5.1.2 Environmental Conditions
Sections 5.1.2.11 - 5.1.2.14

5.1.2.11 Nuclear hardening. Requirements for nuclear hardening shall be as specified herein.

5.1.2.11.1 Fully hardened. Levels of nuclear survivability shall be tailored from NAVSEA Instruction C3401.1. Requirements for air blast, thermal radiation, and free field EMP shall be tailored from NSWC TR 87-192 for exposed equipment and cables; modified to limit conducted current levels to 10A on cables that penetrate the ship's hull. Requirements for air blast induced shock, transient radiation effects on electronics (TREE), and conducted EMP shall be tailored from NSWC TR 87-192 for all equipment. EMP tests shall be tailored in accordance with the RS05 and CS10 requirements of MIL-STD-461 (see 5.1.2.3).

5.1.2.11.2 Minimal acceptance. It is the responsibility of the specifier to determine if the equipment requires nuclear hardening, and the degree of nuclear hardening. DOD Directive 4245.4 provides further guidance. Installation in a sheltered, controlled environment does not protect the equipment from all effects of a nuclear event.

5.1.2.11.3 Ruggedized techniques. With proper care, COTS equipment can be ruggedized to meet the nuclear environment. The specifier may consult NSWC TR 90-22 for techniques to harden equipment to the nuclear environment. Suggested guidelines for hardening are provided below.

(a). Air blast and thermal radiation: Appropriate shielding and insulation may be applied to protect exposed equipment.

(b). Air blast induced shock: To meet this requirement and the underwater shock requirements of MIL-S-901, equipment may be shock mounted (see 5.1.2.14 ).

(c). EMP: Appropriate electromagnetic shielding and grounding shall be used. Protection may be applied at I/O ports to prevent propagation of the EMP pulse into equipment. For small signal interfaces, terminal protection devices (TPDs) or filter pin connectors shall be used due to the fast rise time of the EMP pulse. For power circuit interfaces, metal oxide varistors (MOVs) may be applied.

(d). TREE: The ship's hull is relatively transparent to the TREE conditions. Radiation detection, power interruption and dump may be applied. With this approach, a radiation detection integrated circuit (IC) provides a signal for power supplies to momentarily turn off, and high voltage circuits and capacitors to be crow-barred (discharged to ground). A radiation detection IC is under development and will also be available as a SEM module of the Standard Hardware Acquisition & Reliability Program (SHARP) program at NWSCC, Crane, Indiana. Using this approach, any momentary component latch-ups will not result in a sustained fault of components and subsequent failure. Power supplies of COTS equipment and capacitors used to store energy would be modified to interface with the radiation detection IC. Other methods employed include component selection and component derating. Fiber optics may be sensitive to TREE conditions. Fiber optic cables shall be selected which are insensitive to TREE. 

5.1.2.12 Salt fog (spray). Requirements for salt fog (spray) shall be as specified herein.

5.1.2.12.1 Fully hardened. Equipment shall be tested in accordance with MIL- STD-810, method 509. As an alternative, equipment may be tested in accordance with IEC 68-2-11Ka, except with a duration for exposure of 48 hours.

5.1.2.12.2 Minimal acceptance. Generally, requirements for salt fog effects are not applicable. Requirements for equipment operation under salt fog effects shall be specified only for those installations determined by the specifier to be subjected to salt fog effects.

5.1.2.13 Ship motion and attitude. Requirements for ship motion and attitude shall be as specified herein.

5.1.2.13.1 Fully hardened. Equipment shall be fully operational through the ship motion and attitude conditions in accordance with DOD-STD-1399, section 301. Inclination tests shall be as specified in Appendix D.

5.1.2.13.2 Minimal acceptance. Ships motion and attitude conditions are defined in DOD-STD-1399, section 301. Under heavy weather conditions, office equipment such as duplicating machines may be permitted to shut down when the inclination exceeds a pre-specified limit.

5.1.2.14 Shock. Equipment used aboard ship is subjected to shock and vibration as a result of shipping and service conditions, as well as from hostile engagements (see 5.1.2.11.3 ). In all cases, equipment shall be designed to operate within the service environment to be encountered aboard ship. Shock tests and requirements for shipboard equipment are specified in the following documents:

(a). Functional shock: MIL-STD-810, method 516, procedures I and VI.

(b). Storage and transportation: MIL-STD-810, method 516, procedures II, III, IV, and VIII.

(c). Combat condition: MIL-S-901.

Requirements for shock testing shall be as specified herein.

5.1.2.14.1 Shock spectrum and transient duration. In order to perform shock tests, a shock spectrum and transient duration shall be defined which represent the extreme design conditions to be encountered. Where published data is not available, guidance shall be sought from COMNAVSEASYSCOM (Codes SEA-06K21 and SEA 55X12).

5.1.2.14.2 Shock Grades. Equipment is classified into grades in accordance with DOD-STD-1399, section 072.4, in order to determine the testing requirements for combat shock (see MIL-S-901). The shock grade, shock spectrum, and transient duration determine the tailoring requirements for testing.

5.1.2.14.3 Fully hardened. Equipment shall be classified as grade A and shall be in accordance with MIL-S-901 in addition to the applicable portions of MIL-STD-810, method 516.

5.1.2.14.4 Minimal acceptance. Equipment which is normally stowed for combat shall be classified as grade C with no testing requirements. All other equipment shall be classified as grade B and be tested in accordance with MIL-S-901. Note: MIL-S-901 does specify grade C.