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.

Extravehicular activity (EVA) will play an important role as humans begin exploring Mars, which, in turn, will drive the need for new enabling technologies. For example, space suit heat rejection is currently achieved through the sublimation of ice water to the vacuum of space, a mechanism widely regarded as not feasible for use in Martian environment pressure ranges. As such, new, more robust thermal control mechanisms are needed for use under these conditions. Here, we evaluate the potential of utilizing a full suit, variable emittance radiator as the primary heat rejection mechanism during Martian surface EVAs. Diurnal and seasonal environment variations are considered for a latitude 27.5°S Martian surface exploration site. Surface environmental parameters were generated using the same methods used in the initial selection of the Mars Science Laboratory's initial landing site. This evaluation provides theoretical emittance setting requirements to evaluate the potential of the system's performance in a Mars environment. Parametric variations include metabolic rate, wind speed, radiator solar absorption, and total radiator area. The results showed that this thermal control architecture is capable of dissipating a standard nominal EVA metabolic load of 300 W in all the conditions with the exception of summer noon hours, where a supplemental heat rejection mechanism with a 250 W capacity must be included. These results can be used to identify when conditions are most favorable for conducting EVAs. The full suit, variable emittance radiator architecture provides a viable means of EVA thermal control on the Martian surface.

In this paper, a transient thermal simulation approach is used to characterize the heat flux and heat flux rates between the lunar surface and a moving spacesuit model. Five different lunar-surface settings are simulated with craters and boulders at three solar elevation angles (θ 2, 10, 90 deg). Heat fluxes and rates are evaluated for different parts of the suit and different characteristic tasks along a given path. The simulated paths are based on Apollo mobility studies. The results indicate that, at lower solar elevation angles, which imply lower lunar-surface temperatures, the thermal impact of surface features becomes more pronounced. In all simulated cases, and for more than 85% of the time, the infrared heat fluxes vary at rates below 20 W · m −2 · s −1 . The incidence versus magnitude of infrared heat flux rates follows a power law with a negative exponent. Smaller heat flux rates have a higher occurrence at lower surface temperatures, and vice versa. The created lookup tables with task, solar elevation angle, and incident heat fluxes can be used as a baseline in the design and sizing of thermal control hardware for moving objects on the surface of the Moon. Nomenclature

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Many bodies in the solar system have features which could conceivably have been formed by a grazing impact with a comet or asteroid. We present the results of deterministic computer simulations of various objects striking a terrestrial planet at a grazing angle. The system is modeled using a combination of the Material Point Method (MPM) and classical planetary dynamics. The impact exhibits three distinct regimes: (i) the initial stage where rapid ejecta leaves the planet in a nearly straight line, (ii) the intermediate stage where the ejecta begins to curve in towards the planet and the trench is being created on the surface and the (iii) the long term stage where the trench is created and any paths exhibited by the ejecta are stable capture orbits. In the case of Mars, we show that a grazing impact can not only dig a trench which has the same general morphology as Valles Marineris but also can create ejecta which orbits the planet at distances comparable to those for current Martian satellites.