Ice-Piston Fueling Interface

The ice-piston injector forms and launches solid D-T pellets for deep fueling of the breeder; its interface carries preload, extrude, and launch commands.

What it is

Deep fueling of Hyperion needs solid fuel delivered past the plasma edge, not just gas puffed at the boundary. The ice-piston mechanism freezes a D–T column, extrudes it, and chops it into pellets that a gas gun or centrifuge launches inward. The interface exposes preload, extrusion rate, cut timing, and launch velocity.

Command and sense set

• Actuate: cryostat setpoint, piston preload force, extrusion rate, pellet cut trigger, propellant valve.
• Sense: extrudate temperature, piston position/force, pellet mass (light-gate), launch velocity, arrival time.
• Cross-link: density from the interferometer chords.

# fueling demand split (breeder)
n_e   = interferometer_lineavg()
u     = density_mpc(n_e, n_ref, twin)
if u.needs_deep:
    pellet = size_from_demand(u.slow)
    ice_piston.extrude(rate=pellet.rate)
    ice_piston.launch(v=pellet.v, t=next_window)   # timed to plasma phase

Timing and ownership

Pellet launch timing is the critical parameter — deposition depth depends on injection velocity and the plasma phase at arrival — so the launch trigger is owned by L1 and synchronized to the plant clock. Piston preload and cryostat setpoints are slow and owned by L3/L4 as part of a fueling campaign.

This interface is distinct from the existing preload telemetry: here the focus is the command contract that turns a density-MPC demand into a launched pellet. Calibration ties pellet mass to light-gate signal and velocity to time-of-flight, tracked for drift. Design-and-simulation specification.