Talk:Launch loop

Close-Loop Cable?

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)

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)

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)

Vacuum Sheath?

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)

unclear article

'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)

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)

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)

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)

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)

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

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)

A few questions

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)

How exactly does it radiate excess heat? Through the casing when it enters the ocean at the ends?

Just radiation through to the casing which then it turn radiates as well.- (User) WolfKeeper (Talk) 18:15, 19 May 2008 (UTC)

What sort of materials / engineering is required to lift something 80km to hop on the track?

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

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)

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?

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

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.

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)

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)

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)

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)

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)

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)

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)

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)

   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)

KeithLofstrom here, with a few comments

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)

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)

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)

Removed from the article

(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.

Why so Certain?

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 is simple. If you start off at rest, have a constant acceleration a, and a target velocity v, it is simple to find the necessary distance s to achieve v--the formula is:

$s={\frac {v^{2}}{2a}}$

We want a constant acceleration that is about 3g's, and let us go with 30 m/s2 to keep it simple. Our target velocity is about 11 km/s.

We have: $a=30{\tfrac {m}{s^{2}}}=0.03{\tfrac {km}{s^{2}}},v=11{\tfrac {km}{s}}$

$s={\frac {(11{\tfrac {km}{s}})^{2}}{2(0.03{\tfrac {km}{s^{2}}})}}={\frac {121{\tfrac {km^{2}}{s^{2}}}}{0.06{\tfrac {km}{s^{2}}}}}=2016.{\overline {6}}km$

That is pretty close to the 2000 km number put out by designers of the launch loop. Cornince (talk) 01:56, 17 December 2008 (UTC)

Altitude maintance

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)

It's carried there by the momentum of the rotor. It's a bit like a when you're watering the garden through a hose, if you put it on a straight flow setting and point it up, the water forms an arch. It's going too slowly to carry any major load, but perhaps you could imagine hanging a paper or foil wrapper on the arch or something. The launch loop works the same way, except the rotor is going ohmygod fast and it can carry a lot more weight.- (User) Wolfkeeper (Talk) 18:39, 13 October 2008 (UTC)

It would be good for the article to mention this. One other thing I'm uncertain about, these 2 towers that use the magnetic forces to keep up the launch loop, will they be 80 km high? Cornince (talk) 22:20, 16 December 2008 (UTC)

There's no towers, there's just 'elevator' cables hanging down from the docks. The docks are held up by the main launch loop cable, not the other way around.- (User) Wolfkeeper (Talk) 00:08, 17 December 2008 (UTC)

Also, it seems that this loop has varying altitudes, in that it is at certain points 80 km high, while at other points it is near ground level. The descriptions I've read don't seem to be clear on this point. Cornince (talk) 22:22, 16 December 2008 (UTC)

I'm not sure why you say that. The loop is at ground level at each end and 80 km in the middle, as the diagram shows.- (User) Wolfkeeper (Talk) 19:54, 18 December 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)

People are fond of saying it's the momentum of the rotor but no explanation of why this helps, and how the momentum lifts it. It is in fact the same mechanics that allows normal orbits. The rotor is moving along the equator at 14km/sec Running along the ground at the anchor point it will try and stay in a straight line. Since the earth curves down away from it it will carry on in a (mostly) straight line and appear from the perspective of those on the earth's surface to rise up into the air. It won't be perfectly tangential to the Earth as gravity will have an effect and cause it to arc downwards slightly but since the cable is moving at well over orbital velocity it will appear to rise into space.

Consider what would happen if you had a rail gun firing pellets at 14kmps they would travel in a (mostly) straight line but appear to rise into orbit because their momentum means they try and travel in a straight line. This is the same thing except because it is a loop what we have fired comes back again and is reused. Rufty (talk) 12:26, 13 July 2015 (UTC)

Actually having re-read the references there is another effect - at the launch station the loop is angles upwards by 5 degrees. Therefore the cable is heading skywards and the momentum of the cable means that this is providing a good chunk of the lift. Clearly this needs more explanation in the article if several people keep mis-understanding it. Sorry for adding to the confusion. Rufty (talk) 12:54, 13 July 2015 (UTC)

Elevator?

"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)

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)

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)

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)

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)

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)

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)

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)

Proof of Principle

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)

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)

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)

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)

I would say it's fractionally above technology readiness level 2.- (User) Wolfkeeper (Talk) 23:58, 16 December 2008 (UTC)

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)

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)

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)

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)

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)

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)

Well, Keith Lofstrom and Paul Birch built a small desktop model that basically worked.- (User) Wolfkeeper (Talk) 15:31, 9 March 2009 (UTC)

Source?- Cornince (talk) 08:11, 17 March 2009 (UTC)

I agree, is there a link to source material? --Qwerspam (talk) 19:20, 17 March 2009 (UTC)

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)

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)

Safety?

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)

Oh yeah, big time. That comes under the heading of 'don't do that'. Lofstrom would site it at sea to minimise these issues. You design it so it doesn't snap; with ample safety margins.- (User) Wolfkeeper (Talk) 19:26, 1 October 2009 (UTC)

Actually an airplane couldn't hit it in the middle because the middle is at far too great an altitude, 80km is about 240,000 feet, whereas aircraft fly at ~35,000 ft.

Factual article or propaganda?

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)

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)

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)

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)

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)

Neutrality

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)

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)

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

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)

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)

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)

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)

Keith Lofstrom again

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)

Fatal Flaw

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)

From the Launch Loop Website

"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 agree somewhat - the right thing to do would be to point out why certain "Suggestions" are stupid and direct people there. But that doesn't change the fact that the general idea of an Launch Loop is interesting. Don't let you stop from telling your ideas.

Here's my "view to prompt further investigation".

To let a loop float more than 80km high a lot less than first cosmic velocity (< 1/10) is needed if the loops radius is significantly smaller than earths (but still >80km). For spacecraft acceleration a straight line several 1000s of km long is necessary. To get this one could connect multiple "small" loops through a lower positioned cable C suspended under the "small" loops. C would have to deliver power for spaceship acceleration through other means than magnetic coupling though. Any serious flaws? 93.82.7.154 (talk) 13:18, 27 February 2012 (UTC)

I think I got it, but...

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)

Economics, reliability, and plausibility:

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)

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Ability to stay aloft

"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)