Atmospheric Re-entry Energy Storage (ARES)- A Novel concept for utilizing atmospheric re-entry energy

As the aspirational goal of Mars settlement starts to slowly materialize, it is apparent that its viability hinges on the utilization of its energy and material resources. Although Mars has a thinner atmosphere than Earth, it still exerts large amounts of heat on entry vehicles, generating temperatures around ~1500 deg C. Therefore, the entry vehicle is covered with a thick layer of ablative heat shield to protect the inside from reaching undesired temperatures. However, the temperature on the Martian surface is significantly cold. It varies between -140 deg C and 30 deg C. One of the critical challenges in developing a settlement and operating equipment on Mars is to find adequate heat sources on its surface. The envisioned heat sources are solar energy, geothermal energy, greenhouse gases and Radioisotope Thermoelectric Generators (RTG). Although solar and possibly geothermal energy are the preferred sources for their unlimited supply, they are localized and require an elaborate infrastructure. Trapping greenhouse gases also requires extensive infrastructure. RTGs require a large amount of radioactive fuel and both the equipment and fuel have to be transported from Earth. Due to its hazardous nature, disposal/reprocessing of the fuel will be challenging. Interestingly, little to no effort has been spent to study the possibility of utilizing the large heat generated during vehicle entry. This paper proposes a novel concept to collect, store and utilize the atmospheric entry heat energy using Phase Change Materials (PCMs) obtained from the Martian moons. Mars settlement architectures suggest that Phobos and Deimos can be used to set up preliminary base camps. These moons are potentially trapped C-type asteroids and have the possibility to contain rich Lithium reserves. Lithium and its alloys have a relatively high latent heat of fusion and low density, making them an ideal PCM for this application. This concept takes advantage of the undesired heat generated during atmospheric entry to melt the PCMs. A storage system would store and insulate the melted PCM as it solidifies and heat energy is released. The utilized PCM could then be reused and consumed for a variety of purposes. With current technology limitations, the heat storage system could only store the heat energy obtained using PCMs for a few hours. While the results from ongoing research could considerably increase its efficiency, PCMs could be used as a temporary energy source in landing sites where no other energy generation infrastructure is available. Alternatively, the heat generated from PCMs could be converted to electricity using thermoelectric generators.