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1.
Microbiome ; 12(1): 62, 2024 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-38521963

RESUMO

BACKGROUND: The International Space Station (ISS) stands as a testament to human achievement in space exploration. Despite its highly controlled environment, characterised by microgravity, increased CO 2 levels, and elevated solar radiation, microorganisms occupy a unique niche. These microbial inhabitants play a significant role in influencing the health and well-being of astronauts on board. One microorganism of particular interest in our study is Enterobacter bugandensis, primarily found in clinical specimens including the human gastrointestinal tract, and also reported to possess pathogenic traits, leading to a plethora of infections. RESULTS: Distinct from their Earth counterparts, ISS E. bugandensis strains have exhibited resistance mechanisms that categorise them within the ESKAPE pathogen group, a collection of pathogens recognised for their formidable resistance to antimicrobial treatments. During the 2-year Microbial Tracking 1 mission, 13 strains of multidrug-resistant E. bugandensis were isolated from various locations within the ISS. We have carried out a comprehensive study to understand the genomic intricacies of ISS-derived E. bugandensis in comparison to terrestrial strains, with a keen focus on those associated with clinical infections. We unravel the evolutionary trajectories of pivotal genes, especially those contributing to functional adaptations and potential antimicrobial resistance. A hypothesis central to our study was that the singular nature of the stresses of the space environment, distinct from any on Earth, could be driving these genomic adaptations. Extending our investigation, we meticulously mapped the prevalence and distribution of E. bugandensis across the ISS over time. This temporal analysis provided insights into the persistence, succession, and potential patterns of colonisation of E. bugandensis in space. Furthermore, by leveraging advanced analytical techniques, including metabolic modelling, we delved into the coexisting microbial communities alongside E. bugandensis in the ISS across multiple missions and spatial locations. This exploration revealed intricate microbial interactions, offering a window into the microbial ecosystem dynamics within the ISS. CONCLUSIONS: Our comprehensive analysis illuminated not only the ways these interactions sculpt microbial diversity but also the factors that might contribute to the potential dominance and succession of E. bugandensis within the ISS environment. The implications of these findings are twofold. Firstly, they shed light on microbial behaviour, adaptation, and evolution in extreme, isolated environments. Secondly, they underscore the need for robust preventive measures, ensuring the health and safety of astronauts by mitigating risks associated with potential pathogenic threats. Video Abstract.


Assuntos
Anti-Infecciosos , Enterobacter , Microbiota , Voo Espacial , Humanos , Astronave , Microbiota/genética , Genômica
2.
Astrobiology ; 24(3): 230-274, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38507695

RESUMO

As focus for exploration of Mars transitions from current robotic explorers to development of crewed missions, it remains important to protect the integrity of scientific investigations at Mars, as well as protect the Earth's biosphere from any potential harmful effects from returned martian material. This is the discipline of planetary protection, and the Committee on Space Research (COSPAR) maintains the consensus international policy and guidelines on how this is implemented. Based on National Aeronautics and Space Administration (NASA) and European Space Agency (ESA) studies that began in 2001, COSPAR adopted principles and guidelines for human missions to Mars in 2008. At that point, it was clear that to move from those qualitative provisions, a great deal of work and interaction with spacecraft designers would be necessary to generate meaningful quantitative recommendations that could embody the intent of the Outer Space Treaty (Article IX) in the design of such missions. Beginning in 2016, COSPAR then sponsored a multiyear interdisciplinary meeting series to address planetary protection "knowledge gaps" (KGs) with the intent of adapting and extending the current robotic mission-focused Planetary Protection Policy to support the design and implementation of crewed and hybrid exploration missions. This article describes the outcome of the interdisciplinary COSPAR meeting series, to describe and address these KGs, as well as identify potential paths to gap closure. It includes the background scientific basis for each topic area and knowledge updates since the meeting series ended. In particular, credible solutions for KG closure are described for the three topic areas of (1) microbial monitoring of spacecraft and crew health; (2) natural transport (and survival) of terrestrial microbial contamination at Mars, and (3) the technology and operation of spacecraft systems for contamination control. The article includes a KG data table on these topic areas, which is intended to be a point of departure for making future progress in developing an end-to-end planetary protection requirements implementation solution for a crewed mission to Mars. Overall, the workshop series has provided evidence of the feasibility of planetary protection implementation for a crewed Mars mission, given (1) the establishment of needed zoning, emission, transport, and survival parameters for terrestrial biological contamination and (2) the creation of an accepted risk-based compliance approach for adoption by spacefaring actors including national space agencies and commercial/nongovernment organizations.


