Actually, when you have one in place, building a second space elevator is a lot cheaper. For the cost of a year of the Iraq War, you could probably build two or three dozen elevators, and the Earth would begin to look like a pincushion. It would probably be cheaper to go to geosynchronous orbit for your vacation than to go to Disneyland.
The first mouse I ever used was the first mouse that ever was, while visiting Doug Englebart in 1967 or 1968. I've always felt that it was a real mistake that we didn't also pick up his five-key chord keyboard for the left hand. With the three buttons on the mouse, you could type ASCII without lifting your hands. My second mouse was on an ALTO, serial #35, at Xerox.
Years later I tried to combine the mouse and chord keyboard by fastening a thing called a Write-hander to a mouse with duct tape. Didn't really work out
Hey, I have the complete source code for HASP, the Houston Automatic Spooling Processor. It controlled card reading and printing for IBM System/360 mainframes. It's all in well-written but sparsely-commented Assembler, some of which I myself wrote. All on a little gray 9-track distribution tape that I'm sure I can get copied back to punch cards.
I've seen descriptions of a half-dozen of these solar-system models, here and abroad. It's time to go to the next level, a scale model of the Milky Way galaxy. All we need is a basketball painted black for the center and a hundred million LEDs.
It might be clear to you because 1) you wrote it and 2) you are so proficent in the language that, to you, it reads like plain English
As a general rule, your comment is right on. However, I've been teaching programming and documentation for some 35 years and am very much aware of the phenomenon of "internalization" where you become so familiar with things in a system that it never even occurs to you to say them. I'm also much aware that levels of language proficiency can vary. In fact, I've several times written systems that I knew at some time in the future would be converted to another language, and hence had to assume that those doing the conversion would be relatively more proficient in the new language and less in the one I was writing.
Once when I was at Prime, Bob Frankston (of VisiCalc fame) stood up in front of us and explained that his code was so well written that it didn't need comments. I thought at the time that he was being extremely arrogant, and later, when I had to do something with his code, realized that he was also extremely wrong. My comment sounded like that kind of attitude, and for that I apologize.
My intent is that a person who doesn't know Ada at all, who has had maybe a single Pascal course (and who speaks English), will be able to understand my programs because of the choice of names, structures, and constructs. Ada is the only language I know where I have a prayer of accomplishing that.
I haven't used ADA, but I understand that it is somewhat designed for self-documenting code, and that as a result you are hemmed in on all sides by language rules.
Ada allows you to write what your program does as code. Most other languages make you kind of sneak up sideways on what you want the program to do, tricking the language into doing your desire. Then you have to add comments to say what it is you really wanted. I write quite a few comments in programs to remind myself (and in some circumstances others) what the program does. In Ada, I'll write the code, look at it, realize that it says what it does, and not need to write comments. My best code has no comments, and no need for them. (Except for hypertext pointers to design and requirements documents.)
I don't understand about the "hemmed in on all sides by language rules." Ada has fewer rules than, for example, Java. That is, the syntax and semantics can be expressed in significantly fewer definition constructs (BNF, VDL, whatever). For me, moving back to Ada after a stint programming in Java or C++ is like coming out of a dark and stuffy room into a nice spring afternoon.
Python was designed by a guy who is both a computer geek and a math geek.
So was APL. Ever seen APL? It's essentially encrypted at the source.
He also wrote a book back in the early 80's called The Big U. An unbelievable stinker; if you can get your hands on a copy, buy it and burn it. Imagine a combination of the bad parts of PCU and Animal House written by Stephenson while badly hung over.
1. How much would a space elevator weight ? The CNT elevator will mass (not weigh) about 40x its payload. The initial ribbon, unreeled from GEO, will be about 40,000 kg. Once it's down, climbers the size of small cars will climb up it from the ground, adding another layer of nanotubes as they climb. About 220 such will bring it to 800 tons and a capacity of 20 tons.
2. would it weight enough to affect the earth's rotation by altering the center of gravity ? Yes. We'll all be thrown off into space. Buy duct tape and oxygen.
