The National Archives has discovered that the space-age answer to retrieving facts and figures is creating a nightmare for those trying to preserve the nation's documentary heritage.

With the arrival of more computers and word processors, virtually all federal agencies, Congress and the courts are increasing their use of machine-readable magnetic tapes to store statistical and policy-making information.

But while the tapes have been a tremendous space-saver over paper, they have turned out to be tougher to preserve. Paper basically needs to be kept dry and out of direct sunlight to guard against long-term deterioration. The tapes, on the other hand, have to be shielded from the immediate effects of dust, heat, cold, humidity and magnetic fields. Any of those can cause a tape to develop a glitch or forget everything it knows -- permanently.

Even when those elements don't damage a tape, its chemical composition can cause it to self-destruct within a decade.

Although agencies eventually transfer less than 3 percent of their materials to the Archives' permanent collections, that will add up to another 2,400 tapes in fiscal 1983, each holding as much information as could be stored in nine file-cabinet drawers packed with legal-size paper.

"We have made the commitment to save the material and along with that commitment goes the responsibility of taking those preservation measures that are essential," said Trudy H. Peterson, chief of the machine-readable archives branch.

The Archives' computer tape collection includes the Defense Department's 50-tape Vietnam Data Base (covering U.S. operations in Vietnam and Cambodia, casualty and prisoner-of-war files); social indicators of equality for minorities and women (1960-78); Spanish-surname and Puerto Rican household information from the 1970 census; Education Department data on kindergarten education; Public Health Service data on health service trends; the tapes of the President's Commission on Campus Unrest (1967-70); United States Information Agency surveys of foreigners' perceptions of America, and all current industry filings to the Securities and Exchange Commission and the Civil Aeronautics Board.

From tapes that contain statistical material, such as the Vietnam file, answers to specific questions can be extracted. Others simply provide copies of reports and documents.

Threats to most tapes can be mitigated by setting up "controlled environment" rooms, but two major problems remain: getting agencies to handle the tapes more carefully before they are transferred to the Archives, and improving tapes so they don't deteriorate so fast.

Charles M. Dollar, director of the Special Archives Division, said it makes the Archives' job tougher when agencies "keep them behind a boiler in the basement before we get them."

The Commerce Department's National Bureau of Standards is studying the deterioration problem for the Archives. When the study is completed, both agencies will ask the tape manufacturers to accept voluntary standards for durability.

In the meantime, there is only one solution for the preservationists: re-record the tapes at least every 10 years.

"We have to be worried about the potential for losing historically valuable information. Not over the next year or the year after, but in the future," Dollar said. "The short-term solution [re-recording] becomes prohibitively expensive. The industry must make a less expensive, less costly storage medium."

The cost of re-recording can add up when $12.50 computer tapes and computer time at $172 an hour is involved. In fiscal 1983, the Archives will spend $101,500 to duplicate all the tapes it adds, as well as re-record each 10-year-old tape. It's not much now, but "as you cost this out over 10, 20 or 30 years, you're running into a lot of money," Dollar said.

Meanwhile, Archives officials are trying to handle more mundane problems -- such as acquiring a $170,000 computer so they don't have to contract out to read the tapes in their own collection.

Because the Archives doesn't have such a computer, users have to buy copies of tapes they want for $86 each and then provide their own computer. Those who want a printout of the information have to pay at least $57, plus computer time, compared with the Archives' 10-cent charge for a photocopied page.

"Paper is much easier to handle," Dollar concedes. But no one, he said, is talking about returning to it.