Assuntos
Marte , Voo Espacial , Humanos , Meio Ambiente Extraterreno , Exobiologia , Contenção de Riscos Biológicos , Astronave
3.
PLoS One ; 19(2): e0292539, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38422052

RESUMO

The PbGA-DDPG algorithm, which uses a potential-based GA-optimized reward shaping function, is a versatiledeep reinforcement learning/DRLagent that can control a vehicle in a complex environment without prior knowledge. However, when compared to an established deterministic controller, it consistently falls short in terms of landing distance accuracy. To address this issue, the HYDESTOC Hybrid Deterministic-Stochastic (a combination of DDPG/deep deterministic policy gradient and PID/proportional-integral-derivative) algorithm was introduced to improve terminal distance accuracy while keeping propellant consumption low. Results from extensive cross-validated Monte Carlo simulations show that a miss distance of less than 0.02 meters, landing speed of less than 0.4 m/s, settling time of 20 seconds or fewer, and a constant crash-free performance is achievable using this method.


Assuntos
Reforço Psicológico , Astronave , Recompensa , Aprendizagem , Algoritmos
4.
Radiat Res ; 201(2): 93-103, 2024 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-38171489

RESUMO

The pervasiveness of deep space radiation remains a confounding factor for the transit of humans through our solar system. Spacecraft shielding both protects astronauts but also contributes to absorbed dose through galactic cosmic ray interactions that produce secondary particles. The resultant biological effects drop to a minimum for aluminum shielding around 20 g/cm2 but increase with additional shielding. The present work evaluates for the first time, the impact of secondary pions on central nervous system functionality. The fractional pion dose emanating from thicker shielded spacecraft regions could contribute up to 10% of the total absorbed radiation dose. New results from the Paul Scherrer Institute have revealed that low dose exposures to 150 MeV positive and negative pions, akin to a Mars mission, result in significant, long-lasting cognitive impairments. These surprising findings emphasize the need to carefully evaluate shielding configurations to optimize safe exposure limits for astronauts during deep space travel.


Assuntos
Radiação Cósmica , Mésons , Proteção Radiológica , Voo Espacial , Humanos , Astronave , Radiação Cósmica/efeitos adversos , Proteção Radiológica/métodos , Astronautas , Cognição , Doses de Radiação
5.
Astrobiology ; 24(1): 100-113, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38227836

RESUMO

The health of astronauts during space travel to new celestial bodies in the Solar System is a critical factor in the planning of a mission. Despite cleaning and decontamination protocols, microorganisms from the Earth have been and will be identified on spacecraft. This raises concerns for human safety and planetary protection, especially if these microorganisms can evolve and adapt to the new environment. In this study, we examined the tolerance of clinically relevant nonfastidious bacterial species that originate from environmental sources (Burkholderia cepacia, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Serratia marcescens) to simulated martian conditions. Our research showed changes in growth and survival of these species in the presence of perchlorates, under desiccating conditions, exposure to ultraviolet radiation, and exposure to martian atmospheric composition and pressure. In addition, our results demonstrate that growth was enhanced by the addition of a martian regolith simulant to the growth media. Additional future research is warranted to examine potential changes in the infectivity, pathogenicity, and virulence of these species with exposure to martian conditions.


Assuntos
Marte , Voo Espacial , Humanos , Meio Ambiente Extraterreno , Raios Ultravioleta , Astronave , Bactérias
6.
Life Sci Space Res (Amst) ; 40: 126-134, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38245337

RESUMO

The way that a given environment may influence human mental health is widely established, with decades of research linking anxiety, depression, stress, productivity, and general mood with all facets of a given environment, including noise levels, lighting, air quality, and other factors. The environmental conditions of a space habitat have far reaching consequences for human mental health and should be carefully managed. This manuscript serves to briefly review what is known about the main components of a space habitat (e.g., noise levels, lighting, air quality, privacy, plant life, etc.), and provide specific and clear recommendations for mission planners and space habitat designers. Where appropriate, opportunities for future research are highlighted.


