Investigating the feasibility of a modulated diode laser for crewed spacecraft fire detection.

摘要

One of these risks associated with human spaceflight is the danger of fire in the manned spacecraft environment. One promising technology for providing fire detection capabilities on long duration space missions is a device in early stages of development that utilizes diode lasers to detect the concentration of target gases in the environment. The Modulated Laser Analyzer for Combustion Products (MLA-CP), developed under a contract from the NASA-Johnson Space Center, was evaluated in part by this thesis work to assess its potential for further development.; The MLA-CP was designed by SouthWest Sciences to detect the concentrations of CO2, CO, HCCH and HCN flowed through its Herriott Cell. However, during the first phase of testing, the results indicated that the MLA-CP was prone to substantial error. The majority of this error was deduced to be due to etalons within the laser hardware.; The etalons inherent to the specific laser used by the MLA-CP have proven to be a hindrance to the performance of the device. Ambient air temperature changes affecting the laser temperature over the course of a day led to substantial error. These ambient temperature changes affected the laser etalon, and were not reduced in magnitude by characterizing the etalon on device start-up. However, the short term tests conducted with UHP N2, 1% CO 2 and 10 ppm HCCH indicated that with proper calibration the MLA-CP was capable of accurately and quickly determining the concentrations of these target gases. (Abstract shortened by UMI.)