DOD in 2001 adopted a new approach for developing new weapon systems, called evolutionary acquisition with spiral development (EA/SD), as its preferred standard. EA/SD, which is referred to informally (though not entirely accurately) as spiral development, is an outgrowth of the defense acquisition reform movement of the 1990s, and is part of DOD's effort to make its acquisition system more responsive to rapid changes in threats, technology, and warfighter needs. It is also intended to increase DOD's control over program costs, DOD program-manager accountability, and participation of high-tech firms in DOD weapon acquisition programs. DOD's goals in using EA/SD are to: get useful increments of new capability into the hands of U.S. personnel more quickly; take better advantage of user feedback in refining system requirements and developing subsequent increments of capability; mitigate technical development risk in weapon programs that are to employ new or emerging technologies; and facilitate the periodic injection of new technology into weapons over their life cycles, so as to better keep pace with technological changes. Under DOD's previous weapon acquisition method, now known as single step to full capability (SSFC), DOD would first define a specific performance requirement to be met, and then work, usually for a period of more than 10 years in the case of a complex weapon system like an aircraft or ship, to develop and build a design that, upon first deployment, was intended to meet 100% of that requirement. The core idea of EA/SD is to set aside the quest for 100% fulfillment of the requirement in the initial version of the weapon and instead rapidly develop an initial version that meets some fraction (for example, 50% to 60%) of the requirement. Field experience with this initial version is then be used to develop later versions, or blocks, of the weapon that meet an increasing fraction of the requirement, until a version is eventually developed that meets the 100% standard. Figure 1 below details the process for each block. Each block includes four phases for conceiving, developing, producing, and sustaining (i.e., supporting) a weapon system. Each phase is governed by certain acquisition rules and regulations, including entrance and exit criteria, and is subject to the requirements process, including the Initial Capabilities Document (ICD) and Capability Development Document (CDD). Each block includes its own acquisition contracts and fully funded budgets for a defined time period. As shown in Figure 1 , spiral development occurs as the second phase within a block . Spiral development is an iterative process for developing a weapon system's capabilities in which the developer, tester, and user to interact with one another so as refine (i.e., spiral down to a specific understanding of) the system's operational requirements. Spiral interaction can change the course of a system's technology development. Although EA/SD differs from SSFC in its use of block development from the outset of a program, from a program-management perspective, EA/SD is similar in some areas to SSFC, including the development milestones and reviews that are used at each development stage. EA/SD, however, is intended to be more flexible than SSFC in terms of permitting changes in a program's requirements or development path resulting from changes in threats, technology, or warfighter needs. EA/SD is also intended to be more flexible than SSFC regarding entry points into the acquisition process. Under SSFC, the dominant entry point was the beginning. Under EA/SD, in contrast, programs can enter various phases of any block (A, B, or C in Figure 1 ), depending on the maturity of the program. Under EA/SD, the final desired capability of the system can be determined in two waysâat the beginning of the program, with the content of each deployable block determined by well-understood (i.e., mature) key technologies, or along the way, with the content of each block determined by success or failure in developing less-well-understood (i.e., emerging) technologies or the evolving needs of the military user. Applying EA/SD at the outset of large weapon acquisition programs, such as the ballistic missile defense program, can create significant initial uncertainty regarding the design and ultimate cost of the systems that will eventually be procured under the program, the number of systems to be procured, and the schedule for procuring them. Applying EA/SD to other programs, particularly those intended to develop more up-to-date subsystems for improving existing weapons such as the F-16 fighter or M-1 tank, can produce much less uncertainty regarding the program's ultimate outcome. Although DOD used EA/SD for years on a somewhat limited basis, DOD decided in 2001 that EA/SD would henceforth be the "preferred" (i.e., standard or default) acquisition strategy for all types of weapon acquisition programsânewly initiated programs, existing programs for developing new weapons, and programs for upgrading weapons already in existence. EA/SD was elevated in prominence that year when DOD announced that it was applying EA/SD to its ballistic missile defense program and that the Navy's program for a new family of surface combatants would be an EA/SD program. Several defense programs are now using