Even after a $30 billion outlay to make the new MX blockbuster hard to hit by hauling it back and forth in tunnels or around a race tack, it still may need a revived anti-ballistic missile to protect it.

The Air Force adknowledges that possibility in recently released Senate testimony, terming the combination of the MX and ABM "a very happy marriage" for offsetting the threat of a barrage of Soviet warheads.

Rep. Les Aspin (D-Wis.), however, says that the Air Force testimony raises doubts in his mind about the wisdom of the MX project.

"It's time to seriously consider whether maintaining a huge, landbased ICBM force is really worth it at all," he said in a statement issued after reading the Senate testimony. Aspin said the prospect of having to build the ABM to protect the MX adds "a whole new dimension" to the debate.

Maj. Gen. Kelly Burke told the Senate Armed Services Committee at a closed session in April that the Soviets might decide to deploy enough warheads to bombard all the shelters to be built for the MX, which is still under development.

Under the Air Force scheme, each MX would be shuttled among 25 underground shelters so Soviet gunners would not know which one to aim at.

"The Soviets," Burke told the Senate committee, "have to attack all 25 in order to destroy" one MX missile.

"But with the Army's ballistic missile defense system in a mobile mode," Burke continued, "we could preferentially defend the occupied shelters and ignore the others."

In other words, the Air Force would make the ABM mobile along with the MX - presumably by putting some part of the warhead defense on its own wheels or tracks. The ABM would then concentrate on protecting the silo which held the MX missile without giving away the "shell game."

To be sure of breaking through the ABM shield, the Soviets would have to shoot two warheads at each of the 25 MX shelters, said Burke, who called such an effort prohibitively expensive.

Burke is director of operational requirements in the Air Force's research office. His superior, Lt. Gen. Thomas Stafford, deputy Air Force chief of staff for research, also portrayed the ABM as a potential guardian of the MX which is expected to be deployed in 1986.

Under the strategic arms limitation treaty before the Senate, the United States and Soviet Union could not arm a single missile with more than 10 warheads. However, the Pentagon has said that the Soviet SS18 missile already in the inventory has enough lift to carry 30 warheads.

Burke and Stafford see the ABM as a desirable protection if the Russians deploy more than 10 warheads on each missile after the SALT II treaty expires in 1985.

Stafford told the Senate committee that shuttling the MX from one shelter to another would be enough protection "for a period of time."

"But," he added, "if the Soviets should increase their number of boosters overtly or covertly, or number of re-entry vehicles, a ballistic missile defense could help offset that." Stafford said he did not know how much an ABM for MX would cost.

The Army spent $6 billion on the ABM from 1968 through 1975 before abandoning the idea of stopping a bullet with a bullet. Research on advanced ABM'S has continued since then.

The testimony by Burke and Stafford comes at a time when some specialists are quietly advocating a heavier investment in weapons designed to defend the nuclear offense.