Talk:Launch loop

message: The article makes the statement "In 2008[10] Bolonkin proposed a simple rotated close-loop cable to launch the space apparatus in a way suitable for current technology."  Either I don't understand the statement (meaning it needs more explanation) or it is just plain wrong.
There is a quantity known as specific velocity (not unlike the characteristic velocity of a rotovator) that is equal to the square root of the quantity strength divided by density (σ/ρ)0.5.  It is in essence 0.707 times the characteristic velocity which contains the factor 2 in the numerator (2σ/ρ)0.5.  The characteristic velocity is defined as the maximum tip speed a rotovator with a uniform, untapered cable can attain.  The specific velocity is used for non-spinning tethers, and works out to be the maximum tangential velocity that a closed loop cable can withstand.  Beyond that velocity, the inertial loads exceed the strength and the loop breaks.
I know of no current technology with specific velocity greater than about 2 km/sec, let alone the ~7+ km/sec needed to launch a payload.  If I am wrong, what am I missing?  If the statement is wrong, it should be removed.
KitemanSA (talk) 03:37, 19 July 2008 (UTC)
replies: text: I haven't read the paper, but so far as I can make out Bolonkin's idea is still to magnetically contain the moving parts of the loop, but some of the technical details are different. He does away with the high acceleration portions, stuff like that.- (User) WolfKeeper (Talk) 14:27, 19 July 2008 (UTC)
thread_title:  Close-Loop Cable? 

message: The Description section is somewhat unclear, as it in the second paragraph starts talking about the vacuum sheath without actually telling how this is incorporated in the whole structure. Could someone who has better knowledge about the subject try to clarify this? OttoMäkelä (talk) 20:39, 30 December 2007 (UTC)
thread_title: Vacuum Sheath?

message: 'ts not clear how this works.
Is just a spinning rope, or is it working as a magnetic realgun ?  —Preceding unsigned comment added by 82.217.143.153 (talk) 23:09, 28 March 2008 (UTC)
replies: text: It's not really exactly either. The moving metal rotor when dragged past a magnet generates huge eddy currents that pulls the magnet along after the rotor.- (User) WolfKeeper (Talk) 01:45, 29 March 2008 (UTC)
replies: text: A good way to envision this is to think of a firehose with no one holding onto it. It will flail about in the air. The launch loop works on the same principle, except instead of moving water through the hose, you are moving an iron cable which is suspended magnetically with minimal friction. The "hose" is forced upward by the kinetic motion of the cable and held in check by the guy wires.  —Preceding unsigned comment added by 63.211.201.174 (talk) 11:12, 26 August 2008 (UTC)

text: It is, but it doesn't have to for this kind of structure to stand up. It works like when you squirt water across the garden from a hose, you could imagine you could hold up a structure with lightweight kite-like things that sit on top of the stream by deflecting it slightly.- (User) Wolfkeeper (Talk) 17:28, 25 October 2009 (UTC)

text: It just goes much faster and so can go much further.- (User) Wolfkeeper (Talk) 17:28, 25 October 2009 (UTC)

text: I couldn't get it either to start with. But then went to the original paper and read the author's description. He describes it so clearly, and I could immmediately see what he was saying. So have put his description as a quote at the head of this article, hope it helps others to read it and get the idea quickly as well. The rest of the article then is fine, clear and easy to read, once you understand the concept. Robert Walker (talk) 02:14, 22 November 2012 (UTC)
thread_title:  unclear article 

