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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS2000

Natural Hazards of the Space Environment

Spacecraft in Low Earth Orbit (LEO) are subject to numerous environmental hazards. Here I'll briefly discuss three environment factors that pose acute threats to the survival of spacecraft systems and crew: atmospheric drag, impacts by meteoroids and orbital debris, and ionizing radiation. Atmospheric drag continuously opposes the orbital motion of a satellite, causing the orbit to decay. This decay will lead to reentry if not countered by reboost maneuvers. Orbital debris is a by-product of man's activities in space, and consists of objects ranging in size from miniscule paint chips to spent rocket stages and dead satellites. Ionizing radiation experienced in LEO has several components: geomagnetically trapped protons and electrons (Van Allen belts); energetic solar particles; galactic cosmic rays; and albedo neutrons. These particles can have several types of prompt harmful effects on equipment and crew, from single-event upsets, latchup, and burnout of electronics, to lethal doses to crew.All three types of prompt threat show some dependence on the solar activity cycle. Atmospheric drag mitigation and large debris avoidance require propulsive maneuvers. M/OD and ionizing radiation require some form of shielding for crew and sensitive equipment. Limiting exposure time is a mitigation technique for ionizing radiation and meteor streams.

Evans, Steven W.↗
NASA NTRS1998

Space Environment Effects: Low-Altitude Trapped Radiation Model

Accurate models of the Earth's trapped energetic proton environment are required for both piloted and robotic space missions. For piloted missions, the concern is mainly total dose to the astronauts, particularly in long-duration missions and during extravehicular activity (EVA). As astronomical and remote-sensing detectors become more sensitive, the proton flux can induce unwanted backgrounds in these instruments. Due to this unwanted background, the following description details the development of a new model for the low-trapped proton environment. The model is based on nearly 20 years of data from the TIRO/NOAA weather satellites. The model, which has been designated NOAAPRO (for NOAA protons), predicts the integral omnidirectional proton flux in three energy ranges: >16, >36, and >80 MeV. It contains a true solar cycle variation and accounts for the secular variation in the Earth's magnetic field. It also extends to lower values of the magnetic L parameter than does AP8. Thus, the model addresses the major shortcomings of AP8.

Huston, S. L.↗
NASA NTRSDate not supplied

Comparison of the Nowcast of Aerospace Ionizing Radiation System (NAIRAS) With ISS Measurements

The Nowcast of Aerospace Ionizing Radiation System (NAIRAS) is a sophisticated physics-based model that has been providing real-time global predictions of cosmic radiation exposure, pertinent to both galactic and solar sources, to air travelers for a decade. The utility of NAIRAS, however, extends beyond the atmospheric ionizing radiation environment. The recently developed NAIRAS 3.0 version demonstrates an expansion of its domain to the space radiation environment. This extension incorporates an additional trapped inner belt proton source, coupled with altitude-dependent and rigidity-dependent geomagnetic shielding for galactic cosmic rays (GCR) and solar energetic particle (SEP) protons. The latest version of NAIRAS operates in two modes: real-time global predictions of the atmospheric radiation environment and a user-specified run-on-request service for global dosimetric calculations or predictions of dosimetric and particle flux quantities along user-uploaded flight path. It is available to the public at the Community Coordinated Modeling Center (CCMC). In this work, we present the validation exercises that have been conducted using the Automated Radiation Measurements for Aerospace Safety (ARMAS) onboard the International Space Station (ISS), thereby establishing NAIRAS's efficacy in predicting space radiation exposure. As such, NAIRAS 3.0 holds significant potential for human safety and technological advancement in aerospace travel and exploration.

Daniel Phoenix↗
NASA NTRSDate not supplied

The Effect of a SEP Event on Astronauts Doing a Spacewalk As Computed By the Nowcast of Aerospace Ionizing Radiation System (NAIRAS)

The Nowcast of Aerospace Ionizing Radiation System (NAIRAS) is a sophisticated physics-based model that has been providing real-time global predictions of cosmic radiation exposure, pertinent to both galactic and solar sources, to air travelers for a decade. The utility of NAIRAS, however, extends beyond the atmospheric ionizing radiation environment. The recently developed NAIRAS 3.0 version demonstrates an expansion of its domain to the space radiation environment. This extension incorporates an additional trapped inner belt proton source, coupled with altitude-dependent and rigidity-dependent geomagnetic shielding for galactic cosmic rays (GCR) and solar energetic particle (SEP) protons. The latest version of NAIRAS operates in two modes: real-time global predictions of the atmospheric radiation environment and a user-specified run-on-request service for global dosimetric calculations or predictions of dosimetric and particle flux quantities along user-uploaded flight path. It is available to the public at the Community Coordinated Modeling Center (CCMC). In this work, we present the computations of the dose in the ISS vicinity during the SEP event of August 8, 2023; which happened a day before a scheduled spacewalk. We demonstrate that astronauts would not have suffered a dose equivalent in excess of 1 mSv if the event happened a day later. As such, NAIRAS 3.0 holds significant potential for human safety and technological advancement in aerospace travel and exploration.