Assuntos
Voo Espacial , Astronave , Humanos , Saúde Mental
7.
Life Sci Space Res (Amst) ; 40: 51-61, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38245348

RESUMO

Numerous technological challenges have been overcome to realize human space exploration. As mission durations gradually lengthen, the next obstacle is a set of physical limitations. Extended exposure to microgravity poses multiple threats to various bodily systems. Two of these systems are of particular concern for the success of future space missions. The vestibular system includes the otolith organs, which are stimulated in gravity but unloaded in microgravity. This impairs perception, posture, and coordination, all of which are relevant to mission success. Similarly, vision is impaired in many space travelers due to possible intracranial pressure changes or fluid shifts in the brain. As humankind prepares for extended missions to Mars and beyond, it is imperative to compensate for these perils in prolonged weightlessness. Possible countermeasures are considered such as exercise regimens, improved nutrition, and artificial gravity achieved with a centrifuge or spacecraft rotation.


Assuntos
Gravidade Alterada , Voo Espacial , Ausência de Peso , Humanos , Astronave , Exercício Físico
8.
Z Med Phys ; 34(1): 31-43, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38030484

RESUMO

The International Partner Agencies of the International Space Station (ISS) present a comparison of the ionizing radiation absorbed dose and risk quantities used to characterize example missions in lunar space. This effort builds on previous collaborative work that characterizes radiation environments in space to support radiation protection for human spaceflight on ISS in low-Earth orbit (LEO) and exploration missions beyond (BLEO). A "shielded" ubiquitous galactic cosmic radiation (GCR) environment combined with--and separate from--the transient challenge of a solar particle event (SPE) was modelled for a simulated 30-day mission period. Simple geometries of relatively thin and uniform shields were chosen to represent the space vehicle and other available shielding, and male or female phantoms were used to represent the body's self-shielding. Absorbed dose in organs and tissues and the effective dose were calculated for males and females. Risk parameters for cancer and other outcomes are presented for selected organs. The results of this intracomparison between ISS Partner Agencies itself provide insights to the level of agreement with which space agencies can perform organ dosimetry and calculate effective dose. This work was performed in collaboration with the advisory and guidance efforts of the International Commission on Radiological Protection (ICRP) Task Group 115 and will be presented in an ICRP Report.


Assuntos
Radiação Cósmica , Voo Espacial , Feminino , Humanos , Masculino , Doses de Radiação , Radiometria , Astronave
9.
Life Sci Space Res (Amst) ; 39: 14-25, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945085

RESUMO

Two DOSimetry TELescopes (DOSTELs) have been measuring the radiation environment in the Columbus module of the International Space Station (ISS) since 2009 in the frame of the DOSIS and DOSIS 3D projects. Both instruments have measured the charged particle flux rate and dose rates in a telescope geometry of two planar silicon detectors. The radiation environment in the ISS orbit is mostly composed by galactic cosmic radiation (GCR) and its secondary radiation and protons from the inner radiation belt in the South Atlantic Anomaly (SAA) with sporadic contributions of solar energetic particles at high latitudes. The data presented in this work cover two solar activity minima and corresponding GCR intensity maxima in 2009 and 2020 and the solar activity maximum and corresponding GCR intensity minimum in 2014/2015. Average dose rates measured in the Columbus laboratory in the ISS orbit from GCR and SAA are presented separately. The data is analyzed with respect to the effective magnetic shielding and grouped into different cut-off rigidity intervals. Using only measurements in magnetically unshielded regions at low cut-off rigidity and applying a factor for the geometrical shielding of the Earth, absorbed dose rates and dose equivalent rates in near-Earth interplanetary space are estimated for the years 2009 to 2022.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Astronave , Doses de Radiação , Monitoramento de Radiação/métodos , Radiometria , Atividade Solar
10.
Life Sci Space Res (Amst) ; 39: 26-42, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945086

