"Why is it that people find it more important to research into going to the moon then research on how to build toilets?"
Short answer: Because spending money on space research and development will ultimately help you make toilets (and plubming and sewage treatment plants and...) faster, better and cheaper.
No area of knowlege is wholly independent of everything else. Raising your technology and knowledge base in one field will ultimately raise those bases in all fields. Hell, for the most part nobody would have indoor plumbing if Rome didn't spend so much on defense. Strong army = more lands conquered = more lands to supply with clean water = need to invent aqueducts.
While I agree with the idea of spending a little on space R&D instead of blowing it all on social reform programs (who needs a bunch of people who can all get along hunky-dory if none of them have ever seen a telephone?)...
"How many Americans are without health insurance? How many Americans are in jail? How many Americnas suffer from obesity?"
My GOD man, do you see what you're calling "poor?" I've never really been out of the US but at least I know that being here in the thick of it can really skew your viewpoint. We live in a country where the vast majority of the people below the so-called "poverty line" own a car, a television and a microwave oven! Poor people in India don't even have a damned wall socket (if they have a wall!) to plug a television into, let alone the knowledge of how to use one (not like they've ever seen one before...).
What you're referring to as India's "middle class" is the slice of their population that can best relate to "middle class in the US." In the vast majority of the rest of the world, that's called "upper class."
"What I want to see is a nation or a group of nations going to the moon for the purpose of DOING something."
The "somethings" you refer to simply will not happen until space launches become cheap and/or plentiful. That doesn't happen overnight, economy of scale doesn't happen until you've built up the scale to begin with. And this is especially true with new technology, where you need to learn new construction and engineering methods before you can even think of large-scale production. When it comes to space exploration, we're still in the middle of the "research & development" stages (they don't call it space exploration for nothing).
Not that this means that R&D isn't profitable, however. It's just a slower turn-around than you seem to be demanding. Quite a big chunk of money was sunk into the Saturn V program, but 30+ years on we're still not done reaping the benefits in new technology and processes spun off from that project.
If you're so eager for a quick buck, why not do what everybody else just like you has done and day-trade some Enron stock? Unrealistic investment turn-around expectations go hand in hand with unrealistic accounting...
If she really loved you she'd be happier with a FDDI ring...
Re:Why doesn't anybody listen? - to the FAQ?
on
Going Up?
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· Score: 2
"Yes it is going to be 22,000 miles long. But it is going to be VERY thin,very little over all mass. There is going to be a VERY small amout of mass in this compared to the world trade towers."
Why am I scared? Being one long strand, the top will accelerate as fast as the bottom. If we didn't have an atomsphere, that acceleration would go unchecked. 9.8 m/s/s over 45,000,000,000 meters gives you a velocity that's an appreciable fraction of the speed of light, a velocty about where a single gram would have about a kiloton of TNT in kinetic energy.
Yes, the atmosphere will slow it down, but not nearly as much as people here on./ seem to think it will (with nothing more than skin friction I don't see any reason not to believe that it would be coming down quite a bit faster than the speed of sound). And instead of grams falling down we'd have tons.
"should be humankind against itself, not each country against the other."
There's a difference?
No, I'm not trolling and I'm not being flippant. I fail to see how you can draw a line between "country vs. country" and "humanity vs. self," since countries are nothing more than a human institution.
"So your points are 1) It won't burn up because its moving slower than debris 2) It won't burn up because its moving faster than debris"
More like:
1.) It won't burn up because it starts below terminal velocity and accellerates, instead of starting above terminal velocity and having to be "braked" by the atmosphere.
2.) Its terminal velocity would be higher than for space debris because there is no air in front of the beanstalk, just more beansatlk.
"Next point. If there is nothing but beanstalk in front, it must be falling straight down. That being the case, what's the problem? It'll fall straight down and leave a big pile of tangled ribbon at its base."
1000 tons falling straight down at obnoxious velocities (which it would be) into the ocean = tsunami.
