Every color used in the construction of a parachute has a purpose. On some, it satisfies the owner’s aesthetic. For others, it is advertising. In the military, the color serves a specific requirement for visibility, or the lack of it. And then there’s the seemingly haphazard arrangement of orange and white panels on the parachute that slowed the descent of NASA’s Perseverance rover as it plummeted toward the surface of Mars. It was unique, so there had to be some reason for it, and finding out what it was consumed my free moments.
Anyone who thinks engineers are the antithesis of fun need only look at this chute. The New York Times reported that Allen Chen, the engineer in charge of the rover’s landing system, said during a post-landing news conference that “Sometimes we leave messages in our work for others to find for that purpose, so we invite you all to give it a shot and show your work.” The article, “NASA Sent a Secret Message to Mars. Meet the People Who Decoded It,” introduced the people on Earth who immediately tackled the challenge.”
My guess is that all of them have seen The Martian, the addictive Matt Damon film, or read Andy Weir’s book for which it was named and so closely hews. But the oddly arranged panels of orange and while did more than spell out “Dare Mighty Things” in binary code. (Here is NASA’s decoder ring, with an explanation in “STEM Learning: Mars Perseverance Parachute Coding Activity.“)
Embedding the message was a bonus benefit devised by parachute system engineer Ian Clark, who also worked on the slow-down system for the preceding Curiosity rover. Evaluating the high-speed video of a high-altitude test failure of a prototype design, Dr. Clark found the chute’s checkerboard pattern complicated the analysis of how the fabric unfurled and inflated. Knowing that Perseverance would live-stream its descent to Mars, he got approval for a distinct pattern that would simplify post-flight evaluation.
Each of the 80 gores that made up the 70-foot chute is composed of four panels, 320 pieces of fabric that can be a different color, but he stuck with the two colors used on previous extra terrestrial parachutes because the fabric dyes had proved successful. It makes sense that jeopardizing a $2.7 billion mission to Mars by introducing a new color, no matter how aesthetically pleasing, would surely be a career limiting move for everyone in that approval chain.
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If the name Theodor Knacke means nothing to you, don’t feel bad. It meant nothing to me, until last week when I learned about the man and his lifetime contributions to the field of aerodynamic decelerator systems, also known as parachutes. Many people in aviation only think about—and appreciate—the parachute if it is the only thing that will prevent a sudden stop after long fall. But just think, where would the space program be without the parachute, and the uncountable thousands whose lives have been saved by this seemingly simple device? And let’s not forget those who fling themselves from high places for fun.
When looking at the details involved, designing a decelerator system is one of aviation’s premier engineering challenges. Working with a variety of sewn together textiles an engineer must create an aerodynamic system that reliably assembles itself in midair. Sounds simple, doesn’t it? Let’s consider the parachute used in an F-18. It must fully deploy so an aviator does not come to a sudden stop after ejecting at zero speed and zero altitude. At the other end of its performance spectrum, the parachute must assemble itself in such a sequence that it does not self-destruct when it unfolds at 40,000 feet in a Mach number slipstream. And just to make it interesting, the parachute must be packed and hydraulically mashed into a solid textile brick that is wedged into the top of a seat under a canopy where the brick bakes on sunny days, freezes at altitude, is bathed it corrosive salt sea air for months and months and months.
And the engineer who wrote the book—literally—on meeting this daunting engineering challenge?