Talk:Reactionless drive

Woodward effect

It seems to me that this article could mention Mach's Principle and the Woodward effect. If Woodward is right, after all, then perhaps there is a way to build a reactonless drive. Personally, I suspect his device will actually prove to be a special kind of reaction drive, in which the "reactant" is gravity waves --but that's WP:OR and of course not permissible in the article here. Still, until something like that gets proved, it wouldn't hurt to include something in the article about the Woodward effect. V (talk) 20:48, 19 April 2010 (UTC)

Propellantless Propulsion

Some years ago NASA hosted a "Breakthrough Propulsion Physics" initiative that attracted a number of wild ideas. I do not know to what extent any of the ideas/papers presented at this Conference http://www.integrityresearchinstitute.org/Propulsion/JPCReport.htm could be considered to have been published. At least one of them is available on the web at the big Archive site: http://web.archive.org/web/20030608095941/www.tdimension.com/documents/AIAA+2001+Manuscript.pdf It is to be noted that if this physics is valid, then even though a device is described that uses no propellant, it is nevertheless not a reactionless drive. Per the document, it claims to generate a kind of beam of gravitational waves; it should be obvious to anyone here that if such waves can be artificially generated and do move off in one direction, carrying momentum, then the device that generates them must move in the opposite direction, per Momentum Conservation. The cool thing, and the reason I'm posting this, is that if such a device existed and you saw it flitting about, you would not be able to easily detect the "exhaust" associated with its motion --you would need a gravitational-wave-detector! It would look like a reactionless drive!!! V (talk) 18:02, 21 April 2010 (UTC)

Ultra High Vacuum Gyroscope

I think some clarification, or at least a reference, is needed here. —Preceding unsigned comment added by 162.53.36.90 (talk) 21:07, 22 July 2010 (UTC)

What about Warp Drive (albuierre and star trek), wormholes etc.

According to that paper by Alcubierre (I think that is the name), warp drive is possible under general relativity...and it does not act like a rocket. There is no momentum exchange. What say you guys to that? 68.186.48.171 (talk) 04:50, 17 August 2010 (UTC)

Nobody has any idea how to build one, and if you did build one, it's possible to build a time machine using it, so it's theoretically extremely dubious.- Wolfkeeper 05:55, 17 August 2010 (UTC)

Reaction with medium

if a drive mechanism has a reaction with a medium then it is not reactionless. therefore any drive system that interacts with spacetime (which is psyical according to Realativity) or some aspect of physical reality that is ubiquitous to the universe (like the quantum vacuum) then it is reacting with a medium and cant be counted here. couple of small notes: spacetime swimming may be feasable, but i would hesitate to jump on that because of how big you would need to make yourself to make use of a spherical universal spactime. also: there is simply no known mechanism in physics of converting rotational momentum to linear momentum without the loss of mass and thus a change in momentum. i know this from practical experiance; mechanicaly it doesnt fit with what has been both observed by scientists, mathematicians and engineers. it has been observed consistantly that momentum cannot be changed without something being moved in accordance with the third law.In the case of the aformentioned discus, the discus player is 'thrown' backwards, but his friction with the ground prevents his movement. the discus remains in the air not because its rotation is causing it to move but because of the aerodynamic properties of the discus (again, a reaction with the medium, but not producing thrust this time). if the discus thrower were in space he would be accelerated away from the discus as it left his hand. the discus would be spinning, but it wouldnt be accelerating, and though it wouldnt stop that would be due to lack of friction (more medium interactions) not conversion of momentum from rotation.

i close off here as this is becoming a treatise, but simply put this engine concept appears to be illogical, given what has been established already in physics.

Beam-powered propulsion

The article should probably explain that these also are not reactionless drives in a similar way to the tethers. anyone else agree? IRWolfie- (talk) 15:29, 16 June 2011 (UTC)

Gyroscopic Inertial Thrusters

Interesting discussion. The greatest hindrance to discovery and invention is MENTAL INERTIA, and the treatment of science as though it is a dogmatic religion.

Can anyone cite an authority that made the ridiculous statement that angular accelerations and momentum can NOT be exchanged for linear accelerations and momentum?

