CAPE CANAVERAL, Fla.--Space shuttle Discovery carried the American flag back into space yesterday after a 32-month absence, its five astronauts riding a 700-foot tail of flame from rockets meticulously redesigned after the Challenger disaster.

"Everyone certainly stood tall today," said Kennedy Space Center Director Forrest S. McCartney as Discovery settled into orbit, 184 miles above earth.

Six hours after liftoff the crew accomplished the main mission of its flight, release of a satellite that will give NASA nearly constant communication with future shuttle missions.

It was the first launch since the Challenger explosion with its toll of seven lives on a cold winter day shocked the nation and stopped the manned space program in its tracks.

"We sure appreciate your all getting us up in orbit the way we should be," Discovery's commander, Navy Capt. Frederick Hauck, told Mission Control. "We're looking forward to the next four days--we have a lot to do and we're going to have a lot of fun doing it."

Lift-off was the first and most important milestone, but more was at stake than simply getting into space. The two-year grounding of the shuttle fleet set back the nation's satellite delivery capability, and the release of a communications satellite was the main order of business in orbit, several hours after launch.

The giant Tracking and Data Relay Satellite is a $100-million twin of the craft that was destroyed aboard Challenger.

In Washington, President Reagan praised the launch, saying the shuttle was "headed into orbit and America is back in space." He saluted the bravery of the crew and added, "We ask God to bless this important voyage."

Launch, at 11:37 a.m. EDT, came only after NASAwaived weather guidelines to allow for flightthrough some lighter-than-usual Florida winds. The98-minute delay simply heightened the tension asNASA unveiled a spaceship that underwent more than400 modifications since the Challenger flight.

Just how well the Discovery's booster rocketsperformed in their new design awaited detailedanalysis. But J.R. Thompson, who directed the workfrom the Marshall Space Flight Center in Alabamasaid, "From everything I see, everything looksgreat."

Hauck's veteran flight crew consisted of AirForce Col. Richard Covey, Marine Lt. Col. David C.Hilmers; John M. Lounge; and George D. "Pinky"Nelson. Landing is scheduled for Monday at EdwardsAir Force Base in California.

The astronauts had said all along they weretreating the mission as a test mission--a"shakedown flight," in the words of Covey--andthey quickly ran into first-flight problems. Awater evaporator that provides cooling to the shipduring the climb to space and return to Earth waspartly clogged with ice. And a device thatprovides electrial power to move an orbitalsteering engine was not working.

Neither problem was critical. Flight DirectorGary Coen said engineers were devising ways ofthawing the evaporator before it is needed againand that backup power was available to turn thesteering engine.

To the delight of the approxiamtely 250,000people gathered on river banks and highways and anecstatic NASA team in Launch Control, Discoverylifted off its seaside pad and streaked intocloudy skies. It remained in view less than a halfminute, but the tension was considerable and thesight was unforgettable.

Discovery, an American flag on its left wing,was making its seventh spaceflight.

Anxiety was highest as the ship went through a30-second period of severe aerodynamic stress. Itwas during this stage of the flight that one ofChallenger's booster rockets failed and triggeredthe January 28, 1986 catastrophe, 73 seconds afterlift-off.

Some television viewers reported what theythought was an errant flame shooting from the leftbooster rocket about 90 seconds after lift-offyesterday. Officials said an analysis revealed aharmless phenomenon that causes flame from theexhaust to "climb" up the side of the rocket.

"It was not particularly unusual," said NASA'sSteve Nesbitt.

The analysis that followed the Challengerdisaster led to 56 major and more than 400 minorhardware modifications--and a new, moreconservative launch procedure. Conservative ornot, NASA launch supervisor Robert Crippen granteda waiver of wind guidelines to move the launchforward. NASA said he met with his 21-personoversight team, reviewing an analysis of the windsituation, before approving the waiver