The Pentagon, in an extraordinary display of faith in new technology, is counting heavily on a quartet of new cruise missiles to help maintain the arms balance with Moscow -- even though none of these missiles is operational yet.

In effect, the United States is making a $10 billion bet that these low-flying missiles, which look like flying torpedoes, will only work as advertised but also quickly close a missile gap with the Soviets that officials fear could otherwise open in a few years.

The Defense Department's top officials and scientists are unanimous in their praise and confidence in these new weapons and are moving full-speed ahead on all four at roughly the same time, with little or no challenge within the defense establishment and Congress.

Yet a small group of critics warns privately that these weapons could be flying toward "a total flop" and creating a false sense of security for a portion of the future U.S. missile arsenal.

The critics argue that these missiles would have a hard time finding their targets in a real wartime situation and that the program of flight testing in this country could be tailor-made for "cooking up" the kind of results that feed a false sense of confidence.

Cruise missiles are basically small, pilotless airplanes, powered by jet engines and carrying either an atomic bomb or a large conventional non-nuclear explosive in the nose. The missile can be fired from land, sea or air at targets many hundreds of miles away, supposedly with extreme accuracy.

The key to doing this is very sophisticated electronic brain to each missile which consists of inertial guidance system to put the missile on its initial course, a second guidance system to correct its position as it flies toward the target, and a computer to give the orders.

In essence, the cruise missile is throughly "American" in the eyes of both its supporters and critics. To its supporters, it exploits areas of technology where the United States has a considerable edge to produce a dramatic advance in weaponry, while to its critics it reflects a fascination with technology that has led to too many excessively complex weapons that don't perform as advertised.

The program really began to take off early in 1977, when the Pentagon picked the General Dynamics Corp. of San Diego to begin full-scale development of the Tomahawk cruise missile for both the Navy and the Air Force. These 21-foot-long missiles are meant to carry atomic warheads to targets such as or East Europoean airfields, command centers, ammunition dumps, and missiles bases up to 1,800 miles away. The ground-launched version would be fired from U.S. bases in Europe and the sea-launched from Navy vessels.

The missiles are meant as a North Atlantic Treaty Organizatin Counter-balance to new Soviet intermediate-range SS20 missiles already deployed in Europe.

Defense officials expect the number produced eventually will reach into the thousands at a cost of $3 billion or $4 billion in the next few years.

Then in March of this year, the Air Force chose the Boeing Co. of Seattle, Wash., to begin production of more than 3,000 nuclear -tipped, air-launched cruise missiles (ALCM) in a program valued at about $4 billion.

These missiles are meant to be fired from B52 bombers -- with up to 20 on each plane -- at Soviet Targets 1,500 miles away.

The potential here, however, is much greater. William J. Perry, undersecretary of defense for research and engineering and the Pentagon's top scientist, says that the ALCM is "the quickest and cheapest thing we could do to build up our strategic force" if a new arms race ensues with Moscow and arms limitation talks break down completely.

"It is the primary candidate for a beef-up," Perry says, indicating that production could go to 5,000 simply by expanding the number of B52Gs now slated to get these missiles to also include the later "H model of the aged bomber.

By next year, he says, the production rate will be up to 500 per year.

Then, early in April the Pentagon went back to General Dynamics with a development contract for a fourth cruise missile version. This one is intended to fly only about 300 miles with conventional bombs aboard and meant to be used by both Navy and Air Force tactical jet fighters to knock out such things as airfields and shipping close to a battle field.

This contract is ultimately apt to be worth $2 billion or more if 3,000 -6,000 missiles are built, officials say.

This medium-range missile, dubbed MRASM, is the only one to have run into some trouble in Congress, where the House Armed Services Committee prefers a different approach. But the Pentagon eventually expects to prevail.

In all of the programs, the cruise missile is basically meant to replace airplanes. The idea is to launch the cruise missile well outside the range of enmy defense that might otherwise shoot down the missile-carrying airplane. Then the missile flies at speeds of 500 miles per hour hugging the earth at attitudes of 200 to 600 feet, over long distances and hopefully ducking under enemy radar beams.

