For the past five years ADA Technologies has been developing and refining a portable fire extinguisher (PFE) for use in microgravity environments. This technology uses fine water mist (FWM) to effectively and efficiently extinguish fires that are representative of spacecraft hazards. Fine water mist offers advantages of high heat transfer rates, high heat capacity, and compatibility with crew and shipboard systems that alternative technologies do not. We have tested the technology on a wide range of representative fires including tests in a 34% O2/8 psia environment to confirm its efficacy under spacecraft conditions. However, to date we have not demonstrated the technology in a microgravity situation to confirm that our design is tolerant of this aspect of orbital flight. Such a test is a logical next step in the evolution of our FWM extinguisher. The current ADA prototype design meets a specification of less than 10 lb for the filled and fully operational device. Fire suppression is identified in the OCT roadmap Technical Area T06: “Human Health, Life Support and Habitation Systems”. In particular, section 2.4., “Environmental Monitoring, Safety, and Emergency Response (EMSER)” mentions efforts to “develop technologies to ensure crew health and safety by protecting against spacecraft hazards, and for effective response should an accident occur”. Another critical advantage of the FWM technology is its compatibility with the Multi-Use/Multi-Function Respirator System and Mask also envisioned in the TA 06 roadmap. NASA is currently evaluating the use of ADA’s FWM PFE to replace the current CO2 fire extinguisher on the International Space Station (ISS). The three primary objectives of the proposed experiments are to: (1) demonstrate that the water atomization process taking place inside the PFE and the subsequently generated water mist plume are not measurably affected under reduced gravity conditions, (2) demonstrate that water mist droplets transport through a tortuous or greatly obstructed path is more efficient in weightlessness as droplets will not tend to settle, and finally (3) measure the light obscuration due to a water mist plume dispersing in an open enclosure as this was identified as a potential concern in a manned vehicle. Two separate experiments using essentially the same setup are proposed. The two experiments would be performed on different days to allow for adjustment of the apparatus and refilling of the prototype extinguishers. In the first experiment, ADA’s PFE FWM will be discharged inside an enclosure across the path a laser beam of a Malvern Spraytec instrument in order to measure droplet size distribution (DSD) upon discharge. ADA has an extensive database of measurements made in the laboratory with the Malvern instrument to which the flight measurements will be compared. Light obscuration due to the mist dispersion in the back section of the enclosure will also be measured. In the second experiment baffles will be installed inside the enclosure, spanning most of its length to form a space representative of experiment racks used on the ISS. The prototype PFE will be discharged into this space, and the migration of mist throughout the obstructed volume will be characterized. In this experiment, we will as above discharge the PFE, then measure the obscuration due to water mist in two locations downstream of the obstructing baffles for the remaining near-zero-g time. The proposed project team includes ADA Technologies and our subcontractor the Colorado School of Mines (CSM) along with the National Center for Space Exploration Research at NASA’s Glenn Research Center. The CSM and NASA participants have experience on zero-G aircraft, and will apply their expertise to the detailed design of hardware and experimental protocol development for the project. We believe the team and technology make this project a strong candidate for successful execution on board the zero-gravity aircraft.