Guillaume Gronoff↗
NASA NTRS2018

The Probability of False Go/No-Go Determined by GOES Proton Flux: Proposed Launch Constraints for Avoiding Damaging Solar Energetic Particle Events

The space environment is full of harmful radiation and high energy particles that can cause damage to materials and affect computer systems by e.g., single event effects (SEEs), total ionizing dose (TID), etc. There are three main sources of high energy particles: Trapped radiation in Earth's Van Allen belts (electrons and protons); Solar energetic particles (SEPs) (protons and heavy ions); Galactic cosmic rays (GCRs) (protons and heavy ions). In this study, we focus on the SEPs and their time series and energy spectrum to quantify probabilities of launch go/no-go. The SEPs originate from solar particle events (SPEs) that are associated with a solar flare and/or a coronal mass ejection (CME). These events are difficult to predict. Recent work has been done on these prediction techniques. The Geostarionary Operational Environmental Satellite (GOES) has been observing SEPs for decades. The greater than 10 megaelectronvolt proton flux is shown in Figure 2 since 1986. The SEPs are influenced by the 11-year solar cycle and typically come from active regions on the Sun.

DeStefano, Anthony M.↗
NASA NTRS1991

The ionizing radiation environment of LDEF prerecovery predictions

The Long Duration Exposure Facility (LDEF) was exposed to several sources of ionizing radiation while in orbit. The principal ones were trapped belt protons and electrons, galactic cosmic rays, and albedo particles (protons and neutrons) from the atmosphere. Large solar flares in 1989 may have caused a small contribution. Prior to the recovery of the spacecraft, a number of calculations and estimates were made to predict the radiation exposure of the spacecraft and experiments. These were made to assess whether measurable radiation effects might exist, and to plan the analysis of the large number of radiation measurements available on the LDEF. Calculations and estimates of total dose, particle fluences, linear energy transfer spectra, and induced radioactivity were made. The principal sources of radiation is described, and the preflight predictions are summarized.

Watts, John W., Jr.↗
NASA NTRS1996

Naval Research Laboratory's programs in advanced indium phosphide solar cell development

The Naval Research Laboratory (NRL) has been involved in the development of solar cells for space applications since the 1960s. It quickly became apparent in this work that radiation damage caused to solar cells by electrons and protons trapped by the earth's magnetic field would seriously degrade the power output of photovoltaic arrays in extended missions. Techniques were therefore developed to harden the cells by shielding them with coverglass, etc. Ultimately, however, there is a limit to such approaches, which is determined by the radiation response of the semiconductor material employed. A desire for high efficiency and radiation resistance led to the development of alternative cell technologies such as GaAs, which has since become the technology of choice for many applications. InP cells are currently the most radiation resistant, high efficiency, planar cells known. NRL first sponsored InP solar cell technology in 1986, when Arizona State University was contracted to grow p/n cells by liquid phase epitaxy. NRL's interest in InP cells was generated by the results presented by Yamaguchi and his co-workers in the early 1980s on the remarkable radiation resistance of cells grown by diffusion of S into Zn doped p-type InP substrates. These cells also had beginning of life (BOL) efficiencies approximately 16%(AM0). Related to the radiation resistance of the cells was the fact that radiation-induced damage could be optically annealed by sunlight. Relatively large quantities of 1 x 2 cm(exp 2) diffused junction cells were made and were used on the MUSES-A and the EXOS-D satellites. These cells were also available in the U.S. through NIMCO, and were studied at NRL and elsewhere. Workers at NASA Lewis became involved in research in InP cells about the same time as NRL.

