The resistivity of graphite fibers varies quite a bit. For example the venerable Toray T300 fibers are listed around 2000 microohms-cm, while Union Carbide P100's are around 250. You have to be careful because bulk carbon is different. Aluminum is about 2.7 in those units. Graphite can be specially made to have lower resistivity but I'll use the 250 value for ROM calcs. Use a 16km cable length.
So if we assume a 1 in^2 cable section (6 cm^2) and they can manage to get 15kV, the current for 40MW is 2667A. The total resistance of a 16km cable would be 250e-6/6*16000*100=67 ohms. The power loss would be 2667^2*67 = 491MW. So this ROM calc shows it obviously wouldn't work because you would need a ridiculously fat cable.
The paper they wrote talks about an Vectran/aluminum conductor. Let's look at that quickly. To get 10% cable losses the cable resistance would have to be 4e6/2667^2 =.5 ohms. Using resistivity=2.7e-6 ohm-cm the cable section would have to be 2.7e-6*16000*100/.5=4.3 cm^2. The volume would be 16000*.00043=6.9m^3 and the mass 2700*6.9=18630kg (19 tonnes). So there you have 40 tonnes at least for the conductors, 60 if they use 3-phase transmission.
Vectran, Spectra, and Aramid fibers are all similar crystalline organic fibers. Ultimate tensile strength is usually around 3GPa, but you would probably use at most half that for a real world application. So to hold a 19000kb cable where F=19000*10=190000N, A=190000/1.5e9=1.27e-4m^2. Density is around 1500kg/m^3 so the Vectran mass/cable would be 1.27e-4*16000*1500=3048kg or 3 tonnes. So 6 or 9 tonnes total. Just to hold the cable weight.
The aerodynamic loads are hard to figure. Let's do something really rough. In their paper they quote energy density at altitude of 20kW/m^2. Air density is at 10km is.4kg/m^3. Wind velocity would be (20000/.4)^.5=223m/s. Assume they do really well and get 50% of the energy out, the rotor projected area has to be 40000000/10000=4000m^2 or a square 63m on a side. Energy density goes with the square of V, so the delta V would be 223*(1-.707) = 65m/s. Using the momentum equation, the force per m^2 is F=rho*V*delta V=.4*223*65=5798N. The total force would be 5798*4000=23,192,000N. Thats 5 million pounds.
This is the sort of time you wish you had someone to check your calcs, because that seems high. But if it is right, that would need a Vectran cable 1.27e-4*23000000/190000=.015m^2 area or about 7cm in diameter. Well, that looks maybe doable after all.
This is true, I did some calculations on the other thread that showed aluminum probably couldn't be made to work and graphite probably could. The property you need is a high tensile strength/density ratio. Kevlar and Specta also have very high ratios, so they could be used as the load carrying reinforcement.
The advantage of graphite is that it is conductive and could maybe be used as the conductor too so you wouldn't need the aluminum. That would add risk to the project because it may never have be done before.
A ROM calc showed that graphite conductive cables would weight about 40 tons. A reinforced aluminum cable might be double that. These are not small numbers, and the weight you add to the cables has to be held up by the platform, which takes away from the power generation.
None of that means it couldn't be feasible, practical, or economical, it just looks really hard to do.
I'm happen to be an expert in aircraft structures and based on what I said in the original thread, I really wonder if they know what they are talking about. The Economist article talks about aluminum tethers and from what I can tell such cables would be physically impossible. That is basic stuff to get wrong.
Secondly, a winged platform with horizontal-axis turbines would make more sense. Their helicopter-ish layout uses a lot of rotor structure to present a little area to the airflow. You cannot tilt the platform to present more rotor area to the airflow because the lift vector has to be parallel to the anchor cables where they attach to the vehicle. Those cables which will be nearly vertical, that is basic catenary physics and there is nothing you can do about it unless you use other lift vehicles to hold the tether up (the way high-altitude kites work.)
Thirdly, the jet stream meanders around. Are they thinking about moving the turbines to follow the jet stream? How would that work? Would they move their restricted airspace region to follow them? And what kind of ground station would be massive enough to bear the large forces this thing generates and be portable enough to drive on roads?
Fourthly, it will have either be certified by the FAA or will have to fly over uninhabited areas. Flying things crash, they always crash, and a 10 kilometer cable whipping down on you from the sky is a nasty thought. Certification has killed more than a few projects that otherwise seemed like good ideas.
I'm not saying it's all impossible. Just unlikely.
It just so happens I have a bit of experience designing aluminum and graphite aircraft parts, and my brother is an EE so by osmosis I know enough electrical stuff to fake some calculations.
Thing is, for a constant-diameter cable of a given density and a given strength, the length that can hang under it's own weight is an intrinsic property. For example, I would guess electrical grade (fairly pure) aluminum has a strength of at most 10,000 psi, and a density of.1 lb/in^3. The maximum hanging length would be 1.6 miles. If you taper it you might double that.
