The Pentagon's research director yesterday gave further impetus to the idea of substituting a small mobile missile for the big MX by saying that such a switch would be feasible "from a technical standpoint."

Richard D. DeLauer, in testimony before the House Armed Services subcommittee on research and development, did not formally endorse turning away from the MX and deploying the smaller missile, but his remarks could encourage those who want to do so.

President Reagan's MX commission, headed by Brent Scowcroft, is studying the small missile as an alternative to the beleaguered MX, but has not made a recommendation.

DeLauer said one question about a smaller missile is whether it could survive a Soviet first strike, and another is whether it could achieve the same accuracy as missiles fired from silos or other stationary shelters.

DeLauer said technical advances over the last five years suggest that such accuracy could be achieved. He warned, however, that a new mobile missile could not be deployed until the 1990s. Reagan has called for deploying the first MX missiles in 1986.

Reagan as a candidate in 1980 ridiculed President Carter's scheme for deploying the MX, but Reagan's ideas for deployment have run into the same kind of ridicule in Congress. The question is how to deploy a new generation of land-based missiles in a way that will not leave them vulnerable to attack, as present missiles supposedly are.

Congress last year denied Reagan money to put the MX into production until the deployment issue can be resolved. That led to appointment of the MX commission.

The idea of running a small ocean-spanning missile around the countryside to make it hard for the Soviets to find and hit has been studied for at least 25 years.

In the 1960s, one objection was that the best place to deploy such a U.S. missile would be in the open spaces of the West. But the weather there is usually cloudless, it was argued, and thus would make it easy for Soviet satellites peering down from space to keep track of the mobile missile.

In contrast, the Soviets have thousands of square miles of remote lands, frequently clouded over, where their missiles could be hidden, posing problems for U.S. surveillance by satellite.

William Perry, DeLauer's immediate predecessor as Pentagon research director, told The Washington Post in an interview that when he proposed to U.S. military leaders that they build a smaller missile than the MX they protested that it would not look as big and menacing as Soviet ICBMs now deployed.

"They told me it would look like a peanut," Perry said. The Pentagon under Carter stuck with the MX.