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The objective of this design project was to construct a CubeSat deorbit device. Using applicable research sources, a best practice design for an inflatable deorbit device was to be constructed and demonstrated as a prototype. The device was to be part of the payload for a 1U CubeSat, meeting all of the standards for that CubeSat type.
The benefits of constructing this demonstration device was a proof of concept. The first concept to be proved was that this payload can meet the constraints of a 1U CubeSat payload (size, mass, etc.). The second benefit was the development of a low cost, reliable method to deorbit a CubeSat. The removal of high altitude CubeSats will reduce a significant future source of space debris.
The approach chosen was to design an inflatable balloon or pillow shape. This design was less complicated than a fixed folding array design. Depicted in (7)Figure : Predicted lifetime of a 1U CubeSat without deorbit module (7). It can be seen in the figure that the predicted lifetime is well in excess of 400 years. Figure is the predicted lifetime of a 1U CubeSat with a ballistic coefficient produced by increasing the frontal area to approximately 0.6 m2 . The increased surface area resulted in an effective deorbit device. The deorbit device successfully removed the satellite from orbit within the prescribed 25 year life span.
Figure : Predicted lifetime of a 1U CubeSat without deorbit module (7)
Figure : Predicted lifetime of a 1U CubeSat with deorbit module (7)
The actual shape of the inflatable structure is dictated by the complexity of constructing the volume. It is for this reason that a pillow shape, as shown in Figure , will be used. The pillow design need only be sealed along the edges, and thus lends itself to a simpler design. Material selection of the pillow is critical. In the harsh low earth orbit regime, radiation and atomic oxygen are the primary concerns (7). The material chosen to survive this environment is a polyimide film known as Kapton®. Kapton is a product of the DuPont Company and has a proven track record for long term space applications (8).
The inflation of this balloon must be done with a reliable gas source. There are two main options in this area. The first is a cool gas generator, and the second is a stored refrigerant. Several companies specialize in developing space qualified cool gas generators for various applications. One company specifically, Bradford Engineering, has developed a 2 gram cool gas generator. This is a perfectly viable method to inflate a small deorbit mechanism for a CubeSat (9). For the refrigerant option, a simple pressure vessel containing the fluid would be sufficient (7).
Figure : Deorbit Pillow Construction (7)
The actual triggering of the deorbit device can be accomplished either by an onboard timer or with ground based signaling. The actual activation will be processed through the main bus of the CubeSat and should require a minimal fraction of the total CubeSat’s available power (~5%). The housing for the deorbit device will be constructed of the 6061-T6 aluminum alloy, per NASA and California Polytechnic guidelines. This alloy is common to the entire CubeSat and P-Pod launcher, and offers the best density option for design integration and weight minimization.