There have been several models developed either for laboratory reference or for test control conditions. They have been assessed re- cently by the Armed Forces Special Weapons Projectt2/ and the summation of the various fall-out models is presented here in its entirety from that report: Armed Forces Special Weapons Project Method This method is based on ground surveys at JANGLE (surface) and CASTLE Bravo, end consists of "idealized" contours which follow a single scaling wind direction. Abrupt wind shears and unusual weather conditions are not easily handled. The method is suitable for planning purposes only, not for post-shot analysis. An order- of-magnitude contour can be drawn for any weapon yield between 0.1 KT and 100 M? in two or three minutes by trained personnel. Air Research and Development Command Method The model assumes that 90% of the bomb debris activity is in the stem of the stabilized cloud, and 10% is in the muskroon. Mean effective particle sizes are assumed for the cloud and parts of the stem, and Stokes' law fall rates for spherical particles are used. Wind and weather conditions are allowed for. The method is calibrated to CASTLE Bravo, but is adaptable over a wide range of yields. A problem solution requires several hours by trained personnel. Army Signal Corps Method The model divides a hypothetical stabilized bomb cloud consisting of superposed cylinders into dise or cylindrical wafers or compartments, each associated with a particular particle size category and fall rate. Each disc is then brought to the ground accord- ing to the winds acting on it, and ground values are then summed over all the discs to obtain contours. A different model must be generated for each weapon yield, and for different localities: a Armed Forces Special Weapons Project, Fall-out Symposium (Confidential) AFSWP-895, January 1955, SECRET Restricted Data 51