"Why won't it just cut through the ocean like it does the air?" you're about to ask. Because sooner or later, it's going to come across something that will make it bend, be it the surface of an ocean rig that's at the bottom of the beanstalk or the bottom of the ocean, and once that initial kink comes into being at the landing point, that structure is going to whip around near the landing ponit like there's no tomrrow. Take a look at photos of trains that have jumped the rail and you'll notice that the front cars are all smashed up and can be thrown quite far from the rail because the cars behind it still have a lot of momentum and nothing else to stop it.
Sure, the structure will probably burn up in the lower atmosphere in that kind of motion at the surface of the earth, but whether it burns up or not that momentum has to go somewhere (so sayeth Newton), which will probably still spell out an atmospheric shockwave that I wouldn't want to be anywhere near.
"If, on the other hand, if falls over, then it will indeed build up a wall of air against its HUGE surface area."
If it falls sideways. Which it won't because of it's huge surface area. Nowhere to go but straight down at an obnoxious speed.
"Finally, the tensions of falling would very likely fragment the ribbon. In fact, the article says it will be designed for this to be the case."
If its strong enough to pull up multi-ton cargo, how will it break apart under its own weight?
"I can only imagine the forces acting on a 60 km long streamer."
The difference is that a streamer isn't under tension while a falling beanstalk would be. It couldn't flap like that because the bottom would be pulling it down and inertia would try to counteract that by "pulling up." It would probably flap quite a bit as it nears the end of the collapse, but it will be more like my tape measure analogy in its motion.
If you drop a sheet of paper edge down, it will fall down pretty fast until the bottom edge gets deflected to one side, causing the paper to curl into a U and maximizing the surface area for air resistance to play on. That couldn't happen with this ribbon because there is no bottom edge to get picked up, only more ribbon. This design will be all too aerodynamic.
"yet its surface area is 45,000,000m x.10m or 45 million square meters. Thats a lot of drag."
It would be if it were falling sideways, but it won't. The side of a mile-long freight train has a whole heck of a lot of surface area, but the only thing that really matters as far as wind resistance is the surface area of the front of the engine.
" This is one of the reasons there's no longer a green Mozilla logo,"
Then I must be color-blind. I keep on seeing a green, fire-breathing lizard on the splash screen whenever I start Moz. And there's another green lizard delivering mail when I start Moz mail.
"Absolutely right. We shouldn't ever build any more tall buildings, or bridges, either. Yes, security is an issue, but it is for conventional rocketry as well--and we haven't stopped launching shuttles loaded with thousands of pounds of highly explosive material."
We're not talking about something 110 storeys tall. We're talking about something 22,000 miles tall. Orders of magitude difference here, with the potential to cause damage over areas measured in "square miles" instead of "city blocks."
"Except that as soon as the force of the falling cable below starts to really pull hard on the cable above, the cable will snap."
If it's strong enough to be able to pull up tons of payload, it's more than strong enough to be able to survive a mere 9.8 m/s/s acceleration.
"Well sure, but if you read the article, you would know that the cable will not be of uniform density. In principle, the cable can be very thin near the bottm end, and thicker in the middle."
When you're talking about something 22,000 miles long, and when talking about forces being exerted in geometric proportions, minor fluctuations in thickness like "tripling" or "by an order of magintude" won't make much difference. If you want to make a difference, the thickness better flare out like a trumpet bell.
"Using a counterweight just beyond geostationary orbit (as proposed, again in the article FAQ) will balance the weight of the cable below geostationary orbit."
1.) The counterweight will have to mass as much as 140 times the mass of the beanstalk (which itself will not be a negligible mass).
2.) All points in the beanstalk below geostationary altitude have a net force on it pointing downard. If there is a cut anywhere between the ground and 22,000 miles up, everything below the cut will come down. It doesn't matter if the cut is 20,000 miles up or "merely" 7 miles up, everything below the cut comes down.
"Consider, most space debris that "falls to earth" burns up in the atmosphere."
