Stellar engine

Last updated
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. Class C Stellar Engine.JPG
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.

Stellar engines are a class of hypothetical megastructures which use the resources of a star to generate available work (also called exergy). 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. [1] The concept has been introduced by Bădescu and Cathcart. [2] The variants which produce thrust may accelerate a star and anything orbiting it in a given direction. [3] [4] The creation of such a system would make its builders a type-II civilization on the Kardashev scale.

Contents

Classes

Three classes of stellar engines have been defined. [2]

Class A (Shkadov thruster)

One of the simplest examples of a stellar engine is the Shkadov thruster (named after Dr.  Leonid Shkadov, who first proposed it), or a class-A stellar engine. [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. 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 3.85×1026  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. 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.

Class B

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.

Class C

A class-C stellar engine, such as the Badescu–Cathcart engine, [2] 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 higher temperature Dyson shell partially covered by a mirror combined with an outer sphere at a lower temperature would be one incarnation of such a system. The non-spherical mirror ensures conversion of light impulse into effective thrust (like a class-A stellar engine) while the difference of temperature may be used to convert star energy into mechanical work (like a class-B stellar engine). 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). 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.

Caplan thruster

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. The ramjets would produce directed plasma to stabilize its orbit and jets of oxygen-14 to push the star. Using rudimentary calculations that assume maximum efficiency, Caplan estimates that the Bussard engine would use 1012 kg of solar material per second to produce a maximum acceleration of 10−9 m/s2, yielding a velocity of 200 km/s after 5 million years and a distance of 10  parsecs over 1 million years. While theoretically the Bussard engine would work for 100 million years, given the mass loss rate of the Sun, Caplan deems 10 million years to be sufficient for a stellar collision avoidance. [6] His proposal was commissioned by the German educational YouTube channel Kurzgesagt. [7]

Svoronos Star Tug

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). [8]

See also

Related Research Articles

<span class="mw-page-title-main">Dyson sphere</span> Hypothetical megastructure around a star

A Dyson sphere is a hypothetical megastructure that encompasses a star and captures a large percentage of its solar power output. The concept is a thought experiment that attempts to imagine how a spacefaring civilization would meet its energy requirements once those requirements exceed what can be generated from the home planet's resources alone. Because only a tiny fraction of a star's energy emissions reaches the surface of any orbiting planet, building structures encircling a star would enable a civilization to harvest far more energy.

<span class="mw-page-title-main">Interstellar travel</span> Hypothetical travel between stars or planetary systems

Interstellar travel is the hypothetical travel of spacecraft between star systems. Due to the vast distances between the Solar System and nearby stars, interstellar travel is not possible with current propulsion technologies.

<span class="mw-page-title-main">Spacecraft propulsion</span> Method used to accelerate spacecraft

Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric entry.

<span class="mw-page-title-main">Ion thruster</span> Spacecraft engine that generates thrust by generating a jet of ions

An ion thruster, ion drive, or ion engine is a form of electric propulsion used for spacecraft propulsion. An ion thruster creates a cloud of positive ions from a neutral gas by ionizing it to extract some electrons from its atoms. The ions are then accelerated using electricity to create thrust. Ion thrusters are categorized as either electrostatic or electromagnetic.

<span class="mw-page-title-main">Bussard ramjet</span> Proposed spacecraft propulsion method

The Bussard ramjet is a theoretical method of spacecraft propulsion for interstellar travel. A fast moving spacecraft scoops up hydrogen from the interstellar medium using an enormous funnel-shaped magnetic field ; the hydrogen is compressed until thermonuclear fusion occurs, which provides thrust to counter the drag created by the funnel and energy to power the magnetic field. The Bussard ramjet can thus be seen as a ramjet variant of a fusion rocket.

Thruster may refer to:

<span class="mw-page-title-main">Kardashev scale</span> Measure of a civilizations evolution

The Kardashev scale is a method of measuring a civilization's level of technological advancement based on the amount of energy it is capable of harnessing and using. The measure was proposed by Soviet astronomer Nikolai Kardashev (1932–2019) in 1964 and was named after him.

<span class="mw-page-title-main">SMART-1</span> European Space Agency satellite that orbited the Moon

SMART-1 was a Swedish-designed European Space Agency satellite that orbited the Moon. It was launched on 27 September 2003 at 23:14 UTC from the Guiana Space Centre in Kourou, French Guiana. "SMART-1" stands for Small Missions for Advanced Research in Technology-1. On 3 September 2006, SMART-1 was deliberately crashed into the Moon's surface, ending its mission.

A solar thermal rocket is a theoretical spacecraft propulsion system that would make use of solar power to directly heat reaction mass, and therefore would not require an electrical generator, like most other forms of solar-powered propulsion do. The rocket would only have to carry the means of capturing solar energy, such as concentrators and mirrors. The heated propellant would be fed through a conventional rocket nozzle to produce thrust. Its engine thrust would be directly related to the surface area of the solar collector and to the local intensity of the solar radiation.

<span class="mw-page-title-main">Laser propulsion</span> Form of beam-powered propulsion

Laser propulsion is a form of beam-powered propulsion where the energy source is a remote laser system and separate from the reaction mass. This form of propulsion differs from a conventional chemical rocket where both energy and reaction mass come from the solid or liquid propellants carried on board the vehicle.

