A LEGEND'S ENCORE!; GLENN RETURNS TO SPACE AT 77.

Byline: John Noble Wilford The New York Times

John Glenn, an astronaut again at 77, returned to orbit Thursday in the space shuttle Discovery for a rendezvous with the memory of a time when exploits of early astronauts held the world in thrall and for a long-awaited encore in the role of durable hero as the oldest traveler in outer space.

At 2:19 (11:19 a.m. PST), after two suspenseful delays, the shuttle's two rockets and three engines ignited in flames and billowing vapors, lifting the seven-member crew, including Glenn, the retiring Democratic senator from Ohio, into an orbit some 345 miles above Earth.

``Liftoff of Discovery with a crew of six astronaut heroes and one American legend,'' intoned Lisa Malone, the countdown commentator, at the moment the shuttle rose into a cloudless blue sky.

Although Glenn's flight had been criticized in many quarters as a publicity stunt and political payoff with little scientific value, an estimated 250,000 visitors to the Kennedy Space Center and surrounding communities, one of the biggest crowds to see a shuttle departure, followed Discovery's ascent, all the way to a vanishing point of light more than five minutes after liftoff. President Clinton and Hillary Rodham Clinton watched from the roof of the Launch Control Center. He was the first incumbent president to see a space launching here since President Nixon watched the takeoff of Apollo 12 in 1969.

In an interview on CNN before the liftoff, Clinton pointed out that this flight - the last mission before the National Aeronautics and Space Administration begins launching the International Space Station - marked the end of an era. ``So John Glenn began this first phase of our space program, and he's ending it just before we start on the space station,'' Clinton said.

A few hours after Discovery reached orbit, Lt. Col. Curtis Brown, the commander, looked over at Glenn.

``Let the record show, John has a smile on his face and it goes from ear to ear,'' the colonel said. ``We haven't been able to remove it yet.''

In his first radio communication with Mission Control, Glenn was ebullient. ``To do a trite old phrase, Zero-G and I feel fine,'' he said, paraphrasing himself from 1962.

Looking over Hawaii

Looking down on the Hawaiian islands, Glenn said: ``Today is beautiful and great. I just can't even describe it.''

More than 36 years ago, Feb. 20, 1962, Glenn, then 40, rocketed aloft here to become the first American to orbit the planet. Alone, squeezed into a tiny Mercury capsule, he made all of three orbits of Earth lasting five hours. Now he was riding the relatively commodious Discovery, with 70 times the room of the Mercury capsule, on a mission planned to last nine days.

Two younger astronauts, Brown and Lt. Col. Steven Lindsey of the Air Force, were at the controls. From his passenger seat in the compartment below the flight deck, Glenn felt the bump at liftoff and the increasing vibration and noise of the first two minutes of surging rocket power, 20 times the thrust of the Atlas rocket that first put him in orbit.

When the two solid-rocket boosters were jettisoned after a little more than two minutes, he felt a sharper jolt and might have caught sight of a flash of light in the tiny compartment window.

In many ways, it was a more comfortable ascent this time. At most, the rocket power exerted on Glenn's body was about three times the normal force of gravity at sea level. This was nothing crushing, certainly nothing like the G-forces from the Atlas, which reached eight times normal levels. As the three shuttle hydrogen engines burned, Glenn could begin to relax to the steady whirring of turbines and fans.

Unbuckled at last

Eight and a half minutes after ignition, he and the other Discovery astronauts had reached orbit and, unbuckling their straps, experienced the floating sensation of weightlessness. On his Friendship 7 flight in 1962, Glenn never got the chance to unbuckle and had no place to stretch out. For the rest of the day, the crew moved slowly about Discovery, opening the cargo bay doors, and activating the systems and scientific instruments in the pressurized Spacehab module in the cargo bay where the astronauts are to conduct many of their medical, biological and materials-processing experiments during the mission.

Generally overlooked in the avid attention on Glenn is the multinational crew, including a Japanese and a Spanish astronaut. The crew is to get busy today with dozens of astronomy observations, tests of hardware for the Hubble Space Telescope, and experiments concerning the effects of a low-gravity environment on living organisms and human physiology.

