An increasing amount of the world's information will never be put in paper book form. Two reasons are accessibility and cost.
For example, the enormous volume of documentation on the Space Station program (on which I work) mainly exists as an online archive( at http://issa-www.jsc.nasa.gov/cgi-bin/dsql+/ORAP?-h +palshome, which isn't accessible to the general public as far as I know, but all it would take is a permissions fix to change that). There are a few paper copies kept in fireproof vaults as a backup, but the online archive lets me find in minutes what would take days with the paper version.
Second issue is cost. A standard 5-drawer file cabinet holds around 225 MBytes of printed text, and costs $1700 to fill, counting the cabinet and printer costs. Printing books is going to be on the same order of cost (shelves rather than file cabinet). That's around $1 of hard disk space. If you multiply printing and shelving by the number of copies in libraries across the country, you are talking factor of a million or so cheaper to store on disk rather than paper. Having the internet as a distribution system brings the cost balance back a bit, but I think any rational comparison would show online is much cheaper than paper in total. So the LoC is costing the taxpayers money by insisting on paper.
They don't, but then that wasn't a design requirement. Shooting down ballistic missiles in flight was. The way you stop back-seat nukes is by keeping really close tabs on who has the critical technologies (like isotope separation and making nice, symmetrical trigger implosions), and where the inventory is (fissionable materials, live bombs). Your other defense is that old standby, MAD. Any organization that uses nukes on the US knows that there won't be anything left of them after we are through.
For additional nightmares, consider that a liquefied natural gas tanker carries a nuclear bomb worth of energy. If you can figure out a way to make it go boom in a city harbor, it would be as bad as using a nuke. Or consider an truck bomb attack directed against a nuclear power plant. The containment buildings are pretty tough, but the control rooms aren't.
"When an elderly but distinguished scientist says something is impossible, he is almost surely wrong" - Arthur C. Clarke
I collect Scientific American, and one of the most fascinating aspects of my collection is the series of articles on why this or that technology won't work or has reached it's limits. The authors that SciAm gets to write it's articles usually fit the definition in Clarke's Law above, and they have invariably been wrong, usually quickly.
Two examples: SciAm published an article in 1947 on why long range ballistic missiles wouldn't work, mostly based on the inability to make the guidance systems accuarate enough. About 5 years later we were deploying them.
They also published an article in the 1980s on why space-based lasers for strategic defense wouldn't work. I was working in that area at the time, and the problems they raised had already been solved, we just couldn't talk about it because it was classified.
Here's an approach for increasing magnetic storage capacity I haven't seen elsewhere: Current tape drives are high capacity but slow. They work just like ancient scrolls, unrolling and rolling up on a spool. Think instead like a codex (i.e. a modern book with pages). Have a stack of magnetic sheets arranged like the mess of catalogs at an auto parts place (spines down, pages held to +- 45 degrees of vertical by end holders). Use a static charge to fan out the leaves at the place you want to read, then slip in the read head from above. This gives you 3-D magnetic storage with fast (at least compared to tape) access time.
Some information about these tanks from a guy who works in the building they were lost from.
First of all, what were these tanks? The space station uses an oxygen/nitrogen atmosphere that approximates sea level composition, without the 1% argon and trace elements. As the crew breathes and uses up oxygen, the Carbon Dioxide Removal Assembly scavenges the CO2 and dumps it overboard. The oxygen tank provide the replacement O2 to make up what is lost. The space station modules have many cables and pipes that go through the walls of the modules, and the modules are bolted to each other. There is a certain amount of leakage at these points (on the order of a pound a day). Since the station atmosphere is 80% nitrogen, you need to replace that too.
You need to play with the composition of the atmosphere in the airlock to prepare for a spacewalk (reduce dissolved nitrogen in the blood to prevent the bends), and also to refill the spacesuit tanks afterwards. For this reason these tanks are mounted on the outside of the Airlock module, which is still under construction here in Huntsville.
There are up to three tanksets that can be mounted on the airlock at any one time, each tankset consisting of two pressure tanks, the 'doghouse' that covers them and provides insulation and protection from space debris, and the structural mountings, plumbing, valves, and wiring. It's not clear to me what exactly was lost, but from the size of the box it was likely one tankset, which is about 3x3x4 feet in size. There are something like 8-10 total tanksets in existence, since full ones would be brought up to replace the ones on orbit that were empty, plus spares for 10 years of operation.
