He got it right; you just can't READ. He says that the Fortune 500 companies have errors totaling $165000 * 9 *500 = about three-quarters of a billion. TRUE! He than says that, given that very rough estimate, the total for all US companies could be $10 billion. The estimates are questionable, but the math was done correctly.
I hope you don't create spreadsheets for your company.
there's no reason it couldn't or shouldn't be done.
Two words: radiation belts
The Apollo astronauts crossed the radiation belts in about 30 minutes, getting a dosage of about 1/2 rad. That's approximately the recommended YEARLY dosage for non-nuclear workers. Passengers on the SE would take about 90 hours to cross the belts, giving them a dosage of about 100 rads. 500 is fatal, so they'd be very, very sick and most would die prematurely. (Info from a paper by Jorgensen and Patamia at the Conference).
It would take a huge amount of shielding, many tons, to protect just a few passengers. Doable for a few astronauts, but we'll need to find a better way before tourists ride the SE.
AI has been one of the great scams of the last 40 years, one whose main purpose was to wring money out of (D)ARPA and NSF. Maybe they've finally caught on.
Minor point: you implied that gravity was in effect up to 35950 km and that centrifugal effect applied above that. In fact, both forces work on the whole length of the elevator, but gravity decreases and centrifigal force increases as you go up. At 35,950 km they are equal, and above that centrifigal force is larger.
Bob Munck (Brown '67)
I notice that the word "software" appeared exactly twice in the article. That's appropriate, because the military doesn't have the foggiest idea how to build software. I say this as someone who has worked both on the WWMCCS upgrade fiasco and on a multi-year, multi-prime-contractor, multiple-hundreds-of-millions-of-dollars program to improve the way DoD does software. We didn't; I think there's a pretty fair chance we actually made it worse.
The other thing the military doesn't do is security. They think you make your systems secure by classifying the source code. It's always a race to the bottom to find which is worse, system reliability or system security. This doesn't bode well for an attempt to build a HUGE secure, reliable network.
My prediction: they'll burn through tens of billions of dollars, chew up the careers of a large number of programmers and managers, and the whole idea will fade away around 2010 or so. One good thing; the coding cannot possibly be outsourced.
I'm appalled at the number of people on this thread who are obviously equating science fiction to Star Wars, Star Trek, and their ilk. These things are to science fiction as military music is to music. I wish we could do something like always calling movie and TV SF "Sci-Fi," but we've long since lost the battle to preserve the benign meaning of "hackers," so I guess this is a lost cause too.
Read a book, already. (One that's not based on a movie or TV show.)
It's pretty obvious one end hooks to Earth, but what do you hook the other to?
An artificial satellite in geostationary orbit,
No, no forget all that "geostationary" stuff. What holds the Space Elevator up is good old centrifugal force. Whirl a rock on the end of a string around your head: the string is held taut and the rock out at right angles to gravity by centrifugal force. In similar fashion, the Space Elevator will be whirling around so fast that it'll be held taut. Sure, it's only going around once every 24 hours, but it's really, really long.
(Yes, centrifugal force isn't real, it's virtual. It's the apparent force created on a mass under centripetal acceleration.)
That's a different situation. The Tivo software doesn't know that the channel it's recording is music, because it doesn't know anything about the incoming signal. In DirecTivo, the software is running both the recording and the channel selection function.
Just as a point of interest, DirecTiVo -- the combination of TiVo and DirecTV -- won't allow you to record the 40 or so music channels. It's probably the same irrational people. When XM does allow recording, they'll do it in such a way that they can block it for selected shows.
You didn't say when you'd want to retrieve the data or how much you'd want to spend to do so, so I made some assumptions:
Beam the data into space. When you want to retrieve it, you'll have to go catch it.
You don't want the beam waving all over the place because of the Earth's rotation, so aim it at the North Star (assuming you're in the northern hemisphere). If this activity continues for a long time, you'll have to compensate for the precession of the Earth's axis and for various smaller wobbles; I believe a correction every century or so will suffice.
