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2024年8月23日发(作者：运亮)

美军X-43

改装后携带X-43A试验飞机的B-52轰炸机

携带着X-43A试验飞机的B-52轰炸机

X-43A飞机以冲压喷气引擎发动，机长3.7米，外形为黑色，最高速度将

为7马赫，即每小时近8047公里，相当于音速的7倍，由美国东岸至西岸只需

半小时的飞行时间。马赫是音速的单位，依轨道高度而稍有差异，海平面上一马

赫相当每小时1200公里。1967年10月，一架以火箭推动的X-15型飞机曾创下

6.7马赫的纪录。

在去年的5月份，X-43A超高速飞机将在今年从加利福尼亚州的爱德华兹空

军基地进行第一次无人驾驶的遥控试飞任务。为确保试飞时气流速度够快，

NASA将用一架B-52型轰炸机把配组有“飞马”助推火箭的X-43A载到7200米

的高空，然后释放。接着，“飞马”助推火箭把X-43A推进到7马赫速度后脱落，

X-43A再点燃自身的引擎，飞行10秒、大约27公里，然后坠入太平洋。落海时

的撞击力会把X-43A的设计机密彻底摧毁。试飞所得的空气动力学数据，将作

为下次试飞和改良设计之用。如果一切顺利，今后两年之内，X-43将进行三次

不同性质的试飞来检验这种所谓“超高音速引擎”的性能。NASA科学家称，他们

到目前为止已为这个项目投入了2亿美元，但真正用于太空航行还得等25年。

届时，真正意义上的超高速飞机体长将达60米，能通过跑道自行升降，飞行速

度最后能高达10马赫以上，从而为人类航空史揭开新的一页。

航空技术上的“惊人一跃”

无人驾驶飞行器X-43A是NASA“极速X(HyperX)”计划的一部分，也是“高

超音速”系列的头一炮。所谓“高超音速(hypersonic)”，是指达到音速5倍(5马赫)

或以上。高超音速飞行有一大难题：普通引擎的叶片会碎毁。因此X-43A采用

的是“超音速燃烧冲压式喷气引擎”(supersoniccombustionramjet?，简称Scramjet。

它没有涡轮引擎般的叶片或移动组件，基本上就是一条一体成型的空管子，当飞

行器飞行的速度足够时，被推逼进入机内的空气就被压缩，空气中的氧气与氢气

这时就会混合燃烧，产生强大的推动力。但这种发动机只排出水，而并无其他废

气。

X-43A将由其改进的神马推进器来推动，由B-52飞机在40000英尺的高空

释放，由推进器以7马赫的速度推进到95000英尺的高度。当推进器燃烧完毕后，

X-43A将会同推进器分离依靠自己的能量按照预定的程序进行飞行试验。

目前，全球使用一般空气助燃的涡轮喷气引擎的飞机中飞得最快的是美国空

军的SR-71“黑鸟”侦察机，速度可达3马赫。科学家认为，配备冲压喷气引擎的

飞机，其速度几乎有无限的可能，但也承认应用该技术的飞行器要多年以后才能

面世。

美国数十年来都是研究以火箭引擎推动高超音速飞机，但X-43A却突破性

地推翻了过去的研究。火箭引擎由于要携带氧气以助燃，会增加机身重量，但

X-43A却使用大气层中的氧气来助燃，可说是一大改良，飞行成本因而会大大降

低。

军事霸权的“利刃”

