TO COMPREHEND THE debate over new defenses against nuclear missiles that President Reagan inaugurated with his "Star Wars" speech on March 23, you must know something about Dr. Edward Teller, the father of America's hydrogen bomb, and also about the new "survivalist" school of nuclear thinkers.

Teller and the survivalists would like to break the cosmic contract that has governed -- however uneasily -- Soviet-American relations in the thermonuclear era. They put more faith in technology than in arms-control agreements. They now believe that emerging new technologies offer a better prospect than diplomacy for protecting the United States from the potential horrors of nuclear war.

Only Ronald Reagan could tell us if Edward Teller was the key influence on his decision to challenge American scientists to invent new defenses that would make nuclear weapons "obsolete," and so far the president isn't saying. But there is no doubt that Teller's views have been important, and his fellow physicists speak with increasing certainty about the private advice they believe Teller has been giving to Reagan about a new generation of super weapons potentially as significant as the H-bomb.

The Hungarian-born Teller, who served as a model for Stanley Kubrick's caricature of "Dr. Strangelove," has always been a loner within the fraternity of nuclear phsyicists who worked on the atom and hydrogen bombs. Over the years he has upheld hawkish positions, arguing in the '50s against a test- ban treaty because fallout really wasn't so dangerous, arguing in the '60s in favor of antiballistic missiles (ABM's) and in the '70s against the treaty banning large-scale ABM systems.

Teller and Reagan go way back -- to 1967, precisely, when the newly-elected Gov. Reagan became the first governor of the state ever to visit the Lawrence Livermore National Laboratory in California where Teller has done much of his work. "He listened carefully," Teller said of Reagan in a recent interview, "and he asked a number of highly intelligent questions which showed he can clearly comprehend the technology," Teller added.

That was the beginning of a relationship that has continued since, and which Teller acknowledged was "one component that led to" President Reagan's recent initiative. "That I have seen the president is on the record," Teller said. "That I argued for defensive weapons is a fact. . . . There are several excellent (technological) possibilities and we are making good progress and I am optimistic. . . . What we have now is incomparably better than what we had in the '60s."

Teller, who is now 75, is also optimistic about President Reagan. He told a conference of physicists in Italy last year that Reagan's presidency was a "miracle" sent to save the West. Last week he publicly praised Reagan's "courage" for pursuing the idea of missile defenses.

"Star Wars" has stuck as a description of Reagan's speech because the technology behind it really does sound like science fiction. Take for example the X-ray laser, which is being developed at Livermore under Teller's titular supervision.

Sources in the scientific community speak only generally about the highly classified X-ray project. Its existence was first officially revealed by George A. Keyworth II, President Reagan's science adviser (and a proteg,e of Teller's, who recommended him for the job) in a speech last Jan. 14 congratulating Livermore scientists on their work. That speech forced the Department of Energy to retroactively declassify Keyworth's public description of the device as "nuclear explosive pumped X-ray lasers."

The idea is to "columnate," or direct the X-ray energy released in a nuclear explosion to create a devastating new weapon. A bomb mounted on a satellite equipped with X-ray tubes could become a space-based battle station. When the bomb is detonated, deadly beams would be created which -- when focused and properly aimed -- could destroy Soviet missiles as they rose up through the atmosphere, shattering rockets and warheads almost instantly. (If implemented, this idea would also destroy the 1965 treaty banning nuclear weapons from space.)

A group of young scientists headed by Dr. George Chapline and Dr. Lowell Wood of the "O Group" at Livermore have reportedly made significant advances in this technology in the last three years. The underlying physics of the idea was demonstrated in a 1980 underground nuclear explosion at the Nevada test site code-named "Dauphin."

Though the physics were demonstrated, the weapon technology was not. Pointing such a laser beam successfully at incoming Soviet missiles would be like shooting from New York and hitting a Piper Cub traveling at 6000 miles an hour above Los Angeles. It takes a steady technological hand to hold the angle of the laser gunsight to within one in one million parts of a degree.

