Stellar engine

Stellar engines are a class of hypothetical megastructures which use the resources of a star to generate available work (also called exergy).

[5] Such an engine is a stellar propulsion system, consisting of an enormous mirror/light sail—actually a massive type of solar statite large enough to classify as a megastructure—which would balance gravitational attraction towards and radiation pressure away from the star.

For a star such as the Sun, with luminosity 3.85×1026 W and mass 1.99×1030 kg, the total thrust produced by reflecting half of the solar output would be 1.28×1018 N. After a period of one million years this would yield an imparted speed of 20 m/s, with a displacement from the original position of 0.03 light-years.

Notice that such system suffers from the same stabilization problems as a non-propulsive shell, as would be a Dyson swarm with a large statite mirror (see image above).

Astronomer Matthew E. Caplan of Illinois State University has proposed a type of stellar engine that uses concentrated stellar energy (repurposing the mirror statites from class A) to excite certain regions of the outer surface of the star and create beams of solar wind for collection by a multi-Bussard ramjet assembly.

[8] Alexander A. Svoronos of Yale University proposed the 'Star Tug', a concept that combines aspects of the Shkadov thruster and Caplan engine to produce an even more powerful and efficient mechanism for controlling a star's movement.

The result is that the Svoronos Star Tug is a much more efficient engine capable of significantly higher accelerations and max velocities.

Diagram of a class-C stellar engine (to scale) built around a Sun-like star. It consists of a partial Dyson swarm composed of 5 Dyson rings of solar collectors (the class-B component), and a large statite Shkadov thruster (the class-A component). Perspective is from below the system's ecliptic at a distance of ~2.8 AU . The system's direction of acceleration is on a vector from the center of the star through the center of the Shkadov thruster, which is hovering over the star's north pole (with regards to the ecliptic), at a distance of 1 AU.