Why do they cost $750,000? Boeing and it's subcontractors spend about $45,000 a pound to design airplanes or space stations. Pound for pound they cost the same to develop, because it's the same guys following the same design standards, using the same type of CAD workstations, etc. And the airplanes sell for $600 a pound. So assume the tankset weighs 300 pounds (I haven't looked up the weight, that's an educated guess based on the size). So the total design cost would have been $13.5 million spread over 10 units, or $1.35 million per unit, plus a manufacturing cost of $180,000 per unit. The quoted cost of $750,000 is less than this because the tankset is simpler than average for the station or an airplance as a whole , being mostly structure rather than a mix of structure and active components like computers and life support systems.
How did they get thrown out? Most likely (I have no official information to go on) sloppy inventory tracking and labeling. I'm pretty sure someone didn't walk out with them, since the storage yard outside the building is behind two barbed wire fences, and with crate you are talking about a 500 pound item. Most of the US portion of the Space Station is being assembled in this building, and crates of components are arriving all the time. A trash contractor periodically picks up dumpsters full of packing materials and the empty crates, and I suspect the screwup was something like parking a full crate over by the empty crate pile, and no one bothered to check to see if it was really empty. The overall impact to the program isn't so bad, since you effectively have lost one of your spare units (you have 9 now instead of 10), and they will simply produce a replacement.
These are not exactly new ideas. I worked on inflatable aerobrake studies in the early 1980s. It was a cover story in Popular Science in the mid-80's, and my boss was a technical consultant for the movie 2010, which had the spacecraft aerobrake into Jupiter orbit. Slow aerobraking, without special hardware for the braking part, has been done by the Venus Radar Mapper and more recently by the Mars Global Surveyor.
Inflatables are even older. Somewhere in my files is a report by Goodyear (of course) dating to the 1960's on inflatable space hardware, like space station modules with a hard cylindrical core with the life support equipment, surrounded by a inflatable donut which became the living space.
Rather than the case in the article of a copy running in parallel with the meatware version, think instead of a backup copy being made by the nanobots. This can be discrete backups (daily, monthly, whatever), or more-or-less realtime mirroring.
The backup copy isn't activated unless the meatware version is dead. Then there is continuity in the sense that only one version at a time thinks it's the 'real me".
Daniel
When Data storage is limited, I am the predator
on
The Regulon
·
· Score: 1
In the days of paper-based file storage (like when I started my working life), I was the one who weeded out the weak and useless data. I was only given one or two file cabinets worth of storage space for all my work-related data, and I periodically (usually when I got moved from one desk location to another) weeded the files of stuff I didn't need enough to keep.
Two file cabinets of printed documents equal about
450 MB of text. So the early years of PC's saw the same predator process - My disk filled up with stuff, and I had to decide what to keep and what to throw out.
My current PC at work has 5 of it's 6 GB still free after using it for a year. It's the first machine that has significantly more storage than
I could hold in paper form (the previous machine
had 600MB). And my new home PC has a 40GB disk drive. That's a lot bigger than the 4 GB of paper
books I have at home (and I have a lot of books
at home).
So, suddenly, we have a greatly enlarged resource - data storage. It's growing faster than I'm filling it at the moment. Since there is no extra cost for holding the data on disk (a 1 costs the same to store as a 0), I have no reason to be a ruthless predator and filter out the data I need the least.
Come the time when I'm getting new data so fast that my disks fill up, and I can't afford to keep filling CD-RWs with offline-data, then I'll have to be a predator again and kill files.
People have always tried to incorporate good genes into their offspring. When you choose a mate, whether you choose for beauty, brains, muscles, etc., you are choosing to incorporate those characteristics in the genetic makeup of your children.
What is new is being able to choose good genes in a more controlled fashion than a random 50/50 mix of your and your mate's genes.
For example, if you have a single copy of a disease-causing gene, you could choose the other copy of the chromosome to contribute to your offspring, and thus weed out that disease from your children. Where's the moral problem with that?
But anyway, before we have time to perfect the genetic screening/selection techniques and raise a generation of "perfect" children, the computer intelligences will have taken over anyway, so it will be a moot point.
This invention seems to be a reinvention of report generation from a database according to a template. For example, in a large bank, the tellers have many terminals, all displaying different account information based on a customers' profile. The account database is live, being updated constantly as checks clear, ATMs are used to withdraw cash, etc. The account display can have additional fields or pages that appear depending on which services that customer has (checking, savings, loans, etc.).