Summers, Geoffrey P.↗
NASA NTRS2023

NAIRAS Ionizing Radiation Model: Extension from Atmosphere to Space

The Nowcast of Aerospace Ionizing RAdiation System (NAIRAS) model is a real-time, global, physics-based model originally developed to predict exposure from cosmic radiation to air travelers from both galactic and solar sources. A prototype operational NAIRAS model has provided tabular and graphical data products via its public web site for about ten years. A new version of the NAIRAS model has been developed that incorporates an extension of the model domain from the atmospheric ionizing radiation environment to the space radiation environment, with the addition of the trapped inner belt proton source and altitude-dependent and rigidity-dependent geomagnetic shielding of the galactic cosmic rays (GCR) and solar energetic particle (SEP) protons. New output products of differential and integral particle flux have been developed for the characterization of single-event effects (SEE), expanding the application of NAIRAS from human radiation exposure assessment to allowing end-users to quantify radiation environment risks to aviation and spacecraft microelectronic systems. The NAIRAS model has transitioned to prototype operations at the Community Coordinated Modeling Center (CCMC) where the model now operates in two modes: (1) real-time global predictions of the atmospheric radiation environment and (2) a run-on-request (RoR) service allowing the user to select a specific time period for the global dosimetric calculations, or to upload an aircraft, balloon, or spaceflight trajectory file to provide predictions of the dosimetric and particle flux quantities along the flight path. The new features of NAIRAS version 3.0 are described in this paper and example results of the new output products for low-Earth orbit (LEO), medium-Earth orbit (MEO), and free-space radiation environments are presented

Christopher J. Mertens↗
NASA NTRS1999

Initial Biological Damage from Space Radiation: Implications for Development of Biological Countermeasures

Astronauts are exposed to high-energy nuclear particles originating from the galactic cosmic rays, high-energy protons trapped in the Earth's magnetic field or solar particle events, and secondary radiation produced by nuclear reactions. Important differences between conventional radiation including X-rays or gamma-rays, and high-energy nuclei occur at the level of initial damage to DNA and other potential biological target molecules, and to tissues. Such differences include a large fraction of the initial damage from high charge and energy (HZE) nuclear particles manifested as irreparable lesions including small- and large-scale DNA deletions. Also, low dose-rate exposures in space result in a heterogeneous population of damaged cells distinct from energetic photon irradiation of tissue. We present an overview of the initial biological damage and dose and dose-rate effects produced by ionizing radiation using track structure and nuclear reaction models. Implications of the differences in cellular and tissue damage between conventional radiation and space radiation for the development of biological countermeasures are discussed.

Cucinotta, Francis A.↗
NASA NTRS1972

High energy proton model for the inner radiation belt.

Reconsideration of inner radiation belt processes and proton theories. The ability of trapped particles to diffuse across magnetic shells is shown radically to alter the view of magnetospheric processes and to call for such a reconsideration. Inner belt calculations incorporating radial diffusion processes are performed in a manner parametrizing the radial diffusion coefficient. The latter is then varied so as to obtain agreement with experiment. The diffusion coefficient thus obtained is compared with coefficients derived by other means.

Walt, M.↗
NASA NTRS1974

Jupiters radiation belts and their effects on spacecraft

The effects of electron and proton radiation on spacecraft which will operate in the trapped radiation belts of the planet Jupiter are described, and the techniques and results of the testing and simulation used in the radiation effects program are discussed. Available data from the Pioneer 10 encounter of Jupiter are compared with pre-encounter models of the Jupiter radiation belts. The implications that the measured Jovian radiation belts have for future missions are considered.

Parker, R. H.↗
NASA NTRS1974

Jupiter's radiation belts and their effects on spacecraft

The effects of electron and proton radiation on spacecraft which will operate in the trapped radiation belts of the planet Jupiter are considered, and the techniques and results of the testing and simulation used in the radiation effects program at the Jet Propulsion Laboratory are discussed. Available data from the Pioneer 10 encounter of Jupiter are compared with pre-encounter models of the Jupiter radiation belts. The implications that the measured Jovian radiation belts have for future missions are considered.

Parker, R. H.↗
NASA NTRS2001

Neutron Environment Calculations for Low Earth Orbit

The long term exposure of astronauts on the developing International Space Station (ISS) requires an accurate knowledge of the internal exposure environment for human risk assessment and other onboard processes. The natural environment is moderated by the solar wind, which varies over the solar cycle. The HZETRN high charge and energy transport code developed at NASA Langley Research Center can be used to evaluate the neutron environment on ISS. A time dependent model for the ambient environment in low earth orbit is used. This model includes GCR radiation moderated by the Earth's magnetic field, trapped protons, and a recently completed model of the albedo neutron environment formed through the interaction of galactic cosmic rays with the Earth's atmosphere. Using this code, the neutron environments for space shuttle missions were calculated and comparisons were made to measurements by the Johnson Space Center with onboard detectors. The models discussed herein are being developed to evaluate the natural and induced environment data for the Intelligence Synthesis Environment Project and eventual use in spacecraft optimization.

