The failure of ground equipment caused the scrub of a weekend test-firing of the redesigned space shuttle booster rocket, officials said, tentatively rescheduling the test for Wednesday. The test would take place at Morton Thiokol Inc.'s test bay 25 miles west of Brigham City, Utah, four days after a test-firing was halted Saturday just one second before ignition, said Rocky Raab, a spokesman for the rocket manufacturer. The test would be the second of four full-scale booster demonstrations required before shuttle missions resume in June. The rescheduling came after two days of tests by engineers who determined that a problem with ground-support circuitry caused the failure of the ignition-control system. The system's "safe and armed" valve, a device designed to prevent the rocket from firing when it is in its "safe" position, failed to open properly, Raab said.