Consider that most space debris is moving extremely fast in relation to the atmosphere, while a falling beanstalk will start falling at rest.
Consider that most space debris comes down in "chunks," allowing a wall of air to be compressed in front of it. A falling beanstalk won't have a wall of air in front of it slowing it down, it will have yet more beanstalk in front of it pullint down faster.
Consider that, since there's nothing in front of a chunk of beanstalk beyond more beanstalk, the only friction you'll have is skin friction, allowing a much higher terminal velocity than you would have with "chunks."
"We even need to take special percautions to make sure out shuttles don't burn up on re-entry."
Look at the arrangement of the heat tiles on the shuttle. The bottom and leading edges are designed to withstand much more heat than the sides or the top. With a falling beanstalk, for all intents and purposes there are no "leading edges" or a "bottom," just more beanstalk.
Think of a train. Most of the wind resistance happens in front of the engine at the front. The engine plows through the air in front of it, and the cars behind it just move into the gap that was opened.
"I would be willing to bet the people working on this have much more scientific knowledge than you do sitting at home with your TI-83."
TI-92+, actually. Bit of a life-saver when it came to doing all those integrals involved in Fourier transforms in my partial differential equations class.
"I'm sure they've considered such things and take them into account. Do you honestly think a project like this would ever go up if we weren't 99% sure it would work?"
I don't see anything going up. I only see some website talking about the idea. Not everything on the internet is true or even feasable, even on Slashdot (which occasionally posts articles about perpetual motion machines).
"As currently proposed, the first Space Elevator is small! It is only 890 tons, less than half the mass of the Space Shuttle at launch."
Are we talking 1,780,000 pounds of weight, or 890,000 kilograms of mass? If we're talking weight, then its mass will be quite a bit higher than you'd expect (force of gravity drops off with altitude). If the number they spit out is the weight, then it would be a great deal more massive than the space shuttle.
"Your arguement is assuming the bottom pulls the top down (collapse), but what would happen if it were cut in half or breaks further up? Does the top spin into orbit and the bottom collapse?"
Orbital velocity for altitude X is inversely proportional to the altitude of X. In other words, the lower you are, the faster you have to be going in order to be in orbit.
However, for a beanstalk, every point below the top is actually going slower than the top (points toward the outside of a wheel are moving faster than points towards the inside, so a pebble stuck in the tire treads moves faster than the lug nuts). So those points aren't even going fast enough to be considered in orbit at the atltitude at the top, let alone their current altitude. Every point in the beanstalk between the bottom and geostationary orbit has a net force pulling down.
In other words, cut the ribbon anywhere between the ground and 22,000 miles up, and everything below the cut comes crashing down. Fly a plane into it at around 7 miles up, and you have seven miles of stuff coming down at you.
"The people working on this seem to think that their ribbon will burn up / disintegrate if it falls. But hey, what do they know?"
I'd certainly like to see their numbers. Things burn up in the atmosphere because of their high relative speed to it (the space shuttle, for example, hits the atmosphere going around mach 27 IIRC). The beanstalk will start falling from a dead stop in relation to the ground. It will accellerate to terminal velocity for the lower portion and probably continue down at that constant velocity (which will be pretty fast, and when squared and multiplied by half the mass of something 45,000,000 meters long, will be a frightening amount of kinetic energy).
Besides, most of the friction with the atmosphere will be in the form of skin friction along the length of the beanstalk. Unlike skydivers, rocks and spacecraft, there's no wall of air to get compressed in front of the falling mass because (for the most part) the only thing in front of the falling mass is more beanstalk (which will be pulling down instead of pushing up as air would be). So the terminal velocity will be faster in this case than it would be for a rock.
The magic number for a counter-weight just on the far side of geostationary is about 140 times the mass of the beanstalk. 140 times the mass of something (anything) 45,000 kilometers long can't be easy to put there.
"Analysis shows that the proposed ribbon (of 1cm width below 10km altitude) would break at 71.5 m/s (159 mph) or a Category 5 hurricane. The proposed location of the ribbon is not in a hurricane or high wind area."