Note that if the speed of light really is an absolute limit, you'll have to count on the universe being curved and wait for the data to come around again. Again, you didn't say anything to indicate that this might be a problem.
Very low. Even at the end of a 100,000 km tether, the effective gravity is -0.0538 g. Actually, centripetal acceleration due to the rotation of the Earth is -0.0574 g and Earth's gravity is 0.003596 g. You're much better off using this wonderful carbon nanotube ribbon material to connect two (or more) habitats and spin them around each other, with the whole construct orbiting near the elevator at GEO.
90 cm in width, "thinner than a piece of paper"
(actually, about 10 microns) thick. Your calculations are off by about five orders of magnitude. Reading is a skill.
In fact, one of the programs that constituted those 250K LoC was an interpreter for a language named BRUIN -- BRown University INterpreter -- that was used fairly extensively by institutions running CP-67/CMS on a 360 mod 67. It took about a hundred instructions to interpret a line of the source code, so the answer is about 2 minutes on the old mainframe or 20 ms on a modern micro. Of course, as I said the interpreter was written in assembler; that probably isn't true of PERL.
As an old microcoder, my basic inclination is to think of machine instructions as interpreted. That's even true of RISC machines, though less so. You haven't lived until you've fixed a bug by weaving a wire through a row of tiny transformers to change the microcode.
I once estimated that I had written 250,000 lines of assembly code for the IBM/360 mainframe, and that if all of those instructions could be executed just once, it would take about a second to run all of them on a System 360 mod 50. On today's machines, probably a few hundred microseconds. Doesn't seem like much of a result for several years of my life. (Ah, but quite a few of those LoC were something called Hypertext.)
Rules for Optimization:
#1. Don't do it.
#2. (Experts only) Don't do it yet.
We had this discussion at the ACM 20th Conference in 1968. It was me and Andy van Dam from Brown arguing with Al Perlis (Yale), Bernie Galler (UMich), and Harlan Mills (IBM). We used a simplified version of IBM/360 Assembler called SOS in the first-semester CS course, and the big guns on the other side thought we should switch to Algol. I mentioned my IF-THEN-ELSE macros for Assembler, and Harlan really liked the idea.
Afterward a cute Pembroker in a really short skirt came up to introduce herself. I don't know if she agreed with our argument, but she's been my wife for quite awhile now. I don't teach much any more, but when I teach beginning CS, I teach assembler. The students we taught machine programming to back then have held positions like VP at Microsoft, CS Department Head at MIT, Princeton, Washington, UNH, and Waterloo.
I wish people wouldn't keep referring to C as a "programming language;" it's a pathology.
Haven't seen it yet -- both shows are sitting on my TiVo HD -- but if it doesn't have those classy Tektronix storage tube displays, it's a horrible waste and an insult to the entire Ponderosa and the A Team. You know, those green displays where you can actually see the beam writing the picture like an electronic Etch-a-Sketch?
We actually built a simulation of an Etch-a-Sketch using an ARDS storage tube display. That's what passed for advanced graphics at Brown in 1967.
If we can convince the CIA of that (should be easy), we'll be on our way in force before the 2004 election. Of course, we won't have allowed for any way to come back.
That's why you put the crypto engine on the keyfob.
I actually patented that idea when I was at Prime Computer in 1981 (U.S. Patent 4,723,284). The patent was, of course, owned by Prime, which no longer exists, and has itself expired. I don't know what this does to the possible ownership of the idea.
In my patent, the private key was generated deep in the bowels of the manufacturing device, burned into the encryption chip in a way that made it impossible to retreive, and then completely erased from everywhere else. The public key was printed on the chip and also available for external electronic retrieval. In effect, the chip and keyfob now have a unique, unforgeable identity.
Blows Ashcroft's E-Mail Monitor out of the water
on
Can You Raed Tihs?
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· Score: 2, Insightful
"Carnivore" or whatever it's called now suddenly has a much harder problem. Add a liberal use of slang (pun intended), metaphores, spoonerisms, and the massive and increasing volume of spam that also has to be scanned, and it's probably out of business.
