Spacecraft Radiation Research Articles

Model‐Based Systems Engineering Approach for Designing an Artificial Magnetic Field Generator System for Spacecraft Radiation Protection

AbstractThe hazardous environment of space, dominated by cosmic and solar radiation, poses a significant threat to spacecraft and their occupants. Traditional radiation shielding methods, like passive materials, have limitations in weight and effectiveness. An artificial magnetic field generator system emerges as a promising solution to replicate Earth's magnetosphere, providing a protective magnetic shield against harmful radiation. (Dick, Launius, 2007) This paper presents a Model‐Based Systems Engineering (MBSE) approach to the holistic modeling and design of such a system.Utilizing the MBSE approach, this study models the system's components, their interactions, and the offered services, incorporating Radiation Monitoring, Magnetic Shielding, Power Management, System Health & Diagnostics, and Crew Communication services. The conceptual data model captures key entities and their relationships, ensuring a coherent integration of the system's parts. The activity diagram illustrates the operational flow, providing clarity on the system's dynamic behavior under varying radiation conditions and power reserves. A services taxonomy is developed to hierarchically categorize and ensure the comprehensive functionality of the system.The application of MBSE methodology provides numerous advantages, including a unified visualization of the system's complexities, enhanced stakeholder communication, and a streamlined validation and verification process. Furthermore, the flexibility inherent in the MBSE approach ensures that the system can be easily updated or scaled based on advancements in technology or changing mission requirements. (ECLIPSE Suite, 2022) The MBSE approach's application to the design of an artificial magnetic field generator system for spacecraft presents a robust and systematic method to ensure optimal performance, safety, and adaptability in the perilous realm of space.

Generalized hierarchical expected improvement method based on black-box functions of adaptive search strategy

With the improvement of the accuracy of numerical simulation experiments, the computational costs of black–box function problems are increasing. In the process of global optimization using the Bayesian optimization method, the sampling cost and the optimization accuracy are the keys for measuring the effectiveness of the Bayesian optimization method. The expected improvement method has a closed-form of the acquisition function, which can realize the effective use of the sampled points, thereby reducing the sampling cost and improving the optimization accuracy. Therefore, this method has been widely used to solve practical engineering problems. The current expected improvement methods are based on fixed local–global search strategy. These methods have difficulty adapting to black-box functions of different complexities, and they have significant limitations in balancing local and global search capabilities. This article proposes a generalized hierarchical expected improvement (GHEI) Bayesian optimization method with an adaptive search strategy. By introducing the balance parameters to adjust the improvement functions, the local–global search criterion is further changed. On this basis, an adaptive search strategy based on the equivalent expectation to improve the optimization is proposed, and it improves the ability to deal with black-box functions of different complexities. The accuracy of the hierarchical Gaussian process model is further improved through methods such as related parameter estimation, hyperparameter determination, and basis function order selection. Comparative analysis with numerical calculation examples verified the effectiveness of the proposed method. Finally, the adaptive GHEI method is applied on the spacecraft radiation resistance equivalent test analysis, and results show that the adaptive GHEI method exhibits a strong search efficiency and applicability .

On the Formation of Phantom Electron Phase Space Density Peaks in Single Spacecraft Radiation Belt Data

AbstractThis study examines the rapid losses and acceleration of trapped relativistic and ultrarelativistic electron populations in the Van Allen radiation belt during the September 7–9, 2017 geomagnetic storm. By analyzing the dynamics of the last closed drift shell (LCDS), and the electron flux and phase space density (PSD), we show that the electron dropouts are consistent with magnetopause shadowing and outward radial diffusion to the compressed LCDS. During the recovery phase, an in‐bound pass of Van Allen Probe A shows an apparent local peak in PSD, which does not exist in reality. A careful analysis of the multipoint measurements by the Van Allen Probes reveals instead how the apparent PSD peak arises from aliasing monotonic PSD profiles which are rapidly increasing due to acceleration from very fast inwards radial diffusion. In the absence of such multisatellite conjunctions during fast acceleration events, such peaks might otherwise be associated with local acceleration processes.

