Even laser powered launch vehicles need fuel. Remember Newton's laws?
Laser powered launch can use the atmosphere- but only initially- but pretty soon they have to leave it and do the bulk of their acceleration outside; you need to do mach 25 to reach orbit, and nobody has ever achieved more than mach 6 in the atmosphere.
The big advantage of laser powered launch is that it doesn't need to carry the power supply with it. This means that the fuel can be heated far hotter than it would normally- for example pure hydrogen can be used- this means that the exhaust velocity is much higher than if hydrogen/oxygen was used as in the space shuttle (the oxygen is heavy and slows the exhaust speed down). That means that much less fuel is required; however you still need plenty of fuel.
It's not significantly radioactive until they turn on the reactor; until it becomes radioactive it's very safe; it wouldn't matter if it blew up.
They won't turn on the reactor until it reaches orbit, and then it becomes hot. Once it reaches orbit, if it blew up, the remnants would stay in orbit for extremely long periods.
Besides, personally, I've been to Florida. It's a big swamp, and America doesn't seem to have a clue how to handle it, they should probably vacate the area:-)
The headline (you did RTFS, right?) says it all: "Rice engineers make first pure nanotube fibers"
Yeah, I did, and I've read most of the NACA research papers on space elevators too. Please tell me where, when you RTFS, where it says that the material they made had a strength/weight ratio sufficient to make a Space Elevator. Until that has been demonstrated it's material science; which is really very much more basics physics research than engineering.
The nanotubes are sticky and bond well with themselves.
Absolutely. But the fur-balls haven't previously achieved anything like their full strength potential.
Creating nanotubes is dead-on easy.
Yup. But the problem is creating 120GPa nanotube cable- nobody has ever done that so far.
You will end up with 100% pure nanotube rope or cable at the end of the process.
True, but that doesn't make it strong. Furballs have not massive strength. The microstructure of the 100% rope is completely critical. The nanotubes have to be almost perfectly aligned along the length of the cable, with just enough crossconnects to keep the cable together. Any nanotubes that are at a significant angle weaken the cable.
I mean, take steel. Steel is orders of magnitude weaker than single filaments of steel. Or glass, same thing- that's why glass fiber is so strong in fact (single filaments are usually much, much stronger than bulk material.) Until somebody can show that carbon nanotubes made in this way lose less than 25% of their theoretical strength, I think I'm pretty justified in being atleast a little skeptical; albeit hopeful. As I noted the article didn't claim anything as regards strength/weight ratio.
I admit it sounds very promising, particularly since this is similar to how Kevlar is made...
Conventional rocketry will never be subject to the economy of scale. Too expensive. SE will.
So, if I understand you correctly you are arguing that conventional rocketry will never be cheap because the space launch market it is too small. But the space elevator will be cheaper and so will create a larger space launch market... for conventional rocketry too.
The economies of scale apply just as much to conventional rocketry as to the space elevator- as I say, I've seen the figures for both space elevators and rocketry and it is much more arguable than you seem to think- the underlying, per launch, costs of both are very small indeed (maybe $50/kg); in both cases they are hidden behind the fact you need to borrow billions of dollars to build them in the first place.
Ultimately, the Space Elevator may end up cheaper, but it's not a slam-dunk; and frankly I wouldn't want to bet on it; but I am by no means anti-elevator.
And you're very definitely right about the interplanetary aspects of space elevators; even if it winds up more expensive (it doesn't look like it at the moment, but there's plenty of potentially fatal flaws with them) they are still very much worth building.
If you had a super-duper composite material to build a space elevator, don't you think getting the mass fraction for a single stage to orbit spacecraft would be a piece of cake?
Possibly. Might even be able to get away with a pressure fed rocket.
Graphite composite was supposed to be the revolution in mass fraction that was going to make the X-33/Venture Star workable, and the only thing came down like a house of cards when the composite cryo fuel tank was not all it was cracked up to be.
Yeah, well, they tried to make an asymmetric, composite, hydrogen tank. One project manager resigned, mainly because of that. If they had gone for cylindrical or spherical they might well have flown.
All elevators have a certain maximum design load, determined mainly by the thickness of the cable. So it can't carry more than a certain total weight at any one time; so launching every two minutes is probably not possible.
In theory you can make the cable thicker, but this takes time and expense. As an example of one of the issues, since it's thought that the elevator cable will be occasionally cut by meteorites or space junk, it probably doesn't pay you to make it too thick (ultimately you'd spend all your time thickening the cable and then you'd get no use out of it before it falls down.)
I'd be willing to spend two weeks in a box to get to space on a budget.
