By Edited by: Laura Carrabine, Senior Editor
NASA uses an innovative and cost-effective unmanned aircraft to gather earth science data around the world. It was designed by the U.S. Naval Research Laboratory and developed at NASA’s Ames Research Center. The Systems Integration Evaluation Remote Research Aircraft (SIERRA) is routinely deployed for environmental collection missions over remote or inaccessible regions where harsh conditions and long flights are required.
The SIERRA has completed missions over the Arctic, lingering for hours at a time in extreme sites to collect data on the polar ice cover. It’s also flown over volcanoes to peer into active craters. NASA’s goal is to increase SIERRA’s 9-10 hour trips to obtain even more valuable information per flight. To achieve their goal, NASA decided to redesign the engine cowling to reduce drag and improve fuel economy.
The Mach-T3 team produced a CAD model using incomplete 3D optical scanning data.
NASA approached MACH-T3 Engineering to help solve this challenge. MACH-T3 specializes in 3D solid modeling, finite element analysis (FEA), and mechanical design. To accelerate the design process, MACH-T3 engineers implemented reverse engineering technologies using Rapidform XOR software by INUS Technology. The software converts 3D scans into parametric CAD models.
To design a more aerodynamic cowling, an accurate 3D CAD model was needed consisting of all engine dimensions and cowling mounting specifications. Because SIERRA’s engine is an off-the-shelf aircraft engine, NASA did not own such a model.
Traditional measurement methods for building a 3D CAD model would have been too labor-intensive. NASA engineers estimated that the process would take at least 500 hours. This method involves disassembling the engine and manually measuring each part. These measurements are then used to manually reconstruct a CAD model. Typically, multiple iterations are required in the modeling process because there will be missing or inaccurate measurements from the original parts.
MACH-T3 took a different approach. “Using a 3D laser scanner and software, we can reverse engineer equipment in a fraction of the time it takes to manually accomplish this task,” explained Bobby Machinski, owner of MACH-T3 Engineering. “Today’s 3D technology allows us to easily obtain all of the proper contours and quickly produce a CAD model for any part.”
In 2010, MACH-T3 bought Rapidform XOR software because it was one of the only products that can make parametric CAD models from 3D scan data. The software combines CAD functions with reverse engineering and scanned data handling capabilities. Because Rapidform incorporates both applications, users move from unprocessed 3D scans to complete, feature-based solid models. The software creates a model from incomplete 3D scan data. Typically, optical 3D scanners cannot pick up all data points and render a complete scan due to differences of surface texture, color, and obstructed lines of sight.
Reverse engineering software helped the Mach-T3 team redesign the Sierra aircraft’s engine cowling in record time.
“The beauty of Rapidform is that once you get enough information, you don’t need 100% of the data,” explained Machinski. “The software recognizes the geometry and allows you to extract model information, even with missing scan data. The product finds the geometric primitives automatically. This makes it easy to convert the data over to a CAD solid model, saving time and improving accuracy.”
Deviation analysis is another key feature of the software that saves time. It allows the user to quickly see deviations between the raw scan and the idealized CAD model. “This feature allows us to set tolerances as needed. We can step it up or down to find out how close we are to the ideal model versus the physical model,” Machinski continued. “The software allows us to quickly address deviations that matter to the design, ignore the ones that don’t, and produce a solid model quickly.”
Rapidform XOR software helped MACH-T3 capture the data they needed and quickly develop a CAD model. “The entire project took us 50 hours instead of 500, allowing us to achieve success in only 10% of the time it would have taken us compared to using conventional means,” concluded Machinski. “The engine model was complete, accurate, and allowed NASA to make an improved cowling design that perfectly fit around all the SIERRA engine components.”
NASA is now one step closer in their redesign of SIERRA’s cowling. Utilizing the detailed and accurate 3D CAD engine geometry to create the new aerodynamic cowling design, SIERRA will soon be conducting longer atmospheric sampling missions over volcanoes and ice reconnaissance in the Arctic.