Soviet missiles are becoming so accurate that the United States and other NATO countries may have to develop a different type of plane for deployment in Europe's forward bases, the Pentagon's research director says.

Richard D. DeLauer, sounding that warning in an interview recently, said he was pressing for more NATO emphasis on planes that could take off and land on small patches of ground or country roads to escape missile attacks on front-line airfields.

As matters stand, DeLauer said, the risk is high that steadily improving Soviet missiles could catch NATO fighter planes on the ground or, failing that, destroy runways so that planes that did get in the air would no longer have forward bases from which to reach Warsaw Pact countries or rise to shoot down enemy aircraft.

The Soviet theater missiles DeLauer and other Pentagon specialists are worried about as they look at NATO's aircraft near the alliance's European front line are the SS21, with a range of about 72 miles, the SS22, with a range of 540 miles, and the SS23, with range of 300 miles. Pentagon officials said the Soviets are developing conventional, nuclear and poison gas warheads for these three missiles while improving their accuracy to a worrisome degree.

The Soviets, like the Americans, are achieving accuracy for their missiles by programming them to follow maps stored in their mechanical brains. One type of missile feels its way along by bouncing radio beams off mountains, valleys and other geographical features plotted on the map. DeLauer said aircraft that could jump from one place to another in a hurry could foil such pre-programmed guidance systems.

He said he considers a new engine one of the big keys to developing survivable and versatile warplanes that could take off and land vertically or in short spaces. Pentagon specialists are discussing with West German counterparts joint development of an engine for V/STOL (vertical and short takeoff or landing) aircraft.

The desired characteristic of a V/STOL engine is a lot of power for its weight, called thrust-to-weight ratio. Otherwise the airplane cannot carry enough fuel and weapons to offset the high cost of V/STOL capabilities. The Marine Corps is the only service buying a fixed-wing plane that can take off and land vertically, the AV8B Harrier, a British design.

Pentagon critics of the AV8B contend that it costs too much for what it can deliver in combat-effectiveness. The Pentagon's weapons book puts the price of the AV8B at $36 million, compared with $19 million for the Air Force's F16 fighter on the line in several European countries. Marine leaders consider the AV8B's ability to provide close support for troops and all-around versatility make it worth the high price.

U.S. aerospace executives long have said that advances in V/STOL depend largely on how much money the Pentagon is willing to provide. Although DeLauer said he feels a sense of urgency about developing more survivable aircraft for the European front, there are many competing demands on the U.S. and NATO defense budgets. This is one reason DeLauer says he is hopeful of pooling U.S. and German resources for V/STOL engine development.

While pushing for more survivable planes for forward deployment in Europe, the Pentagon is taking a fresh look at ways to give more protection to the aircraft now deployed there. Building more and better aircraft shelters is under consideration.

Besides threatening NATO aircraft, highly accurate Soviet theater missiles like the SS21, SS22 and SS23 for conventional war could be fired at the giant storehouses of weaponry the United States has in Europe for its Army divisions.

Sen. Ted Stevens (R-Alaska), chairman of the Senate Appropriations subcommittee on defense, already has questioned the wisdom of offering the Soviets any more of these juicy targets.