> Prior to any break, anyone at the top end of the elevator would experience some gravitational force.... Following a break, they would actually go into free fall.
That's true for one specific place slightly above the pre-break center of mass at GEO. Further out than that, the perceived force of gravity (produced by centripetal acceleration) will diminish by a tiny bit, but will still be there. Any long, thin object in orbit will be oriented along a line through the center of the earth, in what's called gravity-gradient stabilization, and will have some amount of perceived gravity away from its center everywhere but at the center of mass. Clip off a tiny amount at the bottom end and the center of mass shifts slightly and the perceived gravity changes slightly, but it doesn't go away.
A break of the SE anywhere in the atmosphere will only reduce the total mass by 1/10,000th or less, but the effect will be somewhat greater because the tension on the anchor will also be lost.
Note that "free fall" here only means the absence of gravity, not motion in the direction of the earth. In fact, the whole elevator will move up to a (very slightly) higher orbit.
The first space elevator is going to weigh about 800 tons. We may someday do big, heavy-lift elevators that weigh as much as 10,000 tons. Your calculations start out being off by eight orders of magnitude, and get worse.
It's much more correct to say that the only way we'll be able to detect that the elevator has fallen is by noticing that it's no longer there.
They wouldn't exactly "fall." Cutting the ribbon anywhere within the atmosphere only removes a tiny fraction of a percent of its mass; the rest of it will drift up and to the east at a couple of miles per hour. All we'll need to do is reel out a tiny bit more ribbon at the top and the whole thing will drift down and west until it's back where it started. Then grab the end and tie it down. No big deal; probably interrupt service for a week or so.
Something no one has mentioned is the difficulity of finding that tiny ribbon in the vast Pacific sky. The terrorist flying the jet won't even be able to see it until he gets within a mile or less; can you see something the size of a broomstick from ten miles?
Re:The idea is good the article is bull@#$%.
on
Space Elevator Going Up
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· Score: 2, Informative
Should be : 24 hour to complete a full orbit We all groaned at that mistake in the Guardian article, though you might be able to argue that a "year" for a given body is the period of time it takes to make one orbit around its primary. That is, everything orbits once a year. Pretty weak.
1. Tracing space junk ~0.01-1mm in size which flies around with a speed ~10km/sec. The ribbon will be about a meter wide, 20 microns thick, and curved across its width. Stuff that small will punch right through it, sure, but won't sever enough of it to cause it to break. Every couple of weeks a maintenance climber will go up looking for little punctures like that and patching them.
2. Moving platform fast enough on the ground to avoid collision at the altitude ~200 -1000 km . At those altitudes junk has the maximum density. Almost all of the junk big enough to hurt the ribbon is in orbit, is and will continue to be tracked on radar. There'll be plenty of warning; analysis says that the ribbon anchor will have to move about a kilometer once a day.
Edwards, who estimates it would take about $7bn to turn the concept into reality. This thing should weight no less then ISS. Most of it flies much higher orbit: 36,000-100,000km compare to ~500km for ISS,- READ: more expensive to get there. The initial ribbon, weighing about 40 tons, will go up in two Delta IV launches on spools. (Two more Delta IVs will take up the GEO transfer vehicle and the deployment mechanism.) The initial ribbon will be unreeled from GEO, one end flying down to the surface and the other climbing above GEO to serve as counterweight. We will then send a little tiny climber up this initial space elevator, splicing just a little bit more material to the ribbon along its entire length. Then another one, slightly larger because the ribbon is now a tiny bit stronger. Then another. After 210 climbers, the ribbon will be able to hold a 20 ton climber and we can start building a second ribbon.
So, you see, the Space Elevator is bootstrapped up to a usable size. We don't need to launch it with rockets; most of it goes up on itself. We only need 4 Delta launches, at an estimated price of $500 million each.
Slashdot Mirror
I hope you don't create spreadsheets for your company.
