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Space Test Program - Houston 3 - Massive Heat Transfer Experiment (STP-H3-MHTEX)


Overview | Description | Applications | Operations | Results | Publications | Imagery

Experiment Overview

This content was provided by Andrew Williams, Cecilia Penera, and is maintained in a database by the ISS Program Science Office.

Brief Summary

Space Test Program - Houston 3 - Massive Heat Transfer Experiment (STP-H3-MHTEX) investigates the in space performance of capillary pumped loop (CPL) heat transfer equipment, which uses continuous fluid flow to transfer heat from multiple spacecraft sources to an external radiator surface. This investigation intends to improve the understanding of heat transfer transport phenomena and two-phase flow (i.e., liquid-vapour flow) performance in microgravity. This investigation is one of four on the STP-H3 platform and is located at EXPRESS Logistics Carrier site 3 (ELC-3).

Principal Investigator(s)

  • Andrew Williams, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH, United States
  • Cecilia Penera, Northrop Grumman Aerospace Systems, Redondo Beach, CA, United States
  • Co-Investigator(s)/Collaborator(s)

  • Jeff Nienberg, Northrop Grumman Aerospace Systems, Redondo Beach, MD, United States
  • Laura Ottenstein, NASA Goddard Space Flight Center, Greenbelt, MD, United States
  • Developer(s)

    United States Department of Defense Space Test Program, Johnson Space Center, Houston, TX, United States
    Air Force Research Laboratory, Kirtland AFB, NM, United States

    Sponsoring Space Agency

    National Aeronautics and Space Administration (NASA)

    Sponsoring Organization

    National Laboratory - Department of Defense (NL-DoD)

    ISS Expedition Duration:

    March 2011 - October 2013

    Expeditions Assigned


    Previous ISS Missions

    MHTEX flew as Two Phase Flow (TPF) with different heat pump and capillary loop configurations on STS-85.

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    Experiment Description

    Research Overview

    • Space Test Program - Houston 3 - Massive Heat Transfer Experiment (STP-H3-MHTEX) plans to examine and achieve flight qualification of an advanced capillary pumped loop system that includes multiple parallel evaporators, a dedicated starter pump, and an advanced hybrid evaporator.

    • CPLs are two-phase transport devices that are used in the transporting of heat loads over defined distances with minimal temperature drop across the system.

    • The heat load is acquired through the vaporization of the working fluid within an evaporator and then rejected through external spacecraft radiator systems.

    • Extended operation in the microgravity environment is to be demonstrated, and correlation of performance to ground testing for design and test purposes will be performed.

    • MHTEX further demonstrates that the CPL technology allows many distributed payloads, both internal and external, to be thermally networked together. With the MHTEX CPL technology, radiators can be located separately from high power components, which allow payloads to share common remote radiators in optimal thermal locations.


    The STP-H3-MHTEX investigation features a next generation of spacecraft thermal control technology to measure the on-orbit performance of the capillary pumped loop (CPL) system. MHTEX incorporates enhancement to the original Two Phase Flow (TPF) flight experiment flown on STS-85 by adding a starter pump and advanced hybrid evaporator. With these additional components, MHTEX will demonstrate failure-free start-up, demonstrate performance over a variety of operating conditions, and improve understanding of two-phase flow in a microgravity environment.

    MHTEX CPL components consist of four unique evaporators (heat acquisition) plumbed in parallel with a dedicated starter pump. Heaters that simulate electronic heat loads similar to what is expected on larger satellites are placed on or near each evaporator. The heat is distributed from the multiple evaporators via transport lines which link the evaporators to two parallel condensers. The condensers mounted to variable conductance heat pipes (VCHPs) transport the heat to three fixed conductance heat pipes directly attached to the MHTEX radiators. In addition, a fluid reservoir controls the CPL system temperature and provides fluid management.

    The design implications and on-orbit performance results of this investigation may be used in spacecraft bus designs regarding equipment layouts and system level thermal designs.

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    Space Applications

    The STP-H3-MHTEX investigation provides robust and reconfigurable spacecraft performance information intended to reduce the design and development time and costs of related satellite components with regards to spacecraft thermal regulation. The full STP-H3 complement of investigations, including thermal control, attitude knowledge, and environmental sensing technologies may be used in future spacecraft design and development; each technology offering an increase in efficiency and decrease in cost.

    Earth Applications

    The spacecraft that these technologies apply to include those supporting Earth-bound communications. The improvements that STP-H3- MHTEX intends to demonstrate with regards to thermal spacecraft regulation create for more robust and capable satellites that are used to interface with ground systems.

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    Operational Requirements

    Payload Health, Status and Experiment Data will be downlinked via standard ISS 1553 communications protocols. STP-H3 is a compliment of 4 payloads that share a command window of 4 hours a day throughout the week. TReK is used for commanding and downlinking of data from the payload to the ground. There are 5 remote TReK Payload Operation Control Centers (POCC) that coordinate with the Payload Operations Integration Center (POIC) at MSFC via IVoDS.

    Operational Protocols

    STP-H3 is an external payload that does not require crew internal operations, therefore, direct communication is not required. The TReK operators communicate with the POIC, specifically the Payload Rack Officer (PRO), to be enabled for commanding. The PRO in-turn communicates with the Payload Operations Director (POD) for authorization to command.

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    Results/More Information

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    Related Websites

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    image Two Phase Flow, the precursor to MHTEX, flown on STS-85.
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    image Preflight image showing the location of the STP-H3-MHTEX investigation.
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    image Schematic showing location of the STP-H3-Canary investigation.
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    Information provided by the investigation team to the ISS Program Scientist's Office.
    If updates are needed to the summary please contact JSC-ISS-Program-Science-Group. For other general questions regarding space station research and technology, please feel free to call our help line at 281-244-6187 or e-mail at JSC-ISS-Payloads-Helpline.