Field propulsion
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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, such as gravitational and magnetic fields from stars and planets. Proposed drives that use field propulsion are often called a reactionless or propellantless drive.
Types
Practical methods
Although not presently in wide use for space, there exist proven terrestrial examples of "Field Propulsion", in which electromagnetic fields act upon a conducting medium such as seawater or plasma for propulsion, is known as magnetohydrodynamics or MHD. MHD is similar in operation to electric motors, however rather than using moving parts or metal conductors, fluid or plasma conductors are employed. The EMS-1 and more recently the Yamato 1[1] are examples of such electromagnetic Field propulsion systems, first described in 1994.[2] There is definitely potential to apply MHD to the space environment such as in experiments like NASA's electrodynamic tether, Lorentz Actuated Orbits,[3] the wingless electromagnetic air vehicle, and magnetoplasmadynamic thruster (which does use propellant).
Other practical methods which could be loosely considered as field propulsion include: The
Speculative methods
Other concepts that have been proposed are speculative, using "frontier physics" and concepts from modern physics. So far none of these methods have been unambiguously demonstrated, much less proven practical.
The
In contrast, examples of proposals for field propulsion that rely on physics outside the present paradigms are various schemes for
Several people have speculated that the Casimir effect could be used to create a propellantless drive, often described as the "Casimir Sail", or a "Quantum Sail".[5][6][7][8]
Field propulsion based on physical structure of space
This concept is based on the general relativity theory and the
In the general relativistic field propulsion system space is considered to be an elastic field similar to rubber which means that space itself can be treated as an infinite elastic body. If the
For the quantum field theoretical propulsion system it is assumed, as stated by the quantum field theory and
Conservation Laws
Conservation of momentum is a fundamental requirement of propulsion systems because in experiments momentum is always conserved.[11] This conservation law is implicit in the published work of Newton and Galileo, but arises on a fundamental level from the spatial translation symmetry of the laws of physics, as given by Noether's theorem. In each of the propulsion technologies, some form of energy exchange is required with momentum directed backward at the speed of light 'c' or some lesser velocity 'v' to balance the forward change of momentum. In absence of interaction with an external field, the power 'P' that is required to create a thrust force 'F' is given by when mass is ejected or if mass-free energy is ejected.
For a photon rocket the efficiency is too small to be competitive.[12] Other technologies may have better efficiency if the ejection velocity is less than speed of light, or a local field can interact with another large scale field of the same type residing in space, which is the intent of field effect propulsion.
Advantages
The main advantage of a field propulsion systems is that no propellant is needed, only an energy source. This means that no propellant has to be stored and transported with the space craft which makes it attractive for long term interplanetary or even interstellar crewed missions.[10] With current technology a large amount of fuel meant for the way back has to be brought to the destination which increases the payload of the overall space craft significantly. The increased payload of fuel, thus requires more force to accelerate it, requiring even more fuel which is the primary drawback of current rocket technology. Approximately 83% of a Hydrogen-Oxygen powered rocket, which can achieve orbit, is fuel.[13]
Limits
The idea that with field propulsion no fuel tank would be required is technically inaccurate. The energy required to reach the high speeds involved begins to be non-neglectable for interstellar travel. For example, a 1-tonne spaceship traveling at 1/10 of the speed of light carries a kinetic energy of 4.5 × 1017 joules, equal to 5 kg according to the mass–energy equivalence. This means that for accelerating to such speed, no matter how this is achieved, the spaceship must have converted at least 5 kg of mass/energy into momentum, imagining 100% efficiency. Although such mass has not been "expelled" it has still been "disposed".
See also
References
- ^ AKAGI, Shinsuke; FUJITA, Kikuo; SOGA, Kazuo (May 27, 1994). "Optimal Design of Thruster System for Superconducting Electromagnetic Propulsion Ship" (PDF). Proceedings of the 5th International Marine Design Conference. Retrieved November 30, 2022.
- ^ US 5333444, Meng, James C. S., "Superconducting electromagnetic thruster", published 1994-08-02, assigned to United States Secretary of the Navy
- ^ Peck, Mason A. "Lorentz-Actuated Orbits: Electrodynamic Propulsion without a Tether" (PDF). Retrieved November 30, 2022.
- ISSN 0022-4650.
- ^ "Running on empty". New Scientist. Retrieved 2023-08-06.
- OSTI 21370934.
- .
- ISBN 978-0-14-029647-1.
- ISBN 978-1-60805-566-1.
- ^ .
- ISBN 978-981-238-303-7. Extract of page 19
- ^ There will be no photon rocket, by V. Smilga http://www.dtic.mil/dtic/tr/fulltext/u2/611872.pdf Archived 2017-05-17 at the Wayback Machine
- ^ Pettit, Don. "The Tyranny of the Rocket Equation". NASA. Archived from the original on 2016-10-29. Retrieved 2016-11-04.
External links
- Examples of current field propulsion systems for ships.
- Example of a possible field propulsion system based on existing physics and links to papers on the topic. broken link
- Stoyan Sarg (2009). Field Propulsion by Control of Gravity: Theory and Experiments. CreateSpace Independent Publishing Platform. ISBN 978-1-4486-9308-5.
- Y. Minami., An Introduction to Concepts of Field Propulsion, JBIS,56,350-359(2003).
- Minami Y., Musha T., Field Propulsion Systems for Space Travel, the Seventh IAA Symposium on Realistic Near-Term Advanced Scientific Space Missions, 11–13 July 2011, Aosta, Italy
- Ed.T.Musha, Y.Minami, Field Propulsion System for Space Travel: Physics of Non-Conventional Propulsion Methods for Interstellar Travel, 2011 ISBN 978-1-60805-270-7.
- Field Resonance Propulsion Concept - NASA
- ASPS
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