NASA'S ROBOTIC SCRAMJET SET TO FLY TEST OF THIRD X-43 TO BE LAST IN SERIES.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - NASA is planning for the flight this fall of its third hypersonic X-43, a wingless, wedge-shaped pilotless craft that is expected to hit more than 7,000 mph over the Pacific Ocean.

After a March flight in which another X-43 reached about 5,000 mph, the National Aeronautics and Space Administration is preparing the third and final flight of a $230 million program researching an experimental type of jet engine that could power future space vehicles and military aircraft.

``It was extremely successful for such a high-risk event,'' Joel Sitz, NASA Dryden Flight Research Center's X-43A program manager, said about the March flight, which set a world speed record for a jet-powered craft.

The next flight is being planned for October and, as the last one, will originate from NASA's Dryden Flight Research Center.

The program's goal is to advance technologies for a scramjet engine: an ultra-high-speed engine drawing oxygen for combustion from the atmosphere rather than carrying it as a rocket ship does. By not having to carry oxygen, a spacecraft could save fuel weight and carry more equipment.

The scramjet concept has been the subject of analysis and ground tests for years. The data from the March flight will help NASA researchers validate wind-tunnel tests and other analyses on hypersonic flight.

One challenge facing the upcoming flight is that the heat on the X-43A will approach 4,000 degrees, almost double that of the March flight, Sitz said.

Additional thermal protection is being put on the vertical tail and on the leading edges of the aircraft. The thermal protection is a coating similar to what is used on the space shuttles.

On the record-setting March 27 mission, NASA's modified B-52 bomber carried a 12-foot-long X-43A aircraft out to the test range over the Pacific Ocean about 50 miles off the California coast. A winged Pegasus booster rocket pushed the X-43A to its test altitude of about 95,000 feet, where it separated from the booster and flew freely under scramjet power.

The 5,000 mph speed, fastest ever for a craft powered by a jet engine, was twice as fast as that of the famous SR-71 Blackbird spy plane, which flew at speeds of about 2,200 mph.

The X-43A's engine burned only for a few seconds, but it was enough to provide NASA with what researchers called a treasure trove of information on scramjet flight. After its engine shut down, the X-43A flew a set of maneuvers all the way to its splashdown onto the Pacific Ocean.

``We got data down to 40 feet above the water,'' Sitz said.

The fall flight will be conducted in much the same fashion, except that it is expected to reach a higher altitude of 110,000 feet.

The first X-43 aircraft had to be blown up in June 2001 over the Pacific Ocean by a self-destruction mechanism when the Pegasus booster rocket carrying it went out of control after its fins came off.

A number of factors apparently contributed to the 2001 failure, including the B-52's dropping the rocket at a 23,000-foot altitude, where the atmosphere is much denser than it is at 40,000 feet, where Pegasus rockets are launched when they go into space.

The X-43 test program is NASA's first dedicated to hypersonic research since the last X-15 rocket plane flight at Edwards Air Force Base in 1969. The rocket-powered X-15's fastest flight was Mach 6.7, or about 4,520 mph, with W.J. ``Pete'' Knight at the controls.

Plans for follow-on versions of the X-43A have been canceled by NASA as the result of funding for President George W. Bush's new space initiative to return men to the moon.

NASA is in the process of determining how to continue its hypersonics research.

Sitz said he would like to see the agency pursue an effort to integrate four engine types - jet turbine, ramjet, scramjet, and rocket - into a reusable vehicle that could be flown as many as 50 times a year.

While NASA considers its course in hypersonic research, the Air Force is pressing ahead with efforts to develop such technologies for use in future aircraft that would be capable of reaching any spot in the world within a couple of hours.

The Air Force's ultimate goal is to develop an aircraft capable of flying at least 3,500 mph and carrying 12,000 pounds of cruise missiles or small-diameter bombs.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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Ground tests on a drone at NASA's Dryden Flight Research Center in 1999 prepare for X-43 scramjet flight testing, with a third flight planned for autumn.