Interstellar Probe: A Practical Mission to Escape the Heliosphere

Since the beginning of space exploration, one of the most ambitious goals has been to explore beyond the boundaries of our solar system. Ground and Earth-orbit based systems have given a deep understanding of the overall characteristics of the heliosphere in the local interstellar medium and how the characteristics of our solar system are similar to and different from other systems. Viewing the heliosphere from outside will allow, for the first time, a more complete understanding of how a star system evolves and interacts with the Universe. Interstellar missions have been studied for decades. The primary reasons we have not yet explored this region are critical limitations in technology. These include a lack of propulsion that can achieve the high speeds needed to get to the heliospheric boundary in reasonable time, reliable systems that can function for the long lifetime needed, reasonable communications capabilities at interstellar range, and constraints on mission resources such as power when more than 100 AU from the Earth. Recent developments in launch systems, execution of long-lived missions such as New Horizons, new radioisotope power systems, and advanced communications systems have for the first time allowed for a practical, feasible near-term mission that can achieve the goal of exploring outside the solar system. We present recent results of a concept study that examined possible missions that could be launched as early as 2030 using existing, or near-existing, technology. These possible missions support significant payloads for heliospheric science, with the potential for additions to the payload for planetary investigations or astrophysics. The concept study includes a detailed look at possible trajectories in launch years from 2030 to 2040 with flyout speeds at least twice that of Voyager 1 and 2, and significant opportunities for tuning the flyout direction to maximize the heliophysics return as well as allow encounters with outer planets or Kuiper Belt Objects. We present a summary of trade studies performed to investigate the constraints and design space for an interstellar probe. These trades include a comparison of trajectories that include gravity assists at Jupiter and at the Sun to increase speed, optimization of the telecommunications architecture to balance data downlink rate with power usage, and spacecraft control methods to allow precise pointing for telecommnications while minimizing propellant usage for an extremely long-lived mission. We present a spacecraft design that can support the potential payloads designed to operate reliably for 50 years, while allowing for communications from 1000 AU.