I don't see what is new and un-obvious about the Yahoo patent.
Gate's 'salary' is 400K according to the proxy statement, and his wife also works for MSFT and probably pulls down a couple of 100K too (but she's not in the top 5 so she isn't listed in SEC filings).
That salary is insignificant in comparison with the approximately $13 billion in MSFT stock Gates has sold in the last two years and not donated to his foundation. The interest alone, even in a lousy savings account, is 1000 times his official salary as CEO of MSFT. And you can assume that he's got a smart investment manager making that money work for him.
At a nominal 8% return, he can pay for a new $40 million house like the one he built every month, and still have $500 million a year in play money.
I don't this actually happens. Likely his 'living expenses' are in the $10M a year range, and the rest of the money is being spread around in other investments so that when MSFT crashes, he'll still be the world's richest individual.
The Gates foundation has the equivalent of 200M shares of MSFT stock. Gates has reduced his holdings by 360M shares in the past two years, which is essentially the time period the foundation has been funded also. So 160M shares were still sold outright.
Now, the foundation, if it is prudently managed, should not keep all it's assets in MSFT stock, it should diversify. Their annual report does not cover what assets they hold specifically.
If you compare MSFT's proxy statements from two years ago to the Sept 1999 one, you find that the directors of the company as a group have reduced their ownership stake from 35.8% to 25.7%.
I attended a NASA space elevator workshop earlier this year, and I'd like to make a few comments. First of all, the cable hanging from synchronous orbit is not an optimum design. Large structures have to support all the load at each point. So a cable hanging down is smallest at the bottom, and each unit of length going up has to be an increment thicker to support the added weight of that length of cable. So as you go up the cable cross section gets exponentially bigger, because thicker cable in the higher sections add proportionately more load. Now consider a tower built up from the ground, using the same type of high strength materials as the cable would use. A tower will show the same type of exponential taper, but with the fat portion near the ground (i.e. it will look like the Eiffel Tower). For a minimum weight design, you would build a tower up from the ground and have it's top meet a cable hanging down from orbit. To put some numbers to it, assume you have 2 million psi carbon fiber of the buckytube flavor. A constant section strand 800 km long at one gee can just support it's own length. The physics of the situation says the cross section needs to increase by a factor of e (2.718..) every 800 km to keep from breaking. The earth's gravity well is the equivalent of 6400 km deep due to the fall off of gravity with height. So a cable hanging all the way from synchronous orbit, which is only 2% from the top of the gravity well, needs to be about e^8 times the mass of whatever you are lifting, or about 3000:1. If you have a tower and a cable, each e^4 times the cargo weight, then the combined weight is 110 times the cargo weight. This is a much simplified analysis. In the real world, you will have factors of safety and redundant design, overhead beyond a bare cable to deal with. Also, the tower, being close to the ground is presumably cheaper to build than the stuff in orbit. Finally, compressive and tension strengths for the same material are not the same. But the basic idea is that a cable all the way from orbit is not optimum. Secondly, buckytubes are presently made at a cost of $800/gram, a few grams at a time. Work is being done on scaling up production and bringing down cost. If it gets down in the range of $10/gram, people will start using it in places where weight is extremely critical (that's about the cost to launch things into space for example). Thirdly, long cables in orbit MUST be damage tolerant and have self-repair capabilities because man-made space junk and natural meteoroids WILL run into it. For example, you can have 6 main cables, any 4 of which can carry the load, with cross-straps every 10 km to re-distribute the load around a break. The cables need to be separated by more than the width of the widest thing that can run into it (think space station = 120 m wide). When a cable gets broken, a "repair spider" runs out to the break with a replacement spool of cable, winds in the broken pieces, and installs the new one. Fourthly, in the near term, a full up space elevator is not economic. Single-stage to orbit rockets are marginal on having payload (88% fuel, 10% structure, 2% payload). So anything you can do to relieve them of some of the rocket propulsion job can have a dramatic impact on payload capacity. So a tower going up from the ground in the range of 10-100 km (which can be done without buckytubes), and a cable in orbit to catch the rocket which is 100s of km long can help a lot, and can be done with existing carbon fibers.
Slashdot Mirror
An increasing amount of the world's information will never be put in paper book form. Two reasons are accessibility and cost.
h +palshome, which isn't accessible to the general public as far as I know, but all it would take is a permissions fix to change that). There are a few paper copies kept in fireproof vaults as a backup, but the online archive lets me find in minutes what would take days with the paper version.
