A Midgetman missile - with a first stage built by Thiokol and a third stage built by another Utah plant, Hercules Aerospace - was successfully test-fired into the Pacific Ocean Thursday.

Air Force officers announced that the Midgetman was fired from Vandenberg Air Force Base, Calif., to the Kwajalein Missile Test Range in the Marshall Islands, in the Pacific Ocean. The Kwajalein Atoll is about halfway between Hawaii and Australia."The small ICBM flew approximately 4,000 nautical miles in 30 minutes, landing in its assigned area," said a public affairs officer at Norton AFB, Calif.

Col. Howard J. Mitchell, program director for the Small ICBM, said, "Initial indications are all systems worked properly, and we are extremely pleased with the performance of the missile." The missile shot was to evaluate missile performance, ground and flight software, canister launch system, and launch sequence procedures.

The Midgetman is under full-scale development. The missile is composed of two distinct elements, the missile itself and the mobile launcher.

The Small ICBM is 53 feet long, 46 inches in diameter, and weighs about 37,000 pounds.