Washington — Pentagon weapons planning may be on the edge of fundamental change, with unmanned bombers, self-steering artillery shells, and other high-tech ``smart'' weapons becoming higher development priorities. Defense Secretary Frank Carlucci and other administration officials see such a move as a cost-effective way to bolster NATO forces in Europe, which have long been outnumbered by their Soviet opponents.
But the US military, fond of buying big platforms such as warships and tanks, is not uniformly enthusiastic about a change in budget emphasis.
And a number of smart-weapons programs under way have been beset by problems. Three - a surveillance drone, a guided shell, and a powered bomb - were purged from the 1989 defense budget because of technical troubles.
``We have to be careful that we don't sink all our resources into the fantasy of silver bullets,'' says Dennis Kloske, an adviser for NATO armaments to the secretary of defense. ``But we need to conserve and identify and advance key technologies.''
In the wake of the superpower treaty banning medium-range nuclear missiles, the state of NATO tank armies and air forces has become a much-discussed topic among alliance members. Conventional weapons modernization will surely be a subject high on the agenda during President Reagan's NATO meetings in Brussels this week.
At the US Senate hearings on the INF Treaty, numerous witnesses have claimed that when nuclear Pershing 2 and cruise missiles are withdrawn, upgrading NATO weapons will become more important than ever. Adm. William Crowe, chairman of the Joint Chiefs of Staff, deemed it essential that the allies ``enhance the cutting edge of NATO's existing forces.''
But addition of tank divisions and air wings would undoubtedly cost more than the US or its allies are willing to spend. Thus the heightened interest in smart weapons and associated launchers and communications networks, which could improve the striking power of existing forces for less money.
In general, smart weapons use advanced sensors and electronics to steer toward targets. The Army, for instance, is developing a munition intended to descend by parachute, sniffing for tanks with an infrared sensor. Cruise missiles are a type of smart weapon, and advanced cruise missile guidance and propulsion units are being researched.
A recent Pentagon report by a long-term strategy commission called for more emphasis on development and purchase of smart weapons. ``The alliance's posture could be transformed by new military technologies,'' according to the report on ``discriminate deterrence.''
Besides such votes of interest, a number of factors are pushing Pentagon planners to devote more resources to advanced-technology weapons.
One is congressional pressure. A number of senators on the Armed Services Committee have banded behind a so-called NATO defense initiative, which would consolidate management and guarantee funding for a package of smart weapons and communications systems.
Another factor is the preferences of Mr. Carlucci himself. Two weeks ago at a meeting of senior Pentagon officials, he endorsed implementation of a weapons-planning approach called ``competitive strategies.''
This idea, first hatched during the Pentagon tenure of Caspar Weinberger, calls for pushing development of US technical strengths that match up against Soviet weaknesses: micro-electronics, for instance.
Competitive strategies ``provides a framework for conventional force modernization in NATO,'' says the Pentagon's Dennis Kloske.
Mr. Kloske adds that some weapons that seem less than ``smart'' - the humble mine, for instance - make sense in this modernization framework.
Carlucci has specifically endorsed a thin, secret blue-covered report on NATO competitive strategies that calls for development of:
Unmanned aircraft capable of attacking Soviet main bases.
Long-range mobile weapons, perhaps such as the ATACMS missile the Army is working on.
Surveillance networks, such as JSTARS, which are capable of tracking mobile Soviet targets deep behind the front lines.
These and other programs of competitive strategies are to be protected from budget cuts, say defense officials, and nurtured as much as possible.
Large obstacles to the rise of smart munitions and other advanced technology systems do exist.
The military services have never been quick to embrace weapons that challenge old ways of fighting. In the past, both the Navy and the Air Force have resisted adopting long-range cruise missiles into their contingency plans, one Defense Department source complains.
The Air Force, for instance, has pressed ahead instead with purchase of the F-15E, an expensive deep-strike bomber version of the basic F-15 jet.
And the performance of smart weapons does not always live up to their promise. Many now in development have faced technical struggles. The Aquila drone, after years of disastrous test flights, was finally killed in the 1989 budget, as were an upgraded Copperhead laser-guided shell and the AGM-130 rocket-powered bomb.
In addition, a $5 billion program to develop a battlefield surveillance command and control system, JSTARS, has had trouble in crucial radar systems. A joint NATO project to build a guided warhead for the Army Multiple Launch Rocket System has fallen two years behind schedule and been downgraded in performance.
Some smart weapons promise economy. Cruise missiles, for instance, are cheaper than jet fighters. But others would cost more than the weapons they replace. This is especially true for smart munitions. The Army is aiming to make the new SADARM self-steering antitank munition cost about $15,000 per rocket - far more than today's ``dumb'' shells.
Would the US be able to afford a stockpile of smart munitions large enough to make any difference in actual combat, instead of on the testing field? ``That's a critical issue,'' says Robert Costello, undersecretary of defense for acquisition.