WASHINGTON -- A test version of the X-33s radical new rocket engine has been installed in its Mississippi test stand, the engine test director told space.com Tuesday. "It was installed in the test stand July 26th," Steve Nunez, X-33 Project Manager at the Stennis Space Center, Hancock County, Mississippi said by telephone from the test center.

But the engine was still not fully assembled. Parts were being flown in from the engines maker, Rocketdyne, in Canoga Park, California. The Linear Aerospike Engine will be subjected to a series of tied-down tests in the stand as soon as assembly is completed, Nunez said. The new rocket arrived at Stennis near the Mississippi coast during the weekend of July 10th and was accepted by NASA formally July 13th for test firings.

Nunez outlined a multi-part firing program that will begin with a pair of ultra-short, 0.8-second bursts from the rocket. "These are firings to basically verify combustion," Nunez explained. Following these, two other firings of 2.5-second duration are planned, followed by a pair of tests at 2 to 5 seconds each.

According to Nunez, these will be followed by running the engine to 80 percent of its thrust. The rocket can be throttled up and down in power settings during a launch of the X-33 space vehicle, depending on the winds, weights, and other loads upon the vehicle that day. Additional test firings will probe "various aspects of the flight profile," Nunez said, leading up to full power firings. NASA plans currently call for 14 firings of the no. 1 developmental engine now at Stennis, followed by six firings of the no. 2 engine and five firings of engine no. 3.

This complete series of single engine firings are to be completed before the end of the year, Nunez said. Next year will see the first clustered testing of two of the Aerospikes mounted together on a rocket stand. These firings will gather data on how well the system performs in multi-engine configurations.

The X-33 flight test vehicle, is due for rollout from its Lockheed Martin Skunk Works facility in Palmdale, California next January, with first test flight planned in July, 2000. The space vehicle will test a single stage suborbital craft for the first time at the edge of space. The X-33 will use a cluster of four of the Aerospike designs to power its flights.

A fully operational version of the X-33, called VentureStar, would be an orbital payload-carrying launch vehicle that would be, like the smaller X-33, fully reusable. VentureStar would use seven of the Aerospikes firing in parallel to insert itself into orbit under current designs. Neither the X-33 nor VentureStar would carry people, although VentureStar could carry a people-carrying module in future versions.