Modern-Aviation

Although three X-43A flights were planned, only two were successful, with the first aircraft crashing into the sea. The initial attempt was on 2 June 2001. At first all went well: the stack was attached to the wing of NASA's B-52B, which took off from Dryden. Once over the Pacific, the Pegasus rocket ignited and successfully separated from the B-52B. Around 12 seconds after separation, disaster struck - the rocket experienced a control problem which led to the rudder controls failing. Moments later the starboard fin was torn from the vehicle, followed by the port fin, then the rudder and wing. This caused the stack to spin out of control and veer off course as it went transonic. NASA ground controllers decided that it would be safest to destroy the two craft, which were blown up at 13:45 Pacific Time, by onboard explosives. Unfortunately, the two craft were destroyed before the X-43A could begin flying independently.

A number of factors caused the rocket failure, the main once being the malfunction of the booster's flight control system, which failed because of poor design and insufficient wind tunnel testing. Wind tunnel test data later revealed the need for more powerful booster fin actuators to withstand the higher aerodynamic loads. In addition, changes were made so the rocket could launch at its normal altitude of 40 000 ft (12 200 m) instead of the 23 000 ft (7 000 m) used on the first flight, thus reducing aerodynamic loads even further.

The X-43A's second flight went successfully on 27 March 2004. It began at 12:40 pm Pacific Standard Time when the B-52B took off from Dryden with the stack mounted under its wing. Just before 2:00 pm the stack was released and soared up to around 95 000 ft (29 000 m). Once the rocket reached its optimum speed, the X-43A was released and its air intake opened and the engine was ignited before it accelerated away from the rocket. The scramjet burnt for eleven seconds, during which the X-43A travelled at a phenomenal Mach 6.83 and covered 15 miles (24 km). For nearly ten minutes after engine burnout, controllers manoeuvred the X-43A as it glided down towards the Pacific and lost speed. All through the flight unique test data was gained, thus achieving one of the chief aims of the Hyper-X programme: to obtain data that could not be gained in a wind tunnel or on the ground.

The X-43A easily broke the record for the fastest free-flying air breathing aircraft in the world. A ramjet-powered missile that flew at a little over Mach 5 in July 2001 held the previous record in the same category. The X-43A's accomplishment was instantly recognised by Guinness World Records, who were going to put it into their next book of records. However, the third X-43A's Mach 10 flight easily broke this record.

Like the tip of a giant arrow, the 12 ft 2 in (3.7 m) long, wedge-shaped X-43A was attached to the nose of a modified Pegasus booster rocket on 16 November 2004 and slung under the wing of a former B-52B bomber. The massive aircraft carried the pair, called the 'stack', to an altitude of 40 000 ft (12 000 m) over the Naval Air Warfare Centre Weapons Division Sea Range, just northwest of Los Angeles in the United States. Then the stack was released and the Pegasus booster rocket ignited. It accelerated the X-43A until it reached a speed of over Mach 9 (nine times the speed of sound), or a staggering 6 200 mph (10 000 km/h).

At an altitude of about 111 000 ft (33.5 km) the unmanned X-43A was let loose and its scramjet ignited. Its engine power was enough to allow it to independently carry on the flight at over Mach 9. The X-43A travelled more than 620 miles (1 000 km) before losing speed and power and plunging into the Pacific Ocean. Throughout the flight completely unique test data was gained. A maximum speed of around Mach 9.6 (around 6 800 mph or 11 000km/h) was attained, smashing the previous speed record of an air-breathing jet of Mach 6.83 set by another X-43A in March 2004. The X-43A's third and last flight under the Hyper-X programme ended in success. NASA's Hyper-X programme was designed to turn scramjets into practical, workable technology and to perhaps use them on future aircraft.

