The CG(X) cruiser is the Navy's planned replacement for its 22 existing Ticonderoga (CG-47) class Aegis-equipped cruisers, which are projected to reach retirement age between 2021 and 2029. The CG-47s are multimission ships with an emphasis on air defense. The Navy wants the CG(X) to be a multimission ship with an emphasis on air defense and ballistic missile defense (BMD). The Navy plans to equip the CG(X) with a large and powerful new radar capable of supporting BMD operations. The CG(X) may also have more missile-launch tubes than are on the DDG-1000, and one 155mm Advanced Gun System (AGS), or none, as opposed to two AGSs on the DDG-1000. The Navy's planned 313-ship fleet calls for a total of 19 CG(X)s. The FY2008-FY2013 Future Years Defense Plan (FYDP) calls for procuring the first CG(X) in FY2011 and the second in FY2013. The Navy's 30-year (FY2008-FY2037) shipbuilding plan calls for building 17 more CG(X)s between FY2014 and FY2023, including two CG(X)s per year for the seven-year period FY2015-FY2021. The Navy is currently assessing CG(X) design options in a study called the CG(X) Analysis of Alternatives (AOA), known more formally as the Maritime Air and Missile Defense of Joint Forces (MAMDJF) AOA. The Navy initiated this AOA in the second quarter of FY2006 and plans to complete it by mid-September 2007. Navy plans call for Milestone A review of the CG(X) program in the first quarter of FY2008, preliminary design review (PDR) in the third quarter of FY2010, critical design review (CDR) in the third quarter of FY2011, and Milestone B review in the fourth quarter of FY2011. Although the CG(X) AOA is examining a wide range of design options for the CG(X), the Navy has publicly stated on several occasions that would like to use the design of its new DDG-1000 destroyer as the basis for the CG(X). (The potential for using the DDG-1000 design for the CG(X) was one of the Navy's arguments for moving ahead with the DDG-1000 program.) At an April 5, 2006, hearing, for example, a Navy admiral then in charge of shipbuilding programs, when asked what percentage of the CG(X) design would be common to that of the DDG-1000 (previously called the DD(X)), stated the following: [W]e haven't defined CG(X) in a way to give you a crisp answer to that question, because there are variations in weapons systems and sensors to go with that. But we're operating under the belief that the hull will fundamentally be—the hull mechanical and electrical piece of CG(X) will be the same, identical as DD(X). So the infrastructure that supports radar and communications gear into the integrated deckhouse would be the same fundamental structure and layout. I believe to accommodate the kinds of technologies CG(X) is thinking about arraying, you'd probably get 60 to 70 percent of the DD(X) hull and integrated (inaudible) common between DD(X) and CG(X), with the variation being in that last 35 percent for weapons and that sort of [thing].... The big difference [between CG(X) and DDG-1000] will likely [be] the size of the arrays for the radars; the numbers of communication apertures in the integrated deckhouse; a little bit of variation in the CIC [Combat Information Center—in other words, the] command and control center; [and] likely some variation in how many launchers of missiles you have versus the guns. If the CG(X) is based on the DDG-1000 design, its unit procurement cost might be comparable to that of the DDG-1000. The FY2008-FY2013 FYDP includes notional "placeholder" figures of about $3.2 billion in FY2011 to procure the first CG(X) and about $3.1 billion in FY2013 to procure the second CG(X). This compares with about $3.2 billion to procure each of the first two DDG-1000s in FY2007-FY2008. Early Navy plans called for procuring two DDG-1000s per year, and a total of 16, 24, or 32 ships. In large part for affordability considerations, planned DDG-1000 procurement was reduced to one ship per year, and a total of 7 ships. If affordability considerations similarly limit CG(X) procurement to one ship per year, total CG(X) procurement might be reduced from 19 ships to perhaps no more than 12 ships, and possibly as few as eight. Some observers, including the Congressional Budget Office (CBO), have expressed concern about the prospective affordability and executibility of the Navy's long-range shipbuilding plan. Some Members of Congress, particularly Representatives Gene Taylor and Roscoe Bartlett, the chairman and ranking member, respectively, of the Seapower and Expeditionary Forces subcommittee of the House Armed Services Committee, strongly support expanding the use of nuclear propulsion to a wider array of Navy surface ships, beginning with the CG(X). Nuclear propulsion is an option being studied in the CG(X) AOA. If the CG(X) is to be a multimission ship for replacing the CG-47s, basic design options for the CG(X) include (but are not limited to) the following: a conventionally powered ship based on the hull design of the 9,200-ton Arleigh Burke (DDG-51) class Aegis destroyer, or on a variation of that hull design; a conventionally powered ship based on a new-design hull that is smaller than the DDG-1000 hull; a conventionally powered ship based on the DDG-1000 hull design or on a variation of that hull design (the Navy's stated preferred approach); a conventionally powered ship based on a new-design hull that is larger than the DDG-1000 hull; and nuclear-powered versions of each of these four ships. Basing the CG(X) on the current DDG-51 hull could produce a CG(X) design displacing roughly 9,000 tons. Lengthening the DDG-51 hull with a mid-hull plug might produce a CG(X) design displacing roughly 11,000 tons, which would be about 24% smaller than the 14,500-ton DDG-1000, and roughly as large as the six California (CGN-36) and Virginia (CGN-38) class nuclear-powered cruisers that were procured for the Navy in the 1960s and 1970s. The deck house and lower decks of the DDG-51 hull would need to be redesigned to accommodate a radar capable of supporting BMD operations, an integrated electric-drive propulsion system, other new technologies from the DDG-1000, and (if desired) missile-launch tubes large enough to accommodate a BMD interceptor now in development called the Kinetic Energy Interceptor (BMD). Since the DDG-51 hull design was originally developed in the 1980s, it may include hard-to-change features that prevent it from fully accommodating certain DDG-1000 new technologies, such as, perhaps, those permitting the ship to be operated by a substantially smaller crew. For ships of a similar type and level of complexity, relative size can be rough proxy for relative unit procurement cost. A 9,000- to 11,000-ton CG(X) would be 62% to 76% as large as a 14,500-ton DDG-1000-based CG(X). However, some shipbuilding costs, such as shipyard fixed overhead costs, do not go down proportionately with ship size. A DDG-51-based CG(X) consequently might cost more than 62% to 76% of what a 14,500-ton CG(X) would cost to procure—perhaps something more like 72% to 86%. Production of a DDG-51-based CG(X) might benefit from residual learning-curve effects of prior production of DDG-51s, the last of which was procured in FY2005. Any limitations in incorporating DDG-1000 technologies for reducing crew size could result in a ship with a larger crew than that of the DDG-1000, and thus higher crew-related life-cycle O&S costs than a DDG-1000-based CG(X). The DDG-51 hull is a conventional flared hull that slopes outward as it rises up from the waterline. A CG(X) based on the DDG-51 hull consequently would be more detectible by radar than a ship using a tumblehome (inwardly sloping) hull, like that of the DDG-1000. In addition, as ship size grows, so does the size of the ship's weapon and sensor payload. Consequently, larger ships generally have more capability than smaller ones. Indeed, due to certain economies of scale that occur in naval architecture, larger ships can have proportionately larger payloads than smaller ones. Thus, a DDG-51-based CG(X) might be less than 62% to 76% as capable as a 14,500-ton CG(X). Due to the space, weight, and energy requirements of the large and powerful BMD-capable radar to be carried by the CG(X), accommodating such a radar in a DDG-51-based CG(X) design might require steep reductions in other ship capabilities.