Stellar engine

From Wikipedia, the free encyclopedia

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 which passes 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.
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 which passes 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.

Stellar engines are a class of hypothetical megastructures which use a star's radiation to create usable energy. Some variants use this energy to produce thrust, and thus 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.

There are three variant classes of this idea.

Contents

[edit] Class A (Shkadov thruster)

One of the simplest examples of stellar engine is the Shkadov thruster (named after Dr. Leonid Mikhailovich Shkadov who first proposed it), or a Class A stellar engine.[1] 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, probably by an order of magnitude — 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 is 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.[2] 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. The sun: power = 3.85*1026 W, force = 1.28*1018 N, mass = 1.99*1030 kg, acceleration = 6.45*10-13 m/s2. 1000000 (one million) years = 3.16*1013 s, velocity = 20 m/s, distance traveled = 0.06 light years. One billion years -> velocity = 20 km/s, distance = 64,000 light years.

[edit] Class B

A Class B stellar engine is a Dyson sphere — of whichever variant — built around the star, which uses the difference in temperature between the star and interstellar space to extract usable energy from the system, possibly using the phenomenon of thermoelectricity (heat engines, or thermal diodes). Unlike the Shkadov thruster, such a system is not propulsive. The Matrioshka Brain concept is based on this stellar engine concept, extracting energy for a specific purpose: data processing.

[edit] Class C

A 'Class C' stellar engine combines the two other classes, employing both the propulsive aspects of the Shkadov thruster, and the energy generating aspects of a Class B engine.

A Dyson shell with an inner surface partly covered by a mirror would be one incarnation of such a system (although it still suffers from the stabilization problems as a non-propulsive shell does), as would be a Dyson swarm with a large statite mirror (see image above). A Dyson bubble variant is already a Shkadov thruster (provided that the arrangement of statite components is asymmetrical), adding energy extraction capability to the components seems an almost trivial extension.

[edit] References

  • Stellar engine (article at the website of the Encyclopedia of Astrobiology, Astronomy and Spaceflight)
  • Solar Travel (Astronomy Today, Exploration Section)
  • Shkadov, L. M. "Possibility of controlling solar system motion in the galaxy," 38th Congress of the International Astronautical Federation", October 10-17, 1987, Brighton, UK, paper IAA-87-613.
  • Viorel Badescu and Richard B. Cathcart, "Stellar engines for Kardashev's Type II Civilization", Journal of the British Interplanetary Society 53: 297-306 (2000)
  • Viorel Badescu and Richard B. Cathcart, "Use of Class A and Class C stellar engines to control Sun movement in the galaxy", Acta Astronautica 58: 119-129 (2006).
  • Viorel Badescu and Richard B. Cathcart, "Stellar Engines and the Controlled Movement of the Sun", Chapter 12, pages 251-280 IN V. Badescu, R.B. Cathcart and R.D. Schuiling (Eds.) MACRO-ENGINEERING: A CHALLENGE FOR THE FUTURE (Springer, 2006).
  1. ^ Shkadov, L. M.
  2. ^ Actually, the radiation pressure emitted by the surface of the star remains the same. However, the thrust provided by the radiation emitted on the side of the star facing the sail/mirror/statite is counteracted by the gravitational attraction of the mass of the statite. Gravity and radiation pressure for that portion of the star's surface balance which creates an overall imbalance in the net force on the star.

    Another way to think of it: The mass of the statite mirror acts as a 'gravitational tugboat', with the star continuously pushing it ahead of the star's trajectory. The mirror would have to be 'tuned' so that the force of the radiation pressure from the star would be enough to balance the gravitational attraction of the star, and to accelerate it at the same rate as the star.