10 kilometers isn't even a drop in the bucket when you're talking about something going up at least to 45,000 kilometers (that's 4 orders of magnitude for those of you keeping score at home).
On top of that, every little bit more you put below geostationary orbit requires a lot more mass on the far side of geostationary (to counterbalance the weight). Yet again the inverse square bites you in the ass.
And your quoted passage reminds me of another point: wind speeds at height are a great deal faster than those on the ground. Just because there is neglibible wind on the surface doesn't mean the jet stream isn't whipping by at 60+ mph a few miles over your head.
I found my numbers (as well as some otherrants). If you put a huge couter-weight just on the far side of geostationary to hold the thing up, that counter-weight will need to mass about 140 times more than the mass of the beanstalk. While that may sound small, remember that even the smallest mass-per-meter gets pretty damned big when multiplied by 45 million. Not that it solves the problem of any breaks below the 45,000 km altitude...
Re:Good idea for nuclear waste?
on
Going Up?
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· Score: 1
"You could lanuch self-guiding ships full of the stuff straight into the sun...the sun sure wouldn't care."
Especially since, odds are, you'd miss the sun entirely. Moving something to the center of a gravity well is much more difficult than those who know nothing about orbital mechanics believe. You're more likely to have that waste whizing right by the sun, getting yanked back around by the sun's gravity and smacking right back into the earth.
Re:Impact on the environment (and the ground)
on
Going Up?
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· Score: 3, Interesting
"The energy gained by the falling cable will be at most its gravitational potential energy,"
Isn't that cute... but it's WRONG!
The top of the cable has something much more powerful acting on it than gravity alone: the bottom of the cable. The top will be moving just as fast as the bottom, accellerating downward just as much as the bottom. So you have a miles-high structure coming towards the earth at a relatively steady 9.8 m/s/s. This is far worse than mere gravity alone.
Everytime this has come up on Slashdot I've posted how foolish an idea this is (especially after 9/11), but nobody seems to listen to me.
1.) If it falls, bad things will happen. As I type this there are probably at least 10 posts to this article moderated way up that point out how "safe" this thing would be coming down. Every single one has two flaws:
It treats the beanstalk as a series of point particles as opposed to one connected strand
It neglects the fact that gravity is stronger towards the bottom of the beanstalk than the top
What does this mean? It means that, as the bottom comes down, the top will be yanked down faster than it would be by gravity alone. Want an analogy? Extend a tape measure to its full length. Let go and let it wind itself back up. Try not to cut your hand. And you want to build this on a large scale?
2.) People will now respond to this post saying that it won't fall down because the top will be in orbit. In order to keep the bottom of the beanstalk from whipping around the circumference of the earth every 90 minutes, you must be talking about putting the center of gravity into geostationary orbit. I've done the math. If you want to put the center of gravity of a cable with uniform density into geostationary orbit, it puts the top of your beanstalk well beyond lunar orbit (inverse square againt). And when the moon snaps off that top guess what happens.
Since this is a four-month old story, how about we discuss turning old HDDs into speakeasies instead? With hookers! And blackjack! In fact, forget the disk drives!
This is the same judge that had the balls (metaphoricly speaking) to tell the federal government that they had to release the names of the folks they're holding down in Camp X-Ray. Something tells me she's not so easily swayed...
Gliders of any sort aren't flying, they're falling with class (to paraphrase Buzz Lightyear). Note that they generally have specifications that say how many inches down they fall per feet of forwawrd flight.
As for ultralights, they only became possible with modern advances that maximized the hp-per-pound of modern Otto cycle engines.
You can do human-powered flight (somebody used it to fly over the English Channel in the 80's, but I'm too lazy to Google it), but it's going to be... interesting with such a small wingspan.
Human-powered flight with a smaller wingspan than most gasoline-powered planes? Ouch. IIRC, the guy who flew over the English Channel had something like 50 feet to play with.
