Spacecraft are self-contained biospheres that must be designed to protect astronauts from harmful aspects of the interplanetary environment. Radiation encountered in deep space poses a significant threat to the health of astronauts and the success of future NASA missions beyond low-Earth orbit. Isotropic galactic cosmic rays (GCRs) and intermittent solar particle events (SPEs) threaten to cause acute radiation sickness and exceed NASA’s permissible exposure limits (PELs) for cancer risk for explorers in near-term space operations. Thus, effective methods of mitigating this radiation risk are high priorities for NSBRI and NASA. This First Award Fellowship will design a magnetic shielding architecture capable of reducing the amount of radiation by a factor of 4 that reaches the astronaut habitat, thus alleviating many biological uncertainties associated with this risk. Through computational modeling, we will investigate the spectra of harmful radiation and will design a “swarm-bot” type magnetic field configuration that will deflect incoming radiation, thus forming a “safe-region” within the astronaut habitat. The novel method proposed here will work in concert with many aspects of existing superconductor technology. This system will be shown to operate in parallel with the existing NASA Orion spacecraft infrastructure and in a continuous mode but without the need for continuous power. The success of the fellowship will lay the groundwork for future laboratory demonstrations and possible mission inclusion of this technology.
Mitigation of the Spacecraft Radiation Environment Via Magnetic Shielding by an Array of Dispersed Superconducting Magnets (First Award Fellowship)
David Chesny, Ph.D.
Florida Institute of Technology
Spacecraft are self-contained biospheres that must be designed to protect astronauts from harmful aspects of the interplanetary environment. Radiation encountered in deep space poses a significant threat to the health of astronauts and the success of future NASA missions to destinations such as asteroids and eventually Mars. It is still an unresolved question how modern technology can provide protection against such an environment. Thus, it is paramount to develop an effective method of radiation shielding to safeguard against this risk. The priority of the National Space Biomedical Research Institute (NSBRI) is to fund research that will deliver countermeasures and technologies for risk mitigation that will ensure the health of astronauts in the space environment. The radiation threat encountered here is twofold: galactic cosmic rays (GCRs) present an isotropic flux of high-energy (~GeV) particles that originate from supernovae, black holes, etc., outside our solar system, and solar particle events (SPEs) are streams of plasma (~MeV) that are emitted intermittently from the atmosphere of our Sun. Extended exposure to GCRs and SPEs presents a significant risk to astronauts of exceeding NASA's stringent permissible exposure limits (PELs), developing potentially catastrophic acute radiation sickness during a mission, increasing the risk of cancer, and even death. Alleviating these vulnerabilities requires the investigation of countermeasures to reduce spacecraft exposure to such dangers and is a major goal of NSBRI.
This will develop a technology that will (1) provide an infrastructure that will reduce the overall radiation environment experienced by a spacecraft by a statistically significant fraction (goal factor 1/4), thus filling gaps in NASA's Integrated Research Plan, (2) complement the use of biological supplements, medications, etc., that alleviate the negative effects of radiation exposure, thus providing a level of redundancy safeguarding astronauts against this threat, (3) show that the design is reconfigurable in response to short-term forecasts of SPEs, (4) provide the specifications of modern technology that will enable such radiation protection in advance of planned human missions beyond low-Earth orbit (LEO), (5) work alongside existing NASA spacecraft infrastructure, and (6) provide outreach in an effort to enhance education and interest in future space exploration. Currently, this technology is at a Countermeasure Readiness Level (CRL) of 3 and a Technology Readiness Level (TRL) of 2. The success of this research will elevate the technology to CRL 5 and TRL 4. The proposed countermeasures will mitigate radiation effects and improve human factors and performance during space missions, both of which are fundamental goals of NASA's Human Research Roadmap.
We propose a previously unexplored architecture for a radiation-protected deep space expedition. The Orion spacecraft itself with command module, astronaut habitat, and service module will not be altered. Instead, a number of relatively small independent mobile satellites, each containing superconducting coils, will form a protective array around the spaceship. These satellites will act as diverging or converging magnetic lenses whose purpose is to reduce the radiation flux passing through the volume occupied by the spaceship. The magnet array will be reconfigurable and its formation will exploit the principles of swarm-bot technology. The individual units can be moved either by their own propulsion or by a designated “tug boat” to form an array suitable for changing space weather conditions. Protection against GCRs requires a practically spherically symmetric magnetic shield which can be created by an array of magnets in a form of a regular polyhedron. In advance of an SPE storm, the array will be reconfigured to form a denser network oriented in the direction of the incoming radiation. Such a capability is a great advantage over the fixed “magnetic armor” because the latter has to be designed for the worst case scenario--of GSCs and SPEs--despite SPEs being short-lived threats. The goal of the magnet array is to provide a “safe region” around the spacecraft in which the number density of the charged particles is lower than it would be in the absence of such a shield. Since magnetic fields do not change GCR and SPE particle energy, the dose of radiation absorbed by the biological tissue inside the protected region is reduced by the same proportion as the number density of the particles. This will provide improved constraints for future models of biological responses to radiation and reduce uncertainties in studies of radiation effects.
Developing technologically accessible shielding methods for spacecraft will help constrain Earth-based research into the effects of high-energy radiation on human space performance and health. Calculations of the equivalent dose and relative biological effectiveness of other classes of safeguards (i.e., medications) for radiation protection rely on accurate input radiation levels that will be encountered during long-duration space missions. The shielding method developed in this study will provide such constraints to researchers in order to more effectively cultivate other levels of redundancy against this important radiation threat.