That doesn't even include the pulling loads from the monster at the top, which would be large. So aluminum is out.
Carbon nonotubes are hocus-pocus for real-world stuff right now, so forget about that.
However, graphite fibers conduct electricity not too bad, they might work, and they have fabulous strength in tension.
You could probably load a carbon fiber cable up to at least 100,000 psi, and it's density is.06 lb/in^3. That gives a hanging length of 26 miles. That looks better.
Let's fake an electrical calculation to see if it has a chance to work as a transmission cable.
If we use 10KV then for 10MW we have 1000A. The resistivity of graphite fibers is about 4 micro ohms-in. So lets say we make a 1 in^2 section cable, the resistance would be 4 micro-ohms/inch. A 10 mile length would have a resistance of 2.5 ohms and the power dissipation would be 2,500 watts. Surely we could dissipate that over about 10 miles without it overheating the cable.
The weight of the cable would be 1*10*5280*12*.06 = 38,016 lbs (19 tons). Since you need two of them, the total cable-weight load on the monster would be 38 tons.
Add to that the air loads of the horizontal windmill action (which is the whole point of the stupid thing) and what I'll call the catenary multiplier effect for lack of a better term, and the actual load on the cables will probably be something on the order of 100 tons. Since the cables were only stressed to about half their capabilities by the hanging load, it might work.
But you see why I call it a monster. The rotors have to genterate 100 tons of (inclined) lift.
(I used a 10 mile cable length throughout because while the altitude is about 6 miles, the monster is blown sideways and the cable hangs in a catenary shape.)
Toughness has both a qualitive and quantitive meaning. As someone mentioned before, it can be thought of as the amount of energy (the area under the stress-strain curve) required to fail the material. As a general rule, materials in the same class show an inverse relationship between strength and toughness.
It also has a quantitative definition that relates to crack sensitivity. Fracture toughness has a specific definition that relates to the strength of the stress singularity at a crack tip required to make the crack propogate unstably (i.e. break.)
The magnitude of the stress singularity is called the stress intensity K and its units are ksi*inches^.5 (MPa*m^.5). It varies with the applied stress and the geometry and size of the crack.
Stress intensity is the whole basis of fracture mechanics, which is a fairly new discipline only understood since about the 1950's. If you know the fracture toughness of a material you can calculate how big a crack any given thing made out of that material can withstand under a given load. Thats why planes are safe, they are designed to withstand cracks that can be easily found during inspection. Pressure vessels are designed to stand big enough cracks that they will start to leak before then burst so the problem becomes evident before they go boom. This kind of analysis is called damage tolerance.
It's also used to predict how fast cracks will grow under cyclic load. By testing you can develop the so called da/dN vs delta K curves that let u predict how long, for example, and airplane can fly before a crack that can't be found by inspection grows to a size that can be found. That tells you how often you should go look.
But it still advises local children not to work in fields at the explosion site, nor eat their snails -- which are a local delicacy.
How come whenever someone in a faraway land eats something odd, we call it a delicacy. I bet the people in the next town over from Palomares say "Those guys from Palomeres, they dig up SNAILS and EAT THEM. Hillbillies."
This Spanish-fishing-village-nuclear-bomb thing reminds me of an old film called Day of the Fishes. I wonder if they are connected.
I belive the part of the document that may draw attention is this:
Provide space capabilities to support continuous, global strategic and tactical warning as well as multi-layered and integrated missile defenses;
That will be seen by some as laying the groundwork for, or at least being consistent with, the weaponization of space in support of National Missile Defense. The "multi-layered" term means "not just ground-based interceptors."
Most displacement-based structural finite element packages feature grid points that characterize motion with six parameters: X, Y, Z, RX, RY, RZ. This is because beam and plate elements are abstractions to reality that introduce the concept of "bending". Solid elements are "less" abstracted and often don't support the rotational degrees of freedom.
Just to say, using those six degrees of freedom at a point is a way to reproduce "reality" in a certain abstracted way.
Well all right, I can see you will insist on hammering away at your sad little misconceptions until someone who actually knows sets you right, and even then I have little hope, but for what little its worth here's some truth.
Canada and the USA spend similarly on social programs, with the exception of health care. The US actually spends much more on health care (with similar overall outcomes) due to the fractured and inefficient nature of your system. But that doesn't get counted as social spending because it's not a government program.
As a percentage of GDP, US defence spending is about 4%, Canada is approaching 2% this year. Canada is on the high side of NATO defence/GDP spending now though in the last decade it was lower. Mostly due to scarey deficits and debts we had to fix. Personally I was never comfortable with those low spending levels, but that's an internal matter for us Canadians to sort out, isn't it?
The total Canadian Federal budget is about the same size as the American defence budget. It's a simple fact of life that Canada is the wrong size class to match the US in military capabilities. You cretinous Americans who bleat on ad-nauseum about this fact are simply being pig-headed and willfuly thick.