For example, the enormous volume of documentation on the Space Station program (on which I work) mainly exists as an online archive( at http://issa-www.jsc.nasa.gov/cgi-bin/dsql+/ORAP?-
Second issue is cost. A standard 5-drawer file cabinet holds around 225 MBytes of printed text,
and costs $1700 to fill, counting the cabinet and
printer costs. Printing books is going to be on
the same order of cost (shelves rather than file
cabinet). That's around $1 of hard disk space.
If you multiply printing and shelving by the number of copies in libraries across the country,
you are talking factor of a million or so cheaper to store on disk rather than paper. Having the internet as a distribution system brings the cost balance back a bit, but I think any rational comparison would show online is much cheaper than paper in total. So the LoC is costing the taxpayers money by insisting on paper.
Daniel
They don't, but then that wasn't a design requirement. Shooting down ballistic missiles in flight was. The way you stop back-seat nukes is by keeping really close tabs on who has the critical technologies (like isotope separation and making nice, symmetrical trigger implosions), and where the inventory is (fissionable materials, live bombs). Your other defense is that old standby, MAD. Any organization that uses nukes on the US knows that there won't be anything left of them after we are through.
For additional nightmares, consider that a liquefied natural gas tanker carries a nuclear bomb worth of energy. If you can figure out a way to make it go boom in a city harbor, it would be as bad as using a nuke. Or consider an truck bomb attack directed against a nuclear power plant. The containment buildings are pretty tough, but the control rooms aren't.
Daniel
"When an elderly but distinguished scientist says something is impossible, he is almost surely wrong" - Arthur C. Clarke
I collect Scientific American, and one of the most fascinating aspects of my collection is the series of articles on why this or that technology won't work or has reached it's limits. The authors that SciAm gets to write it's articles usually fit the definition in Clarke's Law above, and they have invariably been wrong, usually quickly.
Two examples:
SciAm published an article in 1947 on why long range ballistic missiles wouldn't work, mostly based on the inability to make the guidance systems accuarate enough. About 5 years later we were deploying them.
They also published an article in the 1980s on why space-based lasers for strategic defense wouldn't work. I was working in that area at the time, and the problems they raised had already been solved, we just couldn't talk about it because it was classified.
Here's an approach for increasing magnetic storage capacity I haven't seen elsewhere: Current tape drives are high capacity but slow. They work just like ancient scrolls, unrolling and rolling up on a spool. Think instead like a codex (i.e. a modern book with pages). Have a stack of magnetic sheets arranged like the mess of catalogs at an auto parts place (spines down, pages held to +- 45 degrees of vertical by end holders). Use a static charge to fan out the leaves at the place you want to read, then slip in the read head from above. This gives you 3-D magnetic storage with fast (at least compared to tape) access time.
Daniel
Some information about these tanks from a guy who works in the building they were lost from.
First of all, what were these tanks? The space station uses an oxygen/nitrogen atmosphere that approximates sea level composition, without the 1% argon and trace elements. As the crew breathes and uses up oxygen, the Carbon Dioxide Removal Assembly scavenges the CO2 and dumps it overboard. The oxygen tank provide the replacement O2 to make up what is lost. The space station modules have many cables and pipes that go through the walls of the modules, and the modules are bolted to each other. There is a certain amount of leakage at these points (on the order of a pound a day). Since the station atmosphere is 80% nitrogen, you need to replace that too.
You need to play with the composition of the atmosphere in the airlock to prepare for a spacewalk (reduce dissolved nitrogen in the blood to prevent the bends), and also to refill the spacesuit tanks afterwards. For this reason these tanks are mounted on the outside of the Airlock module, which is still under construction here in Huntsville.
There are up to three tanksets that can be mounted on the airlock at any one time, each tankset consisting of two pressure tanks, the 'doghouse'
that covers them and provides insulation and protection from space debris, and the structural mountings, plumbing, valves, and wiring. It's not clear to me what exactly was lost, but from the size of the box it was likely one tankset, which is about 3x3x4 feet in size. There are something like 8-10 total tanksets in existence, since full ones would be brought up to replace the ones on orbit that were empty, plus spares for 10 years of operation.
