Functional and parametric degradation of microcircuits due to total ionizing dose (TID) often poses serious obstacles to deployment of critical state-of-the-art (SOTA) technologies in NASA missions. Moreover, because device dielectrics in which such degradation occurs vary from one fabrication lot to the next, these effects must be reevaluated on a lot-by-lot basis. Often, the most effective mitigation against TID degradation is the addition of radiation shielding to the electronics box. Unfortunately, shielding materials can add significant amounts of mass to a system, particularly when vulnerable parts require shielding over 4π steradians. One method for reducing mass is to apply spot shielding located only on the critical components that require it. Reduced box- and/or spacecraft-level shielding will necessitate more complex spot shielding to protect the component from the omnidirectional radiation environment.
It is important to consider collateral shielding provided by neighboring components or larger objects within the spacecraft in order to minimize the shield footprint. Such patterned design complexities involve painstaking fabrication and installation, and the shielding effectiveness must be verified with three-dimensional ray-trace analysis. Small package sizes make component-level shielding fabrication even more challenging. Three-dimensional (3D) printing technology offers promising breakthroughs in the design and deployment of radiation shielding optimized to the capability of the component, the mission radiation environment, and the shielding already provided by the component’s surroundings. However, in order for that potential to be realized, a thorough understanding of radiation transport through the shielding materials is essential so that the most efficient shielding design can be developed and turned into a CAD model for input to the 3D printer. This work leverages existing particle transport codes to develop tools for constructing such CAD models. The NOVICE transport code is well suited to this task as a result of its modular nature, efficiency, and flexibility. Using knowledge of the external space radiation environments and existing electronics box-level defined radiation environments, such as those for the Magnetospheric Multiscale mission (MMS), a method was developed for constructing patterned-shield CAD models for use with direct metal laser sintering (DMLS) 3D printing technology.
This work introduces state-of-the-art electronics, increasing performance while decreasing hardware complexity, volume, and power. Mass is saved by enabling use of lightweight spacecraft structural materials and making up the difference in shielding with spot shielding located only on critical components that require it. Moreover, it does so efficiently by capitalizing on previous DMLS capability analyses, expanding applications of this promising technology. It also reduces the infusion risk of new electronics technology.
Although every mission would likely benefit from the development of this capability, the greatest benefits would accrue for long-duration missions; missions in harsh radiation environments such as the radiation belts of Earth, Jupiter, and Saturn; and small-satellite development initiatives such as NASA’s Edison Small Satellite Demonstration Program, since small satellites provide little shielding against the space radiation environment.