message: Is the design limited inherently to 5 metric ton payloads, or is it possible to increase that size? The article says that the launch loop is, in and of itself, able to reach LEO, escape orbits, GEO, and others. 
I understand how this would be possible with a "kick-start" booster on the payloads, but how is the launch loop capable of this "in and of itself"? It seems to me that at the given 3g acceleration, at the end of a 2000km long track an object would be traveling at about 10.5 km/s. If memory serves me that's not quite escape velocity on its own. I'm rusty on my physics, so that could be a wrong number. I might add at this point that by training I am not a physicist or engineer, although I feel that I can understand the concepts if pointed to the appropriate articles and given time.
:I made it 10.8 km/s. The other thing is that the rotation speed of the earth is ~500m/s, which gets you there near enough. But making the track a bit longer or pushing the acceleration up by a few percent is not a big deal. Neither is a small kick rocket to make up the difference.- (User) WolfKeeper (Talk) 18:15, 19 May 2008 (UTC)
replies: text: Just radiation through to the casing which then it turn radiates as well.- (User) WolfKeeper (Talk) 18:15, 19 May 2008 (UTC)

text: Kevlar maybe. Some sort of composite cable.- (User) WolfKeeper (Talk) 18:15, 19 May 2008 (UTC)

text: I was wondering the same thing.  Looked up strength of a few materials.  Kevlar has a breaking length of 256km.  So yes, I would say Kevlar could be used.  Also, carbon fiber (breaking length of 250km)  P0wder2 (talk) 00:02, 14 July 2013 (UTC)

text: It just detaches and the cable curves away as it follows the horizon.- (User) WolfKeeper (Talk) 18:15, 19 May 2008 (UTC)

text: Roughly inversely proportional. Most of the cost is in loans for construction and so forth, although there are some fixed running cost in electricity.18:15, 19 May 2008 (UTC)

text: It's probably not a solid pipe, the stake in the ground seems to be a joint every few meters. The exact details vary between the different published papers (which isn't surprising since they're 20 years apart!)- there's different ways to implement the concept described in the article.- (User) WolfKeeper (Talk) 15:02, 29 May 2008 (UTC)

text: I don't think there are any major ones, unlike space elevators that are quite constrained in that regard, but you'd have to check the paper on that. All launch systems benefit from being near the equator due to the rotation of the Earth, so I would guess you'd have to make the loop a bit longer as you move away, but not massively so. Hmm, it might be worth adding that to the comparison section as an advantage over space elevators.- (User) Wolfkeeper (Talk) 17:18, 17 January 2009 (UTC)
replies: text: As per a discussion with KeithLofstrom at the 2009 Orycon, energy requirements do increase when moving away from the equator, but there are other more serious concerns. Building in calm seas allows a far less expensive structure, and most (not all) equatorial regions are far calmer than the rest of the Atlantic and Pacific oceans. K7aay (talk) 06:39, 3 January 2010 (UTC)
replies: text: Are storms mainly a concern for a loop anchored to some kind of rig in the middle of the sea? Is it less of an issue if both ends are planted on solid ground? Incidentally, if it's anchored to an island, how large would the island need to be? What about other natural disasters, could the loop withstand a severe earthquake? Otto (talk) 16:45, 1 April 2010 (UTC)
replies: text: IMO, it probably could survive an earthquake, a tsunami might be more interesting though. But we're really supposed to be discussing the tech here, the article is really the focus.- Wolfkeeper 17:22, 1 April 2010 (UTC)
thread_title:  A few questions 

message: I think Wolfkeeper did a great job of summarizing the idea - more details at , which also has a wiki where folks can add their own ideas.  More questions about this article can be asked and answered at [ http://wiki.launchloop.com//index.cgi?WikiPedia ], so we can respect the talk page guidelines here.  —Preceding unsigned comment added by 96.253.164.73 (talk) 03:37, 11 July 2008 (UTC)
replies: text: Well... I'm only doing so because if they ask questions or otherwise comment here then it helps us know whether the article is confusing and whether there's anything missing. I'm absolutely not guaranteeing to answer them though, although so far I have done so, and the level we're getting them at does not seem to be a problem; anything complicated I'll certainly forward to you ;-)- (User) Wolfkeeper (Talk) 17:07, 17 January 2009 (UTC)
thread_title:  KeithLofstrom here, with a few comments 