美国国防部试验无人驾驶飞机已达半个世纪之久，只是到现在才真正发展出

具有攻击能力的无人驾驶战斗机，它能在不危害美军飞行员的情况下，作为先锋

部队摧毁敌军防空系统。在现国防部长拉姆斯菲尔德打算提出的美军新战略中，

无人驾驶战斗机已被列为重点开发项目。

无人驾驶战斗机体形及作战能力与传统战机相差不大，但造价却便宜很多，

更能迅速大批生产应付战争需要。布什在近期关于调整美国国防战略的讲话中曾

重点提及此类战机，本年度美国国防预算也将拨款1亿5千万美元研发这一机种。

今年3月，正在试验中的一款无人驾驶飞机“捕猎者”成功发射导弹摧毁了一辆坦

克，这是美军自越战后首次进行的类似试验。

该款战机仅长27英尺，能被“打包”收藏在箱子内10年，一旦需要作战，只

需30分钟就能完成“拆箱”出征。波音还为其无人战斗机开发微波炮或激光炮，

用于摧毁敌军的雷达或导弹发射器。

美国军方之所以对研制无人驾驶飞机甚至高超音速轰炸机如此感兴趣，其中

一个重要原因是美军现在的王牌飞机??战斗机的隐形技术已被识破。例如，捷克

已发明一种能侦测B-2隐形轰炸机和F-117隐形战斗机的雷达。此外，据报其他

国家也已掌握了破解隐形战机的雷达技术。因此，将来的轰炸机必须靠速度和在

更高空进行轰炸才能达到目的。

目前，美军主要靠三种轰炸机作长途攻击：B-52、B-1B和B-2轰炸机。它

们的速度及最远航程均有限，因而需要在海外基地部署。但以高超音速轰炸机的

速度，美国只要在东西两岸部署了它，便可在数小时内轰炸全球任何地方，这就

可省掉在海外驻军带来的外交及开支问题。估计无人驾驶高超音速轰炸机将主要

被用于携带核武器攻击他国，以威慑如俄罗斯、伊拉克、朝鲜、印度、巴基斯坦

等国。美国将可凭借此机，巩固其军事霸权地位

不言而喻的幕后秘密

X-43A是一项高风险高回报研究项目。该型飞机设计以音速的7到10倍飞

行，使用新型的冲压式发动机来取代原始的火箭推动，这一只有12英尺长的

X-43A代表着实现太空飞行更快更经济目标上的一个巨大的飞跃。

如果未来商用客机能够达到10马赫的话，由纽约至洛杉矶的航时仅为半小

时。但NASA还打算开发更快的“高超音速”系列，预计X-43D型可达15马赫。

按这一速度，来往纽约和洛杉矶仅需20分钟，而飞到东京只要2小时，甚至太

空旅行也能变得更便宜简便。

有专家指出，高超音速飞机未必适用于商业用途，因为高速飞行能产生高温、

极度加速及低调动性，令乘客不舒服。因此这种无人驾驶的飞机最大的用途还是

在军事上。美国陆军飞行及导弹指挥室现已在利用风洞测试这种飞机，以评估它

可以装配何种导弹。

这种极速战机由于飞得太快，所以任何一种导弹都没有能力将它击落。美国

政府最近已新制定了“国家高超音速战略”，由美国三军、NASA和防卫先进研究

计划署携手统筹，负责研发所有达5倍音速的引擎、飞机、武器、发射系统等。

比方说，如果有了高超音速导弹，美军就能更有把握地用它来截击来犯的导弹，

而高超音速轰炸机也可以极速划破敌国长空执行任务，使敌国防空系统完全无力

跟踪和拦截。美国空军科学咨询委员会指出：“高超音速技术将令美国空军脱胎

换骨成真正的太空军队。”

