Fine water mist is being considered as a replacement technology for fire suppression on the next generation of manned spacecraft. It offers advantages in performance, ease of cleanup, compatibility with on-board environmental systems, and ability to recharge during a mission. ADA Technologies has designed a prototype hand-held extinguisher that is being tested at ambient environmental conditions. In this SBIR program ADA Technologies proposes to advance this prototype with a new design for a reduced-momentum nozzle to generate a fine water mist that can be discharged into confined and obstructed spaces to attack hidden fires as well as open fires in manned spacecraft. In Phase I multiple nozzle concepts will be designed, fabricated, and competed to identify the most promising concepts. In addition, we will adapt a vacuum chamber at team member Colorado School of Mines to evaluate the advanced nozzles against fires in an atmosphere of 34% oxygen and 7.6 psia total pressure, representative of the conditions in manned spacecraft. These tests will validate the efficacy of Fine Water Mist at these nonstandard atmospheric conditions. Phase I products will include a comprehensive specification for a beta prototype hand-held FWM extinguisher that incorporates the best advanced reduced momentum nozzle. In Phase II we will carry the beta prototype design forward to testing in microgravity and develop a plan for flight qualification of the hardware. We will work with a partner experienced in the production and qualification of flight test fixtures and experiments. ADA will partner with a commercial supplier of fire protection equipment to take this technology into the broader commercial marketplace, targeting aerospace and flammable fuels storage as early market segments.