Like a well-aimed multiple-warhead missile that lands on several targets simultaneously, conservative voters and action groups scored a direct hit Tuesday on the permanent liberal Democratic defense and foreign policy establishment in the U.S. Senate.

The tide that swept Ronald Reagan into office also swept out of office Democratic Sens. Frank Church of Idaho, Birch Bayh of Indiana, George McGovern of South Dakota and John C. Culver of Iowa. Being swept out of Washington with these senators are many of the notions and attitudes about American policy that have come to be accepted around the world for the past decade.

All of these lawmakers were among the strongest supporters of the second U.S.-Soviet strategic arms limitation treaty (SALT II), which was signed by President Carter and Soviet President Leonid I. Brezhnev in June, 1979, but which has never been approved by the Senate. Perhaps more important, all were among the most well-informed backers of the highly technical SALT process, and thus were doubly valuable to this and previous adminstrations as counterweights to anti-SALT specialists such as Sen. Henry M. Jackson (D-Wash.).

In addition, all had played an active and occasionally skeptical role when it came to challenging the Pentagon on various defense spending issues.

In his preelection debate with Reagan, Carter said that "arms control is the single most important issue in this campaign."

Though the SALT agreement faced tough going in the Senate no matter who won Tuesday, Reagan's victory not only dooms the treaty in its current form but guarantees the new Republican president -- who strongly opposed Salt II -- that he will have less of a fight from liberal senators against whatever kind of new approach to arms control he comes up with.

All four of the ousted senators had been targeted for defeat by the National Conservative Political Action Committee (NCPAC), a coalition of groups opposing a wide range of causes generally supported by liberal lawmakers.

Two other senators, Alan Cranston (D-Calif.), who was also on the NCPAC hit list, and Gary Hart (D-Colo.) managed to survive election night. Both are also articulate supporters of the SALT process and are respected defense specialists.

To administration officials, however, Granston and Hart "will be like lone voices crying in the wilderness" of a Senate which will now probably take on a distinctly more hard-line attitude toward dealing with Moscow and a softer line toward reining in the Pentagon. Given the coloration of the new Senate, however, arms control officials in government suspect that even those remaining voices will tone themselves down.

The departure of Church as chairman of the Senate Foreign Relations Committee, along with defeated Republican moderate Jacob K. Javits of New York from that same committee, also is certain to change the long-standing liberal image of that panel.

Though another Republican moderate, Sen. Charles H. Percy (R-Ill.), is in line to become the new chairman, if seniority, rather than ideological, considerations apply, adminstration officials think Percy, too, could be influenced by the Senate's new mood.

Republican control of the Senate will also mean that Sen. John C. Stennis (D-Miss.) will turn over the chairmanship of the powerful Senate Armed Services Committee after 11 years, probably to ranking Republican Sen. John G. Tower of Texas.

Though Stennis has always advocated strong defenses, he has also been critical of Pentagon waste and mismanagement on occasion, and has been a loyal supporter of this and previous adminstrations on key defense policies.Tower is more outspoken on specific defense issues, the need for higher defense spending and for scrapping SALT II. Tower also comes from a state with a heavy concentration of defense contractors.

Some Capitol Hill sources, however, point out that Tower is also chairman of the Republican Policy Committee, was an active force in the campaign, and could wind up with another job in a Reagan adminstration. Similarly, a Senate now under Republican rather than Democratic control might also be a factor that could influence Jackson, the veteran Washington Democrat who is a major voice in Congress on defense affairs, if he is offered a role, as has been rumored, in the Reagan adminstration.

If Tower and Jackson remain on Capitol Hill, then these two generally hard-line senators on defense issues, in combination with others such as Sam Nunn (D-Ga.) and a host of other new and old conservative lawmakers, are going to be the predominant voices heard, with fewer nay-sayers, in Congress on these issues under its new lineup.

At the same time, some veteran nonpolitical professional staff members on key congressional committees offer words of caution.

The same conservatism that may suggest easier acceptance of higher defense spending proposals, they say, is apt to be tempered later by fiscal conservatism when it becomes clear that there isn't enough money for all the new military projects.

"In the end," one aide says, "the same money dilemma that's been around for a long time will be back."

If Reagan means what he said in his victory statements about the need for a bipartisan foreign and defense policy, then these experienced aides believe there will also have to be some effort for arms control included in those policies.