Patented NASA Technology Enables Real-Time View of Objects Under Stress
Imagine wind turbine blades that can automatically adjust their shape in real time to produce more energy. Or imagine aircraft wings that can stiffen when an aircraft experiences turbulence to save fuel and improve the ride for passengers. At present, the shape of these structures can’t be measured in real time and therefore can't adapt to these types of changes in their environment.
Or, imagine civil engineers being able to immediately see and record precise bridge movements along a bridge's braces and spans. Future incidents like the 2007 Interstate 35W eight-lane bridge collapse in Minneapolis, Minn., might be avoided.
These and other such advances are now possible because of a new technology patented by engineers at NASA’s Dryden Flight Research Center.
The recently patented fiber optic-based sensor technology provides a way to easily sense the shape of real world structures in real time.
"It's gratifying to see this patent awarded, which means we can take the next step toward licensing and commercialization so that the technology can be used in the marketplace," says Dryden engineer Lance Richards, who co-authored the patent application with Dryden's William Ko. "We just want to see this technology used and people benefiting from it."
"This is an exciting opportunity for us to have a patent with such a broad range of potential benefits for the public," said Greg Poteat, Dryden's new technology officer.
"This technology is unique for us in that it can be used commercially, such as in structural safety applications, in a way that Dryden's flight research-specific technology traditionally hasn't," Poteat said. "Our technology transfer office will also be initiating a marketing activity to look for commercial companies who may be interested in licensing the technology."
The shape sensing technology moved from years of laboratory development and testing to large-scale, dynamic field testing in 2008 when it was flown on Dryden's Ikhana remotely piloted aircraft to measure the change in the aircraft's wing shape real time in flight. The effort represented one of the first comprehensive flight validations of fiber optic sensor technology.
In application, a long, hair-thin fiber optic strand is attached to a structure, like the Ikhana's wings. Every quarter-inch along the fiber, a sensor instantaneously feeds back the strain and shape of the structure to a computer. The result is a complete, as-it-happens look at every twist and turn of the structure from literally hundreds of sensors along a single strand of optical fiber attached to it.
"In addition to aerospace applications like some we've tested, the sensors can also be used to look at the stress of other structures, like bridges and dams, and possibilities extend to biomedical uses as well. The applications of this technology are mind-boggling," Richards said.
It's an incredible amount of data, and it doesn't get lost in electronic noise; it all gets displayed in colorful computer graphics fed back to a control system. NASA engineers can measure strain, temperature, and displacement changes with it.
The patented technology can be used on wings as well as other complex structures such as re-entry vehicles. For example, NASA is looking at using this technology behind the Constellation Program's Orion capsule heat shield in order to see exactly where strain, temperature and structural deformations are occurring even as the capsules re-enter Earth's atmosphere.
"Generations of aircraft and spacecraft could benefit from work with the new sensors since the sensors have performed well, both in the laboratory and now in flight," said Richards.
The weight reduction that fiber optic sensors would make possible could reduce operating costs and improve fuel efficiency of aircraft.
The development also opens up new opportunities and applications that would not be achievable with conventional technology. For example, the new sensors could enable adaptive wing-shape control.
"The sensors on Ikhana are imperceptibly small because they're located on fibers approximately the diameter of a human hair," Richards explained. "You can get the information you need from the thousands of sensors on a few fibers without the weight and complexity of conventional sensors. Strain gauges, for example, require three copper lead wires for every sensor and are significantly heavier than optical fiber."
When using the fiber optic sensors, researchers do not require analytical models for determining strain and other measurements because data derived with the sensors include the actual measurements being sought.
Intelligent flight control software technology now being developed can incorporate structural monitoring data from the fiber optic sensors to compensate for stresses on the airframe, helping prevent situations that might otherwise result in a loss of flight control.
By extension, the application of the technology to wind turbines could improve their performance by making their blades more efficient. "An improvement of only a few percent equals a huge economic benefit," Richards said.
NASA's Aeronautics Research Mission Directorate funded algorithm and systems development, instrument and ground test validation of the new sensor system.
NASA Dryden Flight Research Center