Plant cultivation in space requires substrates that provide sufficient water retention, root system support, and nutrients. Arcillite – a calcined montmorillonite clay product – is currently used in growth chambers on the International Space Station despite significant variability in mineral composition and occasional detrimental effects on seed germination and plant growth. In contrast, hydrogels – which are used as soil amendments in agriculture – can be produced with desired structural and chemical properties. We compared two batches of arcillite and polyacrylamide (PAAM) hydrogel granules by growing and analyzing radishes (Raphanus sativus) and observed significant differences in leaf and bulb biomass, evapotranspiration, and photosystem II efficiency between the two batches of arcillite, with soluble calcium, magnesium, selenium, and sulfur being more abundant in the poorly performing arcillite. There was no difference in leaf and bulb biomass or photosystem II efficiency between PAAM and the arcillite batch without excessive calcium, but radishes grown in PAAM required significantly less water. Our results indicate that PAAM can outperform arcillite in water-limited environments because of reduced evapotranspiration rates, greater uniformity, and comparable yields. Therefore, hydrogels such as PAAM may be beneficial for space plant cultivation.
Sleep loss and circadian misalignment are recurrent features of human spaceflight and represent an integrated threat to astronaut health, cognition, and operational performance. This narrative review examines the mechanisms that destabilize sleep in space, distinguishes sleep disturbance from clinically diagnosed sleep disorders, evaluates current countermeasures, and identifies priorities for exploration-class missions. Altered light exposure, irregular schedules, high workload, noise, constrained sleeping environments, stress, and possible microgravity-related physiological changes can disrupt coordination between circadian timing and homeostatic sleep pressure. This may result in shortened and fragmented sleep, altered sleep architecture, and insomnia-like symptoms. Evidence from shuttle, International Space Station, and analog missions associates sleep deficiency and circadian misalignment with reduced vigilance, slower psychomotor responses, increased stress, and greater medication use. Timed light, protected sleep opportunities, workload management, environmental control, strategic naps, and carefully selected pharmacological interventions offer complementary benefits, but none is sufficient alone. Long-duration missions will require individualized, multimodal fatigue-risk management integrating validated monitoring, adaptive lighting, autonomous scheduling, and conservative medication protocols. Emerging precision strategies combine wearable physiological biomarkers and research-grade multi-omics profiles with personalized chronotherapy and closed-loop environmental control, although staged validation is required before operational deployment. Key knowledge gaps concern clinically defined sleep disorders, interactions between sleep regulation and other spaceflight hazards, individual and sex-specific responses, and the durability of countermeasures during lunar and Martian missions. Sleep should therefore be treated as a mission-critical system variable rather than solely as an individual medical complaint.
Long-duration missions beyond low Earth orbit will expose crews to prolonged microgravity during transit and partial gravity on the Moon or Mars. Existing exercise, nutritional, pharmacological, and sensorimotor countermeasures mitigate selected aspects of deconditioning but do not reproduce gravity’s continuous multisystem stimulus. Artificial gravity (AG), generated by rotation, is therefore a promising integrative countermeasure. This structured narrative review evaluates the physiological rationale for AG, evidence from human centrifugation and ground-based analog studies, human-factors and engineering constraints, and priorities for exploration missions. Evidence is strongest for the acute restoration of hydrostatic gradients and cardiovascular loading and is suggestive, although heterogeneous, for preserving orthostatic tolerance, muscle function, and selected sensorimotor outcomes. In the 60-day AGBRESA study (24 participants; eight per group), daily continuous or intermittent centrifugation attenuated the decline in time to presyncope relative to control but did not prevent several autonomic, ocular, balance, or mobility changes. Evidence for durable protection of bone, connective tissues, neuro-ocular health, immunity, endocrine and circadian regulation, cognition, sleep, and behavioural health remains insufficient. Interpretation is limited by small samples, overlapping cohort analyses, heterogeneous exposure geometries and schedules, and reliance on bed-rest analogs rather than in-flight trials. AG should therefore be regarded as a configurable intervention rather than a single countermeasure. Translation requires standardized reporting, adequately powered comparative studies, explicit safety and ethical governance, analyses of sex-related and individual responses, combined AG–exercise protocols, and phased validation from ground-based analogs to orbital demonstrators.
Long-duration space missions expose crews to isolation, confinement, operational workload, disrupted sleep and limited resupply, all of which may affect psychological health and mission performance. This narrative review examines whether, through which pathways and under what operational constraints culturally familiar foods could support astronauts’ mental resilience. Evidence was integrated from spaceflight and space-food research, isolated and confined environments, nutritional psychiatry, the microbiota-gut-brain axis and terrestrial studies of cultural food practices. The literature supports two complementary pathways: biological effects mediated by dietary composition and the microbiota-gut-brain axis, and psychosocial effects mediated by identity, nostalgia, familiarity, agency and social connection. Direct evidence in astronaut populations is currently insufficient; consequently, terrestrial and analogue findings should be interpreted as hypothesis-generating rather than confirmatory. We propose a conceptual framework in which cultural familiarity is treated as a design attribute of space food systems alongside safety, nutritional adequacy, stability, usability, resource efficiency, reliability, variety and palatability. Priority studies should test culturally matched foods in controlled analogues and spaceflight using predefined psychological, dietary, microbiome and team-level outcomes.
The increasing frequency of debris-generation events over the last decade has driven the development of debris environmental and evolutionary models that categorize debris motion and flux in the near-Earth environment. Among these populations, debris smaller than 10 cm represents a disastrous population with mission-ending capabilities and is disproportionately represented in current debris models due to a lack of measurements and tracking data, leading to increased uncertainty and associated risks. Current frameworks differ in their assumptions regarding the generation, evolution, and validation of sub-10 cm orbital debris. Evolutionary and environmental models each rely on distinct assumptions, validation data, and debris-generation physics. These explicit differences contribute to the lack of comparability and increased uncertainty across debris frameworks. Recent cross-model comparisons reveal flux disagreements of roughly a factor of two to three at the centimeter scale, widening to an order of magnitude or more below 1 mm, which underscores the difficulty of characterizing the sub-10 cm regime. Categorizing the differing assumptions will, in turn, identify validation gaps and help correct errors and uncertainties related to sub-10 cm debris prediction and validation.
