In-Situ Resource Utilization (ISRU)

Material Types

The Mars Incubator construction relies heavily on materials produced from the Martian surface. Regolith is found in the form of Martian sand, Basalt is the bedrock found underneath, and polyethylene, whilst not naturally occurring, can be produced by combining CO2 and hydrogen.

Equipment Required

A processing plant will be required to prepare the materials for use in the construction of the Habitat. The plant consists of two material flows, one for the production of plastic, the other for the processing of the regolith and basalt.

For resource gathering and habitat assembly an excavator will be brought with different attachments including a bucket, vice, precision manipulator and a printhead.

Additional equipment that will need make the trip include molds, advanced electronics, a laser cutter, a heated press, and a kilopower installation. All the exterior panels, interior panels, support structures, and the connecting devices are made from Martian materials.

Process

The first step in production is to produce polyethylene for use in most of the pressure retaining and structural parts of the habitat. To do this, water-laden regolith or water-ice is collected and loaded into the hopper, sifted, and fed into the furnace. It is heated to remove any water, which collected and stored.

The water is then electrolyzed to isolate the H2. The O2 can be stored for crew use after production.


Conceptual Design

The H2 is combined with C02 from the atmosphere over a copper catalyst to produce CO and more water. The water is recycled, and the CO is hydrogenated over an iron-based catalyst to produce ethyne and water. Again, the water is recycled and the ethyne is polymerized to produce the polyethylene. The regolith tailings produced from this process can be stored later for backfill.

Raw polyethylene is used to make 4 items: exterior panel anchors, backplates, trim, and tensioning devices. They all use different molds but the same process of pouring polyethylene powder, heating until fused, and letting it cool.

Production of an exterior panel requires all three materials. Regolith, basalt, and polyethylene. Basalt fiber is used as a reinforcement against pressurization. To process it, it’s dumped into the collection hopper where it is pulverized into feedstock. It’s then fed into the furnace to ensure it’s free of H20 and then continues into the fiber machine. Here, the material is melted and drawn through a platinum rhodium bushing into small diameter fiber that is cooled and wound around a bobbin. These fibers are then wound around anchor points placed in the mold as well as used for feedstock for the laser print head.

Conceptual Design

The bulk of the panel material is a regolith-polyethylene mixture. Regolith dried in the furnace bypasses the Fiberizer and is fed directly into the mixing hopper with the polyethylene powder. With the trim in place, this mixture is poured into the mold, over the basalt fiber that we’ve already wound. The backplate is placed on top. The last steps require heating and compressing the materials, allowing the newly formed panel to cool, then removing it from the mold. To make different configurations, alternate molds and fiber guides will need to be used as well as cutting out holes where necessary.

External Tiles

The standard building blocks for the habitat are the hexagonal and pentagonal tiles. There are three standard geometries used to complete the habitat, one hexagonal and two pentagonal. The pentagonal tiles in the smaller pentagonal polyhedrons have a different mating angle than the larger tiles but are the same basic size. The large volume of the habitat has 20 hexagons and 12 pentagons, like a typical soccer ball. The smaller volumes are platonic solids made up of 12 pentagons to form dodecahedrons (the common 12-sided die).

All the tiles are made from the same materials, use the same reinforcement technique and are approximately 16 inches thick. Most of the volume of the tiles is a mixture of polyethylene powder and Martian regolith. This material will be pressed into a mold and heated to approximately 130° C. This process melts the polyethylene and regolith mixture to form a composite. The addition of the regolith reduces the amount of the polyethylene required by consuming some of the volume of the molded part. Using the regolith and polyethylene improves compressive strength while maintaining pliability. Other advantages of using polyethylene are that it is effective at shielding against GCR (galactic cosmic rays) and has good wear resistance. Its typical use on Earth as shot peen masking demonstrates its effectiveness as protection against high velocity small particles such as rocket motor ejecta.


Because of the tension force exerted on the tiles when the habitat is pressurized, the tiles need anchoring points to mechanically secure them to each other. To achieve this, the press tool has provisions for basalt fibers to be wound through the internal volume of the tile before the polyethylene and regolith are pressed. An insert, molded from polyethylene, is used to help reduce the bend radius. These windings act as anchoring points to distribute the load throughout the tile and help to strengthen the tiles against impacts. Finally, the border of the tile has polyethylene strip molded into the tile to act as a weld area for sealing the habitat. These features can be seen in the images below. More research on the appropriate mix ration of plastic to sand and fiber is need, additionally, more work is needed on winding patterns.

MEPS Tiles
The Mechanical Electrical Plumbing (MEP) tile is similar to the basic tile in its construction, except for special inserts in the center of the tile. It has all the same features of the standard tile, using the basalt fiber windings and the polyethylene inserts for welding. The same mold tooling can be used to create this tile by utilizing a mold insert to create space in the center of the tile for the MEP inserts. The fiber windings go around the MEP insert and are still used as mechanical reinforcement for the pressure retaining aspect of the structure. The MEP inserts are necessary to provide an avenue for heat exchange of the and provide pass-throughs for electrical, water, and other life support services. A diagram of a MEP tile can be seen below.

Hatchway Tiles
The hatchway tile is very similar to the MEPS tile in construction. An aluminum support structure is used frame the hatchway and bear the tensile load from the panel. The basalt fiber anchors are wound around the aluminum insert, and a molded polyethylene Insert is used to make the seal to the hatchway. The tile is then sintered in the same method as a standard tile. While each of the three smaller cells have a suit hatch tile, it is only used for emergencies in the Bio-Generation and Multipurpose Cells.

Viewport Tiles
The viewport tile is once again constructed in a similar method as the standard tile. It utilizes the same design features as the standard tiles. Using a mold insert, a viewport is added to the center of the tile. The basalt fiber winding wraps around the parameter of the viewport insert. The fiber windings support the insert and help to retain it in place. The viewport tiles are used in the Bio-Generation Cell to allow sunlight into the habitat. A viewport tile can be seen below.

A Greenhouse…on Mars!

The Mars Incubator habitat design has a number of cool features to make a stay on mars bearable. One of my favorites is the greenhouse!

The “Bio-generation” volume will be used to conduct experiments with plant life in the Martian environment. This cell includes 5 view ports to allow sunlight into the habitat, and will have 2 MEP’s (mechanical, electrical, plumbing) units for heating and cooling, as well as a freshwater system independent from the human life support system.


Having plants to tend will be a pleasant diversion for the crew that could result in real scientific development. Additionally, it will help scrub the air, and reduce the isolating affects of the Martian desert environment. The view ports will provide stunning views of the Martian landscape. There is a lot of value in the use of this space because we can achieve scientific results in a crew friendly atmosphere.

To address potential safety concerns, the cell is also fitted with a small hatch to the exterior of the habitat for emergency use only. As with all the secondary volumes, there is reserve oxygen below the deck, making this cell a suitable refuge are in the unlikely event of a rapid depressurization. In fact, it might be one of the most pleasant places in the hab to be stranded for any duration of an emergency!