Temperature Regulation Inside Martian Craterhabs

(Mars is known as a frozen dead world in popular culture. A screenshot from 2015 movie "The Martian". An astronaut inside a rover braving the extreme cold of the Martian night)

Temperature on Mars

The average temperature on Mars is -60c, with temperature extremes ranging from 21c at midday near the equator to -130c at night at the poles. The extremely thin Martian atmosphere, with pressure averaging around 0.006 bar, offers little to retain daylight heat during the frigid nights, with rapid drop in temperature after sunset. Any future human habitat concept for the red planet must factor this in, and be resilient enough to withhold as much heat as possible to reduce the power required to maintain internal temperature in a comfortable range.

Craterhab; an inflated pressurized fabric dome concept for Mars

(A small surface human settlement on Mars with Craterhabs - inflated fabric pressurized habitat system)

Craterhab is our flagship pressurized habitat concept consisting of ultra-high strength composite fabric in the form of sheets and cables, anchored into the ground. These are large scale structures aimed to create a paraterraformed environment inside Martian craters. 

These domes are built around the core challenge of maintaining liveable internal atmospheric pressure, where humans can come out of their spacesuits and adopt an Earth-like living experience for safety and comfort.

While protecting the inhabitants from extremely low atmospheric pressure is a greater priority for immediate survival and sustenance, any large scale habitat system, once set up, will face the constant challenge of temperature regulation round the clock. 

Living underground will obviate much of the need for temperature regulation, but it may work for early, small-scale colonization. With the expansion of human presence on Mars, humans must live on the surface in large habitats containing entire bases or city blocks and do farming, harnessing the natural sunlight for photosynthesis and day-night cycle. Radical measures are needed to achieve a reliable temperature regulation for a long term sustenance of a sizable human presence on Mars.

Smart design of a Craterhab

Craterhabs are designed having the temperature regulation needs in mind. Being a fabric structure means there is little material in the way of radiant loss of the precious interior heat into the frigid exterior. The Craterhab design has the following provisions for temperature regulation.

1. The semi-transparent material

The main body of the Craterhab dome designed for Mars consists of an opaque Dyneema skeletal framework, with light coloured kevlar webbing interwoven between the opposite sides of the hexagonal lattice of the skeletal frame. Gaps are left within the webbing to allow natural light, up to 20-30%. The webbing is sealed and secured with a hexagonal semitransparent silicone sheet overlapped and sealed at the edges by Dyneema strip along the Dyneema skeletal frame. This pattern is repeated over each hexagon. The outer layer of the Silicone sheet is covered by a thin layer of Kapton, which not only reflects the UV light but also protects the silicone from the vacuum of the exterior. 

This allows a small but considerable fraction of the sunlight to penetrate into the dome during daytime, creating a greenhouse effect and warming up the interior of the Craterhab. The hemi-ellipsoidal shape of the dome means warming up of the dome right from the time of sunrise, until nearly sunset, utilizing most of the daytime sunlight. With no overcast days on Mars. Occasional wispy cloud layers in the Martian atmosphere are not capable of blocking any noticeable amount of sunlight in most of the year, except the global dust storms once every few years that blanket the entire globe for months on end, and will require powered heating of the interior.

(The light coloured Kevlar webbing inside the hexagonal skeletal frame. The small gaps in the webbing will allow natural light to penetrate to create a greenhouse effect inside a Craterhab)

(The greenhouse principle) Source: https://nmsgrade8science.weebly.com/causes-of-climate-change.html

(An AI artwork of what the interior of a residential Craterhab might look like. The aim of a Craterhab pressurized habitat system to is create a para-terraformed environment inside Martian craters to enable maximum Earth-like living environment. Temperature regulation inside a Craterhab will play a vital role in enabling and sustaining such an environment).

2. Double layer and air insulation

The main Craterhab dome is composed of a double layer of the above configuration with a slight gap between the two, roughly 5-10mm. This gap will be filled with air. Air has almost the same thermal conductivity and insulation property as the aerogel, but far cheaper. Though vacuum has lower thermal conductivity, pressurized air is better in keeping the bilayer separate, maintaining a gap between the two layers and creating a reliable insulation. This will reduce the conductive heat loss from the interior to the exterior.

(The air between the fabric layers will provide excellent insulation against conductive loss of heat from the interior to the outside)

3. The habitat volume

Craterhabs are designed to be enormous structures, up to several million cubic meters of habitable volume inside Martian craters. The greenhouse effect will warm up the interior pretty quickly after the day break, yet the large interior volume will create a thermal buffer, and slow down the heat loss during the night. 

4. Air circulation

Craterhabs will run on continuous climate control and gas exchange. The cold air sinking to the bottom of the Craterhab can be heated and recirculated while scrubbing CO2 and adding oxygen equal to the breathing volume of the humans living inside, maintaining a constant supply of heated air to match the radiant heat loss. This will consume power but Martian human settlements are expected to be power hungry. It will not be possible to establish a substantial human presence on Mars without a reliable and sustained power generation method from local resources on Mars, including small scale nuclear reactors, or novel methods including fusion energy or innovative concepts such as our proprietary hybrid power generation method utilizing the cold and thin Martian atmosphere as a deep heat sink for rapid release of unbalanced entropy of subsurface water ice into the atmosphere (Mareekh Process - patent no. US 11421559 B1).

(Utilizing latent heat released from Mareekh Process to heat up interior of a Craterhab. Source: https://www.mareekh.com/post/revisiting-the-mareekh-process-part-1-the-latent-heat-question)

5. Humidity

(The Eden Project, Cornwall UK houses world's largest indoor rainforest. This sustained tropical ecosystem is enabled through the use of greenhouse heat trapping and high humidity)

Most greenhouses on Earth maintain a humidity of ~ 80% for better temperature regulation and plant growth. The same concept can be employed in a Craterhab through maintenance of high humidity to conserve maximum heat. Humid air has relatively higher specific heat than dry air due to its moisture content. This means it takes longer to achieve the desired temperature, but contains much higher heat content than dry air, and releases it much slower than dry air.