Energetics of water in the Solar System

Water is vital for space exploration, from drinking to fuel reformation, and is naturally abundant in the Solar System [1–16]. While in-situ resource utilization (ISRU) requires vastly less energy than transporting resources, the energetics has scarcely been explored besides on Earth and limited analysis on Mars’ vapor. Here, we develop a thermodynamic framework to quantify the energy requirements for resource extraction from 18 water sources on 11 planetary bodies. We find that desalinating saline liquid brines, where available, could be the most energetically favorable option and the energy required to access water vapor can be four to ten times higher than accessing ice deposits. While desalination energetics are highly sensitive to salt concentration, we show that desalination energetics only vary by a factor of 2 with respect to the type of salt present. Additionally, unlike chemical mixtures, the minimum energetics are insensitive to composition in physical mixtures (e.g., ice-regolith and inert vapor mixtures). Additionally, by deriving and computing the equation-of-state for pure water, we extend the least work estimates of atmospheric water harvesting by 94°C lower than previous studies that depend on predetermined databases. The presented approach and data may inform decisions regarding water harvesting, habitation, and resource reformation.

Microstrip Resonant Sensor for Differentiation of Components in Vapor Mixtures

A novel microstrip resonant vapor sensor made from a conductive multiwalled carbon nanotubes/ethylene-octene copolymer composite, of which its sensing properties were distinctively altered by vapor polarity, was developed for the detection of organic vapors. The alteration resulted from the modified composite electronic impedance due to the penetration of the vapors into the copolymer matrix, which subsequently swelled, increased the distances between the carbon nanotubes, and disrupted the conducting paths. This in turn modified the reflection coefficient frequency spectra. Since both the spectra and magnitudes of the reflection coefficients at the resonant frequencies of tested vapors were distinct, a combination of these parameters was used to identify the occurrence of a particular vapor or to differentiate components of vapor mixtures. Thus, one multivariate MWCNT/copolymer microstrip resonant sensor superseded an array of selective sensors.

Maximum Condensable Pressure in a Sealed Container With Arbitrary Temperature Distribution

Pressure vessels and sealed canisters are designed to maintain seal integrity under a maximum internal pressure. When the temperature inside the canister rises, the internal pressure rises accordingly. The presence of condensable liquid-vapor mixtures can create a strong relationship between the pressure and temperature. An isothermal container admits a straightforward thermodynamic pressure calculation; however, large temperature gradients inside the container require complex multiphase conjugate heat transfer calculations to predict accurate pressures. A simplified prediction using the peak internal temperature to find the saturated pressure of the condensable fluid may introduce unrealistic pressures when significant fluid mass exists in a cooler location of the container. This work presents methodology to calculate the pressure of a condensable fluid in a sealed container with large internal temperature differences using a two-temperature approach to predict saturated boiling and superheating of the vapor phase. An arbitrary temperature distribution allows for pressure calculations by considering the expected location of the liquid mass and the peak internal temperature. An enthalpy balance provides the effects of the temperature distribution and the peak pressure condition is easily predicted using the proposed method. This work provides a means to calculate the maximum internal pressure of a sealed container with a condensable fluid without the need for complex multiphase computer modeling.