Consideration of particle wave diffraction to enhance spacecraft radiation shielding

Recent advances in atomic microscopy and interferometry have made evident the possibility that the wave-like behavior of Galactic Cosmic Ray (GCR) particle radiation and its secondary emissions can be exploited by diffraction through passive shielding materials to reduce the harmful impact to humans and equipment traveling in deep space. This research examines an additional physical mechanism to the well accepted “stopping power” and “nuclear collision” processes determined by the Bethe-Bloch and Bradt-Peters equations, in order to enhance shielding effectiveness: that the wave-like behavior of GCR radiation and its secondary emissions can be used to reduce the harmful impact of the radiation. Thus, it is shown theoretically possible to passively alter the path of some GCR particle radiation by diffraction, thereby directing them laterally and presenting the possibility that diffraction “safe zones” could be created behind a shielding material that may enhance its effectiveness. Preliminary analysis indicates the best application may be in shielding dangerous neutron secondary emissions.

Impact of Earth’s Magnetic Field Secular Drift on the Low-Altitude Proton Radiation Belt From 1900 to 2050

The effects of the space radiation environment on spacecraft systems and instruments are significant design considerations for space missions. In order to meet these challenges and have reliable, cost-effective designs, the radiation environment must be understood and accurately modeled. The low-altitude proton environment varies slowly in time due to the secular drift of Earth’s main magnetic field and due to the evolution of the solar cycle. The purpose of this paper is to extend the onera proton altitude low model capabilities by introducing a prediction of Earth’s main magnetic field model up to the year 2050. Impact on low-altitude spacecraft radiation specification for next space missions is then assessed.

Research progress of space radiation protection technologies in manned deep space exploration missions

Unlike the low-Earth orbit (LEO) project, space radiation, mainly coming from galactic cosmic radiation (GCR) and solar particle event (SPE), has been generally considered to be one of the most important health risk factors for astronauts in manned deep space exploration missions. In fact, space radiation environment in deep space is substantially different from that in low Earth orbit, in which high-energy protons and heavy nuclei provide the main contribution to the equivalent dose and health risk. Both the total equivalent dose and health risk in deep space are significantly higher than those in LEO missions, which may exceed the permissible radiation exposure limits in the career of astronauts. And, health risks from space radiation exposure remain a primary concern for manned deep space explorations. Space radiation protection is an important strategy to reduce astronauts’ risks of damage and disease induced by space radiation and ensure their health and safety in manned deep space exploration missions. Therefore, space radiation protection is considered to be an important technical problem to be solved in the further manned spaceflight project. However, the complexity and particularity of space radiation environment in manned deep space exploration missions make space radiation protection extremely difficult. Based on the analysis of space radiation environment characteristics in manned deep space exploration missions, this review systematically summarizes and analyzes the current research progresses of space radiation protection, including physical protection and biomedical protection. In general, the physical protection refers to the passive shielding and acitve shielding. The passive shielding of materials with different thickness is the simplest and feasible physical countermeasure to deal with deep space radiation, especially in the case of SPE occurrences. The passive shielding technologies were raised and reviewed from four aspects, including radiation shielding performance indexes and their applications in new material selections, manned spacecraft radiation shielding, personal radiation shielding, and astral surface soil radiation shielding. However, the passive shielding is problematic for GCR due to the penetration of primary high-energy particles, the production of secondary radiation and the mass constraints of manned spacecraft. While, active shielding, involving the generation of electromagnetic fields to deflect space radiation, is a promising and interesting technical improvement to overcome challenging technical hindrance to prevent GCR. But different kinds of active shielding technologies, such as electrostatic shielding, plasma shielding, confined and unconfined magnetic field shielding, have not been applicable in practical cases. Moreover, a series of radioprotectors and radiomitigators in the biomedical protection, including (1) antioxidants, (2) inhibitors of various pathways, (3) cytokines, chemokines, growth factors and hormones, (4) protein molecules, (5) cellular therapeutic agents, and (6) plant derived products, were also summarized and reviewed. Most radioprotectors and radiomitigators are currently being researched and developed under early preclinical phase, and have not been approved by the food and drug administrations. At the same time, the deficiency of some present radioprotectors and radiomitigators, such as the unclear biomedical mechanisms and unavoidable side-effects, limited the popularity in actual applications. In a word, the review points out that the current space radiation protection technologies still face a series of problems and challenges, and puts forward the key technologies and countermeasures of the current space radiation protection. The summary and analysis of the critical challenges and key countermeasures of space radiation protection are of great significance for the follow-up researches and provide a theoretical basis and a solution for the implementation of manned deep space exploration mission.

