Open Questions & Roadmap
Direct conversion rests on established physics, but the integrated high-field D-3He train still has real questions the test program must answer.
What is settled and what is not
The individual converters — electrostatic, traveling-wave, MHD, thermionic — each have an experimental pedigree. What is not yet demonstrated is the assembled multi-modal train, at ultra-high field, fed by a real D-3He plasma, delivering a measured recovery fraction. Being honest about that boundary is essential: the burner is a design-and-simulation study, and these are the questions it exists to answer.
The open questions
- Integrated recovery fraction: how much of the charged-particle energy the full train actually delivers to the bus.
- Beam quality from the expander: whether the exhaust is as directional and well-sorted as models predict.
- Bunching against space charge: how tightly TWDEC can hold bunches at burner power density.
- MHD at ultra-high field: electrode life and Hall behavior in a fusion-exhaust channel at 17–26 T.
- Materials lifetime: erosion, secondary emission, and radiation tolerance over real operating hours.
- Neutron handling: confirming the ~5.44% thermal share and its shielding in practice.
The roadmap
The path runs from today's design-and-simulation work, through component-level testing of the individual converters and materials, to the integrated burner test unit targeted around 2032. Only after the test unit measures the recovery fraction and demonstrates the handoffs does a commercial, load-sited MetroVolt follow. Each step is gated on the previous one delivering evidence, not on optimism.
Why this honesty is the point
Direct energy conversion is the reason MetroVolt can promise firm, near-zero-water power at the load — but the promise is a design case, not an operating result. Stating the open questions plainly, and tying them to a dated test program, is how the burner program keeps its claims proportionate to its evidence. This section describes a machine being designed, not one already running.