Yes, read the works of Emmy Noether - the genius-level mathematician much admired by Einstein. She proved that the conservation-laws of physics are directly linked to basic symmetries of time and space. One of the results is that linear and angular momenta are separately conserved, and therefore cannot be inter-converted. The only problem is that those of low intellect are unable to understand the proofs and thus continue to waste their lives on trying to achieve the impossible. They should learn to take instruction from their betters. — Preceding unsigned comment added by 82.2.156.175 (talk) 15:39, 22 December 2018 (UTC)

Such claims were made by Edison, attempting to discredit Tesla's alternating current. Mass and momentum equations are remarkably similar to the math involving electronics.

Over 20 others repeated my experiments, converting angular accelerations into linear acceleration, passing pendulum, water, ice skid, and air table tests.

Conservation of energy is NOT violated, since energy is required to change the velocity or direction of the device. While only small "anomalous" amounts of thrust have been generated, the venemous nature of religion in the name of science has been VERY difficult to overcome.

"Do NOT confuse me with facts and experiments that appear to violate a BASIC TENNANT of physics, it is IMPOSSIBLE, therefore I will disbelieve my lying eyes!" - is the too common reaction when any attempt is made to further this field of research. This is inconvenient, and NOT helpful, especially when fanatics insist on erasing any facts that do not conform to their religious views of science.

David E. Cowlishaw

Please don't delete this. CowlishawDavid (talk) 21:11, 17 June 2011 (UTC)

Reverted to original article minus forum style commentary CowlishawDavid (talk) 00:05, 21 June 2011 (UTC)

Deleted unmerited links, per WP:ELNO. AndyTheGrump (talk) 03:15, 21 June 2011 (UTC)

Yo, Cowlishaw, stop adding these unsourced or poorly cited personal conclusions of yours to the article. Per WP:NOR, Wikipedia is not the place to publish your opinions, theories or findings. The self-promotional soapboxing you added here just makes it that much worse. Binksternet (talk) 05:49, 24 June 2011 (UTC)

Here is a version of the gyroscope text that might be suitable for the article.

Gyroscopic Inertial Thruster (GIT)

The Gyroscopic Inertial Thruster is a proposed reactionless engine which uses a principle can best be described as "rectified angular accelerations to produce a linear result". This proposed reactionless thruster that was discussed during the late 90's and early 2000's via public internet communications (newsgroups), which encouraged several "garage inventors" to work toward the goal of reactionless thrust. Enthusiasts attempted building and testing a wide range of machines, based on the principle, of "rectified angular accelerations".

I actually like this definition, it's more succinct in it's description, and NOT a derivation of Eric Laithwaite's work (torque against torque on an obtuse angle). Any attempt to bring my actual work into this discussion is soon shot down by Zealots that claim expertice, without doing the math, or the experiments. WHAT? DO I HAVE TO DIE FIRST, to be recognized for my work?

davide.cowlishaw (facebook profile name, where I CAN share without adverse reactions!

The links to the experiments and actual work are there, and not here (by some design, that I can't fathom in hiding reality, in favor of flat-earth fantasies). David Eugene Cowlishaw 10:07 pm, Thursday, 28 July 2011 — Preceding unsigned comment added by 216.134.173.13 (talk) 05:07, 29 July 2011 (UTC)

"DO I HAVE TO DIE FIRST, to be recognized for my work?" No. You have to get it published in reputable scientific journals. AndyTheGrump (talk) 05:14, 29 July 2011 (UTC)

Fill in the fact tags with reliable or even marginally reliable sources and we're in business. --Rocksanddirt (talk) 17:37, 24 June 2011 (UTC)

I'm not so sure that "Secrets of Antigravity Propulsion: Tesla, UFOs, and Classified Aerospace Technology" (currently reference number 13) is a reliable reference. For more about its author, and his many earth-shattering discoveries, see here. Cardamon (talk) 17:28, 1 July 2011 (UTC)

I added a brief description of the supposed operating principle of the GIT, which is hard to figure out from the other references supplied. ~~Duncan — Preceding unsigned comment added by 99.103.1.165 (talk) 21:30, 19 October 2012 (UTC)

Quantum Vacuum Plasma Thruster

Should this be added? JCDenton2052 (talk) 03:43, 9 December 2012 (UTC)