But that is merely the surface of things. The US doesn't really want Canada to have a robust military, for example, the Arrow/Iroquois. That home-grown world-class project was killed by Diefenbaker at the behest of you Americans. From the Wikipedia article:
In a later interview in the 1990s, Pearkes discussed these problems and then revealed that he was advised by an American official, while en route to Colorado, that Canada did not need to build aircraft because the US had plenty and could make them available at any time.
So instead we were to deploy those idiotic Bomarc missiles that would use nuclear warheads over Canadian territory to shoot down Soviet bombers. American idea. Thanks much guys.
Moving along, lets talk about blood. In WWII, for example, at Normandy, the US (pop 130M): 2 beaches, the UK (pop 50M): 2 beaches, Canada (pop 12M): 1 beach. Now before anyone starts with their worn out what-have-you-done-for-me-lately awfulness, lets see how long Americans can shut the hell up about how they saved Europe from the Nazis. If you can wallow in WWII glory then and expect respect, then you better damn well give it where it's due.
I take no joy in what follows, but since I know this carries weight amongst certain brutal-minded types I might as well point out, Canadians are doing way more than their share of the dying in Kandahar right now at this very instant. I will not talk about comparative body counts because that is simply too disprespectful of the soldiers both yours and ours. You won't know about any of that because your news reports simply call us NATO soldiers but make no mistake, Canada is doing more than it's share there. So is the US and the UK.
Canadians don't pick up their guns often, thats a fact, but when we do it gets serious. Tweaking us with that we-could-invade-you-and-theres-nothing-you-can-do- about-it ignorance is so beside the point that knowing its the only thing can think of to say makes me want to just tie you up and flick your earlobe until you promsie to stop.
The favorite tactic of people like you is to toss out one-line lies that take pages and pages to explain properly. Its even worse when the audience (thats you) feels entitled to incuriosity because you have manged to convince yourself of your innate superiority. So not even do I have to explain what is ignorant about what you just said, I have to try to convince you to care. But I've already resigned myself to the fact that Amerians like you are ignorant and prefer it that way. So whats the point.
Montreal is overrun most holiday weekends with Boston college kids who can drink here before they can in your clenched-buttock country. From what I've seen, lotsa luck with your future. Each one wants to grow up to be just like your prez's: screwing the help and taking 8 months a year off.
What you know about Canada could be completely hidden within something as small as your brain.
I understand why you can't comfortably live with the fact that your closest neighbour and best friend, if nations can be said to have such things, thinks you are nuts. So you toss glib little epiphets that probably were programmed into you by a radio show and voila problem taken care of. But seriously, we have been watching your country go friggen kookier and kookier over the past many years and frankly it scares us.
It all started for me when your iconic president of the right said something to the effect that if only space aliens would invade earth, then mankind could unite. What a jerk. Then he signed into law a deregulation regime that transferred (via fraud) over 500 billion (probably close to a trillion in todays dollars) to his natural constituency (rich people) which ordinary taxpayers had to pay for. I don't know why you people put up with this but you do. It's pathetic. In many ways it's worse for Canadians because all we can do is watch and hope your country doesnt start leaking something radioactive.
When you become able to name the prime minister of my country during the Regan years, without looking it up, then we can have a conversation as knowledgable equals. Until then all you are doing is parroting meaningless old shallowisms to make yourself feel better.
P.S. Do you even know the order of magnitued of the Canadian death toll in Afghanistan?
P.P.S. While obviously pissed off, I'm not an American hater. The problem is that youre a big fat guy standing at the bar while we are sitting at a table right beside. Your ass is right in our face and you dont even know it. You should but you don't.
Every day I'm able (when I have the stomach for it) to watch America obsess inwardly about the minutae of it's own existence with rarely a mention of how the things they do impact upon the greater whole.
This is no accident. The reflexive American response to the subject of foreign events is dismissive and barely civil. As if every SINGLE other country is either backwards, lazy, unsophisticated, or a pathetic American wannabe. I deliberately cast this net wide, not every American says these things but it is their natural reflex: they are programmed that way in grade school by chanting chants, swearing oaths as children before they know what it means, and congratulating their adolescent selves with brave tales of the genocidic birth of their nation.
I'm a Canadian, I do a great deal of travel in the United States (or I did until who knows, my ranting gets me placed on some beaureaucratic American watch list or another designed to get some member of Congress re-elected) and I could not possible tell you (even under threat of water boarding) how many times the lets-take-over-Canada chestnut has so hilariously been tossed my way. I have had enough personal relationships to know that a joke told more than twice is not "just kidding" any more. Americans in their secret place really honest to God think that they need it, they want it, they can have it. And anyway, Canadians are smug socialistic freeloaders so who's going to stop us, Wayne Gretzky? Ha ha ha ha. Oh yeah, wimpy on terrorism too, the 9/11 hijakers came in through Canada everyone knows (Hillary Clinton, famously, publicly, and unretractedly), except they didn't although 80% of Americans continue to "know" they did, and your media doesn't budge an ever-so-cute hair on their pristine little CNN heads to correct that pathetic ignorance.
