Imagine trying to photograph wind. That's similar to what NASA engineers dealt with during a recent effort to study how air moves around planes, rockets, and other kinds of aerospace vehicles. Air is invisible, but our understanding of how it flows is crucial for building better, safer aircraft.
For 80 years, researchers used a technique called "focused schlieren imaging." Think of it as a special camera system that can "see" air movement by detecting tiny changes in its density. It's the same effect that lets you to see heat waves rising from hot pavement on a sunny day ¾ just much more precise.
The Self-Aligned Focusing Schlieren (SAFS) system is a game-changer. It's a compact, low-cost, easy-to-use visualization tool that is less complex than traditional focusing schlieren systems.
"What makes this breakthrough compelling is the ripple effect," said NASA's Brett Bathel, who invented the SAFS alongside fellow engineer Joshua Weisberger at the agency's Langley Research Center in Hampton, Virginia. "When researchers can see and understand air movement in ways that were previously difficult to achieve, it leads to better aircraft designs and safer flights for everyone."
Switching from older systems to SAFS in wind tunnels and other specialized research environments allows aerospace engineers to gather high-speed flow visualization data more efficiently, with less facility downtime, and lower costs. For the aviation industry, it opens doors to new discoveries, potentially revolutionizing how we design everything from commercial airliners to spacecraft.
With SAFS in its toolbox, NASA is also better positioned to meet its mission goals related to efficiency and safety in aviation and space. Researchers are using SAFS to capture flow separation on the High Lift Common Research Model, a tool for improving how accurately we can predict the takeoff and landing performance of new aircraft. And it's helping them investigate shock cell structures ¾ diamond shapes that form in exhaust plumes ¾ for the Space Launch System model.
The NASA technology is already being used worldwide, adopted by over 50 institutions in more than 8 countries, from Notre Dame to the University of Liverpool. Companies continue to license the technology and commercial versions are hitting the market.
The impact has been so significant that NASA's researchers earned multiple awards. R&D World gave SAFS a spot on its 2025 R&D 100 Awards, selected by a panel of global experts.
NASA also named the SAFS a 2025 NASA Government Invention of the Year, the highest award the agency gives to groundbreaking technologies.
To understand why the SAFS is a big deal, you need to know what researchers were working with before.
The older focused schlieren imaging setup required researchers to have access to both sides of what they were testing. They needed to set up separate grids of light sources on each side and align them perfectly with each other. It's the equivalent of lining up two window screens on opposite sides of a room so their patterns match exactly.
Setting up one of these systems could take weeks of painstaking adjustments, and if someone accidentally bumped the system or needed to make an adjustment? Start over.
Enter the SAFS system. In 2020, NASA researchers asked a critical question: What would happen if they could eliminate all that complexity by using the properties of light itself?
The solution? Light polarization. Your polarized sunglasses work by filtering light in specific directions. The SAFS system does something similar, using light polarization to create the same effect as the older, cumbersome dual-grid setup. The SAFS system only requires access to one side of the object you're testing. And, instead of needing two separate grids that must be perfectly aligned, it uses just one grid that does double duty.
What used to take weeks of setup now takes just minutes. Need to make adjustments? No problem. The SAFS system can tweak sensitivity, change its field of view, or adjust focus on the fly. The system is compact and immune to vibrations (goodbye, starting-over-because-someone-walked-by).
Sometimes revolutionary advances come not from adding complexity, but from finding new creative solutions to age-old problems. The SAFS is proof that there's always room for innovation ¾ and this one is already making its mark on the world.
The work on SAFS was supported through NASA's Aerosciences Evaluation and Test Capabilities portfolio office and Transformational Tools and Technologies project, which works to develop new computational tools to help predict aircraft performance. The project is part of NASA's Transformative Aeronautics Concepts Program under its Aeronautics Research Mission Directorate.
