National Aeronautics and

Space Administration

2023 Moon to Mars Architecture Concept Review 1white paper 2023 Moon to Mars Architecture

Introduction

NASA has been sending humans to space for 

more than 60 years, confronting the essential 

challenge of human spaceflight: that our bodies 

and minds evolved to live on Earth. Living and 

working off our planet, and on another planet, 

poses unique hazards to the human system. 

Understanding the effects of spaceflight on 

human physiology, psychology, and individual 

and team performance is essential to keep 

astronauts safe and healthy as exploration 

moves from low-Earth orbit to deep space 

destinations on and around the Moon and 

eventually Mars. 

The five main hazards of human spaceflight 

are space radiation, isolation and confinement, 

distance from Earth, altered gravity fields, and 

hostile/closed environments. This paper will 

highlight how these hazards and the risks they 

pose to the human system influence NASA’s 

Moon to Mars Architecture. These hazards are 

not always independent from one another; like 

human systems, the hazards are frequently 

coupled and interconnected, potentially causing 

synergistic effects or combined impacts. 

Addressing the hazards and defining solutions 

will require a combination of human health and 

performance and engineering solutions. These 

solutions will be balanced with acceptable risks 

imposed on the crew and mission parameters 

such as duration, vehicle designs, operational 

considerations, and cost.

Human Health and Performance: Keeping Astronauts

Safe & Productive On a Mission to Mars

Figure 1. Five 

Hazards of Human 

Spaceflight and 

Associated Human 

System Risks

The following content integrates and summarizes NASA-STD-3001, NASA Spaceflight Human-System 

Standard Volume 1 and 2, which establishes agency standards that enable human spaceflight 

missions by minimizing health risks, providing vehicle design parameters, and enabling the 

performance of flight and ground crew. Applicability and tailoring of standards are determined 

based on each program’s mission profile and procurement strategy.
2023 Moon to Mars Architecture Concept Review 2

Space Radiation

On a Mars mission, crew members will experience 

accumulated ionizing radiation exposure from galactic 

cosmic radiation and solar particle events. Solar particle 

events can expose astronauts to sudden increases in 

radiation, but the probability of a large event that would 

cause acute syndromes such as nausea and fatigue is 

extremely low (approximately 1 in 1,000). Shielding of 

spacecraft and habitats is effective against solar particle 

events, but only mitigates galactic cosmic radiation 

exposure by approximately 7–15 percent. 

Deep space radiation exposure is a mitigated in-mission 

risk for acute radiation sickness. The consequences of 

spaceflight radiation exposure are an increased risk of 

cancer incidence and death later in life (post-mission), 

along with increased risk of cardiovascular disease. 

The overall increase in cancer mortality for an average 

weight, non-smoking astronaut would increase from a 

probability of 15 percent over a lifetime to approximately 

20 percent after a 1,000-day Mars trip (which is a 33 

percent increase in lifetime mortality risk). Comparatively, 

an American who is overweight, drinks alcohol, consumes 

an average diet, and lives a less active lifestyle than 

a typical astronaut has an approximately 21 percent 

probability of dying from cancer. 

For comparison, occupational controls for terrestrial 

radiation workers — such as personnel working at 

nuclear power plants or medical personnel using x-ray 

equipment — require radiation exposure to incur less 

than a 0.5 percent increase in mortality risk per year; 

nominally, exposure is controlled to incur less than a 0.1 

percent increase in mortality risk per year.

Transit vehicles and habitat design guidance to minimize 

radiation exposure should consider the following factors:

• Transit time and mission timing: Minimize the total 

transit time between the planets to reduce the crew’s 

radiation exposure, and plan transits during solar 

maximum to minimize galactic cosmic radiation 

exposure.

• Engineering countermeasures: Provide shielding 

from solar particle events using existing/planned 

vehicle mass. Use of consumables, including 

environmental control and life support system water/

gray water, should be considered for solar particle 

event protection in lieu of polyethylene.

• Optimized vehicle design and shielding materials: 

Use existing mass to increase global cosmic radiation 

shielding to approximately 7–15 percent. 

• Monitoring/notification: Provide onboard 

capabilities to detect, monitor, and characterize the 

radiation environment.

Isolation and Confinement

Future exploration missions will involve humans traveling 

further from Earth for longer mission durations. These 

missions will likely necessitate prolonged periods of 

isolation and confinement that pose a greater risk for 

behavioral health and performance. These hazards could 

lead to: 

1. Adverse cognitive or behavioral conditions affecting 

crew health and performance during the mission.

2. The development of psychiatric disorders if adverse 

behavioral health conditions are undetected or 

inadequately mitigated.

