Cost and Considerations for Successful Implementation of Long Duration Space Missions

Robotic space flight has allowed us to explore our sun, and the planets and moons of our solar system, well beyond the current limitations of human space flight. The Johns Hopkins Applied Physics Laboratory (JHU/APL) has sent spacecraft to destinations such as Mercury (MESSENGER), Pluto (New Horizons), and to the Sun (Parker Solar Probe). Under the New Horizons mission (launched in 2006), JHU/APL became the first organization to develop a mission specifically designed to study Pluto and the Kuiper Belt. The journey to the furthest reaches of our solar system required an extended mission operations phase, and with that came additional considerations to ensure mission success. Using lessons learned from New Horizons and the utilization of new technology, JHU/APL undertook the Interstellar Probe (ISP) mission concept study (report released December 2021). Technologies utilizing nuclear power have allowed spacecraft to be powered for much longer durations without substantial increase in mass. The use of nuclear power sources in the form of radioisotope power systems (RPS) revolutionized the design of robotic space missions. As this technology undergoes a new cycle of refresh and development, improvements will allow us to operate missions over multiple decades, enabling longer and farther exploration. The next logical step in NASA's space exploration challenge is to focus on missions that collect science beyond our own solar system. To date, there have only been five missions that have left our solar system: Voyager 1, Voyager 2, Pioneer 10, Pioneer 11 and New Horizons. Of these five, only Voyager 1 and Voyager 2 have entered interstellar space. Voyager 1 and Voyager 2 are twin spacecraft launched in 1977 by NASA's Jet Propulsion Laboratory (JPL). They are both RPS powered and have operated for over 45 years. This feat has not been repeated again for various reasons, though cost and technical constraints that an interstellar, long duration mission brings are among them. It is not enough to assume that just because we have succeeded before with Voyager 1 and Voyager 2, that the task can be repeated successfully without careful research and planning. This research and planning was the foundation of the ISP report. However, ISP will not be the last interstellar mission concept nor the last concept requiring a long duration mission operations phase. As further study is done to refine these concepts, a framework to assist the community in handling the programmatics and costs of a long duration space mission is necessary. Since an intentional long duration space mission is still mostly a novel concept, we will start with looking at other fields of study to draw ideas from. This paper will delve into the groundwork necessary to develop such a framework, discuss initial ideas and map out the research that will be necessary to create a cost model based on the developed framework.