Tell me if this isn't a good idea: designing ion engines for space. The European Space Agency (ESA) is integrating ion engines into at least one of their spacecraft. While ion engines have miniscule thrust power, they can operate on solar power for years, unlike conventional fuel boosters, which are powerful but burn up quickly. Theoretically, a spacecraft running on an ion engine would start out slowly but accelerate indefinitely, reaching the edge of our solar system yet still increasing in speed.

The ESA, for now at least, seems to be interested in using ion engines for another purpose, which is to keep their Goce spacecraft in low-earth orbit. In this case the ion boosters would function as a "cruise control," in the words of one ion propulsion developer.

Go here to read the labels for the image. 

Image courtesy ESA