Influences of mass flow rate on heat and mass transfer performances of water sublimator combined with fluid loop

For spacecraft working in vacuum environment, sublimator is an effective heat rejection approach to reject system’s peak heat load, and supplement spacecraft radiation heat rejection. For a spacecraft active fluid loop thermal control system combined with sublimator, waste heat generated from multi-point distributed heat sources could be collected by the fluid loop efficiently. However, the heat and mass transfer performances of the sublimator combined with fluid loop have not been adequately studied in previous research, especially for the influences of the heat load. Since work fluid mass flow rate is the main factor affecting heat load of the fluid loop, this context experimentally studied influences of the fluid loop mass flow rate on sublimator start-up transient characteristics, including heat transfer performances, response time, and work stability. Results indicated that the fluid loop mass flow rate affected the sublimator heat and mass transfer performances obviously, but the heat rejection ability is not always increase with the increasing of the fluid loop mass flow rate. In addition, we obtained the condition to judge whether there is a positive correlation between heat rejection ability and fluid loop mass flow rate.

New Comparative Metric for Evaluating Spacecraft Radiation Shielding

Given the lack of human medical data available to calibrate and tie the sophisticated model calculations of various space radiation exposure metrics, such as “dose equivalent,” to the actual biological harm expected from long-term exposure to galactic cosmic ray (GCR) radiation in the region of cislunar space [nominally at 1 astronomical unit (AU) from the sun], a new spacecraft shielding evaluation metric is proposed that empirically links to the available medical data collected from International Space Station (ISS) operations, and thereby improves shielding material assessment. Adequate protection from radiation is one of the most important unknowns regarding the contemplated long-term spaceflights beyond the Earth’s protective zone afforded by its magnetosphere. This new radiation shielding evaluation metric relies on a comparison of the relative shielding effectiveness of a particular material or shielding design in the cislunar space radiation environment to the verified radiation exposure environment inside the ISS, where hundreds of astronauts have flown and spent considerable time, and for which there is voluminous medical data and continuing medical observation. Thus, the new metric is a measure of how well a proposed shielding protocol operating in the 1 AU cislunar radiation environment replicates the ISS radiation exposure levels. And, because it is calculated on a strict comparable basis, it mitigates the unavoidable errors introduced in the shielding evaluation process inherent in using different GCR models and radiation transport codes, as well as the various versions of radiation quality or weighting factors.

“BION-M” No. 1 spacecraft radiation environment as observed by the RD3-B3 radiometer-dosimeter in April–May 2013

Space radiation has been monitored using the РД3-Б3 (in the following we use the Latin transcription RD3-B3) spectrometer–dosimeter on board a recent space flight of the Russian recoverable satellite “BION-M” No. 1. The instrument was mounted inside the satellite in a pressurized volume together with biological objects and samples. The RD3-B3 instrument is a battery operated version of the spare model of the R3D-B3 instrument developed and built for the ESA BIOPAN-6 facility on Foton M3 satellite launched on September 2007 (Häder et al., 2009). It is a low mass, small dimension automated device that measures solar radiation in four channels and ionizing radiation in 256 channels of a Liulin-type energy deposition spectrometer (Dachev et al., 2002). Cosmic ionizing radiation has been monitored and separated in 256 deposited energy spectra, which were further used for determination of the absorbed dose rate and flux. The paper summarizes the results for the Earth radiation environment at the altitude of 253–585km.

Tribological behavior of polytetrafluoroethylene coatings based on LY12 substrates in the space environment

The spacecraft space radiation environment was simulated by 60Co source. The polytetrafluoroethylene (PTFE) coatings were fabricated on LY12 substrates. And the effect of gamma (γ) irradiation on the tribological behavior of PTFE coatings under vacuum conditions was investigated. Results indicate that the radiation dose has insignificant effect on the friction coefficient of PTFE coatings, and the wear of PTFE coatings reduces with the increase of gamma dose. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first increased with the increase of sliding velocity and then decreased, and the wear of the PTFE coatings decreased with the increase of sliding speed. As the gamma dose was 100 kGy, the friction coefficient of the PTFE coatings first decreased with the increase of load and then increased, and the wear rate of PTFE coatings increased with the increase of load. Scanning electron microscope was utilized.

Modeling the Response of the ESAPMOS4 RADFETs for the ALPHASAT CTTB Experiment

The Component Technology Test-Bed (CTTB) is one of the main components of the ALPHASAT spacecraft radiation Environment and Effects Facility (AEEF), an European Space Agency (ESA) Technology Demonstration Payload. In-flight data collected by the CTTB experiments will be used to validate ground test protocols, perform prediction models for new component technologies and to provide in-flight evaluation of critical component technologies for use in future missions. The relation between the RADFETs gate threshold voltage shift and the dose can strongly depend on the production processes parameters and needs to be experimentally determined before its use in space. A calibration test campaign of ESAPMOS4 RADFETs was conducted at the ESA/ESTEC Cobalt-60 facility. Irradiation runs were performed at three nominal temperatures: room temperature, 60°C, and 80°C. After the irradiation runs, the units underwent annealing, under similar temperature and bias configuration settings. A model capable of describing the RADFET temperature dependent response during irradiation, at low and high dose rate regimes, is presented in this paper, along with the analysis of the RADFET response during isothermal annealing, following irradiation.

