In 1973, Edwin J. Saltzman, an aerospace engineer at NASA's Dryden Flight Research Center, had a moment of inspiration while bicycling to work. He noticed how the aerodynamic wakes of passing semi trucks would push him and his bike toward the shoulder and then suck him back toward the road.
This experience led him to brainstorm ways to help trucks slice through airflow more easily, improving fuel efficiency in the process. Saltzman recruited colleagues and an old Ford van from the Dryden motor pool, which was transformed into a test bed. The engineers started by covering the van in flat sheets of aluminum with 90-degree corners to provide a baseline drag measurement while simulating the boxy motorhomes of the period.
They then methodically altered the shape to reduce drag, first rounding off the front vertical corners, then other surfaces, and finally sealing the underside of the vehicle. These changes created a smoother path for air flowing around the vehicle compared to trucks of the period. A typical truck would plough through the air with its broad front end, leaving that air to flow around the vehicle unevenly, as well as congregate in a low-pressure area at the back—all of which created drag.
The van was retested after each modification, and engineers recorded a 52% drag reduction from rounding off all four front edges, and a further 7% reduction from sealing the van’s underside. Later tests with underbody fairings and a boat tail showed a 15% drag reduction. This test truck looks crude, but not any more bizarre than the products of the Energy Department’s SuperTruck program, which challenges manufacturers like Navistar and Kenworth to build more-efficient rigs.
And NASA’s research has had a real impact on the shape of new trucks. Today, aerodynamic fairings and rounded corners are common features on semi trucks. Some trucks and trailers also have Mitsubishi Lancer Evolution-style vortex generators marketed under the Airtab brand name, a direct result of later NASA research.
It’s an example of how the agency’s considerable engineering resources are used for more than just space exploration. The discovery by Saltzman has led to significant improvements in fuel efficiency for semi trucks, making them more environmentally friendly and reducing their carbon footprint.
This project showcases the power of interdisciplinary research, where engineers from different backgrounds come together to tackle complex problems. By applying aerodynamic principles learned from space exploration to a real-world problem, NASA was able to make a significant impact on the trucking industry.
