Four astronauts flew the new space shuttle Challenger on its maiden flight into Earth orbit today, and late tonight they deployed in space a 5,000-pound satellite that is expected to revolutionize space communications.

Ending almost three months of delays that included five postponements, Challenger and its crew of Paul J. Weitz, Karol J. Bobko, Story Musgrave and Donald H. Peterson roared from Earth into cloudless Florida skies less than one-tenth of a second behind schedule at 1:30 p.m. EST.

About 11:30 p.m., the $300 million Tracking Data and Relay Satellite, first of three identical satellites to be used by the United States to provide almost global communications with all of its earth-orbiting satellites for the next 20 years, was thrust into orbit from Challenger's cargo bay.

About an hour later, after the astronauts maneuvered Challenger about 32 miles from the satellite, a huge rocket engine attached to the satellite was fired to boost it to a permanent position 22,400 miles above the Earth on the equator off the northern tip of Brazil.

On liftoff today, Challenger flew in the same flawless fashion that the first shuttle Columbia did on its five flights that inaugurated shuttle service over the last two years.

"We're thankful that America's space fleet doubled itself today," launch operations director Alfred D. O'Hara said at the Kennedy Space Center an hour after liftoff. "We've got two veterans now, Columbia here on the ground being redone for flight and Challenger in space where it belongs."

Showing no sign of the engine trouble that forced four of its five launch postponements, Challenger was in orbit 10 minutes after liftoff. Hydrogen and oxygen leaks that plagued Challenger's engine testing clearly had been left behind.

"There were no leaks at all on those engines, and the guys who deserve the credit for that and who busted their backs on it are the engine folks," O'Hara said. "They've worked day and night recovering from the problems we've had."

About the only concern launch directors had in the hours before liftoff was whether the jet stream that forced hazardous wind conditions 40,000 feet above Cape Canaveral would move north as forecast. Halfway through the final countdown this morning the jet stream was moving away, and upper-air winds were falling dramatically.

"The winds cooperated perfectly," flight director Jay Greene said at the Johnson Space Center in Houston. "We had no loads on the vehicle as it flew through altitude."

O'Hara explained, "It was touch and go through the night on those winds, but this morning it turned right around. It was a beautiful count and a beautiful launch."

The astronauts certainly seemed to think so as they left Earth. When Challenger's two solid-rocket engines burned out and fell away from the spaceliner, Weitz called out: "Boy, that was something. We recommend this heartily."

The overriding goal of Challenger's voyage, scheduled to climax at 1:46 p.m. EST Saturday with a California landing, was the safe and precise deployment of the Tracking Data and Relay Satellite.

The astronauts pushed the satellite out of Challenger's cargo bay by firing six explosive bolts holding it to a metal table tilted at a 59-degree angle from the bay floor. The force of the deployment in airless space hurled the satellite a mile or two from the shuttle.

When Challenger was far enough from the satellite so that its engine exhausts would cause it no damage, the astronauts ignited engines to push the shuttle another 30 miles from the satellite.

The satellite's onboard solid-rocket motor then ignited and guided it toward permanent orbit. The process of moving the satellite to its permanent perch will require a second engine burn early Tuesday morning and 16 hours of maneuvering by remote control from Earth.

A satellite identical to that carried into orbit today is to be launched in August on the eighth shuttle flight, Challenger's third, for positioning over the Pacific Ocean southwest of Hawaii. A third satellite for use primarily as a spare is to be orbited over the Pacific just west of South America next year.

The new network would quadruple the portions of the globe from which U.S. satellites could communicate with Earth and the amount of time for communication.

It would also permit around-the-clock communication with the orbiting Landsat satellite, the Spacelab due to fly on the ninth shuttle flight in September and the space telescope scheduled to fly in 1985.