In late April 1969, a fidgety, irascible Navy pilot arrived at a weapons laboratory in the California desert, aflame with a secret mission: to invent an antiradar missile that could protect U.S. warplanes from the deadly fire of North Vietnam's radar-guided missiles.

For the next two months, during every waking hour, Capt. Robert F. Doss relentlessly prodded a small band of engineers to come up with a blueprint.

On July 4, Doss and his gang offered a strategy, quickly accepted by the Navy, for building an antiradar missile. It had to be fast, it had to be ready for war by the mid-1970s and it had to be cheap enough, at about $30,000 apiece, to fling at the enemy in large numbers.

Doss' vision proved to be a pipe dream. Twelve years later, the High-Speed Anti-Radiation Missile, or HARM, still had not reached the fleet. The missile had swollen in weight and complexity. Most remarkably, the price had soared to more than $1 million a shot.

The star-crossed history of HARM has been repeated in different ways for a distressingly large chunk of the U.S. arsenal. Beset by industry's hunger for profit and the Defense Department's perpetual quest for a "silver bullet" to protect American warriors from danger, weapons consistently cost more, bog down in development and become more complex than intended through an affliction Pentagon insiders call "requirement creep."

That double helix of spiraling cost and complexity means that despite spending more than $2 trillion, which is the largest peacetime arms spree in U.S. history, the Reagan administration will manage only modest increases in the size of the armed forces.

The Defense Department, for example, has nearly doubled spending on missiles during the past four years, while increasing by only 6 percent the number of missiles purchased.

The number of aircraft purchased under President Reagan is only 9 percent more than under President Carter, and combat jet purchases have actually declined, despite a 75 percent growth in the aircraft budget, according to the Congressional Budget Office.

Some of today's planes and missiles are more lethal than those of the 1970s. But just as clearly, at some point, swapping quantity for quality becomes a losing game.

That principle was clearly illuminated when senior military leaders, waging a paper shootout called Global War Game '84, concluded that NATO would lose half its warplanes in the first 10 days of a nonnuclear war with the Soviet Union.

A fundamental question emerges: Has the defense establishment priced weapons beyond the capacity of even the United States to buy in quantities sufficient for adequate national security?

As part of an occasional series on the defense industry, The Washington Post last month examined the record profits now reaped by defense contractors, the industry's success in deferring taxes and the golden safety net spun by Congress and the Pentagon to protect arms makers from many of the usual risks of doing business. Weinberger Blunted the Cost Spiral

Today's article and two to follow will consider the federal and corporate labyrinths that the nation's weapons must traverse from brainstorm to battlefield.

The Reagan administration contends that it has reversed the historic trend of delay and overrun. Even many of his most truculent critics agree that Defense Secretary Caspar W. Weinberger has blunted the cost spiral by buying larger quantities, gauging costs more realistically and fostering competition.

But internal Pentagon documents suggest that in many ways the business-as-usual syndrome persists. One study, not publicly released, observes that the fundamental ingredients of inefficiency and cost growth remain entrenched: too many weapons programs competing for too few dollars with too little hard-nosed realism in the Defense Department.

"Little discipline to ensure affordability has been forced upon the system through the long-range planning process," the study concluded last year.

Sen. William V. Roth Jr. (R-Del.), a frequent Pentagon critic, came to a similar, albeit blunter, conclusion last month:

"If anything, acquisition problems are as serious today as ever. We are buying less but continuing to spend more."

To the redoubtable Capt. Doss and his flyboy friends, there was nothing theoretical about the need for a weapon such as HARM to knock out enemy radar in Vietnam. The matter was literally one of life and death.

"We were being eaten alive by missiles that were radar-guided," recalled Capt. Ken Dickerson, an A4 Skyhawk pilot in some of the war's first bombing raids who now commands the Naval Weapons Center at China Lake, Calif.

To fight back, the Navy first invented Shrike, a missile built to electronically sniff out enemy radar beams. Shrike was threatening enough to sometimes force the North Vietnamese to flip off their radar, allowing U.S. pilots a little breathing room. But the missile was slow and limited in the types of radar it could detect, and so Doss began his search.