But this is what will be needed to make the new, high-technology defensive systems work. Much of the scientific community is skeptical that X-ray lasers or any other laser weapon, space-based or ground-based, is technically feasible in this century. And if it were feasible, the skeptics doubt it would be worth the risk of provoking the Soviet Union into: a new arms race in space; a preemptive strike against the superweapon or the country trying to deploy it; or the pursuit of countermeasures that might turn any U.S. superweapon into a "hangar queen" that could never get off the ground. Deterrence -- the system of mutual fear -- is safer than these risks, the skeptics argue.

But Dr. Teller strongly disagrees. "I don't want to hurt the Soviets," he said. "I only want to defend ourselves. I think at this moment, I'm a slighly unhawkish hawk."

And why, after nearlyy40 years of nuclear peace and apparently stable mutual deterrence, why now is Teller pushing for exotic new defensive weapons?

"I will tell you," he replied, 'but the answer will not satisfy you, nor does it satisfy me, but it is the best answer I can give you: the time has come."

The scientific progress Teller says he has seen in the sealed labs of Livermore, and the intelligence reports on Soviet development of antimissile capabilities, are things the American public cannot see. We are left to guess, to trust or mistrust what our leaders and scientists say, and to wonder about the strategic thinking and technologies that have brought us to this particular crossroads in the history of annihilative weapons. The Politics

In part, the background to President Reagan's speech 10 days ago is a classic Washington story, the story of a group of hardline military thinkers, survivalists if you will, who began a political crusade in the mid 1970s to change American nuclear doctrine, and who ultimately found a voice in Ronald Reagan.

Members of the group led the fight in the Senate against the SALT II Treaty and promoted a series of sweeping changes in defense thinking all premised on an extremely hostile view of Soviet intentions.

The survivalists want the United States government to acknowledge and plan for the fact that, if attacked, it might have to wage nuclear war, and nuclear war might not be as simple or final as a massive Soviet first strike followed by massive U.S. retaliation. The survivalists believe we should be planning for life during and after Armegeddon because the Soviets are.

They pointed to the Soviet development of a vast arsenal of counterforce missiles that could -- they argued -- destroy American ICBMs in their silos with a first strike. They pointed to Soviet passive defenses like underground bunkers for Soviet leaders, civil defense bomb shelters for millions of workers and evacuation plans for cities. And they pointed to the Soviets' active defenses like antiballistic missile research into laser and particle beam weapons as well as more conventional defensive weapons.

The survivalists believed it was essential for the United States to prepare to prevail in a nuclear conflict. This meant "hardening" worldwide command, control and communications networks to survive a nuclear exchange and protecting American land-based ICBMs from a first strike threat. It also meant anti-missile weapons.

The most vigorous survivalists believe that the existence of nuclear weapons logically requires that we study how to use them as military and political tools rather than viewing them only as weapons of total destruction.

As they argued their case the survivalists picked up other allies who -- if refusing to accept the most ominous implications of survivalist thinking -- agreed that improvements should be made in U.S. strategic forces to strengthen the U.S. deterrent. By the late '70s hardliners clearly held sway in the Senate, and the events of Jimmy Carter's last year in power, particularly the Soviet invasion of Afghanistan and the taking of American hostages in Iran, only strengthened their hand.

An essential ingredient of the survivalists' ethos is the rejection of the doctrine of mutual assured destruction -- the presumption that offensive nuclear arsenals capable of inflicting mass destruction even after an opponent strikes first deter either side from attacking the other.

The desire to change this doctrine reflected a fundemental human tension about the way we deal with our adversarial superpower. We struggle with two choices on how to live with the Soviets: in coiled and well-armed isolation, or by reaching out for the uncomfortable embrace of cooperation and negotiation.

The survivalists have been marketing their new strategic doctrine as morally superior to the balance of terror that holds the civilian populations of the East and West hostage to the nuclear threat. And they are well represented in the Reagan administration. Survivalists dominate the National Security Council and the Pentagon hierarchy.

