NASA to Launch RFID Test to Track Crewmember Supplies

By Mary Catherine O'Connor

June 4, 2007—For crewmembers at the International Space Station, seemingly simple tasks such as changing clothes or brushing teeth can be time-consuming chores. Without gravity, clothing and personal hygiene items float around—as do the crewmembers themselves.

Such conditions also make taking stock of inventory another time-sucking task. Each crewmember must periodically perform an audit of his or her possessions—uniforms, toiletry items, etc.—so that NASA's inventory managers back on Earth can check the supply of these goods and determine which need to be restocked for the next mission. But zero gravity means there's no easy way for each crewmember to dump the contents of his or her personal duffle bag onto a table and sort them out. Instead, he or she must place all items in a second bag and then return each to the original bag, while listing the type and quantity. This process can take up to 30 minutes for each crewmember, says Amy Schellhase, cargo integration manager with Barrios Technology, the aerospace engineering and technology services firm that NASA has contracted to test an RFID technology solution to replace this manual system.

Schellhase and Tim Brown, a NASA integrated data systems manager, say the space agency had previously considered attaching RFID tags to the individual items in each crewmember's bag so that manual counting could be replaced by a quick wave of an RFID reader over the bag. It had also hoped RFID could replace the bar code system NASA uses for tracking spare parts and other high-value, mission-critical hardware in the space station. But after collaborating with a university research group a couple of years ago, tests showed interference from the metallic and liquid materials contained in the items NASA wanted to track made the tags they were testing—passive RFID tags comprised of a silicon chip and antenna and operating in the UHF read range—too unreliable. And the cost and size of more robust, active tags would make them impractical for tracking consumables.

The project, therefore, was put on hold until Brown says he "ran across RF SAW, and their claim to fame was that [the tags] would work around metal and water." RF SAW is a Dallas-based firm that manufactures RFID tags that employ surface acoustic wave (SAW) technology. Instead of a silicon chip, SAW tags contain a piezoelectric crystal, which—like the IC in a silicon-based tag—is connected to an antenna that receives an interrogator's RF signal and transmits a return signal. The SAW tag, however, has a transducer that converts the inbound RF signal into an acoustic one, which travels along the surface of the crystal. The transducer then converts the acoustic signal back to RF before transmitting the tag's data to the reader.