Жұлдыз қозғалтқыштары: Гипотетикалық мегақұрылымдар класы

Class of hypothetical megastructures

Stellar engines are a class of hypothetical megastructures which use the resources of a star to generate available work (or, in other words, to generate energy). For instance, they can use the energy of the star to produce mechanical, electrical or chemical work or they can use the impulse of the light emitted by the star to produce thrust, able to control the motion of a star system. The concept has been introduced by Bădescu and Cathcart. The variants which produce thrust may accelerate a star and anything orbiting it in a given direction. The creation of such a system would make its builders a type II civilization on the Kardashev scale.

Three classes of stellar engines have been defined. 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. Since the radiation pressure of the star would now be asymmetrical, i. e. more radiation being emitted in one direction as compared to another, the "excess" radiation pressure acts as net thrust, accelerating the star in the direction of the hovering statite. Such thrust and acceleration would be very slight, but such a system could be stable for millennia. Any planetary system attached to the star would be "dragged" along by its parent star. For a star such as the Sun, with luminosity 3.85 W and mass 1.99 kg, the total thrust produced by reflecting half of the solar output would be 1.28 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. After one billion years, the speed would be 20 km/s and the displacement 34,000 light years, a little over a third of the estimated width of the Milky Way galaxy.

A class B stellar engine consists of two concentric spheres around a star. The inner sphere (which may be assimilated with a Dyson shell) receives energy from the star and becomes hotter than the outer sphere. The difference of temperature between the two spheres drives thermal engines able to provide mechanical work. Unlike the Shkadov thruster, a class B stellar engine is not propulsive.

A class C stellar engine, such as the Badescu–Cathcart engine, His proposal was commissioned by the German educational YouTube channel Kurzgesagt.

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. Essentially, it replaces the giant parabolic mirror of the Shkadov thruster with an engine powered by mass lifted from the star, similar to the Caplan engine. However, instead of pushing a star from behind with a beam of thrust, as the Caplan engine does, it pulls the star from the front via its gravitational link to it, same as the Shkadov thruster. As a result, it only needs to produce a single beam of thrust (toward but narrowly missing the star), whereas the Caplan engine must produce two beams of thrust (one to push the star from behind and negate the force of gravity between the engine and the star, and one to propel the system as a whole forward). The result is that the Svoronos Star Tug is a much more efficient engine capable of significantly higher accelerations and max velocities. The Svoronos Star Tug can, in principle (assuming perfect efficiency), accelerate the Sun to ~27% the speed of light (after burning enough of the Sun's mass to transition it to a brown dwarf).