Shades of Arthur C Clarke
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| Author | Content |
|---|---|
| Ridcully Jul 09, 2011 9:43 AM EDT |
In his science fiction book, "The Fountains of Paradise", Clarke described the space elevator. It has always intrigued me as a technique for achieving orbital status that was far more efficient compared with rockets, even if I personally considered actually building such an elevator somewhat "fanciful". But then, futuristic concepts described by Jules Verne were equally fanciful in his day but are now more or less routinely part of 21st century human activity. "Around the World in 80 Days" springs to mind as a situation in which Verne himself would be astonished at human progress. My understanding is that the main obstruction to a successful space elevator has always been the structure/strength of the cable connecting the earth to the geostationary space station but apparently cabon nanotube technology may be the solution. In any event, the forthcoming conference on space elevator research could be well worth keeping an eye on: http://spaceelevatorconference.org/default.aspx Space tourism may not be so remote after all. Where there are entrepreneurs, there will be funding. |
| number6x Jul 09, 2011 1:26 PM EDT |
A satellite in geostationary orbit is about 37,000Km or 3,700,000,000 cm (3.7 x 10^9) above the Earth. The cable for the elevator would have to be that long. If the cable had a round cross section 1 meter in radius the volume would be about 1.16 x 10^14 cm^3. If the cable had a density of about 1.4 gm per cm^3 that would be a mass of about 1.6 x 10^11 kg. Just compare that to the mass of the space shuttle at about 1 x 10^5 kg and you would see that we would either need much larger launch capability than we currently posses and we would have to have much stronger carbon nanotubes than we currently have, just for the cable to support its own weight. Developing the technology to produce the cable in space and drop it down would also require quite a few advances in space technology. Also think of the drag and tidal forces exerted on the cable. The main cargo carried to the satellite would have to be the vast quantities of fuel needed for it to correct for those and maintain position. Also carbon nanotubes do not have good cross sectional strength currently and would need that to survive the sheer forces. The largest nanotube produces so far was 18.5 cm, so we also have to develop the technology to produce them a little longer than that :) I've seen an amazing number of advances in my lifetime but I don't think we will see this in 10 years. Possibly in my son's lifetime. For a few decades, this will remain scince fiction. But hopefully it will continue to inspire work and research. |
| Jose_X Jul 09, 2011 7:53 PM EDT |
What exists in nature or human advancement that would even suggest this is possible any time soon (like within 1 century or even 2)? We do have the potential for very advanced real-time controls with advanced computers .,m,.m We had birds, gliders, and ample understanding of science to suggest that we might be able to fly fast and go straight around the world (with stops perhaps) in short time. We know how to submerge and swim so we can guess at submarines. But space elevator!!??? At least journey to the center of the earth (amid ridiculous pressure and temperature that makes our materials liquid.. never mind us) at least leaves open-ended how we get there (ie, just get there as opposed to get there in an elevator). blah blah. OK, not one to put down a challenge easily... My problem isn't in an elevator, but in maintaining an elevator that would be more efficient than a rocket periodically. I mean look at how low our buildings continue to be after centuries of slow progress to increase height. What about if we create the first stage of the elevator within very high mountains (so you are in comfortable environment the whole trip up). This seems plausible if we find adequate sites. This will get us up a "chunk" of the way. Afterwards [still thinking this is pipe dream], we can have plateaus every so high up. If we can tap into solar (or maybe nuclear fission or fusion??) to sustain those platforms.. perhaps use very light gases to hold these up. The elevator chord can also be partly supported by internal or other light gas filing. By creating many platforms, we can rest platforms not currently in use (eg, when the elevator load is between different platforms). Holding up the platforms in low air environment can be done (a) nearly as in space with advanced controls and some sort of propulsion system (a fan or shooting out air that was compressed from surroundings on an ongoing basis to control side to side movements -- here the environment itself naturally does the work of bringing a plentiful supply of air within reach of the compressors). (b) When a stage is not in use, it can rely on being held up by the light air balloon/gases. Thus with gas and propulsion it might control its height and its sideways displacement. We can even lower the weight by having the elevator cargo entity be handed off from platform to platform. Anyway, with energy from the sun for the modest needs to stabilize and with the light gases naturally holding everything up without extra energy and keeping the loads light (hand-off the elevator and keep the platforms modest distances apart so the