Why do they cost $750,000? Boeing and it's subcontractors spend about $45,000 a pound to design airplanes or space stations. Pound for pound they cost the same to develop, because it's the same guys following the same design standards, using the same type of CAD workstations, etc. And the airplanes sell for $600 a pound. So assume the tankset weighs 300 pounds (I haven't looked up the weight, that's an educated guess based on the size). So the total design cost would have been $13.5 million spread over 10 units, or $1.35 million per unit, plus a manufacturing cost of $180,000 per unit. The quoted cost of $750,000 is less than this because the tankset is simpler than average for the station or an airplance as a whole , being mostly structure rather than a mix of structure and active components like computers and life support systems.
How did they get thrown out? Most likely (I have no official information to go on) sloppy inventory tracking and labeling. I'm pretty sure someone didn't walk out with them, since the storage yard outside the building is behind two barbed wire fences, and with crate you are talking about a 500 pound item. Most of the US portion of the Space Station is being assembled in this building, and crates of components are arriving all the time. A trash contractor periodically picks up dumpsters full of packing materials and the empty crates, and I suspect the screwup was something like parking a full crate over by the empty crate pile, and no one bothered to check to see if it was really empty. The overall impact to the program isn't so bad, since you effectively have lost one of your spare units (you have 9 now instead of 10), and they will simply produce a replacement.
These are not exactly new ideas. I worked on
inflatable aerobrake studies in
the early 1980s. It was a cover story in
Popular Science in the mid-80's, and my boss was
a technical consultant for the movie 2010, which
had the spacecraft aerobrake into Jupiter orbit.
Slow aerobraking, without special hardware for
the braking part, has been done by the Venus
Radar Mapper and more recently by the Mars
Global Surveyor.
Inflatables are even older. Somewhere in my files
is a report by Goodyear (of course) dating to the
1960's on inflatable space hardware, like space
station modules with a hard cylindrical core
with the life support equipment, surrounded by
a inflatable donut which became the living
space.
Daniel
Rather than the case in the article of a copy
running in parallel with the meatware version,
think instead of a backup copy being made by
the nanobots. This can be discrete backups
(daily, monthly, whatever), or more-or-less
realtime mirroring.
The backup copy isn't activated unless the
meatware version is dead. Then there is
continuity in the sense that only one version
at a time thinks it's the 'real me".
Daniel
In the days of paper-based file storage (like when I started my working life), I was the one who weeded out the weak and useless data. I was only given one or two file cabinets worth of storage space for all my work-related data, and I periodically (usually when I got moved from one desk location to another) weeded the files of stuff I didn't need enough to keep.
Two file cabinets of printed documents equal about
450 MB of text. So the early years of PC's saw the same predator process - My disk filled up with stuff, and I had to decide what to keep and what to throw out.
My current PC at work has 5 of it's 6 GB still free after using it for a year. It's the first machine that has significantly more storage than
I could hold in paper form (the previous machine
had 600MB). And my new home PC has a 40GB disk drive. That's a lot bigger than the 4 GB of paper
books I have at home (and I have a lot of books
at home).
So, suddenly, we have a greatly enlarged resource - data storage. It's growing faster than I'm filling it at the moment. Since there is no extra cost for holding the data on disk (a 1 costs the same to store as a 0), I have no reason to be a ruthless predator and filter out the data I need the least.
Come the time when I'm getting new data so fast that my disks fill up, and I can't afford to keep filling CD-RWs with offline-data, then I'll have to be a predator again and kill files.
Daniel
You can read it online here
People have always tried to incorporate good
genes into their offspring. When you choose a mate,
whether you choose for beauty, brains, muscles,
etc., you are choosing to incorporate those
characteristics in the genetic makeup of your
children.
What is new is being able to choose good genes
in a more controlled fashion than a random
50/50 mix of your and your mate's genes.
For example, if you have a single copy of a
disease-causing gene, you could choose the
other copy of the chromosome to contribute
to your offspring, and thus weed out that
disease from your children. Where's the moral
problem with that?
But anyway, before we have time to perfect
the genetic screening/selection techniques
and raise a generation of "perfect" children,
the computer intelligences will have taken
over anyway, so it will be a moot point.
Daniel
This invention seems to be a reinvention of report generation from a database according to a template. For example, in a large bank, the tellers have many terminals, all displaying different account information based on a customers' profile. The account database is live,
being updated constantly as checks clear, ATMs
are used to withdraw cash, etc. The account
display can have additional fields or pages that
appear depending on which services that customer
has (checking, savings, loans, etc.).
