is possible. The possibility of the stations being altered during gage recovery, outside effects from other shots, and the gradual change of stations with time cast a reasonable doubt on the validity of the data available. CONCLUSIONS. It is concluded that: 1. A suitable factoring system can be developed for adjusting raw crater data to a standard condition. Additional data, of different media response to shocked conditions, is needed in order to develop these factors. This can probably be done by a system of high-explosive tests under controlled conditions so that parameters such as soil strength, void ratio, moisture content, and density can be varied and their effects on crater size evaluated. 2. Results of Operation Hardtack plus previous results of Operation Redwing have conclu- sively indicated that the detonation of devices inside relatively small water tanks appreciably increases the crater dimensions by acting as tamping material. 3. The cratering curves given in TM 23-200 for water surface burst are not in agreement with craters measured from Operation Hardtack barge shots. Craters formed under these conditions were larger than previously expected. RECOMMENDATIONS It is recommendedthat: 1. A more refined factoring system for adjusting crater dimensions be developed so that shot data can be reduced to a standard condition. 2. Future detonations of nuclear devices having unusual environmental conditions be closely monitored for associated effects on craters. REFERENCES 1. F.B. Porzel; “Ground-Shock Measurements: Crater Survey”; Annex 1.6, Part VI, Section 2, Operation Greenhouse, WT~—109, December 1953; Los Alamos Scientific Laboratory, Los Alamos, New Mexico; Secret Formerly Restricted Data. ° 2. J.L. Gaylord, Lt Col, USAF; “Photographic Crater Survey”; Project 3.7, Operation Ivy, WT-—618, March 1953; Lookout Mountain Laboratory, Los Angeles, California; Unclassified. 3. R.B. Vaile; “Crater Survey”; Project 3.2, Operation Castle, Wr—920, June 1955; Stanford Research Insititute, Stanford, California; Secret Formerly Restricted Data. 4. J.G. Lewis, F.E. Deeds, Capt, CE, and A.W. Patteson; “Crater Measurements”; Project 1.8, Operation Redwing, WT—1307, March 1959; U.S. Army Engineer Research and Development Laboratories, Fort Belvoir, Virginia; Secret Formerly Restricted Data. 5. “Capabilities of Atomic Weapons”; TM 23-200, Revised Edition, November 1957; Armed Forces Special Weapons Project, Washington, D.C. ; Confidential. 6. J.G. Lewis; “Crater Measurements”; Project 1.6, Operation Teapot, WT—1105, July 1958; Engineer Research and Development Laboratories, Fort Belvoir, Virginia; Confidential Formerly Restricted Data. 7, Donald L. Martin; “Nuclear Cratering Phenomena”; Subproject 8-12-95-400, Prepared for the Directorate of Targets, ACS/Intelligence, USAF, Washington 25, D.C., draft manuscript; Engineer Research and Development Laboratories, Fort Belvoir, Virginia; Secret. 8. “Effects of a Soil-Rock Interface on Cratering’ ; AFSWP—-1056, May 1958; U.S. Army Engineer Waterways Experiment Station, Corps of Engineers, Vicksburg, Mississippi; Unclassified. 43