RETURNING TO TRIED AND TRUE; NASA FINDS NEW DESIGNATION IN PAST.

Byline: Jim Skeen Staff Writer

In much the same way NASA learned about supersonic flight, the agency is returning to ``X-planes'' to learn about reusable space-launch vehicles.

Like it has done since 1947 when Chuck Yeager broke the sound barrier in the X-1, or during the 1960s in the X-15 rocket planes, NASA is planning to use X-planes - experimental aircraft - to test technologies and operations practices that will lead to more affordable space flight.

And as it did during the Golden Age of flight test in the 1950s and 1960s, NASA is looking to do much of its X-plane work at Edwards.

``Today's current launch vehicles are stretched, squeezed and liposuctioned to the maximum limit. We need to do something better,'' said Gary Payton, NASA's deputy associate administrator for space transportation technology. ``We need a new set of X vehicles to teach us how to use reusable launch vehicles.''

Three NASA X-plane programs are in various stages of development and all three will have test flights at Edwards.

The most expensive, and perhaps the most ambitious of the X-planes, is the X-33, a $1.1 billion experimental aircraft designed to test technologies for a reusable spaceship called VentureStar being developed by Lockheed Martin.

More than 70 percent of the wingless, wedge-shaped craft has been assembled in a leased complex at U.S. Air Force Plant 42, and tests are under way at NASA centers across the United States on components like the fuel tanks, computer software and the revolutionary rocket engine.

Originally scheduled to fly this year, the X-33 now is scheduled to make its maiden flight in July 2000 from Edwards to an Army airfield at the Dugway Proving Grounds in western Utah - a 450-mile flight that will take 14 minutes.

In its last flight, to Montana, the X-33 will zoom as high as 250,000 feet - 47 miles, or about six miles below the 280,000 feet at which the Air Force awarded its X-15 pilots astronaut wings in the 1960s.

Nearly the size of the space shuttle but piloted by computers on the ground, the X-33 will test technology needed for the VentureStar reusable spacecraft.

The VentureStar is called ``reusable'' because it will go into space and come back in one piece, without dropping rocket stages to burn up in re-entry like the Apollo moon rockets, or even shedding boosters and external fuel tanks like the space shuttles.

NASA hopes that reusable spacecraft will lower the costs and the accident rate in putting satellites and other cargo into space. Launching them would be more like flying an airplane rather than assembling a new rocket for each mission.

The completed X-33 is scheduled to be rolled out of its assembly building in January and taken to a new launch site at Edwards. There it will undergo vibration tests, and workers will load and unload its fuel three times, then fire its engines twice in preparation for the July launch.

The workhorse of the new X-planes will be the X-34, an experimental rocket plane designed to reach speeds of 5,600 mph.

The $85.7 million X-34 program has three main goals: Demonstrate new and efficient methods of preparing a spacecraft for flight; evaluate new technologies aimed at lowering the cost of getting into space; and carry experiments that need a high-speed host.

``We want vehicles that are not only valuable because of the technology embedded in their design, but ones that can carry experiments, too,'' said John London, program manager from NASA's Marshall Space Flight Center in Huntsville, Ala.

Like the famous X-15 rocket planes of the 1950s and 1960s, the X-34 would be carried aloft beneath a larger airplane then released and its rocket engine ignited.

After a free fall of about five seconds, the X-34's engine would then power the rocket to its planned speed and altitude - up to 250,000 feet.

After the engine burnout, the X-34 would dump its excess fuel and then return to Earth for a landing under the control of its onboard computers.

One of the key program goals for the X-34 is to show that launch vehicles can be prepared for missions in a short period of time, rather than the several weeks needed to prepare a space shuttle for a mission. During the program, NASA wants to see two X-34 flights conducted with a 24-hour period.

Flights ranging from more than 4.5 times the speed of sound up to eight times the speed of sound will be conducted from Edwards.

The newest of the X-planes is the X-37. The vehicle will be the first that will be tested in both space and in the atmosphere.

The X-37 will be an unpiloted, computer-controlled test craft capable of traveling up to Mach 25 - about 17,500 mph. The X-37 will be more than 27 feet long and will have a wingspan of 15 feet and a 4-foot-by-7-foot experiment bay.

NASA and Boeing plan to launch the X-37 five times from Edwards.

If all goes well, the X-37 will be taken into orbit by a space shuttle in late 2002. There are two space flight tests planned for the X-37, one lasting two days and another lasting 21 days.

A landing site has not been selected yet for those missions, but NASA is looking at Edwards.

The National Aeronautics and Space Administration and Boeing will pretty much split the cost of the $173 million program. The Air Force will contribute $16 million for the effort.

Assembly, integration, checkout and tests are planned at Boeing sites in Palmdale and in Seal Beach, officials said. Assembly work will begin in 2000.

The X-37 actually will be a larger, more capable version of the X-40A, an unpowered Air Force research aircraft that was also built by Boeing. The X-40A does not have the rocket engine, the experiment bay, thermal protection materials and other spacecraft systems planned for the X-37.