The H₂EM‑Field propulsion system extends the Griffiths‑Canon Architecture from governed hydrogen combustion into a space‑built, field‑governed plasma engine whose performance ceiling is set solely by electromagnetic field physics. As stated in the manuscript, it is “the fastest propulsion system in the Griffiths Canon” and is designed for deep‑space sprint missions unconstrained by atmospheric ascent, launch loads, or monolithic spacecraft architecture.

At the core is the Spine Pod Architecture, a universal mechanical and data interface running the length of the vehicle. Any module — water pod, Prometheus‑class fission reactor, or AIM pod — attaches via the same collar and DIGSP handshake. This makes propellant capacity, power ceiling, shielding depth, and inspection coverage mission‑configurable, not factory‑fixed. The vessel is assembled entirely in orbit from clip‑on modules.

Propellant is generated on demand through microwave cracking of water, eliminating cryogenic hydrogen storage. Each of the four engine cores has its own independent cracking module, ensuring fault isolation and eliminating cascading failures. Plasma initiation is stabilised by a plasma‑locked kernel at the throat, enabling reliable ignition even at high burst mass flow.

The propulsion stack operates in two regimes:

Cruise mode: Isp ≈ 10,000 s, exhaust velocity ≈ 98 km/s

REBCO burst mode: Isp ≈ 500,000–1,000,000+ s, exhaust velocity ≈ 5,000–10,000 km/s

Burst performance is enabled by REBCO high‑field micro‑coil inserts generating 30–40 T in millimetre‑scale bores, producing B_HF/B₀ ratios of 200–800×. As the text notes, “exhaust velocity scales linearly with local field intensity,” allowing peak mission velocities of 1–3% c and outer‑planet return missions measured in days.

The multi‑scale magnetic architecture combines bulk confinement coils (0.1–0.3 T) with REBCO inserts to create steep field gradients, hard suppression walls, and high Lorentz acceleration. The REMN nozzle adds active shear‑stiffening via azimuthal rotation (5–15 km/s), achieving Ω_s/γ_KH ratios of 3.5–15× in bulk and 200–800× at the REBCO boundary. This suppresses Kelvin–Helmholtz instabilities and reduces plume half‑angle to 8–15°, raising nozzle efficiency to 0.84–0.90.

The DIGSP supervisory controller governs all propulsion, power, and pod‑level operations. It manages reactor handshake, REBCO cryo health, capacitor sequencing, thrust vectoring via insert modulation, and continuous CG alignment. DIGSP also commands AIM pods, which execute all physical clip‑on operations, reposition water pods for CG control, inspect spine integrity, and isolate or jettison faulting pods.

Water pods provide propellant, radiation shielding, and dynamic ballast. Reactor pods scale power from 400 kW cruise to 800 kW burst, drawing on Prometheus‑class heritage only for validated mass, shielding, and power‑density benchmarks — not for reactor design.

The architecture is fully falsifiable through staged validation: thrust‑stand measurements, field‑mapping, plasma diagnostics, nozzle stability tests, and REBCO‑insert characterization.