Talk:Magnetic sail/Archives/ 1

superconducting ?

A magnetic sail or magsail ... a large loop of superconducting wire

Does it have to be superconducting ?

Given the low field strenghts needed, I guess not, but then it constantly drains energy from its onboard electric power source, dissipating it in loop by Ohm's law, shortening the total time of acceleration (and thus limiting maximal velocity) of spacecraft. Besides, wire would have to be thicker and therefore heavier.

is "magnetic sail in magnetic field" illustration correct ?

A magnetic sail in magnetic field (represented by magenta arrows). The sail generates its own magnetic field, represented a small bar magnet. The ambient magnetic field pulls on the magnetic sail like any other magnet. The force on the sail is to the left.

I'm almost certain this is incorrect. A constant (over the volume enclosing loop) magnetic field exerts no net linear force on a current loop. However, it *does* exert a torque on that current loop. The torque tends to "line up" the loop with the field. Once it is "lined up", there is no net torque on the loop (only a force on each small segment of the loop pulling it out from the center of the loop). By "lined up", I mean that the loop's "dipole vector" (at right angles to the plane of the loop) is anti-parallel to the magnetic field vector. The magnetic field produced by the loop tends to cancel out the ambient magnetic field.

On the other hand, if the magnetic field is diverging (stronger in some place than others), there *can* be a net linear force on a current loop. I don't think any magnetic sails designs make use of this property.

(EditHint: move this to a physics page ?)

-- DavidCary 07:24, 11 Jul 2004 (UTC)

I could create a less mspaint-ish illustration, once I know what it should actually depict (I'm not too good at physics, damn me). So, if you have any exact ideas, please tell me. Until then, I'll do the other illustration. Frank Miller 22:45, 2 December 2006 (UTC)

Deleted illustration

I deleted the illustration Magnetic sail in a magnetic field. It was not terribly informative, and (as discussed above) did not accurately illustrate where the force comes from. The force on a magnet in a magnetic field comes from the gradient of the field, not from the field itself. In the illustration as shown, there would be a restoring torque on the sail if it is rotated, but no net force. The actual physics are much more difficult to show in a simple illustration. Geoffrey.landis 17:13, 28 February 2007 (UTC)

Merge From Mini-magnetospheric Plasma Propulsion

I merged Mini-magnetospheric Plasma Propulsion into this page. There was a fair bit of shared material, and the concept of M2P2 can only really be understood once you understand the magnetic sail. --Dashpool (talk) 16:26, 1 June 2008 (UTC)

See Talk:Mini-magnetospheric plasma propulsion. --Dashpool (talk) 06:58, 3 June 2008 (UTC)

Steering magnetic sails: [[1]] --Dashpool (talk) 08:10, 3 June 2008 (UTC)

moved unformated text from article

7. Bolonkin A.A., Theory of Space Magnetic Sail. Some Common Mistakes and Electrostatic MagSail. Presented as paper AIAA-2006-8148 to 14th AIAA/ANI Space Planes and Hypersonoc Systems and Technologies Conference, 6-9 November 2006, National Conference Center, Canberra, Australia. See also paper AIAA-2006-7709. In work is shown that the most magnetic sail researchers made a common mistake: not include the opposed magnetic field created the rotated solar wind around magnetic ring. This opposed magnetic field significantly decreases efficiency the magnetic sail.
8. Bolonkin A.A., Non-Rocket Space Launch and Flight, Elsevier, 2006, 488 pgs. Chapter 13: Electrostatic solar wind propulsion, pp. 245-270. Author offered the new electroctatic magnetic sail where the solid superconductivity gigantic ring is changed by electronic ring rotated abound positive charged ball.
9. Bolonkin A.A., New Concepts, Ideas, Innovations in Aerospace, Technology and Human Science, NOVA, 2008, 400 pgs. Chapter 4: Theory of Space Magnetic Sail. Some common Mistakes and Electrostatic MagSail. Author shows that the most magnetic sail researchers made a common mistake: not include the opposed magnetic field created the rotated solar wind around magnetic ring. This opposed magnetic field significantly decreases efficiency the magnetic sail.

Patents:
[1] Bolonkin, A.A., Space Propulsion Using Solar Wind and Installation for It, Russian patent application #3635955/23 126453, 19 August, 1983 (in Russian), Russian PTO.
[2] Bolonkin, A.A., Getting of Electric Energy from Space and Installation for It, Russian patent application #3638699/25 126303, 19 August, 1983 (in Russian), Russian PTO.
[3] Bolonkin, A. A., Transformation of Energy of Rarefaction Plasma in Electric Current and Installation for it. Russian patent application #3663911/25 159775, 23 November 1983 (in Russian), Russian PTO.
Ö

User BKruglyak added a large chunk of text criticizing the magnetic sail concept. Although the criticism itself may be notable, it does not merit the emphasis given by allocating a large section of text here. Was also poorly formatted and contained personal attacks on integrity of various researchers. It probably merits a couple of sentences in the main body of the text: something like "most analyses of magnetic sails have neglected the magnetic field generated by the solar wind itself as it interacts with the sail. These dynamically generated fields could overwhelm than those generated by the coil, and significantly reduce the efficiency of the device." (and an appropriate citation). --Dashpool (talk) 07:23, 8 July 2008 (UTC)