By 2018 we'll almost certainly be able to use a Space Elevator for launch and return. It will be lifting 5 ton loads every couple of days for about $5 million each. We could use ten to twenty lifts to get 50-100 tons of vehicle, supplies, and crew up to GEO, assemble it there, and carry it out (down) to the 70-80,000 km level. (Fortunately, cargos outward bound from GEO can be much more massive, since the forces (centripetal and gravity) are much less.) All it has to do is let go at the right time and it will be slung out to Mars.
We'll be good at strong, reliable carbon nanotube cables by then, so the craft can be in two parts that are spun on a cable for (pseudo-) gravity; no worries about low gravity health effects. At Mars they will have to use ordinary rockets to go into orbit, land, and come back, but we can afford to devote a fair amount of our launch mass to them. Back at Earth orbit they'll have to rendezvous with the Elevator station at GEO, and then can ride a lifter down to the surface in comfort.
It might be interesting to spend some time designing a mission based on this assumption. What orbits are available from the elevator? Can they use the cable they take with them for rotovator-style landing and takeoff at Mars? Can you take a small nuke for power? Etc.
It's an alternating current (AC) field, probably at a fairly high frequency (30 KHz or so). His watch will just vibrate a tiny bit, completely unperceptable.
Stephenson wouldn't make that kind of mistake, even if he was wrong about the meaning of BIOS and about the existance of showcrashes.
In Cryptonomicon, Stephenson suggests the possibility of wiring a doorway to wipe any magnetic disks carried through them. You would wrap many hundreds of turns of wire around the frame (and under the threshold) and run A/C through them to create an electromagnetic field that would demagnitize the disk. I suppose you'd have to have the PC in a plastic case or no case and I don't know how far away from the doorway you'd need to keep it. (Heck, I'm not at all sure it would work at all; he's writing fiction, after all.)
Let's see, doorway wipes the disk if it's taken out, server software wipes the disk if anyone plugs a monitor or keyboard into it, encryption key generated automatically and stored on an RFID chip in a false tooth that's destroyed when you bite down hard... I think you can probably keep your data secret.
I've read your posts, here and elsewhere. I've had no argument with them, but nothing to say either. (Geoffrey Landis wrote a paper on the idea, seemed to agree with you.) I just don't think it's as good an idea as the Space Elevator if and only if we can do carbon nanotube ribbons with the necessary strength. If space elevators work, towers won't be needed or useful.
I don't have a PhD in Physics, though my advisor at Brown has a Nobel in it. I switched to computers junior year.
I've suggested using the very powerful lasers that will power the lifters to ionize columns of air around the ribbon and give the approaching stormclouds a discharge path to ground. It would also be possible to send conductive cables up into the clouds with sounding rockets, balloons, or special lifters on the ribbon to discharge the clouds. This will be necessary once a year or so because of the very low frequency of lightning storms in the area where the first elevator will be located.
Note, too, that a lightning strike would only sever the ribbon very near the bottom, no more than 30-50 km up. That's a very low impact accident; the rest of the ribbon will remain in place or drift higher and to the east over a period of days. We can just move part of the counterweight a bit further out and the severed end will come back down to the surface and can be re-attached.
It's also important to note that there will be several ribbons very quickly, and many ribbons over time; a single one being cut won't be a big deal.
I haven't seen anything about the effect this would have on the Earths rotation.
Yeah, that's a concern. If we build a thousand elevators (all around the Equator), each with a capacity of a thousand tons (the largest anticipated) and run them at maximum load for approximately the current age of the universe, it will slow the Earth's rotation by a second. We'll all have to adjust our clocks.
That proposal is actually the same text as on the HighLift site. I just put it into slightly flashier HTML.
The revised, second-phase report, much advanced over the first, should appear Any Day Now. Just waiting for NASA approval. There's also a book that expands on the idea.
The web server was having troubles late last night, so slashdotting only provided the final straw. We'll be back.