Prompt energization of relativistic and highly relativistic electrons during a substorm interval: Van Allen Probes observations

AbstractOn 17 March 2013, a large magnetic storm significantly depleted the multi‐MeV radiation belt. We present multi‐instrument observations from the Van Allen Probes spacecraft Radiation Belt Storm Probe A and Radiation Belt Storm Probe B at ~6 Re in the midnight sector magnetosphere and from ground‐based ionospheric sensors during a substorm dipolarization followed by rapid reenergization of multi‐MeV electrons. A 50% increase in magnetic field magnitude occurred simultaneously with dramatic increases in 100 keV electron fluxes and a 100 times increase in VLF wave intensity. The 100 keV electrons and intense VLF waves provide a seed population and energy source for subsequent radiation belt enhancements. Highly relativistic (>2 MeV) electron fluxes increased immediately at L* ~ 4.5 and 4.5 MeV flux increased >90 times at L* = 4 over 5 h. Although plasmasphere expansion brings the enhanced radiation belt multi‐MeV fluxes inside the plasmasphere several hours postsubstorm, we localize their prompt reenergization during the event to regions outside the plasmasphere.

The Future of Spacecraft Radiation Design: A Workshop at Aberystwyth University, UK, 28–30 November 2012

Key Points Future of Spacecraft Radiation design

On Convertibility From Antenna to Sensor Brightness Temperature for ATMS

The Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-orbiting Partnership (NPP) satellite is a total power radiometer and scans across the track within a range of ±52.77° from nadir. It has 22 channels and measures the microwave radiation at either quasi-vertical or quasi-horizontal polarization from the Earth's atmosphere. Without simultaneous measurements at both polarizations at the same frequency, the conversion from ATMS antenna temperature to sensor brightness temperature becomes nonunique if the antenna subsystem has a significant spillover from cross-polarization. In addition, the antenna temperature could be contributed from both the near- and far-field radiation through the sidelobes of the ATMS antenna subsystem. An analysis of the ATMS antenna gain measurements reveals that the efficiencies of both ATMS antenna sidelobes and cross-polarization are frequency dependent. From the ATMS pitchover maneuver data, it is found that the contributions of spacecraft radiation through the near-field sidelobes are significant and dominates the scan-angle-dependent features in the ATMS antenna temperatures. A theoretical model is developed for the conversion from antenna to sensor brightness temperatures, which incorporates the angular dependent terms derived from the pitchover maneuver data.

The transient observation-based particle (TOP) model and its potential application in radiation effects evaluation

The evaluation of the radiation hazards on components used in space environment is based on the knowledge of the radiation level encountered on orbit. The models that are widely used to assess the near-Earth environment for a given mission are empirical trapped radiation models derived from a compilation of spacecraft measurements. However, these models are static and hence are not suited for describing the short timescale variations of geomagnetic conditions. The transient observation-based particle (TOP)-model tends to break with this classical approach by introducing dynamic features based on the observation and characterization of transient particle flux events in addition to classical mapping of steady-state flux levels. In order to get a preliminary version of an operational model (actually only available for electrons at low Earth orbit, LEO), (i) the steady-state flux level, (ii) the flux enhancements probability distribution functions, and (iii) the flux decay-time constants (at given energy and positions in space) were determined, and an original dynamic model skeleton with these input parameters has been developed. The methodology is fully described and first flux predictions from the model are presented. In order to evaluate the net effects of radiation on a component, it is important to have an efficient tool that calculates the transfer of the outer radiation environment through the spacecraft material, toward the location of the component under investigation. Using the TOP-model space radiation fluxes and the transmitted radiation environment characteristics derived through GEANT4 calculations, a case study for electron flux/dose variations in a small silicon volume is performed. Potential cases are assessed where the dynamic of the spacecraft radiation environment may have an impact on the observed radiation effects.

