NASA’s Marshall Space Flight Center is building a small CubeSat that uses an 85-m2 solar sail deployed from a central location to capture the push of photons from the Sun as its propulsion source. To integrate this sail into the CubeSat, NASA inventors have developed a new method for folding and packaging the thin membrane.
Increasing packing efficiency by 25 to 30%, the bowtie folding process avoids pocket voids by folding the sail in a Z-fold along its edge. Once the Z-fold is complete, the material is then rolled onto the center hub. The smaller footprint of the stowed solar sail makes the process more practical and economical.
The technology consists of a method/design for folding a 3-micron-thick polyimide solar sail to fit into a 4 × 6 × 8” space. Once in orbit, the solar sail is deployed uniformly from a central hub to power a CubeSat. The bowtie folding process reduces void space, allowing trapped air to escape when subjected to a vacuum. The sail is first Z-folded from one end to the other, creating a long strip of stacked sail that is then folded in half so that it lays upon itself before being spooled onto a central hub. The folding style, which has not been previously documented, leaves all four corners of the sail exposed. The method delivers much improved packing efficiency compared to previous designs, is beneficial for reflective surfaces, and avoids the weakening risks associated with traditional folds.