Navy engineers responded with Shrike-73. It resembled Shrike, but was faster, more lethal and harder for the enemy to see. In three test firings in the summer and fall of 1974, Shrike-73 scored two bulls-eyes.

"Urgently needed," the Navy said of Shrike-73. "No major technical problems." Shrikes cost $19,000 each at the time; the Navy expected the new generation to be only modestly more expensive.

But Shrike-73 soon got its own acronym -- HARM -- its own contractor -- Texas Instruments -- and its own troubles. Big troubles. The missile began to suffer from requirement creep.

The Air Force wanted one thing, the Navy another; the Defense Department decreed that HARM should be both. U.S. intelligence analysts discovered more and more new threats, new Soviet radar frequencies, new tactics. Each time, Texas Instruments was told to jazz up its missile accordingly, delaying production and inflating the price. EXCAP Boosts HARM Price to $600,000

By 1976, the anticipated cost per missile was $48,000. A year later, the figure was $61,000. Two years later, in an attempt to keep up with ever more sophisticated Soviet radar technology, senior Defense Department officials ordered an "EXCAP," or expanded capabilities effort, for HARM. That enormously complicated what the missile was being asked to do and boosted the price to more than $600,000 apiece, according to congressional testimony.

Texas Instruments executives maintain they were simply fulfilling the customer's desires. "We always have an opinion on something," said G. Dean Clubb, the company's HARM expert. "But the government's the one that decides what goes."

Navy Secretary John F. Lehman Jr., however, said defense contractors often encourage requirement creep because the bigger and more complex the weapon, the greater the cost and profit.

"They've got their order book out," Lehman said. " 'The latest study shows you ought to have 20 miles more of range? Sure, we can give you that, piece of cake. We'll hire more engineers' . . . . When you get paid for overrunning, and get profits on top of that for overrunning, you're disserving your stockholders if you don't overrun."

By 1981, when the Navy placed its first order for 80 HARMs, each missile cost $1.3 million and was built from 10,000 design drawings. Furthermore, the entire concept had mutated.

What was to have been a shield for U.S. pilots, "inexpensive enough to be used freely in attack," had become a precious weapon suitable only for "the surgical removal of high priority, extremely sophisticated enemy air defense systems," as one Air Force general put it. It was, Lehman said, a "superb missile." It could destroy early warning radars. It could destroy weather radars. It could destroy air traffic control radars.

But it was so expensive that it wasn't much good for its primary mission: the saturation of enemy radars guiding missiles toward U.S. pilots and their planes.

"This missile is not usable, it will not achieve its effect, unless you can fire a lot of them," Lehman said. "So there we were with a silver bullet again. A classic silver bullet."

The Pentagon never has been acclaimed for prowess in spotting a bargain. President Harry S Truman once groused that "no military man knows anything at all about money; all they know how to do is to spend it."

In 1971, the General Accounting Office found that 61 weapon systems surveyed cost $33 billion more than originally planned. More than a decade later, a similar study of 172 systems found costs had climbed $387 billion, 170 percent above initial estimates.

Thus, HARM is hardly unusual. In 1979, to cite just one example, the Army was so eager for an antitank missile, the Viper, that it ordered the manufacturer "to get something that worked in the field, regardless of the cost," according to a Defense Department audit. 'Stretchout' Strategy Costly in Long Run

Not surprisingly, Viper's cost quadrupled, even as the number of missiles the Army planned to buy was halved. Viper careened out of control so drastically that before it finally was canceled the Army was paying $77 for simple slings made from 52 cents worth of cloth.

Why do cost overruns seem such a fundamental feature of the American arsenal?

One reason is that when political pressures squeeze the defense budget, as is happening today, it is commonplace to simply buy fewer weapons now, and more later. Almost invariably, the "stretchout" strategy costs more in the long run.

A Pentagon study of 61 major programs in fiscal years 1984 and 1985 found that nearly half had been stretched out. The same document also noted that in the past three years, 29 new weapon systems have been started.

