Sarah Baatout

The central challenge is that the material offering the best radiation protection is not necessarily the best structural material.

Hydrogen-rich materials are attractive because hydrogen is very effective at slowing down energetic charged particles while producing fewer harmful secondary particles than heavier materials such as lead. Polyethylene, water and hydrogen-containing composites are therefore promising. However, polyethylene alone may not provide the stiffness, thermal resistance, fire safety or long-term durability required for a spacecraft structure. Simply adding thick layers also increases launch mass and volume, which are both extremely costly.

Long-term stability is another concern. Materials in space face vacuum, large temperature fluctuations, ultraviolet radiation, atomic oxygen in low Earth orbit and ionising radiation. These exposures can cause polymers to become brittle, release gases or lose mechanical performance. Shielding must also address a complex mixture of galactic cosmic rays, solar particles and secondary neutrons; no single material performs optimally against every component.

The most promising approach is therefore not to search for one perfect material, but to develop multifunctional and layered systems. Hydrogen-rich composites could be combined with strong fibres, boron-containing materials or structural layers. Water, food and other mission supplies could also be positioned around crew quarters and a dedicated storm shelter.

The real engineering question is consequently: how much health protection can we obtain per kilogram while preserving structural safety, durability and mission functionality? Shielding must be designed as part of the habitat from the beginning, rather than added afterwards.

My principal message to policymakers would be that human health must be treated as a mission-enabling capability, not as a medical issue to be addressed once the spacecraft has already been designed.

Health considerations influence radiation shielding, habitat volume, privacy, lighting, nutrition, exercise systems, environmental monitoring and the ability to provide autonomous medical care. Policymakers should therefore require a ‘health-by-design’ approach from the earliest phases of every mission.

A second priority is to consider the astronaut’s entire lifetime, not only whether they can complete the mission. Space agencies and commercial operators need shared standards for acceptable risks, long-term health surveillance, medical follow-up and responsibility for delayed effects. These protections should apply consistently, including to commercial and non-career astronauts.

Third, international collaboration and responsible data sharing are essential. Astronaut populations are small, so fragmented national datasets will rarely provide sufficient evidence. We need interoperable databases, common protocols and appropriate mechanisms for sharing data while protecting medical confidentiality.

Finally, space-health policies must account for biological and individual diversity. Evidence derived predominantly from a small and historically homogeneous astronaut population cannot automatically be applied to everyone. Sex, age, genetics, previous exposures and other individual characteristics can influence risks and responses.

In short, policymakers should advocate for health by design, internationally harmonised standards, lifetime responsibility, inclusive evidence and transparent communication of uncertainty. NASA’s human-spaceflight standards similarly integrate health, medical care, vehicle design and crew performance rather than treating them as separate issues.

Yes, open-source communities could make a major contribution. Spaceflight experiments are rare, expensive and usually involve very small sample sizes. Making data, metadata, protocols and analytical code accessible allows independent researchers to reanalyse results, combine datasets, identify patterns and develop new hypotheses without repeating an entire space mission.

However, making data ‘open’ does not automatically make them scientifically comparable. The largest challenge is often not access but context. We must know precisely how samples were collected, preserved and processed; the mission duration and radiation exposure; the gravity condition; the hardware used; the age, sex and health of the biological model; and the ground-control conditions. A missing detail can make two apparently similar datasets impossible to compare.

Key requirements therefore include common metadata standards and controlled terminology; standardised reference controls and reporting of environmental conditions; validated sample-processing and analytical pipelines; access to both raw and processed data, together with software versions and quality-control information; persistent identifiers linking samples, experiments, publications and code; independent replication and benchmarking; and appropriate governance for sensitive human data.

We should also distinguish data generated during real spaceflight from ground-based simulations such as bed rest, radiation exposure or clinostats. These models are valuable, but they do not reproduce every component of spaceflight and should be labelled accordingly.

NASA’s Open Science Data Repository provides a useful model by combining raw and processed datasets with curated, standardised metadata and FAIR principles. Open communities can help close the evidence gap, but only if openness is accompanied by rigorous standardisation, validation and quality control.

Thank you for this important question. Biofilms are organised microbial communities attached to a surface and surrounded by a protective matrix—rather like bacteria constructing a shared shelter.

Spaceflight can alter microbial gene expression, metabolism, stress responses and interactions with surfaces. Microgravity also changes fluid movement and the transport of nutrients and waste around microbial cells. Depending on the organism and environmental conditions, these changes may influence the amount, thickness, structure and resistance of a biofilm. We should avoid saying that spaceflight always increases biofilm formation or virulence: the response is species-, strain-, surface- and environment-dependent.

In a closed habitat, persistent biofilms could contaminate water systems, reduce filter efficiency, damage materials through biocorrosion and potentially act as reservoirs for opportunistic pathogens. This becomes especially important during long missions, when replacement parts and external support are limited.

The solution will require several complementary measures: designing surfaces that reduce microbial attachment; avoiding inaccessible humid areas and stagnant fluid zones; continuously monitoring water, air and high-risk surfaces; detecting changes before a mature biofilm develops; using targeted physical or chemical cleaning methods; testing disinfectants under real or simulated space conditions; and maintaining a balanced habitat microbiome rather than trying to create an entirely sterile spacecraft.

We should also study mixed-species biofilms, because real spacecraft communities contain many interacting microorganisms. NASA is currently investigating how spaceflight affects polymicrobial biofilms, material corrosion and the effectiveness of silver-based disinfection.

The goal is therefore not simply to eliminate all microbes, which is neither realistic nor necessarily desirable, but to manage the habitat as a carefully monitored microbial ecosystem.

This is a very important distinction because some psychological and behavioural changes are normal responses to isolation, confinement, disrupted sleep, high workload and separation from family. A temporary period of irritability, reduced motivation or withdrawal does not by itself indicate a psychiatric disorder.

The key is not one symptom at one moment, but a combination of change from the individual’s baseline, persistence, severity and functional impact. Warning signs become more concerning when they last, worsen or begin to affect sleep, judgement, task performance, self-care, communication or relationships within the crew.

Assessment should therefore combine several sources: confidential self-reporting; regular private check-ins with trained medical or psychological personnel; observation of changes in behaviour and team interaction; sleep and workload information; brief validated cognitive and psychological measures; and operational indicators such as repeated errors or impaired decision-making.

No single sensor, questionnaire or colleague should determine that someone has a clinical problem. Data must be interpreted in context and by appropriately trained professionals. Crew members must also trust that asking for support will not automatically damage their career; otherwise, difficulties may remain hidden until they become operationally significant.

Pre-mission baseline assessment is essential because people express stress differently. Crews should also be trained to recognise changes in themselves and one another without attempting to diagnose colleagues.

In summary, normal adaptation is generally temporary and remains manageable without substantial loss of function. A clinically relevant concern involves persistent or escalating changes, meaningful distress, impaired functioning or a risk to the person or crew. NASA likewise recognises that undetected behavioural changes can progress from reduced performance to clinically significant conditions, especially during long and autonomous missions.