Much of the scientific work will be handled by Stephen Robinson, an engineer; Pedro Duque, an aeronautical engineer who is representing the European Space Agency; and Dr. Chiaki Mukai, a Japanese physician and medical researcher. Glenn's primary duty will be to act as a test subject for investigations of physiological changes from space flight that appear to parallel similar changes in aging humans. His attending physician for many tests will be Dr. Scott Parazynski.

Issue was survival

Such studies point up one of the sharpest contrasts between this flight and Glenn's first. ``Back then, the issue was not successful experiments but survival,'' Glenn said in a recent magazine interview. ``Doctors weren't sure whether humans could take eight G's going up and coming down. As test pilots, our job was to find out what we could do and couldn't do. Did our eyeballs change shape? Would inner-ear fluid move differently? Could we even swallow?''

Officials said the Discovery was operating normally, but engineers said they were investigating the apparent loss of a small, insulated aluminum panel near the tail. A videotape of the launching showed the panel dropping off two seconds after main-engine ignition. The panel appeared to be the cover over a stowed parachute, which is deployed at landing to slow the shuttle on the runway.

At a news conference, Donald McMonagle, a shuttle official at the Kennedy Space Center, said the incident was not expected to pose any additional risk or cause any change in mission plans. The shuttle could land without the ``drogue chute,'' which was added to the shuttles for extra braking force only after more than 50 safe landings without chutes. And the problem presented ``no hazard to operations of the vehicle in orbit,'' the official said.

A more detailed analysis of the problem is expected to be made today, McMonagle said.

The day of Glenn's second launching broke warm and clear, with no signs of technical trouble on Discovery at Pad 39-B. Before his first mission, Glenn had to wait out 10 weather or mechanical postponements between December and Feb. 20 before he finally lifted off.

The countdown Thursday proceeded smoothly toward a scheduled 2 p.m. (11 a.m. PST) liftoff. At a pause at T-minus-9 minutes, Scott Carpenter, the astronaut who was Glenn's backup pilot in 1962, had some parting words echoing his famous farewell to the Mercury flight, which was ``Godspeed, John Glenn.''

Speaking to the crew, Carpenter said, ``At this point in the count, it seems appropriate to say to the crew, good luck, have a safe flight, and to say once again, Godspeed, John Glenn.''

Launch delayed

But Discovery was not going anywhere yet. Some alarms sounded in the cockpit and were recorded at Mission Control in Houston. The countdown was halted while engineers considered possible problems with pressures in the crew module, and soon established that there was nothing to fear. Then at T-minus-5 minutes, the count was interrupted again as one private airplane and then another were spotted flying into restricted airspace near the Kennedy launching area.

The liftoff seemed trouble-free, until the examination of video recordings revealed the piece of metal that seemed to break loose and hit the nozzle of the shuttle's center engine. Investigators were trying to find out if it was indeed the parachute panel that fell off. It is a piece of waffle-shape aluminum 18 inches wide, 22 inches long and 1.7 inches thick.

One of the most important maneuvers of the mission is to come on the fourth day. The Discovery astronauts plan to release a small satellite called Spartan for two days of observations of the sun's corona, or outer atmosphere, and its effects on the space environment throughout the solar system. The satellite is to be retrieved before the shuttle returns to Earth. The landing is scheduled for Nov. 7 here at the Kennedy Space Center.

The mission is the 92nd by a shuttle since the reusable craft were introduced in 1981. And it is the 121st American flight of astronauts since Glenn made history with his first flight. Shortly after 7 p.m. (4 p.m. PST), Glenn passed his old space-flight record of five minutes under five hours, and he had eight days ahead of him on the return flight he had longed to take ever since February 1962.

CAPTION(S):

3 photos

PHOTO (1 -- 2 -- color) John Glenn, who was the first American to orbit the planet in 1962, blasted off from Cape Canaveral, Fla., on Thursday for an eight-day trip aboard the space shuttle Discovery.

Terry/Renna/Associated Press

(3) Astronauts Steve Robinson, left, and Chiaki Mukai, flank John Glenn during the ascent stage Thursday.

Associated Press