Talk:Reactionless drive

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Contents 1 Thornson Inertial Engine 2 moved from inertial drive 3 Zero point theory 4 EMdrive 5 NPOV, inaccuracy and expansion 6 Redirects for disjunction drive and differential sail 7 Centrifugal force drive

[edit] Thornson Inertial Engine

This page conveniently neglects to mention the Thornson Inertial Engine (TIE), although i think there used to be a seperate page for it.

The TIE has, so far, held up to all scrutiny.

- It still works when suspended

- It still works in a vacuum

- It still works when suspended in a vacuum --Arltomem 19:59, 15 August 2006 (UTC)

______________________________________________________________________________________________________________________________ Y'know, the conservation of energy and the conservation of momentum are really aspects of the same thing: in relativity, they combine to become the conservation law for the energy-momentum four-vector. Separating them amounts to pedantry. . . Anville 21:11, 7 June 2006 (UTC)

[edit] moved from inertial drive

Hmmm, there's currently only one link to this page. Aren't Alcubierre drives, Disjunction drives and Diametric drives intertial propulsion engines?

After reading the description of the Alcubierre drive, I would have to say it is not. It is not motion dependent on the function of inertia or internal movement. Indeed, assuming such a wave could be generated, the object to be carried along does not appear to need any moving parts at all. previously unsigned comment by Fresheneesz

Much of this article is a matter of opinion at best. At worst, it is false. If you are reading this believing that this is the last word, look elsewhere. Engines which do not use a propellant have been created, tested, and found functional. The Energy necessary to impart motion has been a problem. Ineffecient design has plagued the field. But, by creating internal momentum and then reabsorbing this momentum does not violate any law of physics. previously unsigned comment by User:71.215.54.11 2006-08-13T21:48:38

I think that a reactionless drive by definition violates the law of conservation of momentum. One cannot "reabsorb" momentum at a later time - thats a violation. Fresheneesz 08:06, 10 September 2006 (UTC)

[edit] Zero point theory

What about the Zero Point Theory? I don't see any direct reference to this, specifically, although this may or may not be identical to the "inertial drive" mentioned. GrammarGeek 08:36, 26 December 2006 (UTC)

[edit] EMdrive

Here's one that some good publications & agencies seem to believe:

• New Scientist
• Reports of a government grant

The claim here is basically that photons aren't bound by conservation of momentum, due to the difference between phase velocity and group velocity. Unfortunately, the engineer is quoted saying a production system would be designed to work "at absolute zero"[1], which tends to raise an eyebrow if you've looked at anything by Carnot. Perhaps that's a journalistic misquote, though, because the same source lists superconductors as having "near zero" resistivity.

I'll go ahead and make some redirects to the article from Roger Shawyer and his invention, the EMdrive. I only took two semesters of quantum, and that was years ago, but I remember phase and group velocity being surprising concepts that led to no surprising results. I trust my education more than the authority of The New Scientist, especially after their complete misunderstanding of amorphous alloys[2]; they didn't even mention dislocation theory, but instead printed something misleading and entirely inaccurate.

previously unsigned comment by User:Polyparadigm 2006-09-10T06:51:57

I wish I could read the rest of that new scientist article - however I doubt it would be any more helpful than the second. The second article says that light doesn't obey the conservation of momentum, however that is entirely untrue. Not only that, but the drive supposedly relys on the difference between phase velocity and group velocity. If you understand what group velociy is, then you know it is not the velocity of anything physical. No information, energy, matter, or anything else is transmitted at this "group velocity" - it is simply a pattern that we recognize visually. An equivalent example is two events that happen at close to the same time - like me clapping my hands here, and a star exploding 100 light-years in the distance. Of course I didn't cause the explosion, no information, or anything else was transmitted. But if you consider my hand clap, and the star's explosion to be part of the same entity, then you have a "group velocity" of much much greater than the speed of light. Group velocity cannot drive a spaceship anymore than clapping my hands can make a star explode. Fresheneesz 08:18, 10 September 2006 (UTC)

Thanks for refreshing my memory about group velocity. Yes, it fits the classic profile of using terms people aren't likely to understand the dictionary definition of to sell a bogus technology. It sounds like you're qualified to include this new device in the article; I don't believe I am.

By the way, sorry about the unsigned post. I assure you I didn't mean to be rude. It was late, and I've been off Wikipedia for a while, having gone cold turkey when it started impacting my carreer; I didn't even think of it.--Joel 06:00, 11 September 2006 (UTC)

This is my first posting of any kind to Wikipedia. I agree that invoking group velocity to explain anything sounds fishy, but in the absence of a detailed explanation of this EM drive I'm willing to give it the benefit of the doubt, for the following reason. Solar sails work by transfering some momentum from a photon to the sail, via red-shifting the photon. I could believe that a device could repeatedly transfer momentum from a photon to the drive on each bounce of the photon in a resonating cavity, each time decreasing the frequency of the photon. What is hard to believe is that bounces from one direction transfer more energy than bounces from the opposite direction. But maybe there is some way to selectively control the amount of momentum transferred based on the geometry or composition of the cavity. Ultimately, the photon will have to exit the drive opposite the direction of acceleration to have a net change in momentum of the drive. Of course, there is nothing "reactionless" about such a drive, so it's not violating anything. Until someone puts the technical paper describing the drive on-line, we won't be able to evaluate it carefully. -- User:Solar Fuel 14:23, 11 September 2006 PST

OK, after thinking about it, I realized that you can't transfer any more momentum from a photon to the drive by bouncing it around a resonator and then ejecting it than you would by just ejecting the photon without bouncing it. So the EM drive doesn't seem to make sense. -- User:Solar Fuel 14:46, 11 September 2006 PST

[edit] NPOV, inaccuracy and expansion

This entry seems to have a very snide tone, which is understandable considering that it is mostly about the debunked reactionless drives. However, it is definitely an NPOV issue. It also doesn't correctly define "reactionless drive", and simply states a priori that all such devices would violate Conservation of Momentum. They call that "including the conclusion in the premises", don't they?