However, I digress. The matter at hand is why American intelligence fuck-ups are of any interest to non-Americans. I'll let my American friends in on a secret (which wouldn't be a secret if you got around more), nobody particulary thinks much of American intelligence or the American military in general. Mention the CIA to anyone besides an American and the first word out of that person's mouth is likely to be something like Pinochet, which if repeated to most Americans would garner the response, what is that, like, something new Taco Bell? Your military? Here's something apropos: lets say you are in your A-10 and about to blast the ever living shit out of something, don't you think you would go down and take a look at what ever it is you're about to shoot? American pilots apprently don't. They just follow the little numbers on their little displays in their little cockpits and push the little button on the stick when the light goes on, or whatever. Thats why they KEEP on blasting the crap out of their OWN British and Canadian allies. Any American apologist who tries to weasel-word his way out of the fact that this is obviously pathetic, I will personally come down there and puke on your mullet.
The few of you who actually retain enough common decency required to know what I'm talking about don't stand a chance of being able to do anything about it. And if you did, you would almost certainly be assasinated, just like the last three that tried.
So who cares if the CIA didn't get OBL. Or did. Or didn't try. Or did. Or was involved with him, or wasn't. If I thought for a picosecond the early interception of OBL would have caused the USA not to be a country of ignorant pricks any more, I would take an interest. But frankly, I'm sick of hearing American bullshit stink itself into my living room, so you can kiss my lily white Canaidan ass, you country of lowest common denominators.
Reminds me of an old joke. A meteor is about to collide with earth, killing everyone. The NYT headline reads:
Meteor to Annihilate Mankind Women and Minorities Worst Affected
Seriously though, all one needs to do is go to spring break at Daytona Beach to find out the American mainstream is completely uninterested in hearing moral admonishments from anyone. By and large the sky-magic crowd is content to tsk-tsk amongst themselves and talk loudly from time to time. But the States is far too modern to put up with anything seriously restrictive for long.
For example, lets say by some mir...er I mean unlikely occurrence, Roe v Wade gets overturned and things go back to the way they were in the '50s. That would just get young people (notorious non-voters) interested again and in a few years we would have another '60s. Frankly I'd be all for that.
All diesels have an unfortunate characteristic called the "smoke point." If the F/A mixture is richer than a certain threshold the burn doesn't have time to finish and intermediate combustion products are ejected out the exhaust. This threshold is lean of stoichiometric.
Despite the incomplete combustion, the power continues to increase which is why you sometimes see 18-wheelers spewing smoke. I don't think they are permitted to do this under most countries' emission laws but some truckers seem to have dialed in the extra power themselves.
The exact type of diesel fuel used will affect the smoke point. Generally speaking lower molecular weight hydrocarbons burn faster. I don't know what effect the sulfer content has on the smoke point (diesel is generally made from crappier crude than gasoline which means more sulfur), but reducing it has to be good because it's so malodorous.
There is a subtle issue with this paper which I notice the authors walked right around, whistling. That is, how do we know the majority of the mass of the clusters really *wasn't* in the gas clouds and condensed out during the collision?
As an example, this abstract talks about star formation initiated by ionization and shock fronts. The bullet part of the Bullet Cluster is a shock front thousands of parsecs long. As this shock travelled through the clouds, maybe the gas condensed into stars or proto-stars. These stars might not be completely formed yet nor strongly clustered and might be invisible to us. Maybe that matter remained with the clusters and didn't get swept along with the clouds.
The only thing the paper has to say about this is "...in the course of a cluster collision, galaxies
spatially decouple from the plasma." I expect this will have to be looked at further.
In other words, maybe the observed clusters aren't represenative of typical intergalactic space. The hubristic use of the word "PROOF" in the title and closing sentence is unfortunate.
A quick Google, oops I mean a quick search using the web site www.google.com, on the Vancouver Stock Exchange turned up this.
I still remember the time the prof in our numies class talked about rounding down if the trailing digit was 1-4, rounding up if it was 6-9, and randomly choosing up or down if it was 5. We were all thinking...Wha? None of the packages I have used since then (eg NASTRAN) employ such a strategy as far as I know, although it may be buried deep inside the guts somewhere.
But it's always been in the back of my mind, doesn't rounding up on 5 introduce a bias?
A previous moon-related story got me to do some calcs I have been thinking about for a while, to find how large the forward dragging (thrust) force on the moon would have to be to cause the orbit to increase by 3.8 cm a year.