Yes, well, another problem is that the box goes right through the worst of the Van Allen belts. This means that the radiation is pretty intense; and you'd be pretty fried when you reached the top (by way of contrast the Apollo astronauts were OK, because they went much more quickly through the belts, but even so, they had about 1% of a fatal dose).
Now, it is possible to shield against the radiation, but the thickness is measured in feet, and the weight of the shielding is very considerable- it's looking like early cargoes will not be people.
Nanotube strength is more than you need. Much more. Pure carbon nanotube strands are strong enough to make a completely untapered elevator, all by themselves. (300 GPa tensile strength).
Nope. That's a theoretical maximum strength; but the theory is probably wrong. Current experimental strength of short fibers is about 120 GPa, and that's only just what you'd need to do this (about 60 GPa is needed, plus a safety factor of say 2).
What you do is you build a composite fiber, just like you have fiberglass, or Kevlar fibers - you dope some composite with nanotubes to increase their strength.
Not quite. If you dope a plastic with nanotubes you'd end up with a material whose strength and weight were dominated by the polymer. That would be wayyyy too heavy and weak. The idea is that you have to use an absolute bare minimum of glue to stick the nanotubes fibers together. Trouble is no-one knows how to do this right now with adequate strength; nanotubes are slippery and particularly hard to glue; and as noted, we don't have a great deal of strength to play with- we need a safety factor for practical reasons.
Kilometer-long doped CNT fibers have already been produced. No, they're not as strong as you need. Yes, that's being worked on, and yes, it's an engineering problem, not a fundamental flaw.
Those fibers aren't even as strong as Kevlar. So, no, it's still a research problem. The engineering begins when we have a cable even a few feet long; of the right strength/weight ratio. Until then- engineers and financiers must hang fire.
It's not quite as simple as whether it can be built though. I mean, look at Concorde; just building something successfully is not enough.
A space elevator would be more expensive than Concorde to develop and build, and because the asking price to send a payload up it is pretty much the build price divided by how often it is used (plus profit), it may very well not turn out that cheap; I've seen estimates as high as $500-$1000/kg- fairly cheap by todays standards (around $2500-$8000/kg), but probably well within reach of conventional rocketry (and conventional rockets improve to if they can use nanotubes).
Basically, if it takes 2 weeks to climb the elevator, you can't launch all that often, and that pushes up the price.
Just because something is made of nanotubes doesn't make it strong, it depends on how they are laid out. The press release sounds good, but until they publish the measured strength/weight ratio of a few feet of their manufactured cable. (The data might be in the paper, but I haven't bought it. Anyone?)
Actually, British Airways managed to make Concorde profitable in the 80s, and it stayed that way until the twin towers. It's pretty easy to make an aircraft profitable when it's unique.
Not only did they make tens of millions on the aeroplane; but the knock-on prestige effect on the airline as a whole was an incredible boost to the rest of the business.
Air France on the other hand, never managed to make the business profitable. I'm unclear how they managed to mismanage such a unique resource which they could pretty much charge any price for; but their lack of profitability doubtless contributed to the end of commercial Concorde flights.
Of course the original manufacturers of the aircraft made big, big losses; but that was partly due to what amounts to protectionism in the American market.
The fabric wasn't merely flammable, it contained both aluminum powder and iron oxide. That combination is called 'thermite', and it needs no oxygen to react; so the fabric was approximately explosive.
Back to my point though...if you have a wireless network, then be a conscientious wireless user and keep to channels 1, 6 or 11.
It's not as simple as that though. The reason you have 11 channels is that in certain circumstances it's ok to overlap channels. For example, in an office block you might use 1,6,11 on the ground floor, and say, 4,9 on the second floor. Provided the flooring gives some degree of shielding, but not total shielding, the interference would be less than using 1,6,11 on each floor. The optimum pattern depends on the distances and materials used in the building; and that can only be determined by a site survey.
(For example, the last building I worked in had metal floors and metallic silvering on the windows, clearly 1,6,11 was fine on every floor.)
It's not a conspiracy theory when they've actually done stuff like it before, and in any case it's not a conspiracy when it's only one party involved.
"The jobs not done until Borland won't run."
I forget whether they were convicted for that one. I think they were. Didn't really matter much though; by the time the court case was done, Borland was gone.
So Fox didn't threaten to sue itself, but is the new rule against fake news crawls real, or was it part of the joke as well?
No, that's real. Actually the new rule is about forbidding talking about Fox's internal rules. But they'll deny that if you ask them about it, which proves it really, doesn't it?
Something to hide? I prefer to think of a police state as somebody to hide from.
