Why propellant management is important
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On the left is a video of the interior of the liquid oxygen (LOX) tank of SpaceX's CRS-5 rocket, as it assists a resupply service mission to the International Space Station. Directly after second engine cut off (SECO), you are able to see packets of LOX floating around the tank.
In spacecraft, slosh caused by accelerations, such as lift-off, can form massive propellant slugs, resulting in devastating consequences. Such as Pogo oscillation, which is when unstable combustion in the engine results in variations to propellent pressure and flow rate. This, in turn, causes propellant sloshing, which puts stress on the spacecraft frame and can lead to structural failure. Another problem caused by sloshing is G-jitter which is uncertainty in orientation or attitude. This is a significant concern for satellites which often require a precise position or orientation. |
On the right is a Youtube video published by NASA Johnson discussing how sloshing liquid can lead to gas bubbles trapped in the liquid propellant due to the current "settling thruster" method of forcing the propellant toward the fuel line of the engine. This video also demonstrates how a stationary propellant management device (PMD) is an example of a capillary flow experiment (CFE) to guide propellant via surface tension forces.
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When I joined the MaSC project in June 2020
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The MaSC project originated as a joint-effort between Carthage Space Sciences and Embry-Riddle Aeronautical University. On the left is an image of a model of the MaPMD designed by Embry-Riddle graduate students and woven out of metglas which a cobalt alloy ribbon that has a reported maximum relative permeability of 1 million which allows it to be magnetized and de-magnetized quickly. This MaPMD design is patented by Embry-Riddle.
I was first introduced to this project the semester before my first summer in college. At that time, the experiment had been tested on board a parabolic flight a year prior and the flight footage and data were not aligning with the predicted behavior of the MAPMD. The MaPMD did not suppress any slosh or respond to the external magnetic field produced by the coils. After showing interest in this project, I was accepted to be a WSGC funded research assistant for that coming summer. |
My Investigation and ResultsDuring my first summer, my objectives were to investigate why the predictions and previous flight data were not consistent and if any discoveries were made, then I would be preparing the payload for a parabolic flight. In order to understand why there is a discrepancy between the data and predictions, I constructed an experiment where I could measure the force on the membrane as its position changes with respect to a single coil. As a side note, at this point in my physics career, I was not very familiar with how magnetic fields and corresponding forces operate.
From my force per position experiment, I concluded that the membrane was not interacting the way we expected with the magnetic field because the magnetic field was too week and the woven MaPMD was not thick enough, and the geometry must change in order to most efficiently interact with the magnetic field. |
Designing a new MaPMD
When designing a new MaPMD, I reviewed a paper suggested by my advisor, Dr. Crosby, that derived the on-axis force of a cylindrical steel slug in a solenoid and noticed a relationship between the external magnetic field and the strength of force on the slug. The force on the slug along the axis of the solenoid is proportional to the magnitude of the magnetic field times the change in magnetic field with respect to the spatial change along the axis of the solenoid. While this relationship doesn't seem too revolutionary, at the time I felt like I had an epiphany. It occurred to me that my results from my experiment suggested the same relationship, that where the magnetic field is changing in space, and had a larger magnitude, the force on the MaPMD was greater. This information, coupled with my understanding that magnetic fields get weaker with distance from the source and knowing that changes in field direction is most dense near the source, pointed me in a direction to design a halo-shaped MaPMD. I worked with my peers to get familiar with Autodesk Inventor and designed the membrane that I would test in EM Works before printing and wrapping in Metgals.
Parabolic flight results
The Objective of the flight test is to demonstrate the ability to position the MaPMD using an external magnetic field, measure reduction in slosh amplitude of low-gravity propellant slosh when the MaPMD is activated. For the first time in MaSC project's history, sloshing was successfully suppressed due to the increased force on the halo MaPMD from the magnetic field produced by the coils.
Presenting my work
I've presented my work on the MaSC project at Carthage STEM poster presentation events, as well as at the 2021 Wisconsin Space Conference at Milwaukee School of Engineering (MSOE) both as a poster and as a slideshow presentation.
Reflection
My experience with the MaSC project is one that has shaped my view of research and helped develop my ability to tackle open-ended questions. The work I did as a researcher on the MaSC project demonstrates my ability to apply my problem-solving skills to break down an open-ended question. At the time of joining the MaSC project, I hadn’t taken any classes on electricity and magnetism, so all of the context I needed to grasp before attempting to perform any meaningful research was my first step. As I reflect, this is one of the defining experiences that solidified my decision to earn my undergraduate degree in physics.