Without the above references, the text is unreferenced, so I've moved it here. Whether it is correct or not, the tone, style and formatting is inappropriate. If anybody wants to fix it up with the references and re-add to the article, please do so.- (User) WolfKeeper (Talk) 15:39, 8 July 2008 (UTC)

I recently proposed reorganizing this article in the "Theory in the limit of small plasma densities" talks section to include a section on critiques, similar to the unsigned talk post suggesting a section on "Critism." I recommend that the Bolonkin 2006 article "Theory of Space Magnetic Sail. Some Common Mistakes and Electrostatic MagSail" be cited and briefly summarized in such a section. A rebuttal by Vulpetti at https://centauri-dreams.org/wp-content/Bolonkin%20Refutation_edited.pdf should also be cited and summarized. There are several critiques on the M2P2 approach, some of which also apply to the plasma magnet (e.g., 1/r magnetic field falloff rate vs classical 1/r^3. Dmcdysan (talk) 19:15, 23 June 2022 (UTC)

I added a paragraph citing and summarizing the Bolonkin 2006 critique and a 2014 rebuttal by Vulpetti. Dmcdysan (talk) 22:23, 15 August 2022 (UTC)

Criticism:

  The simplest computation shows a profound mistake in the most known works about MagSail. 
Some of them (40) are presented in [7].

  Take the typical MagSail ring: radius of ring is R = 50 km, electric current I 
=104 A. 
The intensity H1 of magnetic field in center of ring is

 H1=I/2R=104/105=0.1   N/m,	(1)

This intensity is approximately same of the ring as well as near it.
We assume in our subsequent computation that H₁ = constant.

 Take the typical solar wind flows into ring at distance from Sun 1 AU (the Earth’s orbit 
about its primary star) with average wind speed V = 400 km/s, and density N = 
107 1/m3. The solar wind contains electrons and protons. 
Within the ring magnetic field they rotate under Lawrence force and produce their own 
magnetic field that is OPPOSED to the ring magnetic field, decreases it (diamagnetic 
property), and pumps the ring magnetic energy into energy of its own magnetic field 

(summary energy is constant). This magnetic field from the rotated electrons (we 
here neglect the additional magnetic field from the rotated protons) can be estimated by 
equations (we consider only electrons into the ring):

H₂=i/2r, r=V/(q/m_e)/B, i=3.14R²qNV, B=mu_oH₁ , (2)

where H₂ is magnetic intensity from rotated solar wind electrons, A/m; r is
electron gyro-radius, m; i is electric currency of solar wind electrons,
A; V = 400 km/s is average solar wind speed, B is magnetic intensity,
T; mu₀ = 12.56x10^-7 is magnetic constant.

  Substituting our values, we received r = 18.2 m; i = 5024 A; H2 = 276 A/m. 
The last magnitude shows that the magnetic intensity of solar wind electrons is in 
2760 times greater 
(H2 >> H1) than the ring magnetic 
intensity of MagSail! It is correct fo any charged beam that interacts with the MagSail.< 
That means all research and computation (without an influence the solar wind or charged 
beam into MagSail) is wrong and basically worthless for all practical space exploration 
and exploitation applications.

  How can it happen that hundreds of researchers, professors at famous universities, 
audiences of specialists, members of scientific Conferences and Congresses, editors of 
scientific journals: "Journal of Propulsion and Power", (Editor V. Yang); 
Journal "Spacecraft and Rockets", (Editor V. Zoby), paid so little attention to student-
level mistakes in many scientific publications and public presentations to scientific 
conferences? More over, the director NASA Institute for Advanced Concepts (NIAC)

Mr. R. Cassanova awarded (totaling more than $1 million dollars!) to his close
associate, professor R.M. Winglee (University of Washington) for pseudo-scientific work
about MagSail.[7]* (See also [2], [3] )

It is still happening because popular textbook authors continue to consider the
interaction between the strong magnetic field of particle accelerators and small amount
of charged particles where we can neglect the influence of charged particles in
magnetic field of the accelerator. With MagSail’s, we have the opposed situation: the
weak ring magnetic field and strong magnetic field of solar sail or charged beam.

7. Bolonkin A.A., Theory of Space Magnetic Sail. Some Common Mistakes and Electrostatic MagSail. Paper AIAA-2006-8148 presented to 14th AIAA/AHI Space Planes and Hypersonic System and Technologies Conference, 6-9 November 2006, National Conference Center, Canberra, Australia. See also AIAA-2006-7709 or BolonkinA.A., New Concepts, Ideas, Innovations in Aerospace, Technology and Human Science, NOVA, 2008, 400 pgs. Part A, Chapter 4.
8. Bolonkin A.A., Non-Rocket Space Launch and Flight, Elsevier, 2006, 488 pgs., Ch.13, pp.245-270.

Who is Zubrin?

Changes are needed in the "Principles of origin and design" section to clarify who Zubrin is and assert the notability of his mention in this article. Specifically, I'd like to see a link over to Robert_Zubrin and a mention of his name before "Zubrin's proposed magnetic sail design would ...", which leaves readers scrolling back up to see if they missed prior mention of him. Failing that, perhaps rewording to "The original design..." ◗●◖ falkreon (talk) 00:25, 30 March 2009 (UTC)

Can Such devices be used to leave the earths gravitational field?

For sufficiently (nuclear powered?) devices - would the generation of a magnetic field/associated electric field enable escape from the earths own gravitational pull (in theory, of course).

ConcernedScientist (talk) 22:08, 22 April 2009 (UTC)

No, unfortunately things like the ionosphere and high winds etc would mess with your influence too much. Plus the size of your device would be gigantic... But they can travel around orbital levels, which might be useful for satellites. There are plenty of other ways to get up there. 99.236.221.124 (talk) 22:12, 5 May 2010 (UTC)

Magnetic bacteria as natural magnetic sails

With the discovery of magnetite crystals in the famous martian meteorite and their resemblance to the magnetite crystals made here on earth by magnetic bacteria I would love to hear a discussion on possible panspermia mechanisms involving the physics of the magnetic sail on magnetic bacteria. TSpencerGrow (talk) 09:20, 27 September 2010 (UTC)

Critism

It would be nice if there was a section with views from detractors or just explaining the problems with this system. The Solar Sail as well as the ramjet article could use the same. —Preceding unsigned comment added by 98.232.220.23 (talk) 14:12, 21 September 2010 (UTC)

Speed

"A common misconception is that a magnetic sail cannot exceed the speed of the plasma pushing it."

I can understand how you can do that with a normal sailboat. By slowing down the air and speeding up the water, you extract energy and preserve momentum. You then use that energy to speed up the boat and slow down the air and water.

With a magnetic sail, there's just the plasma, right? From the point of reference that the plasma is still, how can the sail accelerate? — DanielLC 01:37, 11 May 2011 (UTC)

It should be capable of repelling from a planet far from the poles if aligned to field lines, no?

If the craft (or just the sail itself) is aligned with the field lines of the planet's magnetosphere, shouldn't it be capable of repelling from (or attracting to) the planet even when away from the poles? --TiagoTiago (talk) 17:17, 6 November 2011 (UTC)

Methods of Operation: Sailing against the Plasma Wind

Dmcdysan (talk) 20:17, 11 June 2022 (UTC)This section needs citation(s), and could be written more clearly. I will begin working on this and submit some proposed citations and likely revised text.

I have read quite a bit about magnetic sails, but have never seen anything like the following:

"A common misconception is that a magnetic sail cannot exceed the speed of the plasma pushing it. As the speed of a magnetic sail increases, its acceleration becomes more dependent on its ability to tack efficiently. At high speeds, the plasma wind's direction will seem to come increasingly from the front of the spacecraft. Advanced sailing spacecraft might deploy field coils as "keels", so the spacecraft could use the difference in vector between the solar magnetic field and the solar wind, much as sailing yachts do."

It appears to make an analogy with sailboats that may not be valid.

I recommend deletion unless someone can cite a reference. Dmcdysan (talk) 20:17, 11 June 2022 (UTC)

Inside a planetary magnetosphere

Did some searching and added a citation to a Zubrin 1991 paper. Appears that text is a high-level summary of that paper.

"The range of maneuvers available to a magnetic sail inside a planetary magnetosphere are more limited than in a plasma wind." is unclear, not sure what was intended. A later sentence mentions "limited maneuvering capability."

Marked statement for "similar to electrodynamic tether" as needing citation since it is unclear. Cut and pasted it below: In a similar manner to an electrodynamic tether. [citation needed]

Text uses "magnetosphere" in many places where planetary magnetic field should be used instead. Made these corrections. Following cut and pasted the following: "Just as with the more familiar small-scale magnets used on Earth, a magnetic sail can only be attracted towards the magnetosphere's poles or repelled from them, depending on its orientation."

Looked for references that cited the Zubrin 1991 paper and there are many, but did not find any that appear proposing to advance/refine this work. Didn't find any that refuted it either. More recent, relevant citations are still needed, otherwise this should be a historical note.

A magnetic sail in a spatially varying magnetic field. Because the vertical external field B_ext is stronger on one side than the other, the leftward force on the left side of the ring is smaller than the rightward force on the right side of the ring, and the net force on the sail is to the right.

Figure in this section was not helpful in explaining this to me. It is not from the Zubrin 1991 paper. Recommended deletion, cut and pasted here. Other issues are that figure does not show that magnetic sail cannot be reoriented with respect to magnetic field. Lines are not magnetic field lines, possibly height is supposed to indicate relative strength, but this is not a commonly used convention.

Removed invisible comment stating that section need clean up.

Dmcdysan (talk) 21:20, 23 June 2022 (UTC)Dmcdysan (talk) 04:06, 30 June 2022 (UTC)

In a plasma wind

Edited text in this subsection and provided citations and links to other Wikipedia pages that have citations.

Figure is not useful. Better covered in Wikipedia page 'Lorentz force" since this the Figure attempts to depict F = v x B inaccurately. All other paragraphs are marked citation needed. Cut and pasted them and the Figure here in case someone wants to add citations or discuss resurrecting the Figure.

A magnetic sail in a wind of charged particles. The sail generates a magnetic field, represented by red arrows, which deflects the particles to the left. The force on the sail is opposite.

Just as with solar sails, magnetic sails can "tack". If a magnetic sail orients at an angle relative to the solar wind, charged particles are deflected preferentially to one side and the magnetic sail is pushed laterally. This means that magnetic sails could maneuver to most orbits.

Solar weather also has major effects on the sail. It is possible that the plasma eruption from a severe solar flare could damage an efficient, fragile sail..

A common misconception is that a magnetic sail cannot exceed the speed of the plasma pushing it. As the speed of a magnetic sail increases, its acceleration becomes more dependent on its ability to tack efficiently. At high speeds, the plasma wind's direction will seem to come increasingly from the front of the spacecraft. Advanced sailing spacecraft might deploy field coils as "keels", so the spacecraft could use the difference in vector between the solar magnetic field and the solar wind, much as sailing yachts do.

Removed

since citations have been added and old text cut and pasted here in case discussion needed.Dmcdysan (talk) 22:15, 25 June 2022 (UTC)

Mini-magnetospheric plasma propulsion (M2P2)

Edits, comments, discuss and cuts to previous text on this topic. Dmcdysan (talk) 01:31, 4 July 2022 (UTC)

Cut "inflate the magnetic field using a plasma in the same way that the plasma around the Earth stretches out the Earth's magnetic field in the magnetosphere." Reworded to include inflation but Earth does not inject plasma into its magnetosphere.

Cut, Discuss "currents that run through the plasma will augment and partially replace the currents in the coil." Not clear if this is consistent with M2P2.

Comment "This is expected to be especially useful far from the Sun, where the increased effective size of a M2P2 sail compensates for the reduced dynamic pressure of the solar wind." This is actually true for many magnetic sail designs. Moved into MHD section and reworded where equations can demonstrate this fact. May need more work and rewording to clarify this important point.

Cut "The original NASA design proposes a spacecraft containing" This was a NIAC funded project.

Cut "The protons and electrons which make up the solar wind are deflected by this magnetosphere and the reaction accelerates the spacecraft." Applies to all magnetic sail designs. Covered in "Physical principles."

Discuss. "The thrust of the M2P2 device would be steerable to some extent, potentially allowing the spacecraft to 'tack' into the solar wind and allowing efficient changes of orbit." True for the coil but unclear regarding injected plasma. Did not find this in Winglee 2000 citation.

Moved. "A beam-powered of M2P2 variant, MagBeam, is also under development." Moved to a new section in "Designs" titled "Beam Powered" alongside similar text.

Discuss: "Robert Winglee, who originally proposed the M2P2 technique, calculates a specific impulse of 200 kN·s/kg (roughly 50 times better than the space shuttle main engine). These calculations suggest that the system requires on the order of a kilowatt of power per newton of thrust, considerably lower than electric thrusters, and that the system generates the same thrust anywhere within the heliopause because the sail spreads automatically as the solar wind becomes less dense." Some significant criticisms of this analysis M2P2 performance have been published that contradict these staments.

Moved, Discus "the system generates the same thrust anywhere within the heliopause because the sail spreads automatically as the solar wind becomes less dense." Similar to another sentence. Actually true for many magnetic sail designs. May need more work and rewording to clarify this important point.Dmcdysan (talk) 02:00, 4 July 2022 (UTC)

Additional cuts, discussion Cut, Winglee calculated a specific impulse of 200 kN·s/kg (roughly 50 times better than the space shuttle main engine). These calculations suggest that the system requires on the order of a kilowatt of power per newton of thrust, considerably lower than electric thrusters. [citation needed] [Was not able to find this in any of the cited references.]

Dmcdysan (talk) 20:49, 27 July 2022 (UTC)

Various edits and suggestions

In the last day I made several edits, some when I was logged in and others when I was not. In general I found much of the article confusing, with conflicts and redundancies. E.g., there were often several conflicting estimates for ISM density from multiple sources, with no explanation of how these could be reconciled. I also thought that long discussions of the exact density may not belong here; perhaps the article should focus on the mechanics of magsail deceleration given various estimates thereof, without confusing the reader too much over the details about exactly what the ISM density is (it is apparently highly variable), noting only that the effective deceleration depends on this. Actually, it might be useful to find a comparison, not so much between different magsail designs/models, but between one model decelerating against ISMs of various densities. Since the effective deceleration is a (linear?) function of this, the kinds of trips available toward a star whose local ISM is .3/cm^ (local bubble average), .5/cm^3 (the Milky Way average), or perhaps even higher in some places, might be very different from those approaching Alpha Centauri at .1/cm^3. This might be much more interesting than the rather tedious and technical comparisons of the many different designs & models currently occupying about half the article.

I also removed many pointless "(m/s)" and related terms, as this is only useful when giving a specific number or range thereof, e.g., "20 m/s", and not when defining a variable or parameter, for the latter could be expressed in any units and the formula using them will still work out.

Much confusion remains despite the reorganization done last year. Many sections are highly technical; while this itself can be appropriate, they also present much of the information with insufficient context. In particular, the "Proposed Magnetic Sail Systems" section reads like a detailed history and review article for specialists, with little summary and contextualization which would help even a well-informed reader understand the significance of the many designs/models described therein. The back and forth between different authors is unhelpful; do the later ones improve upon or refute earlier ones? Which should we believe? And many sentences are simply unclear, e.g.: "An Icarus design published in 2020 used a Z-pinch fusion drive in an approach called Firefly that dramatically reduced mass of the fusion drive and made fusion only drive performance comparable to the fusion and magsail design." This ends a paragraph on Freeland's magsail design, and some brief reference to how its weight would compare to a fusion drive. But it is very unclear what this last sentence is supposed to add to the discussion. Does it mean that newer fusion designs are comparable in weight even to this particular magsail design? Then we need at the very least a qualifier like "however" to suggest that Freeland's comparison was incomplete. Is it comparing a "fusion-only" drive to one which somehow combines a fusion drive with a magsail? But the latter was not mentioned earlier, so it needs to be explained; I fear, however, that the sentence is simply garbled; I hesitate to correct or remove it because I am simply baffled about what it was supposed to say. Prima facie, the sentence seems to say something about fusion, and nothing about magsails, so we need more qualification to know why it is in this article, let alone this particular paragraph. This lack of contextualization and explanation of the significance of many statements is, I am afraid, typical of large parts of the article, which are hence going to be baffling even to well-educated readers trying to understand how feasible magsail technology might be. Much technical information and many equations are thrown out here without enough attention to the "bottom line" of telling the reader what we can glean from the data presented. This is especially true in the many long reports of theoretical analyses with varying assumptions. We need more focus on an overview of what this all means, and what each of the varying models might tell us about the overall topic. In short, it presents too much data, not enough information, let alone knowledge. ScottForschler (talk) 13:21, 9 October 2023 (UTC)

ScottForschler wrote "And many sentences are simply unclear, e.g.: "An Icarus design published in 2020 used a Z-pinch fusion drive in an approach called Firefly that dramatically reduced mass of the fusion drive and made fusion only drive performance comparable to the fusion and magsail design." This ends a paragraph on Freeland's magsail design, and some brief reference to how its weight would compare to a fusion drive. But it is very unclear what this last sentence is supposed to add to the discussion. Does it mean that newer fusion designs are comparable in weight even to this particular magsail design? Then we need at the very least a qualifier like "however" to suggest that Freeland's comparison was incomplete. Is it comparing a "fusion-only" drive to one which somehow combines a fusion drive with a magsail? But the latter was not mentioned earlier, so it needs to be explained; I fear, however, that the sentence is simply garbled; I hesitate to correct or remove it because I am simply baffled about what it was supposed to say. Prima facie, the sentence seems to say something about fusion, and nothing about magsails, so we need more qualification to know why it is in this article, let alone this particular paragraph."

I made some edits to this paragraph in an attempt to address your questions and comments. Is this clearer now? If you still have questions, please reply to this message so that we can separate out the multiple thoughts in your post and attempt to address them.

I think it is relevant to this article because advances in (proposed) fusion drives reduce mass and are comparable to magsail deceleration, which also has the issues raised by Gros in the kinematic section. Dmcdysan (talk) 20:41, 13 October 2023 (UTC)

ScottForschler wrote: "there were often several conflicting estimates for ISM density from multiple sources, with no explanation of how these could be reconciled. I also thought that long discussions of the exact density may not belong here; perhaps the article should focus on the mechanics of magsail deceleration given various estimates thereof, without confusing the reader too much over the details about exactly what the ISM density is (it is apparently highly variable), noting only that the effective deceleration depends on this. Actually, it might be useful to find a comparison, not so much between different magsail designs/models, but between one model decelerating against ISMs of various densities. Since the effective deceleration is a (linear?) function of this, the kinds of trips available toward a star whose local ISM is .3/cm^ (local bubble average), .5/cm^3 (the Milky Way average), or perhaps even higher in some places, might be very different from those approaching Alpha Centauri at .1/cm^3. This might be much more interesting than the rather tedious and technical comparisons of the many different designs & models currently occupying about half the article."

I deleted the paragraph regarding heliopause and clarified that the cited references use a range of values for the context of travel to Alpha Centauri. Also summarized only the Magsail design references describe deceleration in the ISM so I added a pointer there.

Here is the diff for the changes I made: https://en.wikipedia.org/w/index.php?title=Magnetic_sail&diff=prev&oldid=1180130604

Some answers to your other questions are answered in the Magsail section and a better summary might be made there involving factors such as plasma density, spacecraft velocity, size/current in the Magsail coil and ion distribution. Dmcdysan (talk) 18:37, 14 October 2023 (UTC)

Looking better. I did just edit the "Modes of Operation" introductory paragraph; see what you think of that. I didn't say anything about the distinction between particle and ion density; perhaps that should be mentioned here too. If it is mentioned later in the more technical sections, I confess much of the discussion there exceeds my physics and math skills, and so my eyes glaze over there a bit and don't know where to find this easily. But it seems to me that this is a fairly fundamental distinction which should be mentioned early on, and then referred to again as needed. Perhaps "particle" density is simply understood as density of /ionized/ particles, but that may not be obvious to every reader.ScottForschler (talk) 17:06, 15 October 2023 (UTC)

Please reply to your original post here (as I suggested on your Talk page) and not the most recent post so that the indented threads are kept separate. The way you are replying loses this context.

I undid your change since it does not reflect the compromise I thought we had reached in our private Talk session and specifically text that you agreed to there and then changed again here!

Please look at the Wikipedia policy https://en.wikipedia.org/wiki/Help:Reverting. As mentioned there I reached out to you on your Talk page and you agreed to my revision. You then made changes that differ from what you agreed.

You are approaching https://en.wikipedia.org/wiki/Wikipedia:Edit_warring

You had previously deleted material that clarified the distinction between ions and (atomic) particles.

I found another error that you created in another section that I will also need to correct.

You wrote "I confess much of the discussion there exceeds my physics and math skills." I agree, you continue to demonstrate this.

Have you read any of the cited references? Most are highly technical with many equations, numerical examples, plots, etc. Perhaps this page is not one where your comments and suggestion are helpful.

Keep in mind that the Wikipedia policy https://en.wikipedia.org/wiki/Wikipedia:No_original_research

states that the primary goal is to quote/paraphrase information from reliable sources. Sumlif2 (talk) 20:56, 15 October 2023 (UTC)

Sumlif2 is an alias I created with a different email.

Using this ID and Sumlif2 I have followed up with comments on ScottForschler (talk).

This is the error he created that I had to fix:

https://en.wikipedia.org/w/index.php?title=Magnetic_sail&diff=prev&oldid=1180317001

May appear to be minor but his edit made the equation ambiguous and in conflict with the cited reference.

I offered to work with him off-line to increase the summary paragraph to address some of his comments while conforming to The Wikipedia policy Wikipedia:No original research. Wikipedia is not the place to make original statements without a supporting reliable source. Dmcdysan (talk) 22:17, 15 October 2023 (UTC)

I was going to stop with the one longer reply on my talk page, but must make one note here too to defend myself against some rather strange accusations.

You say "I undid your change since it does not reflect the compromise I thought we had reached in our private Talk session and specifically text that you agreed to there and then changed again here!"

I believe you are egregiously misrepresenting our dialogue there; I will not accuse you of doing so intentionally, as I grant that we have discussed a great many topics and edits recently and you might have gotten confused about the scope of certain points. What we agreed to was a general compromise about specifying units when defining terms (albeit one we were both somewhat unhappy with, though I think you recently came closer to my opinion after seeing others' views on this). We did not come to any agreement about whether most of the variables and equations listed under paragraph 1 of "Modes of Operation" were needed at all. Or rather, I presented some reasons for thinking they weren't, and saw no response to these reasons, nor any further reasons you gave for keeping them. I'm not going to fight your reversion, I'm simply pointing out that you haven't justified it. If I can't convince you of that, or you convince me of the contrary, then we must invite third parties to weigh in, if anyone is interested.

You say: "You had previously deleted material that clarified the distinction between ions and (atomic) particles."

I don't think this is an accurate accusation, either; please point me to any such material. After checking a pre-Oct 8 version, the only sentence I am aware of previously editing which even included the word "ion" was in paragraph 1 under "Acceleration/ deceleration in a stellar plasma wind" where I removed what I think you agreed was some superfluous listing of the types of charged particles in the stellar wind; but this passage did not discuss atomic particles. In any case, I think it would be useful to make the ion-atom (or, more generally, plasma-gas) distinction in the opening paragraph of Modes of Operation, or near to it, rather than somewhere else, if it occurs or occurred anywhere else. I would be very surprised if I removed this distinction anywhere, as it is one I fully comprehend and believe is very important in this context. In any case, if I did remove any such distinction, please consider the usefulness of reinserting it here, or anywhere else it may be useful.

You say, "the Wikipedia policy Wikipedia:No_original_research states that the primary goal is to quote/paraphrase information from reliable sources"

This is not what it says, and your misrepresentation is telling. The term "primary goal" does not appear on the linked page; you might want to instead peruse Wikipedia:about which states that its "purpose is to benefit readers by containing information on all branches of knowledge." I might add that it follows from the purpose of "benefitting" readers that the information be organized and selected in a way which is maximally useful. Again, I am not objecting to quoting or paraphrasing information from reliable sources as such, and am neither trying to present anything that counts as original research. I am not disputing any documented facts. I am objecting to the organization, selection, and manner of presenting many of those facts. I am in particular objecting to throwing into articles needlessly complex terms, symbols, or formulae, when these do not further wikipedia's actual primary goal, and especially when they actively interfere with it; and their presence in other sources, which often have quite different purposes and audiences, is not alone a sufficient justification for their being copied here.

Finally, I now see what you are saying about my error in editing the discussion of astronomical units--but the error I made exemplified exactly why you shouldn't scatter (<units>) all over the article needlessly as you were doing before! When you talked about "the distance from the Sun $a_{\odot }$ (AU)" it looked like you were meaning that $a_{\odot }$ was another way of saying AU, with (AU) in parentheses to express this, just as you earlier said "astronomical unit (AU)," where the "(AU)" correctly and unambiguously expresses an abbreviation, or more generally an alternate name, not a unit to be used. I thought I was hence condensing redundant material. I confess it's been a while since I've seen the $a_{\odot }$ symbol, and forgot exactly what it meant (sol). But can you now see that your style choices regarding units, far from helping me, deeply misled me about this meaning? For the statement made here--that density decreases by the square of the distance to the sun--is a qualitative claim which is true regardless of what units are used (AU, km, miles or furlongs), and hence does not need a specification of units, so I thought that the "(AU)" served some other purpose. Well, even if you don't see that, I hope you are on your way to changing this style on other grounds, at least once many others started agreeing with me when I raised the question. By the way, $a_{\odot }$ never appears again in the article, except in the formula later in that sentence, which itself only describes in complex mathematical notation something which the rest of the sentence already said in plain English. Hence both the symbol and formula add nothing to any reader's comprehension of any point (you already said "sun" and everyone knows what that means; while anyone who doesn't know what "density" or "square" means will not be better informed by looking at the formula!) It looks more like the author (not necessarily you, if you didn't write this passage originally) was just showing off what they know about astronomical and mathematical symbols. So this also exemplifies why adding more technical symbols or equations to an article which doesn't need them doesn't always help, and can actually confuse the reader.

So mea culpa on a substantive point, and my error on specialized astronomical symbols; but tsk-tsk to you for your own original research decisions about how and when to express units in a general-purpose article, which encouraged this and many other confusions on the part of myself and perhaps many other readers.

And now I think (I hope) I'm done, sir. Best wishes to you and your article.ScottForschler (talk) 21:24, 16 October 2023 (UTC)

Mahalo. Aloha. Dmcdysan (talk) 01:06, 17 October 2023 (UTC)

"By the way, $a_{\odot }$never appears again in the article, except in the formula later in that sentence,"

Corrected different notation usage of "d" instead of $a_{\odot }$ as used in another equation. Another error caught - Thank you, Scott.

Clarified usage of ρ in other equations. Began deleting unnecessary units in this section as shown in the following diff:

https://en.wikipedia.org/w/index.php?title=Magnetic_sail&diff=1180673456&oldid=1180317001

Disagree that this case was original research since the cited source used this equation as well as the summary text.

The mathematical convention used in this article inserts equations into equations, not words into equations (not clear to me how to do this in general). Dmcdysan (talk) 03:08, 18 October 2023 (UTC)

Theory in the limit of small plasma densities

"A bow shock can be neglected in the limit of small plasma densities."

This is not what the C. Gros 2017 citation states in Figure 4 and Appendix B. It does state that the effective reflection area A(v) approaches zero as v/c approaches 1 (see Figure 4). Propose replacing the above sentence and summarizing Figure 4 and Appendix B that show that the regime of applicability is related to the ratio of velocity over plasma density in the text of the Effective reflection area subsection.

I looked at citations for the C. Gros 2017 citation and found several papers that cite the results but do not confirm the method. This result is at odds with other predictions, for example the Freeland 2015 "Mathematics of Magsails" and the 1988 Zubrin paper, but operation at high speeds in a low plasma density region such as the ISM invalidates the MHD model and instead this kinematic model would apply.

Comments?

A better organization for this article could be to summarize each of the major magnetic sail approaches and cite the major results and conclusions with reference to another section that contains the mathematical details. Another section could be that for critiques and that is where the material from "Theory in the limit of small plasma densities" would go with a changed title since the analysis is independent of plasma density and dependent only on ship's speed. Another section could compare results from the proposals and the critiques.

Thoughts, anyone? Dmcdysan (talk) 19:04, 23 June 2022 (UTC)

From sub-heading 1 "Deceleration in the ISM"

From C. Gros, using the analytic result for $v(x)$ and the current carrying capacity of state of the art coated superconducting wires, one can estimate the mass required for the magnetic sail.

Citation added to Crowl 2017

There are several issues with the Gros 2017 paper that the Crowl 2017 citation resolves. The issues with the Gros 2017 paper include:

• section 4.2 which has inconsistencies between the equations and example numerical values for Proxima Centauri (PC) coil radius R that differ by an order of magnitude and the mass estimates differ by a factor of 2;
• The optimization of current from Gros section 3.2 equations (15)-(17) that appear to not optimize stopping distance x_max, but instead the ratio of distance traveled to stopping distance. Equation (16) of Crowl appears to correct these issues.

My previous edits restored the equations to align with Gros 2017 before optimization, which align with Crowl 2017 that cites Gros 2017. Following bullets cut and pasted here for discussion. After the above corrections, the comments on requirements for missions may no longer be applicable.

• For a high speed mission to Alpha Centauri, with $v_{0}=c/10$, one finds $R\approx 1600\,{\mbox{km}}$ and $m_{tot}\approx 1500\,{\mbox{tons}}$. These requirements exceed by far the specifications of projected launch systems, such as of the Breakthrough Starshot initiative.
• For a low speed mission to TRAPPIST-1, with $v_{0}=c/300\approx 1000\,{\mbox{km/s}}$, one obtains $R\approx 50\,{\mbox{km}}$ and $m_{tot}\approx 1.5\,{\mbox{tons}}$. These requirements are well within the specifications of projected launch systems.

