![]() | This article is rated Start-class on Wikipedia's content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||
|
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)
Updated KitemanSA's original query to match the current phrasing of the article and made two grammar fixes. Also, found a reference to KitemanSA's 'quantity strength' and a table of common materials with data to calculate their 'quantity strength' at http://www.engineeringtoolbox.com/engineering/?q=σ%2Fρ&sourceid=Mozilla-searchg-materials-properties-d_1225.html which points to what KitemanSA was discussing.
K7aay (talk) 05:44, 3 January 2010 (UTC)
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)
'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)
Still unclear 18 months later... I just read this article and had a real tough time making any sense of the intro or diagram. Both need to be redone IMHO. Halfway thru the body of the article I began to get a glimmer of what it is talking about but I'm not sure my interpretation is right so someone who is familiar with it might take another shot at an intro paragraph. Is this belt moving faster than escape velocity? And the cables hold it down? Remember this is for people who don't already know the subject matter. 68.110.104.80 (talk) 18:56, 1 October 2009 (UTC)
No, I don't get it either, the article states that "A launch loop would be held up at this altitude by momentum of the belt as it circulates around the structure" but it doesn't say what the 'belt' is nor what is referred to by the 'structure'. From the explanations on this page I guess that what is talked about is the momentum of a giant cable held within the loop holding the loop in orbit, but this is only a guess. Can anyone clarify - what is the 'belt', what is the 'structure', and where does the momentum come from? How is this thing held at such a high altitude? FOARP (talk) 10:15, 2 May 2010 (UTC)
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.
How exactly does it radiate excess heat? Through the casing when it enters the ocean at the ends?
What sort of materials / engineering is required to lift something 80km to hop on the track?
How does something detach from it at the end? Rockets, some sort of lifting body design, the fact that the loop drops off, magnetic forces, or some combination?
Finally, I know this question might be harder to answer, but how do the $/kg numbers change if the launch loop isn't used to capacity? I suppose this would be easy to calculate if the power to run it didn't vary much if it was being used to launch all the time as opposed to running without a load, but I doubt this is the case.
Sorry if these questions are uninformed or anything, and if anyone can answer them I'd be appreciative. 67.142.130.19 (talk) 17:29, 19 May 2008 (UTC)
PS: How exactly is the rotor envisioned to be constructed? Is it a monolithic, bendable, iron "pipe" or segmented with some sort of joint every few meters? 72.171.0.139 (talk) 01:06, 20 May 2008 (UTC)
Thanks, that made it a lot clearer for me (along with some reading I did on other articles). I wonder why a traditional space elevator is the focus of all the buzz and research when this concept is more plausible, buildable, and is economically cheaper? 72.171.0.139 (talk) 01:02, 20 May 2008 (UTC)
Thanks for answering these questions. It cleared things up for me also. My question: What are the latitude limits for the launch loop? --173.71.223.237 (talk) 16:22, 17 January 2009 (UTC)
Why not add variable wing magnetically accelerated uavs for dynamical vibrational control, lift, air break, turn and physical strenght off the vacuum sheath- nimb777 04:39, 20 July 2014 (UTC)
I think Wolfkeeper did a great job of summarizing the idea - more details at [1], 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)
Keith Lofstrom again: I can't comment on the appropriateness or the tone of the article relative to Wikipedia standards. If the article needs rewriting for conformance, I hope someone who understands those standards does so. Regards feasibility, obviously Launch Loop is speculation. The same is true for single-stage-to-orbit, mass drivers, macroscale carbon nanotubes, superstring theory, and the Rapture. "That big a mass" or "that tall an elevator" questions are answered by material limits, physics/mechanics, and stability, not by untrained intuition and precedent. Obviously this pushes beyond the current state of the art, but humans have been doing that for all of our history.
Over the last century, or so, we have gotten very good at analyzing models of stuff before we build it, so the steps are getting larger, typically constrained by economics or material limits, not by incremental scaling. Non-mathematically-inclined people have a hard time following that. We have gone far past the ability of intuition to keep up. In my own field of integrated circuits, intuition stopped being useful decades ago. Billion transistor microprocessors can't possibly work ... yet they do. Intel invests billions of dollars in fabs for processors that are still vague descriptions in memos. Like Boeing and the 787 Dreamliner, they bet the company on what their models tell them. It will be a while before Launch Loop gets to those funding levels, but the limits are size of market and a scalable evolutionary path, not physical laws that mysteriously fail above some intuitive threshold.