1994 年 11 月，美国政府取消了 NASA 耗资庞大的国家空天飞机（NASP）

项目，X-30试验机也随即下马。为了顺应“更好、更快、更廉价”的航空航天战

略，美国高超音速试验计划（Hyper-X）计划应运而生，其中 X-43 就是其研究

核心。X-43 计划有 4 个型号即 X-43A、X-43B、X-43C 和 X-43D，其设计速

度目标为马赫 7 至马赫 10。

X-43A 与 X-30 不仅在外形上十分相似，而且发动机方案也都是采用机身一

体化的超音速燃烧冲压发动机。X-43A 的前机体设计成能产生激波的形状，以

对进入超音速燃烧冲压发动机进气道（安装在机体下方）的空气进行压缩。X-43A

试验飞机拥有先进的扁平小巧的机身，机身长 3.6 米，翼展 1.5 米，重量约为 1

吨。由于 X-43A 采用的是高超音速冲压发动机，其燃料为飞机上携带的液态氢，

助燃剂（氧化剂）为空气中的氧，因而需要借助 B-52 载机和助推火箭飞入空中。

2001 年 6 月，X-43A 在第一次试飞中由于助推火箭偏离航线并出现翻滚

被控制人员在空中紧急自毁。这次惨重的失败，让 X-43A 的试验计划大大延迟。

直到 2004 年 3 月 27 日，X-43A 才开始了第二次试飞。B-52 载机在离太平

洋海面大约 12,000 米的空域投下了“包裹”着 X-43A 的助推火箭，随后助推火

箭迅速爬升至 28,500 米的高空。这时，X-43A 从火箭中分离出来，依靠自身的

超音速燃烧冲压发动机工作了大约 10 秒钟，最高速度达到 8,000 公里/小时，

相当于 7 马赫，已经超过了使用火箭动力的 X-15A-2 试验机创造的 6.72 马

赫。这之后，X-43A 发动机停转，并在空中自由滑翔飞行约 6 分钟后，按预定

计划坠入加利福尼亚州附近的太平洋海域。X-43A 的试飞成功具有划时代的意

义，由于不象使用火箭发动机的飞行器那样必须携带所有的燃料和助燃剂，采用

高超音速冲压发动机的飞行器不仅能够减小自身体积，还能够提高飞行器有效载

荷量。如在军事应用中，与 X-43A 类似的飞行器将能携带更大重量的打击武器，

其小巧的体积也让敌方防不胜防。

X-43B 将于 2010 年以前试飞，与 X-43A 不同它将采用涡轮发动机和吸气

超音速燃烧冲压发动机的组合动力。这种新颖的组合动力可以自动调整使用那种

推动力以使飞行达到最佳速度：当飞机的速度只有两倍音速左右时，飞机借助涡

扇喷气发动机前进，这同普通飞机没有两样；当飞机在以高超音速飞行时（5 至

15 马赫），它就开始利用吸气超音速燃烧冲压发动机推进。X-43C 则用来验证

装有超音速燃烧冲压发动机的飞行器从 5 马赫加速到 7 马赫时的自由飞行性

能和超音速燃烧冲压负电荷的性能，其采用的发动机具有普通冲压发动机和超音

速冲压发动机的两种工作模式，预计将于 2008 年进行试飞。X-43D 的研制工

作也在进行中，它将装备一种冷却氢气燃料的双模式超音速冲压喷气发动机，可

将 X-43D 的速度增加至 15 马赫。

X-43A 从助推火箭上分离的想象图

携载 X-43A 的助推火箭与载机 B-52 脱离

助推火箭发动机点火

美国国防先进科技研究计划高级研究局的HTV2高超音速飞行器项目想象

图，HTV2设计希望达到20倍超音速的极速。

美国国防部2011年17日宣布，陆军当天早些时候成功试飞一个超高音速

飞行器，为进一步开发全球即时打击武器搜集了相关数据。

国防部发表声明说，试飞的飞行器为一架概念机，隶属高级超高音速武器

项目，由陆军空间和导弹防御司令部与战略司令部负责，当天是首次试飞。飞行

器美国东部时间6时30分左右从夏威夷考爱岛的太平洋导弹试射场发射，预定

目标是陆军位于夏威夷西南约3900公里的马绍尔群岛夸贾林环礁上的里根试验

场。这个飞行器利用三级推进火箭发射，送入地球大气层预定轨道后开始超高音

速滑翔，最终击中里根试验场的预定目标。

声明说，这次试飞目的是测试飞行器的推进、滑翔及远程飞行能力。试飞

中，陆军位于海、陆、空的信息平台搜集了飞行器在空气动力学、导航和热保护

等方面的数据。这些数据将用于开发今后的超高音速飞行器。

高级超高音速武器项目是陆军用于开发全球即时打击能力的武器项目。全

球即时打击能力指的是利用洲际弹道导弹、超高速巡航载具等运送精确制导的常

规弹头，对位于全球任何地点、只有很窄攻击窗口的高价值目标实施精确打击，

从发起攻击至攻击结束，所用时间不超过1小时。在与俄罗斯签署的核裁军条约

中，美国发展和部署全球即时打击武器未受限制。美国政府认为，全球即时打击

武器是在削减核武器的同时维持威慑能力和快速打击能力的一种办法。

当地时间2011年8月11日上午，一枚“牛头怪IV型”火箭搭载“猎鹰”HTV-2在

美国加州范登堡空军基地成功发射升空，但在太空边缘与火箭分离后，“猎鹰”

