The NASA X-43 was an

experimental An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when ...

unmanned An uncrewed vehicle or unmanned vehicle is a vehicle without a person on board. Uncrewed vehicles can either be under telerobotic control—remote controlled or remote guided vehicles—or they can be autonomously controlled—autonomous vehicl ...

hypersonic In aerodynamics, a hypersonic speed is one that exceeds 5 times the speed of sound, often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since in ...

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...

with multiple planned scale variations meant to test various aspects of

hypersonic flight Hypersonic flight is flight through the atmosphere below altitudes of about 90 km at speeds greater than Mach 5, a speed where dissociation of air begins to become significant and high heat loads exist. Speeds of Mach 25+ have been achieve ...

. It was part of the

X-plane The X-planes are a series of experimental United States aircraft and rockets, used to test and evaluate new technologies and aerodynamic concepts. They have an X designator within the US system of aircraft designations, which denotes the exper ...

series and specifically of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

's Hyper-X program. It set several airspeed records for

jet aircraft A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines. Whereas the engines in propeller-powered aircraft generally achieve their maximum efficiency at much lower speeds and altitudes, je ...

. The X-43 is the fastest jet-powered aircraft on record at approximately Mach 9.6.Thompson, Elvia, Keith Henry and Leslie Williams
"Faster Than a Speeding Bullet: Guinness Recognizes NASA Scramjet."
''

.'' Retrieved: August 1, 2011. A winged

booster rocket A booster rocket (or engine) is either the first stage of a multistage launch vehicle, or else a shorter-burning rocket used in parallel with longer-burning sustainer rockets to augment the space vehicle's takeoff thrust and payload capability ...

with the X-43 placed on top, called a "stack", was

drop launch A drop test is a method of testing the in-flight characteristics of prototype or experimental aircraft and spacecraft by raising the test vehicle to a specific altitude and then releasing it. Test flights involving powered aircraft, particularly ...

ed from a

Boeing B-52 Stratofortress The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air ...

. After the booster rocket (a modified first stage of the

Pegasus rocket Pegasus is an Air launch to orbit, air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to into low Earth orbit, Pegasus first fl ...

) brought the stack to the target speed and altitude, it was discarded, and the X-43 flew free using its own engine, a

scramjet A scramjet (supersonic combustion ramjet) is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully ...

. The first plane in the series, the X-43A, was a single-use vehicle, of which three were built. The first X-43A was destroyed after malfunctioning in flight in 2001. Each of the other two flew successfully in 2004, setting speed records, with the scramjets operating for approximately 10 seconds followed by 10-minute glides and intentional crashes into the ocean. Plans for more planes in the X-43 series have been suspended or cancelled, and replaced by the

USAF The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...

managed X-51 program.

Development

The X-43 was a part of NASA's Hyper-X program, involving the American space agency and contractors such as

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

, Micro Craft Inc,

Orbital Sciences Corporation Orbital Sciences Corporation (commonly referred to as Orbital) was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other governmen ...

and

General Applied Science Laboratory General Applied Science Laboratory (GASL) is an American aerospace company, known as a pioneer of hypersonic propulsion. Description General Applied Science Laboratory was founded in 1956 by Antonio Ferri and became a developer and testing house f ...

(GASL). Micro Craft Inc. built the X-43A and GASL built its engine. One of the primary goals of NASA's

Aeronautics Enterprise Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...

was the development and demonstration of technologies for air-breathing hypersonic flight. Following the cancellation of the

National Aerospace Plane The Rockwell X-30 was an advanced technology demonstrator project for the National Aero-Space Plane (NASP), part of a United States project to create a single-stage-to-orbit (SSTO) spacecraft and passenger spaceliner. Started in 1986, it was can ...

(NASP) program in November 1994, the United States lacked a cohesive hypersonic technology development program. As one of the "better, faster, cheaper" programs developed by NASA in the late 1990s, the Hyper-X used technology and research from the NASP program which advanced it toward the demonstration of hypersonic air breathing propulsion, The Hyper-X Phase I was a NASA Aeronautics and Space Technology Enterprise program conducted jointly by the

Langley Research Center The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...

Hampton, Virginia Hampton () is an independent city (United States), independent city in the Commonwealth (U.S. state), Commonwealth of Virginia in the United States. As of the 2020 United States Census, 2020 census, the population was 137,148. It is the List ...

, and the

Dryden Flight Research Center The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA. Its primary campus is located inside Edwards Air Force Base in California and is considered NASA's premier site for aeronautical rese ...

Edwards, California Edwards (formerly, Muroc and Wherry Housing) is an unincorporated community in Kern County, California. It is located east-southeast of Mojave, about northeast of Lancaster, east of Rosamond, and south of California City at an elevation o ...

. Langley was the lead center and responsible for hypersonic technology development. Dryden was responsible for flight research. Phase I was a seven-year, approximately $230 million, program to flight-validate

propulsion, hypersonic

aerodynamics Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...

and design methods. Subsequent phases were not continued, as the X-43 series of aircraft was replaced in 2006 by the X-51.

