NASA Jet Sets New Speed Record

by Dr. Richard Stimson

in Others

A small, pilotless NASA experimental airplane set a new speed of almost 10 times the speed of sound on Tuesday November 17, 2004. It comes 100 years, 11 months, after the Wright brother’s first controlled flight. The NASA airplane, the X-43A, reached about 6,600 mph during a short flight over the Pacific Ocean that demonstrated that hypersonic flight is possible.

Orville’s first flight on December 17, 1903 was capable of a speed of about 34-mph in still air. On that day there was a head wind of 27-mph so that the ground speed was much slower. Wilbur had no trouble running along side the Flyer, steadying it, while it traveled down the launching rail.

During the early days of aviation, increases of flight speed were relatively slow.

To put this in perspective, by 1909 the Wright airplane demonstrated an average speed of 42.6-mph during the Army flight demonstrations at Fort Myer.

One year later the Wrights built an airplane designed for racing that demonstrated a significant increase in speed. It was clocked at flying over 77-mph with a new eight-cylinder engine. It was the Wright Model R, nicknamed the “Baby Grand.”

Less than 24 years after the first flight at Kitty Hawk, Charles Lindbergh’s airplane, the “Sprit of St. Louis,” was capable of attaining a maximum speed of 125-mph on his solo flight to Paris.

The development of the jet engine resulted in rapid improvements in speed.

An historic breakthrough in speed came on October 14, 1947, when Chuck Yeager became the first person to fly faster than the speed of sound (supersonic flight) flying the Bell X-1. His record-breaking speed was Mach 1.06, or 700 mph, and proved that airplanes can fly safely in the mysterious aerodynamic zone around Mach 1 formerly known as a “sound barrier.”

The SR-71A Blackbird spy plane flew in excess of 2,200-mph, or Mach 3 in 1964.

NASA has been working for the last few years on hypersonic flight, or speeds greater than Mach 5. Among the technical challenges of flying this fast is the development of an engine that can stand the forces necessary to generate hypersonic speed. A conventional jet engine would fly apart at hypersonic speed.

Jet engines operate according to Newton’s Law, that for every action there is an equal and opposite reaction. That means that the faster the jet, the faster the exhaust has to be shooting out of the engine.

In a conventional jet engine the turbine blades that are used to compress air for combustion would fly apart.

The purpose of NASA’s research is to develop technology for a new type of engine known as a “scramjet” that can work at hypersonic speeds. Scramjet is an acronym for “supersonic combustion ramjet.”

A scramjet has no moving parts and achieves compression by sucking in and compressing air at supersonic speeds. It reaches rocket-like speeds, but unlike rockets, it does not need oxygen to ignite the fuel supply. Instead it takes oxygen from the atmosphere.

For a long time experts thought that it was not possible to ignite the fuel in a supersonic air stream. It would be analogous to “striking a match in a hurricane.”

NASA built and tested three unmanned vehicles containing the new engine. They tested three vehicles so that, like the Wright brothers, they could use the lessons learned from each succeeding flight to improve the next one.

Operational testing is particularly essential for the X-43A because, while the Wrights were able to effectively used their wind tunnel to design their Flyer, it is very difficult to test on the ground at hypersonic speeds. While the design of the engine is mechanically simple it is very complex aerodynamically.

The first test flight failed because of a booster rocket problem. The second test established a new world speed record of Mach 7. The last flight, on Nov. 17, broke the previous record by flying at a spectacular Mach 10.

Here is the sequence of events during the last test flight:

Scramjets start to work only at about Mach 6 and therefore must be given a boost. A modified Pegasus rocket provides the boost.

The 12-foot long wedge-shape X-43A, attached to the nose of the Pegasus rocket, was carried under the right wing of a B-52B aircraft to 40,000 feet. It was then dropped about 50-miles off the southern California coast.

The solid rocket motor took the stack up to mach 10 at 110,000 feet.

The motor burned out after 7-8 seconds and pistons pushed the X-43A forward away from the rocket and the higher density of the X-43A made it pull ahead of the Pegasus rocket.

The X-43A engine inlet was then opened and in 3 seconds the engine started firing using hydrogen fuel maintaining a speed of Mach 9.65 at 110,000 feet. This continued for 10-12 seconds. The inlet door then closed 8-9 seconds later for the rest of the flight.

The X-43A then descended while performing maneuvers to test its aerodynamic characteristics. The craft splashed into the ocean after an approximate total flight time of 14 minutes and 850 miles.

What now? Any near term applications of scramjets will probably be military because that is where the money is and NASA has not funded a continuation of the $230 million program. The Wright brothers also received a military contract in 1909.

One of the advantages of a scramjet rocket is that it doesn’t require a heavy, huge oxygen container. Rockets combine liquid fuel with liquid oxygen to create thrust. The larger the rocket the larger the oxygen container in a conventional rocket.

Without the added weight and space, cheaper and easier space missions are possible such as flights to the moon and space stations. Airplanes can cross the Atlantic in 40 minutes.

The U.S. Air Force is researching how to use the technology to create cruise missiles that could reach enemy targets at lightning speed.

Few people in the early days of aviation saw the potential of the airplane. The Wrights themselves didn’t foresee jumbo jets routinely flying across the oceans or space flight.

After World War II, the Dayton Wright Airplane Co., then owned by General Motors, decided to stop building and selling airplanes because they thought there was no longer a profitable future for airplanes after the war.

What the NASA X-43A has done for hypersonics is equivalent to what the Wright brothers did for subsonics 100 year ago. It is amazing what has been accomplished in such a relatively short time.

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