message: "To launch, vehicles are raised up on elevators to a loading dock at 80 km, and placed on the track"
...I personnally have never seen an 80 km high elevator. Anyone care to elaborate?--Perwfl (talk) 03:21, 21 November 2008 (UTC)
replies: text: I will when you elaborate on the 80 km high structure that you have seen that would need it.- (User) Wolfkeeper (Talk) 03:37, 21 November 2008 (UTC)
replies: text: That's not an answer to the person's implied question.  Don't be snide. --12.21.161.34 (talk) 19:41, 11 December 2008 (UTC)

text: It's a valid question.  The statement is that to get a vehicle on a launch loop, it needs to ride an elevator to 80 km above the surface, no easy feat.  The article explains how, through the garden hose analogy, the launch loop itself would be 80 km above the surface, but it doesn't explain how we can get a loading dock, which I assume would be stationary, up 80 km high. Cornince (talk) 21:48, 16 December 2008 (UTC)
replies: text: It's just a tapered cable hanging down from the dock that can be used to climb up to it. The self support length of Kevlar is 256 km for example.- (User) Wolfkeeper (Talk) 23:54, 16 December 2008 (UTC)
replies: text: Could you not just ride up the part of the main cable that comes from the ground? No need for an extra 80 km cable, I think. 76.112.8.174 (talk) 02:33, 17 March 2009 (UTC)
replies: text: Yes, that is theoretically possible, but there are difficulties due to the thickness of the sheath at the relatively high atmospheric pressures, as well as potential issues such as icing that can cause problems.- (User) Wolfkeeper (Talk) 02:43, 17 March 2009 (UTC)

text: Why not use the ascending section of the main loop to get up to 80km?  That way no elevators would be needed.  It's not like the structure couldn't handle it. Also, how close together would the coming and going rotors be?  Presumably some separation would be needed so that the electromagnetic forces needed for acceleration don't just cancel each other out?  John Hogan, 15 June 2013.  — Preceding unsigned comment added by 58.6.208.78 (talk) 17:43, 14 June 2013 (UTC)
thread_title:  Elevator? 

message: Do we know that we can, using magnetic forces, rotate this iron 80 km above the ground and control its movements?  Has this ever been demonstrated, even in miniature?  If not, how would one go about demonstrating this principle with, say, a miniature launch loop, that would lift perhaps just a few feet high and have minor acceleration?  One way to get investors in this project is to demonstrate physically that you can levitate and control this thing with magnets in a way that would facilitate launches. Cornince (talk) 21:52, 16 December 2008 (UTC)
replies: text: That's not a concern for the wikipedia. The wikipedia describes notable concepts. Whether or not it even works, it's still a notable topic.- (User) Wolfkeeper (Talk) 22:14, 16 December 2008 (UTC)
replies: text: Have any sources been found that mention such demonstrations of a working concept of a launch loop?  If such sources exist, that would be notable. Cornince (talk) 22:16, 16 December 2008 (UTC)
replies: text: It's a conceptual design which has never been built, so we cannot be totally sure whether it can be, but my understanding is that it's believed to be physically realisable, and there's no unobtainium or show-stopping problems that are known to exist and it has been examined fairly deeply over a number of years.- (User) Wolfkeeper (Talk) 23:58, 16 December 2008 (UTC)

text: I would say it's fractionally above technology readiness level 2.- (User) Wolfkeeper (Talk) 23:58, 16 December 2008 (UTC)
replies: text: Great.  When does the first testing of using magnets to run an iron pipe through a vacuum sheath while looping it around using magnets, with the streaming causing the pipe to levitate, but the levitation is supported by cables, occur?  Who'll do it?  If it's reasonably small scale, and the pipe doesn't need to move very fast for demonstration purposes, then the concept shouldn't cost too much to build. Cornince (talk) 02:27, 17 December 2008 (UTC)
replies: text: The program to build stuff is unfunded right now. Lofstrom himself doesn't have the cash. NASA has tried some linear maglev launch assist a few years ago, but they didn't seem to like it much; I'm not aware of any ESA program.- (User) Wolfkeeper (Talk) 03:12, 17 December 2008 (UTC)