飞机在独自飞行并返回地球时失去联系。“猎鹰HTV-2号”被称为有史以来最快

的飞机，其速度可达每小时13000英里(约20倍音速)。图为8月11日发布的“猎

鹰HTV-2号”的效果图

美国高超音速试验计划（Hyper-X）计划

HTV-2高超音速无人机

这是NASA2004年研制的高超音速新型航天器——X-43

美国空军HTV-3X

美国将于4月在太平洋上空试飞一种最新超音速无人驾驶战机，这种名为第

二代“猎鹰” 高超音速飞行器(Falcon Hypersonic Technology Vehicle 2，HTV-2)的

战机，可携带5吨重的物资，以超过音速5倍的速度在2小时内可抵达世界任何

地方。

HTV-2采用了Typ Minotaur IV发动机技术，将在加利福尼亚的范登堡空军

基地升空试飞。在与火箭分离后，HTV-2将以高超音速度在大气层飞行，最后降

落在太平洋中部夸贾林环礁的里根实验场。无人机将飞行8000公里，以检验飞

机的绝热性和气体动力驾驶的稳定性。

根据美国国防部下属的美国国防先期研究计划局(DARPA)的报告，HTV-2

的载重量为5吨，是目前飞得最快的战机。这种黑色的楔型战机在2小时内可以

飞行近1.7万公里，相当于地球周长的一半，而洲际导弹的射程只有5500公里

至15000公里间。

美军一直渴望有一种更快的高超音速战机，以取代正在超期服役的

SR-71“黑鸟”超音速侦察机。这种侦察机的速度是音速的3倍，但是DARPA在

技术上始终没有取得突破。

2008年，DARPA提出了一项开发一种类似战斗机的HTV-3的计划。按照设

计，这种飞机具有其它超音速飞机“无与伦比的性能”，速度可达到音速的6倍，

将于2012年投入使用。然而由于2009年美国国会削减了财政预算，这个项目被

迫搁浅，DARPA只好转为开发HTV-2。

高超音速战机的开发给民用客机的发展带来希望。英国的工程师们正准备开

发一种5个小时就可以从英国飞往澳大利亚的高速客机，这种飞机没有舷窗，设

计容纳300名乘客，时速可达6000公里。

英国《飞行国际》网站2011年9月7日报道,美国国防工业协会在今年6月

主持了一次会议，就美国防部的科学技术计划展开探讨。来自美国空军研究试验

室(AFRL)的一位官员出席了会议，并在会上做了简要报告。他的报告清楚地表

明AFRL正计划通过实施“碳基复合材料”(CMC)、“涡轮基组合循环发动机”

(TBCC)和HTV-3X“黑雨燕”(Blackswift) 高超声速飞行器的后继型号等多个研

究项目，最终开发出一种可以“在任何时间、任何地点突破任何防空系统”的高

速飞行器。

上述情况表明美国空军和国防预先研究计划局(DARPA)之间就“黑雨燕”高

超声速飞行器项目展开的合作尽管在2008年被中止，但是双方在相关领域内的

合作并没有完全终止，而只是进入了“冬眠期”。据悉，美空军研究试验室今后

将会按部就班地实施上述计划，最终用10年时间研发出一种飞行速度大于4马

赫的高速轰炸机演示验证机。

X-43 Hyper-X Program

NASA established a multi-year experimental hypersonic ground and flight test

program called Hyper-X. The program sought to demonstrate "air-breathing" engine

technologies that promise to increase payload capacity or reduce vehicle size for the

same payload for future hypersonic aircraft and/or reusable space launch vehicles.

Payload capacity was to be increased by discarding the heavy oxygen tanks that

rockets must carry and by using a propulsion system that uses the oxygen in the

atmosphere as the vehicle flies at many times the speed of sound. Hydrogen will fuel

the program's research vehicles, but it requires oxygen from the atmosphere to burn.

The X-43 program was originally intended to feature two additional vehicles. As

envisioned, the X-43B would demonstrate an engine capable of operating in several

modes. The X-43B’s combined cycle engine would function as a normal turbojet at

low altitudes and switch to scramjet mode at high altitudes and speeds. Planned

X-43B flights were to occur sometime in 2009 after the completion of another

Hyper-X test vehicle, the X-43C. The X-43C was intended to demonstrate the

operation of a solid hydrocarbon-burning scramjet engine at speeds between Mach 5

and 7 sometime in 2008.

