Gravitational Valleys: L4 and L5 Lagrange Points as Permanent Staging Nodes for Interplanetary and Interstellar Transport Networks

The expansion of human infrastructure into deep space is fundamentally limited by the rocket equation and propellant mass fractions. This paper proposes the utilization of the Sun-Earth and Earth-Moon L4 and L5 Lagrange points not merely as observational outposts, but as permanent, zero-propellant staging nodes. By leveraging the natural stability of these points within the Circular Restricted Three-Body Problem (CR3BP), we outline a framework for establishing deep-space manufacturing hubs and gateways to the broader Interplanetary Transport Network (ITN).