This part of the manual presents methods for arriving at a solution to the problem of spacecraft inflight equipment environmental control. The temperature aspect of this problem may be defined as the maintenance of a proper balance and integration of the following thermal loads: equipment-generated@ personnel-generated@ and transmission through external boundary. Achievement of such a thermal energy balance involves the investigation of three specific areas:1. Establishment of design requirements.2. Evaluation of properties of materials.3. Development of analytical approach. The solution to the problem of vehicle and/or equipment pressurization@ which is the second half of major environmental control functions@ is also treated in this section. Pressurization in this case may be defined as the task associated with the storage and control of a pressurizing fluid@ leakage control@ and repressurization. Although secondary to the thermal energy balance@ the function of pressure control is nevertheless an important aspect of the overall environmental problem.?