I'm notoriously dicey with complicated algebra, but if I've done it right (assuming a circular orbit) the total (kinetic plus potential) energy of the moon is -.5*G*me*mm*delta(1/r); me, mm masses of earth & moon, r radius of the orbit. The delta can be approximated as -delta(r)/r^2, plugging in values gives a delta energy of 3.84e18 J
Distance travelled in a year is about 3.2e10m so the average thrust would be (force=work/distance) 3.84e18/3.2e10 = 1.2e8 N = 120,000 tonnes.
Another interesting thing is the ratio of this to the primary graviataional force. Fg = 1.9e20N so the ratio is about 5.8e-13. If we think about how far the force vector between the earth and moon is offset to give the calculated thrust, it is only about.22mm (thats 5.8e-13*r). That is, instead of the gravitational force vector passing directly through the center of the moon's orbit, it passes 0.22mm to the leading side due to tidal action. I find that surprisingly small, given that the center of mass of the earth is offset much further (1000's of kms) from the that point and the tidal bulging must be in the meters or 10's of meters.
Dilation & Evacuation becomes Partial Birth Abortion
Estate Tax becomes Death Tax
Anti Abortion becomes Pro Choice
Creationist becomes Intelligent Design
Able to Kill Anyone Instantaneously becomes Concealed Carry
Critical Thinking becomes Liberal Bias
Fox News: Liberal Bias: Yeah Right.
I became suspicious when I read the phrase "nano bits of silica". Nano technology my big toe: that's a marketing flourish.
The article mentions that this is a sheer thickening fluid, what they probably mean is shear thickening. That would be a fluid where the coefficient of viscosity increases with increasing strain rates, instead of remaining the classically Newtonian constant. In this case it's probably because the glycol tangles around the silica particles and can't untangle quickly.
While it's quite possible the material can become a semi-solid for the brief duration of a dynamic impact there is no reason to believe, and lots of reasons to not to believe, it becomes a particularly strong solid. In a particulate reinforced composite, which this is in its pseudo-solid state, the matrix (the ethylene glycol) is important to the strength and being a simple organic molecule it's strength must be on the same order of, say, polyethylene.
TFA itself infers this, noting the original idea of using the material itself (in peanut-butter mode) didn't work out. Instead it is employed as the matix in a conventional fiber composite using Kevar or Spectra or something like that as the workhorse.
As in all conventional fiber composites, the fiber bears the load, the matrix supports the fiber. In this case the support, I conjecture, amounts to preventing the fibers from displacing away from the impact point, probably allowing fewer layers of fiber to absorb a given impact energy.
Whle this is innovative and a good idea, it's hardly liquid armour. What I would hope for and maybe expect is better performance against pointy, hard, teflon-coated projectiles of the cop-killer variety which work by nosing the fibers out of the way.
Slashdot Mirror
The resistivity of graphite fibers varies quite a bit. For example the venerable Toray T300 fibers are listed around 2000 microohms-cm, while Union Carbide P100's are around 250. You have to be careful because bulk carbon is different. Aluminum is about 2.7 in those units. Graphite can be specially made to have lower resistivity but I'll use the 250 value for ROM calcs. Use a 16km cable length.
So if we assume a 1 in^2 cable section (6 cm^2) and they can manage to get 15kV, the current for 40MW is 2667A. The total resistance of a 16km cable would be 250e-6/6*16000*100=67 ohms. The power loss would be 2667^2*67 = 491MW. So this ROM calc shows it obviously wouldn't work because you would need a ridiculously fat cable.
The paper they wrote talks about an Vectran/aluminum conductor. Let's look at that quickly. To get 10% cable losses the cable resistance would have to be 4e6/2667^2 = .5 ohms. Using resistivity=2.7e-6 ohm-cm the cable section would have to be 2.7e-6*16000*100/.5=4.3 cm^2. The volume would be 16000*.00043=6.9m^3 and the mass 2700*6.9=18630kg (19 tonnes). So there you have 40 tonnes at least for the conductors, 60 if they use 3-phase transmission.
Vectran, Spectra, and Aramid fibers are all similar crystalline organic fibers. Ultimate tensile strength is usually around 3GPa, but you would probably use at most half that for a real world application. So to hold a 19000kb cable where F=19000*10=190000N, A=190000/1.5e9=1.27e-4m^2. Density is around 1500kg/m^3 so the Vectran mass/cable would be 1.27e-4*16000*1500=3048kg or 3 tonnes. So 6 or 9 tonnes total. Just to hold the cable weight.
The aerodynamic loads are hard to figure. Let's do something really rough. In their paper they quote energy density at altitude of 20kW/m^2. Air density is at 10km is .4kg/m^3. Wind velocity would be (20000/.4)^.5=223m/s. Assume they do really well and get 50% of the energy out, the rotor projected area has to be 40000000/10000=4000m^2 or a square 63m on a side. Energy density goes with the square of V, so the delta V would be 223*(1-.707) = 65m/s. Using the momentum equation, the force per m^2 is F=rho*V*delta V=.4*223*65=5798N. The total force would be 5798*4000=23,192,000N. Thats 5 million pounds.