text: John Knapmann and others are doing theoretical investigations into essentially the same concept but for suborbital use (Space Cable) and publishing and presenting papers. Lofstrom still gives presentations as well.- (User) Wolfkeeper (Talk) 03:12, 17 December 2008 (UTC)

text: I thought the proof of concept model had to be full scale in order to escape the gravity restrictions that a scaled down version would not overcome? --173.71.223.237 (talk) 16:35, 17 January 2009 (UTC)
replies: text: No, not at all, and the spaceCable described in the article is suborbital. Don't forget- it works just the same way as the water arch coming from a hose pipe, nothing needs to be orbital speed.- (User) Wolfkeeper (Talk) 17:36, 17 January 2009 (UTC)
replies: text:  Would there be atmospheric drag or other issues with friction that would require the proof of concept model to be full scale? Or would you just overcome that with a fully sheathed cable.  Would there then be additional issues with a fully sheathed model?  —Preceding unsigned comment added by Qwerspam (talk • contribs) 13:19, 9 March 2009 (UTC)
replies: text: Well, Keith Lofstrom and Paul Birch built a small desktop model that basically worked.- (User) Wolfkeeper (Talk) 15:31, 9 March 2009 (UTC)
replies: text: Source?- Cornince (talk) 08:11, 17 March 2009 (UTC)

text: I agree, is there a link to source material? --Qwerspam (talk) 19:20, 17 March 2009 (UTC)
replies: text: Not as far as I know, I saw a video of it once on TV, I think it was on Tomorrow's World or something. Apparently it was reasonably unstable, the full-up system would have various stabilisation systems, and their model was too crude for that; but it did basically work and lift, but it wobbled.- (User) Wolfkeeper (Talk) 22:02, 17 March 2009 (UTC)
replies: text: If anyone can find a source for that, that would be great.  Basically, if Longstrom wants to make his dream a reality, he needs to make lots and lots of desktop models and keep trying to stabilize the system and work out basic principles of stabilizing the magnets so they can be applied to the larger models (it costs less for a desktop model to fail) and then he needs to work on using the desktop models to launch little desktop model ships and come up with basic principles for how to do that; only then, he should move on to the larger models and to start to factor in things like winds and weather and other environmental conditions--and at that point, he should be getting more support for funding such a project. Cornince (talk) 16:12, 24 May 2009 (UTC)
thread_title:  Proof of Principle 

message: Delete this article.  This article has no citations relevant to the topic, other than articles written by Bolonkin.  Also, the article is written as though this non-existent device is both known to be feasible and seems to already exist.  Heathhunnicutt (talk) 16:31, 25 October 2009 (UTC)
replies: text: Careful here, the second reference is to a copy of an article that was published by the AIAA in 1985 by Keith Lofstrom; this was in a reputable journal. This article covers that paper, and other subsequent work; Lofstrom has since published at several major conferences, and there have been other papers published by other authors such as John Knapmann and (as you mention) Bolonkin on very similar systems.- (User) Wolfkeeper (Talk) 17:23, 25 October 2009 (UTC)

text: You may find that this is a wiki. In a wiki, people are at liberty to make changes. Feel free to read the linked papers or other sources on this topic and make any appropriate changes that reflect content from the references. Or, if you feel the wikipedia should not have this topic WP:AFD (good luck with that!)- Wolfkeeper 04:07, 16 December 2009 (UTC)
replies: text: No need to get testy, I'm simply saying it doesn't feel very encyclopedic. I will do my best to rewrite it. Barhamd (talk) 04:43, 17 December 2009 (UTC)
thread_title:  Factual article or propaganda? 

