fleeting targets in counter-terrorism operations, and is assuming fresh importance with the strategic ‘pivot’ to Asia. Although the Air Force says there is no immediate successor to the X-51A program, it adds work on the technology demonstrator “will pay dividends to the High Speed Strike Weapon program currently in its early formation phase with AFRL.”
The May 1 flight was also the fourth, and final, chance to achieve the full mission targets of the $300 million X-51A effort which began in 2004 with the aim of proving the viability of air-breathing, high-speed scramjet propulsion. The first mission, two years ago, achieved partial success when it reached Mach 4.88 under scramjet power in May 2010, but both this mission and the second and third flights in March 2011 and August 2012, ended prematurely after various malfunctions.
The last of the four vehicles that was tested on May 1 incorporated improvements and lessons learned from the three former flights. These included better sealing between interfaces in the engine flow-path that are thought to have suffered “burn-through” on the first flight, allowing hot gases to penetrate the vehicle’s interior and prematurely ending the flight. Additionally, it incorporated hardware and software changes to counter issues thought to have brought the second flight to a premature end after only 9.5 sec. of powered flight at around Mach 5. On that flight the vehicle experienced an inlet un-start during the switch to hydrocarbon fuel, effectively blocking flow through the engine and shutting it down. Finally, the mission also included changes to the hypersonic cruiser’s control fins, one of which failed on the third mission, causing it to go out of control only 16 seconds onto the test while still under boost.
Attached to its modified ATACMS booster, the X-51A cruiser was carried aloft under a B-52H and released at about 50,000ft over the Pacific. The booster accelerated the stack to Mach 4.8 in 26sec. The cruiser then separated and ignited its hydrocarbon-fueled scramjet engine. The fuel-cooled scramjet burned for 240sec, exhausting its fuel supply, then the vehicle coasted to a watery demise in the Pacific. In all, about 370sec of flight data was collected, during which time the cruiser traveled more than 230nm.
Of the four flights in the $300 million program, this was the first full success. The first flight in May 2010 was a partial success, the scramjet burning for more than 200sec and the vehicle reaching Mach 5 before a leaking nozzle seal caused it to lose control. The second flight ended early when an inlet unstart prevented the scramjet from igniting successfully. The third flight in April 2012 ended 15sec after the cruiser separated from the booster, after a control fin malfunction.
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Video: Boeing
