[Author's notes]

Exploration Systems Development Mission Directorate (ESDMD)
The Exploration Systems Development Mission Directorate defines and manages systems development for programs critical to the NASA’s Artemis program and planning for NASA’s Moon to Mars exploration approach in an integrated manner. ESDMD manages the human exploration system development for lunar orbital, lunar surface, and Mars exploration. ESDMD leads the human aspects of the Artemis activities as well as the integration of science into the human system elements. ESDMD is responsible for development of the lunar and Mars architectures. Programs in the mission directorate include Orion, Space Launch System, Exploration Ground Systems, Gateway, Human Landing System, and Extravehicular Activity (xEVA) and Human Surface Mobility.

The ESMD mission is derived from the Vision for Space Exploration first initiated in January 2004, which commits the United States to implement a sustained and affordable human and robotic program to:

• Explore the solar system and beyond
• Extend human presence across the solar system, starting with a human return to the moon by the year 2020, in preparation for human exploration of Mars and other destinations
• Develop the innovative technologies, knowledge, and infrastructures both to explore and to support decisions about future destinations for human exploration
• Promote international and commercial exploration participation to further U.S. scientific, security, and economic interests

Biosphere 2
Biosphere 2 is an American Earth system science research facility located in Oracle, Arizona. Its mission is to serve as a center for research, outreach, teaching, and lifelong learning about Earth, its living systems, and its place in the universe. It is a 3.14-acre structure originally built to be an artificial, materially closed ecological system, or vivarium. It remains the largest closed system ever created.

Constructed between 1987 and 1991, Biosphere 2 was originally meant to demonstrate the viability of closed ecological systems to support and maintain human life in outer space as a substitute for Earth's biosphere. It was designed to explore the web of interactions within life systems in a structure with different areas based on various biological biomes. In addition to the several biomes and living quarters for people, there was an agricultural area and work space to study the interactions between humans, farming, technology and the rest of nature as a new kind of laboratory for the study of the global ecology. Its mission was a two-year closure experiment with a crew of eight humans ("biospherians"). Long-term it was seen as a precursor to gain knowledge about the use of closed biospheres in space colonization. As an experimental ecological facility it allowed the study and manipulation of a mini biospheric system without harming Earth's biosphere.

Its seven biome areas were a 1,900-square-meter (20,000 sq ft) rainforest, an 850-square-meter (9,100 sq ft) ocean with a coral reef, a 450-square-meter (4,800 sq ft) mangrove wetlands, a 1,300-square-metre (14,000 sq ft) savannah grassland, a 1,400-square-meter (15,000 sq ft) fog desert, and two anthropogenic biomes: a 2,500-square-meter (27,000 sq ft) agricultural system and a human habitat with living spaces, laboratories and workshops. Below ground was an extensive part of the technical infrastructure. Heating and cooling water circulated through independent piping systems and passive solar input through the glass space frame panels covering most of the facility, and electrical power was supplied into Biosphere 2 from an onsite natural gas energy center.

The first closed mission lasted from September 26, 1991 to September 26, 1993 with eight crew. Low morale and psychological problems plagued the two-year mission. The eight crew members eventually split into two factions of four who hated each other.

Hawaiʻi Space Exploration Analog and Simulation (HI-SEAS)
The UH Mānoa research project, funded by NASA, will help with the selection of crews for future long-duration space missions, such as a mission to Mars. UH has been operating the long-duration planetary surface simulations in the Mars-like setting to investigate crew composition and cohesion since 2012. The aim of the project is to simulate what it would be like to start a colony on Mars to the best of our ability based on available data, and to resolve challenges on Earth before such a mission may be attempted in the future.

The team was issued with virtual reality headsets to pass the time and let their minds revisit the outside world.

Nezemnyy Eksperimental’nyy Kompleks (NEK)
A crew of six will live in isolation in a closed facility at Moscow's Institute for Biomedical Problems at the Russian Academy of Sciences from four to eight to 12 months. This habitat facility was used in 2011 for a notable series of Russian mock Mars missions known as Mars500. During these missions, crews spent 520 and 105 days (on two separate missions) in the facility.

For a study of this kind, it offers unique aspects which are paramount to meeting NASA’s long-term goals of sending multicultural crews to the Moon, and eventually Mars. The pressurized facility can accommodate large international crews and operate for long-duration missions of more than one year. The crew members are physically isolated from the outside world and have limited communication beyond NEK’s walls. This allows the crew members to feel as if they are in an actual spaceflight environment.

