No one who investigates segments of NASA's history will underestimate the difficulty of finding out what happened and why. Particularly in the study of organization and management, the researcher is pretty much on his own. Organization charts and management instructions are the visible tip of an immense mass of submerged documentation. Researchers who enjoy the thrill of the chase will find themselves fully occupied, and not least among their problems will be locating primary sources. They will have to contend with the sources' dispersal throughout headquarters, center offices, and the Federal Records Centers to which they are eventually retired; the absence of catalogues or data retrieval systems comparable to those maintained by NASA for indexing and classifying aerospace literature; and the lack of uniformity in those records inventories that are available. There has never been a central file or filing system at NASA Headquarters. The responsibility for maintaining, inventorying, and retiring records rests with each office. The only general guide to NASA internal documentation is GSA form 135, which every Federal agency fills out before retiring records. The same caution applies to these forms as to the documents they describe: some are detailed and precise, others are cursory at best.
These deficiencies are not ameliorated by the published material. When one has eliminated promotional literature, spaceflight stories "as told to" Able and Ham, and the kind of learned lumber that spares the reader no smallest detail, one is left with a residue of works that attempt to deal with the space program in a scholarly way. Yet, with one exception, no book tries to get the whole of NASA between two covers. The exception, Frank W. Anderson, Jr.'s Orders of Magnitude (NASA SP-4403, 1976), is brief-less than 100 pages-concise, well written, and one of very few works that treat the histories of NACA and NASA together. But no work that was prepared as a chapter for a bicentennial history of public works in the United States can claim to be definitive. In short, an essay on NASA administrative history must draw on a multitude of sources without relying too heavily on any one of them.
 There remain the periodic official reports on U.S. space activities. Three o these, sponsored by NASA, may be ranked in ascending order of usefulness:
Apart from interviews, congressional hearings, and the sources mentioned, the research on which this book is based rests principally on two collections: the files of the NASA History Office at NASA Headquarters in Washington, D.C., and the NASA documents housed at the Federal Records Center in Suitland, Maryland. There is no need here to describe the resources of these collections; Alex Roland's Guide to Research in NASA History (2d ed., NASA History Office, Nov. 1977) covers the ground most adequately. Rather, I would like to mention the ways in which I have used the material in an administrative history of an agency as large and diversified as NASA.
One limitation is the fragmentary quality of the sources. The reader who expects the documents to deal with large subjects in a large way will be disappointed. Their value consists in their confirmation of particular facts, as controls on other documents, and as bases for presentations of agency programs that were entered into the annual congressional authorization hearings. Occasionally a source gives an historical account of specific programs or organizational entities; examples include staff papers on NASA excepted positions, on the rationale of the Apollo engineering support contracts, on NASA responses to recommendations of  the House Science and Astronautics Committee, and on executive recruitment. The program reviews held for Webb fall into the same category. However, such papers, most of which were never circulated outside the agency, are the exception. The gap between official statements of policy and internal decision making is often uncomfortably wide, and that gap is only partly closed by internal documents, interviews, and presentations before NASA's authorization and appropriations committees. To a degree, the historian's terms of references are bounded by the evidence; I have tried to deal with problem areas for which inadequate supporting documentation exists.
A special case is presented by the tape recordings stored at Suitland. In 1966-1967 several dozen management meetings were taped. While the purpose of the recordings is not entirely clear, most seem to have been prepared as reference material for edited transcripts and-given Webb's strong interest in the study of public administration-as source material for studies such as this book. The tapes run from forty-five minutes to three hours and cover most of NASA's substantive program reviews, as well as strategy sessions attended by NASA senior officials. Few transcripts are available, and most of the tapes have been unused and unheard since they were sent to Suitland a decade ago. Their value is less in disclosing previously unknown facts than in giving a remarkable glimpse of the give-and-take of NASA decision making at the highest level. We hear Webb, Mueller, and Phillips in a dry-run rehearsal for a congressional hearing in executive session on the Apollo fire. We hear Edgar Cortright briefing Webb on the Voyager program and explaining how the program would be parceled out among the centers. As another example, the briefing held for Webb on negotiations for renewal of NASA's contract with JPL is a franker account of NASA relations with the laboratory than anything NASA would have cared to submit in public hearings. Apart from the notorious exception of the Nixon tapes, the NASA tapes are a unique record of the decisions made by senior Federal officials Not all the tapes are as valuable as the three just cited. But as a whole, they are an unusual and almost unknown historical resource, and it would be a service to scholars to have the best of them transcribed and edited.