Getting a probe to 200 AU from the Sun ‘as fast as possible’ is what Innovative Interstellar Explorer is all about. The mission represents a current look at an idea that has been kicking around the space community for about thirty years now — an interstellar precursor mission that would get us into the interstellar medium with an instrument package specifically designed for its study. The goals are laid out in a recent article in The Journal of Spacecraft and Rockets which has been made available online.

The mission offers rich possibilities. At the top of the agenda is to explore the interstellar medium and study the properties of interstellar gas, the interstellar magnetic field, low-energy cosmic rays and interstellar dust. But the complex interactions between the Solar System and the space through which it travels are a major area for research as well. And learning more about the region immediately beyond the heliosphere can tell us much about the origin of the Solar System and give us clues about how other planetary systems form.

It has been fascinating to watch this idea evolve over time. Various trajectories studied for the mission, each described in this paper, included a close pass by the Sun for a gravity assist, using chemical or other thrust systems including nuclear electric propulsion and solar sails. Today’s thinking is to forego the close Solar pass for thermal reasons, and to fly Innovative Interstellar Explorer with a high energy launch followed by a long thrusting period using electric propulsion powered by radioisotope power systems. The mission would pick up a gravity assist at Jupiter, although single and double gravity assists from the outer planets have at one time or another been considered.