Cube Sat project 3D printing for space: assemblies withstand extreme conditions
3D printed components were manufactured by CRP USA for the Portland State Aerospace Society’s Oresat0 Cube Sat, Oregon’s first satellite, deployed into low earth orbit in March 2021 and successfully operating since then. A turnstile antenna assembly, a star tracker camera lens and sensor assembly, and a battery assembly were all 3D printed out of Windform LX 3.0.
The small satellite or “nanosatellite” revolution is here. Kilogram-class satellites, like Cube Sats, now have functionality that were only available in larger 100 to 1,000 kg class satellites. Recently, 3D printing has helped speed up this revolution, especially in universities. Cube Sats have been launched by dozens of countries, universities and companies all around the world. And the state of Oregon joined them recently thanks to the Portland State Aerospace Society (PSAS) that built Oresat0, their very own artisanally hand-crafted Cube Sat system, currently in low Earth orbit. This achievement was possible thanks to their use of Windform LX 3.0 composite material and industrial 3D printing in their most critical subsystems.
The Oresat bus project
The Portland State Aerospace Society is an open source, interdisciplinary student aerospace project at Portland State University in Portland, Oregon, with collaborators at most other Oregon universities. They make sophisticated amateur rockets, small liquid fuel rocket engines, and Cube Sat nanosatellites.
They currently have three satellite missions in the works. All rely on the fully open source Oresat bus which they are offering as an inexpensive (for a satellite) “DIY” platform for designing and building 1U through 3U Cube Sats, paving the way for a solution to the “Cots vs DIY” dilemma.
“Oresat is our fully open source, modular, and re-usable Cube Sat system designed for educational teams”, said PSAS members. “Oresat uses a card cage system, which allows cards to be reused on different missions from 1U to 3U Cube Sats. Cards include everything you would expect aboard a Cube Sat: an on-board computer with multi-band radios, a battery pack, a star tracker, a GPS receiver, and the beginnings of an attitude determination and control system (ADCS). Solar modules are mounted on the outside of the Aluminum frame, along with deployable omnidirectional antennas.”
Oresat0 was deployed into low earth orbit on March 15th, 2021 and has been successfully operating since then. Oresat0.5 is being readied for flight in October 2023, and Oresat1 is scheduled for a deployment off of the international space station in early 2024.
The staellite project
The Portland State Aerospace Society is determined to develop better students through hands-on interdisciplinary systems engineering projects. Everything is designed, built, and tested by interdisciplinary student teams: mechanical engineers work on the structure, thermals, and CAD, Electrical engineers design the cards made of PCBs (standard two and four layers boards), and computer science students program the Linux boxes and microcontrollers that run the Cube Sat.
PSAS members added, “There are very few open source satellites in the world, and ours is probably the most fully featured. We are currently collaborating with four other universities who are building satellites and ground stations based on our projects.”
Using industrial 3D Printing and Windform
Before employing Selective Laser Sintering and Windform LX 3.0 for manufacturing subsystems on Oresat0, PSAS members used other technologies. “We designed and manufactured the parts locally using extremely inexpensive FDM machines until we prototyped a design that worked. We then switched to SLS 3D printing, which worked extremely well. But we couldn’t find SLS parts that could stand the temperature extremes and that were vacuum rated to Nasa and Esa outgassing standards. We were absolutely thrilled to find CRP Technology’s Windform LX 3.0 composite material and CRP USA. With Windform LX 3.0, we could design the parts for 3D printing, run quick turns to prototype on local printers, and then print our final engineering and flight units out of Windform.”
According to the engineers, this absolutely changed the way they design all parts of their satellite thanks to its characteristics: Windform LX 3.0 can be used in space; it has extremely good material properties; it is extremely easy to work with; it is far superior to other 3D printing materials, including the other FDM, SLA, and SLS technologies that the team used.
The team chose Windform LX 3.0, a glass fiber reinforced material from the Windform Top-Line range of composite materials for Powder Bed Fusion 3D printing process (Selective Laser Sintering). It allowed the PSAS team to use 3D printing processes on their critical subsystems, including their extremely reliable deployer for their tri-band turnstile antenna. The antenna has 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 are deployed using nylon monofilament lines and only a single melt resistor. According to the team, “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.”
Using CRP’s Windform LX 3.0, PSAS members were able to mount their star tracker sensor and lens on a small daughterboard that kept the entire assembly to a single 10 mm tall card form factor.
The battery pack needed to reliably hold 18650 cells through vibration testing while also providing thermal and electrical insulation from the rest of the satellite. Windform LX 3.0 allowed PSAS to make an extremely compact battery assembly that was still extremely rugged.
Testing performed on printed parts
Before integration into the launch vehicle, Oresat0 (with 3D printed parts in Windform LX 3.0) was subjected to the following testing: Three axis 14 g random vibration, -40 to +80°C thermal cycling, and vacuum cycling. Windform performed flawlessly for all of these tests. “And of course, continue to perform in low earth orbit for the last year”, add PSAS members.
According to the students: “Working with nanosatellites means extremely limited volume for all systems, so the ability to evolve and maximize the use of our space has been very beneficial. We pack a lot into a small space, and we can plan to use nearly every cubic millimeter when we can use 3D printed parts.”