Design

The X-43A aircraft was a small unpiloted test vehicle measuring just over in

length Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Interna ...

. The vehicle was a

lifting body A lifting body is a fixed-wing aircraft or spacecraft configuration in which the body itself produces lift. In contrast to a flying wing, which is a wing with minimal or no conventional fuselage, a lifting body can be thought of as a fuselage wi ...

design, where the body of the aircraft provides a significant amount of

lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...

for flight, rather than relying on

wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expres ...

s. The aircraft weighed roughly . The X-43A was designed to be fully controllable in high-speed flight, even when

gliding Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is al ...

without

propulsion Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from ...

. However, the aircraft was not designed to land and be recovered. Test vehicles crashed into the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

when the test was over. Traveling at Mach speeds produces a lot of heat due to the

compression Compression may refer to: Physical science *Compression (physics), size reduction due to forces *Compression member, a structural element such as a column *Compressibility, susceptibility to compression * Gas compression *Compression ratio, of a ...

shock waves In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a med ...

involved in supersonic

aerodynamic drag In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fl ...

. At high Mach speeds, heat can become so intense that metal portions of the airframe could melt. The X-43A compensated for this by cycling water behind the engine cowl and sidewall leading edges, cooling those surfaces. In tests, the water circulation was activated at about Mach 3.

Engine

The craft was created to develop and test a supersonic-combustion ramjet, or "

" engine, an engine variation where external combustion takes place within air that is flowing at supersonic speeds. The X-43A's developers designed the aircraft's airframe to be part of the

system: the forebody is a part of the intake airflow, while the aft section functions as an exhaust nozzle.Martin, Guy
“Hypersonic Pioneer: The X-43A.”
''AircraftInFormation.info.'' Retrieved: August 16, 2012. The engine of the X-43A was primarily fueled with

hydrogen fuel Hydrogen fuel refers to hydrogen which is burned as fuel with oxygen. It is zero-carbon, provided that it is created in a process that does not involve carbon. It can be used in fuel cells or internal combustion engines (see HICEV). Regarding hydr ...

. In the successful test, about of the fuel was used. Unlike rockets, scramjet-powered vehicles do not carry oxygen on board for fueling the engine. Removing the need to carry oxygen significantly reduces the vehicle's size and weight. In the future, such lighter vehicles could take heavier

payload Payload is the object or the entity which is being carried by an aircraft or launch vehicle. Sometimes payload also refers to the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight. Depending on the nature of ...

s into

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually consider ...

or carry payloads of the same weight much more efficiently. Scramjets only operate at speeds in the range of Mach 4.5 or higher, so rockets or other jet engines are required to initially boost scramjet-powered aircraft to this base velocity. In the case of the X-43A, the aircraft was accelerated to high speed with a

launched from a converted

bomber. The combined X-43A and Pegasus vehicle was referred to as the "stack" by the program's team members. The engines in the X-43A test vehicles were specifically designed for a certain speed range, only able to compress and ignite the fuel-air mixture when the incoming airflow is moving as expected. The first two X-43A aircraft were intended for flight at approximately Mach 7, while the third was designed to operate at speeds greater than at altitudes of or more.

Operational testing

NASA's first X-43A test on June 2, 2001 failed because the Pegasus booster lost control about 13 seconds after it was released from the B-52 carrier. The rocket experienced a control oscillation as it went

transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic ...

, eventually leading to the failure of the rocket's

starboard Port and starboard are nautical terms for watercraft and aircraft, referring respectively to the left and right sides of the vessel, when aboard and facing the bow (front). Vessels with bilateral symmetry have left and right halves which are ...

elevon Elevons or tailerons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control), hence the name. They are frequently used on tailless aircraft such as flying wings. ...

. This caused the rocket to deviate significantly from the planned course, and it was destroyed as a safety precaution. An investigation into the incident stated that imprecise information about the capabilities of the rocket as well as its flight environment contributed to the accident. Several inaccuracies in data modeling for this test led to an inadequate control system for the particular Pegasus rocket used, though no single factor could ultimately be blamed for the failure. In the second test in March 2004, the Pegasus fired successfully and released the test vehicle at an altitude of about . After separation, the engine's air intake was opened, the engine ignited, and the aircraft then accelerated away from the rocket reaching . Fuel was flowing to the engine for 11 seconds, a time in which the aircraft traveled more than . Following Pegasus booster separation, the vehicle experienced a small drop in speed but the scramjet engine afterward accelerated the vehicle in climbing flight. After burnout, controllers were still able to maneuver the vehicle and manipulate the flight controls for several minutes; the aircraft, slowed by air resistance, fell into the ocean. With this flight the X-43A became the fastest free-flying air-breathing aircraft in the world. NASA flew a third version of the X-43A on November 16, 2004. The modified Pegasus rocket was launched from a B-52 mother ship at an altitude of . The X-43A set a new speed record of at about altitude,"X-43: Scramjet Power Breaks the Hypersonic Barrier."
''AIAA,'' 2006. and further tested the ability of the vehicle to withstand the heat loads involved.
NASA. Retrieved: August 1, 2011.