I don't see what is new and un-obvious about the
Yahoo patent.
Gate's 'salary' is 400K according to the proxy
statement, and his wife also works for MSFT and
probably pulls down a couple of 100K too (but
she's not in the top 5 so she isn't listed in
SEC filings).
That salary is insignificant in comparison with
the approximately $13 billion in MSFT stock
Gates has sold in the last two years and not
donated to his foundation. The interest alone,
even in a lousy savings account, is 1000 times
his official salary as CEO of MSFT. And you
can assume that he's got a smart investment
manager making that money work for him.
At a nominal 8% return, he can pay for a new
$40 million house like the one he built every
month, and still have $500 million a year in
play money.
I don't this actually happens. Likely his
'living expenses' are in the $10M a year range,
and the rest of the money is being spread around
in other investments so that when MSFT crashes,
he'll still be the world's richest individual.
The Gates foundation has the equivalent of 200M
shares of MSFT stock. Gates has reduced his
holdings by 360M shares in the past two years,
which is essentially the time period the foundation
has been funded also. So 160M shares were still
sold outright.
Now, the foundation, if it is prudently managed,
should not keep all it's assets in MSFT stock,
it should diversify. Their annual report does
not cover what assets they hold specifically.
If you compare MSFT's proxy statements from two
years ago to the Sept 1999 one, you find that the
directors of the company as a group have reduced
their ownership stake from 35.8% to 25.7%.
The breakdown by person is:
Gates 22.3% -> 15.3%
Allen 7.6% -> 5.0%
Ballmer 4.9% -> 4.7%
Others 1.0% -> 0.6%
Are they getting out while the getting's good?
I attended a NASA space elevator workshop earlier this year, and I'd like to make a few comments. First of all, the cable hanging from synchronous orbit is not an optimum design. Large structures have to support all the load at each point. So a cable hanging down is smallest at the bottom, and each unit of length going up has to be an increment thicker to support the added weight of that length of cable. So as you go up the cable cross section gets exponentially bigger, because thicker cable in the higher sections add proportionately more load. Now consider a tower built up from the ground, using the same type of high strength materials as the cable would use. A tower will show the same type of exponential taper, but with the fat portion near the ground (i.e. it will look like the Eiffel Tower). For a minimum weight design, you would build a tower up from the ground and have it's top meet a cable hanging down from orbit. To put some numbers to it, assume you have 2 million psi carbon fiber of the buckytube flavor. A constant section strand 800 km long at one gee can just support it's own length. The physics of the situation says the cross section needs to increase by a factor of e (2.718..) every 800 km to keep from breaking. The earth's gravity well is the equivalent of 6400 km deep due to the fall off of gravity with height. So a cable hanging all the way from synchronous orbit, which is only 2% from the top of the gravity well, needs to be about e^8 times the mass of whatever you are lifting, or about 3000:1. If you have a tower and a cable, each e^4 times the cargo weight, then the combined weight is 110 times the cargo weight. This is a much simplified analysis. In the real world, you will have factors of safety and redundant design, overhead beyond a bare cable to deal with. Also, the tower, being close to the ground is presumably cheaper to build than the stuff in orbit. Finally, compressive and tension strengths for the same material are not the same. But the basic idea is that a cable all the way from orbit is not optimum. Secondly, buckytubes are presently made at a cost of $800/gram, a few grams at a time. Work is being done on scaling up production and bringing down cost. If it gets down in the range of $10/gram, people will start using it in places where weight is extremely critical (that's about the cost to launch things into space for example). Thirdly, long cables in orbit MUST be damage tolerant and have self-repair capabilities because man-made space junk and natural meteoroids WILL run into it. For example, you can have 6 main cables, any 4 of which can carry the load, with cross-straps every 10 km to re-distribute the load around a break. The cables need to be separated by more than the width of the widest thing that can run into it (think space station = 120 m wide). When a cable gets broken, a "repair spider" runs out to the break with a replacement spool of cable, winds in the broken pieces, and installs the new one. Fourthly, in the near term, a full up space elevator is not economic. Single-stage to orbit rockets are marginal on having payload (88% fuel, 10% structure, 2% payload). So anything you can do to relieve them of some of the rocket propulsion job can have a dramatic impact on payload capacity. So a tower going up from the ground in the range of 10-100 km (which can be done without buckytubes), and a cable in orbit to catch the rocket which is 100s of km long can help a lot, and can be done with existing carbon fibers.