May 30, 2013
Seeing Doubles: APL Develops Body Models for Airport Security Tests
The Transportation Security Administration (TSA) deployed state-of-the-art advanced imaging technology in 2007 to detect a wide range of threats that might affect transportation security. APL scientists and engineers recently created static, human-like models for TSA that are designed to mimic the body during testing of two types of advanced imaging technology used at airports.
Called Body Phantoms, the models were developed for a laboratory-testing environment and designed so that TSA could perform complex, high-repetition tests using scanners and simulated threats on a fixed background. Tests using live threats are not always practical or safe to perform on real humans, so the Body Phantom was a needed and ideal solution.
TSA’s primary task of responding to evolving security threats means that APL’s approach must also be nimble and quick to respond. Fabricating the Phantoms in a very tight time frame was a key challenge for APL engineers and scientists, who accomplished it by using additive manufacturing combined with specially formulated materials. Additive manufacturing, also called rapid prototyping using 3-D printing, is a process of making solid objects directly from a digital model. The 3-D prints are made using additive processes that create an object by laying down successive layers of material; this differs from traditional machining techniques, which rely mainly on the removal of material by methods such as cutting and drilling.
“We knew we could fabricate something like the Body Phantom,” says Bob Matteson, of the Research and Exploratory Development Department’s Engineered Materials and Fabrication Group. Although the group had never fabricated a life-sized body, it had done similar work fabricating a multifaceted human torso. “So we knew we had the scientific expertise and background to make this happen,” says Matteson.
The human surrogate head model and torso are more complex because they include individual simulated organs with specified mechanical properties.
The team turned to additive manufacturing to meet TSA’s intense schedule requirements. “Additive manufacturing allows us to be very agile in our design and our approach to fabrication,” says Matteson. In combination with state-of-the-art materials, additive manufacturing also speeds things up by allowing engineers to omit steps needed in traditional modeling and casting processes. “The real beauty of additive manufacturing is that the turnaround to produce a full-scale part is about a week—no molds, no casting processes,” says Matteson. “This was significant because our entire time frame was less than six months from requirements to delivery.”
TSA uses two very different types of scanners—one that uses X-ray backscatter technology and another that uses active millimeter wave. APL scientists and engineers had to explore a variety of approaches to best fabricate a model that would be effective for both scanners. Both types of imaging technology are integral to TSA’s effort to continually ensure that travel remains safe and secure by staying ahead of evolving threats. Currently, there are approximately 800 imaging technology units at more than 200 airports.
APL’s Jane Spicer and Megan Leahy-Hoppa, both project managers in REDD’s Experimental and Computational Physics Group, also helped define the materials needed for fabrication of the Phantom. After deciding on materials and selecting a company to customize them to APL-developed requirements, the team focused on solutions for the actual fabrication of the body. “We’re very much a brainstorming group,” says Paul Biermann, of the Engineered Materials and Fabrication Group, who led the materials selection process. “We put a laundry list of possibilities together and then shot them down, one by one.”
The key challenge was to obtain an actual human form to compare with the model because different humans show up differently in different machines. Essentially, the team needed to reverse-engineer a human form to ensure that the Phantom was suitably lifelike. “We found a volunteer to be our model, and we scanned her completely at an outside facility so that we could get a full-body 3-D scan,” says project manager Jacob Boon, of the Asymmetric Operations Department.
With both a Body Phantom and a human model that could be tested side by side, the team was able to see how closely they emulate each other. “Now, we have taken the project one step further and enabled TSA to validate one against the other—an added plus neither of us anticipated,” Boon says.