Boeing X-51
Encyclopedia
The Boeing X-51 is an unmanned scramjet
demonstration aircraft for hypersonic
(Mach
6, approximately 4000 miles per hour (6,437.4 km/h) at altitude) flight testing. It successfully completed its first free-flight on 26 May 2010 and also achieved the longest duration flight at speeds over Mach 5.
The X-51 Waverider
program is run as a cooperative effort of the United States Air Force
, DARPA, NASA
, Boeing
and Pratt & Whitney Rocketdyne
. The program is managed by the Propulsion Directorate within the United States
Air Force Research Laboratory
(AFRL). The X-51 had its first captive flight attached to a B-52 in December 2009.
. Pratt & Whitney
received a contract from the AFRL to develop a hydrocarbon-fueled scramjet engine which led to the development of the SJX61 engine. The SJX61 engine was originally meant for NASA's X-43C, which was eventually canceled. The engine was applied to the AFRL's Scramjet Engine Demonstrator program in late 2003. The scramjet flight test vehicle was designated X-51 on 27 September 2005.
In flight demonstrations, the X-51 is carried by a B-52 to an altitude
of about 50,000 feet (15.2 kilometers) and then released over the Pacific Ocean
. The X-51 is initially propelled by an MGM-140 ATACMS solid rocket booster
to approximately Mach 4.5, before it is jettisoned. Then the vehicle's Pratt & Whitney Rocketdyne
SJY61 scramjet takes over and accelerates it to a top flight speed near Mach 6. The X-51 uses JP-7
fuel for the SJY61 scramjet, carrying some 270 lb (122.5 kg) onboard.
Previously DARPA viewed X-51 as a stepping stone to Blackswift, a planned hypersonic demonstrator which was canceled in October 2008.
tests at the NASA Langley Research Center
on 27 July 2006. Testing continued there until a simulated X-51 flight at Mach 5 was successfully completed on 30 April 2007. The testing is intended to observe acceleration
between Mach 4 and Mach 6 and to demonstrate that hypersonic thrust
"isn't just luck". Four test flights were initially planned for 2009, but the first captive flight of the X-51A on a B-52 was not conducted until 9 December 2009, with further captive flights in early 2010.
traveling through a portion of the Naval Air Station Point Mugu
Sea Range caused a 24 hour postponement. The X-51 completed its first powered flight successfully on 26 May 2010 by flying for over 200 seconds and reaching a speed of Mach 5; it did not meet the planned 300 second flight duration, however. The flight had the longest scramjet burn time of 140 seconds. The X-43 had the previous longest flight burn time of 12 seconds, while setting a new speed record of Mach 9.8 (12,144 km/h, 7,546 mph).
Three more test flights were planned and will use the same flight trajectory
. Boeing proposed to the Air Force Research Laboratory that two test flights be added in order to increase the total to six, with flights taking place at four to six week intervals, assuming there are no failures.
The second test flight was initially scheduled for 24 March 2011, but was not conducted due to unfavorable test conditions. The flight took place on 13 June 2011. However, the flight over the Pacific Ocean ended early due to an inlet unstart
event after being boosted to Mach 5 speed. The flight data from the test is being investigated. A B-52 released the X-51 at an approximate altitude of 50,000 feet. The X-51’s scramjet engine lit on ethylene, but did not properly transition to JP-7
fuel operation.
Related development
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
demonstration aircraft for hypersonic
Hypersonic
In aerodynamics, a hypersonic speed is one that is highly supersonic. Since the 1970s, the term has generally been assumed to refer to speeds of Mach 5 and above...
(Mach
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
6, approximately 4000 miles per hour (6,437.4 km/h) at altitude) flight testing. It successfully completed its first free-flight on 26 May 2010 and also achieved the longest duration flight at speeds over Mach 5.
The X-51 Waverider
Waverider
A waverider is a hypersonic aircraft design that improves its supersonic lift-to-drag ratio by using the shock waves being generated by its own flight as a lifting surface. To date the only aircraft to use the technique is the Mach 3 supersonic XB-70 Valkyrie, which was waverider-like with its...
program is run as a cooperative effort of the United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
, DARPA, NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, Boeing
Boeing
The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...
and Pratt & Whitney Rocketdyne
Pratt & Whitney Rocketdyne
Pratt & Whitney Rocketdyne is a United States company that designs and produces rocket engines that use liquid propellants. Pratt & Whitney Rocketdyne, headquartered in Canoga Park, California, is a division of Pratt & Whitney, itself a wholly owned subsidiary of United Technologies Corporation...
. The program is managed by the Propulsion Directorate within the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Air Force Research Laboratory
Air Force Research Laboratory
The Air Force Research Laboratory is a scientific research organization operated by the United States Air Force Materiel Command dedicated to leading the discovery, development, and integration of affordable aerospace warfighting technologies; planning and executing the Air Force science and...
(AFRL). The X-51 had its first captive flight attached to a B-52 in December 2009.
Design and development
In the 1990s the Air Force Research Laboratory (AFRL) began the HyTECH program for hypersonic propulsionAir propulsion
Air propulsion is the generation of thrust during flight by an aircraft or a creature such as a bird, bat or insect.-Aircraft:An aircraft propulsion system must serve two purposes. First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is cruising...
. Pratt & Whitney
Pratt & Whitney
Pratt & Whitney is a U.S.-based aerospace manufacturer with global service operations. It is a subsidiary of United Technologies Corporation . Pratt & Whitney's aircraft engines are widely used in both civil aviation and military aviation. Its headquarters are in East Hartford, Connecticut, USA...
received a contract from the AFRL to develop a hydrocarbon-fueled scramjet engine which led to the development of the SJX61 engine. The SJX61 engine was originally meant for NASA's X-43C, which was eventually canceled. The engine was applied to the AFRL's Scramjet Engine Demonstrator program in late 2003. The scramjet flight test vehicle was designated X-51 on 27 September 2005.