Both vehicles were cancelled in March 2004 because of a shift in NASA’s strategic

goals following the announcement of the President’s Vision for Space Exploration in

January of that year. However, because of the suc-cess of the X-43A , the U.S.

Congress added $25 million to the NASA 2005 budget to continue devel-opment of

the X-43C research vehicle.

The NASA/industry Hyper-X program sought to demonstrate airframe-integrated,

"air-breathing" engine technologies that promise to increase payload capacity for

future vehicles, including hypersonic aircraft (faster than Mach 5) and reusable space

launchers. The X-43 was to be the first free-flying demonstration of an

airframe-integrated, air-breathing engine and was to extend the flight range to Mach

10. Prior flight experiments conducted by the Russians using a rocket booster have

demonstrated air-breathing engine operation at Mach 5 to 6 conditions. Extending

air-breathing technologies to much greater speeds requires the development of

scramjet engines

Conventional rocket engines are powered by mixing fuel with oxygen, both of which

are traditionally carried onboard the aircraft. The Hyper-X vehicles, designated

X-43A, carried only their fuel - hydrogen - while the oxygen needed to burn the fuel

came from the atmosphere. By eliminating the need to carry oxygen aboard the

aircraft, future hypersonic vehicles will have room to carry more payload. Another

unique aspect of the X-43A vehicle is that the body of the aircraft itself forms critical

elements of the engine, with the forebody acting as the intake for the airflow and the

aft section serving as the nozzle. These technologies were to be put to the test during a

rigorous flight-research program at NASA Dryden.

NASA Dryden had several major roles in Phase I of the Hyper-X program, which was

a joint Dryden/NASA Langley Research Center program conducted under NASA's

Aeronautics and Space Transportation Technology Enterprise. Dryden's primary

responsibility was to fly three unpiloted X-43A research vehicles to help prove both

the engine technologies, the hypersonic design tools and the hypersonic test facilities

developed at Langley. NASA Langley, Hampton, VA, had overall management of the

Hyper-X program and led the technology development effort.

Through this Langley/Dryden/industry partnership, the Hyper-X program fulfilled a

key Agency goal of providing next-generation design tools and experimental aircraft

to increase design confidence and cut the design cycle time for aircraft.

Specifically, Dryden planned to:



Fly three unpiloted X-43A vehicles between January 2000 and September

2001.



Evaluate the performance of the X-43A research vehicles at Mach 7 and 10.



Demonstrate the use of air-breathing engines during flights of the X-43A

vehicles.

Provide flight research data to validate results of wind tunnel tests, analysis

and other aeronautical research tools used to design and gather information

about the vehicles.

As the lead Center for the flight-research effort, Dryden engineers worked closely

with their colleagues from Langley and industry to refine the design of the X-43A

vehicles. Dryden also managed the fabrication of both the X-43A vehicles and the

expendable booster rockets to serve as launch vehicles. Dryden also performed

flight-research planning as well as some vehicle instrumentation and provided control

of the tests.



Unlike conventional aircraft, the X-43A vehicles does not take off under their own

power and climb to test altitude. Instead, NASA Dryden's B-52 aircraft climbed to

about 20,000 feet for the first flight and release the launch vehicle. For each flight the

booster will accelerate the X-43A research vehicle to the test conditions (Mach 7 or

10) at approximately 100,000 feet, where it separates from the booster and fly under

its own power and preprogrammed control. Flights of the X-43A originate from the

Dryden/Edwards Air Force Base area, and the missions occur within the Western Sea

Range off the coast of California. The flight profile calls for launching the X-43A

vehicles heading west. The flight path for the vehicles varies in length and is

completely over water.

The B-52 Dryden used to carry the X-43A and launch vehicle to test altitude is the

oldest B-52 on flying status. The aircraft, on loan from the US Air Force, has been

used on some of the most important projects in aerospace history. It is one of two

B-52s used to air launch the three X-15 hypersonic aircraft for research flights. It also

has been used to drop test the various wingless lifting bodies, which contributed to the

development of the Space Shuttle. In addition, the B-52 was part of the original flight

tests of the Pegasus booster. Modified Pegasus® boosters will serve as the launch

vehicles.