"Swimming" in Spacetime

In light of Dr. Jack Wisdom's 2003 paper "Swimming in Spacetime: Motion by Cyclic Changes in Body Shape" [ http://web.mit.edu/wisdom/www/swimming.pdf ], it appears that much of this WP will have to be re-written in a more favorable light. Wisdom's startling discovery describes a means to produce changes in position by exploiting the spacetime curvature aka gravitational field, without propellent or reaction forces, and without violating conversation of momentum or energy, using a sequence of deformations that displace the center of mass of the body in any given direction within the field. There is no violation of energy or momentum because the motion of the body ceases when the deformations cease. The magnitude of the effect he describes depends upon the magnitude of the spacetime curvature in the region of the body, and the magnitude of the deformations, so in the vicinity of the Earth the motion per cycle is very small, on the order of 10e-23m per cycle where the deformations are on the scale of 1 meter. But the motion is cumulative and substantially larger in regions of high spacetime curvature. So although this effect may be of purely academic interest at present, the former objection that reactionless propulsion is "impossible" and that such concepts must necessarily violate momentum and energy conditions, is now obsolete to the canon of mainstream wisdom. Informedskeptic (talk) 10:18, 20 November 2014 (UTC)

I can find no evidence that Wisdom's paper has been cited in any mainstream scientific journal. What evidence do you have that this paper has any significance? AndyTheGrump (talk) 18:06, 22 November 2014 (UTC)

I’m not sure how you define “significance” in this context, so I’ll make my case for “validity,” “relevance,” and “scientific interest” instead. Following Jack Wisdom’s original 2002 paper and 2003 research article published in Science magazine, his concept was explored by Guéron, Avron and Kenneth, and generalized by Harte in 2007. Harte appears to have been inspired by this subject and published a number of interesting papers on the physics of extended bodies in curved spacetime. In 2009, Guéron published an illustrative article in Scientific American, which has garnered greater public awareness and interest regarding this novel motive principle.

And although “swimming in spacetime” offers a negligible effect in the near-Earth gravitational field, it’s the only unambiguous example of a “reactionless drive” concept that I’ve ever encountered. Informedskeptic (talk) 02:25, 23 November 2014 (UTC)

Case well made. However I'm not convinced that this is actually reactionless - it must be reacting on whatever (usually) mass produced the curvature in spacetime in the first time. Lets say you have a small black hole, and a "gravitational swimmer" next to it (presumably in orbit, but lets ignore that), changing position as described in the article. The combined center of gravity of the two objects (black hole and swimmer), (as well as linear and angular momentum) would presumably not be affected by the swimming motions, and as such any movement of the swimmer would be counteracted by a movement of the black hole. I.e. the drive is not truly reactionless - which is why it obeys all the conservation laws.

Maybe this is actually more a problem with our definition - because I'm pretty sure that anyone coming here looking for a reactionless drive, would find that a drive which surfs by reacting against the gravity gradients of an astronomical object, fulfills their expectation of a reactionless drive. Without really studying the papers, it seems this process would allow a swimmer in orbit, to (slowly) crawl up a gravity well, purely by working against the gravity curvature of said well. That certainly exhibits all the traits of an antigravity- or reaction-less drive, even though it actually is not.

So it seems to me, that the lead of the article is correct in stating that (in other words) "reactionless creation of thrust (or impulse or velocity) will be a violation of Newtons laws, and as such is not considered possible", but still there are valid concepts for drives which creates thrust or motion, purely by working against a gravityfield (while conserving energy and impulse), which would seem reactionless to the casual observer.

Incidentally, gravitational assist falls in the same category - and is indeed a beast very closely related to spacetime swimming, although instead of thriving on changing the swimmers shape, it thrives on the gravity-field (of the star-planet system) changing shape in a predictable fashion as the planet revolves around the star (gravity assist only appears as the probe changes reference frame from the planet to the star), and picking a trajectory which intersects with these changes and gain momentum from them (again reacting against the object creating the local curvature in spacetime). The effect is much larger than spacetime swimming, because the movement through the curved gravity-field is so much larger (on the scale of a orbit) instead of the scale of the shape-change. However it can only happen at very specific points in space and time (those intersecting the planetary gravity field), and as such limits the trajectory severely. Spacetime swimming has fewer limitations, as you create your own opportunities (and only need to interact with a single object).