Two words: radiation belts
The Apollo astronauts crossed the radiation belts in about 30 minutes, getting a dosage of about 1/2 rad. That's approximately the recommended YEARLY dosage for non-nuclear workers. Passengers on the SE would take about 90 hours to cross the belts, giving them a dosage of about 100 rads. 500 is fatal, so they'd be very, very sick and most would die prematurely. (Info from a paper by Jorgensen and Patamia at the Conference).
It would take a huge amount of shielding, many tons, to protect just a few passengers. Doable for a few astronauts, but we'll need to find a better way before tourists ride the SE.
AI has been one of the great scams of the last 40 years, one whose main purpose was to wring money out of (D)ARPA and NSF. Maybe they've finally caught on.
Because of the "organized" part.
Minor point: you implied that gravity was in effect up to 35950 km and that centrifugal effect applied above that. In fact, both forces work on the whole length of the elevator, but gravity decreases and centrifigal force increases as you go up. At 35,950 km they are equal, and above that centrifigal force is larger. Bob Munck (Brown '67)
The other thing the military doesn't do is security. They think you make your systems secure by classifying the source code. It's always a race to the bottom to find which is worse, system reliability or system security. This doesn't bode well for an attempt to build a HUGE secure, reliable network.
My prediction: they'll burn through tens of billions of dollars, chew up the careers of a large number of programmers and managers, and the whole idea will fade away around 2010 or so. One good thing; the coding cannot possibly be outsourced.
Read a book, already. (One that's not based on a movie or TV show.)
Don't forget the kid who pushes all million buttons, or the problems with digestive gases.
An artificial satellite in geostationary orbit,
No, no forget all that "geostationary" stuff. What holds the Space Elevator up is good old centrifugal force. Whirl a rock on the end of a string around your head: the string is held taut and the rock out at right angles to gravity by centrifugal force. In similar fashion, the Space Elevator will be whirling around so fast that it'll be held taut. Sure, it's only going around once every 24 hours, but it's really, really long.
(Yes, centrifugal force isn't real, it's virtual. It's the apparent force created on a mass under centripetal acceleration.)
That's a different situation. The Tivo software doesn't know that the channel it's recording is music, because it doesn't know anything about the incoming signal. In DirecTivo, the software is running both the recording and the channel selection function.
Just as a point of interest, DirecTiVo -- the combination of TiVo and DirecTV -- won't allow you to record the 40 or so music channels. It's probably the same irrational people. When XM does allow recording, they'll do it in such a way that they can block it for selected shows.
Beam the data into space. When you want to retrieve it, you'll have to go catch it.
You don't want the beam waving all over the place because of the Earth's rotation, so aim it at the North Star (assuming you're in the northern hemisphere). If this activity continues for a long time, you'll have to compensate for the precession of the Earth's axis and for various smaller wobbles; I believe a correction every century or so will suffice.
Note that if the speed of light really is an absolute limit, you'll have to count on the universe being curved and wait for the data to come around again. Again, you didn't say anything to indicate that this might be a problem.
Very low. Even at the end of a 100,000 km tether, the effective gravity is -0.0538 g. Actually, centripetal acceleration due to the rotation of the Earth is -0.0574 g and Earth's gravity is 0.003596 g. You're much better off using this wonderful carbon nanotube ribbon material to connect two (or more) habitats and spin them around each other, with the whole construct orbiting near the elevator at GEO.
90 cm in width, "thinner than a piece of paper" (actually, about 10 microns) thick. Your calculations are off by about five orders of magnitude. Reading is a skill.
As an old microcoder, my basic inclination is to think of machine instructions as interpreted. That's even true of RISC machines, though less so. You haven't lived until you've fixed a bug by weaving a wire through a row of tiny transformers to change the microcode.
Afterward a cute Pembroker in a really short skirt came up to introduce herself. I don't know if she agreed with our argument, but she's been my wife for quite awhile now. I don't teach much any more, but when I teach beginning CS, I teach assembler. The students we taught machine programming to back then have held positions like VP at Microsoft, CS Department Head at MIT, Princeton, Washington, UNH, and Waterloo.
