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GW Johnson is working on elements of design of an on-orbit fuel depot.
This is a very large subject with many components.
The physics of behavior of fluids (cryogenic or not) will govern the design of systems to provide refueling services in orbit.
This topic is offered for NewMars members who might wish to contribute to a collection of knowledge on this topic.
The lead off post (#3) will be a search by Google's Gemini for videos on the subject.
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This post is reserved for an index to posts that may be contributed by NewMars members over time.
Index:
Post #3: Gemini on search for videos about fluid in microgravity
In the absence of gravity, forces of adhesion and cohesion dominate
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This post contains a transcript of an exchange with Google's Gemini about fluids in microgravity.
The suggestion to study ISS experiments seem particularly relevant.
Conversation with Gemini
Hi Gemini! This is primarily a request for assistance with a search. I am hoping you might be able to find video of real observations or animations of cryogenic fluid flow in microgravity. I am attempting to assist an engineer designing a tank to hold cryogenic fluids, and able to deliver the fluid efficiently to an external destination. The engineer does not have experience in this field, so the design is currently based upon speculation. I'm hoping that someone has published in this area. My main concern is that the forces of adhesion and cohesion may dominate, since gravity is out of the environment. Our engineer is hoping that rotation of vanes inside the tank will cause fluid to flow in desired directions. If you can find OpenFOAM models of this phenomenon, that would be helpful.
Hello! I can certainly try to help you find videos and models related to cryogenic fluid flow in microgravity. This is a fascinating and important area for space technology.
Based on my search, here's what I've found that might be useful for you:
Videos of Cryogenic Fluid Flow in MicrogravityScienceCasts: The Strange Way Fluids Slosh on the International Space Station: This NASA video shows how water (used as an analog for some propellants) behaves in the microgravity environment of the ISS. It demonstrates fluid sloshing and bubble formation, which are relevant to understanding cryogenic fluid behavior.
Update: I was unable to find this video (Running on Empty) due to the presence of a movie by that name.
Running on Empty: Unsolved Problems in Microgravity Fluid Management: This video discusses experiments with propellant tanks in microgravity, showing how liquids settle into equilibrium shapes adhering to the tank walls due to surface tension, leaving a void in the center. It also touches upon Propellant Management Devices (PMDs) that use capillary forces to manage liquid.
Gas stations in zero gravity: Purdue experiment establishes foundational science for cryogenic fuel depots in space: This describes a Purdue University experiment on a parabolic flight studying cryogenic liquid nitrogen flow boiling in microgravity, with high-speed video of the boiling flow structure.
While these videos may not be exclusively about flow induced by internal mechanisms like rotating vanes, they do illustrate the fundamental behavior of fluids, including those with properties similar to cryogens, in a microgravity environment where surface forces dominate. Observing how these fluids naturally behave will likely be informative for your engineer's design considerations.
OpenFOAM Models and ResearchSeveral research papers discuss using OpenFOAM to model fluid behavior in microgravity, including cryogenic liquids:
One paper, "On the capillary rise of cryogenic liquids in microgravity: numerical analysis and experiments," uses OpenFOAM's Volume of Fluid (VoF) solver to analyze capillary action, which is a dominant force in microgravity and relevant to how cryogenic fluids might behave in a tank.
Another paper, "Evaluation of different interface-capturing methods for cryogenic two-phase flows under microgravity," benchmarks different interface-capturing methods in OpenFOAM for two-phase flows of cryogens where surface tension is significant.
The paper "OpenFOAM Simulations of Late Stage Container Draining in Microgravity" uses OpenFOAM to model capillary-driven draining of liquids in microgravity, which could be relevant to the efficient delivery of cryogenic fluids.
A thesis titled "Pressurization Behavior of a Cryogenic Propellant Tank in Microgravity" also utilizes OpenFOAM to simulate the pressurization process of nitrogen in microgravity, looking at factors like diffuser design.
These resources indicate that OpenFOAM is indeed being used to model fluid dynamics relevant to cryogenic fluid management in microgravity. You might find valuable insights into how to approach modeling your specific tank design within this framework by exploring these papers. They often discuss the numerical methods used (like Volume of Fluid) which are crucial for simulating multiphase flows with free surfaces, as you would have with a liquid cryogen and its vapor.
