"GNMT–H₂EM Integrated Nuclear Microwave‑Thermal Propulsion with Rotating Electromagnetic Nozzles

GNMT–H₂EM Integrated Propulsion Architecture presents the v16 upgrade of the Nuclear Microwave‑Thermal (NM‑T) propulsion system, unifying the original GNMT framework with the H₂EM‑Field electromagnetic governance architecture. This consolidated design resolves the long‑standing capability gap between low‑thrust electric propulsion and high‑thrust chemical propulsion, enabling continuous high‑acceleration deep‑space missions with transit times previously considered unattainable. The baseline GNMT system employs a 4 MW Prometheus‑lineage fast‑spectrum reactor driving twin Rotating Electromagnetic Nozzles (REMN), delivering 35–45 N continuous thrust at Isp = 3,200–3,900 s. REMN performance derives from helicon RF plasma heating (13.56–27.12 MHz, η_RF = 0.70–0.85), magnetic‑mirror thermal conversion (η_mirror = 0.90–0.97), and J×B Lorentz acceleration, achieving η_noz = 0.85–0.92 — a 15–25% uplift over conventional magnetic nozzle architectures. At 1.0 MW RF and 1.2 mg/s water flow, exhaust velocity reaches 38 km/s (Isp = 3,880 s) with 46 N thrust per channel. The v16 H₂EM‑Field integration introduces upstream microwave cracking, field‑gated plasma initiation, and predictive electromagnetic governance. This produces a hydrogen‑rich propellant stream, stabilises burst‑mode plasma dynamics, and enables multi‑zone ignition timing under DIGSP supervisory control. Literature‑consistent projections indicate 10–30% increases in effective exhaust velocity, yielding Isp ≈ 4,900–5,300 s at comparable RF power and flow. The integration preserves GNMT’s dual‑use water‑pod architecture, providing both propellant and 20–40 cm water‑equivalent crew shielding (2–4× GCR dose reduction), eliminating 20–30 tonnes of dedicated shielding mass. Mission analysis for a 100‑tonne reference vehicle shows that in governed burst‑mode, GNMT–H₂EM v16 operates in a fundamentally different transit regime. With field‑gated confinement, multi‑zone cracking/ignition sequencing, and REMN‑stabilised plasma acceleration, the architecture supports sustained high‑acceleration cruise. Updated v16 trajectories yield approximately 4 months for a Jupiter return, 6–7 months for Saturn, and 9–10 months for Pluto, shifting outer‑solar‑system logistics from multi‑year expeditions to operational‑timescale missions. These figures represent falsifiable projections grounded in laboratory‑validated physics, not speculative extrapolation. All subsystems derive from experimentally demonstrated technologies, including helicon RF sources (TRL 9), GaN HEMT burst‑mode amplifiers, magnetic‑mirror nozzle demonstrations, and the Prometheus/JIMO fast‑spectrum reactor lineage (PDR‑validated, 2005). A four‑phase validation pathway targets TRL 8–9 at a programme cost of $80–150M, consistent with NASA Discovery‑class scale. This work forms part of the Griffiths Canon, a developing series on electromagnetically governed hydrogen systems, including the GREMN geometry‑stabilised nozzle, the REMN augmentation collar, and the H₂EM‑Field combustion architecture. This version supersedes all prior GNMT preprints and is accepted for publication in Acceleron Journal.