A solid-fuel rocket motor designed for German and Swedish space experiments has successfully completed its third and final qualification test, Thiokol Corp. officials say.

The 30-foot-long Castor IVB motor, loaded with 21,982 pounds of propellant, was test-fired Wednesday at the Redstone Arsenal in Alabama. The other two qualification tests were conducted in June and September.The motor, which will be used with experiments requiring zero or extremely low gravity, now will go into production.

Thiokol is working under an $11.4 million contract to deliver 10 of the Castor IVB motors to the German-Swedish Maxus program. The Utah-based company will deliver the initial single-stage motor at the end of this month, Wendy Dimond, spokeswoman at Thiokol's Huntsville Division, Huntsville, Ala., said Thursday.

The first Maxus launch is scheduled for April 1991 from Sweden, Dimond said. The rocket will provide commercial and government researchers with up to 15 minutes of micro-gravity time for a variety of scientific payloads before it returns to Earth, she said.

It has a payload capacity of 770 pounds.

Motors in the single-stage Castor series have been used in the Delta and Delta II unmanned launch program.