loads sometimes exceeding 100 pounds or more for extended missions (Figure 2-3). A substantial fraction of that load is associated with the energy supply needed to power the Soldier in the form of food, to power his lethal equipment in the form of explosives or propellants, and in the form of batteries to drive the ever-expanding array of electronic tools designed to improve his fighting skills and make him more decisive.

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FIGURE 2-3. The modern warrior with combat load during dismounted operation in Afghanistan. SOURCE: CALL, 2003.

For a dismounted mission, Soldiers must carry all of their energy in various storage formats or rely on others to provide them with timely resupply. In any case, it requires expenditure of energy to construct suitable energy storage devices that dismounted Soldier will use in addition to requiring energy to transport resupply to them. These expenditures translate to monetary costs to produce energy storage units, transport the units to the Soldier, and store them in theater. To a large extent, these costs drive what is available. Since Soldiers are limited in what they can carry, improving the density of energy storage media is a primary concern. Different modes of energy storage can be compared using a common measure of energy density such as watt-hours per kilogram. A concern for efficiency in developing and distributing energy resources also leads to the need for an energy cost metric, such as dollars per watt-hour or dollars per gallon of logistic fuel, delivered to the Soldier.

How Much Energy Is Needed as a Function of Mission?

For each mission, there is an associated energy requirement to carry out that mission. It is instructive to examine the source of the total mass associated with the energy needed to carry out a particular mission. The energy sources currently in use are ultimately traceable to energy stored in chemical bonds,



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