DFD thrust cycling capability for Thrust–Coast–Thrust missions

Determine whether the Direct Fusion Drive (DFD), a D–3He thermonuclear fusion propulsion system based on the Princeton Field-Reversed Configuration, can be switched off for approximately one year during an interplanetary coasting phase and subsequently restarted to provide thrust, as required by a Thrust–Coast–Thrust Earth-to-Sedna mission profile.

Background

The proposed Sedna mission profile using the Direct Fusion Drive (DFD) employs a Thrust–Coast–Thrust (TCT) trajectory, with two long thrusting periods separated by an extended coasting phase. This architecture assumes the engine can be turned off for thrust generation during coasting and later restarted.

The authors note that this assumption requires the DFD to remain inactive for approximately one year before restarting to deliver thrust. They explicitly state that, although theoretically feasible, this operational capability has not yet been confirmed, making it a critical open issue for the mission’s feasibility.