The National Aeronautics and Space Administration was not the only federal agency to use the services of suspected ex-Nazi war criminals according to federal sources. The Army, Air Force and Navy also have used ex-Nazis in high-level research positions, the sources said.

Some are now under active investigation by the Justice Department's Office of Special Investigations (OSI), according to the sources. The OSI is responsible for tracking former Nazi war criminals in this country.

The Justice Department announced Wednesday that Arthur L.H. Rudolph, who developed the Saturn V rocket that took U.S. astronauts to the moon, left the United States last March for West Germany and renounced his U.S. citizenship rather than contest U.S. allegations that he "worked thousands of slave laborers to death" while supervising production of V2 missiles for the Nazis.

The West German government said yesterday that it plans to start an investigation of Rudolph, and Neal M. Sher, who heads OSI, said the Justice Department is willing to provide evidence to the West Germans.

Rudolph was a close friend and a co-worker of Wernher von Braun, who headed rocket research for the Nazis. They were among 118 German rocket experts secretly brought to this country by the U.S. Army after World War II in what was called Operation Paperclip. After rocket work for the Army, they both became NASA officials.

Sources said yesterday that two other secret operations, code-named Crossbow and Overcast, also brought German scientists and engineers to the United States, totaling 492 by May 18, 1948. According to NASA documents, the Air Force took 205, assigning most to the Wright Patterson Air Force Base outside Dayton, Ohio. The Army took 177, including the 118 who came with von Braun. And the Navy took 72.

NASA has refused to comment on how many of the German scientists other than von Braun and Rudolph worked for the U.S. space program. The agency is maintaining what even one of its spokesmen called a "stony silence" on the matter.

Sher has declined comment on whether his office is investigating other German scientists who came here after World War II.

But other sources familiar with OSI operations say that there are active files on many ex-Nazi scientists, including one Air Force aerospace medical expert who conducted numerous experiments on live human subjects at the Dachau concentration camp. In one experiment, women and children reportedly were immersed in icy water to determine how long it would take them to die, the sources said. The objective was to determine maximum rescue times for pilots whose planes crashed at sea.

One source said that Justice probably would have conducted an investigation of von Braun except that he died in 1977, before the creation of OSI in 1979. The source said von Braun "was a Nazi . . . in the sense that he was a good German soldier." But he added that there was no indication that von Braun was involved directly in persecution as Rudolph was.

Allan A. Ryan Jr., who preceeded Sher as director of OSI, said in an interview yesterday that he believes there are at least 10,000 Nazi war criminals currently in the United States.

In a new book, "Quiet Neighbors, Prosecuting Nazi War Criminals in America," Ryan charges that U.S. immigration policy just after the war did little to discourage former Nazis and Nazi collaborators from lying about their pasts and moving to the United States. Most entered the country under the Displaced Persons Act and have faded into quiet anonymity.

Ryan said the German scientists fell into a different category. But he and other current and former Justice Department officials said that while the scientists worked for the Nazi government, there is no reason to believe that most were war criminals actively involved in persecution.

"You have to look at it in the context of the times it took place in," Ryan said. "The Germans were at the forefront of rocketry development. These guys had it. We didn't have it, the Brits didn't have it, the Russians didn't have it. There was a sense that we needed their talents and that if we didn't get them, the Russians would."

President Harry S Truman wanted to recruit the scientists but made it clear that he did not want former Nazis who had taken part in human experimentation or persecution.

"There was a great premium placed on getting these people into the country," Ryan said. "The Army knew that Rudolph had been at the V2 missile facility. They didn't know -- but they could have found out -- about the slave labor. I'm not saying there was a cover-up. But they didn't want to go looking for things they didn't want to know."

Without the German scientists, Ryan added, "The United States probably would never have put a man on the moon."

In his book, Ryan is critical of U.S. immigration policy under the Displaced Persons Act, saying it was so concerned with excluding communist sympathizers that it did not screen out war criminals. He also criticizes a federal policy that did not actively pursue those war criminals until OSI was created in 1979.

"The overwhelming majority of Nazi criminals came through the front door, with all their papers in order . . . . They were beneficiaries of a law that virtually excluded Jews while welcoming their oppressors . . . . These immigrants were not merely ex-Nazis or Nazi sympathizers or Nazi collaborators. They were the war criminals, the handmaidens of Nazism who had personally and quite willingly taken part in the persecution of millions of innocent men, women and children."