Missions through the Scientific International Research In a Unique terrestrial Station, or SIRIUS, represent an international, multicultural series of studies researching the effects of isolation and confinement on human psychology, physiology and team dynamics to help prepare for long-duration space exploration. A recently completed four-month mission occurred from March to July 2019. The six international crew members reported for training in January, prior to the start of the mission. Other NEK missions in the SIRIUS series will be longer in duration, lasting eight months and one year. With an international crew, the series of research will focus on studying multicultural team dynamics in an isolation environment.

The goals of the SIRIUS missions involve studying behavioral health and performance in an isolated environment over long periods of time. Assessments will specifically focus on team dynamics, physical and mental effects of prolonged exposure to confinement, sensory deprivation, monotony, and limited communication with the outside world. This also allows the development of countermeasures, which can be validated in flight. This type of research is important, since crews that will explore beyond low-Earth orbit will be international in composition, and will be more isolated and confined than humans have ever been.

HERA (Human Exploration Research Analog)
A crew of four will live in isolation in a closed facility at Houston's Johnson Space Center for 45 days.

Participants that join the experiment's crew will spend 8 months inside HERA, a closed three-story habitat designed to serve as an analog for isolation, confinement, and remote conditions in exploration scenarios. It will have environmental aspects similar to those astronauts are expected to experience on future missions to Mars.

The crew will spend these months living together in isolation and working on scientific research. They will even virtually conduct experiments that future astronauts might be expected to perform on locations like the lunar surface.

By living and working in this Mars base-like environment, participants in this study will help NASA researchers to better understand the psychological and physiological effects of isolation, according to a NASA statement.

This will be a type of analog mission, a crewed mission on Earth but which mimics the environment or living conditions expected at a place like the moon or Mars. These missions help researchers to not only perform relevant science experiments but also to see how people might fare under strange conditions for extended periods of time.

Participants will experience environmental aspects similar to those astronauts are expected to experience on future missions to Mars. A small international crew will live together in isolation for eight months conducting scientific research, using virtual reality and performing robotic operations among a number of other tasks during the lunar mission. The research will be conducted to study the effects of isolation and confinement as participants work to successfully complete their simulated space mission. Results from ground-based missions like this help NASA prepare for the real-life challenges of space exploration and provide important scientific data to solve some of these problems and to develop countermeasures.

NASA is looking for highly motivated U.S. citizens who are 30-55 years old and are proficient in both Russian and English languages. Requirements are: M.S., PhD., M.D. or completion of military officer training. Participants with a Bachelor’s degree and other certain qualifications (e.g., relevant additional education, military, or professional experience) may be acceptable candidates as well.

MARS-500
The MARS-500 mission was a psychosocial isolation experiment conducted between 2007 and 2011 by Russia, the European Space Agency and China, in preparation for an unspecified future crewed spaceflight to the planet Mars. The experiment's facility was located at the Russian Academy of Sciences' Institute of Biomedical Problems (IBMP) in Moscow, Russia.

Between 2007 and 2011, three different crews of volunteers lived and worked in a mock-up spacecraft at IBMP. The final stage of the experiment, which was intended to simulate a 520-day crewed mission, was conducted by an all-male crew consisting of three Russians (Alexey Sitev, Sukhrob Kamolov, Alexander Smoleevskij), a Frenchman (Romain Charles), an Italian (Diego Urbina) and a Chinese citizen (Yue Wang). The mock-up facility simulated an Earth-Mars shuttle spacecraft, an ascent-descent craft, and the Martian surface. The volunteers who participated in the three stages included professionals with experience in engineering, medicine, biology, and human spaceflight. The experiment yielded important data on the physiological, social and psychological effects of long-term close-quarters isolation.

According to official results, the crew of 520-day isolation underwent the trial as a single unit. There were no interpersonal conflicts noted, nor any situations that would require interrupting or delaying any aspect of the project. The difficulties encountered during the performance of some complicated activities were overcome by the crew together. Cultural differences and language difficulties did not bear any significant influence. Friendly and constructive communication is said to have prevailed throughout the experiment. The crew spent time together, watching films in different languages, and used such recreational activities as an opportunity to discuss the films and interact socially.

