THAT'S ROCKET SCIENCE; UPGRADES PONDERED BEFORE X-33 DEBUTS.

Byline: Jim Skeen Staff Writer

Before the $1.2 billion X-33 rocket plane has even rolled out of its assembly hangar, NASA and Lockheed Martin are considering scheduling a second series of test flights.

The flights would be aimed at further reducing the technical risks of building a reusable spaceship by testing new materials and components even more advanced than those now in the wedge-shaped unmanned rocket craft.

``The improvements we are looking at generally fall in two categories: weight reduction and lower life-cycle costs,'' said Lockheed Martin spokesman Tony Jacob.

Some parts of the X-33 vehicle would be replaced after the initial test flights next year.

For the second round of test flights, the vehicle would be equipped with materials for which technologies have been maturing since the craft was initially built.

For example, metal components would be replaced with lighter-weight carbon composites, and there would be some new engine components, a more advanced thermal protection system and improved electronic gear.

Thinking of a modified X-33, some people are dubbing it X-33B.

The initial test flights, scheduled to begin next summer, will test a number of technologies that Lockheed Martin envisions using on a reusable spaceship called VentureStar.

Lockheed Martin expects VentureStar to revolutionize the space industry by dramatically reducing the cost of getting people and goods into space. Described as a craft with a single stage to orbit, the VentureStar will not drop booster rockets as the space shuttle and conventional rockets do.

Neither will the X-33, although it will fly just to the edge of space - not into orbit.

Among the technologies to be tested during the X-33's initial flights are those incorporated into the craft's aerospike rocket engines.

Instead of bell-shaped exhaust nozzles, like those on conventional rockets, the aerospike uses the atmosphere as part of its nozzle, with the surrounding airflow containing the exhaust plume. This allows the engine to adjust during flight to optimize performance, while traditional engines cannot compensate for atmospheric changes.

The X-33 is powered by two aerospike engines, each with 20 combustion chambers. The X-33 will steer itself by varying the thrust from the chambers.

For the second round of flight tests, among the components being considered for replacement with carbon composite are copper rocket exhaust ramps and pumps that were originally designed in the 1960s for the Saturn V space booster, which propelled the Apollo moon missions.

``It's a new concept in terms of us adapting it for a launch vehicle,'' Daniel Mulvill, NASA's chief engineer, said about using the lighter-weight material. ``We need to explore its performance and its robustness.''

Also to be tested would be microminiature electronic gear to help guide the unpiloted experimental aircraft, officials said.

No cost estimates for a second round of flight tests were available. There have been no negotiations between NASA and Lockheed Martin for the additional flights yet.

The initial flight tests are scheduled to begin in July.

The X-33 will make its first flights from Edwards Air Force Base to the Dugway Proving Grounds in Utah. Each of the 450-mile flights is expected to take about 14 minutes.

Later flights will go to the Malmstrom Air Force Base near Great Falls, Mont., about 950 miles from Edwards. Those flights will each take about 24 minutes each.

CAPTION(S):

2 Photos

PHOTO (1 -- ran in Simi and Conejo edition only) The X-33 rocket plane is being assembled in Palmdale. Even before the first test flight, a second round of tests is being considered.

(2 -- color in AV edition only) Although suborbital, the X-33 being built in Palmdale may be a forerunner to a spacecraft that will not drop booster rockets.