The gits are very probably already recording who and when I call, recording my internet usage, shopping items, email headers and so on. And they probably scan all transoceanic phone calls for keywords, and may well be recording them now the cost of storage is so low.
And I say this without any trace of paranoia- they record these things for the whole country pretty much anyway.
That's actually not entirely atypical; if you just ask people cold whether they think they are a good idea. Which is presumably why the government chose this route. However when people are actually forced to look at the issue in more detail; they mostly change their mind- the statistics typically end up more like 60% against.
Noteably, this was roughly the result of the consultation period (presumably the people that bothered to reply to it had thought about the issues to some extent, and so were mostly against it) and there have been debates on TV (polling before debate: most people think it's a good idea, polling after: most don't.)
Wow! Really? That's good news. No, and I haven't heard anything about the Microsoft Linux distro that was due at that time, do you think that that could have slipped out even further now?:-)
As it says... they do NOT support Linux but are not going to do anything to block Linux from running under it.
That isn't quite right. The Microsoft spokeswoman said:
But Microsoft has optimized the product around key customer needs, which is helping them address application compatibility issues they are having with older, custom-written applications when they are buying new PCs and upgrading to newer operating systems, she said.
Translation: we're going to optimise it to run what we want it to run, if it deliberately^h^h^h^h^h^h^h^h^h^h^h^h accidentally turns out that Linux runs like a dog under our VM feel free to raise a problem ticket, and we'll get around to it sometime before Hell freezes over, maybe.
The bottom line of this is that this feature was good for the producer, and bad for the customer (potentially very bad if it messes up something on an intranet).
Trouble is, we buy products because it is good for us, not good for the manufacturer. They seem to have lost sight of it, although may have realised their mistake (or equally likely they haven't realised it, but it's just they dislike the bad publicity).
Either way, it speaks volumes of their corporate decision making. In my experience, corporate decision making is at best, of highly variable quality; managers try to come up with just slightly too clever schemes that try to raise profits at the (non financial) expense of the customer. These things add negative qualities to the product. Why would you ever want to do that?
You could easily sue these businesses for false advertising.
Suing is never easy or risk free. You can win and still be stuck with enormous legal costs, or you might be awarded costs, maybe. Or you lose, in which case you would lose big. In any case the lawyers win. And suing a well-healed corporation is even more risky, they can afford expensive lawyers that are more likely to win (if nothing else), or they can just buy you off (in which case the advert stands and other, less knowing people will get ripped off.)
Personally I much prefer an 'umpire' to make the decisions- it's cheaper alround that way- sure they don't always make the absolute best decisions, but like an umpire in sport, they're usually pretty good and very rarely terrible.
Too right man! Advertisers never, ever tell untruths or half-truths, and can be absolutely trusted to use free speech to sell products on entirely reasonable and honourable grounds.
The idea that advertisers might be accused of lying sickens me to my stomach- free speech is much more important than the negative outcome of any TV ad- no matter how much people are lied to and end up spending money on falsely advertised products! They should have known the adverts were lying!
These censorous, fascist and outright communist Europeans need to learn a thing or two about the right way to let people uphold American rights just like all God-fearing American people in America, where there's no molly-coddling and everyone knows the adverts are full of it!
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Laser powered launch can use the atmosphere- but only initially- but pretty soon they have to leave it and do the bulk of their acceleration outside; you need to do mach 25 to reach orbit, and nobody has ever achieved more than mach 6 in the atmosphere.
The big advantage of laser powered launch is that it doesn't need to carry the power supply with it. This means that the fuel can be heated far hotter than it would normally- for example pure hydrogen can be used- this means that the exhaust velocity is much higher than if hydrogen/oxygen was used as in the space shuttle (the oxygen is heavy and slows the exhaust speed down). That means that much less fuel is required; however you still need plenty of fuel.
It's not engineering, it's research. It so happens that the researchers here are engineers and chemists, but it's still research.
They won't turn on the reactor until it reaches orbit, and then it becomes hot. Once it reaches orbit, if it blew up, the remnants would stay in orbit for extremely long periods.
Besides, personally, I've been to Florida. It's a big swamp, and America doesn't seem to have a clue how to handle it, they should probably vacate the area :-)
Yeah, I did, and I've read most of the NACA research papers on space elevators too. Please tell me where, when you RTFS, where it says that the material they made had a strength/weight ratio sufficient to make a Space Elevator. Until that has been demonstrated it's material science; which is really very much more basics physics research than engineering.
Absolutely. But the fur-balls haven't previously achieved anything like their full strength potential.