The Alcubierre drive (and other "warp-drives") is very different from spacetime swimming - it is truly reactionless, and actually generates neither thrust, impulse nor velocity, but only a change in position. Whether it is possible to realize remains to be seen, but the concept doesn't break any fundamental known laws of physics, and it is truly reactionless.

PS: Other thought experiments using a negative mass ends up having a net zero mass, and thus their center of mass is undefined, and although the parts of the device moves, the center of mass does not (i.e. the simple example of placing two identical masses, one positive and one negative, near each other, in which case the positive mass would be repulsed, while the negative mass would be attracted to the other. The two masses would both accelerate away chasing each other, but the total kinetic energy of the system would stay zero, due to the negative mass gaining negative kinetic energy.)

In short, I think we need to move the space-time swimming to the "quasi-reactionless methods" section, and possibly split this section into drives reacting on gravity fields, and drives reacting on other fields or particles. And maybe we should write a reference to them in the lead of this articles as I wrote above, stating that "there are valid concepts for drives which creates thrust or motion, purely by working against a gravity-field (while conserving energy and impulse), which would seem reactionless to the casual observer" Tøpholm (talk) 21:20, 4 March 2015 (UTC)

I don't think Alcubierre drive et al. are "reactionless"

By the page definition, "...thrust is generated without any need for an outside force or net momentum exchange to produce linear motion", the hypothetical Alcubierre drive et al are not reactionless as no thrust is generated. The position of the rocket is changed, but there's no such thing as a "law of conservation of position", especially in curving spacetimes. Any objections to my moving to the quasi-reactionless section? Unfortunately I can't find an WP:RS classifying canonically what is or isn't a reactionless drive. Rolf H Nelson (talk) 20:21, 22 November 2014 (UTC)

Is there a source that calls a drive reactionless? If not, their inclusion can be removed as being OR. --JorisvS (talk) 20:30, 22 November 2014 (UTC)

In Google Scholar there are 428 cites of the Alcubierre drive, and only 7 of them use the word "reactionless". Alcubierre is already in Faster-than-light travel, so we could probably delete its mention here.

The Alcubierre concept certainly applies to the notion of reactionless propulsion. The problem was in the definition - I think most people think "change in position" and not necessarily "change in momentum" when they think of a reactionless drive. So I changed "thrust" to "motion" in the abstract. And the idea of "reactionless" is well understood, I don't think we need a source to use the word "reactionless" because there are many ways of expressing the idea. Informedskeptic (talk) 02:24, 23 November 2014 (UTC)

Personally I think thrust, not change in position. Can you find a cite? Maybe "swimming in spacetime" and the concept that there is no well-defined center of mass in general relativity should be moved to Physical theories modified by general relativity. Rolf H Nelson (talk) 03:57, 25 November 2014 (UTC)

I think we thought "thrust" because we were used to thinking of "propulsion" in the Newtonian context of action→reaction: "thrust" by definition describes equal and opposite momentum, so it's inherently inapplicable to the "reactionless drive" concept. What we're envisioning when we imagine a reactionless drive is simply a device that produces controlled changes in position; lifting, maneuvering, i.e. "the appearance of thrust." And Jack Wisdom's discovery perfectly embodies the notion of a "reactionless drive," and, it's the only universally academically accepted concept in this category to date. Which is why it merits mention in the WP:LEAD, imo. When I come to Wikipedia to look up "reactionless drive," it's exactly what I'm looking for - an actual viable physical principle that offers a method of induced motion without propellant or external forces. And honestly I think it's wrong to give the impression in the opening paragraph that the very notion of reaction propulsion is necessarily fictitious, now that we know of an (albeit miniscule) effect that has been vetted by the peer review process, that embodies the very notion of a reactionless drive. Informedskeptic (talk) 05:22, 25 November 2014 (UTC)

Lead section / Definition of "Reactionless drive" / Article structure

I see a problem with the opening line, and subsequently with the structure of the article which follows, stemming from the definition of "reactionless drive." The WP:LEAD currently starts:

"A reactionless drive (also known by many other names, including as an inertial propulsion engine, a reactionless thruster, a reactionless engine, a bootstrap drive or an inertia drive)[citation needed] is a device to generate thrust without a propellant, presumably in contradiction to the law of conservation of momentum."

