Microgravity Science Glovebox / ISS Research Program
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Zero Boil-Off Tank Experiment (ZBOT)


  • ZBOT research will aid the design of long-term storage systems for
    cryogenic fluids. Simulated by Perfluoro-normal-Pentane (P-n-P).
  • Obtain 1-g and microgravity two-phase flow data for pressure control
    through mixing and active cooling.
  • Verify and validate a Computational Fluid Dynamics (CFD) model for
    cryogenic storage in 1g and microgravity.
  • Use data and CFD model to assess and optimize cryogenic liquid storage
    design concepts.


  • Reduces launch mass and decreases risks through enabling design
    concepts for long-term storage of cryogenic fluids.
  • Cost effective and reliable cryogenic storage for both life support and
    propulsion systems satisfying the requirements for long term mission
    scenarios from Moon to Mars and beyond.

Development Approach

  • Ground phase: develop ground-based experiment and obtain 1-g data for
    tank pressurization and pressure control.
  • Flight phase: develop ISS experiment and obtain microgravity data for tank
    pressurization and pressure control.
  • Develop a state-of-the art two-phase CFD model for tank pressurization and
    pressure control.
  • Validate and Verify (V&V) the CFD model with microgravity and 1g data.
  • Use the validated CFD model and empirical correlations derived from the 1g
    and microgravity data for scale-up tank design.

Flight Operations Summary

The following general steps are taken to prepare the tank before each test run in order to ensure that the tests are all started from a common initial state:

  • Set the jet temperature to the desired initial fluid temperature.
  • Set jet flow rate so that fluid will be well mixed.
  • Continue to run the jet until:
  • All thermal gradients have sufficiently decayed (i.e. until all thermistor temperatures are within +/- 0.25 oC of each other).
  • All thermistors are within +/- 0.25oC of the desired starting temperature.
  • Turn on the heater power supply and set desired heat input.
  • Configure the data acquisition system to record desired.

Brief descriptions of the microgravity test categories

  1. Self-Pressurization Tests: Isolate test cell from mixing/cooling loop by valving off the jet inlet and the tank outlet. At time = 0, turn on the heater and record measurements. After a prescribed pressurization time, turn off the heaters and go back to step #1 to prep the tank for the next run.
  2. Mixing Tests: Set desired jet speed. At time = 0, turn on the heaters allowing the tank to pressurize for a specified time period. After the pressurization time has elapsed, turn on the jet and continue to run until either the maximum allowable mixing time has elapsed or the tank pressure has returned to the initial pressure for this particular experimental run. Turn off the heaters and jet and go back to step #1 to prep the tank for the next run.
  3. Subcooled Jet Cooling/Mixing Tests: Specify heater power, jet inlet temperature and jet speed. Specify whether jet will be active during the entire run or whether an initial pressurization will occur. For mixing throughout, at time = 0, turn on the jet and heaters. After a specified elapsed time, turn off the jet and the heaters and return to step #1. For an initial pressurization, at time = 0, turn on the heaters allowing the system to pressurize. After the pressurization time as elapsed turn on the jet. Continue until either the maximum allowable mixing time has elapsed or the tank pressure has decayed to the initial pressure. Turn off jet and heaters and return to step #1.

Data to be taken during the course of experiment operations

  • Tank Pressure
  • Heat Powers
  • Temperature at all locations (inside and outside)
  • Ullage position
  • Inlet Jet Temperature
  • Tank Outlet Temperature
  • Jet Flow Rate
  • Gravitational Acceleration Data
  • Velocity Field Visualization-PIV

Tank Assembly


Contacts at NASA Glenn Research Center
Project Manager: William Sheredy, NASA GRC

Project Scientist: Dr. David Plachta , NASA GRC


Principal Investigator: Dr. Mohammad Kassemi, NCSER/GRC


Co-Investigator: Dr. David Chato, NASA GRC

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ZBOT Related Documents
small acrobat icon   ZBOT Overview Chart
small acrobat icon   ZBOT-2 Overview Chart
small acrobat icon ZBOT Short Overview Presentation
small acrobat icon ZBOT SRD
small acrobat icon   A Tank Self-Pressurization Experiment Using a Model Fluid in Normal Gravity
small acrobat icon   A Numerical Study of Tank Pressure Control in Reduced Gravity
small acrobat icon   Validation of Tank Self-Pressurization Models in Normal Gravity
small acrobat icon   On the validity of purely thermodynamic descriptions of two-phase cryogenic fluid storage
small acrobat icon   Pressure Control of Large Cryogenic Tanks in Microgravity
small acrobat icon   Self-Pressurization of Large Spherical Cryogenic Tanks in Space
small acrobat icon   Publications & Presentations

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Tim Reckart
NASA Official: Thomas St. Onge
Last Updated: February 3, 2011
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