This is the sort of time you wish you had someone to check your calcs, because that seems high. But if it is right, that would need a Vectran cable 1.27e-4*23000000/190000=.015m^2 area or about 7cm in diameter. Well, that looks maybe doable after all.
But the thing is a monster.
This is true, I did some calculations on the other thread that showed aluminum probably couldn't be made to work and graphite probably could. The property you need is a high tensile strength/density ratio. Kevlar and Specta also have very high ratios, so they could be used as the load carrying reinforcement.
The advantage of graphite is that it is conductive and could maybe be used as the conductor too so you wouldn't need the aluminum. That would add risk to the project because it may never have be done before.
A ROM calc showed that graphite conductive cables would weight about 40 tons. A reinforced aluminum cable might be double that. These are not small numbers, and the weight you add to the cables has to be held up by the platform, which takes away from the power generation.
None of that means it couldn't be feasible, practical, or economical, it just looks really hard to do.
I'd be happy to give you my work number offline so we can discuss what we respectively do and don't know. If your mom will let you use the phone.
I'm happen to be an expert in aircraft structures and based on what I said in the original thread, I really wonder if they know what they are talking about. The Economist article talks about aluminum tethers and from what I can tell such cables would be physically impossible. That is basic stuff to get wrong.
Secondly, a winged platform with horizontal-axis turbines would make more sense. Their helicopter-ish layout uses a lot of rotor structure to present a little area to the airflow. You cannot tilt the platform to present more rotor area to the airflow because the lift vector has to be parallel to the anchor cables where they attach to the vehicle. Those cables which will be nearly vertical, that is basic catenary physics and there is nothing you can do about it unless you use other lift vehicles to hold the tether up (the way high-altitude kites work.)
Thirdly, the jet stream meanders around. Are they thinking about moving the turbines to follow the jet stream? How would that work? Would they move their restricted airspace region to follow them? And what kind of ground station would be massive enough to bear the large forces this thing generates and be portable enough to drive on roads?
Fourthly, it will have either be certified by the FAA or will have to fly over uninhabited areas. Flying things crash, they always crash, and a 10 kilometer cable whipping down on you from the sky is a nasty thought. Certification has killed more than a few projects that otherwise seemed like good ideas.
I'm not saying it's all impossible. Just unlikely.
It just so happens I have a bit of experience designing aluminum and graphite aircraft parts, and my brother is an EE so by osmosis I know enough electrical stuff to fake some calculations.
Thing is, for a constant-diameter cable of a given density and a given strength, the length that can hang under it's own weight is an intrinsic property. For example, I would guess electrical grade (fairly pure) aluminum has a strength of at most 10,000 psi, and a density of .1 lb/in^3. The maximum hanging length would be 1.6 miles. If you taper it you might double that.
That doesn't even include the pulling loads from the monster at the top, which would be large. So aluminum is out.
Carbon nonotubes are hocus-pocus for real-world stuff right now, so forget about that.
However, graphite fibers conduct electricity not too bad, they might work, and they have fabulous strength in tension.
You could probably load a carbon fiber cable up to at least 100,000 psi, and it's density is .06 lb/in^3. That gives a hanging length of 26 miles. That looks better.
Let's fake an electrical calculation to see if it has a chance to work as a transmission cable.
If we use 10KV then for 10MW we have 1000A. The resistivity of graphite fibers is about 4 micro ohms-in. So lets say we make a 1 in^2 section cable, the resistance would be 4 micro-ohms/inch. A 10 mile length would have a resistance of 2.5 ohms and the power dissipation would be 2,500 watts. Surely we could dissipate that over about 10 miles without it overheating the cable.
The weight of the cable would be 1*10*5280*12*.06 = 38,016 lbs (19 tons). Since you need two of them, the total cable-weight load on the monster would be 38 tons.
Add to that the air loads of the horizontal windmill action (which is the whole point of the stupid thing) and what I'll call the catenary multiplier effect for lack of a better term, and the actual load on the cables will probably be something on the order of 100 tons. Since the cables were only stressed to about half their capabilities by the hanging load, it might work.
But you see why I call it a monster. The rotors have to genterate 100 tons of (inclined) lift.
(I used a 10 mile cable length throughout because while the altitude is about 6 miles, the monster is blown sideways and the cable hangs in a catenary shape.)
Toughness has both a qualitive and quantitive meaning. As someone mentioned before, it can be thought of as the amount of energy (the area under the stress-strain curve) required to fail the material. As a general rule, materials in the same class show an inverse relationship between strength and toughness.
It also has a quantitative definition that relates to crack sensitivity. Fracture toughness has a specific definition that relates to the strength of the stress singularity at a crack tip required to make the crack propogate unstably (i.e. break.)