This is an improper use of the word "thrust" which is by conventional physics understanding and its mathematical definition an expression of momentum difference. NASA defines thrust in this manner:

"Thrust is a mechanical force, so the propulsion system must be in physical contact with a working fluid to produce thrust. Thrust is generated most often through the reaction of accelerating a mass of gas. Since thrust is a force, it is a vector quantity having both a magnitude and a direction. The engine does work on the gas and accelerates the gas to the rear of the engine; the thrust is generated in the opposite direction from the accelerated gas."

"The thrust equation describes how the acceleration of the gas produces a force."

F = ((m * V)2 - (m * V)1) / (t2 - t1)

Thrust is the application of Newton's third law. Therefore defining "reactionless drive" in terms of "thrust" (which by definition equates to "reaction drive") is contradictory:

Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction on that system.

Simply put, a "reactionless drive" is better defined as "any hypothetical or theoretical propulsion mechanism that does not employ the thrust principle." David Darling's alternative definition of "reactionless drive" conveys this point clearly:

"Reactionless drive

A hypothetical means of propulsion that does not depend on Newton’s third law (action and reaction are always equal and opposite) and the ejection of reaction mass. Some types of reactionless drive have been proposed as a means of faster-than-light travel. In science fiction, such a system is often referred to as a ‘space-drive’ or ‘star drive.'"

Sounds good. Rolf H Nelson (talk) 05:54, 2 December 2014 (UTC)

Perhaps because of the initial contradictory definition, the article gives WP:UNDUE weight to discredited/cranky historical attempts to violate Newton's third law (the Dean drive, Gyroscopic inertial thruster - demonstrably unworkable devices), and relegates the most significant entries which are genuinely theoretically compelling reactionless drive concepts, to the bottom of the page.

As far as I can tell the term "reactionless drive" *is* used by some to specifically apply to what I would call "attempts to create an efficient rocket by violating Newton's third law", and by others for solar sails and other scientifically reasonable devices that don't use standard rocket principles but are otherwise kind of rocket-ish. The problem with the second category is that it's extremely broad, to the point where we can't much about them as a group. It's also vague and arbitrary, which makes it hard for us to categorize; an airplane propeller or a space elevator could be called a "reactionless drive" if you squint right, which is why I had to use the word "rocket-ish" above. The current article calls this second category "quasi-reactionless", which isn't even really a word. Rolf H Nelson (talk) 05:54, 2 December 2014 (UTC)

"A large number of infeasible devices, such as the "Dean drive", are a staple of science fiction, particularly for space propulsion. To date, no reactionless drive has ever been validated under properly controlled conditions."

Why are we telling users that this topic is only relevant to science fiction books, when there is serious on-going academic research on this topic? It seems that this too results from the opening definition, which essentially means "reactionless drives are attempts to produce thrust without using thrust." Instead this article should focus on concepts that don't invoke thrust, like metric engineering and applications of general relativity.

There's a minor problem with the "conclusion" of the Lead:

"To date, no reactionless drive has ever been validated under properly controlled conditions."

As much as it pains me to say this (because this particular concept strikes me as the least promising area of current research on this subject), it appears that this statement is no longer entirely technically true. Because to date, two independent experiments have confirmed the existence of a reactionless force using Shaywer's dreadful EmDrive concept. Perhaps these will both be refuted by future and better experimental tests, but in the meantime, we have to live with the data (as aggravating as it may be). But more to the point: why is the closing emphasis of the Lead section written to dissuade interest in this fascinating topic and to convey an obsolete position? Perhaps we should say something more interesting and factual, like "Efforts are currently underway to evaluate two reactionless drive concepts at NASA but results to date are inconclusive."

This raises more of a general policy question that I hope someone can clarify for me: isn't the best encyclopedia the most useful resource for researchers, students, and other interested parties? If so, shouldn't the priority and emphasis of a given article reflect the most active and legitimate areas of inquiry, which users are most likely to come here seeking references to, rather than "burying the lead" at the bottom of an article, or limiting an article's scope? There was recently a suggestion to delete mention of the Alcubierre drive from this article - which is bewildering to me. Spacetime propulsion is a primary example of a "reactionless drive" concept, and a vibrant area of on-going theoretical research (White's team at NASA is even attempting an unlikely but courageous experiment to distort spacetime towards demonstrating the validity of the Alcubierre drive concept). And the interest in the idea is enormous, even academically. So why isn't it featured far above the long-discredited Dean drive, instead of being buried at the bottom of the page facing possible deletion and a move to an obscure page?