Replacements

In January 2006 the USAF announced the

Force Application and Launch from Continental United States The DARPA Falcon Project (Force Application and Launch from Continental United States) is a two-part joint project between the Defense Advanced Research Projects Agency (DARPA) and the United States Air Force (USAF) and is part of Prompt Global ...

or FALCON scramjet reusable missile. In March 2006, it was announced that the Air Force Research Laboratory (AFRL) supersonic combustion ramjet "WaveRider" flight test vehicle had been designated as X-51A. The USAF

Boeing X-51 The Boeing X-51 Waverider is an unmanned research scramjet experimental aircraft for hypersonic flight at and an altitude of . The aircraft was designated X-51 in 2005. It completed its first powered hypersonic flight on 26 May 2010. After t ...

was first flown on May 26, 2010, dropped from a B-52.

Variants

After the X-43 tests in 2004, NASA Dryden engineers said that they expected all of their efforts to culminate in the production of a two-stage-to-orbit crewed vehicle in about 20 years. The scientists expressed much doubt that there would be a

single-stage-to-orbit A single-stage-to-orbit (SSTO) vehicle reaches orbit from the surface of a body using only propellants and fluids and without expending tanks, engines, or other major hardware. The term usually, but not exclusively, refers to reusable vehicles ...

crewed vehicle like the

(NASP) in the foreseeable future. Other X-43 vehicles were planned, but they have been suspended or canceled. They were expected to have the same basic body design as the X-43A, though the aircraft were expected to be moderately to significantly larger in size.

X-43B

The X-43B, was expected to be a full-size vehicle, incorporating a turbine-based combined cycle (TBCC) engine or a

rocket-based combined cycle The RBCC, or rocket-based combined cycle propulsion system, was one of the two types of propulsion systems that may have been tested in the Boeing X-43 experimental aircraft. The RBCC, or strutjet as it is sometimes called, is a combination propu ...

(RBCC)

ISTAR ISTAR stands for intelligence, surveillance, target acquisition, and reconnaissance. In its macroscopic sense, ISTAR is a practice that links several battlefield functions together to assist a combat force in employing its sensors and managing t ...

engine. Jet turbines or rockets would initially propel the vehicle to supersonic speed. A

ramjet A ramjet, or athodyd (aero thermodynamic duct), is a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust. Since it produces no thrust when stationary (no ram air) ramjet-powered vehicles require an ass ...

might take over starting at Mach 2.5, with the engine converting to a scramjet configuration at approximately Mach 5.

X-43C

The X-43C would have been somewhat larger than the

X-43A The NASA X-43 was an experimental unmanned hypersonic aircraft with multiple planned scale variations meant to test various aspects of hypersonic flight. It was part of the X-plane series and specifically of NASA's Hyper-X program. It set s ...

and was expected to test the viability of hydrocarbon fuel, possibly with the HyTech engine. While most scramjet designs have used hydrogen for fuel, HyTech runs with conventional kerosene-type hydrocarbon fuels, which are more practical for support of operational vehicles. The building of a full-scale engine was planned which would use its own fuel for cooling. The engine cooling system would have acted as a chemical reactor by breaking long-chain hydrocarbons into short-chain hydrocarbons for a rapid burn. The X-43C was indefinitely suspended in March 2004. The linked story reports the project's indefinite suspension and the appearance of Rear Admiral

Craig E. Steidle Rear Admiral Craig Eugene Steidle, USN, Ret., (born July 12, 1945) served as the first associate administrator of the Office of Exploration Systems at NASA (now known as the Exploration Systems Mission Directorate), an organization formed to imple ...

before a House Space and Aeronautics subcommittee hearing on March 18, 2004. In mid-2005, the X-43C appeared to be funded through the end of the year.

X-43D

The X-43D would have been almost identical to the X-43A, but expanded the speed envelope to Mach 15. As of September 2007, only a feasibility study had been conducted by Donald B. Johnson of

and Jeffrey S. Robinson of NASA's

. According to the introduction of the study, "The purpose of the X-43D is to gather high Mach flight environment and engine operability information which is difficult, if not impossible, to gather on the ground.""X-43D Conceptual Design and Feasibility Study."
AIAA. Retrieved: August 1, 2011.

References

Notes

Bibliography

* Bentley, Matthew A. ''Spaceplanes: From Airport to Spaceport'' (Astronomers' Universe). New York: Springer, 2008. . * Swinerd, Graham. ''How Spacecraft Fly: Spaceflight Without Formulae.'' New York: Springer, 2010. . * Peebles, Curtis. ''Eleven Seconds into the Unknown: A History of the Hyper-X Program.'' Virginia: AIAA, 2010. .

External links

X-43 Launch NASA Animation

International components of the X-43a

Launch from B-52infrared
* https://web.archive.org/web/20150316013940/http://videoclip.pk/watch_video.php?v=H1M8DKHXN2HO {{DEFAULTSORT:Nasa X-43 2001 in spaceflight Aircraft manufactured in the United States 2000s United States experimental aircraft Proposed reusable launch systems NASA aircraft Hypersonic aircraft Scramjet-powered aircraft Aircraft related to spaceflight