As an engineer at the NASA Jet Propulsion Laboratory (JPL), Evan Hilgemann (MSAE ’15) is drawing on hands-on experience he gained as a Michigan Aerospace Engineering graduate student to develop innovative space exploration technologies, including small satellites and exoplanet observational tools.
Evan first gained exposure to small satellites as a graduate research assistant for Michigan Exploration Laboratory (MXL), a leading CubeSat development group under AE Professor James Cutler. At JPL, Evan worked as the Mechanical Lead for a large aperture CubeSat antenna designed to measure high-frequency radio signals from low-Earth orbit. Evan notes:
“In MXL, I was focused on guidance, navigation and control and attitude determination control systems [which are heavily software-centric tasks]; for the JPL CubeSat mission, I was doing mechanical design. Though the specific problems were different, my MXL research familiarized me with the process and mindset of working on smaller spacecraft, which was very valuable.”
Since delivering the CubeSat hardware, Evan has joined the Starshade development team. JPL’s Starshade is designed to enable direct observation of planets outside our solar system by blocking out the light of a distant star around which a dim “exoplanet” is orbiting. This can be visualized as using your hand to block out the light from a bulb to see a small bug buzzing around – except the bulb is 1 billion times brighter than the bug. Evan reflects:
“In the same way that at the beginning of the 1900s we began having a decentralized view of our galaxy – we started to realize that all those fuzzy blotches in the sky were actually other galaxies! – we are having a growth of perspective now; we are understanding that there are [abundant] planets outside our solar system, and with technology like Starshade, we can study [their atmospheres and composition].”
To achieve its goal of blocking out distant starlight for an on-looking telescope, the Starshade must be fabricated to extreme precision. This comes with a unique set of technical challenges, as Evan explains:
“The petal shape of the Starshade is designed to prevent light from diffracting around the edges and into the telescope. If your Starshade was circular, your telescope would see rings of light that would totally wipe out the visibility of the planet. To get rid of that diffractive effect, you need to manufacture the Starshade to very specific tolerances.”
“In the same way that at the beginning of the 1900s we began having a decentralized view of our galaxy... we are having a growth of perspective now."Evan Hilgemann
How specific? The perimeter of the petal has a profile tolerance of 100 microns, or about the width of a human hair. The radius of the edge of the petal has to be even more precise, with a tolerance of only 1 micron.
To accommodate these strict requirements, Evan and his team members must be highly conscious of the materials and processes that they implement:
“We have been running all sorts of studies on the benefits of using different materials and chemical etching processes. Right now, we are looking into amorphous metals; they don’t have a crystal structure, which gives them benefits of both metals and ceramics in one package. Because they don’t have grain boundaries [caused by a crystalline structure], the etching process can be done very uniformly and doesn’t result in jagged edges [that could scatter light].”
Moving forward, Evan is eager to gain exposure to new aspects of mission development:
“Coming off of my CubeSat work, I am interested in gaining some broader experience with flight design. Starshade is a very hands-on, active prototyping environment. I’ll be able to help bring the design to maturity [for hopeful use on missions like the WFIRST telescope], which is an interesting challenge.”
For a simulation of Starshade’s deployment sequence, see below: