Propellantless propulsion from plain-old Special Relativity

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Diogenes
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Re: Propellantless propulsion from plain-old Special Relativ

Post by Diogenes »

AcesHigh wrote:
well, yes, just like we needed a definition back in the 19th century to exclude all the thousands of objects we started finding on the asteroid belt, and Ceres also ended up being removed from the definition of a planet. In the same way, with the previous definition of a planet, we would end up with hundreds or thousands of objects farther from the sun being considered as planets. And I am sure that just as some people were against removing Pluto from the planets list, the same people would be against having a Solar System with 150 planets. However, they were not the ones providing a scientific definition that could serve as a threshold for removing those objects that had the same characteristics as Pluto.


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alexjrgreen
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Re: Propellantless propulsion from plain-old Special Relativ

Post by alexjrgreen »

Diogenes wrote:But tell me, how many Angels can dance on the head of a pin?
Quantum Gravity Treatment of the Angel Density Problem
Ars artis est celare artem.

RERT
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Re: Propellantless propulsion from plain-old Special Relativ

Post by RERT »

Back to the root topic I'm afraid... I just read the paper - the Arxiv version.

The says nothing I could spot about reaction forces, but simply does a careful calculation of the total force on two current loops in the case where the Lorentz force propagates at the speed of light. The answer (equation 50) manifestly need not be zero.

They have a fairly high opinion of themselves, with their short list of references being Newton, Maxwell, Heaviside, Einstein, Feynman, basic texts in mechanics and electrodynamics, and a 2012 paper on a similar subject!

Unfortunately the antiquity of that list would also imply that this should not really be news. I did find this quote in one of my undergrad texts, which might be pertinent:

"...the magnetic force of interaction, in contrast to the Coulomb electric force, thus violates Newtons Third law. So, therefore does the total force. [...] There are no particular grounds for supposing that Newton's third law must apply to electromagnetic forces. On the other hand it does turn out [...] that the law of conservation of momentum in a closed system can be retained by ascribing momentum to the electromagnetic field."

DeltaV
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Re: Propellantless propulsion from plain-old Special Relativ

Post by DeltaV »

RERT wrote:Back to the root topic I'm afraid...
Thread drift? On Talk-Polywell? Never happens!

WRT propulsion, an emitted EM field carrying opposite momentum must occur to balance the ponderable mass' momentum:

No emitted EM (closed system) = No propulsion.
Emitted EM (open system) = Possible propulsion.

GIThruster
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Re: Propellantless propulsion from plain-old Special Relativ

Post by GIThruster »

That sounds like it was written by an engineer for engineers. I know of no physicists who would so casually admit a failure of conservation.

I don't think most people rightly understand what a terrible thing it would be, for conservation to not hold. It is a dictate of pure reason, and as such a requirement for science to be worth doing. If there are ever circumstances under which conservation does not hold, these are really circumstances beyond some counter-intuitive dictate of QM or such, but rather a denial of the laws of logic that describe how our universe operates. If the basic principle of conservation does not obtain, there is no point in doing science, because it cannot lead us to a real working knowledge of the universe. Conservation is THAT kind of important.

When you read stuff that says conservation is not satisfied, it is either sensationalistic grandstanding intended to garner attention, like the bullshit at Eagleworks; or it is an example of astonishing ignorance permeating the engineering culture where it certainly does not belong. Both of these happen often. I had a discussion the other day with a retired MS ME who was telling me how any situation where one had a Coefficient of Performance above 1, was an example of a violation of conservation and I explained to him again, just as I had 8 years ago, that he does not understand what conservation is all about and needs to stop using that language. That is a completely wrong understanding of what conservation is all about, and this stuff is just everywhere.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

DeltaV
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Re: Propellantless propulsion from plain-old Special Relativ

Post by DeltaV »

I r engenear.

As Wanser points out in

[DEAD LINK]http://www.mehtapress.com/mehtapress/Jo ... file_5.pdf[DEAD LINK]

http://i-sss.org/upload/toc/JOSE/2/2/146/JOSE_146.pdf ,

traditional concepts of momentum conservation revolve around the assumption of constant masses. Variable masses upset the dogmatic applecart.

