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ZBOT, ZBOT-NC

Zero Boil-Off Tank (ZBOT, ZBOT-NC)

ZBOT-NC Quad Chart
ZBOT-NC Quad Chart

Rocket fuel, spacecraft heating and cooling systems, and sensitive scientific instruments rely on very cold cryogenic fluids. Heat from the environment around cryogenic tanks can cause their pressures to rise, which requires dumping or “boiling off” fluid to release the excess pressure, or actively cooling the tanks in some way. Zero Boil-Off Tank (ZBOT) uses an experimental fluid to test active heat removal and forced jet mixing as alternative means for controlling tank pressure for volatile fluids.

Investigation on Space Station to Test Minimizing Pressure of Space Travel

ZBOT
ZBOT in the Microgravity Science Glovebox Engineering Unit Work Volume at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

Spacecraft rely on liquids for everything from fuel to life support systems for astronauts. Storing these liquids at the correct temperature and pressure is essential to prevent loss of fluids or failure of a storage tank. Human life in space is a balancing act of reliable systems and meticulous planning.

Rocket fuel and other liquids used in space are stored at cryogenic temperatures of –423 to -243 degrees F. As these liquid cryogens are warmed by the environment, they evaporate, which increases pressures inside storage tanks.

NASA Glenn Research Center’s Zero Boil-Off Tank (ZBOT) experiment on the International Space Station will study ways to relieve that pressure without the loss of fluid. ZBOT launched aboard Orbital ATK’s Cygnus spacecraft on its seventh contracted resupply mission for NASA from… Continued

Research Overview

Description

Space Applications

Long-term storage of cryogenic fluids is necessary for spacecraft propulsion and life support. Scientific sensors aboard space telescopes and other space probes also require operation at cryogenic temperatures, but can only work as long as the cryogenic fluids last. ZBOT carries out small-scale microgravity tests to enable further research for lightweight, efficient and long-duration cryogenic storage in space.

Earth Applications

Cryogenic tanks require complicated storage and flow solutions for fluids that act as both liquid and gas, depending on their temperatures. ZBOT investigates the role of phase change physics and heat transport on the pressure control of these volatile fluids. Results from the investigation improve models used to design tanks for long-term cryogenic liquid storage, which are essential in biotechnology, medicine, industrial, and many other applications on Earth.

Operational Requirements and Protocols

The ZBOT test points are performed at three different fill levels: 70%, 80%, and 90%. The test tank is launched at a fill level of 70%. Particles are then injected into the fluid. The test fluid, P-n-P, is pre-conditioned to a nominal starting point temperature prior to each test. Tests fall into three categories: jet-mixing, subcooled jet mixing, and self-pressurization tests. Once tests are completed, the Fluid Reservoir are used to increase the fluid level in the test to the 80% and 90%. Dissolved gas are removed from the test fluid after each fill adjustment. Also, additional particles are injected to the fluid adjustment. There are a total of 52 test points, 23 each at the 70% and 90% fill levels, and 6 test points at the 80% fill level. Data are downlinked periodically. Return of the hardware is not required for data retrieval.

On-orbit procedures cover the installation of the hardware into the Microgravity Science Glovebox (MSG). During installation the crew must evacuate air from hoses and fill the water loop. The hoses are evacuated using the Microgravity Science Glovebox vacuum exhaust system (MSG VES). The water loop is filled from the ZBOT Water Reservoir. After the hardware is installed, the crew inject particles into the Test Section between 3-5 times. Experimental runs are controlled from the ground.

Gallery

ZBOT Contacts

Project Manager: William Sheredy, NASA Glenn Research Center

Project Scientist: John McQuillen, NASA Glenn Research Center

Principal Investigator: Dr. Mohammad Kassemi, NCSER/GRC

C0-Investigator: Dr. David Chato, NASA GRC

Engineering Team: ZIN Technologies, Inc.

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