Boeing X-51

  • Boeing
  • DARPA ( design and development )

The Boeing X -51A Waverider is an unmanned aircraft demonstration with ramjet, which should reach a speed of Mach 6 . The X -51A reached ( the last flight ), however, only Mach 5.1. The X -51A is the direct successor of the X -43 and the Air Force Research Laboratory, Boeing, Pratt & Whitney Rocketdyne and companies as well as the DARPA developed. Potential military applications are seen at hypersonic aircraft and missiles to fight time-critical targets. However, one also plan to build a relatively inexpensive space shuttle play a role. The X -51A is a single aircraft. Hence each of the four machines flew only once before it crashed into the Pacific Ocean.


The development of the X -51A began in late 2004 and early 2005, after the flight tests of the X -43 were completed and DARPA needed another demonstration aircraft for the drive with ramjet under the now-defunct Falcon project. The ground tests have been successfully carried out in 2006 and 2007. The X -51A was from earlier projects, such as the Advanced Rapid Response Missile Demonstrator forth. A special feature is used for the X -51 flame retardant of the type jet fuel JP -7, developed for the Lockheed SR -71, and used for the ignition of ethylene. All previous ramjet engines were powered by hydrogen, which is dangerous to handle. A hydrogen tank is also relatively large, and so takes up most of the available space a. The X -51A was also designed as a wave rider for exploiting the compression lift.

The first flight of Flight Test Vehicle 1 (FTV 1) was scheduled for October 27, 2009, was postponed several times and finally carried out on 26 May 2010 by the Edwards Air Force Base in the Mojave Desert in California from. Three other specimens under construction to complete flights.

To launch the missile was launched on a wing pylon of a Boeing B- 52H to a height of about 15 miles and dropped at about Mach 0.8. Two accompanying P -3 Orion were responsible for the collection of telemetry data, while ground radar stations took over the trajectory tracking. The aircraft from the booster of a tactical solid rocket was accelerated MGM -140 ATACMS, who received an aerodynamic fairing and lighter titanium nozzles. At a speed of Mach 4.8 and an intermediate stage of the booster at an altitude of about 20 km were separated.

The ramjet engine P & W Rocketdyne SJY 61-2 was then activated at a speed of Mach 4.8. Thus, while the combustion chamber is not overheated by the 1000 ° C hot air flowing therethrough, it will be bathed in the operation of the fuel that evaporates. The cooling channels are provided with a catalytic coating, the heavy fuel into lighter molecules such as Hydrogen or ethylene, decomposed. This burn due to the high temperature of fuel and working fluid within a millisecond. As the necessary temperature is not present immediately after turning on the engine, ethylene is first introduced. After reaching the necessary conditions of operation of JP -7 is changed. The planned operation time of 300 seconds for the acceleration to the intended final speed greater than Mach 6 could not be achieved. The X -51 accelerated for 140 seconds to about Mach 5, then had to be destroyed because of failure of the telemetry link though. Despite the shorter operating time and lower terminal velocity of the first flight is considered successful. With an acceleration time of 150 seconds with 211 seconds flight time of 10 seconds record the X -43 was replaced in 2004.

The second test flight on June 13, 2011 also ended prematurely. During the transition of ethylene on JP -7 has caused problems in the air inlet. Attempts to stabilize the flow and combustion process failed, and the missile crashed into the Pacific Ocean.

Another test flight on August 15, 2012 ended as the previous flights also, with a crash in the Pacific. Just a few seconds after the scheduled notching of the bearing B -52 An error occurred in one of the tail rudder.

In the fourth and final test flight on May 1, 2013, the X -51A Mach reached 5.1. The engine worked for more than six minutes with the X - 51 260 nautical miles driven put.

The aim of the proposed tests, four of the X- 51 is to cause, inter alia, the ignition at lower speeds and temperatures than previously possible. Currently, a missile is required to bring the ramjet aircraft to ignition speed. The engineers hope that in future sufficient to ignite the speed that reaches a normal jet engine.

At the 54th Annual Laureate Awards from the American magazine Aviation Week the project on March 8, 2011 in the category Aeronautics / Propulsion has been excellent.


  • Length: 7.60 to 7.90 m
  • Weight: 1814 kg
  • Maximum speed: Mach 7 ( reached Mach 5.1 )