Tuval and Yahalom are, however, relying on emitted EM for momentum balance in a constant-mass system, thusly in compliance with tradition.

[EDIT: Fixed dead link]
Last edited by DeltaV on Sat Oct 31, 2015 10:46 pm, edited 1 time in total.

RERT
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Re: Propellantless propulsion from plain-old Special Relativ

Post by RERT »

GIThruster: the guy whose textbook I quoted (P.C.Clemmow of Cambridge University), as well as DeltaV, explicitly says that momentum conservation can be recovered. Tuval and Yehalom say the same thing at the start of their paper in the revised format. Nonetheless, the mechanical system will experience a propellantless force. I don't believe anyone is suggesting non-conservation of momentum, so I'm somewhat puzzled what you are railing against.

To quote further from the text, considering the interaction of two particles:

"the magnetic force on [particle 1] is (mu0/4Pi)*e1*e2*(V1 x(r x V2))/r^3,
and the magnetic force on [particle 2] is -(mu0/4Pi)*e1*e2*(V1 x(r x V1))/r^3

[the first] is the negative of [the second] only in the special case where V1 is parallel to V2. The magnetic force of interaction [...] thus violates Newton's Third Law..."

Which I think says the something very similar to the root paper, and a lot more concisely. What the paper adds is the scale of the effect for a vaguely practical setup.

R.

RERT
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Re: Propellantless propulsion from plain-old Special Relativ

Post by RERT »

(V2 X (r X V1)), of course! R.

GIThruster
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Re: Propellantless propulsion from plain-old Special Relativ

Post by GIThruster »

I'm not railing--just pointing out this is an improper use of the term, both in this paper, and especially in the recent conference paper Sonny caused all the fuss with by claiming he was violating conservation. This kind of language should have no place in the scientific community. It's just cheesy rhetoric and should not be pandered to as it invites us to think wrongly about conservation and about the basic project of science itself.
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

D Tibbets
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Re: Propellantless propulsion from plain-old Special Relativ

Post by D Tibbets »

AcesHigh wrote:....

3 - It must have cleared the neighborhood around its orbit....

"Pluto fails to meet the third condition, because its mass is only 0.07 times that of the mass of the other objects in its orbit (Earth's mass, by contrast, is 1.7 million times the remaining mass in its own orbit).[146][148] The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as the prototype for the plutoid category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.[149]"

In other words, clearing it´s neighborhood means that the particular object must be by far the largest mass in it's orbit.
You might argue that Pluto is not a planet because it is in a resonant orbit with Neptune, but you could reverse that argument and say that Neptune is not a planet.
no, you cannot, because Neptune is by far, VERY FAR, the largest mass in it´s orbit.


I am sure that when we are confronted with such a case, we will create a definition.

Fact is, we need a threshold, otherwise we would have hundreds (not 30) plants on the solar system. It seems you people are not searching for a good scientific definition of a planet... the definition you guys want is "what I studied at school".

Balderdash. The basis of your arguement is that Neptune is fare more massive than Pluto, true, but when it is pointed out that Neptune does not perturb Plutos orbit enough to make Plutos orbit enough to make it unstable through the mechanism of orbital resonance does not mean that the two "planets" have the same orbit. It just implies that in the course of their separate orbits, they never come close enough for close gravitational encounters.The orbits cross, but they are not the same. A simple glance may support your reasoning about mass differences, after all without the special condition of orbital resonance, surely Neptune would "clear" Pluto from it's orbit. But this qualifier is not included in the definition. A scientific definition must be con sidtant irregardless of the tests you submit it to. Some examples- A Earth or Mars type body in a resonant orbit with a super Jupiter, or even a binary star. (if you want to push the mass differential). Is the Earth twin now considered a dwarf planet?. And how about a body in exactly the same orbit as Earth but on the opposite side of the sun. Can only one be considered a planet? A better comparison might be a Mercury size body orbiting opposite Jupiter. They are both in the same orbit and one is much more massive than the other. Does this demote the Mercury body to dwarf status?

