Book excerpt: Prepared for the Subcommittee on Sea Power of the U.S. Senate Committee on Armed Services. Addresses the question of how much money the U.S. Department of the Navy needs to sustain its current force of about 300 ships and 3,500 aircraft. Examines the Navy's missions, its modernization plans, and the budgetary implications of supporting the service's current and planned fleets through 2020. It also looks at four alternative force structures that the Navy might be able to sustain at roughly its current funding level of $90 billion (adjusted for inflation). Charts and tables.