Current Status

On 11 August 1998, the first piece of hardware was delivered to NASA - a scramjet

engine that was used for a series of ground tests in NASA Langley's 8 Foot High

Temperature Tunnel. This engine could later be used for flight if necessary.

The first flight engine was to be mated to the X-43 flight vehicle in February 1999

and delivered to NASA Dryden leading to the first flight of the program in early 2000.

The next major delivery was to be the X-43A airframe integrated with the second

engine and adapter to NASA Dryden in June 1999. The engine was to be transported

to Langley for a series of wind tunnel tests in the 8-Foot High-Temperature Tunnel

beginning in early 1999 prior to the first scheduled flight in early 2000.

Orbital Sciences Corp., Dulles, VA, was under contract to designing and build three

Pegasus-derivative launch vehicles for the series of X-43A vehicles, a process that

Dryden oversaw. A successful critical design review for the launch vehicle was held at

Orbital¹s Chandler, Ariz., facility in December 1997.

NASA selected MicroCraft Inc., Tullahoma, Tenn., in March 1997 to fabricate the

unpiloted research aircraft for the flight research missions, two flights at Mach 7 and

one at Mach 10 beginning in 2000. Micro-Craft is aided by Boeing, which is

responsible for designing the research vehicle, developing flight control laws and

providing the thermal protection system; GASL Inc., which is building the scramjet

engines and their fuel systems and providing instrumentation for the vehicles; and

Accurate Automation, Chatanooga, Tenn.

The first X-43A Hyper-X program research vehicle was launched on 02 June 2001.

For the launch, the X-43A was attached to the nose of a modified Pegasus launch

vehicle, which was carried by NASA's modified B-52 bomber. Seventy-five minutes

after takeoff, at an altitude of approximately 24,000 ft., the Pegasus was released. Its

solid rocket motor ignited 5.2 seconds later sending the launch vehicle and research

vehicle payload on its test flight. Eight seconds later, the vehicle began its planned

pitch up maneuver, which was expected to take it to an altitude of approximately

95,000 ft. Shortly thereafter, the X-43A began to experience a control anomaly

characterized by a roll oscillation. At 13.5 seconds after release and at an altitude of

approximately 22,000 ft., structural overload of the starboard elevon occurred. The

severe loss of control caused the X-43A to deviate significantly from its planned

trajectory, and as a result, it was destroyed by range safety 48.6 seconds after release.

On 23 July 2003 the NASA mishap investigation board charged to review the loss of

the X-43A Hyper-X program research vehicle concluded no single factor or potential

contributing factor caused the mishap. The flight failed because the vehicle's control

system design was deficient in several analytical modeling areas, which overestimated

the system's margins. The mishap board found the major contributors to the mishap

were modeling inaccuracies in the fin actuation system, modeling inaccuracies in the

aerodynamics, and insufficient variations of modeling parameters. The flight mishap

could only be reproduced when all of the modeling inaccuracies with uncertainty

variations were incorporated in the analysis.

The second flight test of an unpiloted 12-foot-long X-43A began on 27 March 2004

when the vehicle was dropped from the wing of a B-52 aircraft, lofted to nearly

100,000 feet by a booster rocket and released over the Pacific Ocean to briefly fly

under its own power at seven times the speed of sound (almost 5,000 mph).

The final flight of NASA's X-43A hypersonic research aircraft took place 16

November 2004. The mission flight-validated the operation of the X-43A's

supersonic-combustion ramjet - or scramjet - engine at a record airspeed of almost

Mach 10, or 10 times the speed of sound. The X-43A and its modified Pegasus

booster rocket was mated to NASA's B-52B launch aircraft on Thursday, Nov. 11.

Pre-flight checks of the X-43A and the booster are occurring Friday and Saturday,

with final closeouts and fueling slated for Sunday, Nov. 14th. NASA's X-43A

scramjet-powered research vehicle broke the air speed record November 16 and

showed that an "air-breathing" engine can fly at nearly 10 times the speed of sound.