It also needs to go into theoretical reactionless drives, such as the Alcubierre Warp. I have also heard of a reactionless drive that works within the boundaries of general relativity, known as "Inertia contol by metric patching", and it would behoove this entry to discuss it. There is, or was, also a page on the NASA site devoted to theoretical ideas for non-rocket based propulsion, including differential sails and similar ideas.

Rather than simply being snide about failures, this entry should discuss the theoretical possibilities of reactionless propulsion.

I'll do some of these changes myself, but I don't have all the resources necessary to make this page anything other than a power trip.

--71.223.34.127 17:28, 19 October 2006 (UTC)

Is the intro's definition incorrect? The first sentence seems pretty accurate to me. Fresheneesz 18:33, 14 December 2006 (UTC)

[edit] Redirects for disjunction drive and differential sail

Many people will probably get to this page searching for information on technologies like the disjunction drive and differential sail, so it should have links to them. 71.223.34.127 17:35, 19 October 2006 (UTC)

Never mind, I fixed my problem, that people would come here looking for theoretical drives, myself. This entry still has some serious NPOV issues, though.71.223.34.127 17:44, 19 October 2006 (UTC)

[edit] Centrifugal force drive

use the concept in a Magnetic Accelerator Gun (Railgun, coilgun) to accelerate and decelerate a mass on an oval track with the corners in the thrust axis. Accellerate on the direction of the thrust, declelerate on the opposite straightaway. The 'thrust' is the difference in centrifugal on the corners, created not by friction, but by continuous magnetic acceleration/decleration.

Don't really know how efficient this would be though. Definitly would need nuclear power to produce significant 'thrust'. Plus a huge moving part. The thrust would be pulsing (reciprocating engines are too), but multiple devices could smooth it out. If the weight was 10% of the mass of the ship and the resulting low-Centrifugal was 3Gs and the resulting high-Centrifugal was 10gs, you would get 1 G of forward acceleration, a pause then 0.3 G of backward acceleration, a pause, repeat (0.7G of profit).

Actually i'm not sure if it would work. The acceleration g-force on teh straightaway is backwards to the direction of desired 'thrust' Same for the decelartion in the opposite direction. The straightaway acceleration/deceleration will probably negate most or all (or more than all) of the centrifigal force profit.

The idea is that sattelite gyroscopes don't use reaction mass to stabilize or initiate rotation. They exploit the momentum from the gyroscopes' centrifugal force. Adding exploitation of molecular or atomic strong force bonds to the centrifugal force exploit of gyroscopes could result in a bigger and better exploit to create a no-reaction-mass net linear thrust (Hey when you are in a drag racer and pull 4 Gs, that seat keeps the human from being left behind).

Maybe having some mag-lev (hey theres already magnetic acceleration / deceleration - rides use it all the time, and mag-lev trains exist too) on the acceleration/deceleration straightaway would remove the negation of the centrifugal force exploit. Just put the wheels on the track (connect mass to ship) in the corners.--GreatInca 22:56, 12 January 2007 (UTC)

Its good that you're thinking so techincally. However, your centifugal force exploit violates the conservation of momentum. The acceleration added to the weight's velocity would come at the cost of the momentum of the 'ship'. What would really happen is that the centrifuge ring would start moving in a circle (in the opposite direction of the weight inside), but no macroscopic linear motion would occur. Fresheneesz 05:52, 10 January 2007 (UTC)

I was hoping mag-lev would enable a cheat. I don't know if an accelerating mag-lev train is puts an equal and opposite force onto the track, because it is floating. If it doesn't, it's an excellent loophole in the momentum conversation law, as long as the float is disabled when it comes to apply the centrifigual force to the ship. It is a mass riding around an oval ring, like the high-roller fair-ride (ovalloid ring with train going around inside, but turn off the ringed track-structure's rotation). Or an very squished super-loop / ring of fire. Add-mag-lev accel to the one straight part, and decel on the opposite straight part, and allow contact on the corners. But if Mag-lev acceleration is creating an opposite force on the track, then there is no loophole to exploit, because the 3rd-law of motion would negate the centrifugal force profit. I don't recall electromag guns having any recoil my Sci_Fi RPG book, so that's why I am thinking of mag-lev / electromag acceleration as a loophole exploit. --GreatInca 22:56, 12 January 2007 (UTC)

Well, sci-fi books sometimes get it wrong. Rail guns do indeed have recoil in the real world. Physical laws don't have loopholes. You say that a mag-lev train is "floating", which is a good description - but remember that whatever you're sitting is making you "float" as well. The electrons in the atoms of your chair are repelling the electrons on the surface of your skin and clothes, which levetates you upward. A maglev train works in a similar way, except it floats alot higher. Fresheneesz 01:11, 14 January 2007 (UTC)

This page really needs some clean-up. There should be a clear delineation between discussions of the scientific soundness of the general concept, claims to invention, and treatment in science fiction. Right now it reads like a jumbled mess, and the very strict statement that reactionless drives necessarily require the violation of conservation of momentum is both uncited and inaccurate. A quick counter-example is Miguel Alcubierre's warp metric. Whether this solution or others in its class are physical or not is besides the question, none admit non-conversative flow of momentum. --Rev Prez 20:11, 30 March 2007 (UTC)