WITH U.S. FORCES, SAUDI ARABIA, JAN. 18 -- The Patriot battery, ugly stepchild of one of Saudi Arabia's biggest air bases, shot down a Scud missile today and became everybody's darling.

"I'm sitting in my jet, getting ready to go," said Air Force F-15 fighter pilot 1st Lt. Steve Kirik. "I looked over at my port engine, and there it was. It was like a big, brilliant flare. It jumped off the ground, snaked back and forth a couple of times and then boom! It was pretty spectacular."

Kirik, a stocky 24-year-old from Moline, Ill., was one of the few people on the base who had a pretty good idea of what had happened. An inbound Iraqi surface-to-surface Scud missile had been intercepted and killed by a single rocket fired from an Army Patriot launcher.

It was the first time a Patriot anti-missile missile, the U.S. military's state-of-the-art air defense system, had been fired in anger, and the result was a spectacular fireworks display for thousands of servicemen who had donned gas masks and crouched behind bunkers in anticipation of an imminent enemy attack.

"We didn't expect it at that moment," said Patriot battalion commander Lt. Col. Leeroy Neel, 42, of Houston. "It was there, we reacted properly, and it was gone."

As Neel finished his account, a half-dozen soldiers gathered in the base chapel clapped and gave him a rousing cheer. It was much the same elsewhere. The snazzy fighter pilots who hang out here had nothing but nice things to say about the Army grunts who man the Patriot batteries: "Let's just say my respect for them rose tremendously," said Kirik. "Glad to have them here."

They are dogged, stubborn artillerymen who wear chemical warfare suits 24 hours a day and who have been on Scud alert ever since Operation Desert Storm began early Thursday. They spend their days in a dark van full of computers watching green television screens, waiting to see the telltale parabola that lets them know that an enemy ballistic missile is inbound.

"I knew right away what it was," said 1st Lt. Charles McMurtrey, the 27-year-old Montgomery, Ala., native who was the duty officer on watch when the Scud crossed the Iraqi border a little after 4 a.m. "There's no way you can confuse it."

This afternoon, McMurtrey and his bleary-eyed assistant, Sgt. Joe Oblinger, 26, of South Bend, Ind., were standing on a bleak stretch of desert on the outskirts of the base. It was a typical Patriot launch site, close to the glamor but not part of it. Pieces of paper and old plastic bags blew through shredded tires and junk that littered the sand. The launchers themselves, ugly dumpster shapes pointed toward the sky, completed the picture.

"We alerted the command post and the battalion immediately," said battery Capt. Jim Spangler, 27, of Dayton, Ohio. Besides their normal alert, the Patriot team was also listening to Armed Forces Radio, and had heard about the Scuds that had exploded in Israel moments earlier.

"Actually," Spangler said, "I don't remember when I heard about the Israel Scuds. Both things happened almost simultaneously."

When McMurtrey hit the alarm, the base public address system sounded a siren and announced: "Condition Red, Condition Red, don your gas mask!" In this war, any report of Iraqi attack raises fears of poison gas.

In the Patriot van, the machine took over, locking on the incoming Scud and tracking its progress. There is always an opportunity to override the computers manually, Spangler said, but in a normal defensive posture, the technicians let the machine do the work, including the actual launch.

This time the posture was defensive, but hardly normal: "It's a lot different when you know if you miss it could mean 100,000 people will die," Spangler said. "There's a lot of pressure."

McMurtrey and Oblinger watched the target, but they also continued broad scanning. One Scud could mean others. Outside the van, Spangler and the rest of the battery -- about 100 people in all -- put on gas masks and knelt behind sandbags.

At 4:28 a.m. the Patriot launcher fired its missile. It arched upward, swerved once, and twice, then found the target, invisible on a moonless light.

"I was standing outside my tent about three kilometers {two miles} away," said Neel. "I saw the explosion, but it didn't register immediately. Then I thought, 'my God, that's one of mine.' "

Inside the van, Oblinger was making sure of the kill, ensuring that he didn't need to fire a second missile. McMurtrey was looking for more targets. Neither man could spend the time to congratulate the other, because they both had too much work to do.

Eleven hours later, there was little difference: "We have yet to cool out," Spangler said. "We're always on edge. You're talking a matter of seconds."

Neel didn't know if the Scud warhead had been high-explosive or chemical, and he didn't particularly care. "A chemical team takes care of that. My people just find them and shoot them down."

Description: Tactical air defense system

Range: 50 miles

Length: 17 ft., 5 in.

Weight: over 2,000 lbs.

Warhead: Conventional high explosive

Speed: Higher than Mach 3

1. Technicians in a mobile "Engagement Control Station" monitor the area for incoming threats.

2. When an incoming missile or aircraft is spotted, the Patriot is launched from a mobile launcher.

3. A ground radar system and the airborne Patriot receive reflected radar signals from the enemy vehicle. The Patriot sends its data to the ground station for computer correlation.

4. After making this comparison, the ground station repeatedly transmits an adjusted flight path to the Patriot.t

5. If successful, the Patriot will intercept the enemy missile or aircraft and destroy it in the air.

Compiled by James Schwartz and Evelyn Richards -- The Washington Post