Comments?Dmcdysan (talk) 20:39, 6 August 2022 (UTC) Another issue with the Gros 2017 paper is that the calculation of the coil radius reported in Equation (23) for Proxima Centauri (PC) of R=1600 km is 11.2 times the value computed from his Equation (22) for the parameters stated in the paper. The Trappist-1 value of R=47 km is 4.6 times his Equation (22) for the parameters stated in the paper.

One source of these errors may be the derivation of Equation (10), which appears to have some calculus errors. I did some numerical integration and found that Equation (11) for stopping distance $x_{max}$ is 2 to 4 times optimistic as compared with the numerically integrated stopping distance. Other equations summarized in the Wikipedia article use Equation (11) as a basis and may also predict something different than numerical integration. I will move these Equations in the Wikipedia article here for discussion.

I will also move some of the other text from Gros into the Criticism section. — Preceding unsigned comment added by Dmcdysan (talk • contribs) 19:08, 15 August 2022 (UTC) Dmcdysan (talk) 19:32, 15 August 2022 (UTC)

Below is the cut text for discussion.

The analytic expression for the effective reflection area $A_{G}(v)$ from Equation MKM.2 allows for explicit solution for the time to stop from an initial velocity $v_{0}$ and the distance required $x_{max}$ from Equation MKM.1. Minimizing the stopping distance $x_{max}$ for a given spacecraft mass $m_{tot}$ yields Equation (11) as follows:

$x_{max}={\frac {1/0.081}{log^{2}((v_{0}/c)(I_{G}/I))}}{\frac {1}{m_{p}n_{p}}}\,{\frac {m_{tot}}{\pi R_{c}^{2}}}$

(MKM.3)

with initial velocity $v_{0}$. The velocity $v$ of a craft at distance traveled $x\in [0,x_{max}]$ is given by Equation (12)

$v(x)=v_{0}\,e^{a}\,\exp \left({\frac {-a}{\sqrt {1-x/x_{max}}}}\right),$

(MKM.4)

where $a=log((c/v_{0})(I/I_{G}))>0$. Further algebra results in Equation (14) of the time $t=t(x)$ needed to decelerate from $v_{0}$ to 0 over the distance $x$ as follows:

$t=\int _{0}^{x}{\frac {dx'}{v(x')}}={\frac {e^{-a}}{v_{0}}}\int _{0}^{x}dx'\exp \left({\frac {a}{\sqrt {1-x'/x_{max}}}}\right)$

(MKM.5)

Note that the time $t(x\to x_{max})$ needed to come to a full stop diverges in this model, a consequence of the curve fit approximation. Dmcdysan (talk) 19:33, 15 August 2022 (UTC)

Restored this text to main article. In an offline discussion with Adam Crowl confirmed derivation of Gros Equation (10) is correct. Resolved comparison with numerical integration confirming this result by noting that Gros's equation of Force has an effective coefficient of drag coefficient of C_d=4. Dmcdysan (talk) 19:39, 21 August 2022 (UTC)

Cut the following sentence - an interpretation of the equation, not stated in the subject article. Comments?

"The number of protons reflected per second is $A(v)n_{p}v$ , with every impacting proton transferring a momentum of $2m_{p}v$ to the craft with momentum conserved" Dmcdysan (talk) 19:46, 21 August 2022 (UTC) Replaced the above thought with a summary from the Gross 2017 paper.

Cut the following sentence since the mass estimation by Gros has several issues described above. The Zubrin/Freeland is better described and citations in the YBCO superconducting wire Wikipedia article are more recent and accurate. Comments?

Using the analytic result for v(x) and the current carrying capacity of state of the art coated superconducting wires, one can estimate the mass required for the magnetic sail, the acceleration as well as the stopping distance and time.Dmcdysan (talk) 20:35, 22 August 2022 (UTC)

This is an important result, and further clarification, summarization or clarification may be warranted. Dmcdysan (talk) 19:57, 23 October 2023 (UTC)

References

Magsail (MS) Electromagnetic deployment

I was reading the article and got to this point, I remembered seeing a report all about this and related concepts, deployment, construction, structures. It's a lot more detailed, newer, demonstrates different geometries. I tried to add a ref for this to no avail because I've no clue how to use this website, so I'll just put it here. Please add this if deemed worthy, if not, give it a read anyway because it's very interesting. See figure 3. https://core.ac.uk/download/pdf/76425321.pdf — Preceding unsigned comment added by 27.96.192.8 (talk) 14:34, 2 August 2023 (UTC)

Yes, interesting paper titled: HIGH-TEMPERATURE SUPERCONDUCTORS AS ELECTROMAGNETIC DEPLOYMENT AND SUPPORT STRUCTURES IN SPACECRAFT. I don't see the relevance of Figure 3. Regarding applicability to Magnetic Sail, page 22 indicates that Zubrin [13] chose not to use this method and instead chose centrifugal force (as described in the Magsail section), so IMHO it is not related enough to this article to cite. Thanks for sharing! Dmcdysan (talk) 17:25, 4 September 2023 (UTC)

Archive Test

Tried to change Cluebot III archive interval from 30 to 60 days, but must have typed in something wrong since it was archiving every day. This topic is an archive test. Dmcdysan (talk) 18:26, 8 January 2024 (UTC)