Scientific American did that in their Amateur Scientist section about 45 years ago. The WWV receiver used tubes, but they had two fingertip-sized transistors driving the electromagnet. I considered building one for my junior-high science fair, but built a four flip-flop "computer" instead. Eight transistors, cost me about 5 bucks each. That was about a day's worth of my father's income.
I don't entirely understand what "standard" means in these cases. When we made Ada 82 an ECMA and ISO standard, lo these many years ago, we created a massive validation suite of many thousands of test programs and their expected results. Validating a single version of a compiler on a single host and a single target took hundreds of man-hours to run the tests, analyze the results, and argue about their validity. A validated Ada compiler was a big deal, you knew for certain that it would compile and run your program exactly the same way that other validated compilers would. (Validation included the run-time environment targetted by the compiler.)
I don't believe that these new languages, things like C++ and C#, have anything like that; I haven't found any mention of validation suites or even the concept of a validated compiler. Apparently the vendor just claims to be conformant, maybe runs a few dozen tests. Why would anyone waste their time coding to a "standard" like that, with no reason to believe that their code would work on any target other than the one they developed it on?
Sure, developing the Ada Validation Suite was a big deal, took many man-decades of effort by some very smart people. But the result was that it saved many times as much work by all the grunt programmers who used the language. It must be incredibly frustrating to code in C# and C++, let alone a completely unstandardized language like Java.
Newton is at rest, and will tend to remain at rest. The increase in kinetic energy of a climbing mass is taken from the kinetic energy of the rotation of the Earth, slowing it by an amount proportional to the ratio of the mass of the climber to the mass of the Earth.
I can't argue with your second point, because I don't understand it. There is no orbital plane change. It doesn't matter that the Earth is inclined by 23 degrees to the plane of its orbit around the sun. All those satellites that are up there now manage to stay up without "big rocket engines." They don't need fuel, and neither will the Space Elevator.
Re:Biggest hurdles to actually building one...
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The Space Elevator
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· Score: 1
Why would you need nanotubes that long? The fibers in a rope are only a few inches long, no matter how long the rope is. Nanotubes are molecules, about one nanometer in diameter. Many millions of them will go to make up a single "fiber" of the ribbon.
The first elevator, with a capacity of 20,000 kg (20 tons) will weigh about 800,000 kg (800 tons). That's rather less than 100 trillion tons. If it snapped near the top, and somehow fell on NYC, it would be substantially less disruptive than the falling paper from a ticker-tape parade. The great majority would burn up in the atmosphere (making carbon dioxide) and perhaps as much as 5,000 kg would reach the ground.
Your analysis is flawed. When a climber is going up, and thereby gaining angular momentum, it causes the entire elevator to lean slightly to the east. This pulls back on the Earth, slowing its rotation by an amount proportional to the ratio between the mass of the climber and the mass of the Earth. When the climber stops climbing, the elevator returns to its full upright and locked position as a result of the centripetal acceleration acting on the counterweight.
The counterweight is above geosynchronous orbit. The center of mass of the entire elevator is at GEO. The counterweight is small relative to the mass of the cable, several tens of tons where the cable masses several hundreds of tons. When there is nothing climbing the elevator, there will be a tension on the anchor approximately equal to the capacity of the elevator -- about 20,000 kg for the 800,000 kg ribbon.
Nah. Even if it's all the way out at the end, at 100,000 km, such a station would only feel 0.05 G. And it would be a very dangerous place: anyone going outside could accidentally let go, not noticing because gravity is so tiny, and be slung out to Jupiter. It would be very difficult to rescue this poor unfortunate before they vanish into the distance.
On the other hand, such a station is well outside the van Allan belts, so radiation is less of a problem than it is on the ISS now.
The climbers certainly are not going to "accelerate at 1 g" or anything like that. They will start out very slowly, probably less than 50 km/hr, and gradually pick up speed after they leave the atmosphere and as gravity decreases. (Gravity is down to 1/2 g just 2600 km up.) Top speed will be in the range of 200 km/hr.