RESUMO

The Light Ion Detector for ALTEA (LIDAL) is a new instrument designed to measure flux, energy spectra and Time of Flight of ions in a space habitat. It was installed in the International Space Station (Columbus) on January 19, 2020 and it is still operating. This paper presents the results of LIDAL measurements in the first 17 months of operation (01/2020-05/2022). Particle flux, dose rate, Time of Flight and spectra are presented and studied in the three ISS orthogonal directions and in the different geomagnetic regions (high latitude, low latitude, and South Atlantic Anomaly, SAA). The results are consistent with previous measurements. Dose rates range between 1.8 nGy/s and 2.4 nGy/s, flux between 0.21 particles/(sr cm2 s) and 0.32 particles/(sr cm2 s) as measured across time and directions during the full orbit. These data offer insights concerning the radiation measurements in the ISS and demonstrate the capabilities of LIDAL as a unique tool for the measurement of space radiation in space habitats, also providing novel information relevant to assess radiation risks for astronauts.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Astronave , Atividade Solar , Monitoramento de Radiação/métodos , Doses de Radiação , Íons
11.
Life Sci Space Res (Amst) ; 39: 3-13, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945087

RESUMO

The Radiation monitoring system (RMS) continuously operated in various configurations since the launch of the Zvezda module of the International Space Station (ISS). The RMS consisted of 7 units, namely: the R-16 dosimeter, 4 DB-8 dosimeters, utility and data collection units. The obtained data covers a time of 22 years. This paper analyses the radiation environment variations on board the "Zvezda" module. Variations of the onboard daily dose rate associated with changes of ISS altitude and 11-year cycle galactic cosmic rays' variations are analyzed and discussed. It is shown that the observed increase in the daily dose from 0.20 - 0.25 to 0.35 - 0.50 mGy/day is mostly due to the increase of ISS orbit altitude, resulting in a substantial increase of the dose contribution from the South Atlantic Anomaly (SAA) Region. Dose rate variations in the SAA as well as latitude and longitude dose rate distributions are discussed in detail. Analysis confirms that the well-known westward drift effect of the SAA is clearly visible from radiation dose measurements on the ISS.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Monitoramento de Radiação/métodos , Astronave , Doses de Radiação , Federação Russa
12.
Life Sci Space Res (Amst) ; 39: 43-51, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945088

RESUMO

The data from two Bulgarian-German instruments with the basic name "Radiation Risk Radiometer-Dosimeter" (R3D) are discussed. The R3DR instrument worked inside the ESA EXPOSE-R facility (2009-2010), while R3DR2 worked inside the ESA EXPOSE-R2 facility (2014-2016). Both were outside the Russian Zvezda module on the International Space Station (ISS). The data from both instruments were used for calculation of the neutron dose equivalent rate. Similar data, obtained by the Russian "BTNNEUTRON" instrument on the ISS are used to benchmark the R3DR/R2 neutron dose equivalent rate. The analisys reveals that the "BTNNEUTRON" and R3DR/R2 values are comparable both in the equatorial and in the South Atlantic Anomaly (SAA) regions. The R3DR/R2 values are smaller than the "BTNNEUTRON" values in the high latitude regions. The comparison with the Monte Carlo simulations of the secondary galactic cosmic rays (GCR) neutron ambient dose equivalent rates (El-Jaby and Richardson, 2015, 2016) also shows a good coincidence with the R3DR/R2 spectrometer data obtained in the equatorial and high latitude regions.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Astronave , Doses de Radiação , Radiometria , Nêutrons
13.
Life Sci Space Res (Amst) ; 39: 52-58, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945089

RESUMO

We detect regular particle showers in several compact pixel detectors, distributed over the International Space Station. These showers are caused by high energy galactic cosmic rays, with energies often in the 10 s of TeV or higher. We survey the frequency of these events, their dependence on location on ISS, and their independence of the location of ISS, on its orbit. The Timepix detectors used allow individual particle tracks to be resolved, providing a possibility to perform physical analysis of shower events, which we demonstrate. In terms of radiation dosimetry, these showers indicate certain possible limitations of traditional dosimetric measures, in that (a) the dose measured in small sensor may be less than that received in a larger distribution of matter, such as a human and (b) the spatial and temporal extent of these events represents a regime of poorly documented biological response.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Humanos , Doses de Radiação , Astronave , Radiometria
14.
Life Sci Space Res (Amst) ; 39: 59-66, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945090

RESUMO

The Hybrid Electronic Radiation Assessor (HERA) system is a Timepix-based ionizing radiation detector built for NASA Exploration-class crewed missions. The HERA performs data analysis on-system and generates telemetry messages for ingestion, display, and relay by the spacecraft. Several iterations of the hardware have been flown aboard the International Space Station as payloads to test system operation and gain experience with the hardware in the space radiation environment. The HERA system and its payload operations are described, and data collected by the various HERA systems are presented.


