Aerospace Industry The ENose mimics a mammalian nose to “smell” leaks or spills of chemical species on board space stations
NASA developed a supersensitive sensor that mimics a mammalian nose to “smell” leaks or spills of analytes (chemical species) on board space stations. Called a JPL Electronic Nose or ENose, the autonomous device, which requires minimal crew interfacing, monitors the quality of the recycled air in the space station by continuously sampling air and documenting events where potentially trained-for chemical substances have been released. By training, it means that the sensors are exposed to the target analytes under various conditions. Data from that training is used to construct the data library. The ENose can also sense when an electrical fire breaks out through the increasing heat that releases a variety of signature molecules. Since it is thus, the ENose “fills the long-standing gap between on-board alarms and complex analytical instruments“, according to NASA. The developers explained that while the device can detect the presence of a small group of chemicals, which could be dangerous if they are present in the air, it is not designed to analyse everything in the air. A PDA, laptop computer or interface unit are used to record and analyse data in real-time. The sensor unit consists of an anodised aluminium chassis, which houses the sensor array and pneumatic system. It also contains the electronics to route power, relay data and commands between the sensor array and the ENose interface unit. For it to work, the ENose uses an array of 16 different polymer films, which are designed to conduct electricity. When a substance is absorbed into these films, the films expand slightly, and that changes how much electricity they conduct. Each of these films reacts differently to each substance or analyte. Some of the polymers used for the ENose sensors include nylon, PE, PVC, and polyvinyl alcohol (PVA). NASA selected polymers that respond to targets and make them conductive by adding carbon, thus ensuring that the sensors have a longer lifespan. The first generation JPL ENose flew on the Space Shuttle STS-95 in 1998. Development of the third generation device is underway, NASA said. It is being made especially for use in the International Space Station (ISS). It has the same basic sensor design as the first generation but the developers have found ways to make the polymers more sensitive than the ones used in the earlier model.
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MAY 2016
Propylene, a lunar element When the Cassini spacecraft, launched in October 1997, embarked on a seven-year Cassini-Huygens mission to the ringed planet Saturn, it not only uncovered two new moons, Methone and Pallene, but also discovered a chemical on Saturn’s largest moon, Titan, that is used in plastics for packaging and household applications here on Earth. Cassini detected a small amount of the monomer propylene, which is used to make PP, in Titan's lower atmosphere through the Composite Infrared Spectrometer (CIRS). This instrument measures the infrared light, or heat radiation, emitted from Saturn and its moons in much the same way our hands feel the warmth of a fire. CIRS can identify a particular gas glowing in the lower layers of the atmosphere from its unique thermal fingerprint. The challenge is to isolate this one signature from the signals of all other gases around it. NASA's Voyager 1 spacecraft, which made the firstever close flyby of Titan in 1980, was able to identify many of the gases in the moon’s hazy brownish atmosphere as hydrocarbons, the chemicals that primarily make up petroleum and other fossil fuels found on Earth. On Titan, hydrocarbons form after sunlight breaks apart methane, the second-most plentiful gas in that atmosphere. The newly freed fragments can link up to form chains with two, three or more carbons. The family of chemicals with two carbons includes the flammable gas ethane. Propane, a common fuel for portable stoves, belongs to the three-carbon family. Voyager detected all of the one and two-carbon families in Titan's atmosphere. From the three-carbon family, the spacecraft found propane, the heaviest member, and propyne, one of the lightest members. But the middle chemicals, one of which is propylene, remained elusive. The Cassini spacecraft discovered amounts of plastic chemical propylene in Titan's lower atmosphere
As researchers continued to discover more chemicals in Titan's atmosphere using ground and space-based instruments, propylene was finally found as a result of more detailed analysis of the CIRS data, leading to a Eureka moment! Thus, this opens up a whole new horizon for plastic materials in space.