Definitions of planets should be applicable to any stellar system, not just the Sol system.
The only definitions that I can think of would be that the body is in a stable orbit around a star, is not fusing hydrogen to any meaningful extent (Jupeter may be fusing the occasional deuterium- deuterium in it's core, but it is trivial). And, the body is spherical. These criteria can be applied universally. You can add additional qualifiers like mass limits (it could elminate the need for sphericity considerations as the mass chosen would incorporate this, so long as you give enough margin so that mass vs volume does not contribute. A larger volume may be needed for a young gas dominate planet vs a rocky planet for sphericity considerations, then again maby not as it doesnt require much gravity for a gas to assume a spherical distribution. The same might be said for a liquid planet versus a rocky planet. Arbitrary radii or masses might then be applied for subclassing planets- dwarf, regular, giant, super giant... All of this is at least partially arbitrary, but at least it could be applied universally.
As I said, you could also eliminate trojans based of some shortfall in mass ratio, but again this does not apply to Pluto. It is not a trojan of Neptune., as it is not in the same orbit of Neptune. If you use the argument that Pluto crosses Neptunes orbit and thus must be grouped into Neptunes orbital influence and Neptune is far more massive than Pluto and so it alone deserves the title of planet, there is again a flaw. If Neptune is defined as a planet, then it must have cleared it's orbit, at least of those objects which are otherwise in the same orbit. Yet, pesky Pulto remains in the defined Neptune orbit, ergo Neptune is not a planet. Resonance must be accounted for, one way or the other. You can define a mass difference and assign the title to the dominate partner, and that is fine for the solar system. But it could break down is other star systems. It is bnot consistant and reasonable. You could have a super Jupeter in a resonant crossing orbit with a Earth size body. Should you demote the Earth body?

Stable orbit and minimum size/ mass/ sphericity are the only criteria that I think are reasonable measures across all star systems. This is not what is applied in the IPS definitions, and it is thus the nonscientific villain.
Whether you set limits that allows only Jupiter to be a planet, or admit the potential dozens of bodies that are round and orbit the Sun is irrelavent, just be consistent. The question of shared orbits or crossing orbits introduce complexities that are open to interpretation. If the orbit is stable for at least a billion years , for example, then it is good enough. Clearing an orbit is a dynamic and never ending process. Jupiter , or at least many examples of large to small planets orbiting stars may entirely eject other quite reasonable planets from the star system given enough time. Even a small planet might perturb a larger planet enough that it interacts with the parent star and gets ejected from the system. Heck, even a moon might do that. So, even the orbital stability is relative. You can only say the body is in a stable orbit within some time/ computed limit. Then there are the rare but possible encounters with extrasolar passing stars or orphan planets (is it still a planet?) that can perturb orbits.

Dan Tibbets
To error is human... and I'm very human.

palladin9479
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Re: Propellantless propulsion from plain-old Special Relativ

Post by palladin9479 »

AcesHigh wrote:
That definition was deliberately chosen to exclude smaller solar objects that are farther from the sun.
well, yes, just like we needed a definition back in the 19th century to exclude all the thousands of objects we started finding on the asteroid belt, and Ceres also ended up being removed from the definition of a planet. In the same way, with the previous definition of a planet, we would end up with hundreds or thousands of objects farther from the sun being considered as planets. And I am sure that just as some people were against removing Pluto from the planets list, the same people would be against having a Solar System with 150 planets. However, they were not the ones providing a scientific definition that could serve as a threshold for removing those objects that had the same characteristics as Pluto.
And this people is the problem with the world today. Nobody is willing to listen to an entire argument, after they find the first thing that triggers an ego self defense mechanism they go off and ignore everything else.

The important part of my comment was later after the part where you got defensive. I will repost it without the first part so you don't get triggered again.
It would been better for them to say "larger then X mass is planet, smaller then X but larger then Y is demi-planet, smaller then Y is asteroid". I don't care for politics and real-fact vs good-fact getting involved in science, it never results in anything good.
There an unbaised non-political metric that could be used universally. Astrophysicists, and not politicians or interested parties, could go back and forth on what the optimal values of X and Y would be, and ultimately they would decide on one that enabled a spheroid to accumulate some significant amount of layered atmosphere (solar wind not withstanding) and have some sort of significant gravity that enabled self organization and cohesion. Those values might, or might not include Ceres or Pluto, I don't care as long as they are universally applied.