message: It appears from above that I'm not the only one to find the tone of this article to be a little biased.  My problem is that it seems to be actively preaching itself as the superior choice for our time/money/investment/etc. versus the tether space elevator concept.  While it may be true, the tone and wording is suspiciously preachy. - BalthCat (talk) 08:40, 21 December 2009 (UTC)
replies: text: Beanstalk-style Space Elevators are impossible to build at the moment anyway; the strongest practical engineering material is still a conventional polymer, and that material hasn't got the strength/weight ratio you need for this.- Wolfkeeper 18:10, 23 December 2009 (UTC)

text: I've added a tone tag to the top of the article.- Wolfkeeper 18:10, 23 December 2009 (UTC)

text: Really though, the article is only marginally above a stub anyway; it hasn't even been rated at C class, the article is much more sketchy than it may seem.- Wolfkeeper 18:10, 23 December 2009 (UTC)
replies: text: Tone is the wrong tag, as per WP:TONE.  I'm not referring to overly technical jargon, or overly casual tone.  I see the article as it is now as being overly concerned with comparing the technology with the space elevator tech.  The third lead paragraph for example.  Admittedly the article is in formation, but that doesn't mean the tag is inappropriate, it can stay there as long as it needs to.  - BalthCat (talk) 22:15, 23 December 2009 (UTC)
replies: text: The tag is inappropriate. There's no reason at all that information shouldn't be in the article about space elevators.- Wolfkeeper 16:27, 21 January 2010 (UTC)
thread_title: Neutrality

message: I am excited by the steady improvement of this wikipedia article, including the critical remarks that motivate Wolfkeeper and others to make those improvements.  Thanks all!
I spend most of my time on Server Sky , doing presentations and writing papers on that.  However, "dynamic structure" launchers are being explored by many people now, including some of the space elevator community.  One prolific author is Dr. John Knapman, inventor of the Space Cable .  You can find a bibliography at the bottom of this webpage .  While John and I differ on the details, his analysis is usually sound.  Other hard-to-find Launch Loop references include a December 1984 "Analog" article, an L5 News article from around 1985, and a September 1981 (IIRC) American Astronautical Society newsletter. 
There are also some articles by Paul Birch in JBIS,  and Ken Brakke in L5 News, about Orbital Rings.  Expect new journal articles about those dynamic structures from others, soon.
The launch loop wiki  is still the best place to find papers, presentations, and details.  While the peer-reviewed literature is vital, the journals are inaccessible or too expensive for most people.  Wikis promote multi-party conversation, which much better for collaboration and resolving details.  If you want to have more of a conversation about this, please go there.
Just for fun, if you want to see a "simulation" of a launch loop, look at this video  of Eugene Kovalenko's tabletop model.  While the pulley and the rubber belt seem primitive, what Eugene accomplished - a half-meter altitude, a couple of meters per second - is about a factor of 100,000 away from a real launch loop, and there are real lessons to be learned by watching it.  The space elevator games , involving a 1 kilometer tether suspended by a helicopter, is also about a factor 100,000 away from a real space elevator.  However, their tether and competition cost a few million dollars.   The relative difficulty and cost may scale all the way to full size.
KeithLofstrom (talk) 19:04, 20 March 2011 (UTC)
thread_title:  Keith Lofstrom again 

message: There is a serious physics problem with the end loops. The whole structure is meant to support itself on the centripetal force of an enormous amount of extremely fast moving mass flowing in both directions along a loop that is 2000 km long and more than 80 km high. When all of this fast moving mass reaches the end loop it does a U-turn in a small loop that is about 20 km in diameter. Has anyone actually calculated the force that it would take to make that U-turn? Are there actually any materials that could handle those forces? Even with a switch yard that spread the masses into a dozen different loops at each end, I still think that there is a serious problem.
A second serious problem exists in the support of the whole system's weight on a flotation system at the ends of the loop. — Preceding unsigned comment added by 97.65.82.66 (talk) 20:43, 1 September 2011 (UTC)
thread_title:  Fatal Flaw 