EA/SD. The ballistic missile defense program is a more complex case than others because it includes multiple weapon systems, some existing and some in initial development, in different phases and blocks of development. In addition, although the ballistic missile defense program has embraced most of the EA/SD model (notably, the possible absence of ultimate cost and timeline projections), it differs from other programs being pursued under EA/SD because it operates under different oversight rules instituted in January 2002 by Defense Secretary Rumsfeld. A November 2003 General Accounting Office (GAO) report on EA/SD prepared at the direction of the Senate Armed Services Committee (see " Legislative Activity " section below) concluded the following: DOD has made major improvements to its acquisition policy by adopting knowledge-based, evolutionary practices used by successful commercial companies. If properly applied, these best practices can put DOD's decision makers in a better position to deliver high-quality products on time and within budget.... The next step is for DOD to provide the necessary controls to ensure a knowledge-based, evolutionary approach is followed. For example, the policy does not establish measures to gauge design and manufacturing knowledge at critical junctures in the product development process. Without specific requirements to demonstrate knowledge at key points, the policy allows significant unknowns to be judged as acceptable risks, leaving an opening for decision makers to make uninformed decisions about continuing product development. DOD was responsive to the requirements in the Defense Authorization Act for Fiscal Year 2003 [see " Legislative Activity " section below].... This [GAO] report makes recommendations that the Secretary of Defense strengthen DOD's acquisition policy by requiring additional controls to ensure decision makers will follow a knowledge-based, evolutionary approach. DOD partially concurred with our recommendations. DOD believes the current acquisition framework includes the controls necessary to achieve effective results, but department officials will continue to monitor the process to determine whether other controls are needed to achieve the best possible outcomes. DOD agreed it should record and justify program decisions for moving from one stage of development to next but did not agree with the need to issue a report outside of the department. EA/SD poses potential issues for Congress regarding DOD and congressional oversight of weapon acquisition programs. Some of these issues appear to arise out of uncertainty over how EA/SD differs from the SSFC approach; others appear to arise out of the features of EA/SD itself. One issue for Congress, addressed in the GAO report, is whether DOD has established adequate rules and regulations for conducting internal oversight of EA/SD programs. Some observers have expressed concern about this issue, particularly with regard to the spiral development phases of programs. In support of this concern, they have cited budget justification documents for the ballistic missile program, which have included some references to block development but have provided incomplete information on how much funding is spent for specific blocks, over what period of time, and on what progress has been made to date in each block. Supporters of EA/SD argue that DOD is fully aware of the need for adequate oversight and will take steps to ensure that it is provided. Potential questions for Congress include: How does DOD oversight for EA/SD programs compare to DOD oversight of SSFC weapon acquisition programs in terms of frequency and nature of reviews, information required to be submitted to reviewing authorities, and evaluation and reporting by reviewing authorities? Will DOD oversight procedures, and review bodies be the same for all EA/SD programs, or will they vary from program to program? Another issue for Congress is how to carry out its responsibility to allocate defense spending. EA/SD poses potentially significant issues for congressional oversight, particularly for newly initiated weapon acquisition programs, in three areas: Ambiguous initial program description. Programs initiated under EA/SD may not be well defined at the outset in terms of system design, quantities to be procured, development and procurement costs, and program schedule. These are key program characteristics that Congress in the past has wanted to understand in some detail before deciding whether to approve the start of a new weapon acquisition program. EA/SD can thus put Congress in the position of deciding whether to approve the start of a new a program with less information than it has had in the past. Lack of well-defined benchmarks. A corollary to the above is that Congress may not, years later, have well-defined initial program benchmarks against which to measure the performance of the military service managing the program or the contractor. Funding projections potentially more volatile. Although projections of future funding requirements for weapons acquisition programs are subject to change for various reasons, funding projections for EA/SD programs may be subject to even greater volatility due to each program's inherent potential for repeated refinements in performance requirements or technical approaches.