How to improve design, enhance vibration and thermal performance in small satellites using industrial 3D printing and composite materials.
It is commonly known that cube satellites and small satellites are providing an effective alternative to larger, more expensive satellites for those companies, universities and teams interested in launching their payloads into orbit.
As demand to access to space grows, engineers are adapting these small structures to provide new achievements and goals, so it’s reasonable to say that the production and launch of small satellites is revolutionising the Space industry.
Additive manufacturing technology not only helps this radical change to be fulfilled, but has itself reached new heights with the production of structural components for the new generation of space craft. These heights have been reached thanks to the combination with advanced composites as manufacturing materials.
Designing with AM
Additive manufacturing is often faster than designing and producing a tool for traditional manufacturing technologies. Furthermore, 3D printing gives more flexibility in the timeline to make design improvements and being able to think outside of limitations caused by traditional tooling. This choice makes it possible to substantially reduce the costs and is very convenient in terms of timing when compared to traditional production methods.
While the challenge of designing is addressed with the use of additive technology, the next step is to find a material that meets the rigid mechanical properties required for space applications. This is not easy research: a variety of additive technologies available on the market can produce the majority of designs, however, not all the materials for AM are appropriate. For example, some material properties could be too weak for space ready parts and structures. So selecting the right material is fundamental when opting for AM.
The OreSat0 CubeSat
An example case is represented by the Portland State Aerospace Society (PSAS) that built OreSat0, their very own artisanally hand-crafted CubeSat system, fully open source, modular and reusable, designed for educational teams. They have been a fan of additive manufacturing for some time now so the first transition to professional 3D printing was not “traumatic” for them.
In this specific case, they used Fused Deposition Modeling (FDM) 3D printing until they prototyped a design that worked. Then they switched to Selective Laser Sintering (SLS) which “worked extremely well”, say the PSAS team. The team then faced the “real” challenge: find a SLS material to manufacture functional, flight-ready parts capable of meeting the requirements for their OreSat0 system, including minimising volume and mass, isolating systems both thermally and electrically, and be robust enough to withstand 14g random vibration environmental testing.
In particular the team needed to pack one of the OreSat’s critical subsystems, a tri-band deployable antenna system, in a volume of only 5x5x2cm. The antenna had three separate antennas (UHF at 436.5 MHz, L band at 1.265 GHz, and L1 at 1.575 GHz) each with 4 elements; all 12 of these elements had to be deployed using nylon monofilament lines and only a single melt resistor.
Metal couldn’t be used because it would detune the antennas, but most 3D printing materials weren’t up to the task of being flown in space. After researching all available materials, the team came across a composite material, glass fiber reinforced, named Windform LX3.0. “The SLS technology combined to this material allowed us to pack so much functionality in such a tight space. We’ve never seen anything close to the packing density of this antennas system”, says Cass Bloom, a mechanical engineering student at Portland State University. He continues, “There was no way we would have been able to get the packing density of three bands with four elements each in anything other than a 3D printed, non-conductive process. We don’t know of any other satellite with this kind of antenna density.”
Manufacturing materials
The parts that PSAS decided to manufacture using SLS and glass fiber reinforced composite material, were critical for vibration and thermal performance. That’s why.
Before the satellite is integrated into the launch vehicle, it must first pass a 3 axis, 14g random vibration test and undergo a full thermal evaluation using simulation software. Vibration inside of a rocket headed to orbit is intense, and it is very important that nothing inside of the satellite vibrates free or worse, breaks apart. Once the satellite is in orbit, it is exposed to a range of sometimes intense temperatures that must be carefully considered when choosing materials to include.
The PSAS team highlight, “The manufacturing material we chose, consistently met both of these needs, being for example able to withstand extreme thermal cycling from -40 to +100 C. It become an integral design parameter for our OreSat.”
OreSat0 was deployed into low earth orbit on March 15th, 2021. PSAS planned to set OreSat0.5 for flight in October 2023, whereas they scheduled to deploy OreSat1 via the International Space Station in early 2024.
The OreSat0 main structure was made out of machined aluminum, which is a requirement of the CubeSat specification; the OreSat0 parts that PSAS decided to produce using SLS process and glass fiber reinforced composite material are, in addition to the turnstile antenna assembly: the star tracker used in the camera lens and sensor assembly; the battery assembly.
PSAS’s future CubeSats have the SWIR camera lens holder and helical deployer as well 3D printed in Windform LX 3.0 glass fiber reinforced composite material.
Nathanael Baker is the Senior Project Coordinator at CRP USA