Star lifting is any of several hypothetical processes by which a sufficiently advanced civilization could remove a substantial portion of a star's matter which can then be re-purposed, while possibly optimizing the star's energy output and lifespan at the same time. The term appears to have been coined by David Criswell.

A radioisotope rocket or radioisotope thermal rocket is a type of thermal rocket engine that uses the heat generated by the decay of radioactive elements to heat a working fluid, which is then exhausted through a rocket nozzle to produce thrust. They are similar in nature to nuclear thermal rockets such as NERVA, but are considerably simpler and often have no moving parts. Alternatively, radioisotopes may be used in a radioisotope electric rocket, in which energy from nuclear decay is used to generate the electricity used to power an electric propulsion system.

<span class="mw-page-title-main">Megastructure</span> Very large artificial object

A megastructure is a very large artificial object, although the limits of precisely how large vary considerably. Some apply the term to any especially large or tall building. Some sources define a megastructure as an enormous self-supporting artificial construct. The products of megascale engineering or astroengineering are megastructures.

Megascale engineering is a form of exploratory engineering concerned with the construction of structures on an enormous scale. Typically these structures are at least 1,000 km (620 mi) in length—in other words, at least one megameter, hence the name. Such large-scale structures are termed megastructures.

<span class="mw-page-title-main">Spacecraft electric propulsion</span> Type of space propulsion using electrostatic and electromagnetic fields for acceleration

Spacecraft electric propulsion is a type of spacecraft propulsion technique that uses electrostatic or electromagnetic fields to accelerate mass to high speed and thus generating thrust to modify the velocity of a spacecraft in orbit. The propulsion system is controlled by power electronics.

Engineering on an astronomical scale, or astronomical engineering, i.e., engineering involving operations with whole astronomical objects, is a known theme in science fiction, as well as a matter of recent scientific research and exploratory engineering.

A thermal rocket is a rocket engine that uses a propellant that is externally heated before being passed through a nozzle to produce thrust, as opposed to being internally heated by a redox (combustion) reaction as in a chemical rocket.

<span class="mw-page-title-main">Technosignature</span> Property that provides scientific evidence for the presence of technology

Technosignature or technomarker is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not. Some authors prefer to exclude radio transmissions from the definition, but such restrictive usage is not widespread. Jill Tarter has proposed that the search for extraterrestrial intelligence (SETI) be renamed "the search for technosignatures". Various types of technosignatures, such as radiation leakage from megascale astroengineering installations such as Dyson spheres, the light from an extraterrestrial ecumenopolis, or Shkadov thrusters with the power to alter the orbits of stars around the Galactic Center, may be detectable with hypertelescopes. Some examples of technosignatures are described in Paul Davies's 2010 book The Eerie Silence, although the terms "technosignature" and "technomarker" do not appear in the book.

Atmosphere-breathing electric propulsion, or air-breathing electric propulsion, shortly ABEP, is a propulsion technology for spacecraft, which could allow thrust generation in low orbits without the need of on-board propellant, by using residual gases in the atmosphere as propellant. Atmosphere-breathing electric propulsion could make a new class of long-lived, low-orbiting missions feasible.

References

  1. "Stellar_Engines.pdf". Google Docs. Retrieved 2022-06-12.
  2. 1 2 3 Badescu, Viorel; Cathcart, Richard B. (2000). "Stellar engines for Kardashev's Type II Civilization". Journal of the British Interplanetary Society . 53: 297–306. Bibcode:2000JBIS...53..297B. Archived from the original on 2018-08-24. Retrieved 2013-07-01.
  3. Badescu, Viorel; Cathcart, Richard B. (February 2006). "Use of Class A and Class C stellar engines to control Sun movement in the galaxy". Acta Astronautica. 58 (3): 119–129. Bibcode:2006AcAau..58..119B. doi:10.1016/j.actaastro.2005.09.005.
  4. Badescu, Viorel; Cathcart, Richard B. (2006). "Chapter 12: Stellar Engines and the Controlled Movement of the Sun". Macro-Engineering: A Challenge for the Future. Water Science and Technology Library. Vol. 54. pp. 251–280. doi:10.1007/1-4020-4604-9_12. ISBN   978-1-4020-3739-9.
  5. Shkadov, Leonid (10–17 October 1987). "Possibility of controlling solar system motion in the Galaxy". Proceedings of the IAF 38th International Astronautical Congress. 38th International Astronautical Congress IAC 1987. Brighton, England: International Astronautical Federation. pp. 1–8. Bibcode:1987brig.iafcR....S.
  6. Caplan, Matthew (December 17, 2019). "Stellar engines: Design considerations for maximizing acceleration". Acta Astronautica. 165: 96–104. Bibcode:2019AcAau.165...96C. doi:10.1016/j.actaastro.2019.08.027. S2CID   203111659. Archived from the original on December 23, 2019. Retrieved December 22, 2019.
  7. "How to Move the Sun: Stellar Engines". YouTube. Kurzgesagt. December 22, 2019. Archived from the original on 2021-12-21. Retrieved April 26, 2021.
  8. Svoronos, Alexander A. (2020-11-01). "The Star Tug: An active stellar engine capable of accelerating a star to relativistic velocities". Acta Astronautica. 176: 306–312. Bibcode:2020AcAau.176..306S. doi:10.1016/j.actaastro.2020.07.005. ISSN   0094-5765. S2CID   224962621.