"less than 450 lbs"
With a wingspan like that I would certainly hope so!
Slashdot Mirror
"Why is it that people find it more important to research into going to the moon then research on how to build toilets?"
Short answer: Because spending money on space research and development will ultimately help you make toilets (and plubming and sewage treatment plants and...) faster, better and cheaper.
No area of knowlege is wholly independent of everything else. Raising your technology and knowledge base in one field will ultimately raise those bases in all fields. Hell, for the most part nobody would have indoor plumbing if Rome didn't spend so much on defense. Strong army = more lands conquered = more lands to supply with clean water = need to invent aqueducts.
While I agree with the idea of spending a little on space R&D instead of blowing it all on social reform programs (who needs a bunch of people who can all get along hunky-dory if none of them have ever seen a telephone?)...
"How many Americans are without health insurance?
How many Americans are in jail?
How many Americnas suffer from obesity?"
My GOD man, do you see what you're calling "poor?" I've never really been out of the US but at least I know that being here in the thick of it can really skew your viewpoint. We live in a country where the vast majority of the people below the so-called "poverty line" own a car, a television and a microwave oven! Poor people in India don't even have a damned wall socket (if they have a wall!) to plug a television into, let alone the knowledge of how to use one (not like they've ever seen one before...).
What you're referring to as India's "middle class" is the slice of their population that can best relate to "middle class in the US." In the vast majority of the rest of the world, that's called "upper class."
"What I want to see is a nation or a group of nations going to the moon for the purpose of DOING something."
The "somethings" you refer to simply will not happen until space launches become cheap and/or plentiful. That doesn't happen overnight, economy of scale doesn't happen until you've built up the scale to begin with. And this is especially true with new technology, where you need to learn new construction and engineering methods before you can even think of large-scale production. When it comes to space exploration, we're still in the middle of the "research & development" stages (they don't call it space exploration for nothing).
Not that this means that R&D isn't profitable, however. It's just a slower turn-around than you seem to be demanding. Quite a big chunk of money was sunk into the Saturn V program, but 30+ years on we're still not done reaping the benefits in new technology and processes spun off from that project.
If you're so eager for a quick buck, why not do what everybody else just like you has done and day-trade some Enron stock? Unrealistic investment turn-around expectations go hand in hand with unrealistic accounting...
If she really loved you she'd be happier with a FDDI ring...
"Yes it is going to be 22,000 miles long. But it is going to be VERY thin,very little over all mass. There is going to be a VERY small amout of mass in this compared to the world trade towers."
./ seem to think it will (with nothing more than skin friction I don't see any reason not to believe that it would be coming down quite a bit faster than the speed of sound). And instead of grams falling down we'd have tons.
Why am I scared? Being one long strand, the top will accelerate as fast as the bottom. If we didn't have an atomsphere, that acceleration would go unchecked. 9.8 m/s/s over 45,000,000,000 meters gives you a velocity that's an appreciable fraction of the speed of light, a velocty about where a single gram would have about a kiloton of TNT in kinetic energy.
Yes, the atmosphere will slow it down, but not nearly as much as people here on
"should be humankind against itself, not each country against the other."
There's a difference?
No, I'm not trolling and I'm not being flippant. I fail to see how you can draw a line between "country vs. country" and "humanity vs. self," since countries are nothing more than a human institution.
"So your points are
1) It won't burn up because its moving slower than debris
2) It won't burn up because its moving faster than debris"
More like:
1.) It won't burn up because it starts below terminal velocity and accellerates, instead of starting above terminal velocity and having to be "braked" by the atmosphere.
2.) Its terminal velocity would be higher than for space debris because there is no air in front of the beanstalk, just more beansatlk.
"Next point. If there is nothing but beanstalk in front, it must be falling straight down.
That being the case, what's the problem? It'll fall straight down and leave a big pile of tangled ribbon at its base."
1000 tons falling straight down at obnoxious velocities (which it would be) into the ocean = tsunami.