chords and support are modest), then we might be able to go above the mountain area for maybe a few miles if we are lucky. As the surrounding atmosphere gets lighter and lighter, it's more difficult to get the air balloons to work. .. and we still have a long LONG LOOOOOOOONNNNNNNNNNNGGGGGGGG way to go to reach the stationary satellites. Good luck. I think we can even consider that a balloon ride to a high platform would be cheaper and more practical than the above platform connections. But then what? Why don't we just rely on the cheapness of being at ground zero and send up a one time rocket! I'd suggest rocket propulsion from a high platform.. since the rockets excel at the high altitude regions.. but, besides the weight of the rocket, this breaks the elevator concept. I think, however, that if we assume elevator was not intended literally but simply to suggest that people inside a compartment could be sent up.. then we have already succeeded. NASA is going to have time on its hands to experiment if they want, but we should always seek for efficiency and not to mimic science fiction writers, whom should not be expected to bat 1.000. |
| keithcu Jul 09, 2011 10:03 PM EDT |
For those who want get any of their technical questions answered, I recommend Edward's book. We can create fibers and spin them into threads like we do with cotton. We need fibers less than an inch long to do this -- anything longer doesn't work. So we have it long enough. The problem is that people aren't working on nanotube rope -- it sounds fanciful to certain people, like the Linux desktop ;-) Regards, -Keith |
| Jose_X Jul 09, 2011 11:39 PM EDT |
Keith, I just read the article (fairly quickly so missed some details). I think if you want this "moonwalk" in 7 years you should understand that the teams back then did not work to make a few wealthy investors wealthier yet. They did it for the common good and for national security. I don't think patents were there to get in the way of progress, either. Have you considered how to deal with these issues in the context of a space elevator? |
| Jose_X Jul 09, 2011 11:54 PM EDT |
I forgot to ask.. which Edwards and Edwards book are you talking about (sorry if I sound ignorant)... googling... "In 2008 the book 'Leaving the Planet by Space Elevator', by Dr. Brad Edwards and Philip Ragan.." I suppose it's that one. Looking a bit at the wikipedia article, I see that the idea is to keep the center of mass at geostat orbit. I was originally thinking of something above that orbit height since (without doing much physics analysis right now) I figured the weight towards the center of the earth would match the centripetal accel to keep the object at constant speed around the planet at that higher altitude. [This is essentially the same thing as extending a counter weight towards space.. where once you reach the final position, you effectively have a large mass out in space beyond geostat orbit. I was assuming that counterweight position would be where the actual space station and people largely reside.] Judging by the confident tone of the article, I assume the weight and tensile strength analysis has been done and people believe we are close to achieving this with nano technology... or at least for the structure to hold itself up all by itself with no added weight or jerking.(??) It might turn out that we'd get a moon station set up first and have the first elevator exist "on" the moon. Have you considered/researched whether a moon station is more feasible? [Yes, it's a complex problem with many variables and assumptions.] EDIT: Upon further thinking, while the strength and energy requirements of materials and "rocketing" on the moon are better (shorter, less pull towards moon, etc), the lack of effective atmosphere and surface body of water removes many tools like gliding and parachuting that would might be used a lot on earth. [Yes, the lack of materials on the moon is an obvious and major short-coming as well. We'd have to stock the station rather well over a large number of missions to the moon.] Well, heating up is not a major factor on return trips to moon surface (this argues in favor of moon elevator). If we could get it set up, it would be much cheaper to run. ... So moon citizens may end up with that elevator before earthlings. In large numbers, they would get to see their grey barren planet from far away before we could see ours from far away (lol). |
| Jose_X Jul 10, 2011 12:19 AM EDT |
I smile thinking of how we don't have to pay loads of money to leave the "hell" hole that is outer space in order to come live in this beautiful environment down here on the surface of the earth. We get it for free!! |
| keithcu Jul 10, 2011 1:22 AM EDT |
Man pays money to put things everywhere, why not up in space? People think of space as a source of resources and money. The motivation to do a task doesn't matter. The goal of making money in space will not hurt space progress. People can also have multiple motivations. This isn't about making money vs. serving the public good. That is a false choice as you can / should have both. That is what the free market is about, voluntary transactions. Free software is voluntary. People make money, and do good for that money. Can you read the outside world section of my book? Patents are a cost, but we can pay it. It is billions in a trillion dollar industry -- a rounding error. The problem is simply that the whole endeavor seems too far out to too many people. Even those who like the idea think it is a 20-30 year idea. Consider going to Steve Ballmer and telling him to create a Linux. How would that go, no matter all the good arguments you would make. The book is the Edwards and Westling book. The others are not technical. His book walks through every challenge. It is interesting. Yes, the science has been proven regarding carbon nanotubes. What remains is engineering. The biggest challenge is ribbon repair. So you'd need to put a bunch of people on it. |
