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UCFS Mackerel, a Loaf-class freighter, cruising above Mars with its segmented tail heat radiator glowing at the edges
UCFS Mackerel · reactor aft, crew and cargo inside the forward shadow cone

U.C.F. Engineering / Propulsion Systems

Trimodal fusion drive.

One fusion source serves three operating regimes: efficient direct-plasma cruise, propellant-augmented thrust, and high-output ship power. The arrangement is speculative. The bookkeeping is not.

System architecture

Follow the energy and mass.

Compact fusion program →

Select a mode to trace the active paths. The reactor is one part of a complete propulsion chain: confinement, conversion, propellant handling, a magnetic nozzle, shielding, and heat rejection.

UCF propulsion schematic // live mode trace
FUSION FUELD + ³He injectionREACTION MASSH₂ / D₂ variable flowSHADOW SHIELD · LiH / BORONFUSION COREFRC / mirror plasmacharged products retainedDIRECT CONVERTERcharged particles → HVDCMIXING LAYERplasma heats added massMAGNETIC NOZZLEplasma enthalpy → axial exhaustPOWER BUSmagnets · ship · payloadTAIL RADIATORsegmented tail → infrared
fusion fuelplasmareaction masselectric powerwaste heat

Operating regimes

One machine. Three assignments.

Direct plasma cruise

Spend power on exhaust velocity.

Charged fusion products expand through the magnetic nozzle with minimal added mass. Specific impulse is highest and thrust is lowest—the efficient setting for long interplanetary burns.

Thrust augmentation

Spend propellant on schedule.

Hydrogen or deuterium enters the plasma edge, raising exhaust mass flow. Thrust increases while exhaust velocity and propellant economy fall.

Power / idle

Keep the ship alive.

A direct converter feeds the high-voltage bus. Magnets, cryogenics, cargo refrigeration, avionics, and habitat loads remain supplied at minimum thrust.

Propulsion trade

More reaction mass. More thrust. Lower Isp.

Augmented mode does not add energy. It distributes available power across more exhaust mass. The chart is normalized and avoids claiming performance no flight article has demonstrated.

24%

REACTION-MASS FLOW →NORMALIZED OUTPUTTHRUSTEXHAUST VELOCITY / Isp

Loaf-class installation

The reactor defines the hull.

Fleet registry →
CREW + CARGO INSIDE SHADOW CONESHIELDSEGMENTED TAIL HEAT RADIATORMAGNETIC NOZZLE
Loaf-class side elevation · the curled segmented tail is the ship’s primary heat-rejection surface
Charged products can turn. Neutrons cannot.Magnetic fields guide ions and electrons. Neutrons require shielding, distance, replaceable blankets, and controlled access.
The tail sets sustained power.Coolant carries conversion and reactor waste heat into the articulated tail. Its exposed segments radiate infrared energy to space; tail temperature, deployed area, and clear sky view determine the duty cycle.
Magnets compete with cargo.Superconducting coils must confine plasma and form the nozzle. Their mass comes out of the freight allowance.
!

“Aneutronic” is not neutron-free.

D–³He operation still produces D–D side reactions, bremsstrahlung, activation, and waste heat. U.C.F. plans assume a neutron blanket, aft exclusion zone, remote maintenance, replaceable components, and generous tail-radiator margin. No bowl leaves the depot on optimism alone.

Engineering archive

Continue the technical brief.

Review compact fusion, brachistochrone routes, fleet geometry, and habitat systems.

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