Zero-g Slosh Model Technology: Knowledge Payload

The Zero-g Slosh Model Technology: Knowledge Payload gathers data to develop accurate prediction models of loads on the propellant tank (e.g., liquid pressure, viscous shear) from non-linear contact line motion. When a spacecraft accelerates, the induced pressure gradient generally dominates capillary effects and slosh behavior is nearly as simple as it is on Earth. This research gathers data on propellant behavior during and after spacecraft movement events in order to develop computer prediction models. The data from this demonstration will develop a simulation technology that could lead to more fuel-efficient designs.

Problem Statement 

Non-linear contact line motion has been known since the 1960s to be able to have a large effect, such as a factor of six, on the fundamental natural frequency (presumably on harmonics too). When acceleration exists for the spacecraft, such as during an orbit-raising burn or a trajectory acceleration or correction burn, the acceleration-induced pressure gradient generally dominates over capillary effects and slosh is nearly as simple as one-g slosh on Earth. Two considerations, one old and one new, create a need for gathering data on the low-g response, such as propellant (or coolant, water, or other liquid in use in a spacecraft) settling after a maneuver or docking event or motion of a robotic servicing vehicle: first, little data exists for this common event in spaceflight and thus few models for computation and design exist, and second, the new trend towards smaller satellites reduces uncertainty from scaling up data from these small fluids payloads to true scale.

Summary of Flight Test
2022-09-12 We have designed, built, and ground-tested an original zero-gravity capillary-dominate fluids slosh experiment to acquire new data for use in developing computer models of non-linear contact line motion in weightlessness. The geometry of the liquid test vessels in the experiment creates a two-dimensional flow field in the build of the liquid mass that permits computation power in modeling to be focused on the contact line region. Such models are important for the design of water management in life support systems, refrigeration loops, and some rocket propellant management or refueling systems.
2023-12-19 This tech maturation payload operated as designed on December 19, 2023 and acquired data from liquid sloshing in the weightlessness of spaceflight, which even 65 years into the space age is an uncommon set of data. All four combinations of liquid properties and wettability of the solid walls of the test vessels produced high-resolution video data of the liquid positioning and motion in zero-gravity. Analysis of the data is underway.

• Improves modeling: Liquid response (i.e., slosh) data gathered during flight will facilitate two-dimensional computational modeling
• Enabling: More precise models will improve design and fuel efficiency
• Innovative: Supports green propellant advancements that will impact small satellites and robotic servicing missions 

Future Customers
• New green propellant systems
• Closed-loop life support missions
• Robotic servicing missions
• Agencies needing simulations including NASA and Department of Defense
• Commercial space organizations

This is early/mid-stage (TRL 6) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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