Though they fly straight, their small size is supposed to make them hard to shoot down even if spotted, and because they are relatively cheap -- $1 million apiece or less when mass produced -- they can be launched in numbers large enough to overwhelm defenses.

The Pentagon clearly considers them "bargains" in comparison to the U.S. arsenal of big ocean-spanning ICBMs based in this country and on missile-firing submarines.

Perry counterssthe charge that the United States is putting too many eggs in one technological basket with the cruise missiles by pointing out that Americahs landbased ICBM force is supposed to be modernized with the new MX missile and that the new Trident missile-firing submarines will also soon begin entering the fleet.

But there is no way, Perry says, to get those bigger weapons into service fast. So he, Defense Secretary Harold Brown and President Carter came to the conclusion in 1977 that the strategic balance of power with Moscow could tip against the United States in the 1980s, and that cruise missiles were the best and quickest way to respond to the Soviet missile build-up of land and submarine-based ICBMs.

Perry is the principal driving force behind the cruise missile. Some of his friendly critics think he was a case of "cruise-missilitis."

Perry is respected within the defense establishment and he said in a recent interview he had "high confidence" in these new weapons, "certainly relative to other major programs we are working on today." He said he thought the risks were low in 1977 when they got started "and everything since then confirms that judgment."

"We are doing things that exploit the technology we have. We are combining things, not stressing any single technology or sub-system," he said.

"You might say," he continued, "that we are following the Beethoven approach to weapons systems planning. Beethoven was famous for finding a good theme and hitting it over and over again. We think this is a good theme. It's a good technology. It lends itself well to our industrial base and we are pulling out the throttle ver vigorously to exploit it to the full advantage."

He acknowledges that a lot of things are going on very fast and concurrently -- developed work, flight testing and start-up of production lines. "So we could have a lot of egg on our face but fortunatly, that's not the case."

The critics, however, think that may become the case.

It should be noted that around the Pentagon, it is hard to find anybody who admits to being even modestly concerned about the performance of these new weapons.Those few who are clearly seem to be mavericks. Yet some have long experience in weapons programs so their views appear worth airing, given the huge fiscal and security stakes involved.

The critics focus on several areas.

Historically, they say, cruise missiles are not new, having been used by the Germans in World War II in the form of crude "buzz bombs." Much more modern versions were built by the U.S. Navy and Air Force in the early 1960s in the Regulus and Matador missile programs. Neither of these missiles was very reliable, and critics believe new versions with better technology still face the burden of history.

The much more severe test, they believe, lies in the very low altitude and high-speed environment in which the cruise missile flies. These missiles take a pounding, sometimes for hours, in the turbulent air at low level. This plays havoc with gyroscopes trying to hold the missile on course and generally contributes to reliability problems with instruments, they say.

Perhaps most importantly, critics eye the crucial part of the cruise missile's guidance system. This is known as Terrain Contour Matching, or TERCOM in Pentagonese.

Stored in the computer memory of each missile is an electronic "map" of the route the missile is supposed to take to the target. These are prepared from pictures taken by space satellites or reconnaissance planes of potential enemy territory. By using a special electronic scanning device on the missile that points toward the ground, the missile's brain is supposed to compare what the ground looks like to what the map looks like. It is then supposed to find pre-selected landmarks, such as a distinct group of hills, to make sure exactly where the missile is.

With this electronic match-up telling the computer exactly where the missile is, it then sends a "fix" to the inertial guidance system, correcting any navigational errors that may have crept in during the flight so far. Depending on the length of the flight, the missile might need to fly over or near several fix points in order actually to hit the target.

Critics claim the system is too dependent on finding easily recognizable terrain features, that there are large areas in the Soviet Union that are like prairies with few sharp features, and that the electronic map-matching has too many potential technical traps.

The device used to scan the ground and make comparisons with the stored "map" is a radar altimeter, used for measuring altitude above the ground. Critics claim such instruments are not sharply focused enough to give really accurate readings, that they can be fooled by sharp crevices, high trees and seasonal changes in foliage.