The magnitude of the stress singularity is called the stress intensity K and its units are ksi*inches^.5 (MPa*m^.5). It varies with the applied stress and the geometry and size of the crack.
Stress intensity is the whole basis of fracture mechanics, which is a fairly new discipline only understood since about the 1950's. If you know the fracture toughness of a material you can calculate how big a crack any given thing made out of that material can withstand under a given load. Thats why planes are safe, they are designed to withstand cracks that can be easily found during inspection. Pressure vessels are designed to stand big enough cracks that they will start to leak before then burst so the problem becomes evident before they go boom. This kind of analysis is called damage tolerance.
It's also used to predict how fast cracks will grow under cyclic load. By testing you can develop the so called da/dN vs delta K curves that let u predict how long, for example, and airplane can fly before a crack that can't be found by inspection grows to a size that can be found. That tells you how often you should go look.
How come whenever someone in a faraway land eats something odd, we call it a delicacy. I bet the people in the next town over from Palomares say "Those guys from Palomeres, they dig up SNAILS and EAT THEM. Hillbillies."
This Spanish-fishing-village-nuclear-bomb thing reminds me of an old film called Day of the Fishes. I wonder if they are connected.
Most displacement-based structural finite element packages feature grid points that characterize motion with six parameters: X, Y, Z, RX, RY, RZ. This is because beam and plate elements are abstractions to reality that introduce the concept of "bending". Solid elements are "less" abstracted and often don't support the rotational degrees of freedom.
Just to say, using those six degrees of freedom at a point is a way to reproduce "reality" in a certain abstracted way.
I'm sorry, I know mullets and I know hockey hair, and that is no mullet.
Actually that was 54.40. "54 40 or Fight."
Well all right, I can see you will insist on hammering away at your sad little misconceptions until someone who actually knows sets you right, and even then I have little hope, but for what little its worth here's some truth.
Canada and the USA spend similarly on social programs, with the exception of health care. The US actually spends much more on health care (with similar overall outcomes) due to the fractured and inefficient nature of your system. But that doesn't get counted as social spending because it's not a government program.
As a percentage of GDP, US defence spending is about 4%, Canada is approaching 2% this year. Canada is on the high side of NATO defence/GDP spending now though in the last decade it was lower. Mostly due to scarey deficits and debts we had to fix. Personally I was never comfortable with those low spending levels, but that's an internal matter for us Canadians to sort out, isn't it?
The total Canadian Federal budget is about the same size as the American defence budget. It's a simple fact of life that Canada is the wrong size class to match the US in military capabilities. You cretinous Americans who bleat on ad-nauseum about this fact are simply being pig-headed and willfuly thick.
But that is merely the surface of things. The US doesn't really want Canada to have a robust military, for example, the Arrow/Iroquois. That home-grown world-class project was killed by Diefenbaker at the behest of you Americans. From the Wikipedia article:
So instead we were to deploy those idiotic Bomarc missiles that would use nuclear warheads over Canadian territory to shoot down Soviet bombers. American idea. Thanks much guys.
Moving along, lets talk about blood. In WWII, for example, at Normandy, the US (pop 130M): 2 beaches, the UK (pop 50M): 2 beaches, Canada (pop 12M): 1 beach. Now before anyone starts with their worn out what-have-you-done-for-me-lately awfulness, lets see how long Americans can shut the hell up about how they saved Europe from the Nazis. If you can wallow in WWII glory then and expect respect, then you better damn well give it where it's due.
I take no joy in what follows, but since I know this carries weight amongst certain brutal-minded types I might as well point out, Canadians are doing way more than their share of the dying in Kandahar right now at this very instant. I will not talk about comparative body counts because that is simply too disprespectful of the soldiers both yours and ours. You won't know about any of that because your news reports simply call us NATO soldiers but make no mistake, Canada is doing more than it's share there. So is the US and the UK.
Canadians don't pick up their guns often, thats a fact, but when we do it gets serious. Tweaking us with that we-could-invade-you-and-theres-nothing-you-can-do- about-it ignorance is so beside the point that knowing its the only thing can think of to say makes me want to just tie you up and flick your earlobe until you promsie to stop.
The favorite tactic of people like you is to toss out one-line lies that take pages and pages to explain properly. Its even worse when the audience (thats you) feels entitled to incuriosity because you have manged to convince yourself of your innate superiority. So not even do I have to explain what is ignorant about what you just said, I have to try to convince you to care. But I've already resigned myself to the fact that Amerians like you are ignorant and prefer it that way. So whats the point.
Montreal is overrun most holiday weekends with Boston college kids who can drink here before they can in your clenched-buttock country. From what I've seen, lotsa luck with your future. Each one wants to grow up to be just like your prez's: screwing the help and taking 8 months a year off.
What you know about Canada could be completely hidden within something as small as your brain.
