One year after President Reagan's dramatic ''Star Wars'' call for new defenses against nuclear weapons, the push is on to make it reality. The White House is about to name a ''Star Wars'' ''czar'' who will report directly to Defense Secretary Caspar W. Weinberger and oversee a stepped-up program of technical research.
The administration wants nearly $2 billion in its fiscal 1985 budget for spending in this area, a 71 percent jump over current annual spending. The total bill will reach $24 billion over the next five years, according to administration estimates, and it is likely to spiral upward from there.
In fact, there is much more to this than just defending against Soviet missile warheads, important as that is.
Increasingly, it is felt, the next battleground will be directed from, if not located in, the high ground of space. And many of the ''Star Wars'' technologies being explored will be just as important in any high-tech conventional war of the future, featuring ''real time'' intelligence and battlefield rockets whose sensors provide pinpoint accuracy.
There is much overlap, too, with the new United States antisatellite weapon, which recently had its first test shot. Still, the subject remains highly controversial, even within the administration itself.
''No one knows how effective defensive systems can be made, nor how much they might cost,'' says one administration expert.
Will it work? No one is promising a magic bullet that could actually render nuclear warheads ''impotent and obsolete,'' as the President suggested a year ago.
''We're not talking about a force field that is absolutely impenetrable over the entire United States,'' White House science adviser George A. Keyworth II said last week. But recent rapid advances in data processing and lasers at least make the notion of defending against missile attack worth exploring, it is felt.
Critics warn that any system inevitably will allow a few nuclear weapons to penetrate and therefore could heighten nuclear tensions. But this may miss the point, Dr. Keyworth and other scientists respond. They are optimistic that enough enemy missiles and warheads could be zapped (with directed-energy) or splattered (with very high-speed projectiles) that an opponent could not be comfortably sure that his attack would succeed.
This new form of deterrence, based on increased uncertainty, it is argued, is better than the old massive-retaliation policy, dubbed mutual assured destruction.
Officials are stressing that this is all merely speculative and that they are just probing the technological possibilities. Some tests in space could be carried out before the end of the decade, but actual deployment of an advanced missile defense system is not envisioned until after the year 2000.
''There are significant uncertainties which need to be answered before we can make any major decisions on deployment or indeed on full-scale development,'' concedes a senior Pentagon official.
But officials also warn that the US must develop a hedge against Soviet advances in ballistic missile defense. The Soviet Union has the world's only operational antiballistic missile (ABM) system, albeit a relatively unsophisticated one. But it is building new antiaircraft systems that could have potential for missile defense, as well as radars that US officials suspect may violate the 1972 ABM Treaty.
Former National Aeronautics and Space Administration chief James Fletcher, who headed a presidential panel exploring missile defense technologies, recently warned that there is ''striking evidence that the Soviet Union has pursued with vigor all of the technologies . . . many of which we do not even understand yet.''
During the 1960s, the US developed and briefly deployed a limited system of rockets designed to intercept incoming warheads.
The technologies being explored today include the engagement of enemy weapons just before impact, as well as a layered defense that projects farther out into space.
But the most recent scientific developments offer the promise of damaging or destroying ballistic missiles shortly after liftoff from an attacking country halfway around the world, before they have a chance to disperse their many nuclear warheads, decoy warheads, and other devices that are part of such an attack.
Defense officials outline five areas on which research efforts will be focused:
* Surveillance, target acquisition, and tracking. This includes optical imaging using lasers rather than radar beams and the processing and transmitting of signals almost immediately (in ''real time'').
* Directed-energy weapons. Included here are ground-based lasers (in some cases, bounced off mirrors in space), space-based lasers, space-based particle beams, and nuclear-driven directed-energy weapons to attack enemy rockets during early boost and post-boost phases of flight.
* Kinetic-energy weapons. These include interceptor missiles and ''hyper-velocity gun systems'' to attack enemy warheads that have survived earlier defenses and are in midcourse or nearing their target.
* Systems analysis and battle management. Building survivable command, control, and communication systems could present the biggest challenge, officials say, especially in ultrasophisticated computer software.
* Support programs.
While officials see the need to pursue ''Star Wars'' technology, they also admit that the challenge is great.
Says Undersecretary of Defense Richard DeLauer: ''Many of our weapons and sensors will require orders of magnitude performance improvements to accomplish the President's defense objectives.''
With federal deficits in mind, lawmakers at the moment are more concerned with the cost of ''Star Wars'' missile defenses than with technological possibilities.
White House science adviser Keyworth says overall costs may not need to be more than the US already is spending - and intends to spend - on strategic weapons like the MX missile.
But some senior Pentagon officials have expressed concern about the cost of developing and deploying ground- and space-based missile defenses which, they warn, could be very high.
At a congressional hearing last week, Republican Sens. Barry Goldwater of Arizona and Pete Wilson of California were among those insisting that the Pentagon provide more detail on the cost of space defense systems.