General Considerations for Cryogenic Fluid Management in Microgravity
In microgravity, the absence of buoyancy and sedimentation means that surface tension, wetting forces (adhesion), and cohesion become much more significant in determining fluid behavior. This can lead to phenomena like:
Wetting and Spreading: Liquids tend to creep along surfaces they wet.
Capillary Action: Fluid movement in narrow spaces due to the interplay of adhesive and cohesive forces.
Sloshing: Movement of the liquid within the tank due to external accelerations (even small ones).
Vapor Formation and Management: Boiling can occur even without significant heating due to the lack of hydrostatic pressure, and managing the vapor (ullage) is critical.The idea of using rotating vanes to induce fluid flow is interesting. In microgravity, this might indeed create some directed motion through viscous drag and by influencing the liquid's contact with the vanes. However, the overall effectiveness would likely depend on the speed of rotation, the geometry of the vanes and the tank, and the fluid properties (viscosity, surface tension). You might need to consider how this induced flow interacts with the natural tendencies of the fluid in microgravity, such as its tendency to adhere to surfaces.
I hope this information is a helpful starting point for you and the engineer you are assisting. If you have more specific questions, feel free to ask!
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This post is about one of the videos suggested by Gemini in Post #3
https://phys.org/news/2015-02-video-str … ional.html
This video shows experiments conducted on the ISS.
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This is a followup in an attempt to discover information that might exist about materials better suited for use as a vane inside a cryogenic tank than others. While this high level search was not productive, there were a couple of hints that might be useful.
Conversation with Gemini
Hi Gemini! Thank you for your assistance with many previous questions. This one is a follow up to our earlier correspondence about on-orbit cryogenic fluid behavior, in the context of refueling operations. You provided links to videos about observations of fluid behavior at the ISS (and other similar videos). This question is about choosing materials that resist adhesion between cryogenic fluids such as oxygen, methane and hydrogen. The question arises in the context of a moving vane inside a delivery tank. Please see if you can find any data that might be published about adhesion at the temperatures where these materials are liquid, and gravity is near zero.
Hi Gemini! It's great to continue our discussion on cryogenic fluid behavior. You're asking about materials that resist adhesion with cryogenic fluids like oxygen, methane, and hydrogen in near-zero gravity conditions, specifically for a moving vane inside a delivery tank. This is a very interesting and complex problem due to the combined effects of extreme temperatures and microgravity.
Finding directly published data on the adhesion of these specific cryogenic fluids to various materials in near-zero gravity might be limited, as these are specialized conditions. However, we can look at related information on:
Materials known for low adhesion or release properties at cryogenic temperatures.
Studies on the behavior of these cryogenic fluids with different surfaces.
General principles of adhesion and how they might be affected at cryogenic temperatures and in microgravity.Here's what I've found that might be relevant:
General Considerations for Low Adhesion at Cryogenic Temperatures:
Polymers: Some polymers, particularly fluoropolymers like Polytetrafluoroethylene (PTFE or Teflon), are often used in cryogenic applications due to their low coefficient of friction and generally low adhesion properties. They are known for their chemical inertness and ability to withstand a wide range of temperatures.
Surface Finish: A very smooth surface finish generally reduces the contact area and thus can lower adhesion.Specific to Cryogenic Fluids:
The primary concern with cryogenic liquids and surfaces is often frost formation from condensation of air moisture, which can then freeze and cause adhesion. Materials with low thermal conductivity might help in reducing this.
Adhesion due to direct freezing of the cryogenic fluid to the surface is also a possibility, though perhaps less likely with materials that don't readily form strong chemical bonds with the fluid molecules.What the Search Results Indicate:
One search result mentions that at cryogenic temperatures, the cold surface of equipment and piping can cause the skin to stick and tear upon removal, highlighting that adhesion can be a concern with various materials at these temperatures.
Another result discusses adhesives for cryogenic applications, noting that many become brittle at these temperatures, which is a different aspect but indicates the temperature's impact on material properties related to bonding.
There's a focus in some results on materials for cryogenic tanks and the bonding of insulation, where adhesion is desired with adhesives, but this is the opposite of what you're looking for.Lack of Direct Data:
I haven't found specific studies quantifying the adhesion forces between liquid oxygen, methane, or hydrogen and various materials in a microgravity environment. This kind of data would likely come from specialized experiments conducted in space or simulated microgravity.
