Dust and Aerosol Measurement Feasibility Test (DAFT) - 07.15.15
The Dust Aerosol Measurement Feasibility Test (DAFT) releases particles in the International Space Station (ISS) atmosphere to test the ability of different equipment to measure the levels of dust and air quality. Science Results for Everyone
Little is known about the size of soot particles in space, which makes it hard to design accurate fire detectors for spacecraft. This experiment measured particle sizes aboard International Space Station (ISS) and tested a hand-held commercial detector. Data indicated low levels of particulate in ISS relative to Shuttles – not surprising given ISS’s smaller crew size and its filtration system. Results show average particle sizes are larger on orbit than on Earth, perhaps due to inefficiency of the spacecraft’s filter. Knowing the median particulate level throughout ISS will help design better smoke detectors capable of distinguishing normal dust from dangerous smoke particles. Experiment Details
David L. Urban, Ph.D., Glenn Research Center, Cleveland, OH, United States
Thomas Cleary, National Institute of Standards and Technology, Gaithersburg, MD, United States
George Mulholland, University of Maryland, College Park, MD, United States
Jiann Yang, National Institute for Standards and Technology, Gaithersburg, MD, United States
Zeng-guang Yuan, Glenn Research Center, Cleveland, OH, United States
ZIN Technologies Incorporated, Cleveland, OH, United States
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration
October 2004 - September 2006
Previous ISS Missions
The P-Trak and DustTrak were first tested on ISS Expedition 10.
- Requirements defined for smoke detectors in spacecraft have varied significantly, because little is known about the size distribution of particles (soot) from fires in space.
- Accurate fire detection requires being able to distinguish dust particles from soot particles, and being able to detect smoke particles of the appropriate size.
- This experiment will provide the first systematic measurements of the sizes of particles in the air aboard ISS over time and prove the usefulness of the P-Trak Ultrafine Particle Counter (a small hand held commercial device).
- If successful, the detector will be used in the Smoke and Aerosol Measuring Experiment (SAME). DAFT is the first step for the development of an Advanced Fire Detection System for use on future space exploration missions.
Our understanding of how fires burn in a spacecraft has evolved since the fire detection equipment on space shuttle and space station was developed. One thing we have learned is that smoke particles that form in microgravity can be larger than those formed on Earth. Since smoke detectors are gauged to detect certain sizes of particles, this knowledge could help design more accurate smoke detectors for future spacecraft. The Smoke and Aerosol Measurement Experiment (SAME) is planned to gather particulate size information on ISS. The DAFT experiment, which was initiated after the Columbia accident, is to be used to obtain data in preparation for SAME using very little upmass.
DAFT is intended to assess and characterize the distribution of particles in the air inside ISS to allow assessment of the suitability of current shuttle and ISS smoke detectors. This experiment was begun on Expedition 10 and is planned for completion during Expedition 13. DAFT is designed to test the effectiveness of the PTrak Ultrafine Particle Counter, a device that counts ultra-fine dust particles in a microgravity environment. Most particle counters work by using a laser to record instances when the beam is interrupted; however, this method will not record ultra-fine particles that are much smaller than the wavelength of the light. P-Trak works by passing dust-laden air through a chamber of vaporous isopropyl alcohol. When a droplet of alcohol condenses over an ultra-fine dust particle, the particle becomes large enough to break the light beam and be counted. The alcohol is then recycled as it condenses on sidewalls and gravity pulls the alcohol back to the saturator. If the results are satisfactory, P-Trak will be used in SAME, which requires counts of particles ranging from 0.2-1 micron.
Extended duration space flight missions with larger vessels will require fire detection systems with increased reliability and sensitivity. In order to provide the data required for that development, SAME needs to utilize the DAFT experiment to provide mitigation against the risk that the P-Trak may not be able to provide the required data.
Additionally, in the event that the experiment is successful, it may be possible to use these devices to provide more detailed information about the character of the particulate in the atmosphere aboard the ISS.
The smoke detectors developed from the results of SAME can also be useful in other extreme environments on Earth, such as submarines or underwater laboratories. Accurate detection of smoke in these environments can save lives.
Since they have no external power requirements, DAFT-1 and DAFT-2 can be operated almost anywhere (where the release of small amounts of alcohol is permitted) within the ISS. Downlinking is performed using a program supplied by the project and installed onto an EXPRESS computer. Three test points can be accomplished by a single crew member in 80 minutes.
DAFT-3 and DAFT-4 needs ISS gaseous nitrogen and therefore require an active nitrogen source, and safety restraint for the fill device. Test point time increases by 15 minutes per point.
The crew member simply assembles the test set up from the included packages, turns the devices on and waits 6 minutes for operation, noting average readings and/or anomalies. Sensitivity to the alcohol content of the atmosphere on board the ISS limits usage of the P-Trak to a maximum of three test points per day. For DAFT-3 and DAFT-4 precautions regarding overfilling the sample bag and preventing potential hose whip exist.
Preliminary results, based on DAFT sessions performed on ISS in 2005 and 2006, demonstrated that the P-Trak Ultrafine Particle Counter could be successfully built into the SAME payload, and established the optimal ranges for particle detection using this instrument. The data collected also indicate very low levels of particulate in the ISS environment relative to that previously measured on Shuttle. This low particulate level is not surprising due to the small crew size on ISS (two or three vs. the typical seven-person crew on shuttle) and the High-Efficiency Particular Accumulator (HEPA) filtration system of ISS. It is suspected that the particulate level will rise once station hosts a larger crew. In later experiment runs, the results indicated that the average size of the particles were larger on orbit than on Earth. These results could be due to the inefficiency of the large particle filter. Once the median particulate level throughout ISS is known, it can be used to design future smoke detectors that accurately distinguish normal dust from the presence of dangerous smoke particles.
A series of events (malfunction of the electronic data transmitted, crew time limits, and an alcohol wick that did not open) shortened the overall experiment, but adequate data was collected to label the demonstration successful.
Results will be used to develop better smoke detectors for use during future space missions(Urban et al. 2005).^ back to top
Ruff GA, Urban DL, King MK. A Research Plan for Fire Prevention, Detection, and Suppression in Crewed Exploration Systems. 43rd Aerospace Sciences Meeting and Exhibit, Reno, NV; 2005
Urban DL, Ruff GA, Yuan Z, Cleary T, Griffin DW, Yang J, Mulholland G. Detection of Smoke from Microgravity Fires. SAE Technical Paper. 2005; 2005-01-2930: 10 pp. DOI: 10.4271/2005-01-2930.
Ground Based Results Publications
Microgravity Science Combustion
P-Trak a device that counts ultra-fine dust particles. Image courtesy of Glenn Research Center.
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Dust Trak is a particle counter that uses a sensor to read the percentage of light being blocked.
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Video screen shot of ISS Commander and Science Officer, Leroy Chiao, performing DAFT operations on ISS during Expedition 10. Image courtesy of Glenn Research Center.
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This image shows two particle counters that are attached to a silver bag containing dust. The bag contains a well-characterized standard dust sample called "Arizona Road Dust". Image courtesy of Glenn Research Center.
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NASA Image: ISS013E69250 - Astronaut Jeffrey N. Williams, Expedition 13 NASA space station science officer and flight engineer, works with the dust and aerosol measurement feasibility test (DAFT) in the Destiny laboratory of the International Space Station.
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