message: I think I got the overall concept. (It could probably be presented a lot clearer; it was not until I saw the YT video of the tabletop model that I understood how this is intended to work.) But even now a question remains: There's a payload that gets accelerated by the magnetic fields generated... but wouldn't it fly off immediately? How do you ensure it stays with the launch loop for further acceleration? -- 145.228.61.5 (talk) 14:44, 18 December 2014 (UTC)
thread_title:  I think I got it, but... 

message: The article implies $30 billion would provide a system sending 6 million tons per year of cargo to 8000 m/s over 2000 km of distance. For perspective, phase 1 of the California High-Speed Rail system is to send up to tens of millions of 0.1-ton passengers annually over a comparable to lesser distance, at literally about 0.5% to 1% of the speed ($68 billion cost).
$10 billion is predicted to cover building a version 2000 kilometers long and 80 kilometers high with 14000 m/s internal velocity. For perspective, that would be 100 times taller than the tallest ($1.5 billion) skyscraper in the world today even without getting into the length.
If so, there would probably be some smaller-scale, lower-velocity implementation practical as a relatively low-cost precursor to the full-scale launch loop, worthwhile in some more terrestrial application (unmanned cargo, or tourism, or high-altitude platforms, or something).
That is if its cost estimates and other assumptions are valid.
But are they valid?
Civil engineering builds things thousands of kilometers long occasionally, like the interstate highway system.  Yet I know of no examples of any civil or mechanical engineering project of comparable scale ever expecting the level of perfection required for the launch loop.  The trans-Alaska oil pipeline sometimes gets shot up with bullet holes by random people, but it is comparatively readily patchable and restorable.
If a launch loop ever has a moment of physical rotor-sheath contact at any point anywhere along its multi-million-meter length, friction at 14000 m/s is going to turn the contact point into sheer plasma.
The launch loop is like the ultimate single point of failure system imaginable, because, as soon as part of the rotor gets broken (vaporized), the section next to its gets knocked out of alignment and blows up too, blowing up the part next to it, and so on.  At 14000 m/s, each gram of the rotor has more than 20 times as much energy content as its mass in TNT high explosive.
One terrorist with a hand grenade or just a rifle with armor-piercing ammo could blow the whole thing sky-high, if random flexing & bending from wind gusts or something else didn't do it first (anything of a few-centimeters diameter having a low area moment of inertia relative to its millions-of-times-greater length).  Even terrorism has exceptional odds, as it would not be a target chosen by mere happenstance but rather the single most expensive item in the world relative to vulnerability.
The launch loop seems like the kind of ideal which may appeal to physicists and electrical engineers, not so much to civil or mechanical engineers with hands-on experience.
I'll grant that it is creative.  But practical?  The cost figures may be overrated, if really getting into nitty-gritty details like how low tolerances drive up costs.  In fact, low tolerances and a need for everything to be perfect the first time are in large part exactly what cause much of the extreme costs in current spacecraft; it is not the rocket launch fuel or raw materials, both relatively minuscule (closer to cents than thousands of dollars per pound). 
I wonder how many people really think this is more doable than other rocket and/or non-rocket spacelaunch methods for reducing costs.  — Preceding unsigned comment added by 68.12.48.19 (talk) 09:56, 18 October 2015 (UTC)
thread_title:  Economics, reliability, and plausibility: 

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thread_title:  External links modified 

message: "As the rotor speed increases, it curves to form an arc." This line is given as if this statement is obvious and needs no further explanation. Is it just me who is too dumb to know this obvious fact or must the article be much clearer about what exactly causes the structure to form an arc?  — Preceding unsigned comment added by 213.164.76.76 (talk) 11:18, 1 March 2018 (UTC)
thread_title:  Ability to stay aloft