Potential Approaches:
Given the lack of direct adhesion data under your specific conditions, the best approach might be to:
Consider materials known for low adhesion at cryogenic temperatures (like PTFE).
Investigate the wettability of these cryogenic fluids on different materials. Low wettability often correlates with lower adhesion.
Look for studies on cryogenic fluid handling in microgravity that might mention material choices to minimize sticking, even if not quantifying adhesion directly.It's possible that experimental data on this specific topic is proprietary or exists within specialized aerospace research.
Do you have any specific materials in mind that you'd like to know about? Knowing that might help me narrow down the search.
Thank you for taking a preliminary look at the public facing resources at your disposal. While the results at this high altitude level are (apparently) minimal, it is possible that a deeper level of search would have better results. Thanks for giving the question a try.
You're welcome! I understand that the initial search didn't yield the specific, in-depth data you were looking for regarding adhesion of cryogenic fluids to materials in microgravity.
To try a deeper search, I will refine my queries to be more targeted. I'll focus on combinations of keywords like:
"cryogenic fluid adhesion" + "microgravity"
"liquid oxygen adhesion" + "materials" + "space"
"liquid hydrogen sticking" + "tank materials" + "zero gravity"
"cryogenic propellant wetting" + "low adhesion surfaces"Let me run these more specific searches. I'll let you know what I find.
Thanks for your patience while I conducted a more focused search. While direct quantitative data on the adhesion forces of liquid oxygen, methane, and hydrogen to specific materials in microgravity remains elusive in publicly available resources, I did find some related information and concepts that might be helpful:Key Concepts and Potential Strategies:
Surface Tension Devices: In microgravity, surface tension becomes a dominant force for fluid management. Spacecraft propellant tanks often use devices like vanes, galleries, sponges, and screens to control liquid propellant location. These devices rely on the principle that liquids tend to adhere to surfaces, and their design encourages the liquid to move towards desired collection points while preventing gas ingestion.
Wetting and Non-Wetting: The degree to which a liquid "wets" a surface (forms a contact angle less than 90 degrees) is related to adhesion. Lower wetting generally implies lower adhesion. For your moving vane application, a material that is poorly wetted by the cryogenic fluids of interest might exhibit lower adhesion.PTFE (Teflon): As mentioned before, PTFE is known for its low surface energy, which generally leads to poor wetting and low adhesion for many substances, including some cryogens. Its use in cryogenic applications for seals and other components suggests it might be worth considering for a low-adhesion vane.
Surface Finish: A very smooth, non-porous surface can minimize the contact area and potential for mechanical interlocking, thus reducing adhesion.
Insights from the Search Results:
One paper discusses "propellant management devices" (PMDs) which use surface tension to manage cryogenic propellants in microgravity. This highlights the importance of material-fluid interactions (like adhesion and wetting) in space applications.
Another paper mentions that for cryogenic liquid acquisition devices, material compatibility is a key factor. While it doesn't directly address low adhesion, it underscores that the choice of material interacting with the cryogen is crucial.
The concept of "no-vent filling" for liquid hydrogen in microgravity aims to avoid issues related to gas-liquid distribution, which can be influenced by how the liquid interacts with the tank walls.
In summary:
While I haven't found specific adhesion coefficients for your exact scenario, the principles of surface tension, wetting, and the use of materials like PTFE in cryogenic systems suggest that materials with low surface energy and those that are poorly wetted by liquid oxygen, methane, and hydrogen would likely exhibit lower adhesion. A smooth surface finish would also be beneficial.
To get more specific data, you might need to look into specialized material science studies focused on the cryogenic temperatures of these fluids or potentially consult with experts in cryogenic fluid management for aerospace applications.
Do you have any other questions or would you like to explore the properties of specific materials further in this context?
Let's pause here. Thank you for providing an overview of the subject. While I'm away, best wishes for success as you attempt to help your many customers
Understood. Thank you for the conversation so far. Best wishes to you as well! Feel free to reach out again when you're ready to continue.
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Update 2025/05/27:
This link points to an article by GW Johnson about a fuel depot in LEO....
The article is updated to reflect his recent work in a method of exporting cryogenic fluids from tanks.
https://www.dropbox.com/scl/fi/bzall273 … lex5b&dl=0
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