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Boeing has used the Pegasus 5 software widely, including on its 777X, which is slated to fly in 2020.

In the late 1990s, as computers were becoming more powerful, Stuart Rogers began working on Pegasus 5 software that made use of this increasing processing power to dramatically transform how airplanes and spacecraft are designed and built.

The code enables designers to do the bulk of their work on the computer, reducing the number of expensive and time-consuming wind tunnel models and tests required for a new aircraft or upgrade.

“It can be applied to many, many different types of problems, from airplanes to spacecraft to rockets to internal flows,” said Rogers, who has worked at NASA's Ames Research Center since arriving in 1984 as a student. “If you've already studied your whole design space in the computer, then you only need to build a wind tunnel model to verify that performance.”

The software itself is a preprocessor for overset-grid computational fluid dynamics (CFD) simulations. This CFD approach divides large domains into smaller, more workable segments. Pegasus 5 reassembles the pieces, stitching together the various parts of this complex geometry for a flow solver, which computes the aerodynamics or fluid dynamics for the problem at hand. Before Pegasus 5, piecing these segments together was a painstaking process consuming much more time and user input.

“We set about trying to improve the capabilities that we had and really sped up the process dramatically,” said Rogers. “Pegasus 5's primary goal was to come up with new algorithms to really automate the process of gluing together all these geometrical parts without so much user input, so you didn't need a super-experienced user to do it,” Rogers said.

Rogers’ work on Pegasus 5 began in 1998 at NASA's Advanced Subsonic Technology (AST) Program, a joint research effort with Boeing. The multiyear program supported the development of Pegasus 5 for two years, a process that involved Boeing from the beginning, as the company helped define the technical requirements of the final product. Boeing was one of the first companies to apply Pegasus 5 “to very complex and realistic aircraft configurations,” according to Robb Gregg, chief aerodynamicist for Boeing's Commercial Airplanes Division. Boeing lobbied “for a greatly streamlined and automated alternative to PEG4,” Gregg said, referring to Pegasus 4, the upgrade's predecessor, which Boeing also used.

This rendering of the surface of the Space Shuttle's external tank illustrates the complex geometry capabilities of the Pegasus 5 software.

Rogers went on to use Pegasus 5 on numerous projects at NASA, including the Space Shuttle Program, where he helped investigate the 2003 accident of the Space Shuttle Columbia and helped the program return to flight. As he used Pegasus 5 over the years on increasingly powerful computers, Rogers saw how to make it better. “We made incremental improvements to the software, none of which were actually funded directly by any program,” he said.

Every once in a while, Rogers releases a new version and sends it to NASA users, Boeing, and other companies. The code has been distributed to more than 470 organizations in industry, academia, and the U.S. Department of Defense. Pegasus 5 has been used to develop or upgrade essentially every major NASA spacecraft in the past 15 years. Pegasus 5 has run simulations for NASA's next crewed spacecraft, Orion, as well as the Space Launch System being built by Boeing that will transport astronauts aboard Orion into orbit and beyond.

Boeing meanwhile has been using the software widely to develop and support its commercial airplanes, military aircraft, and spacecraft. The company used Pegasus 5 in the development of its wide-bodied 747-8 — the longest passenger aircraft in the world — and the latest versions of the 787 Dreamliner. Pegasus 5 simulations also played a role in developing the 737 MAX, which first flew in early 2016, and the 777X, which is slated to fly in 2020. The company has also used Pegasus 5 for smaller tweaks to jetliners currently in use, such as when Boeing added new antennas to improve Internet service on passenger flights.

Gregg notes that while Pegasus 5 helps Boeing save time, an even more important benefit is the reduction in potential user errors. “Previously, we had to either simplify geometry or strictly limit the use of overset-grid CFD to the verification of the design, which was typically developed using other in-house capabilities,” Gregg said. “Today, much of the uncertainty of analysis and design has been eliminated.”

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This article first appeared in the January, 2019 issue of Tech Briefs Magazine.

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