The possibilities of scramjet-powered aircraft are enormous, mainly because of their sheer speed. They could one day power long-haul airliners which would dramatically cut journey times - travelling at 9 323 mph (15 000 km/h), an 18-hour trip from New York to Tokyo would become a 2-hour flight. Compared to rockets, they would be cheaper, safer and more flexible and would be able to carry a heavier payload. They would also dramatically improve space travel by cheaply powering reusable orbital space vehicles, allowing more payloads to be sent into space.

RELEASE: 04-59
NASA's X-43A research vehicle screamed into the record books again Tuesday, demonstrating an air-breathing engine can fly at nearly 10 times the speed of sound. Preliminary data from the scramjet-powered research vehicle show its revolutionary engine worked successfully at nearly Mach 9.8, or 7,000 mph, as it flew at about 110,000 feet.

The high-risk, high-payoff flight, originally scheduled for Nov. 15, took place in restricted airspace over the Pacific Ocean northwest of Los Angeles. The flight was the last and fastest of three unpiloted flight tests in NASA's Hyper-X Program. The program's purpose is to explore an alternative to rocket power for space access vehicles.

"This flight is a key milestone and a major step toward the future possibilities for producing boosters for sending large and critical payloads into space in a reliable, safe, inexpensive manner," said NASA Administrator Sean O'Keefe. "These developments will also help us advance the Vision for Space Exploration, while helping to advance commercial aviation technology," Administrator O'Keefe said.

Supersonic combustion ramjets (scramjets) promise more airplane-like operations for increased affordability, flexibility and safety in ultra high-speed flights within the atmosphere and for the first stage to Earth orbit. The scramjet advantage is once it is accelerated to about Mach 4 by a conventional jet engine or booster rocket, it can fly at hypersonic speeds, possibly as fast as Mach 15, without carrying heavy oxygen tanks, as rockets must.

The design of the engine, which has no moving parts, compresses the air passing through it, so combustion can occur. Another advantage is scramjets can be throttled back and flown more like an airplane, unlike rockets, which tend to produce full thrust all the time.

"The work of the Langley-Dryden team and our Vehicle Systems Program has been exceptional," said NASA's Associate Administrator for Aeronautics Research J. Victor Lebacqz. "This shows how much we can accomplish when we manage the risk and work together toward a common goal. NASA has made a tremendous contribution to the body of knowledge in aeronautics with the Hyper-X program, as well as making history."

The flight was postponed by one day when repair of an instrumentation problem with the X-43A caused a delay. When the preflight checklist was resumed, not enough time remained to meet the FAA launch deadline of 7 p.m. EST.

Today, the X-43A, attached to its modified Pegasus rocket booster, took off from Dryden Flight Research Center at Edwards Air Force Base, Calif., tucked under the wing of the B-52B launch aircraft. The booster and X-43A were released from the B-52B at 40,000 feet and the booster's engine ignited, taking the X-43A to its intended altitude and speed. The X-43A then separated from the booster and accelerated on scramjet power to a brief flight at nearly Mach 10.

NASA's Langley Research Center, Hampton, Va., and Dryden jointly conduct the Hyper-X Program. NASA's Aeronautics Research Mission Directorate, Washington, manages it. ATK-GASL (formerly Microcraft, Inc.) at Tullahoma, Tenn., and Ronkonkoma, N.Y., built the X-43A aircraft and the scramjet engine, and Boeing Phantom Works, Huntington Beach, Calif., designed the thermal protection and onboard systems. The booster is a modified first stage of a Pegasus rocket built by Orbital Sciences Corp, Chandler, Ariz.
NASA 16.11.04

The first plane in the series, the X-43A, was a single-use vehicle. Three of them were built. The first was destroyed after malfunctioning in flight; the other two have successfully flown, with the scramjet operating for approximately 10 seconds, followed by a 10-minute glide and intentional crash into the ocean.

The X-43 has set several airspeed records for jet-propelled aircraft, with its fastest record at approximately Mach 9.6 (7,310 mph) (11,000 km/h). 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 was first flown on May 26, 2010, dropped from a B-52. So far, this signals the replacement and end of the X-43 series.