One of the primary safety concerns for Space Station Freedom pressurized modules is fire. Some Freedom modules are unattended for long periods of time. In other cases, enclosed, pressurized volumes are not open to crew monitoring. As a result, a fire detection system is required to continuously monitor all modules for combustion.
This paper briefly reviews the overall design for the Freedom fire detection system, and the design of the two basic types of detectors: smoke and flame. The smoke detectors monitor particulates in small open areas, stand-offs, end-cones, and racks. The flame detectors survey open areas for radiation at wavelengths and intensities characteristic of combustion. Responses from detectors are evaluated by Freedom's data management system to determine the presence of combustion and to recommend appropriate action. The combination of discrete detectors and centralized processing produces a flexible fire detection system which can adapt to an evolving Space Station Freedom design or to other enclosed environments.
This paper then focuses on the design, development, and testing of the flame detector. The flame detector monitors for radiation in three specific ranges of the spectrum: in a narrow band in the ultraviolet, in the visible, and in a broad band in the infrared. The ultraviolet and infrared ranges are characteristic of combustion. The visible range provides a measure of the background and is used as a discriminator to minimize false alarms. The detector provides analog outputs which are functions of the total energy received in each of these ranges. The detector also monitors for flicker, another characteristic of combustion. The design and development of the flame detector are discussed in detail. Final data from the flame detector development test are presented and discussed.