Innovative Interstellar Explorer was a NASA "Vision Mission" study funded by NASA following a proposal under NRA-03-OSS-01 on 11 September 2003. This study focused on the elusive quest to reach and measure the interstellar medium, the region outside the influence of the nearest star, the Sun. It proposes to use a radioisotope thermal generator with ion thrusters. The project is a study of a proposed interstellar precursor mission that would probe the nearby interstellar medium and measure the properties of magnetic fields and cosmic rays and their effects on a craft leaving the Solar System. Mission launch plans analyzed direct, one planet, multi-planet, and upper-stage trades.
A variety of plans were proposed, including using launch windows (not counting backups) for a Jupiter assist in 2014, 2026, 2038, and 2050—about every 12 years. The launch opportunity for the 2014 window passed, but for example it could have resulted in a Jupiter flyby by early 2016 and then go on to reach 200 AU by 2044. With an ion drive, a speed of about 7.9 AU/yr by the time its xenon propellant was depleted could be attained, enabling that 200 AU by 2044 and perhaps 1000 AU after one hundred years from launch. Different launch times and configurations have various timelines and options.