Validation of a Fine Water Mist Fire Extinguisher
PI: Thierry Carriere, ADA Technologies
PI: Thierry Carriere, ADA Technologies
With funding from the NASA SBIR program, ADA Technologies, Inc. has been advancing a design for a Fine Water Mist (FWM) portable fire extinguisher (PFE) that meets the performance requirements of operation in a microgravity environment and effective fire extinguishment of hazards typical of manned spacecraft. A series of tests run in 2008 showed that the ADA beta prototype configuration was capable of extinguishing 90% of test fires with less than one pound of fine water mist. In 2009, ADA designed, fabricated and delivered to Jacobs Technology an advanced prototype that incorporated multiple features deemed essential to operation in manned spacecraft. Continued development of a prototype portable FWM extinguisher via an ADA Phase II SBIR project offers NASA the opportunity to substantially advance this technology toward implementation on the next generation of manned spacecraft in a very efficient use of resources.
- TA06 Human Health, Life Support and Habitation Systems
The portable fire extinguisher (PFE) technology 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.
We believe that two fundamental technical aspects of the PFE need to be validated in microgravity. First, characterization of the droplet size distribution (DSD) generated in a microgravity environment will allow the validation of fire suppression performance by demonstrating that microgravity does not impact to a measurable degree the water atomization mechanism and in turn the droplet size distribution generated in the ADA prototype PFE. Secondly, the efficient transport of water mist droplets through an obstructed space needs to be observed and confirmed. Efficient transport will enable the droplets to reach and cool the fire, as well as reduce oxygen fraction (inerting) in the region. Both these experiments will provide data to confirm that the ADA FWM technology is applicable and operational in the microgravity of space, which will advance the TRL of our device to a level of 7, Prototype Demonstration in an Operational Environment.
The ADA FWM portable fire extinguisher has immediate application to multiple NASA missions: it is proposed for replacement of the existing CO2 portable extinguisher used on ISS and can provide high-quality fire protection for the multiple candidate vehicles now being advanced under NASA’s Commercial Crew Development Program. Once FWM technology has been validated in a zero-gravity environment, it will also be a leading candidate for use in commercial suborbital vehicles now being developed by organizations such as Virgin Galactic, Sierra Nevada and Space-X.
In the first experiment, ADA’s PFE FWM will be discharged inside an enclosure across the path of 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. 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.
The main experiment item will be an enclosure of dimensions: 183 x 122 x 92 cm (72 x 48 x 36 inch). These dimensions are such that a Malvern Spraytec instrument, measuring droplet size distribution, can be installed inside. The width of the enclosure is above 100 cm because the mist discharge needs to first go through the Malvern beam (first 30 cm of the enclosure width) and then disperse for at least 90 cm or about 3 feet to replicate the loss of visibility that may be experienced in an open cabin environment.
In the first experiment, the mean droplet diameter values were very similar to ground data acquired prior to the flight. These data support a conclusion that the droplet size distribution measured in microgravity is not different from the same measurement on Earth.
In the second experiment conducted in an obstructed test fixture, the data showed that the mist flowing around an obstruction was found to consist of substantially smaller mean diameters, both in the micro-g and 1-g environments. This is logical, as the larger droplets would be expected to have sufficient momentum to impact against the obstruction plate and be removed from the mist plume.
A delay in measurements was also observed, due to the time required for the mist to propagate around the obstruction into the main volume of the test fixture. In the obstructed discharge experiment measurements were made of the transmission of a laser source through the fine water mist accumulated in the test fixture during discharges. In micro-g discharges, the laser beams were obscured more strongly than on the ground. At the end of the 10 s discharges, on average, the micro-g experiments allowed 40% light transmission (equal to 60% blockage of the light by water mist) compared to about 70% transmission (30% blockage) on the ground. The light scattering by the fine water mist plume was therefore doubled in micro-g compared to ground. This significant difference indicated that water mist droplets, initially the same size as shown in Malvern measurements, were able to travel around an obstacle in twice the number in the Zero-g experiments compared to the 1-g experiments. This is an important finding for the overall microgravity fire extinguisher development program as fire suppression experiments to validate the technology have been performed in 1-g, suggesting that testing to date represents a worst-case condition compared to PFE operation in a microgravity environment.
Selection DateAFO1 (May 2011)
Program StatusTesting Complete
Current TRL (?)TRL 7
- 1 Parabolic