The H₂EM Vacuum Plasma Cutter (H₂EM‑VPC) is the first fully operational plasma cutting and welding system designed specifically for vacuum and microgravity. No EVA‑capable plasma cutter exists today; astronauts rely entirely on mechanical tools such as saws, bolt cutters, and abrasive wheels, which severely limit emergency repair, salvage, and on‑orbit construction. As the attached document states, “crews on orbit are constrained to mechanical cutting tools… imposing severe limits on emergency repair, structural salvage, and large‑structure assembly.” The H₂EM‑VPC closes this capability gap with a governed electromagnetic plasma architecture built for deep‑space operations.

1. Architecture and Consumables

The H₂EM‑VPC uses a single consumable: water. A microwave cracking module converts water into hydrogen and oxygen on demand, eliminating stored flammable gases and cryogens. The document notes that the system “carries no stored flammable gas, no cryogens, and no pyrotechnic ignition.” Hydrogen feeds the plasma jet; oxygen is routed into a closed‑loop fuel cell that recombines it with recovered hydrogen to regenerate water and produce electrical power. This closed O₂ loop is the system’s principal innovation: “Net consumable loss per sortie is limited to the trace H₂ consumed in metal reactions and plasma entrainment.”

2. Plasma Jet and EM Governance

The plasma jet is generated and shaped entirely by electromagnetic field topology. The tool head contains no heavy power electronics; all high‑power components remain on the sled. The plasma column is governed by the Cut Governance Ratio (G_cut), which controls jet length, energy density, and stability. As the document states, “G_cut is the EM field‑topology parameter that controls jet length, energy density, and cut profile in real time.” When G_cut > 1, the field dominates the jet and produces a coherent, controllable plasma blade suitable for cutting, welding, or ablation.

Four operating modes—Standby, Pilot, Cut, and Weld/Ablate—are managed by the DIGSP supervisory controller. DIGSP enforces safety interlocks, monitors plume stability, and collapses the kernel within 50 ms during faults.

3. Closed‑Loop O₂ Recirculation

The H₂EM‑VPC is the first plasma cutter to close the hydrogen–oxygen–water loop. Oxygen separated from the cracker output is fed into a PEM fuel cell, where it recombines with recovered hydrogen to regenerate water and produce 50–150 W of electrical power. The document describes this loop as: “H₂O → H₂ + ½O₂ → plasma → recombination → H₂O.” This architecture makes the system effectively consumable‑free for a standard EVA.

4. EVA and NGLS Integration

The cutter mounts to the NGLS logistics sled, sharing its power bus, thermal loop, and DIGSP data interface. The sled houses the water tank, cracker, fuel cell, and EM driver electronics, while the operator handles only a lightweight.