Optimization of In-Space Supply Chain Design Using High-Thrust and Low-Thrust Propulsion Technologies

In-space propellant supply chain can be effectively established for manned missions if high-thrust crew vehicles and cargo tugs can be used in conjunction with low-thrust cargo tugs. Optimizing the campaign logistics network by considering all involved missions together, rather than focusing on mission-level planning alone, can provide an efficient method to support top-level architectural decisions. In this work, a framework is presented to help mission designers quickly obtain the Pareto front of initial mass in low Earth orbit versus campaign length by optimizing propellant supply locations for crew missions concurrently with propulsion technology options (e.g., high-thrust or low-thrust) for corresponding cargo deliveries. This methodology is demonstrated for a return-to-the-moon campaign that uses the cislunar space as a staging area. Discrete propulsion system sizes are used for cargo delivery vehicles, and reuse of these tugs is permitted in the model. Both high-thrust and low-thrust trajectory options are considered for each cargo mission. Although the costs for high-thrust trajectories are part of the inputs to the formulation, the costs for low-thrust trajectories are calculated internally because of their dependency on the thrust-to-payload-mass ratio. For an efficient evaluation of low-energy, low-thrust transfers in the Earth–moon system, an approximation method is implemented based on a feedback control law, Q-law, and invariant manifolds. With the developed methods, optimal predeployment strategies are calculated for a campaign of one, two, or three human lunar missions, thus quantifying the game-changing impact of low-thrust propulsion for logistics supply planning in the selected demonstration cases.