Astronauts Sally K. Ride and John M. Fabian today demonstrated what the space shuttle is all about by deploying a $40 million Indonesian communications satellite in the black seas of space with the ease of two people tossing a Frisbee at the beach.

Crossing the South Atlantic Ocean at the end of their 18th orbit of the earth aboard the shuttle Challenger with three other astronauts, Ride and Fabian tapped out messages on their cockpit consoles that set the five-ton cylindrical satellite spinning in the cargo bay.

Minutes later, as they crossed north toward the equator near the Indian Ocean, they sent another series of messages that ordered the satellite out of the bay on the first leg of a four-day trip that will place the satellite over the center of the more than 13,000 islands that make up the Republic of Indonesia in the South Pacific Ocean. The National Aeronautics and Space Administration was paid $11 million for the delivery.

"Okay, that's 4 for 4," Fabian said in reference to the two satellites he and Ride deployed on this seventh shuttle flight and the two identical satellites deployed last November by the crew of the fifth shuttle. Said Ride: "All we felt was the kick when it left the bay."

After beaming back a television broadcast of the silver-and-blue satellite spinning silently away from the shuttle, Ride, Fabian and astronauts Frederick H. Hauck and Norman E. Thagard appeared on the screen lined up in the cockpit wearing blue T-shirts with white lettering that read: "TFNG. We Deliver."

The TFNG stands for Thirty-Five New Guys, the number recruited for the astronaut class of 1978, of which all four rookie astronauts are members. The only crew member without a T-shirt was Commander Robert L. Crippen, who stayed out of sight of the camera most of the time.

"That's all right, Crip," astronaut Terry J. Hart said from the Mission Control Center in Houston. "We can tell you're a steely-eyed veteran from here."

The second straight satellite deployment by the Challenger crew in two days impressed the flight directors at Mission Control as much as it did the crew in orbit. Saturday, the shuttle crew deployed a seven-ton communications satellite for the Canadian government.

"The crew is performing exceptionally well; they're getting the job done and getting it done on time," flight director Tommy Holloway said at the Johnson Space Center in Houston. "All the activities today were accomplished without fanfare, which gives us a glimpse of what shuttle activities are all about and will be in the future."

Once the second satellite left the cargo bay, crew members clearly began to relax. They turned on their tape recorder and played the Beach Boys singing "Surfin' Safari" and Billy Joel's recording of "She's Always a Woman to Me." Hart's reply to the musical selections: "We got a guy here says he has a truck sounds like the music you just played."

The astronauts even had their minds on food today instead of work, especially Ride, the first woman to wear the stars and stripes in space.

"What are you guys eating?" Ride asked Hart soon after the second satellite had been deployed and was on its way to its final destination. Hart replied: "Lots of yogurt and crackers." Ride asked: "What, no burritos?" Answered Hart: "Not today, I got up too early."

In moments, the conversation was back to food. Hart asked Ride: "You guys haven't eaten all those jellybeans, have you?" Said Ride: "I like jellybeans." Answered Hart: "Make sure you save some for post-flight."

The last exchange clearly was a reference to President Reagan's announced visit to the Kennedy Space Center on Friday when the Challenger crew is scheduled to return to earth and land the 100-ton spaceliner in Florida, its launch site, for the first time. Five of the first six shuttle flights have landed at Edwards Air Force Base in California; the sixth was at the White Sands Missile Range in New Mexico.