Field propulsion
Encyclopedia
Field propulsion is the concept of spacecraft propulsion
where no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields.
Examples are a gravity assist trajectory, which uses planetary gravity fields and orbital momentum, schemes that use electromagnetic field
s such as radiation pressure
such as solar sails or photonic drive, and aerodynamic fields such as solar wind
and aerobraking
.
Other concepts that have been proposed are more speculative, using "frontier physics" that may or may not become engineering practice in the future. Although speculative, ideas such as coupling to the momentum flux of the zero-point electromagnetic wave field hypothesized in stochastic electrodynamics
have a plausible basis for further investigation within the existing theoretical physics paradigm. Examples of proposals for field propulsion that rely on physics outside the present paradigms are various schemes for faster-than-light
, warp drive and antigravity, and often amount to little more than catchy descriptive phrases, with no known physical basis. Any such schemes worthy of discussion must rely on energy and momentum transfer to the spacecraft from some external source such as a local force field, which in turn must obtain it from still other momentum and/or energy sources in the cosmos in order to satisfy conservation of both energy and momentum.
One possible method gaining some credibility involves MHD magnetohydrodynamics
in which the entire vehicle acts like the armature of an electric motor and the external environment acts as the stator. Instead of the engine being a separate or distinct part of the vehicle, in this system the vehicle's power source, controls, payload and occupants are all inside the engine itself. This system seems to satisfy many of the requirements of a field propulsion system and is based on known field theory. It represents a radical departure from current ideas of aeronautics and rocket propulsion, and as such, might offer potential for a radical advance in performance capabilities.
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
where no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields.
Examples are a gravity assist trajectory, which uses planetary gravity fields and orbital momentum, schemes that use electromagnetic field
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
s such as radiation pressure
Radiation pressure
Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. If absorbed, the pressure is the power flux density divided by the speed of light...
such as solar sails or photonic drive, and aerodynamic fields such as solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
and aerobraking
Aerobraking
Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...
.
Other concepts that have been proposed are more speculative, using "frontier physics" that may or may not become engineering practice in the future. Although speculative, ideas such as coupling to the momentum flux of the zero-point electromagnetic wave field hypothesized in stochastic electrodynamics
Stochastic electrodynamics
In theoretical physics, Stochastic Electrodynamics is a variant of Classical Electrodynamics which posits the existence of a classical Lorentz Invariant radiation field having statistical properties similar to that of the electromagnetic zero-point field of Quantum Electrodynamics...
have a plausible basis for further investigation within the existing theoretical physics paradigm. Examples of proposals for field propulsion that rely on physics outside the present paradigms are various schemes for faster-than-light
Faster-than-light
Faster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....
, warp drive and antigravity, and often amount to little more than catchy descriptive phrases, with no known physical basis. Any such schemes worthy of discussion must rely on energy and momentum transfer to the spacecraft from some external source such as a local force field, which in turn must obtain it from still other momentum and/or energy sources in the cosmos in order to satisfy conservation of both energy and momentum.
One possible method gaining some credibility involves MHD magnetohydrodynamics
Magnetohydrodynamics
Magnetohydrodynamics is an academic discipline which studies the dynamics of electrically conducting fluids. Examples of such fluids include plasmas, liquid metals, and salt water or electrolytes...
in which the entire vehicle acts like the armature of an electric motor and the external environment acts as the stator. Instead of the engine being a separate or distinct part of the vehicle, in this system the vehicle's power source, controls, payload and occupants are all inside the engine itself. This system seems to satisfy many of the requirements of a field propulsion system and is based on known field theory. It represents a radical departure from current ideas of aeronautics and rocket propulsion, and as such, might offer potential for a radical advance in performance capabilities.