"We jam up the system with so many programs, so many different systems, that we can't afford to buy them in economic quantities, and therefore we end up buying them in small quantities at very high unit cost," Comptroller General Charles A. Bowsher, who heads the GAO, complained last year.

Furthermore, when a new weapon is undertaken there is a "natural human tendency to understate costs," as Defense Comptroller John R. Quetsch put it. The conspiracy of optimism applies to military program managers, whose careers ride with the weapon, and to contractors, whose profits depend on convincing Congress that the programs are prudently affordable.

And Congress, which may be myopic about the real cost of weapons -- the Congressional Budget Office found that nearly $23 billion was excluded from the Defense Department's 1983 cost estimate reports to Capitol Hill -- often turns a blind eye if realism about weapon prices means sacrificing jobs at home.

Perhaps most important, industry often has no incentive to cut costs. The lion's share of Pentagon dollars is spent on contracts awarded without competition and many contractors are reimbursed for whatever they spend on the job.

"Everybody's missed the point of what we're buying. We're not buying products, we're buying costs," said A. Ernest Fitzgerald, Air Force deputy for management systems. "Those guys are selling us their costs. And they're in the business of cost and subsidy maximization because that's their product: costs.

"The system is so nuts that people can't believe it would be that way," Fitzgerald added. "If you wanted to dream up something that would be the absolutely worst way to run the business, this would be it. Joe Stalin couldn't have done it better."

Before the HARM missile was even a gleam in Doss' eye, Texas Instruments was offering to build the earlier generation of Shrike antiradar weapons for $19,500 apiece.

That seemed a bit pricey to the Navy, and Sperry Univac was asked to bid on the same contract. The competition had a remarkable effect: Texas Instruments suddenly found it could build the missiles for $4,480 each, a 77 percent slash in price, while Sperry bid $3,850. The Navy farmed out Shrike business to both firms and continued to play the competitors against each other for years.

When HARM roared past the $1 million mark more than a decade later, the same cure seemed in order. This time, Texas Instruments dug in its heels.

"They did everything in the world to stop it," said Burrell Hays, technical director of the Naval Weapons Center. "They lobbied hard . . . . They were clearly the only ARM [antiradiation missile] manufacturer in the country, and that's a very comfortable place to be."

Texas Instruments argued that "yes, we could take $200 million to qualify someone as a second bidder and train them in all this technology that TI has been developing for -- what, 14 years? -- or we could spend the $200 million on the missile," as company spokesman Norman P. Neureiter recalled.

That logic made sense to then-Deputy Defense Secretary Paul Thayer and then-Undersecretary Richard D. DeLauer, who jointly persuaded Weinberger to veto the Navy's competition plan. Since 1947, formal competition has been required for all Defense Department purchases. The catch is, there are 17 exceptions to the rule.

But before Weinberger's decision, the threat of competition had spurred Texas Instruments to cut its price on HARM three times in three months to less than $400,000 apiece, according to Richard L. Rumpf, deputy assistant Navy secretary for air warfare. Pentagon Still Seeks Inexpensive Missile

Even more dramatic was a Navy decision to seek a second source for the computers needed to control HARM, an initiative that shoved the price down from Texas Instruments' original $260,000 per computer to $52,000.

Texas Instruments' executives, while agreeing that the specter of a competitor caused them to sharpen their pencils, maintain that the price per missile would have dropped below $300,000 as efficiency and production techniques improved.

Today, 16 years after the North Vietnamese provoked the Navy to begin thinking about HARM, the missile finally is wending its way to U.S. aircraft carriers. Its complexity continues to cause the Pentagon some heartburn. In five of its last eight tests, HARM missed the target, according to Navy and congressional officials, and Texas Instruments is still laboring on the missile's computer software.

Almost everyone believes that once the bugs are ironed out, HARM will be a very capable weapon, albeit quite different from the Navy's original vision.

But the story has a postscript. The Defense Department is now looking at two new antiradar missiles -- the Self-Protect Weapon and the Sidearm -- intended to be smaller and less expensive than HARM.

The goal in both cases is to find a weapon cheap enough to be used freely in attack against enemy radar. And that is precisely where Capt. Robert F. Doss, who died several years ago, entered the picture in 1969.