A booster rocket designed for use in an eventual U.S. missile defense system was successful Friday in its first flight test, the Pentagon announced.

The prototype three-stage booster rocket was launched from Vandenberg Air Force Base, Calif., about 1 p.m. PDT and flew about 3,000 miles before splashed down in the Pacific Ocean, said Cheryl Irwin, a Pentagon spokeswoman.

The test did not include an attempted intercept of a missile. The first attempted intercept using the prototype booster rocket is scheduled for 2002 or 2003, Irwin said.

The Pentagon has been using modified versions of older rockets in its intercept tests, including a successful intercept over the Pacific on July 14.

In an intercept test, the booster rocket carries a device called a kill vehicle, which detaches from the booster during the final stage of flight and steers itself into the path of the target missile.

In Friday's flight the rocket carried a mock kill vehicle to simulate the mass and weight of an actual one.