I know that was longer then 140 characters but I absolutely hate lazy twittering.

paperburn1
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Re: Propellantless propulsion from plain-old Special Relativ

Post by paperburn1 »

By strict definition earth has not cleared its orbit.
Cruithne iss about 5 kilometers across, and has an elliptical orbit that takes it inside and outside Earth’s solar orbit. The orbital period of Cruithne is about the same as the Earth’s, and due to the strangeness of its orbit, this means it is always on the same side of the Sun we are. From our perspective, it makes a weird bean-shaped orbit, sometimes closer, sometimes farther from the Earth, but never really far away.
But it actually orbits the Sun, so it’s not a moon of ours. Our orbit is not technically clear.

So I have to go with Mr. Tibbets thinking again, are we a round planet( within 1 percent?) Are we a set radius or larger? Is our path stable?
I am not a nuclear physicist, but play one on the internet.

GIThruster
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Re: Propellantless propulsion from plain-old Special Relativ

Post by GIThruster »

Just because I have no idea where to put it and it doesn't deserve its own thread.

http://astronomynow.com/2015/03/31/race ... tensifies/

And it has to do with SR sorta. . .kinda. . .it does really!
"Courage is not just a virtue, but the form of every virtue at the testing point." C. S. Lewis

hanelyp
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Re: Propellantless propulsion from plain-old Special Relativ

Post by hanelyp »

"Clearing" it's orbit is, as demonstrated by examples given, a poor criteria for being a planet. Dominating it's orbit is a better expression, all objects in stable orbits near that of the planet orbit the planet itself or are in some kind of stable relationship (resonance, Lagrange points ...).
The daylight is uncomfortably bright for eyes so long in the dark.

D Tibbets
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Re: Propellantless propulsion from plain-old Special Relativ

Post by D Tibbets »

hanelyp wrote:"Clearing" it's orbit is, as demonstrated by examples given, a poor criteria for being a planet. Dominating it's orbit is a better expression, all objects in stable orbits near that of the planet orbit the planet itself or are in some kind of stable relationship (resonance, Lagrange points ...).
I have ranted about Pluto and considerations of competing orbits. To keep it simplier, consider only Ceres. It is round, and can anyone reasonably argue that it has not cleared it's orbit like any of the big boy planets? Obvously, its range of dominating influence is smaller than Jupiter, or even Mercury or Sedna, etc.
But there is nothing in the definition that stipulates the range of orbital wiodth that is cleared. again, the definition is haphazard and inconsistant. I am not argueing that Pluto or Ceres being labiled a dwarf planet is unreasonable, provided there are criteria that defines what a Dwarf planet is. Dwarf implies smaller, and assigning a limiting mass for a body to be considered in a certain subgroup of planets is fine, but this is not what the official definitions present.

And what is wrong with 300 planets in the solar system? It is a cultural bias to think that only 5, 8, 15, etc is enough. If the reasonable definition fits, then label an orange an orange. I could understand if only Jupiter was considered a planet, while all others were dwarf planets; or more (?) resasonaby, Jupiter, Saturn, Neptune, and Uranus were planets while all of the much smaller rocky 'planets' were designated as dwarf planets. Past round shape (most of the time), and stable orbit, any hopefully consistent cutoff definitions could be used.

As for atmospheres, there are so many variables that allow for long term atmospheres (more than the tenuous atmospheres that can be measured around even many asteroids). Things like stellar UV striping, presence of protective magnetic field, proximity to the star and the star luminosity and spectral class, etc can make for great differences in the atmosphere of similar sized planets. For instance, I think that Mars has lost most of it's atmosphere partially do to it's smaller gravity, but the lack of a good magnetic field has allowed Solar wind and UV radiation to strip away the gasses, especially the light hydrogen from split H2O. Venus, despite being heavier has had most of its water (assuming it had water) split by UV radiation and solar wind has carried away the hydrogen. Yet the atmosphere is dense due to massive vulcanism. The oxygen from the split water has combined with sulfur, so a nasty mixture of sulfuric acid and carbon dioxide persists as a dense atmosphere.

Dan Tibbets
To error is human... and I'm very human.

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