In flight demonstrations, the X-51 is carried by a B-52 to an altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...
of about 50,000 feet (15.2 kilometers) and then released over the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. The X-51 is initially propelled by an MGM-140 ATACMS solid rocket booster
Solid rocket booster
Solid rocket boosters or Solid Rocket Motors, SRM, are used to provide thrust in spacecraft launches from the launchpad up to burnout of the SRBs. Many launch vehicles include SRBs, including the Ariane 5, Atlas V , and the NASA Space Shuttle...
to approximately Mach 4.5, before it is jettisoned. Then the vehicle's Pratt & Whitney Rocketdyne
Pratt & Whitney Rocketdyne
Pratt & Whitney Rocketdyne is a United States company that designs and produces rocket engines that use liquid propellants. Pratt & Whitney Rocketdyne, headquartered in Canoga Park, California, is a division of Pratt & Whitney, itself a wholly owned subsidiary of United Technologies Corporation...
SJY61 scramjet takes over and accelerates it to a top flight speed near Mach 6. The X-51 uses JP-7
JP-7
JP-7 is a jet fuel developed by the U.S. Air Force for use in supersonic aircraft because of its high flash point and thermal stability. It is the fuel used in the Pratt & Whitney J58 engines, used in the Lockheed SR-71 Blackbird. The air compression of Mach 3+ cruising flight generates very high...
fuel for the SJY61 scramjet, carrying some 270 lb (122.5 kg) onboard.
Previously DARPA viewed X-51 as a stepping stone to Blackswift, a planned hypersonic demonstrator which was canceled in October 2008.
Initial testing
Ground tests of the X-51A began in late 2006. A preliminary version of the X-51, the "Ground Demonstrator Engine No. 2", completed wind tunnelWind tunnel
A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
tests at the NASA Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...
on 27 July 2006. Testing continued there until a simulated X-51 flight at Mach 5 was successfully completed on 30 April 2007. The testing is intended to observe acceleration
Acceleration
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
between Mach 4 and Mach 6 and to demonstrate that hypersonic thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
"isn't just luck". Four test flights were initially planned for 2009, but the first captive flight of the X-51A on a B-52 was not conducted until 9 December 2009, with further captive flights in early 2010.
Powered flight tests
The first powered flight of the X-51 was planned for 25 May 2010, but the presence of a cargo shipCargo ship
A cargo ship or freighter is any sort of ship or vessel that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year; they handle the bulk of international trade...
traveling through a portion of the Naval Air Station Point Mugu
Naval Air Station Point Mugu
Naval Base Ventura County Point Mugu or NBVC Point Mugu is a military airbase located in Point Mugu, Ventura County, California, United States. Due to realignment actions which occurred in 2000, the base is now part of Naval Base Ventura County , a consolidated organization that also includes...
Sea Range caused a 24 hour postponement. The X-51 completed its first powered flight successfully on 26 May 2010 by flying for over 200 seconds and reaching a speed of Mach 5; it did not meet the planned 300 second flight duration, however. The flight had the longest scramjet burn time of 140 seconds. The X-43 had the previous longest flight burn time of 12 seconds, while setting a new speed record of Mach 9.8 (12,144 km/h, 7,546 mph).
Three more test flights were planned and will use the same flight trajectory
Trajectory
A trajectory is the path that a moving object follows through space as a function of time. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit—the path of a planet, an asteroid or a comet as it travels around a central mass...
. Boeing proposed to the Air Force Research Laboratory that two test flights be added in order to increase the total to six, with flights taking place at four to six week intervals, assuming there are no failures.
The second test flight was initially scheduled for 24 March 2011, but was not conducted due to unfavorable test conditions. The flight took place on 13 June 2011. However, the flight over the Pacific Ocean ended early due to an inlet unstart
Unstart
Unstart is the supersonic choking reaction that occurs in ducts with an upstream mass flow greater than the downstream mass flow.There are other ways of conceptualizing unstart which can be helpful...
event after being boosted to Mach 5 speed. The flight data from the test is being investigated. A B-52 released the X-51 at an approximate altitude of 50,000 feet. The X-51’s scramjet engine lit on ethylene, but did not properly transition to JP-7
JP-7
JP-7 is a jet fuel developed by the U.S. Air Force for use in supersonic aircraft because of its high flash point and thermal stability. It is the fuel used in the Pratt & Whitney J58 engines, used in the Lockheed SR-71 Blackbird. The air compression of Mach 3+ cruising flight generates very high...
fuel operation.
Specifications
See also
- WaveriderWaveriderA waverider is a hypersonic aircraft design that improves its supersonic lift-to-drag ratio by using the shock waves being generated by its own flight as a lifting surface. To date the only aircraft to use the technique is the Mach 3 supersonic XB-70 Valkyrie, which was waverider-like with its...
- Flight airspeed record
Related development
- NASA X-43
External links
- X-51 WaveRider page on Boeing.com
- X-51 fact sheet on USAF site
- "AFRL mulls adding scope to X-51A Waverider hypersonic tests". Flight International. March 2009.
- "Pratt & Whitney Rocketdyne Scramjet Excels in USAF Tests". Aviation Week - subscribers only
- YouTube video of FoxNews report, preceding test flight
- YouTube video of test flight, shot from NASA chase plane