LIFE SUPPORT AND ENVIRONMENTAL CONTROL[]
Of all major ship's systems, life support and environmental control are among the most critical. Every key system element is designed with multiple redundancy to provide for maximum crew safety, even in the unlikely event of multiple system failure. Under normal operating conditions, the mean time between failure for the environmental systems should exceed five hundred operating years. Even under such a total failure, emergency backups should insure crew survival in most situations.
Major life support equipment facilities are located in the Primary Hull on Deck 2. The primary life support systems comprise two parallel systems, each serving as a backup to the other. Synthetic gravity generators are located throughout the habitable volume of the spacecraft. Each major life support facility includes a tie-in to the reserve utilities distribution networks. These tie-ins include a limited supply of critical consumables, including breathable air, power supply, and water.
The reserve utilities distribution network is designed to provide minimal life support and power in the event of complete disruption of both primary environmental support systems. Other emergency provisions include distributed reserve life support systems, emergency support shelter areas, and contingency support modules intended to provide ship wide breathable atmosphere for up to thirty minutes in a major system wide failure.
ATMOSPHERIC SYSTEM[]
The USS Solstice environmental system maintains a Class M compatible oxygen-nitrogen atmosphere throughout the habitable volume of the spacecraft. Two independent primary atmospheric plenum systems deliver temperature and humidity controlled environmental gases throughout the vehicle. Additionally, a separate reserve system and emergency systems provide additional redundancy.
Atmospheric processing units for the primary system are located throughout the spacecraft at the rate of approximately two redundant primary units for every 50 m3 of habitable ship's volume. These devices maintain a comfortable, breathable mixture by removing CO2 and other waste gases and particulates, then replenishing the O2 partial pressure. This is principally accomplished through the use of photosynthetic bioprocessing. The atmospheric processors also maintain temperature and humidity within prescribed limits. Once so processed, the breathing mixture is recirculated through the plenum network.
Cruise Mode operational rules specify a ninety-six-hour duty cycle for processing modules, although normal time between scheduled maintenance is approximately two thousand operating hours. At the end of each ninety-six-hour duty cycle, it is normal for the entire atmospheric processing load to be automatically switched to the alternate primary system.
It is, however, possible to individually switch specific system elements as needed. Atmospheric plenum flow can be remotely switched at utilities junction nodes, so that breathing atmosphere can be rerouted to processors at other locations, offering an additional measure of redundancy.
The reserve system is a third redundant set of atmospheric processors, providing up to 50% of nominal system capacity for periods up to twenty-four hours, depending on system load. These are intended for use in the event of incapacity of major elements of the two primary atmospheric
The reserve system shares the plenum network of the two primary systems, and operates by computerized system analysis, which allows any damaged plenum sections or processors to be isolated and removed from service.
Additionally, emergency atmospheric supply systems provide breathing mixture to designated shelter areas for up to thirty-six hours in crisis situations. These systems draw on independent oxygen and power supplies, physically isolated from the primary systems and from each other. The emergency systems are not intended to provide shipwide atmospheric supply. The emergency atmospheric supply systems provide minimal recycling capacity (CO2 scrubbing and O2 replenishment only), but oxygen supply can be significantly extended by drawing on any available supplies from the three primary systems, or from any unused contingency supply modules.
In case of major failure of atmospheric supply necessitating use of the emergency system, contingency atmospheric supply modules, located at most corridor junctions, will maintain a breathable environment for approximately thirty minutes, sufficient for the crew to evacuate to shelters. Environmental suits would be provided to all personnel required to work in areas in which a breathable atmosphere is not maintained. Except in cases of large-scale explosive decompression, even a severe atmospheric supply failure is expected to permit upward of fifty minutes for evacuation of all personnel to designated shelter areas.
Nominal atmospheric values for Class M compatible conditions (per SFRA-standard 102.19) are 26°C, 45% relative humidity, with pressure maintained at 101 kilopascals (760 mmHg). Atmospheric composition is maintained at 78% nitrogen, 21% oxygen, 1% trace gases. Approximately ten percent of living accommodations can be switched to Class H, K, or L environmental conditions without major hardware swapout. An additional 2% of living accommodations are equipped for Class N and N(2) conditions. Atmospheric processing modules can be replaced at major starbase layover to permit vehicle wide adaptation to Class H, K, or L environmental conditions.
EMERGENCY ENVIRONMENTAL SYSTEMS[]
The basic design philosophy of the Starfleet environmental support systems is for extreme reliability coupled with multiple redundancy. Nevertheless, Starfleet recognizes the unknown hazards to which starships and their crews are often exposed, and has provided yet another layer of preparedness for potential environmental crisis situations.
The purpose of these emergency environmental support systems is to provide suitable life support for the crew for periods of time sufficient for the Engineering staff to restore normal function to either primary system or to the reserve system. The first element of this is an emergency backup system designed to provide shipwide lighting and atmospheric supply for approximately thirty minutes. This is intended to allow an orderly evacuation of all ship's personnel to emergency support shelters. These shelters are the second element of the emergency environmental support system.
CONTINGENCY ATMOSPHERIC AND POWER SUPPLY[]
Supplementing the two redundant primary atmospheric support systems and reserve backup system is the contingency atmospheric and power supply system. This system consists of 425 self-contained air supply and power modules located throughout the ship at many corridor junctions. The principal elements of these modules include ventilation fans, cryogenic oxygen storage, CO2 scrubbers, emergency lights, and batteries. In the event of a total failure of all primary and reserve systems, these units provide approximately thirty minutes of atmosphere and lighting throughout the ship, allowing all personnel to take sanctuary in designated environmental support shelters.