NASA - National Aeronautics and Space Administration

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Experiment Overview


Brief Summary

Data from the Capillary Channel Flow (CCF) experiment will help to innovate solutions to transporting liquids (such as fuels, low temperature liquids like liquid nitrogen and water) in microgravity. By understanding capillary fluid flow rates in microgravity, hardware can be developed for "pumping" liquids from one reservoir to another without the need for a pump with moving parts. The reduced cost, weight, and improved reliability of such equipment make this a particularly attractive technology for NASA.

Principal Investigator(s)

Michael Dreyer, Ph.D., University of Bremen, Bremen, Germany

Co-Investigator(s)/Collaborator(s)

Aleksander Grah, University of Bremen, Bremen, Germany

Jörg Klatte, University of Bremen, Bremen, Germany

Mark Milton Weislogel, Ph.D., Portland State University, Portland, OR, United States

Peter Canfield, University of Bremen, Bremen, Germany

Yongkang Chen, Ph.D., Portland State University, Portland, OR, United States

Developer(s)
Information Pending

Sponsoring Space Agency

National Aeronautics and Space Administration (NASA)

Sponsoring Organization

Human Exploration and Operations Mission Directorate (HEOMD)

Research Benefits

Information Pending

ISS Expedition Duration:

September 2010 - September 2013

Expeditions Assigned

25/26,27/28,29/30,33/34,35/36

Previous ISS Missions

ISS Expedition 25/26 was the first operation of CCF in microgravity.

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Experiment Description

Research Overview

• Currently, spacecraft fuel tanks rely on an additional reservoir to prevent the ingestion of gas into the engines during firing. Research is required to update current models, which do not adequately predict the maximum flow rate achievable through the capillary vanes.


CCF tests the theoretical predictions for the free surface shapes and the critical flow velocities for open capillary channel (vane) flows in microgravity. CCF is designed to validate the assumptions used to develop the governing equations. The experiments provide the verifications for the flow rate limits and corresponding critical flow velocities.

Description

Capillary Channel Flow (CCF) is a versatile experiment for studying a critical variety of inertial-capillary dominated flows key to spacecraft systems that cannot be studied on the ground. The results of CCF will help innovate existing and inspire new applications in the portion of the aerospace community that is challenged by the containment, storage, and handling of large liquid inventories (fuels, cryogens, and water) aboard spacecraft. The results will be immediately useful for the design, testing, and instrumentation for verification and validation of liquid management systems of current orbiting, design stage, and advanced spacecraft envisioned for future lunar and Mars missions. The results will also be used to improve life support system design, phase separation, and enhance current system reliability.

Since hydrostatic pressure is absent in microgravity, technologies for liquid management in space use capillary forces to position and transport liquids. On Earth, the effect of capillary forces is limited to a few millimeters. In space, these forces still affect free surfaces that extend over meters. For the application of open channels in propellant tanks of spacecraft, design knowledge of the limitations of open capillary channel flow is a requirement.

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Applications

Space Applications

To enable design of spacecraft tanks that can supply gas-free propellant to spacecraft thrusters, directly through capillary vanes, significantly reducing cost and weight, while improving reliability. Technologies for liquid management in space use capillary forces to position and transport liquids, since the hydrostatic pressure is absent which gives the liquid a defined surface and enables easy withdrawal from the tank bottom. But the effect of capillary forces is limited on Earth to a few millimeters. In space these forces affect free surfaces that extend over meters. For the application of open channels in propellant tanks of spacecrafts, design knowledge of these limitations are a requirement, predicated with a bubble free liquid restriction prior to entering the thrusters.

Earth Applications

Technologies for liquid management in space use capillary forces to position and transport liquids, since the hydrostatic pressure is absent which gives the liquid a defined surface and enables easy withdrawal from the tank bottom. But the effect of capillary forces is limited on Earth to a few millimeters. In space these forces affect free surfaces that extend over meters. For the application of open channels in propellant tanks of spacecrafts, design knowledge of these limitations are a requirement, predicated with a bubble free liquid restriction prior to entering the thrusters.

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Operations

Operational Requirements

Forced liquid flows through open capillary channels with free liquid surfaces will be investigated in the Microgravity Science Glovebox (MSG) onboard ISS. In open capillary channels, if a certain critical flow rate is exceeded, the flow becomes unsteady, the surfaces collapse, and gas ingestion occurs at the outlet. From a fluid mechanical point of view, a characteristic critical velocity must exist at which the steady subcritical flow turns into an unsteady supercritical flow, which involves the collapse of the free surfaces. To find this velocity and the location of collapse of the free surface, the surface profile must be measured with great accuracy. Furthermore, the local flow velocity must be known at dedicated points of the channel.

Operational Protocols

The crew involvement is limited to installation of the CCF hardware in the MSG work volume and exchange of experiment units between sessions.

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Results/More Information

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Related Websites

ISS Research Project - CCF

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Imagery

CCF experimental unit and electrical subsystem, image courtesy of Glenn Research Center.
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