3. Long-term health consequences, including lateemerging cognitive and behavioral changes. 

Transit vehicles and habitat design guidance to mitigate 

various psychological stressors should consider the 

following factors:

• Personal/private space: Provide separate, individual 

sleeping/personal quarters with auditory isolation 

and physical separation (if possible) for each crew 

member. Private spaces separate from common 

spaces, social areas, and congested movement paths 

are preferred.

• Workspace: Allocate adequate volume and resources 

to accommodate everyone’s work and activities (e.g., 

science, laboratory equipment, electronic curriculum). 

• Window: Provide at least one window for direct 

viewing outside of the vehicle.

• Cabin environmental controls: Ensure each crew 

member can control cabin temperature, ventilation, 

lighting, humidity, and noise by placing individual 

controls and distribution vents in crew quarters and 

at workstations.

• Communication with home: Each private quarter 

should include communication systems that facilitate 

multiple modes of communication.

• Crew composition: Characteristics of expected range 

of crew composition (including team size, gender 

makeup, job roles, and cultural backgrounds), which 

are established before the mission.

• Team coordination and collaboration: Provide 

common areas with enough volume for the team to 

gather for recreation and dining, including screen 

access for communal viewing.

• Human factors and habitation: Spacecraft designers 

should use human-centric approaches to create 

optimal workload, habitable volume, and layout, 

ensuring adequate movement pathways and volume 

envelopes and access to rails and harnesses.

Distance from Earth

Mars is, on average, 140 million miles from Earth, with 

a one-way communication delay of up to 22 minutes. 

This distance will require astronauts to solve problems 

and identify solutions as a team, without immediate help 

from NASA’s mission control. 

As distance from Earth increases, spaceflight crews 

will, by necessity, become increasingly independent 

from mission control, and more dependent on their 

vehicle and logistics. This elevates the need for effective
2023 Moon to Mars Architecture Concept Review 3

on-board systems that enable the crew to respond to 

demands and anomalies that may acutely arise. 

This autonomy (or “Earth independence”) must enable 

the astronauts to maintain, debug, and repair the vehicle. 

It must also allow them to monitor the state of their own 

health and wellbeing by accessing and using medical 

information in real-time operations and use decision 

support tools to reduce cognitive burden. Current plans 

entail years of training to prepare astronauts for such 

missions, increasing the risk that not all training will be 

retained (and/or retrievable). 

Transit vehicles, habitats, and operational guidance to 

enable crew and vehicle autonomy should consider the 

following factors:

• Integrated data architecture/decision support tools:

Implement a vehicle-integrated data architecture 

and decision support tools that enable crew to 

make decisions independently of immediate ground 

support. 

• Robust on-board medical capabilities: Provide 

advanced prevention, diagnostic, treatment, and 

rehabilitation modalities. 

• Automation/robotic systems and human 

interaction: Human operators need to maintain 

situational awareness to work effectively with 

automation.

• Food and nutrition: Provide safe, nutritious, and 

palatable food with sufficient calories, micronutrients, 

and macronutrients. Consider shelf life if food will be 

sent ahead of crew.

• Maintainability: Design for maintainability, with 

system-level optimization for parts and ergonomics. 

Consider tools and information as part of the design 

to consume minimal crew time.

• Crew training: Provide adaptable, in-mission training 

capabilities for crew.

Altered Gravity Fields

Astronauts will encounter different gravity fields on a 

Mars mission. On the multi-month trek between the 

planets, crews will be weightless in microgravity. While 

living and working on Mars, crews will have to adapt to 

a partial gravity environment (three-eighths of Earth’s 

gravity), and upon returning home, crews will have to 

readapt to Earth’s gravity. Landing a spacecraft on Mars 

could be challenging as astronauts adjust to partial 

gravity. 

In addition to sensorimotor disruptions, crew members 

may have difficulty maintaining their blood pressure 

while standing, potentially leading to lightheadedness 

and fainting. Additionally, musculoskeletal unloading 

in microgravity will lead to decreased aerobic capacity, 

muscle strength, and bone quality and density (weightbearing bones are estimated to lose about 1–1.5 percent 

mineral density per month spent in microgravity, which 

may lead to long-term changes in bone that increase 

fracture risk). Fluids in the body also shift upward to the 

head in microgravity, resulting in structural and functional 

changes to the eye and increases in the brain ventricular 

and perivascular volumes that can develop in flight and 

persist after flight (Spaceflight Associated Neuro-ocular 

Syndrome [SANS]). 

Transit vehicle design, habitat design guidance, and 

egress/ingress/return considerations to mitigate various 

physiologic effects should consider the following factors:

• Exercise: Provide sufficient volume, mass allocation, 

and vehicle vibrational damping for physiological 

countermeasures. 