An energetic cadre of congressional staff members has assisted them. Some of these right-wing Republican staffers were part of the so-called Madison Group, who caucused at the Madison Hotel to map weekly anti- SALT II strategy and orchestrate leaks to favored newsmen. (They now meet at the Metropolitan Club.)

Two active Madison Group members in the push for defensive weapons have been Angelo M. Codevilla, who is Sen. Malcolm Wallop's (R-Wyo.) aide on the intelligence committee and, to a lesser extent, Sven Kraemer, a former intelligence committee staffer now in charge of the defense planning staff at the National Security Council.

The survivalists have succeeded on many fronts. Already in the Carter administration, official doctrine was changed to put new declaratory emphasis on nuclear war fighting. The view that command and control systems need to be "hardened" and land-based missiles protected from attack is now broadly accepted.

But until 10 days ago, the survivalists had not been able to win a strong presidential commitment to defending the United States from a nuclear attack. Without the defensive component, without making plans to protect the West from Soviet missiles, it was hard to argue that the entire package of new ideas made a lot of sense.

The survivalists knew this, so they have been pushing for antiballistic missile defense. They have been urging that the United States think of nuclear war not as the end, but as a transition period through which the United States must be prepared to pass -- not as an aggressor, but as a defender and a survivor.

An early spokesman for the survivalists was retired Air Force Maj. Gen. George J. Keegan. His evangelical energy and innovative research helped push the CIA to more alarming assessments of Soviet strategic strengths in the mid-'70s. In a March 1977 speech, Keegan warned that the Russians would deploy an "electron gun" particle beam weapon by 1980. (When it did not appear, he revised his estimate to 1983. At this writing, there is still no sign of it.)

That same year, Aviation Week & Space Technology magazine revealed that Air Force intelligence had concluded that the Soviets were working on a charged particle beam weapon at a sprawling complex in south central Soviet Asia near Semipalatinsk.

While Keegan concentrated on particle beams, Wallop emphasized laser technology. With the slogan "assured protection is better than assured destruction," the Wyoming Republican began promoting the development of laser battle stations in space with a 1979 article in Strategic Review: "It is high time that we lay the phantom of MAD (mutual assured destruction) to rest and that we turn our attention to the realistic task of affording maximal protection for our society in the event of conflict."

The technology was available, he preached, at a cost of just a few tens of billions. "Any nation which deployed two dozen . . . first generation chemical laser stations would command the portals of space against the rockets of any other nation," said Wallop. (His plan would flatly violate the 1972 ABM treaty, but Wallop didn't care.)

From the beginning, members of the space laser movement were on the edges of the defense establishment, whose planners and engineers had tracked the emerging technologies for years. They resisted the gee-whiz approach that called for the Pentagon to drop everything and concentrate on space lasers.

One Pentagon official who worked diligently during the last years of the Carter administration to control spending on laser technology was William J. Perry, then undersecretary of defense for research and engineering. Perry thought, as did his boss, Defense Secretary Harold Brown, that the new technologies showed promise, but he wanted to proceed cautiously until the scientists could overcome the technical obstacles.

Meanwhile, a copy of Wallop's 1979 article found its way to presidential candidate Ronald Reagan via his military affairs adviser, William Van Cleave, who later headed the Defense Department transition team.

As Wallop made rounds on the public circuit, his aide, Codevilla, worked in private to build a lobbying force in congress and the aerospace industry for a space-based laser battle station. By the end of November 1979, he had pulled together a group of private industry experts to brief selected members of the Senate Intelligence and Armed Services committees on the capabilities of space-based laser systems.

The outside experts were dubbed "The Gang of Four" by defense planners who saw space laser weapons as a dangerous misapplication of resources. One member of the Gang of Four, Maxwell Hunter of Lockheed's missile and space division, was eventually instructed by his company to take a much lower profile lest he irritate Lockheed's best customer.

