vol.64-2 (2026/7/31)

Examination of the requirements specifications for air-based ECLSS necessary for manned space exploration

Astronauts spend 100% of their time inside spacecraft. Therefore, the Indoor Air Quality (IAQ) inside the spacecraft is even more important than on Earth. The system that controls IAQ is called the Environmental Control and Life Support System (ECLSS) in spacecraft. This document introduces the ECLSS on the ISS and the Gateway. It also introduces SMAC and T-values, and presents examples of ECLSS trade-offs using ESM (Equivalent System of Mass).

On-orbit demonstration of small autonomous distributed environmental sensors in “Kibo” on the International Space Station

In manned space habitats such as the International Space Station (ISS), air quality management is becoming increasingly important for maintaining comfort and health. In particular, CO₂ generated by astronauts’ respiration must be continuously removed, and its control threshold is approximately 7,000 ppm. In this study, on-orbit demonstration data obtained on the ISS using small autonomous distributed environmental sensors were used to characterize the onboard CO₂ concentration distribution and to validate computational fluid dynamics (CFD) analysis. The average onboard CO_{2 concentration with one astronaut present was approximately 2,700 ppm, and a mild concentration gradient was observed across a representative cross-section. In addition, comparison with measured data confirmed the validity of the CFD analysis and enabled prediction of the airflow characteristics within the cabin. These findings contribute to the advancement of environmental assessment models for manned space habitats.}

Development of a photocatalyst for air purification with a view to space applications

Long-duration human space missions require reliable air purification technologies to maintain safe and comfortable closed habitats. In spacecraft, lunar bases, and future Martian habitats, trace contaminant gases, volatile organic compounds, odors, and microbial contamination must be continuously controlled with low power consumption and limited maintenance. This article introduces TiO₂-based photocatalysts as promising materials for air purification with a view to space applications. TiO₂ photocatalysts generate electrons and holes under light irradiation and produce reactive oxygen species that oxidatively decompose organic compounds and suppress microorganisms. Acetaldehyde, one of the waste gases in closed space environments, has been used as a model gas to evaluate photocatalytic decomposition. Fe-cluster-loaded TiO₂ promotes acetaldehyde decomposition under UV-LED and white-LED irradiation compared with bare TiO₂, indicating that interfacial charge-transfer photocatalysts improve photon utilization. In addition, composites of imogolite and Cu (II) -grafted TiO₂ have been investigated under visible light. Imogolite provides adsorption and humidity-control functions, while Cu species promote multielectron oxygen reduction. Optimization of the composite ratio enables high acetaldehyde decomposition activity over a wide humidity range. These results show that visible-light-responsive photocatalysts combined with adsorbents and humidity-control materials are promising candidates for treating waste gases in closed space environments. Future development requires catalyst immobilization, efficient light-source design, long-term durability, byproduct control, and integration with filters and ECLSS technologies.

ECLSS development for human spaceflight

Mitsubishi Heavy Industries (MHI) has developed Environmental Control and Life Support Systems (ECLSS) supporting human spaceflight from low Earth orbit to lunar exploration. Building upon technologies used in the Japanese Experiment Module “Kibo” on the International Space Station (ISS) and the H-II Transfer Vehicle “KOUNOTORI,” MHI advances ECLSS development for the new HTV-X, the Gateway lunar orbiting outpost, and the manned pressurized rover. Core technologies include air revitalization, carbon dioxide removal, and trace contaminant control, adapted for long-duration and remote missions. This paper summarizes MHI’s achievements and ongoing efforts toward sustainable human presence in space.

Air purification system using zeolite-based porous materials

This paper reports on candidate materials for reducing energy consumption in the dehumidification component of CO₂ removal systems. AQSOA^TM Z02 is a zeolite-based porous material composed of silicon, aluminum, phosphorus and oxygen, and it exhibits distinctive water vapor adsorption characteristics. In this study, we present the advantages of this material over conventional adsorbents such as silica gel and zeolite 13X, as demonstrated through small-scale model evaluations, with a particular focus on its high water vapor adsorption capacity, lower regeneration temperature, and faster desorption kinetics.

Atmospheric bioaerosol observations on the region of Antarctic area

Bioaerosols are biological particles, specifically including viruses, bacteria, spores, pollen, and biological fragments. The focus of Antarctic atmospheric bioaerosol research is as follows: (1)assessing the effects of the atmospheric ecosystem on the region’s terrestrial and aquatic ecosystems within its challenging ecological environment; (2)substantiating the atmospheric origins of microbes found in Antarctic ice cores, which may be tens of thousands of years old; (3)elucidating the relationship between bioaerosols and Antarctic meteorological dynamics, such as polar circulation, the polar vortex, and katabatic winds; (4)investigating the long-distance transport of bioaerosols from South America, Australia, and Africa; and (5)conducting inaugural observations of atmospheric bioaerosols in Antarctica. This paper introduces the atmospheric bioaerosol observations of assessment of anthropogenic impacts on atmospheric bioaerosols at Syowa Station, atmospheric bioaerosol observations on the penguin luccary, Syowa Station using a tethered balloon, S17 base via an unmanned aerial vehicle (UAV) in Antarctica, carried out by 54^th and 60^th Japanese Antarctic Research Expedition.

Initiatives toward zero emissions at Syowa Station in Antarctica.
–Study on cloud-based energy management and environmental measurement–

In renewing the Syowa Station in Antarctica, it was required to adopt energy-saving designs. However, since the actual energy use of the station, which is necessary for selecting equipment capacity, had not grasped, it was decided to introduce a cloud BEMS. Here, we report on the installation of measurement systems such as sensors in Antarctica and the construction of a visualization system, which have been carried out so far.