Design Report Guided Missile Submarine SSG(X) - AOE - Virginia ...
Design Report Guided Missile Submarine SSG(X) - AOE - Virginia ...
Design Report Guided Missile Submarine SSG(X) - AOE - Virginia ...
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<strong>SSG</strong>(X) <strong>Design</strong> – VT Team 3 Page 68<br />
4.5 Power and Propulsion<br />
Figure 58 - Midship Section<br />
The <strong>SSG</strong>(X) propulsion system consists of two open-cycle CAT 3512 V12 diesel engines for use during<br />
snorkel, two 500 kW PEM fuel cells used during submerged operations, and 5820 kw-hr nickel-sodium Zebra<br />
batteries. The PEM fuel cells use hydrogen, stored in a solid hydride outboard of the pressure hull, and pure<br />
oxygen, stored in liquid form in the pressure hull. The <strong>SSG</strong>(X) houses an Integrated Power System (IPS) to divide<br />
power throughout the ship and power the RDP.<br />
The process for determining the power and propulsion requirements begins with creating a hand calculation<br />
math model. The model calculates resistance, SHP requirements, and AIP, sprint, and snorkel endurances. The<br />
calculated values must satisfy the ORD requirements and should closely correlate to the values produced by the<br />
MOGO. After endurance calculations are determined to be consistent with the MOGO a prop optimization is run.<br />
The prop is initially optimized based on AIP, but adjusted to ensure no cavitation at other speed conditions. Prop<br />
characteristics are plugged into the math model and the endurances are checked with the ORD. Corrections must be<br />
made if the calculated endurances due not meet the ORD. .<br />
4.5.1 Resistance and Effective Horsepower<br />
Submerged bare hull resistance calculations are performed using a modified Gilmer and Johnson method and<br />
checked with the MIT Harry Jackson method. Figure 59 shows the VT method. The initial values used in this<br />
method correlate closely with those from the MOGO. The viscous resistance was found using a modified Gilmer<br />
and Johnson form factor and an ITTC coefficient of friction with uses a 30% correction factor for sails and<br />
appendages. The total bare hull resistance was found by adding a correlation factor. Using this resistance, the<br />
Effective Horsepower (EHP) was determined over a range of speeds. The results were compared with those from<br />
the MIT method (shown in Figure 60) for validation. The MIT method includes the sail directly and other<br />
appendages using a percentage. Figure 61 shows the bare hull resistance curves.
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