But to Wallop and the other enthusiasts, the $100 million a year that was devoted to space lasers in the Pentagon budget was not enough. In the spring of 1981, Wallop asked the Senate to appropriate an additional $250 million for space lasers, and later settled for an extra $50 million in redirected funds from other Pentagon programs.

The list of sponsors for the amendment, with few exceptions, closely followed the roster of the Senate's right wing: Jesse Helms (R-N.C.), John East (R-N.C.), Steve Symms (R-Idaho), Orrin G. Hatch (R-Utah), Paul Laxalt (R-Nev.), Barry Goldwater (R.-Ariz.), John Warner (R-Va.), John Tower (R-Tex.), William Armstrong (R-Col.), Robert Dole (R- Kan.), S.I. Hayakawa (R-Calif.) and a lone Democrat, Daniel Inouye of Hawaii.

Thus the strongest political support for the new vision of strategic defense came largely from Capitol Hill, from a political movement whose members by and large were not technically trained, and whose arguments were disputed by defense planners responsible for weapons development, and by the mainstream scientific establishment in the Pentagon and private industry. The Diplomacy

In 1972 the United States and the Soviet Union codified into international law what appeared to be a clear statement of their realization that it was fruitless to seek assured protection against each other's nuclear weapons. They did this in a treaty that prevents them from developing large-scale anti- ballistic missile systems.

"Each party undertakes not to deploy ABM systems for a defense of the territory of its country. . . ." says Article One of the treaty, signed by President Nixon and Leonid I. Brezhnev in 1972.

Article Two states: "For the purpose of this treaty an ABM system is a system to counter strategic ballistic missiles or their elements in flight trajectory, currently consisting of: ABM interceptor missiles . . . launchers . . . radars . . ."

Article Five states: "Each party undertakes not to develop, test, or deploy ABM systems or components which are sea-based, air- based, space-based or mobile land-based."

This would appear to rule out all new ABM's. But the hardline proponents of developing new antimissile weapons point out a sentence in the appendix to the ABM treaty which, they say, provides legal justification to proceed apace with laser weapon development.

The sentence is one of the "agreed statements" on how the treaty is to be interpreted, and was inserted at the insistence of the Soviets, according to SALT I negotiator Gerard C. Smith. It says:

". . . The parties agree that in the event ABM systems based on other physical principles and including components capable of substituting for ABM interceptor missiles . . . launchers or . . . radars are created in the future, specific limitations on such systems and their components would be subject to discussion . . ."

Through this loophole, the advocates of exotic space defense technologies argue, they can send a fleet of antimissile killer satellites that would deny the Soviet Union's first strike capability.

"I do not think that's a loophole," Smith said last week. "You ought to look at Article One where the parties agree not to deploy ABM systems . . . That is the heart of the treaty.

"It was agreed," Smith continued, "that, yes, you could do research and development on so-called exotic systems, that's what we called them in the '70s, but we recognized that space-based systems were especially dangerous because that is moving toward a nationwide defense system, and, therefore, we put them under more specific constraints in Article Five so you can't move to development. For (a fixed) land-based (system), however, you could move to development."

As for the language in the anse plangreed statement relating to "other physical principles," Smith said, "The only fair interpretation . . . is that any exotic system is banned. If it is developed and if it is not space-based, then before it is deployed both sides would have to agree that was permitted and that would be an amendment to the treaty."

In his speech, the president stated his intention to go forward with antimissile defense work "keeping in mind our obligations under the ABM treaty," but he didn't explain how this could be done.

Said SALT negotiator Smith: "To my mind that's nonsense. Imagine what sort of limitation would be left. Both parties would deploy not only nationwide but worldwide systems, and that means ABM is out the window.

"That sort of amendment is equivalent to termination," he said.

To Jeremy Stone, president of the American Federation of Scientists, President Reagan's speech was an attack on the arms control community that worked toward an ABM treaty from the early 1960s to 1972. "The most mischievous and pernicious thing the president has done," Stone said, was to create a "mirage" of defensive security, where none can exist, and thereby reduce the chances for arms control agreements on offensive weapons. "We spent ten years educating both countries on this and those of us who did are pretty sore," Stone said.