Preliminary data indicate that the revolutionary supersonic combustion ramjet

(scramjet) engine worked successfully at about Mach 10 -- more than 11,000

kilometers per hour -- as it flew at an altitude of nearly 34,000 meters. The flight took

place in restricted airspace over the Pacific Ocean northwest of Los Angeles. It was

the fastest of three unpiloted tests in NASA's Hyper-X Program to explore an

alternative to rocket power for space-access vehicles

Air-Breathing Scramjet Engine Technologies

This challenging ground and flight-research program will expand significantly the

boundaries of air-breathing flight by being the first to fly a "scramjet" powered

aircraft at hypersonic speeds. Demonstrating the airframe-integrated ramjet/scramjet

engine tops the list of program technology goals, followed by development of

hypersonic aerodynamics and validation of design tools and test facilities for

air-breathing hypersonic vehicles. The scramjet engine is the key enabling technology

for this program. Without it, sustained hypersonic flight could prove impossible.

Ramjets operate by subsonic combustion of fuel in a stream of air compressed by the

forward speed of the aircraft itself, as opposed to a normal jet engine, in which the

compressor section (the compressor blades) compresses the air. Unlike jet engines,

ramjets have no rotating parts. Ramjets operate from about Mach 2 to Mach 5.

Scramjets (supersonic-combustion ramjets) are ramjet engines in which the airflow

through the whole engine remains supersonic. Scramjet technology is challenging

because only limited testing can be performed in ground facilities. Long duration,

full-scale testing requires flight research. Hyper-X will help build knowledge,

confidence and a technology bridge to very high Mach number flight.

Currently, the world's fastest air-breathing aircraft, the SR-71, cruises slightly faster

than Mach 3. The highest speed attained by NASA's rocket-powered X-15 was Mach

6.7. The X-43A aircraft is designed to fly faster than any previous air-breathing

aircraft.

Hyper-X Vehicle Specifications



Length: approximately 12 ft



Weight: approximately 2,200 lb



Performance: Mach 7-10

X-43B Revolutionary Turbine Accelerator (RTA)

The air-breathing, hypersonic X-43B — the third and largest of NASA's Hyper-X

series flight demonstrators — could fly later this decade. NASA will develop, test and

fly the Hyper-X series over the next two decades to support development of

future-generation reusable launch vehicles and improved access to space.

The Turbine-Based Combined Cycle (TBCC) engine project seeks to deliver a Mach

4+ hypersonic propulsion system in this decade. Prime among its enabling

technologies: the Revolutionary Turbine Accelerator (RTA), intended to demonstrate

high mach turbine performance and durability for space access.

The Next Generation Launch Technology program tasked NASA's Glenn Research

Center to lead high-Mach turbine propulsion development projects, including the

TBCC/RTA effort. Glenn Research Center has formulated the Revolutionary Turbine

Accelerator project to develop and demonstrate TBCC-based propulsion for space

access. Project participants include industry, academia, the U.S. Department of

Defense and several NASA centers.

The state-of-the-art in high Mach turbine engine technology is the J-58. The RTA

project seeks to advance the state-of-the-art in high Mach turbines to 25% increase in

Mach number, 250% higher Thrust/Weight, and 2 times improved component life by

2010. By 2015 the RTA project seeks to advance high Mach turbines to 35% increase

in Mach number, 375% higher T/W, and 4 times improved critical component life. In

order to further these advancements the project is initially pursuing a mid-scale

ground demonstration testbed.

The RTA project consists of the development and test of a mid-scale ground-based

turbine accelerator demonstrator and a possible sub-scale turbine accelerator flight

demonstrator with Dual Mode Scram Jet (DMSJ) for a X43-B test flight vehicle.

The mid-scale RTA Ground Test Engine (GTE) would uate & demonstrate Mach 4+

turbo machinery and the advanced technologies required to reach Mach 4. The RTA

GTE would be approximately 50-60% of projected full-scale and will be flight-like.

Flight-like means that all the ancillary components, for example a fuel heat exchanger,

will be incorporated into the demonstrator. In other words, there will be no external

components. However, the GTE will not be flight-weight.

