Story Profile: Heinlein NeLiSp Engine

The NeLiSp engine functions similarly to a jump drive but it harnesses light and cosmic radiation, converting them into their mass equivalents through electromagnetic forces that manipulate photons and radioactive ions to produce a gravitational force that accelerates a ship through space at near light speeds. This gravitational force is also used to bend and fold the fabric of space to periodically jump locations along its path of travel. Furthermore, the reality augmentor Lacey invents to open a portal in Harvest Moon: Lunar Tides is a variation of the NeLiSp system.