The critics have little confidence in tests run on missile ranges in the western United States where the terrain is well known. They suspect that the big financial stakes and widespread involvement of industry, both military services and the Pentagon's research establishment will produce a "cruise missile cartel" unwilling to challenge test results.

Perry argues that the accuracy of the TERCOM system is "sufficient" for nuclear weapons, which devastate a large area even if they don't land on a dime. A different guidance system is used for the conventional weapons carrier, he says.

Perry also says "there has been a very substantial amount of testing under a wide variety of conditions . . . probably more testing than any other major military program."

Yet the defense official also acknowledges under questioning that "it is true we didn't get as many data points as we would like . . . and we didn't get as many flight hours as we hoped due to crashes" in the initial flight test program of the Air Force's big air-launched cruise missile project.

When the selection of Boeing was announced, the Air Force reported that six of 10 flight tests had been successful. Four of the 10 general Dynamic missiles had also failed.

At that time, Perry said "we believed we had sufficient data to confirm the validity of the design and select a contractor." He still believes that.

But as a result of "the gaps" in the flight testing, the planned follow-up series of flight tests has been almost doubled from 11 to 19, he said.

In May, the House Armed Services Committee cut out all $23 million the Pentagon had asked in its new budget for developing the MRASM medium-range tactical cruise missile, which Perry calls a weapon of "national importance."

The House said the Pentagon is not following its instructions to build a high-speed ramjet instead of a cruise missile for this role.

Perry contends the House is wrong, that flying low with a very small missile is the way to get through Soviet defenses, and says he will fight to keep the General Synamics program.

While this debate should be settled soon by a House-Senate conference committee, the question of why General Dynamics rather than Boeing won this tactical missile contract and why it was done so fast may be a longer-running issue.

One congressional aide told this reporter that "you'll never get the whole story."

The day after Boeing won the big Air Force ALCM contract, news stories appeared out of California about how 1,500 General Dynamics workers stood to lose their jobs. A few days later, the new contract to General Dynamics was announced.

Perry, however, makes the case for selecting the California company.

General Dynamics, he said, had long experience working in tactical cruise missiles, and was proposing a scaled-down version of the Tomahawk missile already in development.

Furthermore, there were two dozen test missiles still left from GD's earlier effort to win the ALCM contest, plus a pilot production line set up and a skilled team intact which otherwise would have to have been abanndoned soon.

In short, Perry said, the savings were substantial and "there was hardly a better bargain going today" where "for a relatively small investment the U.S. could get a highly effective new missile in just a few years."

Both the Navy and the Air Force are to use that new missile, which will be managed in a joint project office headed by a Navy admiral.

The contract caused some concern in the Air Force, and some troubled civilian defense officials wondered why it was done so quickly.

Some Air Force officers complained privately that having just picked the Boeing missile as better than the General Dynamics missile in the ALCM contest, why must it take the GD version of the shorter-range tactical cruise missile. It would also mean a new set of spare parts for a different missile and additional training.

Perry maintains that a month-long study and decision-making process -- which he acknowledges is "lightning speed" at the Pentagon -- involved a hard look at both missiles before deciding on General Dynamics. Others maintain a proper look would take much longer.

The Air Force, he said, "would have preferred to have kept it as an Air Force program, making variations from the ALCM, and keeping it under their own control rather than turning it over to a joint program."

"But it seemed to me to be a clear case for a joint program because both services," the Air Force and the Navy, will use it. "That's what I'm paid to do," said Perry, "to make those kinds of decisions. I had no trouble making that one."

Some other critics argue that the new General Dynamics missile isn't needed at all. They say the Navy's existing Harpoon missile can be used to attack enemy shipping at long range, though not as far away as a new cruise missile, some suggest that another missile known as Assault Breaker could do that job.

Perry acknowledges the argument over Harpoon, but believes it is worth it to extend the distance at which the fleet can be protected. He, and several other officials, maintain that Assault Breaker doesn't have enough range or payload to handle the Air Force job of busting up airfields deep behind the lines of a European battlefield.