Per WP:WEIGHT, since the dean drive has gotten a lot of media coverage, it gets more space in Wikipedia. Spacetime propulsion will need to get either a lot of academic cites, or more media attention, to be featured more prominently. Rolf H Nelson (talk) 05:54, 2 December 2014 (UTC)

Sorry for the lengthy post. Thank you for your time and your thoughtful consideration! Informedskeptic (talk) 05:38, 28 November 2014 (UTC)

Should this article exist?

Looking at how few mentions there are of "reactionless drive", and how I can't find any significant scholarly sources that discuss "reactionless drive" as a category in depth, should we just delete the article? There doesn't even seem to be consensus in the literature about what is or isn't a reactionless drive; it doesn't seem to be a rigorously-defined category. And looking at the article, it seems to just be a list of different drives with a short description of each; there's no analysis of what they have in common, nor are there any well-cited statements that apply to reactionless drives as a whole. Rolf H Nelson (talk) 06:02, 2 December 2014 (UTC)

The recent anonymous post and reversion drew my attention to this article, which I'd not reviewed in some time. Today I had the leisure time to go over your extensive list of links. I did have a question. The links which discussed relativistic pendulum effects never answered my question of how exactly does the pendulum conserve energy when swinging from one area of the curved spacetime to another since neither time nor mass can be a constant under such conditions. Is that a true assumption on my part?

Looking at the article it would appear to me properly classified under Category:pseudophysics and Category:Perpetual motion, leading to my belief that it would have importance in the history of pseudoscience. I did fine one humorous link to one of the links you posted. See The psychology of Perpetual Motion Machine Seekers. So I'd vote to not delete it. Trilobitealive (talk) 18:21, 29 January 2016 (UTC)

I didn't post the links, it's confusing that Wikipedia puts them all unlabeled on the bottom by default if there's no reflist-talk tag below. Rolf H Nelson (talk) 22:01, 30 January 2016 (UTC)

Thank you. The list of referenced is less confusing since you've changed its presentation. Trilobitealive (talk) 05:06, 31 January 2016 (UTC)

Why all the controversy over Gyroscopic Inertial thrust. I personally prefer inertial thrust, systems.

WHY DOES WIKIPEDIA KEEP CALLING THESES DEVICES REACTION LESS, THEY ARE NOT REACTION LESS. THAT'S THE POINT. 2603:800C:1F00:2DE8:55A0:3EA3:D182:7AE1 (talk) 19:29, 15 October 2023 (UTC)

Requested move 11 December 2016

Reactionless drive → propellantless drive – Please place your rationale for the proposed move here. Tokamac (talk) 18:12, 11 December 2016 (UTC)

Both previous sections of this Talk page ("Lead section / Definition of "Reactionless drive" / Article structure" and "Should this article exist?" have detected many problems with this page. Indeed this article is so wrong in its concepts… Let me explain the true heart of the problem:

1. Almost all cited examples are in fact propellantless drives. A propellantless drive can be apparently reactionless, but isn't when it is an open system, i.e. exchanging momentum with something outside of the drive. A true reactionless drive would be a closed system that would not exchange momentum with anything outside of the drive. Even the header of the current article mistakes the reactionless drive definition for the propellantless drive one: "A reactionless drive is a device to generate motion without a propellant, presumably in contradiction to the law of conservation of momentum." Somewhat true, but incomplete and as per this definition, a bird, a bee, a glider, etc… would be reactionless! Taking the reaction with air aside, even an electric train would suit this definition! But there are also many more advanced devices that do also work in outer space, relying on fields, that are clearly propellantless drives but are not reactionless at all, like in the following section of the article:

2. "Quasi-reactionless methods" section is a very poor scientific term. They are no such things as quasi-reactionless methods. Scientifically speaking, the cited methods are entirely based on the principle of action-reaction. They simply rely on a reaction with bodies considerably heavier than the average mass of the propellant aboard a conventional rocket. They exchange equivalent momentum with their reaction mass, or they do not. There is no in-between. The fact that the mass the thruster reacts with is not expelled out of its back but the interaction rather takes place through gravitational or electromagnetic fields, is not an excuse to say "they are reactionless drives, but in fact, not really". This is totally absurd.

