Ionic Liquids in Space Technology – Current and Future Trends

Abstract

The space technology industry has been at the forefront of technological innovation since the late 1950s. In recent years, ionic liquids (ILs) have gained increasing attention in a wide range of space‐related applications, due to their advantageous properties such as non‐volatility and wide liquid temperature range. In particular, the ability to design ILs with optimal physical and chemical properties for a given application has allowed them to be employed in a wide range of studies. In this review paper, an overview of ionic liquids and their properties in the context of space technology applications is given. Recent studies into the use of ionic liquids in space propulsion, space lubrication, thermal control, composite materials, space telescopes, and life support systems are reviewed and discussed. Furthermore, where applicable, the potential future trends for ILs in space applications are highlighted.

Ionic liquids: a brief history

“…It seems that Ken Seddon and the other advocates of ionic liquids were right and today there are myriad areas of science in which ionic liquids have been applied. They have even found applications in space (Nancarrow and Mohammed 2017 )!…”

Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation

“…This research has led to a wide range of potential applications, such as replacements for volatile organic compounds (VOC) industrial solvents [ 3 ], catalysis [ 4 ], heat transfer fluids and other energy applications [ 5 ]. However, while some of these developments have resulted in industrial use, such as in gas processing [ 6 ], catalysis [ 7 ], and even applications in space technology [ 8 ], their uptake on a commercial scale has been inhibited by specific barriers. The first major barrier is their prohibitively high cost, which often limits their use to niche, high value-added applications.…”

Friction and Wear of Pd-Rich Amorphous Alloy (Pd43Cu27Ni10P20) with Ionic Liquid (IL) as Lubricant at High Temperatures

“…Ionic liquids (ILs) have attracted significant attention as effective lubricants because of their unique properties such as high 2 of 14 thermal stability, non-flammability, high viscosity, miscibility with organic compounds, and negligible vapor pressure [2][3][4][5][6]. These special properties of ILs make them potential lubricants under extreme conditions experienced in applications, such as internal combustion engines, turbines, hydraulic systems, compressors, transmissions, bearings, and aerospace applications [2][3][4][5][6][7][8][9].…”

“…ILs are room-temperature molten salts that consist of cations and anions [4][5][6][7][8][9][10]. It has been established that when ILs are applied to metal surfaces as lubricants, the inorganic anions make strong bonds with an exposed contact surface, and the cations form a layer over the anions, thereby forming an ordered layer structure [8][9][10][11][12]. These ordered layers separate interacting surfaces and prevent direct solid to solid contacts.…”