| Jose_X Jul 10, 2011 2:50 AM EDT |
Thanks for the info and article Keith. I may not access the book now and may forget about it, but thanks for that. http://www.amazon.com/Space-Elevator-Earth-Space-Transportat... I focused on the length (7 years) for reaching the moon. Money is not sufficient motivator. Most who work on this care about the challenge itself, however, regardless of money (true). But the implied threats during the 60s cold war adds to the focus. Of course (OTOH), we have more people now able to cooperate on this project. Any patent almost exclusive on information (software patents) accessible (otherwise) cheaply is a problem. Linux was not built by people asking for permission or able to pay a few billion dollars. NASA did not have managers and lawyers holding them down too much, I suspect. And anyone seeking monopoly control or squeezing so much to disrupt a particular research group (and this can happen in other ways not related to patent threats) is an impediment, potentially a huge impediment because of how broad patents are (eg, the very low inventiveness bar). Some mega patent holders actually do like to buy up their exclusive teams and play aggressive with others. .. BTW, if "we can pay" for the cost of patents, then that would calm me if in fact someone did pay out those billions and allowed the rest of the world to use and never have to worry about patents again (as concerns this project), but we know very well that is not how patents and the patent business works. [I wrote and incomplete writeup in favor of patent FAIR USE that would make most software patents, independent creations, research, and small commercial activities largely immune to patent litigation http://tofreeornottofree.com/SCOTUS_Amicus_Curiae_Brief__i4i... ] |
| keithcu Jul 10, 2011 6:55 AM EDT |
Software patents will not get in the way of the space elevator. Money is insufficient to building a space elevator because it only allows you get the people and the equipment. You still have to believe in the idea, and make a plan. |
| dinotrac Jul 10, 2011 6:54 PM EDT |
Keith, I'm sorry, but I being to understand some of Microsoft's problems a little better when I read this:Quoting: With a 1,000 person team, 1 man-year of work is accomplished every 2 hours. With 100,000, 1 man-year takes 1 minute and 12 seconds. Work is generally fungible so a 20 year project could use more people and go faster. Long before you ever thought you could actually multiply people that way, Fred Brooks had applied a better and more thoughtful analysis in The Mythical Man-Month. People are not fungible, and projects are not infinitely divisible. Windows Vista was not the only large-scale project to prove the Brooks's wisdom. Wasn't the first, and won't be the last. Ample resources are great. Smart and focused management is great. However, every task has a point at which more resources slow it down and make it worse. |
| keithcu Jul 10, 2011 11:17 PM EDT |
Hi Dinotrac; I read Brooks' book many years ago. Brooks' point was about ramp-up time. However, in a 7 year project, there is plenty of time for ramp-up. The problems with Vista had nothing to do with assigning a bunch of people to a team late. It more had to do with 20 years of accumulated backward compatibility baggage. No question that more resources slow something down at some point. However that is not a problem with 7 years. -Keith |
| dinotrac Jul 11, 2011 7:33 AM EDT |
@Keithcu - You propose a 7 year project for something whose technical feasibility is not yet demonstrated, whose architecture has not been developed, and for which an organization does not yet exist. Sounds like Fred Brooks territory to me. |
| keithcu Jul 11, 2011 9:45 AM EDT |
@Dinotrac: The Edwards and Westling book has demonstrated its technical feasibility. It has nothing to do with Fred Brooks thesis. He was talking about how bringing people to a team late doesn't help a project because they need to learn all the details of a new codebase before they can be productive. It is like learning a new spoken language -- that takes months. So while it can take months or a year to ramp someone up on a project, this is a 7 year project. And it is the year 2011 not 1975, so there is a lot more people with expertise, new technology to depend on, better tools of collaboration, etc. |
| JaseP Jul 11, 2011 10:13 AM EDT |
The bottom line is that there are four practical bars to a working space elevator: 1) Materials science, 2) Engineering those materials into a workable solution, 3) Expense of the project, when cheaper alternatives exist, and 4) Location, and all the geo-political issues that comes with it. If the sum of those issues exceeds the alternatives that work now, we will not get serious consideration of the project. Material and engineering have to advance to a point where it reduces the cost to such a low level that location and political issues become tolerable. To highlight this, just imagine a working space elevator becoming the target of terrorist activity. Until the collateral losses (loss of the elevator vehicle, a destroyed tether ripping apart nearby structures, etc.) of such an attack are low enough, it will never be built. |