Previous versions of the Wikipedia article contained speculations about priority, and who inspired who. Those have been removed, thankfully. A lot of people worked on dynamic structure concepts in the late 1970's and 1980's, inspired by various previous concepts, but mostly by the math. I was inspired by Arthur Clarke's Fountains of Paradise, and traded ideas with Roger Arnold and Ken Brakke and Paul Birch and Robert Forward, as well as many others with great ideas but no publications. Others, like John Knapman and Alexander Bolonkin, thought up ideas like these later on, independently. I don't see those as derivative, but as confirmation - there are some fruitful ideas to explore here, and imaginative people with a grounding in Newtonian physics will keep stumbling across them. I updated my own publications list at http://wiki.keithl.com/index.cgi?PapersPublications - I can forward copies of some of those publications to serious researchers or Wikipedia page re-writers. If you want some aspect of that published material explained, perhaps to clarify a rewrite, please contact me. KeithLofstrom (talk) 04:50, 22 December 2009 (UTC)
(these were completely unreferenced and unformatted)
10. Centrifugal Keeper for Space Stations and Satellites, by A. Bolonkin, JBIS, Vol.56, No. 9/10, 2003, p. 314-327. Author offered and researched the rotating cable which launches and keeps the moveless space station and satellites. Four projects are computed. 11. Kinetic Space Towers and Launchers, by A. Bolonkin, JBIS, Vol. 57, No.1/2, 2004, p.33-39. Author offered and researched new method for access to outer space. A cable stands up vertically and pulls up its payload to space. Five projects are computed. 12. “Non-Rocket Space Rope Launcher for People”, by A.Bolonkin. IAC-02-V.P.06, 53rd International Astronautical Congress, The World Space Congress – 2002, 10–19 Oct 2002, Houston, Texas, USA. 13. “Non-Rocket Missile Rope Launcher”, IAC-02-IAA.S.P.14, 53rd International Astronautical Congress, The World Space Congress – 2002, 10–19 Oct 2002, Houston, Texas, USA. 14. “Inexpensive Cable Space Launcher of High Capability”, IAC-02-V.P.07, 53rd International Astronautical Congress, The World Space Congress – 2002, 10–19 Oct 2002, Houston, Texas, USA.
Patents:
1. Method and Installation for Space Trip. Patent application US PTO 09/789,959 of 2/23/01.
2. Method and Installation for Space Launch, by A.Bolonkin. Patent application US PTO 09/873,985 of 6/04/01.
3. "Method for Launch and Payload Transportation at Long Distance and Installations for It", Patent Application USPTO # 09/978,507 of 10/18/01.
4. Cable Launcher. Patent application US PTO 09/974,670 of 10/11/01.
If you are going to state statistics such as launch velocity and the suchlike, you can not go without touting a few physics equations. Where is the proof this will even work? Much of the article is stated as fact, but if it is simply theory then say that at the beginnning.--MixMaestro (talk) 01:08, 5 September 2008 (UTC)
This articles covers a lot things, but (from my reading), fails to mention how the cable way would either reach 80km up in the air, or be maintained there. —Sladen (talk) 13:40, 13 October 2008 (UTC)
The question i have is before anything is ever put to use, when the cable is first constructed on the ground, how to the lift it into the air for the fist time. Surly no crane(s) or helicopter(s) could accomplish this. --Alex at kms (talk) 02:35, 15 February 2011 (UTC)
"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)
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)
The article claims "the magnetic suspension system would be highly redundant, with failures of small sections having essentially no effect at all." I don't see how this is possible. If the sheath breaks somewhere in the middle (say an airplane hits it), wouldn't the belt fly out of the broken sheath and the whole loop come falling down in a matter of minutes? And wouldn't there be a quick loss of vacuum accompanied by intense heating due to increased friction if there was a hole in any part of the sheath? Halberdo (talk) 06:07, 28 September 2009 (UTC)
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)
I'm gonna have to agree with Heathhunnicutt. As I was reading this article it felt as though one user has been thinking this idea up and adding these ideas as they went along. I'm not saying it's how it happened, but that's how it feels. At the very least we need several people to help rewrite it. No offense Wolfkeeper, but it seems that you have written nearly this entire article. A few other sources need to contribute or we need to start cutting a lot of the content out. Barhamd (talk) 03:05, 16 December 2009 (UTC)
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)
After reading the article, the talk page and the user pages of the participants, I have removed the NPOV language tag. This appears to be a decent-quality article about one of the most feasible non-traditional space launch proposals, and it seems to be honest about its potential technical problems. The claimed advantages for this system come from respectable sources, and have not been refuted by credible sources so far as I can tell. Since the notability of the topic of the article comes from those claimed advantages, it would be inappropriate to remove mention of them. Enon (talk) 20:01, 22 April 2010 (UTC)
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)
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)
"What is not needed; •"Suggestions" without detailed analysis. 99.99% of all ideas are stupid, and if you don't have the technical capability - that is, the time and the fortitude to learn and analyze and do math and risk disappointment - then don't expect me or anyone else to provide it. •Free computer time on your home computer (or your bosses computer). If you can write an accurate simulation, wonderful, we can probably find someplace to run it. Raw cpu cycles are far less useful than a good plan for using them. •Money in small amounts. If you can locate enough money to keep a number of researchers busy for months or years, lets talk. If you want to send 20 bucks somewhere, buy a calculus book and learn how to help. Or give it to some educational charity and tell them it is from the space program - bolix up the folks that say "fix problems on Earth first". •Praise. Accomplishment is its own reward. Don't let us rest at a halfway point on empty praise. Swollen egos have destroyed more projects than any hurdles mere nature can create. •Demands for time and attention. What is sad about this is that the arrogant twits that think nothing of wasting hours of other's time will ignore this message and pester me, while the quiet thoughtful people with something useful to add will probably be scared off by this ranting. A useful yardstick might be - are you self-critical? Would you rather be anonymously right rather than be rich and famous? If your ego is small, and your capacity for self-examination is high, you may well have something to contribute."
In 5 arrogant statements I went from being profoundly interested in this project to having total disdain towards it and those involved. What a way to turn away your potential supporters! Enjoy writing documents that will one day be covered in mildew and dust and lying forgotten in cardboard boxes in the basements of old libraries. — Preceding unsigned comment added by 122.148.43.180 (talk) 05:46, 4 December 2011 (UTC)
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)
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)
Hello fellow Wikipedians,
I have just modified one external link on Launch loop. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:
When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.
This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template ((source check))
(last update: 5 June 2024).
Cheers.—InternetArchiveBot (Report bug) 11:09, 8 November 2017 (UTC)
"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)