November 30, 2020
Additive manufacturing in the realm of space exploration is still fairly new, having been introduced in the last decade. The first structural “AM” parts to be launched into space were a set of eight titanium waveguide brackets onboard NASA’s 2011 Juno mission to Jupiter.
The move to include additively manufactured parts on a spacecraft was considered potentially risky. For spacecraft and instruments, which undergo a seemingly endless battery of tests before launch, the largely untested capability of a 3D-printed part in space carried too many unknowns. Fortunately, AM fared well on Juno, and the development of spacecraft instrument parts by this method (including 3D printing) has continued to improve — allowing engineers to take advantage of an ability to create intricate components faster and more easily.
Now, the Johns Hopkins Applied Physics Laboratory (APL) is taking the plunge with its own additively manufactured metal part on the Particle Environment Package (PEP)-Hi instruments aboard the European Space Agency’s (ESA’s) JUpiter ICy moons Explorer (JUICE) mission, a first for the Lab.
JUICE aims to study gas giant Jupiter as well as its three biggest moons, Ganymede, Callisto and Europa, which are thought to harbor water beneath their icy surfaces. The mission, launching in 2022 and then traveling for seven years toward its targets, will try to determine whether those ocean worlds can support life. JUICE will rely on a sizeable payload of 10 instruments, including PEP, which consists of six sensors that will map the plasma surrounding Jupiter.
APL is building one of those sensors, PEP-Hi, which comprises two particle detection instruments: Jovian Energetic Electrons (JoEE) and Jupiter Energetic Neutrals and Ions (JENI).
JENI, a dual-functional camera and ion spectrometer, will help the mission observe and analyze the gaseous atmosphere around Europa and Callisto. JoEE, a multidirectional electronic spectrometer, will study the magnetosphere of Ganymede.
The PEP-Hi instruments are notably small. However, JENI, a boxy structure with a fanned-out top, towers over JoEE, a rounded, Roomba-like instrument with intricate panels. JoEE’s panels, each about the size of a quarter and stitched together to form what is called a collimator, may not look like much to the naked eye, but closer inspection reveals that they are peppered with hundreds of tiny holes that can filter even smaller particles like electrons for detailed observations, and protect the fragile detectors inside the instrument. This intricate — and delicate — collimator gave the team the most trouble during JoEE’s construction.
“It was difficult to get a very small collimator onto JoEE, and we were having problems with the materials and finding manufacturers who could actually make them,” said Cori Battista, Space Exploration Sector (SES) program manager for the PEP-Hi instruments.
After several traditionally manufactured parts failed to make the cut, Battista and her team turned to APL’s Research and Exploratory Development Department (REDD) for help.
Around 2017, Battista recalled, REDD’s Michael Presley suggested additive manufacturing. Presley, an AM engineer, recognized that scientists were designing and building the part from a “unique scientific point of view,” which created a unique manufacturing challenge.
“Electrons coming into this sensor are controlled by magnets, and magnets have a spherical field,” Presley said, pointing out the 518 tiny holes found in each collimator segment. “Every one of those holes has to be angled in a different way because they are aligned to that spherical magnetic field.
“The problem was that, traditionally, we make collimators for straight fields, so they’re basically just grids,” he added.
When Presley and his team in REDD made a first attempt at building the collimator using traditional machining, that issue was evident. “We couldn’t get through a single one of these segments without the drill snapping off,” he said.
For over a year, Presley experimented with several materials and approaches, finally settling on a combination of 3D printing and machining.
Additionally, instead of printing the collimator in one piece, Presley split it into nine, which allowed him to flip the print orientation and angle the tiny holes. The pieces were then bolted together to form the curved band that would attach to the JoEE instrument.
But as Presley pointed out, proving it’s doable is only half the battle.
The REDD team also needed to validate its parts and secure NASA approval. The team reached out to the additive manufacturing team at NASA’s Marshall Space Flight Center to work out a qualification process meeting agency standards. From 2018 to 2019, Presley and team members across the Lab worked to implement new qualified processes for AM parts, including new process controls, inspection techniques, quality documents, and more than 60 pages of documentation for meeting the standard, which is currently being used to build an AM part on another APL-led space mission: NASA’s Double Asteroid Redirection Test (DART), launching in 2021.
That component, part of the baffles for the sun sensors aboard the DART spacecraft, is simpler than the collimator, but the ability to easily and quickly create custom dimensions at the Lab made AM the best choice.
“This was the first time we were doing something like this with the PEP-Hi project,” said Battista. “I am the biggest supporter of what REDD is doing with AM.”
Even during the COVID pandemic, which threatened to derail the building and delivery of the JoEE and JENI structural thermal models, the team overcame numerous hurdles and completed the models ahead of schedule. The team delivered the PEP-Hi instrument models to ESA in October and continues to work on the parts that will eventually be part of the JUICE spacecraft.
“I can’t overstate how big a deal it is that in two years we went from not even being allowed to print 3D parts [for space missions] to creating a full flight part,” Presley said. “The JUICE PEP-Hi team and Space Exploration Sector really came together and delivered the components needed to get certified by NASA. We went from very little cross-pollination between REDD and SES to a really fruitful collaboration that is still yielding independent research and development projects and a fully qualified flight part in a span of two years.”
The successful collaboration between SES and REDD on JUICE points to additive manufacturing becoming an integral part of future space missions. With DART launching next year, and JUICE soon after, it’ll be a testament to the innovative capabilities of AM.
“[With additive manufacturing], you can do geometry you just can’t do any other way,” said Presley.
Media contact: Justyna Surowiec, 240-228-8103, Justyna.Surowiec@jhuapl.edu
The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit www.jhuapl.edu.