Creating nanotubes is dead-on easy.
Yup. But the problem is creating 120GPa nanotube cable- nobody has ever done that so far.
You will end up with 100% pure nanotube rope or cable at the end of the process.
True, but that doesn't make it strong. Furballs have not massive strength. The microstructure of the 100% rope is completely critical. The nanotubes have to be almost perfectly aligned along the length of the cable, with just enough crossconnects to keep the cable together. Any nanotubes that are at a significant angle weaken the cable.
I mean, take steel. Steel is orders of magnitude weaker than single filaments of steel. Or glass, same thing- that's why glass fiber is so strong in fact (single filaments are usually much, much stronger than bulk material.) Until somebody can show that carbon nanotubes made in this way lose less than 25% of their theoretical strength, I think I'm pretty justified in being atleast a little skeptical; albeit hopeful. As I noted the article didn't claim anything as regards strength/weight ratio.
I admit it sounds very promising, particularly since this is similar to how Kevlar is made...
(Crossing fingers).
So, if I understand you correctly you are arguing that conventional rocketry will never be cheap because the space launch market it is too small. But the space elevator will be cheaper and so will create a larger space launch market... for conventional rocketry too.
The economies of scale apply just as much to conventional rocketry as to the space elevator- as I say, I've seen the figures for both space elevators and rocketry and it is much more arguable than you seem to think- the underlying, per launch, costs of both are very small indeed (maybe $50/kg); in both cases they are hidden behind the fact you need to borrow billions of dollars to build them in the first place.
Ultimately, the Space Elevator may end up cheaper, but it's not a slam-dunk; and frankly I wouldn't want to bet on it; but I am by no means anti-elevator.
And you're very definitely right about the interplanetary aspects of space elevators; even if it winds up more expensive (it doesn't look like it at the moment, but there's plenty of potentially fatal flaws with them) they are still very much worth building.
Possibly. Might even be able to get away with a pressure fed rocket.
Graphite composite was supposed to be the revolution in mass fraction that was going to make the X-33/Venture Star workable, and the only thing came down like a house of cards when the composite cryo fuel tank was not all it was cracked up to be.
Yeah, well, they tried to make an asymmetric, composite, hydrogen tank. One project manager resigned, mainly because of that. If they had gone for cylindrical or spherical they might well have flown.
In theory you can make the cable thicker, but this takes time and expense. As an example of one of the issues, since it's thought that the elevator cable will be occasionally cut by meteorites or space junk, it probably doesn't pay you to make it too thick (ultimately you'd spend all your time thickening the cable and then you'd get no use out of it before it falls down.)
I'd be willing to spend two weeks in a box to get to space on a budget.
Yes, well, another problem is that the box goes right through the worst of the Van Allen belts. This means that the radiation is pretty intense; and you'd be pretty fried when you reached the top (by way of contrast the Apollo astronauts were OK, because they went much more quickly through the belts, but even so, they had about 1% of a fatal dose).
Now, it is possible to shield against the radiation, but the thickness is measured in feet, and the weight of the shielding is very considerable- it's looking like early cargoes will not be people.
Nope. That's a theoretical maximum strength; but the theory is probably wrong. Current experimental strength of short fibers is about 120 GPa, and that's only just what you'd need to do this (about 60 GPa is needed, plus a safety factor of say 2).
What you do is you build a composite fiber, just like you have fiberglass, or Kevlar fibers - you dope some composite with nanotubes to increase their strength.
Not quite. If you dope a plastic with nanotubes you'd end up with a material whose strength and weight were dominated by the polymer. That would be wayyyy too heavy and weak. The idea is that you have to use an absolute bare minimum of glue to stick the nanotubes fibers together. Trouble is no-one knows how to do this right now with adequate strength; nanotubes are slippery and particularly hard to glue; and as noted, we don't have a great deal of strength to play with- we need a safety factor for practical reasons.
Kilometer-long doped CNT fibers have already been produced. No, they're not as strong as you need. Yes, that's being worked on, and yes, it's an engineering problem, not a fundamental flaw.
Those fibers aren't even as strong as Kevlar. So, no, it's still a research problem. The engineering begins when we have a cable even a few feet long; of the right strength/weight ratio. Until then- engineers and financiers must hang fire.
A space elevator would be more expensive than Concorde to develop and build, and because the asking price to send a payload up it is pretty much the build price divided by how often it is used (plus profit), it may very well not turn out that cheap; I've seen estimates as high as $500-$1000/kg- fairly cheap by todays standards (around $2500-$8000/kg), but probably well within reach of conventional rocketry (and conventional rockets improve to if they can use nanotubes).
