Rocket Dreams

The experimental rocket engine crucial to NASA’s future space missions made its debut Tuesday in a hangar at Boeing Co.’s Rocketdyne plant here, where it has been in development for three years.

The engine, radically different in design from those previously used to launch spacecraft, was built to power the X-33 test vehicle, scheduled for its first launch next year at Edwards Air Force Base.

The aim of the X-33 project is to test the engines and other innovations planned for VentureStar, NASA’s next generation of relaunchable, manned space vehicles.

“This is a tremendous day,” said Byron Wood, a veteran rocket engineer and head of the Rocketdyne division, at a news conference attended by several dozen employees who worked on the X-33 engine.

“The only thing that will beat this is seeing it fire for the first time,” Wood said.

That test is scheduled to occur next month at NASA’s Stennis Space Center in Mississippi.

The main engines now used to launch the space shuttle are jettisoned after liftoff. This new engine, called an “aerospike,” is a permanent part of the space vehicle and can be refueled for repeated launches.

Unlike conventional rocket engines with thrusters that push gases out a bell nozzle, the aerospike design resembles an upside-down bell with the thrusters on the outside. Its liquid hydrogen thrusters--10 on each side--were designed to shoot hot gases down curved ramps (also called spikes) to not only propel the rocket, but also steer it, officials say.

“We were able to get rid of all the mechanical things that were used to steer earlier rockets,” Wood said before the news conference. “It allowed us to make the engine much more compact and aerodynamic.”

Development of the copper-coated ramps, which will have to sustain both tremendous thrust forces and temperatures as high as 4,000 degrees, took longer than expected--the engines were initially scheduled to be at the point they are now in the fall of 1998. But on Tuesday, Wood predicted the engine program, which to date has cost about $30 million, will not be substantially over budget “when the costs are amortized over time.”

The solution to the ramp problem involved finding ways to bond the copper to a honeycombed steel platform. “Copper is very good at directing the thrust,” Wood explained, “but on its own, it’s not very strong.” The engine is further strengthened by titanium struts.

Lockheed Martin, the company building the X-33 at its Skunk Works facility in Palmdale, is also behind schedule on the project. That company’s biggest problem occurred late last year when a hydrogen fuel tank designed for the vehicle broke apart.

The first, computer-piloted flight of the X-33--initially scheduled for March of this year--is now scheduled for July 2000. That first flight, a suborbital mission, is supposed to launch from Edwards and land 14 minutes later at Dugway Proving Ground in Utah, about 450 miles away.

Later X-33 flights are supposed to reach Malmstrom Air Force Base in Montana, about 950 miles distant. All X-33 missions will be unmanned.

Wood said he and other Rocketdyne engineers began working on Aerospike engine designs about 30 years ago. “We thought they would go on the space shuttle,” he said. “The world wasn’t ready for them.”

Not everything about the engine is new. A substantial part of its exhaust system was recycled from J2 engines Rocketdyne made for the Apollo moon program. “They were in storage,” Wood said. “We took them out and modified them.”

The engine Rocketdyne unveiled Tuesday will never fly. “It’s for extensive testing only,” said Steven Bounley, director of the plant’s propulsion program.

The next two made at the plant will be installed on the X-33. Together, they are designed to provide the craft with 412,000 pounds of thrust at launch.

If all goes according to plan on the X-33 project, Lockheed Martin officials say the first VentureStar, which will be about twice the size as the X-33 and able to carry a crew, will be built in 2004. The VentureStar, which NASA hopes will eventually replace the space shuttle as the agency’s primary space vehicle, will carry eight aerospike engines capable of generating 3.5 million pounds of thrust.

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Linear Aerospike Engine

The aerospike engine unveiled Tuesday by Boeing Rocketdyne is radically different in design and much more efficient that conventional bell nozzle engines. This engine is being produced for use on the Lockheed Martin Skunk works X-33 vehicle, which will have two aerospike engines. Lockheed Martin’s planned full-scale reusable launch vehicle, the VentureStar, will have seven aerospike engines.

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Source: Boeing; Researched by ROGER KUO / Los Angeles Times