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:

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.