For some reason, this note and the replies to it seem to assume that everything has to travel 50,000 miles. In fact, the geostationary point (where gravity drops to zero) is only 21,000 miles (36,000 km) up and that's where most of the action will be. The main reason to go beyond GEO is to be slung to another planet, something that will happen relatively rarely. The normal estimate for trip time to GEO is about a week.
There's very little real need for speed. Cargo doesn't tend to be in a hurry and people can take along a couple of books and videos.
Sorry, can't do a loop. The ribbon just isn't strong enough to hold itself up, so it has to be tapered from geosynchronous orbit down to the surface. It will be about 2.5 times as large (cross-section) at GEO. Obviously you can't do a moving loop that is always tapered that way.
It has been suggested that we could do multiple loops, each a bit thicker than the one below it, to get the same effect. The mechanism that moves energy and payloads from one loop to the next hasn't been worked out yet. Climbers will have to have large rollers and belts in contact with the ribbon and will have to grab it very, very hard, but this still is probably the better engineering solution.
Slashdot Mirror
Actually, when you have one in place, building a second space elevator is a lot cheaper. For the cost of a year of the Iraq War, you could probably build two or three dozen elevators, and the Earth would begin to look like a pincushion. It would probably be cheaper to go to geosynchronous orbit for your vacation than to go to Disneyland.
The first mouse I ever used was the first mouse that ever was, while visiting Doug Englebart in 1967 or 1968. I've always felt that it was a real mistake that we didn't also pick up his five-key chord keyboard for the left hand. With the three buttons on the mouse, you could type ASCII without lifting your hands. My second mouse was on an ALTO, serial #35, at Xerox.
Years later I tried to combine the mouse and chord keyboard by fastening a thing called a Write-hander to a mouse with duct tape. Didn't really work out
Hey, I have the complete source code for HASP, the Houston Automatic Spooling Processor. It controlled card reading and printing for IBM System/360 mainframes. It's all in well-written but sparsely-commented Assembler, some of which I myself wrote. All on a little gray 9-track distribution tape that I'm sure I can get copied back to punch cards.
What's my legal situation here?
I've seen descriptions of a half-dozen of these solar-system models, here and abroad. It's time to go to the next level, a scale model of the Milky Way galaxy. All we need is a basketball painted black for the center and a hundred million LEDs.
Great project for the next Burning Man.
As a general rule, your comment is right on. However, I've been teaching programming and documentation for some 35 years and am very much aware of the phenomenon of "internalization" where you become so familiar with things in a system that it never even occurs to you to say them. I'm also much aware that levels of language proficiency can vary. In fact, I've several times written systems that I knew at some time in the future would be converted to another language, and hence had to assume that those doing the conversion would be relatively more proficient in the new language and less in the one I was writing.
Once when I was at Prime, Bob Frankston (of VisiCalc fame) stood up in front of us and explained that his code was so well written that it didn't need comments. I thought at the time that he was being extremely arrogant, and later, when I had to do something with his code, realized that he was also extremely wrong. My comment sounded like that kind of attitude, and for that I apologize.
My intent is that a person who doesn't know Ada at all, who has had maybe a single Pascal course (and who speaks English), will be able to understand my programs because of the choice of names, structures, and constructs. Ada is the only language I know where I have a prayer of accomplishing that.
Ada allows you to write what your program does as code. Most other languages make you kind of sneak up sideways on what you want the program to do, tricking the language into doing your desire. Then you have to add comments to say what it is you really wanted. I write quite a few comments in programs to remind myself (and in some circumstances others) what the program does. In Ada, I'll write the code, look at it, realize that it says what it does, and not need to write comments. My best code has no comments, and no need for them. (Except for hypertext pointers to design and requirements documents.)
I don't understand about the "hemmed in on all sides by language rules." Ada has fewer rules than, for example, Java. That is, the syntax and semantics can be expressed in significantly fewer definition constructs (BNF, VDL, whatever). For me, moving back to Ada after a stint programming in Java or C++ is like coming out of a dark and stuffy room into a nice spring afternoon.
