Recently, the Wolfpack went through integration for our FlipSat-1 satellite. It is a mission to validate the usage of Micro: bits in space, a microcontroller that has no flight heritage, by testing the frequency of SEU’s (Single Event Upsets) - when radiation flips a one to a zero or vice versa in a computer storage unit - in space travel. The CubeSat will be traveling on Near Space Launch’s (NSL) TROOP mission – a satellite on a ring with a number of satellites containing several payloads.
The integration took place at NSL’s headquarters in Upland, Indiana. NSL is a company specializing in space flight and communications technology founded at Taylor University by professors Hank Voss and Jeff Dailey. Last week, Mr. Simmons and I traveled to Indiana and spent a few days at their labs.. I gained valuable experience from working with John Pugsley, an experienced engineer at NSL, learned a lot about what space-grade means, and got to contribute directly to a complex space project.
When I first arrived in Indiana, John and I tested the payload to ensure that it was good for space travel. After an initial review, some challenges arose. First, we learned that one of the payload materials would not be space-worthy. Space-grade materials can survive the harsh conditions of space without issue: temperature, radiation, and vacuum . A good example is aluminum – it is not affected by the extreme high or low temperatures in space. However, PLA (Polylactic Acid), what we typically use in 3D printers and the original bracket’s material, cannot withstand these conditions and is not viable for space travel. Instead, it could disintegrate.
Figure 1: The Micro: bit (top) mounted in its bracket above the Mux breakout board (bottom)
The payload also used a volatile adhesive, meaning that, to reuse parts, all the glue would have to be removed, a very difficult task. The payload requires 8 EEPROM boards (Figure 2), a Mux EEPROM breakout board (Figure 1), and a Micro: bit controller (Figures 1&2). The original version also included a Micro: bit breakout board, which only took up more space while not being needed. All of these issues meant that the payload was not a viable prototype until some changes were made, setting back integration significantly.
Figure 2: Two stacks of four EEPROMS (left) and the Micro: bit microcontroller (right)
That night, I worked on creating a layout for the circuit boards so that they would be mounted directly onto the aluminum plate or on top of each other to save space and replace the volatile materials. Mr. Pugsley and I modeled a bracket in SolidWorks (Computer Assisted Design software) and used a Computer Numerical Control (CNC) Machine to drill holes into the aluminum plate and create a bracket out of a space-grade plastic. Finally, we assembled the boards onto the bracket and plate and the payload was ready to go.
But not only does the material and the mechanical design have to be ready for space, the software must also be space-grade. It means that the CubeSat mission has to be very efficient when using satellite communications to the ground, which is typically costly. We tested the code and found that, while it was functional, there was an opportunity to make the data transfer significantly more efficient. The idea is to transmit one data packet with all the telemetry collected in sequence, rather than sending each datapoint separately as text. The receiving end of the group will then extract all the relevant data points from each packet received.
This experience taught me several lessons. First, I learned the do’s and do not’s of space experimentation: carefully take into consideration the materials used, ensure the payload complies with all restrictions regarding power, data volume, and space, remove all unnecessary components, and make sure that data transfer is efficient and that the code never gets stuck or stops functioning. Since I am planning to one day launch my own CubeSat proposal, this is extremely useful knowledge for me to use in my future project. I also had the chance to learn a lot from Mr. Pugsley. He taught me how to test and troubleshoot, and how to use the CNC machine and other tools. I learned about space-grade vs. non-space-grade materials, and working with CAD and CAM software to design the pieces we need.
The Flip-Sat payload is mostly complete now, and we have a working prototype that functions with the TROOP emulator. I will be spending the next few days focusing on optimizing the code, making it more robust and improving the efficiency of telemetry transmission. The FlipSat-1 is set to launch in January of 2024 on NSL’s next TROOP mission, and after all this hard work I can’t wait to see it going to space.