Refuge Sphere v9.0 — Lightweight Optimized Design: A Superconducting Double-Sphere Radiation Shelter for Interplanetary Crewed Missions

Version 9.0 of the Refuge Sphere technical engineering document. This release introduces two mass-optimized variants of the superconducting radiation shelter concept, both maintaining identical shielding performance to the baseline design. Variant A (Standard Optimized, 6 crew): ~11,539 kg, compatible with SLS Block 1, SLS Block 2, Falcon 9, and Starship. Variant B (Compact Commercial, 4 crew): ~8,580 kg (under 10,000 kg with 15% safety margin), primary launcher Falcon 9 — reducing launch costs by 30× compared to government heavy-lift vehicles and making the system accessible to commercial operators. Optimization strategy: inner sphere aluminum replaced by conductive CFRP 3 mm (CS buckling 3.8, compliant with aerospace standards); internal structure aluminum replaced by CFRP; HDPE shielding reinforced with 5% carbon nanotubes (CNT), allowing 10–15% thickness reduction with identical proton stopping power. Shielding performance (all variants): B = 0 internal (Meissner effect, YBCO film at 77 K), E = 0 internal (Faraday cage), protons 100% stopped up to 170 MeV, estimated dose < 1 mSv per class-X SPE event with SC active (protection factor > 1,000×). Standby power: ~2.4 kW (64% lower than equivalent active toroidal design). Document contains: Introduction, General System Description, Magnetic System, Energy System, Thermal System, Structural System, Radiation Shielding Analysis, Mass Budget, Lightweight Optimization (Variant A and B), Access and Interfaces, Operational Modes, Limitations and Future Developments, Appendices 1–3, References. Technical Annexes (Appendices 4–9) published as companion document. Related to: DOI 10.5281/zenodo.19717390 (previous version v8.0b), DOI 10.5281/zenodo.19690549 (abstract).