Besides Sen. Jake Garn (R-Utah), the crew of the next space shuttle mission will bring into orbit a grab bag of mechanical toys to see if they behave differently in weightlessness than they do on Earth.

Among the toys to be flown aboard the Challenger Feb. 20 will be a paddle and ball, a windup car, a set of magnetic marbles, a set of jacks, a helix-shaped spring, a gyroscope, a yo-yo and a mechanical mouse the crew has already nicknamed "The Rat Stuff."

"We're serious about this experiment, and we plan to film these toys to see how they act in zero g zero gravity ," astronaut Jeffrey A. Hoffman said yesterday at Johnson Space Center in Houston.

Besides Hoffman and Garn, the crew includes Karol Bobko, Donald E. Williams, Margaret Rhea Seddon, David Griggs and Patrick Baudry, a French scientist who is the first person to train as both an astronaut and a cosmonaut. He spent two years in the Soviet Union training for a flight he never took.

Hoffman, Seddon and Griggs will be in charge of the toys, manipulating and maneuvering them inside the cockpit in their spare time. Griggs and Hoffman will be in charge of the other business: orbiting two communications satellites.

While Garn will have "no toys of my own to play with," he said he would still serve a useful role.

"I'll be wired for all the medical experiments that will be done on this flight and I will help Dr. Baudry and Dr. Seddon" -- both are physicians -- "in their experiments if they ask for it," Garn said.