Design Report Guided Missile Submarine SSG(X) - AOE - Virginia ...

SSG(X) Design – VT Team 3 Page 11
3 Concept Exploration
Chapter 3 describes Concept Exploration. Trade-off studies, design space exploration and optimization are
accomplished using a Multi-Objective Genetic Optimization (MOGO).
3.1 Trade-Off Studies, Technologies, Concepts and Design Variables
Available technologies and concepts necessary to provide required functional capabilities are identified and
defined in terms of performance, cost, risk and ship impact (weight, area, volume, power). Trade-off studies are
performed using technology and concept design parameters to select trade-off options in a multi-objective genetic
optimization (MOGO) for the total ship design. Technology and concept trade spaces and parameters are described
in the following sections.
3.1.1 Hull Form Alternatives
SSG(X) hull alternatives are chosen based on a set of performance metrics and other considerations. From
these a list of general requirements for the submarine hull is formed and initial design variables and parameter
ranges are specified. This defines the design space from which hull form alternatives are selected for consideration.
The performance metrics are selected based on the mission needs of the SSG(X). Efficiency in transit dictates
the selection of a hydrodynamic hull for low resistance. However, the submarine will not only transit, but must be
able to operate agilely in littoral regions; therefore, dynamic stability and maneuverability are important factors in
the design. To maintain structural efficiency, weight is kept to a minimum. The SSG(X) must be producible and
affordable. The diameter of the submarine must be greater than 22 feet to carry the missile payload and
accommodate the Vertical Launch System (VLS).
A traditional teardrop shape was selected for the hull of SSG(X). The teardrop shape has an elliptical bow and
parabolic stern and was chosen based on its low submerged resistance. This shape is modified by the addition of
parallel midbody for arrangements and machinery and mission spaces. The traditional teardrop and modified
teardrop shapes are shown in Figure 4. The pressure hull will be axis-symmetric for structural efficiency and
producibility. The hydrodynamic envelope may have a slightly larger beam than depth. Two or three decks may be
included in the pressure hull; these decks will have a height between 7 and 8 feet. A lower bilge for batteries and
tankage with a height between 6 and 8 feet will also be included in the pressure hull. The ranges for the diameter,
length, beam, and fore and aft body characteristics are shown in Table 6. The parameters ηf and ηa are exponents
that describe the fullness of the fore and aft bodies as shown in Figure 4.
Figure 4 - Teardrop and Modified Teardrop Hull Forms [MIT Jackson Notes]