| Fettoosh Jul 11, 2011 10:58 AM EDT |
Is it Led. Zeppelin (Stairway To Heaven) http://www.youtube.com/watch?v=BcL---4xQYA http://www.youtube.com/watch?v=7YZb8s7Kxa4&feature=related or is it David Bowie (Space Oddity) ! http://www.youtube.com/watch?v=rKE3FSPJu-4&NR=1 Thou shall not escape Earth but with power. So, enjoy Zeppelin' and think about Bowie's |
| dinotrac Jul 11, 2011 11:30 AM EDT |
@keithcu -- Sigh. The book was born from his experience with the development of OS/360 and trying to make up time as it fell behinds. As with any lesson, you are entitled to learn as little or as much as you please. Ditto with application of lessons learned. I suspect, however, that few people will need to develop a new mainframe OS. The book's value might just lie in one's ability to apply some or all of the lessons learned to other situations. |
| keithcu Jul 11, 2011 7:17 PM EDT |
@JaseP:
Your four challenges to the space elevator are wrong. Edwards has already researched all of the topics in his 2003 book, including terrorism. @Dinotrac: Don't sigh at me. You are the one mistaken and who doesn't respond to the points I make. I understand his thesis but disagree with its relevance to a 7 year project. As I mentioned earlier, I read the book. If I wanted to build a SE in 1 year, Brooks work would be more relevant. |
| dinotrac Jul 12, 2011 9:24 AM EDT |
@keithcu -- Didn't realize I was tasked with a point by point assignment. As such, I'm certainly not obligated to respond point by point. As to technical feasibilty, we may not be defining it the same way. However I think @JaseP summed it up perfectly well. I think of it like the electric car. Seems feasible. Already doable for certain uses, yet... that battery breakthrough we all know is just around the corner has been around the corner for the last 40 years. It could happen tomorrow or it could happen in 50 years or it could happen never. Hard to make a 7 year plan for stuff like that -- and GOSH! -- we really are back at Fred Brooks, because you end up just applying resources to solve a problem that won't be solved in 7 years, no matter what you throw at it. |
| JaseP Jul 12, 2011 12:49 PM EDT |
@keithcu Well, I'm not buying (and, God forbid, actually reading) a book just to dispute its findings,... So let's just say that research isn't reality, and leave it at that. Particularly on terrorism,... they're like cockroaches, they always find a way to survive and infest. I will never buy an intellectual argument that discounts it as a danger. A space elevator would be too tempting a target... And there are so many potential vectors of attack (air, ground/sea, underground/undersea, maintenance, cargo/passengers, etc.). And besides, Dino and I agree so RARELY, that I MUST be right!!! |
| TxtEdMacs Jul 12, 2011 1:19 PM EDT |
Quoting: [...] besides, Dino and I agree so RARELY, that I MUST be right!!! I beg to differ, anytime one agrees with dino the presumption must be that both participants are in error. Until fairly recently that was a rule you could bank on. Something akin to if it's associated with khess, skip it. Nickles, has the economy tanked that far that you can discern between discards. Get out of the trash pile I will send some aid. Will a few dimes do you? YBT |
| keithcu Jul 12, 2011 8:20 PM EDT |
@Dinotrac: The electric car is not like the space elevator, and not like Fred Brooks. Brooks: people (ramp-up learning) problem Electric car: chemistry / physics problem Space Elevator: ignorance of feasibility / lack of leadership problem @JaseP: You don't be able to dispute Brad Edwards' research. Terrorism can be easily stopped. Edwards plan puts it hundreds of miles offshore. Al Qaeda is much too primitive to attack something like that. For them high-tech is bombs in shoes. |
| Grishnakh Jul 12, 2011 9:10 PM EDT |
Patents are easily worked around: simply leave the USA out of the Space Elevator project. As for "terrorists", please get a grip. You don't see countries like Malaysia and China refusing to build skyscrapers because they're afraid a terrorist might bomb it. Protecting a SE is easy: build it in the ocean on a floating, anchored platform, and have some armed security around it. AA missile launchers and a couple patrol boats are all you need. The SE needs to be on or near the equator anyway, and there isn't much land on the equator that's politically stable. |
| JaseP Jul 13, 2011 1:07 PM EDT |
Quoting: Terrorism can be easily stopped. Edwards plan puts it hundreds of miles offshore. Al Qaeda is much too primitive to attack something like that. Yet, Somali pirates have managed to hijack commercial shipping vessels from small boats with outboard motors... Now imagine the same thing, but with scuba gear and bombs,... Just like Al Qaeda and the USS Cole... I remain unconvinced. Sorry. Don't get me wrong, a Space Elevator would be awesome. I just don't see it happening within the next 30 to 40 years. If I live long, maybe I'll see it in my 70s or 80s... |
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