Since the year 2000, astronauts and cosmonauts have been conducting experiments in biology, physics, astronomy and other fields on NASA’s International Space Station (ISS), which is operated by five space agencies from the U.S., the European Union, Canada, Russia, and Japan.
It is the longest running manned spacecraft, and the largest artificial body in orbit, measuring the length and width of a football field it’s about the size of a six-bedroom house and weighs 925,000 lbs. And it is, in fact, a floating laboratory that makes 15.5 orbits per day, experiencing sunrise and sunset every 92 minutes.
So, it’s no ordinary laboratory. But, it does rely on much of the same technology found on any factory floor, says Tom Basciano, Project Manager for the International Space Station at Boeing, who talked about the ISS wireless infrastructure during his keynote at last month’s Automation Conference.
The deployment of the Joint Station LAN (JSL)—a network that connects all the U.S. and international partner modules and supports communications, played a key role in transitioning the ISS program from the use of traditional aerospace manufacturing to commercial-off-the-shelf (COTS) equipment. The move to COTS was driven by the desire to reduce the cost of access to space through the use of standard industry interfaces.
“The same forces that drive day-to-day business in manufacturing drive our industrial automation,” Basciano said.
Eight miles of wire connect electrical power systems on the Space Station, including Ethernet switches from Belden and wireless access points from Moxa. As data goes through the switches it is collected at the U.S. lab and sent through custom avionics to be shipped to the ISS Ku-band system—which are like digital TV dishes—used for downlinking high rate data such as video and payload (experiment) data. The Ku-band system then sends the data to the Tracking and Data Relay Satellites (TDRS) orbiting earth, which transmit data down to the White Sands Test Facility in Houston and the Payload Operations Center in Huntsville, Alabama.
The addition of an external wireless communication (EWC) system, which Basciano was very involved in creating with the help of Moxa, enables flight controllers in Houston and Huntsville to configure and manage the network in space much in the same manner it’s done on a typical factory floor. In addition, the network allows the crew to access the Internet, get email, make phone calls via Voice Over IP (VoIP), and even conduct videoconferences with family or for the public on NASA TV.
The one issue with having a wireless network in outer space is that it only delivers 10Mbits/second, which means the data to be sent down to earth must be transmitted in pieces, with all of the sophisticated processing happening on terra firma.
The external wireless system is an important addition to the ISS communication infrastructure. And, while lowering integration costs was a primary driver of adopting industrial off-the-shelf technology for this project, reliability is even more important, Basciano said.
While some factory floors are very harsh environments, nothing really compares to space. The number one thing to factor into the equation is that the radiation environment is much harsher at ISS altitudes. Also, the thermal environment is much different on the ISS than on earth, and the external equipment can routinely experience drastic temperature changes in the 90 minute orbit that takes them from facing the sun to peering deep into dark space. Then there’s those pesky tin whiskers-- electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin is used as a final finish.
Numerous electronic system failures have been attributed to short circuits caused by tin whiskers, as well as a tin pest, a change in the crystalline structure of tin at extremely low temperatures which causes deterioration and decomposes the material into a powder.
So, there are many factors that must be considered when using COTS technology in space. NASA is cautious about what it brings onto the ISS, but large improvements in the ruggedness of industrial equipment, largely occurring in the automation and automotive industries, has gradually changed attitudes about this technology in the aerospace community, Basciano said.
NASA also studies technology on oil rigs, for example, as they look to improve equipment reliability. Because while research is important as we explore the final frontier, the safety of the crew is always the top priority—even here on earth.
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