In the 1970s the Navy discovered from underwater listening posts that the Soviet Alfa nuclear attack submarine could go faster than 40 knots, about 10 knots more than the fastest U.S. subs.

A secret study was launched to find out why, and the first suspect was grease.

The Soviets, it was argued in hush-hush sessions of Navy and Pentagon analysts, must be greasing the hulls of their subs so they would slide through the water more easily.

Take the Albacore out of the reserve fleet, went the order, rig her bow with the piping needed to spray lubricant along the hull as she plows along and see what happens.

The Albacore went 20 to 30 percent faster as long as the polymer lubricant stayed on the hull, reducing friction.

For a while, it looked as if the worrisome mystery of the Alfa's speed had been solved and the Soviets, who had been thought to be behind us in nuclear propulsion, had found a gimmick. But Pentagon officials said this is no longer the prevailing theory. They say it looks instead as if the Soviets have managed to build a nuclear reactor that generates more power for its size and weight than the U.S. counterpart.

Despite this suspicion, the Navy still plans to build bigger in order to go faster, as it always has sought to do before. It will ask for big money next year to start on a new generation of nuclear attack sub.

But some on Capitol Hill say they believe this is the wrong way to go. They intend to challenge the "bigger is better" theory and urge more emphasis on innovation in both nuclear power plant and hull to reduce size and increase speed.

Such efforts ran aground in the past. The nuclear Navy's now-retired admiral Hyman G. Rickover got his way year after year. But Alfa's speed, the rising cost of U.S. subs, Pentagon budget pressures and Rickover's departure may make for rougher sailing for the Navy.

The Navy plans to build a new class of nuclear attack subs considerably larger than the current 6,900-ton Los Angeles class subs. A Los Angeles class sub costs about $661 million. It was billed as "high speed" when first deployed in 1976 and is believed to have a top speed of a little more than 32 knots.

In the belief that the sub design issue will be a major one by next year, some congressional aides are drafting questions for their bosses on whether it would make more sense to take a leaf out of the Soviet book by building smaller and faster attacks subs.

Anthony R. Battista of the House Armed Services Committee staff, for example, believes such tricks as squirting lubricant against the hull or shooting jets of fluid out the stern to dash away from an enemy or in for an attack deserve a closer look by the Navy. Earlier this year he told the Armed Services research subcommittee that the Soviets may have perfected such techniques.

Pointing to a picture of the Soviet cruiser Kirov, Battista told the panel, according to the transcript of the hearing: "Moving along at 20 knots, it has a bow wave that correlates to a 3-knot motion, but it has a substantial rooster tail that makes it appear as if it is going faster. You wonder if perhaps they are not injecting some kind of fluid through the bow, squeezing it out the stern perhaps."

After the Navy demonstrated with the Albacore that greasing a submarine for speed was possible, Pentagon officials debated in secret sessions whether polymers and other tricks should be incorporated into U.S. submarines. It would be much cheaper than continuing to build bigger and bigger nuclear power plants to achieve a few more knots. And experiments showed that the polymer fluid dissipated so quickly than no telltale signs were left in the ocean for submarine hunters to track.

But opponents of relying on greasing submarines countered that the tank of lubricant might run dry before a sub finished its 60-to-90 day patrol. Better to keep relying on more powerful nuclear power plants, their argument went.

Opponents of greasing subs prevailed in the 1970s. They drew comfort, officials said, from the theory that this quick-fix trickery, not a more advanced and thus worrisome nuclear power plant, explained Alfa's record speed. The Pentagon's 1983 edition of the booklet, "Soviet Military Power," states that the titanium-hull Alfa, which travels "at 40 knots," is the "world's fastest."

However, the underwater detective work on the Alfa continued after the Albacore tests. Recently, new clues suggest that the comforting lubrication theory is flawed. The Soviet Union, officials said, may have advanced into reactors cooled with liquid metal, rather than water, to achieve hotter temperatures and thus more efficiency in their submarine power plant. The smaller the power plant, the smaller the submarine can become.

The advanced reactor theory gained adherents from information gathered by U.S. submarines hiding outside Soviet ports to keep track of Soviet subs going out to sea, officials said. A U.S. sub lying in an ambush position can record the sounds the passing Soviet sub makes without giving any sound.

Defense officials said the telltale propeller beat of the Soviet Alfa submarine undercut the greasing theory, although lubrication still may be part of the answer to Alfa's speed. If lubrication were the complete answer, explained one official, Alfa's propeller beat would remain fairly constant as the sub's speed increased from greasing the hull.

But Navy sleuthing, which went beyond eavesdropping, gathered evidence that Alfa's propeller turned proportionally faster as the sub's speed increased. This strengthened the later theory that the Soviets have found a way to get more power out of small reactor than has the United States.

While some Pentagon officials contend that smallness means a submarine can sail faster and be less vulnerable to detection than a larger sub, others maintain that it is the sensors and weapons that decide who lives and who dies in the deep where sound is the giveaway. It takes big submarines to accommodate all the equipment for hunting down and killing submarines, they argue. Thus, they assert, the next attack submarine must be even bigger than the Los Angeles class.