• Sensorimotor/balance: Provide for in-flight 

sensorimotor countermeasures adaptation training 

to improve astronauts’ performance. Operational 

timelines should reduce the number of critical 

activities for a defined period after a gravity transition 

to ensure crew performance, safety, and mission 

success. Extravehicular activity suit and rover design 

considerations can also be applied to address 

sensorimotor functioning.

• SANS: Provide sufficient volume and mass allocations 

for pharmaceutical or mechanical countermeasures.

• Acceleration and dynamic loads: Design the vehicle’s 

acceleration/deceleration profiles and dynamic 

phases of flight for deconditioned crew members 

with reduced abilities (for both nominal/automated 

operations and manual crew control). 

• Anthropometrics: Consider all operational gravity 

fields and environments, designing habitable 

volumes that ensure all crewmembers can perform 

any planned tasks efficiently and effectively. 

Hostile/Closed Environments 

The ecosystem inside habitats and spacecraft is crucial in 

everyday astronaut life. In space, enclosed environments 

(including vehicles and suits) do not have the benefit of 

natural CO2 removal, relying instead on CO2 removal 

equipment to help regulate CO2 levels and decrease the 

risk of negative consequences of elevated CO2 exposure. 

Additionally, lunar and Martian dust exposure could lead 

to serious health effects to the crew, such as respiratory, 

cardiopulmonary, ocular, or dermal harm.

To ensure environmental adequacy, transit vehicles, 

habitat design, and extravehicular activity planning 

guidance should consider the following factors:

• Environmental control and life support system:

Provide clean air and adequate water quantities 

for consumption and hygiene. Manage air and 

water quality, waste, atmospheric parameters, and 

emergency response systems. 

• Countermeasures: Mitigate the risk of infectious 

disease (viral and bacterial) and alterations to 

immunity (due to spaceflight stressors) through 

implementation of a pre-flight crew health 

stabilization program. 
• Atmospheric pressures/composition and materials/

flammability: Consider differences in flammability in 

different atmospheric pressures and compositions. 

Vehicle and suit design should also incorporate 

on-board treatment of decompression sickness. 

• Dust mitigation: Provide adequate air filtration 

systems to meet existing standards for dust exposure. 

Consider an airlock for ingress/egress to separate 

the vehicle hatch from the habitation area to further 

prevent contamination. Protect extravehicular activity 

suit joints and closures functions to prevent breaches. 

2023 Moon to Mars Architecture Concept Review 4

Key Take-Aways

The human system is being considered early in vehicle design phases and operations for 

Mars architecture development. The architecture recognizes the five primary hazards 

of human spaceflight (space radiation, isolation and confinement, distance from earth, 

altered gravity fields, and hostile/closed environments) and balances risks with cost and 

design parameters. Missions may be comprised of consecutive segments that occur in 

different vehicles at different locations in space with varying distances from Earth and 

that last for different durations. However, the cumulative exposure to the five hazards 

over the entire mission duration needs to be considered to protect human health and 

performance. Shorter transit times to Mars would ameliorate many of the human 

system risks. Mars missions will require crew and vehicle autonomy, which will be a 

significant paradigm shift from current low-Earth orbit missions. 

Additional Reading

1. NASA’s Chief Health and Medical Officer, Technical Briefs, National Aeronautics and Space Administration, 

Washington, D.C. https://www.nasa.gov/ochmo/health-operations-and-oversight/hsa-standards/ochmotechnical-briefs/

2. NASA-STD-3001 VOL 1, NASA Space Flight Human-System Standard Volume 1, Revision A: Crew Health, National 

Aeronautics and Space Administration, Washington, D.C. (2022). 

3. NASA-STD-3001 VOL 2, NASA Space Flight Human System Standard Volume 2: Human Factors, Habitability, and 

Environmental Health, National Aeronautics and Space Administration, Washington, D.C. (2022). 

4. NASA’s Human Research Program, The Human Body in Space, National Aeronautics and Space Administration, 

Washington, D.C. (2021) https://www.nasa.gov/hrp/bodyinspace 

5. NASA’s Human System Risk Board, National Aeronautics and Space Administration, Washington, D.C. https://

www.nasa.gov/hhp/hsrb 

6. NASA’s Human Research Program, Human Research Roadmap, National Aeronautics and Space Administration, 

Washington, D.C. https://humanresearchroadmap.nasa.gov/ 

7. NASA’s Human Research Program, 5 Hazards of Human Spaceflight, National Aeronautics and Space 

Administration, Washington, D.C. (2021) https://www.nasa.gov/hrp/hazards