The diplomatic impact of Reagan's speech has been to enrage the Soviets and unsettle American allies who see themselves "decoupled" from American interests under Reagan's vision. Space lasers and similiar systems would be directed primarily at long range Soviet ICBMSs, and would not likely be as effective in defending Europe against the 15- minute flight of nuclear tipped SS-20s or low flying Soviet cruise missiles and bombers.

In language that was dismissed as "standard disinformation," by U.S. officials, Soviet leader Yuri V. Andropov said the two superpowers had already "recognized the fact . . . that it is only mutual restraint in the field of ABM defenses that will allow progress in limiting and reducing strategic systems."

Then Andropov said what many American military thinkers believe: "The Soviet Union will never allow them to succeed" in deploying a new defensive system that would render Soviet forces impotent. The Technology

In the next 10 years, according to space laser enthusiasts, the United States could deploy a network of 24 or more orbiting laser battle stations capable, they say, of shooting down 1,000 Soviet ICBMs in the first 250 seconds of a Russian attack. The price tag for the first battle station would be $5 billion and for each additional copy, $1 billion.

Though the Pentagon weapons bureaucracy remains skeptical, it is spending $126 million in the current fiscal year on development of laser systems that could be land or space-based.

After Reagan's speech, science adviser Keyworth said laser weaponry, including the X-ray laser and chemical lasers, appear to be the most mature of the exotic technologies that could yield new antimissile weapons in 20 years or more.

Laser technology dates to 1960, but the theory behind it was first explained by quantum physicists, Albert Einstein among them, in the early part of this century.

The word "laser" started out as an acronym for Light Amplification by the Stimulated Emission of Radiation. This is a complicated way of saying that heat, pressure or other energy applied to atoms and then released causes the orbits of subatomic particles to expand, contract or vibrate back and forth. In so doing, the atom gives off energy emissions in the form of light waves.

If this process is performed in the presence of parallel mirrors trapping the light waves and intensifying them by bouncing them back and forth, a powerful beam of continuous wave energy is formed and can be channeled through a chain of mirrors to a firing point.

The chemical laser uses a violent chemical reaction, typically hydrogen and flourine, to energize molecules until they escape the laser chamber through plan nozzles and give up their energy -- thus giving off light waves -- as they pass by facing mirrors.

As congressional laser consultant Thomas Karas pointed out in his recent book, "The New High Ground,": "There are three major lines of research that have to be successful if the Pentagon is to get a useable weapon. First is the laser generating device . . . Second is the mirror for focusing the laser beam on a distant target . . . Third is a system for finding, tracking and aiming the beam at the targets."

The Pentagon has contracted, through its Defense Advanced Research Projects Agency (DARPA), for the development of all three chemical laser system components. TRW Inc. is at work on a five-megawatt Alpha laser generator, Lockheed and Eastman Kodak are at work on a large optical focusing mirror and Lockheed is also perfecting the "Talon Gold" pointing and tracking system.

The technological problems are great. The violent chemical reaction in the Alpha laser sets up a field of heat and vibration that will prevent the laser mirror from holding steady on its target 3,000 miles away. Lockheed scientists, recently monitoring a method to steady the mirror, recorded what appeared to be violent mini-vibrations on their instruments. They were surprised to find that the vibrations were caused by a mosquito walking on the mirror.

Pentagon scientists also will have to build large and perfect mirrors able to withstand a temperature environment that ranges from absolute zero to intense heat. "We've got mirrors two to three feet across and we can't get them to stop breaking on the shelf," said Col..Robert Bowman of the Space Institute.

The infared sensor and laser pointing technology for spotting and firing upon targets thousands of miles away is the most sophisticated and difficult aspect of the program. It must use super high speed on-board computers to study and authenticate a given target as a hostile missile (and not, for example, a manned spaceflight or a peaceful satellite.) It must point the large laser mirror at the target and hold the laser in position long enough to fire, kill and move on to a new target. And all of these functions must occur in a few seconds for the system to be effective against a ballistic missile assault.