Assuntos
Voo Espacial , Astronave , Radiação Ionizante
15.
Life Sci Space Res (Amst) ; 39: 76-85, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945092

RESUMO

We report the results of the first six years of measurements of so-called fast neutrons on the International Space Station (ISS) with the Radiation Assessment Detector (ISS-RAD), spanning the period from February 2016 to February 2022. ISS-RAD combines two sensor heads, one nearly identical to the single sensor head in the Mars Science Laboratory RAD (MSL-RAD). The latter is described in a companion article to this one. The novel sensor is the FND, or fast neutron detector, designed to measure neutrons with energies in the range from 200 keV to about 8 MeV. ISS-RAD was deployed in February 2016 in the USLAB module, and then served as a survey instrument from March 2017 until May 2020. Data were acquired in Node3, the Japanese Pressurized Module, Columbus, and Node2. At the conclusion of the survey portion of RAD's planned 10-year campaign on ISS, the instrument was stationed in the USLAB; current plans call for it to remain there indefinitely. The radiation environment on the ISS consists of a complex mix of charged and neutral particles that varies on short time scales owing to the Station's orbit. Neutral particles, and neutrons in particular, are of concern from a radiation protection viewpoint, because they are both highly penetrating (since they do not lose energy via direct ionization) and, at some energies, have high biological effectiveness. Neutrons are copiously produced by GCRs and other incident energetic particles when they undergo nuclear interactions in shielding. As different ISS modules have varying amounts of shielding, they also have varying neutron environments. We report results for neutron fluences and dose equivalent rates in various positions in the ISS.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Astronave , Nêutrons Rápidos , Monitoramento de Radiação/métodos , Nêutrons , Doses de Radiação
16.
Life Sci Space Res (Amst) ; 39: 86-94, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945093

RESUMO

The energetic particle radiation environment on the International Space Station (ISS) includes both charged and neutral particles. Here, we make use of the unique capabilities of the Radiation Assessment Detector (ISS-RAD) to measure both of these components simultaneously. The Charged Particle Detector (CPD) is, despite its name, capable of measuring neutrons in the energy range from about 4 MeV to a few hundred MeV. Combined with data from the Fast Neutron Detector (FND) in the 0.2 to 8 MeV range, we present the first broad-spectrum measurements of the neutron environments in various locations within the ISS since an early Bonner-Ball experiment that was conducted before the Station was fully constructed. The data presented here span the time period from February 2016 to February 2022. In addition to presenting broad-spectrum neutron fluence measurements, we show correlations of the measured neutron dose equivalent with charged-particle dose rates. The ratio of charged-particle dose to neutron dose equivalent is found to be relatively stable within the ISS.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Nêutrons Rápidos , Astronave , Doses de Radiação , Monitoramento de Radiação/métodos , Nêutrons
17.
Life Sci Space Res (Amst) ; 39: 95-105, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37945094

RESUMO

Monitoring space radiation is of vital importance for risk reduction strategies in human space exploration. Radiation protection programs on Earth and in space rely on personal and area radiation monitoring instruments. Crew worn radiation detectors are crucial for successful crew radiation protection programs since they measure what each crewmember experiences in different shielding configurations within the space habitable volume. The Space Radiation Analysis Group at NASA Johnson Space Center investigated several compact, low power, real-time instruments for personal dosimetry. Following these feasibility studies, the Crew Active Dosimeter (CAD) has been chosen as a replacement for the legacy crew passive radiation detectors. The CAD device, based on direct ion storage technology, was developed by Mirion Dosimetry Services to meet the specified NASA design requirements for the International Space Station (ISS) and Artemis programs. After a successful Technology demonstration on ISS, the CAD has been implemented for ISS Crew operations since 2020. The current paper provides an overview of the CAD development, ISS results and comparison with the ISS Radiation Assessment Detector (RAD) and the Radiation Environment Monitor 2 (REM2) instruments.


