| Code | Display | Definition |
| microgravity |
Microgravity |
A state of very weak gravity experienced in spacecraft in orbit, where the apparent weight is significantly less than on Earth but not completely zero |
| zero-gravity |
Zero Gravity |
The condition of apparent weightlessness experienced in freefall or in space |
| air-quality-space |
Space Habitat Air Quality |
The condition of air within confined spacecraft or space habitats, including levels of pollutants, CO2, and other gases |
| space-radiation |
Space Radiation |
Radiation experienced in the space environment, including galactic cosmic rays, solar particle events, and trapped radiation |
| vacuum-environment |
Vacuum Environment |
The near-vacuum conditions of space that pose risks to human health and spacecraft systems |
| cabin-pressure |
Cabin Pressure |
The atmospheric pressure maintained within spacecraft habitats |
| temperature-extremes |
Temperature Extremes |
The extreme hot and cold temperatures experienced in space depending on exposure to sunlight or shadow |
| lunar-dust |
Lunar Dust |
Fine particles of lunar regolith that can cause respiratory and equipment problems during lunar missions |
| martian-dust |
Martian Dust |
Fine particles of Martian regolith that can cause respiratory and equipment problems during Mars missions |
| space-debris |
Space Debris |
Artificial orbital debris that presents a collision hazard to spacecraft and astronauts during EVA |
| confined-living-space |
Confined Living Space |
The restricted living and working areas within spacecraft that can impact physical and psychological health |
| galactic-cosmic-radiation |
Galactic Cosmic Radiation |
High-energy particles originating outside the solar system that can penetrate spacecraft and human tissue |
| solar-particle-events |
Solar Particle Events |
Radiation from solar flares and coronal mass ejections that can pose acute radiation hazards |