September 2017 - Present
Space Ice is a part of Northwestern University's Dunand Research Group currently developing a NASA-funded CubeSat in collaboration with the University of Illinois to run in-orbit experiments of freeze-casting, a potential space-based materials manufacturing method. We, at Northwestern, are designing the experiments and payload, while UIUC is building the satellite bus. As the lead engineer for Space Ice, I am responsible for ensuring the structural integrity and compliance to standards of the design, and manufacturing the payload.
The Space Ice payload (right) houses the sample containers (left), optical systems to image the experiments (middle), and electronics that run the experiments and communicate with the satellite bus. When developing and evaluating designs, I have to not only consider the strength and rigidity of the components, but also other factors that are often unimportant in applications outside of aerospace, such as outgassing limits and the use of materials with similar thermal expansion properties for interfacing components. Although the forces in orbit are very minimal, the payload has to withstand the immense acceleration of the rocket launch, so I make sure my team's FEA analysis is as accurate of a simulation as possible.
The aforementioned considerations, along with the 0.7 lb mass and the 3.5 in. square profile limits result in many manufacturing challenges. Having three sample containers requires three sets of most components and greatly reduces the space for structural supports in terms of both clearance and the mass budget, resulting in very small, complex parts. This means that I have to carefully select the order of machining setups and methods of fixturing to reduce stacking tolerances, especially since most parts require both turning and CNC milling operations. Additionally, some of the small features, like the 1/64" thermocouple probe holes require a lot of testing of speeds and feeds and particular attention to tool dimensions to avoid collisions with the shank and fixturing. In terms of material selection, the glass sample containers require the use of Kovar for the interfaces since it has similar thermal properties, but presents an additional set of machining challenges. The high toughness of Kovar also requires testing of machining speeds and feeds to achieve a nice surface finishing, but also constant inspection of the tools since they dull easily.
The Space Ice CubeSat is set to launch in late 2018. If you would like to learn more about our research and progress, please visit spaceice.space.