Refuge Sphere: A Superconducting Double-Sphere Radiation Shelter for Interplanetary Crewed Missions

This document presents a conceptual design for the Refuge Sphere, a radiation protection module for crewed interplanetary spacecraft. The system is designed to protect crew members during extreme radiation events including Van Allen belt crossings, Solar Particle Events (SPE), Coronal Mass Ejections (CME), and Galactic Cosmic Ray (GCR) exposure. The core physical principle is the Meissner effect: a 3 μm YBCO superconducting film deposited on the inner surface of a closed spherical CFRP substrate (outer diameter 3,500 mm), cooled to 77 K with liquid nitrogen, expels all external magnetic flux and creates an exactly field-free interior (B = 0). An inner aluminum sphere (diameter 2,800 mm) provides complete electrostatic shielding via the Faraday effect (E = 0). The 290 mm intermediate layer combines HDPE, borated polyethylene, lead laminate, and a Whipple micrometeorite shield. Key results: estimated internal dose during a severe 2-hour class-X SPE is ~20 mSv with passive shielding alone (12× below the NASA emergency limit of 250 mSv), and < 1 mSv with the superconducting Meissner shielding active (protection factor > 1,000×). Standby power consumption is ~2.4 kW — 64% lower than an equivalent active toroidal design. Total system mass is estimated at ~12,250 kg, compatible with heavy-lift vehicles (SLS Block 2, Starship). The concept differs fundamentally from previously studied active toroidal configurations (e.g., EU SR2S project): a closed superconducting sphere achieves B = 0 throughout the entire enclosed volume — an exact and isotropic result — rather than the approximate B ≈ 0 achievable with toroidal geometries. Known limitations include large-scale YBCO film deposition challenges, radiation-induced film degradation over mission timescales, high system mass, and the irreducible GCR high-energy component. Experimental validation with a reduced-scale prototype is identified as the essential next step.