Python was designed by a guy who is both a computer geek and a math geek.
So was APL. Ever seen APL? It's essentially encrypted at the source.
He also wrote a book back in the early 80's called The Big U. An unbelievable stinker; if you can get your hands on a copy, buy it and burn it. Imagine a combination of the bad parts of PCU and Animal House written by Stephenson while badly hung over.
and it's just as likely that DVDs will be replaced entirely by VoD.
(Don't tell me that "video killed the radio star.")
1. How much would a space elevator weight ?
The CNT elevator will mass (not weigh) about 40x its payload. The initial ribbon, unreeled from GEO, will be about 40,000 kg. Once it's down, climbers the size of small cars will climb up it from the ground, adding another layer of nanotubes as they climb. About 220 such will bring it to 800 tons and a capacity of 20 tons.
2. would it weight enough to affect the earth's rotation by altering the center of gravity ?
Yes. We'll all be thrown off into space. Buy duct tape and oxygen.
We'll be good at strong, reliable carbon nanotube cables by then, so the craft can be in two parts that are spun on a cable for (pseudo-) gravity; no worries about low gravity health effects. At Mars they will have to use ordinary rockets to go into orbit, land, and come back, but we can afford to devote a fair amount of our launch mass to them. Back at Earth orbit they'll have to rendezvous with the Elevator station at GEO, and then can ride a lifter down to the surface in comfort.
It might be interesting to spend some time designing a mission based on this assumption. What orbits are available from the elevator? Can they use the cable they take with them for rotovator-style landing and takeoff at Mars? Can you take a small nuke for power? Etc.
Stephenson wouldn't make that kind of mistake, even if he was wrong about the meaning of BIOS and about the existance of showcrashes.
Let's see, doorway wipes the disk if it's taken out, server software wipes the disk if anyone plugs a monitor or keyboard into it, encryption key generated automatically and stored on an RFID chip in a false tooth that's destroyed when you bite down hard ... I think you can probably keep your data secret.
I don't have a PhD in Physics, though my advisor at Brown has a Nobel in it. I switched to computers junior year.
I've suggested using the very powerful lasers that will power the lifters to ionize columns of air around the ribbon and give the approaching stormclouds a discharge path to ground. It would also be possible to send conductive cables up into the clouds with sounding rockets, balloons, or special lifters on the ribbon to discharge the clouds. This will be necessary once a year or so because of the very low frequency of lightning storms in the area where the first elevator will be located.
Note, too, that a lightning strike would only sever the ribbon very near the bottom, no more than 30-50 km up. That's a very low impact accident; the rest of the ribbon will remain in place or drift higher and to the east over a period of days. We can just move part of the counterweight a bit further out and the severed end will come back down to the surface and can be re-attached.
It's also important to note that there will be several ribbons very quickly, and many ribbons over time; a single one being cut won't be a big deal.
Yeah, that's a concern. If we build a thousand elevators (all around the Equator), each with a capacity of a thousand tons (the largest anticipated) and run them at maximum load for approximately the current age of the universe, it will slow the Earth's rotation by a second. We'll all have to adjust our clocks.
The revised, second-phase report, much advanced over the first, should appear Any Day Now. Just waiting for NASA approval. There's also a book that expands on the idea.
The web server was having troubles late last night, so slashdotting only provided the final straw. We'll be back.
Scientific American did that in their Amateur Scientist section about 45 years ago. The WWV receiver used tubes, but they had two fingertip-sized transistors driving the electromagnet. I considered building one for my junior-high science fair, but built a four flip-flop "computer" instead. Eight transistors, cost me about 5 bucks each. That was about a day's worth of my father's income.
I don't believe that these new languages, things like C++ and C#, have anything like that; I haven't found any mention of validation suites or even the concept of a validated compiler. Apparently the vendor just claims to be conformant, maybe runs a few dozen tests. Why would anyone waste their time coding to a "standard" like that, with no reason to believe that their code would work on any target other than the one they developed it on?
