The Air Force is financing a $6 million study on a proposed new basing mode for the MX missile that would couple the benefits of mobility and protected underground silos, Pentagon officials said yesterday.

Known as "carry hard," the new concept uses a new technology for packaging the missile, launcher and electronics in a hardened canister, which would be transported by a vehicle and rotated in and out of underground holes, officials said.

Pentagon spokesman Robert B. Sims said the concept is one of several alternatives being considered for basing the MX. The Reagan administration had planned to place 100 of the multiwarhead missiles in Minuteman silos, but Congress capped the number at 50 because of concern that the silos would be vulnerable to Soviet attack.

The small, mobile Midgetman missile designed to complicate Soviet targeting is being developed, but the high cost of deploying the single-warhead weapon has raised concerns in Congress and the Pentagon.

Sen. Pete Wilson (R-Calif.) said the "carry-hard" approach holds out the promise of a basing mode more survivable than Minuteman silos and less costly than the mobile launchers that would be used to tow Midgetman from site to site.

Wilson, a member of the Senate Armed Services Committee, said the new concept also has the attribute of deception because it would move the missile in and out of holes, complicating Soviet planning.

He said the concept, which is also known as "mobile encapsulated hardness," was made possible by a new technique for hardening the canister, or "suit," in which the missile and its launcher would be transported to different sites. Such hardening in theory would make the missile less vulnerable to exploding nuclear warheads.

Sims said the "carry-hard" research being conducted by Boeing Co. will take at least a year before the method's practicality can be assessed by a Defense Science Board panel headed by M.I.T Provost John M. Deutsch.