Basically, if it takes 2 weeks to climb the elevator, you can't launch all that often, and that pushes up the price.
Just because something is made of nanotubes doesn't make it strong, it depends on how they are laid out. The press release sounds good, but until they publish the measured strength/weight ratio of a few feet of their manufactured cable. (The data might be in the paper, but I haven't bought it. Anyone?)
Something of a misconception. In actual fact an elevator cable has to be attached to the elevator car for the system to work correctly.
Not only did they make tens of millions on the aeroplane; but the knock-on prestige effect on the airline as a whole was an incredible boost to the rest of the business.
Air France on the other hand, never managed to make the business profitable. I'm unclear how they managed to mismanage such a unique resource which they could pretty much charge any price for; but their lack of profitability doubtless contributed to the end of commercial Concorde flights.
Of course the original manufacturers of the aircraft made big, big losses; but that was partly due to what amounts to protectionism in the American market.
The fabric wasn't merely flammable, it contained both aluminum powder and iron oxide. That combination is called 'thermite', and it needs no oxygen to react; so the fabric was approximately explosive.
It's not as simple as that though. The reason you have 11 channels is that in certain circumstances it's ok to overlap channels. For example, in an office block you might use 1,6,11 on the ground floor, and say, 4,9 on the second floor. Provided the flooring gives some degree of shielding, but not total shielding, the interference would be less than using 1,6,11 on each floor. The optimum pattern depends on the distances and materials used in the building; and that can only be determined by a site survey.
(For example, the last building I worked in had metal floors and metallic silvering on the windows, clearly 1,6,11 was fine on every floor.)
"The jobs not done until Borland won't run."
I forget whether they were convicted for that one. I think they were. Didn't really matter much though; by the time the court case was done, Borland was gone.
No, that's real. Actually the new rule is about forbidding talking about Fox's internal rules. But they'll deny that if you ask them about it, which proves it really, doesn't it?
The gits are very probably already recording who and when I call, recording my internet usage, shopping items, email headers and so on. And they probably scan all transoceanic phone calls for keywords, and may well be recording them now the cost of storage is so low.
And I say this without any trace of paranoia- they record these things for the whole country pretty much anyway.
Noteably, this was roughly the result of the consultation period (presumably the people that bothered to reply to it had thought about the issues to some extent, and so were mostly against it) and there have been debates on TV (polling before debate: most people think it's a good idea, polling after: most don't.)
All in all, police state here we come.
They've done it before, and far worse; and got away with it every time.
Wow! Really? That's good news. No, and I haven't heard anything about the Microsoft Linux distro that was due at that time, do you think that that could have slipped out even further now? :-)
That isn't quite right. The Microsoft spokeswoman said:
But Microsoft has optimized the product around key customer needs, which is helping them address application compatibility issues they are having with older, custom-written applications when they are buying new PCs and upgrading to newer operating systems, she said.
Translation: we're going to optimise it to run what we want it to run, if it deliberately^h^h^h^h^h^h^h^h^h^h^h^h accidentally turns out that Linux runs like a dog under our VM feel free to raise a problem ticket, and we'll get around to it sometime before Hell freezes over, maybe.
Trouble is, we buy products because it is good for us, not good for the manufacturer. They seem to have lost sight of it, although may have realised their mistake (or equally likely they haven't realised it, but it's just they dislike the bad publicity).
Either way, it speaks volumes of their corporate decision making. In my experience, corporate decision making is at best, of highly variable quality; managers try to come up with just slightly too clever schemes that try to raise profits at the (non financial) expense of the customer. These things add negative qualities to the product. Why would you ever want to do that?
Suing is never easy or risk free. You can win and still be stuck with enormous legal costs, or you might be awarded costs, maybe. Or you lose, in which case you would lose big. In any case the lawyers win. And suing a well-healed corporation is even more risky, they can afford expensive lawyers that are more likely to win (if nothing else), or they can just buy you off (in which case the advert stands and other, less knowing people will get ripped off.)
Personally I much prefer an 'umpire' to make the decisions- it's cheaper alround that way- sure they don't always make the absolute best decisions, but like an umpire in sport, they're usually pretty good and very rarely terrible.
The idea that advertisers might be accused of lying sickens me to my stomach- free speech is much more important than the negative outcome of any TV ad- no matter how much people are lied to and end up spending money on falsely advertised products! They should have known the adverts were lying!
These censorous, fascist and outright communist Europeans need to learn a thing or two about the right way to let people uphold American rights just like all God-fearing American people in America, where there's no molly-coddling and everyone knows the adverts are full of it!