Vehicle Cabin Atmosphere Monitor (VCAM) identifies gases that are present in minute quantities in the International Space Station breathing air that could harm the crew's health. If successful, instruments like VCAM could accompany crewmembers during long-duration exploration missions.Principal Investigator(s)
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States
Oceaneering International, Incorporated, Houston, TX, United States
National Aeronautics and Space Administration (NASA)Sponsoring Organization
Human Exploration and Operations Mission Directorate (HEOMD)Research Benefits
Information PendingISS Expedition Duration:
March 2009 - September 2011Expeditions Assigned
19/20,23/24,25/26,27/28Previous ISS Missions
The Volatile Organic Analyzer (VOA), a similar instrument, has been used to monitor the ISS environment since Expedition 1.
To successfully live and work in the environment of the International Space Station (ISS), the environment must be monitored to ensure the health of the crewmembers. Crewmembers can be more sensitive to air pollutants because of the closed environment. Pollutants in environment are magnified on the ISS because the exposure is continuous.
VCAM can provide a means for monitoring the air within the enclosed environments, such as the ISS, Crew Exploration Vehicle (CEV), a Lunar Habitat, or another vehicle traveling to Mars. Its miniature preconcentrator, gas chromatograph (GC), and mass spectrometer can provide unbiased detection of a large number of organic species. VCAM's software can identify whether the chemicals are on a targeted list of hazardous compounds and their concentration. Its performance and reliability on orbit along with the ground teams assessment of its raw data and analysis results will validate its technology for future use and development.
VCAM pulls in air from the ISS cabin through an inlet port embedded in its front panel; the air passes through a particulate filter for analysis. Onboard software evaluates targeted compounds that need to be monitored for the crew health.
A VCAM calibration gas is used to periodically quantify how the preconcentrator, GC, and mass spectrometer are actually performing. The raw data, calibration data, and analysis results are all sent to the ground for further assessment to validate the instruments detection, identification, and quantification results.
The VCAM system is a stand-alone instrument that operates autonomously but can be commanded by either crew or ground personnel. It carries its own gas supplies for sampling operations, cleaning, and calibration. Several VCAM processors control the measurement and analysis processes, monitor housekeeping sensors and actuate the valves that control the flow of gas. Commercial backing and turbo-molecular drag pumps maintain the vacuum required to do ion-based mass spectroscopy.
VCAM is a microwave oven-sized payload which weighs less than 30 kilograms and requires 70 to 180 W of power for its operation. VCAM will be installed in an Expedite the Processing of Experiments on Space Station (EXPRESS) Rack and operate for at least twelve months; it will use the racks conditioned air for heat dissipation and its ethernet link for receiving commands from the ground and transmitting data. VCAMs front panel provides the instruments operational interface with the crew: an LED display showing the instrument status and a multi-button system for navigating its control menus; an access door enables the crew to replace the VCAM gas supply orbital replacement unit (ORU) after twelve months of nominal operations.
VCAM will protect crewmembers by informing them of the slow build up of potentially harmful chemical in their breathing air. While VCAMs library contains species that engineers know to be present in the various life-support systems, VCAM can provide data that allow ground scientists to identify compounds that were not expected. These same functions of detection, identification, and quantification can be utilized in the event of a chemical spill or release.Earth Applications
Instruments larger than VCAM monitor the air in enclosed systems on Earth (e.g., submarines). Small portable units are used in the field to monitor the environment.
VCAM will collect an air sample on average once per day. The raw data and on-board analysis, as well as housekeeping data, will be sent to the ground for assessment. VCAMs internal gas supply is sized to last for twelve months; less frequent measurements will result in slightly longer operational periods.Operational Protocols
Operational Protocols: VCAM pumps cabin air into its preconcentrator, a charcoal bed to which many of the chemicals in the air stick (adsorb). After several minutes the preconcentrator is warmed slightly to remove nitrogen, oxygen, and water; then it is heated very quickly to drive the chemicals off into a flow of pure helium gas. This puff of gas mixture flows through a 10-meter capillary with a special internal coating (gas chromatographic column) that separates the chemical families from each other over a twenty minute period. The gas is pulled into the mass spectrometer where it is ionized by an electron beam; the resulting ions are held in the Ion Trap and then ejected based upon their mass-to-charge ratio; the charged mass fractions, characteristic of the original gas, are collected by a high-voltage detector. Fifty mass spectra are collected each second and averaged; the total number of ions ejected each second (over the twenty minutes of gas flow resulting from the original puff of gas) produces a chromatogram. Software in VCAM compares these two pieces of raw data to its standard library to identify the chemical and uses the number of ions to determine the concentration is the air.
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