An explosion that lit up the night sky like daylight destroyed an underground Titan II missile silo here early today, killing one airman, injuring at least 21 others and sending rural residents fleeing for safety.

The powerful nuclear warhead atop the 103-foot-long intercontinental ballistic missile was catapulted out of the silo and landed about 200 yards away in nearby woods. Air Force inspectors said they had found no evidence of damage to the weapon, or any radiation leaks.

Authorities here, 52 miles north of Little Rock, evacuated an area that stretched 10 miles north of the silo and five miles on either side, rousting about 1,400 people from bed in Damascus and from nearby towns of Bee Branch and Gravesville.

Hours before the explosion, one member of the Air Force mantenance crew -- performing what Air Force officials called "routine" mantenance -- dropped a three-pound wrench socket from scaffolding inside the silo. The tool fell 70 feet bounced off the missile's thrust mount and punctured the first stage of the missile's 10,000-gallon fuel tank.

As maintenance men struggled to neutralize the leak, hauling a truckload of bleach to the site in the hope of stopping any chemical reaction between the fuel and the oxidizer, the volatile fuel exploded. The blast had enough force to blow off the 740-ton silo door of reinforced concrete and steel, turning the silo to rubble, according to Air Force spokesmen.

The airmen were standing nearby, clad in white airtight suits, breathing packs on their backs, rubber gloves on their hands, boots on their feet, preparing to descend into the silo. Eighteen men were injured seriously enough to require hospitalization. An airman from Ohio died at Baptist Medical Center about 6:30 p.m. from shrapnel wounds in the head and stomach. His name was not released pending notification of his family.

"The silo acted like a big gun barrel," said Ed Stallcup, 55, a state Office of Emergency Services duty officer who was monitoring the fuel leak from an underground command bunker in nearby Conway when the silo erupted. "Our man at the site said you could have read a newspaper it was so bright. Seemed like everything that would have taken the missile to Russia went up all at once."

In Washington, President Carter and Air Force Secretary Hans M. Mark portrayed the explosion as a freak accident and said no radioactive material escaped. "The situation is under control," said Carter, just before leaving for Camp David. "There is no indication of any radioactivity." Sen. Bob Dole (R-Kan.) called for a congressional investigation. "If it's not safe and effective, I don't know why you need it," he said.

Arkansas Gov. Bill Clinton said Air Force officials told him that no nuclear explosion could have occurred inside the silo. The Titan II was one of 54 in the nation's nuclear arsenal, all of them capable of delivering the country's largest hydrogen bomb to a target 6,300 miles away.

A number of steps must be taken to activate the nuclear warheads. A series of keys must be used to activate electrical circuits inside the missile and its warhead. This is done only at launch, however, not when the missile stands on guard in its underground silo.

At 6:30 p.m. after the wrench socket fell and fuel began to leak, a maintenance technician noticed vapors and passed the word. A four-man crew in the underground command post 40 feet down a passageway from the missile began its "hazard checklist" and prepared to evacuate, said one SAC official.

Guages indicated the possibility of a fire and the missile crew threw levers that sent water pouring into the silo from tanks above ground. Within 24 minutes after the first signs of the fuel leak, the crew had climbed onto an elevator and escaped. A helicoper than plucked them up and delivered them unharmed to Little Rock Air Force Base 40 miles away.

Meanwhile, at 6:47 p.m., the Air Force notified the state emergency officials of a possible fire in missile silo 47.

By 8 p.m., Little Rock Air Force Base passed the word to state officials that they did not expect a fire or an explosion, according to the Office of Emergency Services logbook. Nonetheless, local Air Force officials suggested evacuating residents within 2,000 feet of the silo.

By Van Buren County Sheriff Gus Anglin insisted residents be evacuated within a one-mile radius and 100 people were herded from their homes and taken to the high school gymnasium in nearby Clinton.

Anglin had been exposed to fumes from a leak at the same Titan II site nitrogen tetroxide, one of the two chemicals that are mixed as propellant for the ICBM, leaked from a storage tank near the silo.

The other chemical is Aerozine 50.

The 1978 leak forced the evacuation of 500 school children, sent four people to the hospital and angered local residents. Two lawsuits were subsequently filed in federal court. Since then, Anglin and Sen. David Pryor (D-Ark.) have been leading a fight to force the Air Force to install an automatic system to warn residents of leaks.

Sid King, general manager of radio station KGFL-AM in Clinton, was an eyewitness to today's explosion. King, who was permitted to remain outside the gate of the silo to broadcast live remote bulletins, said that by midnight last night officials felt the spilled chemicals in the missile silo were manageable and containable.

By 1 a.m., the Air Force had airlifed about 25 airmen to the site to begin cleaning up the leak. About 2:30 a.m., the personnel, dressed in special fire-retardant white suits, prepared to enter the silo. An array of special equipment and trucks containing large generator-powered spotlights had been assembled on the site by this time.

"The personnel disappeared into the silo and I assumed the worst was over. It was chilly that evening, and my back was to the silo, but suddenly my back warmed up and I saw a tremendous flash of light. I whirled around to see this 200-foot column of flames shooting up out of the silo. Then we were hit by the most incredible boom I have ever heard.

"My first thought was that the nuclear warhead had gone off. By then, however, everyone was diving for the ditches. I ran to my car, and dashed five miles up the road to the roadblock. It was there that I learned that the explosion had been caused by the toxic missile propellant.

"It was also then that I realized that all the Air Force men I had seen in their white suits had probably been consumed in the explosion."

A voice boomed from a public address system in the fenced-off compound; "All military and civilian personnel must evacuate the area." Tires squealed as state troopers, deputy sheriffs and Air Force personnel raced toward Damascus to begin the evacuation.

"The explosion shook our house like an earthquake, even though we're about seven miles from the silo." said Herman Swafford, 41, of Bee Branch, as he sat on the floor of the Clinton High School gym evacuation center today. "We grabbed a few blankets and some diapers for the baby and little else and we were heading for the car when the sheriff's deputy arrived. He told us to get out as fast as we could, that there would be toxic fumes in the air."

Grace McMackin, also of Bee Branch, said, "We all figured that when we heard the explosion we knew exactly what had happened. Our neighbors in the road practically ran over us trying to get to Clinton. So we sat in our car most of the rest of the night -- and let me tell you, 11 people and two dogs in the same car isn't funny.

At the White House, President Carter said he had asked Defense Secretary Harold Brown to "give me a complete evaluation of the cause of the accident," assess the status of the other 53 Titan II missiles and "make sure there is no repetition of this accident."

The president indicated that the time was approaching for the old liquid-fueled, land-based Titans to be replaced by ones propelled by a less dangerous solid rocket fuel with a texture of an eraser.

"Through a normal evolutionary process," Carter said the Titan IIs will be replaced by a new missile. Titan IIs have been underground and on ready-to-fire status since 1963.

Pryor said today it was "unbelievable" that the Air Force has not installed an early warning system on the Titan missile sites.

The explosion started a small forest fire in the area, which was quickly extinquished. A light rain of gravel fell for a few seconds after the blast, along with large chunks of the silo door and the nuclear warhead.

By late today the roadblocks in the evacuated area had been lifted and residents were being allowed to return to their homes.

Sheriff Anglin accused the Air Force of trying to downplay a dangerous incident. "They acted as if they wanted to cover up the leak and were reluctant to let us order any type of evacuation."

Air Force Secretary Mark compared yesterday's Titan II explosion to an accident on a C47 transport, saying that it should not be used to condemn the whole vehicle. "A safe system can have an accident," said Mark.