"NOVA," public television's reliable science documentary series, begins its fourth season tonight with the darkly engrossing story of "Hitler's Secret Weapon," which airs at 8 on Channel 26.

The hours has been culled from hundreds of thousands of feet of captured film. Much of it is undoubtedly what the German people were shown of the development of the V-1 and V-2 rockets in World War II.

"Weapon" restricts itself to the German role in the development of rocketry (U.S. pioneer Robert H. Goddard is only mentioned, for instance) but youngsters with a scientific bent will undoubtedly divine that German science was, without doubt, preeminent in the field.

The sophisticated viewer will be fascinated with the justifications from Wernher von Braun and Gen. Walter Dornberger which convey, unwittinly, the manner in which the best scientific minds can sidestep the consequences of their work while trying to prove a scientific point.

The V weapons (the "V" stood for "vengeance") that terrorized London and Antwerp as the war neared its end were the result of a loophole in the Versailles Treaty, which failed to ban rocket weapons.

As they tell the story tonight, von Braun and Dornberger, who eventually led 124 top rocket scientists to the U.S. side at war's end, played the two services against each other to get huge budgets from each.

Eventually, 30,000 technicians were working at Peenemunde as the projects developed.

In October 1942 the first V-2 was successfully launched, the forerunner of the vehicles that took the U.S. to the moon and back. As related tonight, it was a major scientific moment in 20th-century science.

Meanwhile, the German war effort was failing. In one fascinating aside von Braun relates how he and Dornberger took a carefully prepared film to Hitler and convinced him to continue the faltering program.

What is not remarked on is that their success led to the death of thousands in London and Antwerp when the horror weapons finally fell. It is this cold ambivalence in the story-telling that makes "Weapon" a chilling hour to watch.