I wish people wouldn't keep referring to C as a "programming language;" it's a pathology.
We actually built a simulation of an Etch-a-Sketch using an ARDS storage tube display. That's what passed for advanced graphics at Brown in 1967.
If we can convince the CIA of that (should be easy), we'll be on our way in force before the 2004 election. Of course, we won't have allowed for any way to come back.
I actually patented that idea when I was at Prime Computer in 1981 (U.S. Patent 4,723,284). The patent was, of course, owned by Prime, which no longer exists, and has itself expired. I don't know what this does to the possible ownership of the idea.
In my patent, the private key was generated deep in the bowels of the manufacturing device, burned into the encryption chip in a way that made it impossible to retreive, and then completely erased from everywhere else. The public key was printed on the chip and also available for external electronic retrieval. In effect, the chip and keyfob now have a unique, unforgeable identity.
"Carnivore" or whatever it's called now suddenly has a much harder problem. Add a liberal use of slang (pun intended), metaphores, spoonerisms, and the massive and increasing volume of spam that also has to be scanned, and it's probably out of business.
That's true for one specific place slightly above the pre-break center of mass at GEO. Further out than that, the perceived force of gravity (produced by centripetal acceleration) will diminish by a tiny bit, but will still be there. Any long, thin object in orbit will be oriented along a line through the center of the earth, in what's called gravity-gradient stabilization, and will have some amount of perceived gravity away from its center everywhere but at the center of mass. Clip off a tiny amount at the bottom end and the center of mass shifts slightly and the perceived gravity changes slightly, but it doesn't go away.
A break of the SE anywhere in the atmosphere will only reduce the total mass by 1/10,000th or less, but the effect will be somewhat greater because the tension on the anchor will also be lost.
Note that "free fall" here only means the absence of gravity, not motion in the direction of the earth. In fact, the whole elevator will move up to a (very slightly) higher orbit.
It's much more correct to say that the only way we'll be able to detect that the elevator has fallen is by noticing that it's no longer there.
Something no one has mentioned is the difficulity of finding that tiny ribbon in the vast Pacific sky. The terrorist flying the jet won't even be able to see it until he gets within a mile or less; can you see something the size of a broomstick from ten miles?
We all groaned at that mistake in the Guardian article, though you might be able to argue that a "year" for a given body is the period of time it takes to make one orbit around its primary. That is, everything orbits once a year. Pretty weak.
1. Tracing space junk ~0.01-1mm in size which flies around with a speed ~10km/sec.
The ribbon will be about a meter wide, 20 microns thick, and curved across its width. Stuff that small will punch right through it, sure, but won't sever enough of it to cause it to break. Every couple of weeks a maintenance climber will go up looking for little punctures like that and patching them.
2. Moving platform fast enough on the ground to avoid collision at the altitude ~200 -1000 km . At those altitudes junk has the maximum density.
Almost all of the junk big enough to hurt the ribbon is in orbit, is and will continue to be tracked on radar. There'll be plenty of warning; analysis says that the ribbon anchor will have to move about a kilometer once a day.
Edwards, who estimates it would take about $7bn to turn the concept into reality. This thing should weight no less then ISS. Most of it flies much higher orbit: 36,000-100,000km compare to ~500km for ISS,- READ: more expensive to get there.
The initial ribbon, weighing about 40 tons, will go up in two Delta IV launches on spools. (Two more Delta IVs will take up the GEO transfer vehicle and the deployment mechanism.) The initial ribbon will be unreeled from GEO, one end flying down to the surface and the other climbing above GEO to serve as counterweight. We will then send a little tiny climber up this initial space elevator, splicing just a little bit more material to the ribbon along its entire length. Then another one, slightly larger because the ribbon is now a tiny bit stronger. Then another. After 210 climbers, the ribbon will be able to hold a 20 ton climber and we can start building a second ribbon.
So, you see, the Space Elevator is bootstrapped up to a usable size. We don't need to launch it with rockets; most of it goes up on itself. We only need 4 Delta launches, at an estimated price of $500 million each.