Talk:Plasma propulsion engine
|This article is of interest to the following WikiProjects:|
Hello. This page has been tagged for speedy deletion (made public here: User_talk:IcarusReborn) however I am just starting to revamp the article here: User:SimonHarvey/Sandbox/Plasma_propulsion_engine. Please dont delete it just yet as Consider the topic to be notable, however it will take some time (1week) to get something respectable.
Note:If you came to this point from the Ion thruster merge proposal tag discussion link, you are now on the Plasma propulsion engine discussion page, in order to centralize the comments to one place. I am suggesting that only the material in Section 4 of the ion thruster article, "Electromagnetic or Plasma Thrusters" be merged into this article, as outlined below. Wwheaton (talk) 08:03, 31 January 2009 (UTC)
[ The following are industry terms for space propulsion taxonomy: Chemical propulsion - chemical processes are used to thermally accelerate propellant Nuclear thermal propulsion - nuclear energy is used to thermally accelerate propellant Electric propulsion - electrical energy is used to accelerate propellant Solar thermal propulsion - solar energy is used to accelerate propellant
Witin electric propulsion there are further branches Electrothermal - electricity is used to produce acceleration (Resistojet, Arcjet, VASIMIR) Electrostatic - electrostatic forces accelerate propellant (Gridded ion thruster, Hall thruster) Electromagnetic - electromagnetic forces are used to accelerate propellant (Pulsed plasma, MPD)
The term plasma propulsion is very general and applies to many of the above categories. I would recommend keeping it separate from a given technology. - Added by someone that knows. ]
Plasma Propulsion engine is not the same as a thruster. The physics behind a thruster are short-term or impulse related units of thrust, while an engine defines long-term or continuous propulsion forces. However, they two are often intertwined as few understand the difference and the lack of practical application limits the number of true "engine" models available. —Preceding unsigned comment added by Newbyman (talk • contribs) 17:22, 10 May 2008 (UTC)
Two points about merging this article: 1. The article already exists under the name VASIMR - Vasimir is an incorrect spelling 2. The VASIMR is NOT the same as an ion engine. The term ion engine is imprecise. The general term is electric propulsion - almost all of which involves ionizing something and propelling it. The categories are 1 electrothermal (heating and possibly ionizing in the process and then propelling by thermal expansion) such as arcjet 2 electrostatic (ionizing by any means and then using electric charge to push the propellent) such as Xenon Ion Propulsion Engine 3 electromagnetic (ionizing by any means and then using a combination of electric charge and magnetism to push the propellent) such as VASIMR and Hall Thruster.
(Hall Thruster might also be called a hybrid between two and three, if you call 3 to be only magnetism and not electric charge.)
VASIMR is number three. "Ion engine" without clarifying is almost certainly number two but could be all three, depending on how you mean it. The only electric propulsion system that is definitely not an ion engine would be an arcjet in the case where the propellent is vaporized but not ionized.
I am changing the merge tags on both articles to point to this one place, so we can have a single discussion. I have also changed the section title to "Merge proposal", in both places. Hope this is OK with all. Wwheaton (talk) 07:41, 31 January 2009 (UTC)
- Oppose merge: I think the distinction is essentially that an ion thruster is non-thermal, using electric fields to accelerate charged particles, while plasma engines are thermal, using EM fields to control and isolate the hot working fluid. As there are many subtypes and variations, putting all into a single article seems like a mess, though there could perhaps be a skeleton with links to articles for each type. An expert with a broader knowledge could maybe write such a fat disambiguation page, but it is beyond me, certainly. And a hat full of substantive articles describing each type in some detail probably ought to come first. Wwheaton (talk) 19:13, 30 January 2009 (UTC)
- Note: I am now proposing that all engines in which the exhaust is produced by expanding a thermal plasma, be merged into this plasma propulsion article, and all engines in which the reaction mass is accelerated non-thermally by electric (or conceivably RF, as in a linac) fields be placed in the ion thruster article. Wwheaton (talk) 08:03, 31 January 2009 (UTC)
- Oppose merge: This merge proposal was too nonspecific to be useful. If an individual section is redundant, just be bold and move it and include wikilinks. Since the merge tags have been up for 8 months without commment, I am removing them. Jminthorne (talk) 06:37, 3 September 2009 (UTC)
SPT series, strange unit of thrust?
SPT-290 has 1.5H thrust. What does that mean? Since when does thrust (a force) have units of Henrys, the unit of inductance? Or is it a typo and meant to be N, Newtons. Considering the N and H keys are next to each other I'll assume the latter and amend.1812ahill (talk) 09:02, 26 October 2011 (UTC)
Basic differences between Ion thrusters and plasma thrusters
- Ion thrusters separate positive ions from electrons and accelerate only one species (the ions) through an electric field. They are electrostatic machines by nature. To keep electric neutrality and allow the beam of ions to flow into free space without coming back to a negatively charged spacecraft, electrons are simply reinjected into the accelerated ion plume at the nozzle.
- Plasma thrusters use electromagnetic fields, to heat, confine, and/or accelerate a plasma, that is a ionized gas where electrons, ions and, through collision atoms of the neutral gas, are all accelerated in one direction. They involve the Lorentz force, and more generally magnetohydrodynamics. It should be noted that a true plasma thruster uses the Lorentz force as a mean to directly accelerate the plasma to provide thrust, i.e. the vector component of the Lorentz force is in the same direction as the acceleration vector, in other words the Lorentz force component is directed axially toward the back of the spacecraft (like the magnetoplasmadynamic thruster. Many plasma thrusters actually heat and confine a plasma but don't use directly the Lorentz force to accelerate the plasma out of the thruster, they just "let it go" into space along magnetic field lines, pushed only by thermal and magnetic pressure gradients; like VASIMR, which is thus more an hybrid of an electromagnetic-electrothermal engine.
Finally, a "magnetic nozzle" confines the plasma off the wall and tunes the shape of the plasma plume to provide more thrust or more specific impulse. But it doesn't accelerate a plasma per se. The article has wrong statements about this. You should read the founding reference about electromagnetic plasma thrusters (this is the name this article should be, by he way): the book "Physics of Electric Propulsion" by R.G. Jahn, McGraw-Hill Books Co, NY, 1968. Then the more recent development reported in "Electric Propulsion", pp. 125-141 in Encyclopedia of Physical Science and Technology, R.G. Jahn, E.Y. Choueiri, Princeton University, Academic Press, Vol. 5, III Ed. 2002; and "NASA Technology Investments in Electric Propulsion: New Directions in the New Millennium", J.M. Sankovic, Glenn Research Center, NASA, 2002. Tokamac (talk) 11:05, 11 July 2014 (UTC)