Space exploration has been dreamt of since the first observations of the moon and stars. It has inspired the imagination of humanity and has been a central aspect of many sci-fi stories. Space has also been a motivation to keep pushing the boundaries of science and technology, and with such a high motivation, a plethora of derivatives have arrived in our daily lives, and they can make a high impact in diverse sustainable goals proposed by the United Nations such as innovation, climate change, health, clean water, clean energy, among others. 

Frontier materials have demonstrated great potential to be applied in diverse fields of science and technology and are widely used for space exploration. The derivatives from the research and development of space exploration can create new markets and lead to improved products. Some examples are scratch-resistant lenses, foil blankets, electrolytic silver iodizer for water purification, infrared thermometers, home insulation, memory foam, shock-absorption materials, and many others.

Space exploration needs the development of several technologies for rockets and creating habitats in space stations, satellites and planets. Some of the needed technologies are electromagnetic shielding, thermal insulation, solar energy, water recirculation, robust and lightweight materials, air conditioning, and sensors. As an example, rockets are extremely large and need to carry a huge amount of weight for fuel, cargo, and navigation. A main concern is to balance its mechanical robustness to carry all the weight but be as light as possible to minimize the energy cost to surpass its gravity pull during lift-off. Right now, frontier metal alloys are employed since the infrastructure for their production are already at hand and their cost is still tolerable. A promising alternative are carbon materials that have demonstrated to be among the lightest and strongest materials, take for example, graphene. Graphene has an elastic stiffness up to 1 terapascal for just a single layer of atomic thin carbon. However, there is still much challenge to establish cost effective production at a large scale and keep essential mechanical and electronic properties to send rockets into space.

During a rocket lift-off there is a large amount of heat generated to have enough thrust to overcome gravity pull. This creates the need for insulating frontier materials to protect the rocket that is exposed to a maximum temperature near 3300 C in the combustion chamber of the engine. During winter we tend to think that a fluffy blanket can be best. This is true because they have lower thermal conductivity than solid materials given the air gaps between the blanket fibers. If a material has a highly intricate structure, then the path for heating is longer and could serve better for thermal insulation. In this sense, aerogels are of great advantage. These frontier materials are highly porous that their density is extremely low making them lightweight. Silica and carbon aerogels can be the right materials for this task. Graphene aerogels have demonstrated excellent mechanical stability between -196 and 900 C, proving them as ideal candidates for space exploration.  For this reason, the Parker Solar Probe from NASA entered the Sun’s atmosphere known as corona thanks to the use of carbon foam for thermal insulation.

All spacecraft require energy for transportation and life support if they carry passengers. For this purpose, a renewable energy source is needed. The natural source with the highest amount of energy is the sun and its energy can be harvested and stored to fuel entire cities. Such energy harvesting requires devices with high efficiency to convert solar energy into electrical energy. Typically, solar cells are made of silicon and their costs are constantly decreasing. However, there are frontier materials such as perovskite which can offer a higher efficiency and convert a larger amount of the solar spectrum into energy than conventional silicon based solar cells. Perovskite solar cells are still in development to reduce production cost and increase humidity stability. However, someday a breakthrough may come along and bring perovskite solar cells into the public market.

Water is a vital liquid that needs to be recirculated within a spacecraft and can be done via membrane technology. Among the emerging membrane technologies there are 2D material-based membranes. These membranes can be lightweight, efficient for high separation rate, energy efficient, chemically stable and exhibit excellent antifouling. For example, through forward osmosis, water filtration can be done by keeping a solution with a high concentration of nutrients on one side of the membrane and on the other side wastewater. The concentrated solution of nutrients will attract water to flow through the membrane until both sides of the membrane show the same pressure in the liquids. Thus, without using much energy, wastewater can be recycled by membrane filtration to provide nutritious beverages. A 2D frontier material can be lightweight and by controlling its porosity it can exhibit high separation rate and permeate flux to be implemented for water recycling in space exploration.

The aforementioned are some examples of ways in which frontier materials can be used for space exploration and they can even be used for new human establishments on the moon or Mars, since there are established targets to send humans there. In addition, there are still endless possibilities for frontier material applications. Those that take the challenge may bring leaps in the advancement of frontier materials and make a huge impact in society.

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References:

• https://www.jpl.nasa.gov/infographics/20-inventions-we-wouldnt-have-without-space-travel
• Lee, Changgu, Xiaoding Wei, Jeffrey W. Kysar, and James Hone. Measurement of the elastic properties and intrinsic strength of monolayer graphene. Science 321, 5887 (2008): 385-388.
• https://www.nasa.gov/returntoflight/system/system_SSME.html
• Wu, Y., Yi, N., Huang, L. et al. Three-dimensionally bonded spongy graphene material with super compressive elasticity and near-zero Poisson’s ratio. Nat Commun 6, 6141 (2015). https://doi.org/10.1038/ncomms7141
• https://www.nasa.gov/feature/goddard/2018/cutting-edge-heat-shield-installed-on-nasa-s-parker-solar-probe
• https://www.nanowerk.com/spotlight/spotid=45249.php
• Kang, Y., Xia, Y., Wang, H., Zhang, X., 2D Laminar Membranes for Selective Water and Ion Transport. Adv. Funct. Mater. 2019, 29, 1902014. ‍