President Reagan's Strategic Defense Initiative (SDI) survived a series of attacks on the Senate floor last night as lawmakers rejected five amendments designed to slow or reorient the missile defense effort.

The closest vote was 57 to 38 in defeating an attempt by Sens. Dale Bumpers (D-Ark.) and William Proxmire (D-Wis.) to slash the Reagan's original $3.7 billion request to $1.9 billion and establish an independent panel to evaluate the program.

The Senate rejected, 78 to 21, an amendment by Sen. John F. Kerry (D-Mass.) to freeze spending on the "Star Wars" plan at its current funding level of $1.4 billion and forbid experiments that threaten to undercut what Kerry called "the single-most important arms-control treaty of our time."

He was referring to the ABM treaty signed by the United States and Soviet Union in 1972.

Albert Gore Jr. (D-Tenn.) proposed $2.5 billion in funds for the program, slightly less than the $2.95 billion recommended by the Senate Armed Services Committee, and sought to withhold money for space experiments that might violate the ABM treaty. His plan was defeated, 59 to 36.

A proposal by John Glenn (D-Ohio) to trim the SDI to a $2.8 billion program but make no other changes was defeated, 59 to 36; a plan by Malcolm Wallop (R-Wyo.) to earmark $800 million of SDI funding for missile-defense systems that could be deployed within five years was rejected 62 to 33, and Carl Levin (D-Mich.) lost 48 to 38 when he proposed to create a 10-member panel that would oversee the program and report back to Congress.

The amendments were the first of a number related to the SDI and being considered as the Senate worked into the early morning on the record $302 billion defense authorization bill for fiscal 1986.

The amount would limit defense spending to projected increases in the inflation rate rather than the 5.9 percent growth originally sought by Reagan.

After the three SDI votes, Senate Majority Leader Robert J. Dole (R-Kan.) won agreement to delay votes on resolutions to advise the president to agree to continue respecting the unratified SALT II treaty.

Reagan is expected to announce his decision on SALT II Monday, and the votes regarding missile limits in the treaty would be held next week when the Senate plans to resume debate on the authorization bill.

The week-long delay was prompted by leadership's concern that the SALT II amendments might spark a filibuster by those opposed to continuing to comply with the treaty.

In arguing for his amendment, Kerry said planned SDI space experiments would make "a mockery" of U.S. compliance with the ABM treaty.

"You cannot have SDI and arms control at the same time," he said.

Rather than encouraging the Soviet Union to reduce its land-based missile force, which Reagan has declared is the SDI's objective, the initiative would impel the Soviets to build more offensive weapons to penetrate any new such defense system, Kerry said.

The Soviets are bound to see the Defense Department plan to test whether a satellite could stop a missile immediately after launch as a U.S. violation of the ABM treaty, Kerry said.

The administration has said equipment to be used in the test will not be the prototype of an operational system and thus will not violate the treaty.

"It will look like a space-based ABM sensor, which violates the treaty," Kerry said. He added that other scheduled experiments also threaten to undercut the missile pact.

Opposing Kerry's plan, Sen. J. James Exon (D-Neb.) said, "The only reason that the Soviets are at the arms negotiating table is SDI."

Sen. John W. Warner (R-Va.), expanding on that theme, said freezing SDI funding at the fiscal 1985 level of $1.4 billion would "jerk the chairs from beneath our negotiators" at arms-control talks in Geneva.

He said he supports the ABM treaty and disagrees with Kerry that the proposed SDI tests would violate it.

Earlier, the Senate approved on a 49-to-49 tie vote a proposal to change the Davis-Bacon Act and permit more military construction without paying an area's prevailing wage rates, usually those paid to unionized workers.

Sen. Edward M. Kennedy (D-Mass.) opposed the change championed by Phil Gramm (R-Tex.) and added to the procurement bill by the Senate Armed Services Committee.

Kennedy said the defense authorization bill is not the vehicle in which to revamp the 1931 Davis-Bacon Act, particularly without hearings or a request for change by the administration.

He also said allowing contractors to pay less than the prevailing wage in building hospitals and homes for service personnel would result in imposition of shoddy work on military families.

Gramm countered that his proposal would save $150 million a year by giving small businesses a chance to obtain such contracts.

His change would exempt contractors from paying prevailing wages on projects costing less than $1 million, rather than the $2,000 base now in effect.

Gramm said the Defense Department made the $150 million estimate, and Kennedy called the number "just plain wrong."

The Congressional Budget Office, Kennedy said, estimated such savings by fiscal 1987 at $47 million.

Gramm said the amendment, which organized labor has opposed for years, faces an uphill fight in the House.

He said it prevailed in the Senate because of a new demand for more efficiency in government spending.