Sure, developing the Ada Validation Suite was a big deal, took many man-decades of effort by some very smart people. But the result was that it saved many times as much work by all the grunt programmers who used the language. It must be incredibly frustrating to code in C# and C++, let alone a completely unstandardized language like Java.
Newton is at rest, and will tend to remain at rest. The increase in kinetic energy of a climbing mass is taken from the kinetic energy of the rotation of the Earth, slowing it by an amount proportional to the ratio of the mass of the climber to the mass of the Earth.
I can't argue with your second point, because I don't understand it. There is no orbital plane change. It doesn't matter that the Earth is inclined by 23 degrees to the plane of its orbit around the sun. All those satellites that are up there now manage to stay up without "big rocket engines." They don't need fuel, and neither will the Space Elevator.
Why would you need nanotubes that long? The fibers in a rope are only a few inches long, no matter how long the rope is. Nanotubes are molecules, about one nanometer in diameter. Many millions of them will go to make up a single "fiber" of the ribbon.
The first elevator, with a capacity of 20,000 kg (20 tons) will weigh about 800,000 kg (800 tons). That's rather less than 100 trillion tons. If it snapped near the top, and somehow fell on NYC, it would be substantially less disruptive than the falling paper from a ticker-tape parade. The great majority would burn up in the atmosphere (making carbon dioxide) and perhaps as much as 5,000 kg would reach the ground.
Your analysis is flawed. When a climber is going up, and thereby gaining angular momentum, it causes the entire elevator to lean slightly to the east. This pulls back on the Earth, slowing its rotation by an amount proportional to the ratio between the mass of the climber and the mass of the Earth. When the climber stops climbing, the elevator returns to its full upright and locked position as a result of the centripetal acceleration acting on the counterweight.
The counterweight is above geosynchronous orbit. The center of mass of the entire elevator is at GEO. The counterweight is small relative to the mass of the cable, several tens of tons where the cable masses several hundreds of tons. When there is nothing climbing the elevator, there will be a tension on the anchor approximately equal to the capacity of the elevator -- about 20,000 kg for the 800,000 kg ribbon.
Nah. Even if it's all the way out at the end, at 100,000 km, such a station would only feel 0.05 G. And it would be a very dangerous place: anyone going outside could accidentally let go, not noticing because gravity is so tiny, and be slung out to Jupiter. It would be very difficult to rescue this poor unfortunate before they vanish into the distance.
On the other hand, such a station is well outside the van Allan belts, so radiation is less of a problem than it is on the ISS now.
The climbers certainly are not going to "accelerate at 1 g" or anything like that. They will start out very slowly, probably less than 50 km/hr, and gradually pick up speed after they leave the atmosphere and as gravity decreases. (Gravity is down to 1/2 g just 2600 km up.) Top speed will be in the range of 200 km/hr.
For some reason, this note and the replies to it seem to assume that everything has to travel 50,000 miles. In fact, the geostationary point (where gravity drops to zero) is only 21,000 miles (36,000 km) up and that's where most of the action will be. The main reason to go beyond GEO is to be slung to another planet, something that will happen relatively rarely. The normal estimate for trip time to GEO is about a week.
There's very little real need for speed. Cargo doesn't tend to be in a hurry and people can take along a couple of books and videos.
Sorry, can't do a loop. The ribbon just isn't strong enough to hold itself up, so it has to be tapered from geosynchronous orbit down to the surface. It will be about 2.5 times as large (cross-section) at GEO. Obviously you can't do a moving loop that is always tapered that way.
It has been suggested that we could do multiple loops, each a bit thicker than the one below it, to get the same effect. The mechanism that moves energy and payloads from one loop to the next hasn't been worked out yet. Climbers will have to have large rollers and belts in contact with the ribbon and will have to grab it very, very hard, but this still is probably the better engineering solution.