Piston-Driven Liquid-Liner Magnetized Target Fusion: Energy Balance, Impact Loading, Timing and Economics from an Explicit Parameter Set

Revised version (October 2026) of a first-order, reproducible engineering-economic scoping study of piston-driven liquid-liner magnetized target fusion, built on one explicit parameter set. Main results. (1) The recirculating power of the plant is fixed by the driver gain G (fusion energy per unit of piston kinetic energy): the drive consumes 1/[eta_d eta_th (G+1)] of gross electricity. The reference parameters imply G ≈ 266; keeping total recirculation below 20% requires G ≳ 37, a target-physics figure that, to the author's knowledge, no magnetized-target experiment has approached. (2) Rigid piston impact produces 0.5–1.1 GPa; a compliant interface with a 0.5–1 ms load duration gives safety factors of 2–6 against a conservatively extrapolated gigacycle fatigue strength of AISI 4340 and Ti-6Al-4V, but the design needs very-high-cycle data on real components. (3) Titanium pistons offer no drive-power advantage; under rigid impact on a stiff anvil, steel is the more vulnerable alloy. (4) The symmetry-derived timing tolerance is 0.5–10 µs depending on perturbation growth, so a 1 µs specification is not demonstrably conservative. (5) Net-energy EROI is 4–5 for the reference construction energy; at 20% recirculation the levelised cost of electricity is $113–236/MWh for capital costs of $2–5 billion. This version corrects several conclusions of the previous one (titanium "parasitic power" argument withdrawn, acoustic stress bound corrected, inconsistent fatigue constants replaced and the control-failure conclusion reversed, design-point and cycle-count inconsistencies fixed, EROI convention clarified, HTS appendix re-based on sourced prices); the full list is in Appendix A. All numbers are reproduced by the attached verify.py, which also checks the manuscript against the computation. AI assistance (Anthropic's Claude) was used and is disclosed in the manuscript.