The NASA Innovative Advanced Concepts funded a phase 1 study by Geoffrey Landis for power interstellar fly-by probes. Launching ultra-miniature probes to fly past an exoplanet a nearby star using a laser-pushed sail is now being seriously discussed as a mission, primarily by the “Breakthrough Starshot” program. Breakthrough Starshot has US$100 million to initialize research. Milner places the final mission cost at $5–10 billion, and estimates the first craft could launch by around 2036. Landis is on the Breakthrough Starshot Advisory council.
An interstellar probe will require power for both observations and communications when it reaches the target exoplanet system… but the proposed mission gives a mass allocation that is milligrams, far less than the mass of any real-world power system. Landis proposes harvesting power from the motion of the spacecraft as it passes through the target system’s ambient environment.