"Why won't it just cut through the ocean like it does the air?" you're about to ask. Because sooner or later, it's going to come across something that will make it bend, be it the surface of an ocean rig that's at the bottom of the beanstalk or the bottom of the ocean, and once that initial kink comes into being at the landing point, that structure is going to whip around near the landing ponit like there's no tomrrow. Take a look at photos of trains that have jumped the rail and you'll notice that the front cars are all smashed up and can be thrown quite far from the rail because the cars behind it still have a lot of momentum and nothing else to stop it.
Sure, the structure will probably burn up in the lower atmosphere in that kind of motion at the surface of the earth, but whether it burns up or not that momentum has to go somewhere (so sayeth Newton), which will probably still spell out an atmospheric shockwave that I wouldn't want to be anywhere near.
"If, on the other hand, if falls over, then it will indeed build up a wall of air against its HUGE surface area."
If it falls sideways. Which it won't because of it's huge surface area. Nowhere to go but straight down at an obnoxious speed.
"Finally, the tensions of falling would very likely fragment the ribbon. In fact, the article says it will be designed for this to be the case."
If its strong enough to pull up multi-ton cargo, how will it break apart under its own weight?
"I can only imagine the forces acting on a 60 km long streamer."
The difference is that a streamer isn't under tension while a falling beanstalk would be. It couldn't flap like that because the bottom would be pulling it down and inertia would try to counteract that by "pulling up." It would probably flap quite a bit as it nears the end of the collapse, but it will be more like my tape measure analogy in its motion.
If you drop a sheet of paper edge down, it will fall down pretty fast until the bottom edge gets deflected to one side, causing the paper to curl into a U and maximizing the surface area for air resistance to play on. That couldn't happen with this ribbon because there is no bottom edge to get picked up, only more ribbon. This design will be all too aerodynamic.
"yet its surface area is 45,000,000m x .10m or 45 million square meters. Thats a lot of drag."
It would be if it were falling sideways, but it won't. The side of a mile-long freight train has a whole heck of a lot of surface area, but the only thing that really matters as far as wind resistance is the surface area of the front of the engine.
" This is one of the reasons there's no longer a green Mozilla logo,"
Then I must be color-blind. I keep on seeing a green, fire-breathing lizard on the splash screen whenever I start Moz. And there's another green lizard delivering mail when I start Moz mail.
See, they didn't name Mozilla after a Japanese movie monster, they named after a certain Blue Oyster Cult song. Big difference! :)
"Absolutely right. We shouldn't ever build any more tall buildings, or bridges, either. Yes, security is an issue, but it is for conventional rocketry as well--and we haven't stopped launching shuttles loaded with thousands of pounds of highly explosive material."
We're not talking about something 110 storeys tall. We're talking about something 22,000 miles tall. Orders of magitude difference here, with the potential to cause damage over areas measured in "square miles" instead of "city blocks."
"Except that as soon as the force of the falling cable below starts to really pull hard on the cable above, the cable will snap."
If it's strong enough to be able to pull up tons of payload, it's more than strong enough to be able to survive a mere 9.8 m/s/s acceleration.
"Well sure, but if you read the article, you would know that the cable will not be of uniform density. In principle, the cable can be very thin near the bottm end, and thicker in the middle."
When you're talking about something 22,000 miles long, and when talking about forces being exerted in geometric proportions, minor fluctuations in thickness like "tripling" or "by an order of magintude" won't make much difference. If you want to make a difference, the thickness better flare out like a trumpet bell.
"Using a counterweight just beyond geostationary orbit (as proposed, again in the article FAQ) will balance the weight of the cable below geostationary orbit."
1.) The counterweight will have to mass as much as 140 times the mass of the beanstalk (which itself will not be a negligible mass).
2.) All points in the beanstalk below geostationary altitude have a net force on it pointing downard. If there is a cut anywhere between the ground and 22,000 miles up, everything below the cut will come down. It doesn't matter if the cut is 20,000 miles up or "merely" 7 miles up, everything below the cut comes down.