Assuntos
Radiação Cósmica , Monitoramento de Radiação , Voo Espacial , Humanos , Astronave , Dosímetros de Radiação , Radiometria , Monitoramento de Radiação/métodos , Doses de Radiação
18.
Appl Environ Microbiol ; 89(12): e0083223, 2023 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-37982623

RESUMO

IMPORTANCE: Planetary protection at the National Aeronautics and Space Administration (NASA) requires bioburden on certain spacecraft to be estimated via sampling in order to comply with biological cleanliness requirements. To achieve this, the recovery efficiency of devices used to sample the spacecraft pre-launch must be understood and their uncertainty quantified in order to produce the most reasonable estimates of bioburden. This study brings together experiments performed by NASA and the European Space Agency with approved swab and wipe sampling devices, inoculating steel coupons with laboratory strains of Bacillus spp. spores commonly recovered from spacecraft assembly clean rooms (B. atrophaeus, B. megaterium, B. safensis and B. thuringiensis), with a mathematical model of the assay process to assess recovery efficiency. The statistical treatment developed in this study allows comparison of bioburden estimates made from different devices processed by different methods. This study also gives stakeholders and practitioners a statistically rigorous approach to predict bioburden that can be folded into future modeling efforts.


Assuntos
Bacillus , Astronave , Esporos Bacterianos , Manejo de Espécimes , Laboratórios
19.
Radiat Res ; 200(5): 421-430, 2023 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-37758050

RESUMO

The ionizing radiation exposure to crew on current and future space missions can significantly increase their health risks for cancers, degenerative diseases, and other acute and late effects. A common approach for estimating risk to crew is by completing stochastic (e.g., Monte Carlo) or deterministic particle transport simulations. Within the simulated environment, a small fraction of the particle histories tracked will interact with the astronaut or detector, particularly for larger spacecraft such as the International Space Station, Tiangong Space Station or Lunar Gateway. These simulations can be computationally intensive as they require a very large number of particle histories to achieve a low statistical uncertainty. Variance reduction techniques are applied to simulations to reduce the computational time of the simulation while maintaining the same (or less) statistical uncertainty. The variance reduction technique developed herein involves applying a directional source bias to an isotropic radiation field, such as galactic cosmic rays, to reduce the quantity of particles that have a low probability of interacting with the astronaut or detector. A custom application has been developed utilizing the Geant4 Toolkit that computes the trajectories and energies of particles in three dimensions in the International Space Station using the Monte Carlo method. The results demonstrate the impact of our variance reduction technique on effective dose equivalence depending on: primary and secondary particle type (proton, neutron, photon, heavy ion, etc.), geometric volumes and spacecraft materials. Our variance reduction technique can be tuned by the user to optimize the simulation time depending on their objectives and enables rapid testing of different shield configurations and materials. This variance reduction technique is implemented easily using several input parameters for boundary conditions. Recommended values are presented for rapid implementation in simulations.


Assuntos
Radiação Cósmica , Astronave , Humanos , Astronautas , Radiação Cósmica/efeitos adversos , Nêutrons , Doses de Radiação
20.
Astrobiology ; 23(8): 835-845, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37584746

RESUMO

To support NASA's Mars 2020 mission, bioassays were performed to ensure the biological cleanliness of the spacecraft, instruments, and hardware assembly areas. Bioassays began in May 2014, as the first components were assembled, and continued until their launch in July 2020. Over this 6-year period, 1811 bioassay sampling sessions were conducted. To understand the nature of microbiological presence on and around the spacecraft, an archive of organisms resulting from the bioassays was assembled. This archive included 4232 microbial specimens preserved as frozen stocks. To date, more than 3489 microbial isolates have been tested by MALDI-TOF mass spectrometry analysis. Identifications were based on high confidence level matches to known microorganisms in the reference spectra database where 39 distinct genera were identified. Gram-positive bacteria were isolated almost exclusively. Most, but not all, were spore-forming genera. The most prevalent genera isolated in order of frequency were Bacillus, Priestia, Paenibacillus, Staphylococcus, Micrococcus, and Streptomyces. Within the largely represented Bacillus-like genera, the five most prevalent species were cereus, licheniformis, horneckiae, subtilis, and safensis.


Assuntos
Bacillus , Marte , Astronave
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