In a garrulous sea of palm-pumping, flesh-pressing politicians, the State of the Union heroes of 1986 were conspicuous by their very stillness. Four young people, sitting high above the House floor, somber faces, hands folded politely, nervously licking their lips as they waited for the president to arrive, trying and failing to ignore the hundreds of heads turned their way. As in years past, their identities were kept secret. Such a secret that until the moment of introduction, many in the audience at the Capitol last night assumed they were the children of Challenger astronauts.

They weren't, but all the same they supplied the kind of drama that has made the annual Reagan hero unveiling, love it or leave it, a staple of the political new year.

It was the honorees' second trip. The first was last week, after they were lured by cryptic phone calls from the White House, something about the president wanting to meet them. They'd trooped with their parents into the White House just in time to see the shuttle explode on cable television. After an hour or so the president came out to meet them and explained that there would be a week's delay. "He was really sad," said 13-year-old honoree Trevor Ferrell last night after the speech was over. "He was almost in tears."

* This time the speech was delivered as planned. "You are the heroes of our hearts," President Reagan said at the end of his address. "We look at you and know it is true: In this land of dreams fulfilled where greater dreams may be imagined, nothing is impossible, no victory is beyond our reach; no glory will ever be too great."

They were: Richard Cavoli, a 21-year-old science student at Union College, N.Y., whose crystal experiment to help reduce the harmful effects of X-rays on patients was aboard the doomed Challenger;

Tyrone Ford, of Washington, D.C., a 12-year-old mite in a tan suit and dark tie, a choir director at three churches who has performed at the Kennedy Center and Wolf Trap;

Shelby Butler, a shy 13-year-old from St. Joseph, Mo., who last year, as a crossing guard, pulled a small child out of the path of a runaway bus;

And Trevor Ferrell, 13, of the affluent suburb of Gladwyne, Pa., who founded a shelter for the homeless in Philadelphia. During the 1983 Christmas season, after seeing a television news item about the city's homeless, Trevor insisted that his parents take him to visit the needy on city streets. He spotted a man huddled on a subway grate and got out of the car to offer the man a blanket and pillow he'd brought from his own room. He went on to launch "Trevor's Campaign for the Homeless" with 250 volunteers who help cook and deliver hot meals to about 200 people a night.

Ferrell was perhaps the most calm of the honorees. He has met the president several times, has published a book about his work in Philadelphia, sold the film rights to director Steven Spielberg, visited Mother Teresa in ld,10 Calcutta and received a Young American Medal for Service from Attorney General Edwin Meese. Ferrell said he was the backup hero last year when the White House was worried that Clara Hale, founder of a New York City home for the children of drug addicts, would be unable to come to Washington because of poor health.

* He spoke to the president only briefly last week. "He said he likes what I'm doing," a weary Ferrell said after the speech as he sat with his father and a scheduler from "Good Morning America" in the lobby of the J.W. Marriott Hotel. "That's about all I can remember."

President Reagan first ornamented his State of the Union speeches with "heroes" in 1982, when he surprised almost everyone by interrupting his remarks to introduce two men, former POW and now Sen. Jeremiah Denton and Lenny Skutnik, the man who rescued survivors of the Air Florida crash. There were no honorees in 1983, but in 1984, the White House singled out the Rev. Bruce Ritter, who works with runaway and displaced children, and Sgt. Stephen Trujillo, a participant in the U.S. invasion of Grenada. Last year, it was Jean Nguyen, a Vietnamese refugee who graduated from West Point the previous May, and Clara Hale.

Until the shuttle disaster last week, the betting had been that this year the White House would would tap Ulrike Derickson, the airline employe credited with saving the lives of passengers after the hijacking of a TWA jet in Athens last summer. Marilyn Klinghoffer, wife of the American murdered aboard the hijacked cruise ship Achille Lauro, was thought to be another likely choice.

It even was reported that some White House aides were pushing for the presence of controversial Angolan rebel leader Jonas Savimbi.

It was difficult to picture Savimbi in the middle of last night's lineup. After the speech the four honorees were kissed by Nancy Reagan and then whisked to the White House and presented with glass jellybean jars inscribed with the presidential seal. Three then returned to their hotels. Tyrone Ford went home to his grandmother.

"I don't know, it didn't seem like it was real," said a slightly dazed 13-year-old Shelby Butler once she was safely back in her hotel room with her parents and two little sisters.

The American Automobile Association gave Butler an award for heroism in Detroit last May. Former president Gerald Ford was there to present the medal. "This topped that," said Shelby's mother, Sherry. "This was the top of the line."

Shelby Butler didn't tell anyone but her grandparents why she was going to Washington. She looked a little tired after it was over, and she wasn't exactly sure what her act of instinctive heroism -- pulling another child out of the path of a bus whose brakes had failed -- would mean to anyone else. "It happened so fast, I didn't really think about it," she said. "I guess it might set an example."

Tyrone Ford knew why he'd been chosen. "President Reagan saw me in Washingtonian magazine," he said, referring to a small feature that dubbed him "the wonder Boy of Gospel Music."

Ford was orphaned as a small child, lives with his grandmother in Northwest Washington and sings at the Fellowship Baptist Church. "I don't feel much different," he said politely as he was surrounded by reporters in the Capitol hallway once the speech was over. "But it was nice."