The Engineering Radiation Monitor for the Radiation Belt Storm Probes Mission

An Engineering Radiation Monitor (ERM) has been developed as a supplementary spacecraft subsystem for NASA’s Radiation Belt Storm Probes (RBSP) mission. The ERM will monitor total dose and deep dielectric charging at each RBSP spacecraft in real time. Configured to take the place of spacecraft balance mass, the ERM contains an array of eight dosimeters and two buried conductive plates. The dosimeters are mounted under covers of varying shielding thickness to obtain a dose-depth curve and characterize the electron and proton contributions to total dose. A 3-min readout cadence coupled with an initial sensitivity of ∼0.01 krad should enable dynamic measurements of dose rate throughout the 9-hr RBSP orbit. The dosimeters are Radiation-sensing Field Effect Transistors (RadFETs) and operate at zero bias to preserve their response even when powered off. The range of the RadFETs extends above 1000 krad to avoid saturation over the expected duration of the mission. Two large-area (∼10 cm2) charge monitor plates set behind different thickness covers will measure the dynamic currents of weakly-penetrating electrons that can be potentially hazardous to sensitive electronic components within the spacecraft. The charge monitors can handle large events without saturating (∼3000 fA/cm2) and provide sufficient sensitivity (∼0.1 fA/cm2) to gauge quiescent conditions. High time-resolution (5 s) monitoring allows detection of rapid changes in flux and enables correlation of spacecraft anomalies with local space weather conditions. Although primarily intended as an engineering subsystem to monitor spacecraft radiation levels, real-time data from the ERM may also prove useful or interesting to a larger community.

Use of Semi-Dipole Magnetic Field for Spacecraft Radiation Protection

There are various methods to shield spacecraft from energetic particles, like one based on the usage of the permanent magnets. At the same time this method is not perfect; it only suggests low intensity magnetic field because of neglecting galactic cosmic radiation effects on human body. In this paper, hyper thin rings as a shield for spacecraft are suggested. Although these rings are lighter than permanent magnets, their ability to protect spaceship with a safe and high intensity magnetic field is higher than the magnets.

Investigating material approximations in spacecraft radiation analysis

During the design process, the configuration of space vehicles and habitats changes frequently and the merits of design changes must be evaluated. Methods for rapidly assessing astronaut exposure are therefore required. Typically, approximations are made to simplify the geometry and speed-up the evaluation of each design. In this work, the error associated with two common approximations used to simplify space radiation vehicle analyses, scaling into equivalent materials and material reordering, are investigated. Over thirty materials commonly found in spacesuits, vehicles, and human bodies are considered. Each material is placed in a material group (aluminum, polyethylene, or tissue), and the error associated with scaling and reordering was quantified for each material. Of the scaling methods investigated, range scaling is shown to be the superior method, especially for shields less than 30 g/cm 2 exposed to a solar particle event. More complicated, realistic slabs are examined to quantify the separate and combined effects of using equivalent materials and reordering. The error associated with material reordering is shown to be at least comparable to, if not greater than, the error associated with range scaling. In general, scaling and reordering errors were found to grow with the difference between the average nuclear charge of the actual material and average nuclear charge of the equivalent material. Based on this result, a different set of equivalent materials (titanium, aluminum, and tissue) are substituted for the commonly used aluminum, polyethylene, and tissue. The realistic cases are scaled and reordered using the new equivalent materials, and the reduced error is shown.

Spacecraft Radiation Shielding Using Ultralightweight Superconducting Magnets

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

The effect of spacecraft radiation sources on electron moments from the Cassini CAPS electron spectrometer

Data from the Cassini plasma spectrometer (CAPS) electron spectrometer (ELS) have been found to be contaminated with an energy-independent background count rate which has been associated with radiation sources on Cassini. In this paper we describe this background radiation and quantitatively assess its impact on numerically integrated electron moments. The general properties of such a background and its effects on numerical moments are derived. The properties of the ELS background are described and a model for the background presented. A model to generate synthetic ELS spectra is presented and used to evaluate the density and temperature of pure noise and then extended to include ambient distributions. It is shown that the presence of noise produces a saturation of the electron density and temperature at quasi-constant values when the instrument is at background, but that these noise level moments are dependent on the floating spacecraft potential and the orientation of the ELS instrument with respect to the spacecraft. When the ambient distribution has a poor signal-to-noise ratio (SNR) the noise determines the density and temperature; however, as the SNR increases (increasing primarily with density) the density and temperature tend to those of the ambient distribution. It is also shown that these noise effects produce highly artificial density–temperature inverse correlations. A method to subtract this noise is presented and shown to correct for the presence of the noise. Simulated error estimates for the density and temperature are also presented. The analysis described in this paper not only applies to weak background noise, but also to more significant penetrating backgrounds such as those in radiation belt regions of planetary magnetospheres.