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Stronger possibilities

Features | January 20, 2017 | By:

Carbon nanofibers and graphene can play a role in constructing Space habitats using robotics.

The use of robotically-assisted additive manufacturing involving a mixture of carbon nanofibers, graphene and other polymer nanocomposites will allow the construction of lightweight and impervious sealant barriers, ultra-strong supports, airlocks and even bulkheads for future Space habitats and colonies within dormant lava tubes found on other worlds. This is what one company’s goal is for the future.

4th Planet Logistics is paving the road to space by working with key companies and individuals to produce specialized robots that can not only explore distant worlds but also can build entire habitations on Mars and on the Moon.

The Mars Lava Tube Pressurization Project (MLTPP) of 4th Planet Logistics is developing technologies and strategies that will enable manned Martian and Lunar colonies and bases utilizing existing ancient lava tubes. From conducting detailed surveys of these lava tubes, remotely and robotically, modeling these natural structures, to developing the robotic systems that will employ robotic assembly and additive manufacturing technologies to construct advanced pressurizable and insulative barrier materials and habitats.

The use of lava tubes

Situated safely underneath the harsh surface of mars, ancient lava tubes have many advantages. They are structurally strong, able to support tremendous weight in the weak gravitational fields found on the Moon and on Mars. Lava tubes are a welcomed refuge from the constant bombardment of cosmic rays and meteors. Furthermore, lava tubes provide thermal shielding from the extreme changes of temperatures that occur on the surface. For instance, the temperatures on Mars can be as low as -200 degrees Celsius (C) and as high as 20 degrees C on some Martian days, or “sols” as they are called. Underground, the temperatures average out to be around -60 degrees C.

Lava tubes are formed when fast moving, low-viscosity basaltic lava flows underneath the surface. These lava flows leave behind a smooth coating of basalt as the lava cools against the rock and form a tube-like structure when the lava flow ceases and exits. Some lava tubes on the Moon are estimated to be large enough to enclose entire cities being a few kilometers in diameter.

By utilizing these pre-existing natural structures and reinforcing the walls using robotically-assisted additive manufacturing, these underground tubes will enable future human explorers a safe haven that can be remotely constructed and outfitted beforehand.

Robots on alien worlds

By incorporating robots with 3D printing and additive manufacturing ability, entire habitations can be built years in advance. Lava tubes can be reinforced and sealed to enable pressurization of a breathable atmosphere and insulated to support life. Robots can be sent in droves many years before a single human sets foot on Mars. This will enable the construction of habitats prior to any manned mission. The robots can explore and survey lava tubes, construct barriers, insulate walls, and even build rooms and underground buildings.

By using robot swarms, smaller robots can be mass produced to work as a team in concert. Much like ants, these robots can tether together and overcome many obstacles. Teams of these robots can work continuously, constructing structures using the plentiful materials found on the Moon and on Mars. Swarms of robots can also form a moving network and act as a single entity through the use of distributed computing.

Additive manufacturing on Mars

Concept design of a spider-like robot using advanced manufacturing creating a sealable barrier on the inside of a lava tube on Mars for future human habitation. The material shown is a network of epoxy resins, polymer meshes, graphitic nanofibers, and diamond nanothreads upon a graphene base layer. Image provided by Jonathan Fosdick.
Concept design of a spider-like robot using advanced manufacturing creating a sealable barrier on the inside of a lava tube on Mars for future human habitation. The material shown is a network of epoxy resins, polymer meshes, graphitic nanofibers, and diamond nanothreads upon a graphene base layer. Image provided by Jonathan Fosdick.

Currently, other ways to produce graphene and other carbon nanometers are being investigated by 4th Planet Logistics. These will lower mission costs by eliminating the need to transport raw materials and chemicals from the Earth to distant worlds. This would solve many problems by using available and plentiful materials on these alien worlds, thus reducing payload weight and mission costs.

Basalt, regolith and other minerals could be used, as well, to create various support structures using robots via 3D printing much in the same way houses and even hotels are being printed on Earth with concrete and volcanic ash. However, in order to manufacture the materials needed to construct barriers and sealable living quarters, advanced polymers and nanomaterials will be needed.

Solar-powered units on the surface of Mars would be able to melt and convert the abundant Martian carbon dioxide using electrochemistry to form various chemical precursors along with Martian water. The reduction of carbon dioxide would allow the facile manufacturing of key chemicals, such as ethanol and methanol. These chemicals can be produced via the reduction of carbon dioxide using nitrogen-doped graphene quantum dots along with photocatalysts and/or copper oxide electrodes in solution.

The synthesis of basic chemicals in turn could be utilized to produce other chemicals, such as benzene and ethylene oxide, in order to make various polymers and nanomaterials, such as diamond nanothreads.

Diamond nanothreads are one of the strongest materials known to man. They are stronger than carbon nanotubes. They are extremely lightweight and can be used to reinforce materials, form nanofiber meshes and polymer composities. To make these nanothreads, benzene is slowly pressurized before the pressure is lowered and extruded through specially designed microchannels attached to the robot. Under specific reaction conditions, these nanothreads are easily produced.

These microchannels would allow the robot to produce not only diamond nanothreads but also graphitic nanofibers, which, when used in conjunction with epoxy resins and other polymers, would create robust composite materials, barriers and other structures using advanced additive manufacturing principles.

When incorporated with electrospinning techniques, these robots can exude various polymers and other nanomaterials to create composite nanofiber meshes along with the carbon nanofilaments. Impervious membrane layers can be produced by thermally annealing a spray-coated layer of graphene. Graphene, for instance, can be made entirely on Mars by burning magnesium within solid blocks of frozen carbon dioxide.

The robot can control the material’s location, composition and nanostructure to make many different kinds of barriers, foams, structural supports, and even devices such as solar panels and batteries.

Inflatable structures can also be formed and assembled by the same robots, which can also seal these and connect it to other 3D printed structures.

Applications back home on Earth

The use of robots to crawl into tight and dangerous places to build walls and supports has many applications here at home. Search and rescue missions, mining disasters, earthquake relief and deep-sea exploration are just a few areas that can benefit from such a robotic technology.

The use of robotic additive manufacturing and 3D printing of nanomaterials, nanofiber meshes and various composites in industry here on Earth are broad. Materials and even fabrics can be simply printed consisting of a varying composition, custom tailored to a specific use and application.

Imagine producing a self-cleaning, antimicrobial, smart textile with a single robotic platform. Any material that can be custom designed and produced on the spot which has demanding performance, resiliency and functionality would open the doors to advanced 3D printed textiles and other materials – eliminating many steps in manufacturing and reducing costs.

Jonathan Fosdick is a member of the Nanotechnology Advisory Board, 4th Planet Logistics.

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