First there was fabric over wood and/or metal frameworks. Then were was metal over metal, which led to monocoque construction. Eventually, composite materials followed suit, complete with a subcutaneous layer of acoustic foam to keep things quiet. Paint protects and makes pretty the skin’s exterior; between it and a composite skin is some form of lightening protection and a filler to smooth out any layup imperfections.
Working as a team with GE and the Georgia Institute of Technology on a NASA study completed last year, N+3 Small Commercial Efficient and Quiet Transportation for Year 2030-2035, Cessna turned things around to create a new composite skin it calls STAR-C2, for “Smoothing, Thermal, Absorbing, Reflective, Conductive, Cosmetic.” Not only does the new skin weigh less than half of the current composite coatings, Cessna just received a NASA contract to develop it.
Wired called the Cessna innovation a “self-healing “magic skin’ condom for future aircraft.” I didn’t read the entire 422-page NASA report, so I might have missed the “self-healing” part, but page 270 talks about STAR-C2’s goals, objectives, and many benefits. Increased damage tolerance is one of them, thanks to a layer of energy absorbing foam that takes one for the team.
Over the foam is a conductive layer that not only protects the composite structure from lightening. It also provides EMI and environmental protection and holds the possibility of saying “ouch!” and telling you where it hurts. It all works logically on paper, and now Cessna has the money to address the challenges this innovation presents.
The report’s timeline makes the effort seem quick and easy, until you look at the challenges: skin gaps, door/window seals, external antennas, non-flush fasteners, zone wiring, repair continuity, deice and anti-icing, and many more. And let’s not forget durability, reliability, a monitoring system, and cost.
A decade ago STAR-C2 might have been considered technology worming its way under the wall of science fiction. Today, the challenges it poses are not insurmountable. It is starting small: the baseline is a 20 passenger airliner that will set new standards of efficiency, economy, and environmental impact.
Weight has always been the enemy of powered flight, and anything that reduces it makes aviation’s ultimate challenge—finding a renewable source of power to sustain flight so it has a future—is another goal worth pursuing. — Scott Spangler