"Consider, most space debris that "falls to earth" burns up in the atmosphere."
Consider that most space debris is moving extremely fast in relation to the atmosphere, while a falling beanstalk will start falling at rest.
Consider that most space debris comes down in "chunks," allowing a wall of air to be compressed in front of it. A falling beanstalk won't have a wall of air in front of it slowing it down, it will have yet more beanstalk in front of it pullint down faster.
Consider that, since there's nothing in front of a chunk of beanstalk beyond more beanstalk, the only friction you'll have is skin friction, allowing a much higher terminal velocity than you would have with "chunks."
"We even need to take special percautions to make sure out shuttles don't burn up on re-entry."
Look at the arrangement of the heat tiles on the shuttle. The bottom and leading edges are designed to withstand much more heat than the sides or the top. With a falling beanstalk, for all intents and purposes there are no "leading edges" or a "bottom," just more beanstalk.
Think of a train. Most of the wind resistance happens in front of the engine at the front. The engine plows through the air in front of it, and the cars behind it just move into the gap that was opened.
"I would be willing to bet the people working on this have much more scientific knowledge than you do sitting at home with your TI-83."
TI-92+, actually. Bit of a life-saver when it came to doing all those integrals involved in Fourier transforms in my partial differential equations class.
"I'm sure they've considered such things and take them into account. Do you honestly think a project like this would ever go up if we weren't 99% sure it would work?"
I don't see anything going up. I only see some website talking about the idea. Not everything on the internet is true or even feasable, even on Slashdot (which occasionally posts articles about perpetual motion machines).
"As currently proposed, the first Space Elevator is small! It is only 890 tons, less than half the mass of the Space Shuttle at launch."
Are we talking 1,780,000 pounds of weight, or 890,000 kilograms of mass? If we're talking weight, then its mass will be quite a bit higher than you'd expect (force of gravity drops off with altitude). If the number they spit out is the weight, then it would be a great deal more massive than the space shuttle.
"Your arguement is assuming the bottom pulls the top down (collapse), but what would happen if it were cut in half or breaks further up? Does the top spin into orbit and the bottom collapse?"
Orbital velocity for altitude X is inversely proportional to the altitude of X. In other words, the lower you are, the faster you have to be going in order to be in orbit.
However, for a beanstalk, every point below the top is actually going slower than the top (points toward the outside of a wheel are moving faster than points towards the inside, so a pebble stuck in the tire treads moves faster than the lug nuts). So those points aren't even going fast enough to be considered in orbit at the atltitude at the top, let alone their current altitude. Every point in the beanstalk between the bottom and geostationary orbit has a net force pulling down.
In other words, cut the ribbon anywhere between the ground and 22,000 miles up, and everything below the cut comes crashing down. Fly a plane into it at around 7 miles up, and you have seven miles of stuff coming down at you.
"The people working on this seem to think that their ribbon will burn up / disintegrate if it falls. But hey, what do they know?"
I'd certainly like to see their numbers. Things burn up in the atmosphere because of their high relative speed to it (the space shuttle, for example, hits the atmosphere going around mach 27 IIRC). The beanstalk will start falling from a dead stop in relation to the ground. It will accellerate to terminal velocity for the lower portion and probably continue down at that constant velocity (which will be pretty fast, and when squared and multiplied by half the mass of something 45,000,000 meters long, will be a frightening amount of kinetic energy).
Besides, most of the friction with the atmosphere will be in the form of skin friction along the length of the beanstalk. Unlike skydivers, rocks and spacecraft, there's no wall of air to get compressed in front of the falling mass because (for the most part) the only thing in front of the falling mass is more beanstalk (which will be pulling down instead of pushing up as air would be). So the terminal velocity will be faster in this case than it would be for a rock.
The magic number for a counter-weight just on the far side of geostationary is about 140 times the mass of the beanstalk. 140 times the mass of something (anything) 45,000 kilometers long can't be easy to put there.
