WASHINGTON -- Troubled by technical snags, the X 33 rocketplane project -- an effort to spark creation of a commercial single-stage-to-orbit vehicle -- is the topic of intense renegotiations between NASA and the lead industrial partner for the project, the Lockheed Martin Aeronautics Company.

The project was started in July 1996, with the un-piloted X 33, first billed to take to the skies in a series of suborbital test hops in July 1999.

Stability of the sleek-looking wedge-shaped craft at various speed ranges, as well as its overall weight, has plagued designers. Novel "linear aerospike" engines that will power the rocket plane also proved troublesome to build.

The philosophy of the X 33 is quite simple: Launch like a rocket, land like a plane.

At the time of the tank problems, the X 33 was supposed to wing its way into the air from an Edwards Air Force Base, California launch site this summer. The date for the vehicle's maiden voyage is now on hold.

For Lockheed Martin, lessons learned in building and flying X 33 are key to validating new technologies and reducing risk for the commercial VentureStar -- the firm's fully reusable, single-stage-to-orbit vehicle.

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Table talk

NASA and Lockheed Martin are conducting the X 33 program under a cooperative agreement, the largest industry cost-sharing venture in NASA's history.

Initially, NASA budgeted $941 million for the project, with Lockheed Martin and its team members investing over $300 million in the program to date, said Gary Grigg, acting manager for communications at the Lockheed Martin Aeronautics Company in Palmdale, California.

When will it fly? "If I gave you an optimistic answer, I'd have probably half a dozen people throw bricks at me."

Hush-hush discussions are now underway between the two organizations, focused primarily on whose picking up the extra costs to get the X 33 back on track and up in the air.

"We are currently in active negotiations with NASA regarding restructuring the X 33 program. As a consequence it would not be appropriate for me to comment on where we are in those proceedings," Grigg said.

How much more money is required to pull the X 33 project out of trouble?

Gene Austin, NASA X 33 program manager at the Palmdale plant where the spaceplane is taking place, told SPACE.com that no number is available now.

"That's something we are in real detailed discussions about at this time," Austin said. "Any kind of number right now would be really premature. Hopefully, in the next few weeks, we'll have a definitive statement on that," he said.

Star performers

At Lockheed Martin's building 704 in Palmdale, last used to construct B 1 bombers, the X 33 continues to take shape.

"We've got about 85 to 90 percent of the hardware in the plant right now," said NASA's Austin. "We're going to press on with completion of all hardware deliveries and continue to assemble the X 33 out on the floor," he said.

Austin said that the X 33's aerospike engines have become "star performers". Over a dozen tests of a single motor have taken place at the NASA Stennis Space Center in Mississippi.

A test stand at Stennis is now being readied for dual engine firings, with final qualification and acceptance of X 33 flight engines occurring this fall, Austin said.

"We hope to have the two flight engines back here in Palmdale early next year," Austin said.

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The fix is in

A decision has been made to replace the X 33's composite liquid-hydrogen propellant tanks with aluminum tanks.

"We are in a fairly flexible position right now," Austin said. Teams are now working toward the aluminum tank design for X 33 to be finalized late next month or early August, he said.

Austin said that the move from composite tanks to aluminum should not be misconstrued. NASA sees great promise in using composites to hold supercold rocket fuel, but there are numbers of technical challenges still remaining, he said.

"I fully expect NASA and industry to pursue additional avenues on developing composite tanks. They have great payoffs. We just didn't quite get there on X 33, yet," Austin said.

Looking for a liftoff, but when?

When will X 33 rocket its way off the ground? Project officials are hesitant to put down a firm date.

"If I gave you an optimistic answer, I'd have probably half a dozen people throw bricks at me," Austin said. Beyond engineering the X 33, financing the project and other issues remain, he said, making it hard to speculate on an actual launch date.

Generation X 33: Visionary -- or wishful -- thinking?

However, according to SPACE.com sources close to the project, legal and safety issues also haunt the X 33's programmatic overhaul.

Test hops of the X 33 over populated areas remain a safety concern. The current test program has the vehicle departing Edwards Air Force Base in southern California, flying first into Utah, with later shots into Montana.

Whether or not the rocketplane should haul along self-destruction devices is under discussion, the source said.

Also, using the new aluminum fuel tanks means a redesign of X 33's innards, due to the way those tanks will contract when they are loaded with supercold propellant.

Lastly, Lockheed Martin is faced with coughing up more funds to assure the X 33 is a technical success.

Stung by the company's recent ill fortunes in building Mars spacecraft, "the company doesn't want another mishap," the source said. "So there's some extra resources needed to make sure X 33 is a success. It hasn't been identified who is going to pay for that -- Lockheed Martin or NASA".