We discuss the in-flight autonomous assembly as the means to build advanced planetary science payloads to explore the outer regions of the solar system. These payloads are robotically constructed from modular parts delivered by a group of smallsats (< 20 kg) which are placed on fast solar system transfer trajectories while being accelerated by solar sail propulsion to velocities of ~10 AU/yr. This concept provides the planetary science community with inexpensive, frequent access to distant regions of the solar system with flexible, reconfigurable instruments and systems that are assembled in flight. It permits faster revisit times, rapid replenishment and technology insertions, longer mission capability with lower costs. It also increases the science capabilities of smallsats via the use of modular, redundant architectures and allows for proliferation of sensing instrumentation throughout the solar system.