Such a system would have to be largely self-reliant, free from man's control in many situations.

Last year's annual DARPA review stated, "advanced space-based laser weapons designed to engage strategic aircraft and ballistic missiles will require acquisition, tracking and pointing performance levels beyond those that are currently projected for the Talon Gold demonstration (in 1986)." The report noted that "substantial improvements in pointing precision and the development of rapid acquisition and retargeting capabilities will be necessary."

If these and other problems are solved in the next 10 or 20 years, a deployment of laser battle stations in space would then face an array of potential Soviet countermeasures: space mines, "smart" (computer guided) and "dumb" (conventional) antisatellite projectiles fired from earth or space that can home in and bludgeon the battle station. The Soviets might also employ antisatellite nuclear bombs, whose intense electromagnetic pulse would sizzle the circuitry of any electronic devices not "hardened" against their effects.

Soviet lasers, on the ground or in space, could be used to blind or burn out the sensor "eyes" of a U.S. battle station.

In addition, enemy ICBMs could be coated with heat resistant materials or polished to reflect laser beams. Flares and chaff and dummy missiles would likely accompany a Soviet launch and confuse the sensors on the battle stations.

Advocates think most of these problems can be overcome. They argue that the first system put into space does not have to be perfect, but would possibly lead to a near perfect defense in the next century.

The most troubling deficiency of a superweapon defense, which by its complexity would sap tens, perhaps hundreds gh planof billions of dollars out of the U.S. economy, would be its inability to stop "leakage" of some fraction of Soviet warheads that would get through even the best defensive system. The Soviets will soon have about 10,000 nuclear warheads. What if some of them get through? Theoretically, leakage of less than 1 percent could devastate America's great urban centers.

Moreover, laser battle stations in space will do little to stop low flying bombers, cruise missiles or submarine-launched nuclear missiles set on a flat trajectories. And in the extreme, what would stop the "suitcase" strategy: one hundred Soviets carrying small nuclear bombs into the country in their diplomatically protected luggage?

"They (the advocates) may argue that the U.S. could take a few hits," said Larry Smith, former staff director for the Senate Armed Services subcommittee on military research and development. "But as soon as you admit that it does not work perfectly, you are vulnerable in the extreme. Just look at the simple calculations on the effects of nuclear weapons.

"If it failed to protect Detroit or Baltimore," Smith continued, "in a one megaton blast you would lose more Americans than all of the people who were lost in all of the wars in the entire history of the Republic, which is, by any standard, a fundamental fault in the security of the homeland."

Even the optimistic Dr. Teller acknowledged some of these arguments. "If I spent $100 billion and the Soviets can undo my efforts by spending $10 billion, I am a fool. But if I spend $10 billion and to offset my effort the Soviets must spend $100 billion, then I am doing the right thing."

As for leakage, Teller said, "Why not put up three different systems, each is 90 percent leak proof and together they are 99.99 percent leak proof. That means out of 1,000 bombs fired, only one will hit."

Goodbye Baltimore, replies Smith.

Author Karas points out that Reagan is trying to rid the world of offensive nuclear weapons through the construction of a perfect defensive weapon. But Karas wonders why the president is taking risky and expensive steps toward defensive systems to rid the world of offensive weapons when he could short-circuit the process by negotiating an arms reduction agreement.

"The real thrust is that they are trying to make the world safe for nuclear war," Karas alleges.

Teller's view is different: "The Soviets consider us their only obstacle to their plans for world conquest and they consider that conquest a historic necessity, but the Soviets are very careful, they won't attack unless they are certain they can win. Also, they consider us a decadent society and as unwilling to defend ourselves.

"They believe that even if temporarily we make some effort," he continued, "it won't last, that time is on their side and that Marx has written they will win and so they will."

Doesn't Teller believe there is merit to the argument that U.S. defensive weapons would be provocative?

"I never considered defense provocative," he replied.