3. Non-working reactionless drives have indeed been built: Dean drives and all their derivatives like the Gyroscopic Inertial Thruster (GIT), which only appear to work due to friction with the ground, but cannot work in free fall or in outer space.

4. A true working reactionless drive however, which would not even "break the laws of physics" could exist: a device that would locally generate a gravitational potential, from the smallest impulse engine with a slight positive distortion of spacetime, to the complete superluminal Alcubierre warp drive with its powerful hypothetical negative energy source (also, the very conceptual "Swimming in spacetime" idea). Such a drive would be reactionless, but also thrustless…

Hence the article, which states that a reactionless drive could not exist, is mostly right in the definition of the term, but wrong throughout the article in the presented examples.

Thus I propose to change the title of the article (WP:MOVE) to propellantless drive with a dedicated section "Reactionless drive" dealing with the true problem such a drive raises with conservation of momentum, and possibilities regarding gravity. Indeed a "reactionless drive" is a particular case of a "propellantless drive", not the other way around.

— Tokamac (talk) 18:12, 11 December 2016 (UTC)

Actually the facts are worse, since the "propellantless propulsion" page already exists: it is Field propulsion. So I guess we have to clean this existing page instead. — Tokamac (talk) 22:06, 11 December 2016 (UTC)

So I removed the WP:MOVE notice and instead reworded the whole article in terms of open vs closed systems that completely addresses the difference between propellantless and reactionless drives. The article is now scientifically correct. — Tokamac (talk) 01:06, 12 December 2016 (UTC)

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References

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New type of "Reactionless" Thruster

There's very little to share at this moment, mainly this video and its lengthy description.. https://www.youtube.com/watch?v=NhpHWI5Mwhc

Centrifugal balancers (LeBlanc Balance) have been around for almost a hundred years using the "outside acceleration" of the centrifugal force to dynamically balance rotating loads. We've known since Newton that the first two laws of motion and Conservation of Momentum don't behave as expected/apply in non-inertial systems(having "outside sources of acceleration"). And we've known just as long that an inertial release from a spinning object has a reaction caused by the sudden change in mass distribution relative to the axis of rotation, which looks similar to, but is different from, a rotating wheel perimeter impacting a stationary mass and spontaneously accelerating it. This novel arrangement uses the above to generate a Net Force that is unbalanced. Dave Whitlock (talk) 02:27, 1 March 2017 (UTC)

• Sorry but this definitely counts as Original Research which is a no-no for Wikipedia. Andyjsmith (talk) 08:55, 1 March 2017 (UTC)

MACH Effect Thruster

Would it be appropriate to include a mach effect thruster in this article?

https://arc.aiaa.org/doi/abs/10.2514/6.2014-3821

--Patbahn (talk) 17:22, 27 September 2017 (UTC)

This is a duplicate of the Woodward Effect, noted in the first section of this Talk page. It has not been added to the page but I would support it.

DouglasHeld (talk) 20:55, 8 September 2021 (UTC)

Fringe theory

I removed the positive result on the RF resonant cavity thruster, because it is not referenced in a reliable science journal, but rather in a business magazing, and that result is two years old, and no reputable physics lab has been able to replicate these results in the following two years though several have tried. I removed it under the Wikipedia editing dictum of not giving undo prominence to fringe theories. Nick Beeson (talk) 01:14, 27 March 2018 (UTC)

I find it to be rather inconsistent to remove claims regarding RF thrusters (presumably the Emdrive and Cannae/Fetta ones), while leaving the others. There exists a large number of academic papers on the subject, and the Emdrive in particular has received government-level financial support. As a professional physicist, I of course consider this entire Wiki article to be a complete waste of space. Nevertheless, why keep the Cowlishaw nonsense, for example, while deleting the RF cavity drivel? — Preceding unsigned comment added by 82.2.156.175 (talk) 16:09, 22 December 2018 (UTC)