Illustrated lunar colony from NASA SP 509. Credit: NASA.

Dr. Doug Plata from The Space Development Network hosted a two part session on Earth independence at the 2019 ISDC. This involves the idea of reducing a future space colony's dependence on importing essential goods from Earth for survival. Independence from Earth can only be achieved via in-situ resource utilization, which is the process of converting local resources into required goods. Until this happens, any future space colony will be dependent on shipments from Earth for survival.

This is a special report from the 2019 International Space Development Conference (ISDC) in Washington D.C. The 2019 ISDC was focused on how we can establish a sustainable human presence in space. ISDC covers many visionary topics, including ISRU techniques, space colonies, space solar power, interstellar travel, and more.

There are different types of independent colonies, but this two day session focused on the independence of a technical colony that could produce and develop physical goods.

Colony Requirements

The core requirements of a colony are grouped by their immediacy, including short, medium, and long term. Solving a long term requirement will be for nothing if the colony can not survive the short term.

Short Term

The short term requirements are needed for minute to minute survival. Handling these requirements will be the colony's first goal.

Air: For human and agricultural consumption, which will require a production, purification, and recycling system.
Oxygen: Mainly used for the oxidizer in propellant.
Temperature control: Need to mitigate heat and cold from internal and external sources.
Power: All core systems will require stable and reliable power. The expansion of the power structure will also be important for colony growth.
Electronics: Automated systems will be important for many industrial processes and recreational entertainment. An early colony will only be able to import advanced circuits, so oversupplying key chips can provide a safety buffer. Manufacturing electronics locally will be very challenging due to the dangerous chemicals and advanced machines used, although they have a high density per component.

Medium Term

The medium term requirements are needed for week to week survival.

Drinkable water: Potable water for human and agricultural consumption. Not only will this require a purification and recycling system, but a way to extract new water in-situ.
Food: Locally grown food to supply nutrition. Ideally, the food would be varied in taste and texture to provide both psychological and health benefits.
Equipment reproducibility: Be able to replace equipment damaged from wear and tear. Some types of equipment will be more important than others, so prioritizing those is important. May need to recycle existing equipment, or set up manufacturing equipment that can utilize in-situ resources.
Radiation protection: All people, important electronics, and sensitive agriculture will require additional radiation protection. This is especially important for solar particle events that occur once every 4 to 5 months. Possibly solved with knowledge of local geography or by burying base under regolith.
Sanitation: Will need to reuse and recycle all waste streams. This will allow the recapture of important elements, while also ensuring a healthy environment.

Long Term

Once day to day survival is under control, the long term requirements can be made independent of terrestrial shipments.

Habitat reproduction and replaceability: Structures will need to be upgraded and replaced as the base expands and ages. This will require the use of local materials, possibly by 3D printing structures.
Biological isolation: Quarantine procedures will be important to prevent biological contamination between the colony and outside areas, including Earth.
Sufficient gravity: Human health requires sufficient gravity, both for raising children and maintaining healthy adults. This may require special centrifuge living environments.
Information: Colonists will need access to vast knowledge archives to produce anything they require and for entertainment. Storing petabytes of data in an extreme, power deprived environment for a long duration will be very challenging.
Genetic diversity: Generations of colonists will require genetic diversity among themselves, possibly through a diverse starting group or a gene bank.
Translocation: It is important to have the ability to share and transfer resources, people, and knowledge.

Reasons

The three key reasons for pursuing Earth independence of an off-world colony include reducing costs, increasing robustness of supply lines to the colony, and ensuring human survivability.

Reducing Costs

Satisfying colony requirements locally will ultimately lower the total cost of supplying the colony. A side benefit of producing more goods locally is that the colony can grow faster because they would not be restricted by launches restrictions and travel time from Earth. The colony will require about 50% supply independence before cost savings becomes visible.

Robust Supply Lines

Similar to modern society's reliance on oil supply lines, colonies will be completely reliant on their supply lines for survival until they become independent. It is therefore important for the colony to survive interruptions to their supply lines. One way to increase the robustness of supply lines is to locally produce goods. About 50% of the colony's goods will need to be independent before they have safety of supplies.

Human Survivability

Although a long term concern, having an off-world colony increases the probability that humanity can survive a catastrophic event on Earth. However, any colony will require 100% of their supplies to be independent before this would be possible.

A similar potential is to enable the Earth to become a bio-sanctuary by moving all heavy industry off Earth.

Measuring Independence

Independence from Earth can be measured by the mass launched from Earth to the colony. Initially, the top mass items delivered would include the descent and ascent propellant (>50%) and water. Producing propellant locally would dramatically lower the launch mass from Earth. Possibly up to 85% of the mass can be eliminated by processing water at the colony.

Timelines

It is unclear how soon a colony could achieve Earth independence, especially since we have yet to create an off-world colony. The International Space Station has been permanently inhabited since November 2000, however, it's not a colony with reproduction as the goal.

We need to continue studying the health implications of people living and reproducing in space, along with what is required to live a comfortable and healthy life. The ramifications of failure will be swift and dramatic, so it is important that we understand as much as we can before establishing humanity's first long term off-world colony.

Earth Independence