The crew prepared surprises for birthdays, major state holidays and informal holidays (on 31 October, they celebrated Halloween). Some crew members increased the time spent on individual activities, which did not hamper communication or interaction. No language, social or cultural barriers were observed, and the mission commander exercised his authority as both a formal and informal leader.

Later in the experiment, the crew spent more time in bed or engaged in personal activity. The crew's overall activity levels plummeted in the first three months, and continued to fall for the next year. On their return journey, they spent 700 hours more in bed than on the outward journey. Four of the members suffered from sleep and psychological issues. One crew member slept so badly he suffered chronic sleep deprivation and single-handedly accounted for the majority of mistakes made on a computer test used to measure concentration and alertness.

Chemical oxygen generator
A chemical oxygen generator is a device that releases oxygen via a chemical reaction. The oxygen source is usually an inorganic superoxide, chlorate, or perchlorate; ozonides are a promising group of oxygen sources. The generators are usually ignited by a firing pin, and the chemical reaction is usually exothermic, making the generator a potential fire hazard. Potassium superoxide was used as an oxygen source on early manned missions of the Soviet space program, for firefighters, and for mine rescue.

A chlorate candle, or an oxygen candle, is a cylindrical chemical oxygen generator that contains a mix of sodium chlorate and iron powder, which when ignited smolders at about 600 °C (1,112 °F), producing sodium chloride, iron oxide, and at a fixed rate of about 6.5 man-hours of oxygen per kilogram of the mixture. The mixture has an indefinite shelf life if stored properly: candles have been stored for 20 years without decreased oxygen output. Thermal decomposition releases the oxygen. The burning iron supplies the heat. The candle must be wrapped in thermal insulation to maintain the reaction temperature and to protect surrounding equipment. The key reaction is:

2 NaClO3 → 2 NaCl + 3 O2

Potassium and lithium chlorate, and sodium, potassium and lithium perchlorates can also be used in oxygen candles.

An explosion caused by one of these candles killed two Royal Navy sailors on HMS Tireless (S88), a nuclear-powered submarine, under the Arctic on 21 March 2007. The candle had become contaminated with hydraulic oil, which caused the mixture to explode rather than burn.

In the Vika oxygen generator used on some spacecraft, lithium perchlorate is the source of oxygen. At 400 °C, it releases 60% of its weight as oxygen:

LiClO4 → LiCl + 2 O2

Carbon dioxide scrubbers
Carbon dioxide can be removed from the air chemically using soda lime (sodium hydroxide and calcium hydroxide) in devices called scrubbers. The carbon dioxide is trapped in the soda lime by a chemical reaction and removed from the air.

Other strong bases such as soda lime, sodium hydroxide, potassium hydroxide, and lithium hydroxide are able to remove carbon dioxide by chemically reacting with it. In particular, lithium hydroxide was used aboard spacecraft, such as in the Apollo program, to remove carbon dioxide from the atmosphere. It reacts with carbon dioxide to form lithium carbonate. Recently lithium hydroxide absorbent technology has been adapted for use in anesthesia machines. Anesthesia machines which provide life support and inhaled agents during surgery typically employ a closed circuit necessitating the removal of carbon dioxide exhaled by the patient. Lithium hydroxide may offer some safety and convenience benefits over the older calcium based products.

2 LiOH(s) + 2 H2O(g) → 2 LiOH·H2O(s)

2 LiOH·H2O(s) + CO2(g) → Li2CO3(s) + 3 H2O(g)

The net reaction being:

2LiOH(s) + CO2(g) → Li2CO3(s) + H2O(g)

Lithium peroxide can also be used as it absorbs more CO2 per unit weight with the added advantage of releasing oxygen.

In recent years lithium orthosilicate has attracted much attention towards CO2capture, as well as energy storage.[12] This material offers considerable performance advantages although it requires high temperatures for the formation of carbonate to take place.

Algae-fueled bioreactor
Through the process of photosynthesis, the aquatic plant algae soaks up carbon dioxide, water and sunlight to produce energy. Naturally, the plant will use this energy to multiply and grow, but scientists have been experimenting with ways to capture it and convert it into biofuels instead.

The reactor uses a specific strain of algae called chlorella vulgaris, which is claimed to soak up much more CO2 than any other plant. The algae lives inside a tube system and water tank within the device, which is pumped full of air and exposed to artificial light, giving the plant the food it needs to thrive and produce biofuels for harvesting.