The second layer of the armor is part of the power armor proper. The first is a black body suit worn by the operator for comfort, insulation, and protection from injuries that may be sustained during the armor's operation. The T-45 model D (its most popular variant) is designed for a single operator and is patterned closely after the human silhouette. The most important was the implementation of back-mounted fusion packs, rather than relying on the limited supply of small energy cells, consumed by the armor at an alarming rate. This temporary solution would eventually become the mainstay of American power armor units, especially as subsequent upgrades reduced the impact of the mobility problems that plagued the early production runs. The speed at which it had to be deployed, less than two years after the development of power armor began, resulted in the creation of a stop-gap model utilizing existing technologies and manufacturing techniques.
The T-45 powered combat infantry armor was the first design pressed into service in the Sino-American War, with its first deployments taking place on the Alaskan Front to counter the Chinese offensive.