"Analysis shows that the proposed ribbon (of 1cm width below 10km altitude) would break at 71.5 m/s (159 mph) or a Category 5 hurricane. The proposed location of the ribbon is not in a hurricane or high wind area."
10 kilometers isn't even a drop in the bucket when you're talking about something going up at least to 45,000 kilometers (that's 4 orders of magnitude for those of you keeping score at home).
On top of that, every little bit more you put below geostationary orbit requires a lot more mass on the far side of geostationary (to counterbalance the weight). Yet again the inverse square bites you in the ass.
And your quoted passage reminds me of another point: wind speeds at height are a great deal faster than those on the ground. Just because there is neglibible wind on the surface doesn't mean the jet stream isn't whipping by at 60+ mph a few miles over your head.
I found my numbers (as well as some other rants). If you put a huge couter-weight just on the far side of geostationary to hold the thing up, that counter-weight will need to mass about 140 times more than the mass of the beanstalk. While that may sound small, remember that even the smallest mass-per-meter gets pretty damned big when multiplied by 45 million. Not that it solves the problem of any breaks below the 45,000 km altitude...
"You could lanuch self-guiding ships full of the stuff straight into the sun...the sun sure wouldn't care."
Especially since, odds are, you'd miss the sun entirely. Moving something to the center of a gravity well is much more difficult than those who know nothing about orbital mechanics believe. You're more likely to have that waste whizing right by the sun, getting yanked back around by the sun's gravity and smacking right back into the earth.
"The energy gained by the falling cable will be at most its gravitational potential energy,"
Isn't that cute... but it's WRONG!
The top of the cable has something much more powerful acting on it than gravity alone: the bottom of the cable. The top will be moving just as fast as the bottom, accellerating downward just as much as the bottom. So you have a miles-high structure coming towards the earth at a relatively steady 9.8 m/s/s. This is far worse than mere gravity alone.
1.) If it falls, bad things will happen. As I type this there are probably at least 10 posts to this article moderated way up that point out how "safe" this thing would be coming down. Every single one has two flaws:
- It treats the beanstalk as a series of point particles as opposed to one connected strand
- It neglects the fact that gravity is stronger towards the bottom of the beanstalk than the top
What does this mean? It means that, as the bottom comes down, the top will be yanked down faster than it would be by gravity alone. Want an analogy? Extend a tape measure to its full length. Let go and let it wind itself back up. Try not to cut your hand. And you want to build this on a large scale?2.) People will now respond to this post saying that it won't fall down because the top will be in orbit. In order to keep the bottom of the beanstalk from whipping around the circumference of the earth every 90 minutes, you must be talking about putting the center of gravity into geostationary orbit. I've done the math. If you want to put the center of gravity of a cable with uniform density into geostationary orbit, it puts the top of your beanstalk well beyond lunar orbit (inverse square againt). And when the moon snaps off that top guess what happens.
To sum up: Not on my planet!
Since this is a four-month old story, how about we discuss turning old HDDs into speakeasies instead? With hookers! And blackjack! In fact, forget the disk drives!
This is the same judge that had the balls (metaphoricly speaking) to tell the federal government that they had to release the names of the folks they're holding down in Camp X-Ray. Something tells me she's not so easily swayed...
Gliders of any sort aren't flying, they're falling with class (to paraphrase Buzz Lightyear). Note that they generally have specifications that say how many inches down they fall per feet of forwawrd flight.
As for ultralights, they only became possible with modern advances that maximized the hp-per-pound of modern Otto cycle engines.
You can do human-powered flight (somebody used it to fly over the English Channel in the 80's, but I'm too lazy to Google it), but it's going to be... interesting with such a small wingspan.
"Less than 30 feet wide,"
Human-powered flight with a smaller wingspan than most gasoline-powered planes? Ouch. IIRC, the guy who flew over the English Channel had something like 50 feet to play with.
"less than 450 lbs"
With a wingspan like that I would certainly hope so!