Specifically, the RTA GTE will be used to uate the following characteristics of a Mach

4+ turbine accelerator:



Engine cycle performance and operability;



Windmilling at High Mach;



Demonstration of enabling technologies for full scale RTA;



Reliability & Durability of High Mach turbine components;



Thermal management issues;



Transition modes - turbine to ram;



Inlet and nozzle integration with engine;



Fuel system & cooling circuits;



Engine control system.

NASA GRC, in Cleveland, OH, led the Revolutionary Turbine Accelerator Project

(RTA), and selected GE Aircraft Engines (GEAE), headquartered in Evendale, OH for

a 5-year mid-scale project to begin immediately. Geae is wokring with NASA GRC to

develop the RTA for a new Mach 4+ engine.

GEAE worked to develop an augmentor/ramburner - a key feature for the TBCC

engine. This construct will serve as a conventional augmentor boosting the turbine

engine thrust nearly 50% during its transition to supersonic flight. The augmentor will

transition to a ramburner between Mach 2 and 3 which will then accelerate the vehicle

to speeds above Mach 4.

Current Technology



Plan for the Future



Low Speed System

Mach 3+

Thrust to Weight ratio 4.0

Low Reliability

High Maintenance

1960's Technologies

High Speed System

Mach 4+

Thrust to Weight ratio 15-20

Airline-Like reliability

Low Maintenance

New Millennium Technologies

X-43C

The air-breathing, hypersonic X-43C, is part of NASA's Hyper-X series of flight

demonstrators. Now in development, the X-43C is expected to accelerate to a

maximum potential speed of about 5,000 mph, and could undergo flight-testing as

early as 2008. NASA will develop, test and fly the Hyper-X series over the next two

decades to support development of future-generation reusable launch vehicles and

improved access to space.

On 08 October 2003 NASA selected Allied Aerospace Industries of Tullahoma, Tenn.,

to provide three flight-ready demonstrator vehicles that will fly approximately 5,000

miles per hour or seven times the speed of sound. The multi-year project, called

X-43C, will expand the hypersonic flight envelope for air-breathing engines.

The cost-plus-fixed-fee completion type contract carried performance incentives and

was valued at nearly $150 million over 66 months. The base activity covers all work

through completion of the Preliminary Design Review, and the optional effort covers

the final design, hardware fabrication and all associated support activities.

The X-43C is the next logical step, following the current Hyper-X (X-43A) vehicle

that aims at demonstrating short duration scramjet powered flight at Mach 7 and

Mach 10. The X-43C will demonstrate free flight of a scramjet-powered vehicle with

acceleration capability from Mach 5 to Mach 7, as well as operation of a hydrocarbon

fuel-cooled scramjet.

NASA's Langley Research Center, Hampton, Va., is leading a combined U.S. Air

Force/industry team in the design and development of the X-43C demonstrator

vehicle and its propulsion system. The engine, which will be provided by the Air

Force, will be a dual-mode scramjet capable of running as a ramjet or scramjet.

Allied Aerospace, Flight Systems Division, will team with Pratt & Whitney, West

Palm Beach, Fla.; Boeing Phantom Works, Huntington Beach, Calif.; and RJK

Technologies, Blacksburg, Va. Work will be performed primarily in Tullahoma and

West Palm Beach, although some contract work will also take place at Huntington

Beach, Blacksburg and St. Louis, Mo., and at Langley and NASA's Dryden Flight

Research Center, Edwards, Calif.

Future air-breathing space access vehicles offer advantages over conventional

rocket-powered vehicles that must carry all of the oxidizer needed to burn their fuel.

Air-breathing engine-powered vehicles obtain oxygen from the atmosphere in flight.

By minimizing the need to carry oxidizer, smaller and more efficient vehicles can be

designed for space access missions.

When fully developed, these advanced propulsion systems will offer increased safety,

payload capacity and economy of operation for future, reusable space access vehicles.

The X-43C project will validate advanced technologies, design tools and test

techniques that will enable design of such vehicles in the future.

For the three demonstration flights, a Pegasus-derived rocket booster will be

air-launched by a carrier aircraft to boost the X-43C demonstrator vehicles to Mach 5

at approximately 80,000 feet. The X-43C will separate from the booster and continue

to accelerate to Mach 7 under its own power and autonomous control. Flights will

originate from Dryden/Edwards Air Force Base, Calif. Flight paths of the vehicles

will be over water within the Pacific Test Range.