An adequate theory of weapon effects will, when it is fully developed, permit an accurate prediction of the military damage achieved when a weapon is delivered under ideal conditions. The degradation in actual use due to unreliability, to enemy countermeasures, and to delivery errors leads to a second major field ‘of study. Weapon analysis is a study of the military worth of a weapon based on knowledge of weapon effects and of the several factors which reduce the performance of a system below the ideal. Functional reliability has been recognized from the start as an important factor in any system. However, improved techniques have been developed for determining the reliability of systems and of individual components, and have in turn pointed out areas for profitable improvement. The dual motor IF] is an example of such component improvements. An important change during the past three years has been the increased realization that evaluation of a system must also include a study of the human aspects of its expected use. Human engineering studies and close liaison with the Military have led to more realistic requirements and, in turn, to systems of reduced complexity. The development or improvement of components resulting both from the weapons analysis studies already mentioned, and from engineering requirements, also has been im- portant. Creation of two departments with the direct responsibility in this area has resulted in increased contributions to the weapons program, One departmentis responsible for radar and test equipment development. The other department concerns itself with mechanical and electrical components. The research organization also has given direct support to the engineering groups in several fields of specialization. For example, an aerodynamics group has been established with responsibility for specifying the shapes of ballistic cases. Extensive use of wind tunnel testing, consultation with leading aerodynamic institutions, and theoretical work has greatly reduced the time and expense necessary for the design and testing of new ballistic weapon shapes. Tests of Assemblies, Components and Over-All Weapons During the course of development and evaluation, many tests of a new weapon and its components are made to determine and assure weapon suitability and reliability. For example, the following tests were made of one typical free-fall bomb (Mk 5) and its compo- nents: Over-All Weapons Tests These include: Drop tests (25 weapon, complete with fuze but without live HE, were dropped to acquire performance and reliability data; and 36 were dropped to acquireballis- tic data); catapulting and arresting tests (one weapon complete with fuze was subjected to 17 catapultings, and 12 arrested landings); dynamic stress tests of bomb with fuze (1 tested); temperature distribution tests (1 tested); aircraft compatibility tests (to determine bomb bay clearance and separation characteristics of bomb and 13 carriers). DOLD 70 ate ‘The specific information obtained in weapons effects measurements has been interpreted by analytical groups to predict the reaction of various target complexes to atomic bursts. The variation in effect on the target has been studied-as a function of bomb yield and burst location, and these studies have provided information on the change in target damage due to burst height and delivery errors. To speed up these studies, which are tedious in practice, the research group has developed analog computing devices, an example of which is the bombing evaluation computer.