Clowdsley, M. S.↗
NASA NTRS1999

Solar Array Verification Analysis Tool (SAVANT) Developed

Modeling solar cell performance for a specific radiation environment to obtain the end-of-life photovoltaic array performance has become both increasingly important and, with the rapid advent of new types of cell technology, more difficult. For large constellations of satellites, a few percent difference in the lifetime prediction can have an enormous economic impact. The tool described here automates the assessment of solar array on-orbit end-of-life performance and assists in the development and design of ground test protocols for different solar cell designs. Once established, these protocols can be used to calculate on-orbit end-of-life performance from ground test results. The Solar Array Verification Analysis Tool (SAVANT) utilizes the radiation environment from the Environment Work Bench (EWB) model developed by the NASA Lewis Research Center s Photovoltaic and Space Environmental Effects Branch in conjunction with Maxwell Technologies. It then modifies and combines this information with the displacement damage model proposed by Summers et al. (ref. 1) of the Naval Research Laboratory to determine solar cell performance during the course of a given mission. The resulting predictions can then be compared with flight data. The Environment WorkBench (ref. 2) uses the NASA AE8 (electron) and AP8 (proton) models of the radiation belts to calculate the trapped radiation flux. These fluxes are integrated over the defined spacecraft orbit for the duration of the mission to obtain the total omnidirectional fluence spectra. Components such as the solar cell coverglass, adhesive, and antireflective coatings can slow and attenuate the particle fluence reaching the solar cell. In SAVANT, a continuous slowing down approximation is used to model this effect.

Bailey, Sheila G.↗
NASA NTRS2012

Near-Earth Space Radiation Models

Review of models of the near-Earth space radiation environment is presented, including recent developments in trapped proton and electron, galactic cosmic ray and solar particle event models geared toward spacecraft electronics applications.

Xapsos, Michael A.↗
NASA NTRS2015

SRAG Measurements Performed During the Orion EFT-1 Mission

The Exploration Flight Test 1 (EFT-1) was the first flight of the Orion Multi-Purpose Crew Vehicle (MPCV). The flight was launched on December 5, 2014, by a Delta IV Heavy rocket and lasted 4.5 hours. The EFT-1 trajectory involved one low altitude orbit and one high altitude orbit with an apogee of almost 6000 km. As a result of this particular flight profile, the Orion MPCV passed through intense regions of trapped protons and electron belts. In support of the radiation measurements aboard the EFT-1, the Space Radiation Analysis Group (SRAG) provided a Battery-operated Independent Radiation Detector (BIRD) based on Timepix radiation monitoring technology similar to that employed by the ISS Radiation Environmental Monitors (REM). In addition, SRAG provided a suite of optically and thermally stimulated luminescence detectors, with 2 Radiation Area Monitor (RAM) units collocated with the BIRD instrument for comparison purposes, and 6 RAM units distributed at different shielding configurations within the Orion MPCV. A summary of the EFT-1 Radiation Area Monitors (RAM) mission dose results obtained from measurements performed in the Space Radiation Dosimetry Laboratory at the NASA Johnson Space Center will be presented. Each RAM included LiF:Mg,Ti (TLD-100), (6)LiF:Mg,Ti (TLD-600), (7)LiF:Mg,Ti (TLD-700), Al2O3:C (Luxel trademark), and CaF2:Tm (TLD-300). The RAM mission dose values will be compared with the BIRD instrument total mission dose. In addition, a similar comparison will be shown for the ISS environment by comparing the ISS RAM data with data from the six Timepix-based REM units deployed on ISS as part of the NASA REM Technology Demonstration.

Gaza, Ramona↗
NASA NTRS1990

The NSSDC trapped radiation model facility

The National Space Science Data Center (NSSDC) trapped radiation models calculate the integral and differential electron and proton flux for given values of the particle energy E, drift shell parameter L, and magnetic field strength B for either solar maximum or solar minimum. The most recent versions of the series of models, which have been developed and continuously improved over several decades by Dr. James Vette and coworkers at NSSDC, are AE-8 for electrons and AP-8 for protons. The present status of the NSSDC trapped particle models is discussed. The limits of validity of the models are described.

Gaffey, John D., Jr.↗