The risk of soft errors due to radiation continues to be a significant challenge for engineers trying to build systems that can handle harsh environments. Building systems that are Radiation Hardened by Design (RHBD) is the preferred approach, but existing techniques are expensive in terms of performance, power, and/or area... This paper introduces a novel soft-error resilient asynchronous bundled-data design template, SERAD, which uses a combination of temporal and spatial redundancy to mitigate Single Event Transients (SETs) and upsets (SEUs). SERAD uses Error Detecting Logic (EDL) to detect SETs at the inputs of sequential elements and correct them via re-sampling. Because SERAD only pays the delay penalty in the presence of an SET, which rarely occurs, its average performance is comparable to the baseline synchronous design. We tested the SERAD design using a combination of Spice and Verilog simulations and evaluated its impact on area, frequency, and power on an open-core MIPS-like processor using a NCSU 45nm cell library. Our post-synthesis results show that the SERAD design consumes less than half of the area of the Triple Modular Redundancy (TMR), exhibits significantly less performance degradation than Glitch Filtering (GF), and consumes no more total power than the baseline unhardened design. (read more)