Environmental Systems - Part One

Of all major ship's systems, life support and environmental control are among the most critical. Arguably, the most important task aboard any starship is the maintaining of a stable artificial environment. Every essential 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. The proper setting-up and up-keep of a closed life-cycle (such as aboard a starship) is complex, involving equipment and facilities throughout the vessel, and equally wide-ranging in functions.

Major life support equipment facilities are located in the Primary Hull on Decks 5, 7, and 9. In the Engineering Hull, major life support equipment is located on Decks 12, 15, and 20. The primary life support systems comprise two parallel systems, each serving as a backup to the other.

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, end wafer. 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 shipwide breathable atmosphere for up to thirty minutes in a major systemwide failure.

The USS Matrix 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, separate reserve system and emergency systems provide additional redundancy.

The function of the Atmospheric Recycling System is to recycle the ship's air supply: circulating it, converting carbon dioxide to oxygen, removing contaminants, and conditioning. With a rated capacity of 5500 cubic meters, one unit usually processes 3-6 smaller decks. In the case of larger decks, three to five ARS units operate in tandem. Hangar Bays (and the Carrier Bays) have their own ARS units, coupled to a high-pressure storage tank system. This allows the bay to be pressurized and depressurized without additional load upon other units. Atmospheric processing units for the primary systems are located throughout the spacecraft at the rate of approximately two redundant primary units for every 50 m2 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 using 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. ARS units are comprised of four chambers, strung together via insulated interconnecting ducts, with various
support machinery and sensing devices incorporated.

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 systems. 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.

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 lay over to permit vehiclewide adaptation to Class H, K, or L environmental conditions.

Bibliography-

Star Trek The Next Generation Technical Manual – by R. Sternback and M. Okuda
Starfleet Dynamics - John David Schmidt

Author – Chief Engineer Lt. Wayne N Snyder
Date: September 6, 1998