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Research Papers

Defining a Discretized Space Suit Surface Radiator With Variable Emissivity Properties

[+] Author and Article Information
Christopher J. Massina

Aerospace Engineering Sciences,
University of Colorado Boulder,
429 UCB,
Boulder, CO 80309
e-mail: christopher.massina@colorado.edu

David M. Klaus

Aerospace Engineering Sciences,
University of Colorado Boulder,
429 UCB,
Boulder, CO 80309
e-mail: klaus@colorado.edu

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF THERMAL SCIENCE AND ENGINEERING APPLICATIONS. Manuscript received February 21, 2015; final manuscript received July 4, 2015; published online August 12, 2015. Assoc. Editor: Steve Cai.

J. Thermal Sci. Eng. Appl 7(4), 041014 (Aug 12, 2015) (9 pages) Paper No: TSEA-15-1048; doi: 10.1115/1.4031132 History: Received February 21, 2015

Heat rejection for space suit thermal control is typically achieved by sublimating water ice to vacuum. Converting the majority of a space suit's surface area into a radiator may offer an alternative means of heat rejection, thus reducing the undesirable loss of water mass to space. In this work, variable infrared (IR) emissivity electrochromic materials are considered and analyzed as a mechanism to actively modulate radiative heat rejection in the proposed full suit radiator architecture. A simplified suit geometry and lunar pole thermal environment is used to provide a first-order estimate of electrochromic performance requirements, including number of individually controllable pixels and the emissivity variation that they must be able to achieve to enable this application. In addition to several implementation considerations, two fundamental integration architecture options are presented—constant temperature and constant heat flux. With constant temperature integration, up to 48 individual pixels with an achievable emissivity range of 0.169–0.495 could be used to reject a metabolic load range of 100 W–500 W. Alternatively, with constant heat flux integration, approximately 400 pixels with an achievable emissivity range of 0.122–0.967 are required to reject the same load range in an identical external environment. Overall, the use of variable emissivity electrochromics in this capacity is shown to offer a potentially feasible solution to approach zero consumable loss thermal control in space suits.

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References

Figures

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Fig. 1

Representative response to state variation and continuous thermal state averaging heat dissipation schemes

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Fig. 2

The EMU and one constant temperature radiator integration concept. (Space suit image credit: NASA). Integration scheme modified from Ref. [13].

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Fig. 3

Mechanical counter pressure suit concept and constant flux concept. Space suit image credit: Professor Dava Newman, MIT. (Used with permission–Illustration: Cam Brensinger.) Integration scheme modified from Ref. [13].

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Fig. 4

Example of intermediate emissivity settings achieved with a variable potential source

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Fig. 5

Example of effective net emissivity values achieved by high–low state mixing

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Fig. 6

Space suit radiator surface area scaled to a cylinder approximation

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Fig. 7

Cylinder area approximation's interactions with the lunar pole environment. A, B, C, and D correspond to β angles at 90 deg increments starting with A =  0 deg

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Fig. 8

Radiative power distributions across suit segments, 293.72 K (69.02 °F)

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Fig. 9

Radiative power distributions with variation in emissivity and radiator temperature

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Fig. 10

Suit temperature requirements for constant flux segment dissipation, 300 W

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Fig. 11

Emissivity setting requirements for constant flux at a lunar pole at 300 W of constant dissipation

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Fig. 12

Emissivity setting requirements for constant flux in lunar pole environment

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Fig. 13

Allowable total emissivity variations for thermal comfort

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