I understand why you can't comfortably live with the fact that your closest neighbour and best friend, if nations can be said to have such things, thinks you are nuts. So you toss glib little epiphets that probably were programmed into you by a radio show and voila problem taken care of. But seriously, we have been watching your country go friggen kookier and kookier over the past many years and frankly it scares us.
It all started for me when your iconic president of the right said something to the effect that if only space aliens would invade earth, then mankind could unite. What a jerk. Then he signed into law a deregulation regime that transferred (via fraud) over 500 billion (probably close to a trillion in todays dollars) to his natural constituency (rich people) which ordinary taxpayers had to pay for. I don't know why you people put up with this but you do. It's pathetic. In many ways it's worse for Canadians because all we can do is watch and hope your country doesnt start leaking something radioactive.
When you become able to name the prime minister of my country during the Regan years, without looking it up, then we can have a conversation as knowledgable equals. Until then all you are doing is parroting meaningless old shallowisms to make yourself feel better.
P.S. Do you even know the order of magnitued of the Canadian death toll in Afghanistan?
P.P.S. While obviously pissed off, I'm not an American hater. The problem is that youre a big fat guy standing at the bar while we are sitting at a table right beside. Your ass is right in our face and you dont even know it. You should but you don't.
Rest of the Planet to Americans: Put down the nuclear weapons and step away from the maifest destiny.
You are no longer worthy.
Every day I'm able (when I have the stomach for it) to watch America obsess inwardly about the minutae of it's own existence with rarely a mention of how the things they do impact upon the greater whole.
This is no accident. The reflexive American response to the subject of foreign events is dismissive and barely civil. As if every SINGLE other country is either backwards, lazy, unsophisticated, or a pathetic American wannabe. I deliberately cast this net wide, not every American says these things but it is their natural reflex: they are programmed that way in grade school by chanting chants, swearing oaths as children before they know what it means, and congratulating their adolescent selves with brave tales of the genocidic birth of their nation.
I'm a Canadian, I do a great deal of travel in the United States (or I did until who knows, my ranting gets me placed on some beaureaucratic American watch list or another designed to get some member of Congress re-elected) and I could not possible tell you (even under threat of water boarding) how many times the lets-take-over-Canada chestnut has so hilariously been tossed my way. I have had enough personal relationships to know that a joke told more than twice is not "just kidding" any more. Americans in their secret place really honest to God think that they need it, they want it, they can have it. And anyway, Canadians are smug socialistic freeloaders so who's going to stop us, Wayne Gretzky? Ha ha ha ha. Oh yeah, wimpy on terrorism too, the 9/11 hijakers came in through Canada everyone knows (Hillary Clinton, famously, publicly, and unretractedly), except they didn't although 80% of Americans continue to "know" they did, and your media doesn't budge an ever-so-cute hair on their pristine little CNN heads to correct that pathetic ignorance.
However, I digress. The matter at hand is why American intelligence fuck-ups are of any interest to non-Americans. I'll let my American friends in on a secret (which wouldn't be a secret if you got around more), nobody particulary thinks much of American intelligence or the American military in general. Mention the CIA to anyone besides an American and the first word out of that person's mouth is likely to be something like Pinochet, which if repeated to most Americans would garner the response, what is that, like, something new Taco Bell? Your military? Here's something apropos: lets say you are in your A-10 and about to blast the ever living shit out of something, don't you think you would go down and take a look at what ever it is you're about to shoot? American pilots apprently don't. They just follow the little numbers on their little displays in their little cockpits and push the little button on the stick when the light goes on, or whatever. Thats why they KEEP on blasting the crap out of their OWN British and Canadian allies. Any American apologist who tries to weasel-word his way out of the fact that this is obviously pathetic, I will personally come down there and puke on your mullet.
The few of you who actually retain enough common decency required to know what I'm talking about don't stand a chance of being able to do anything about it. And if you did, you would almost certainly be assasinated, just like the last three that tried.
So who cares if the CIA didn't get OBL. Or did. Or didn't try. Or did. Or was involved with him, or wasn't. If I thought for a picosecond the early interception of OBL would have caused the USA not to be a country of ignorant pricks any more, I would take an interest. But frankly, I'm sick of hearing American bullshit stink itself into my living room, so you can kiss my lily white Canaidan ass, you country of lowest common denominators.
Reminds me of an old joke. A meteor is about to collide with earth, killing everyone. The NYT headline reads:
Meteor to Annihilate Mankind
Women and Minorities Worst Affected
Seriously though, all one needs to do is go to spring break at Daytona Beach to find out the American mainstream is completely uninterested in hearing moral admonishments from anyone. By and large the sky-magic crowd is content to tsk-tsk amongst themselves and talk loudly from time to time. But the States is far too modern to put up with anything seriously restrictive for long.
For example, lets say by some mir...er I mean unlikely occurrence, Roe v Wade gets overturned and things go back to the way they were in the '50s. That would just get young people (notorious non-voters) interested again and in a few years we would have another '60s. Frankly I'd be all for that.
All diesels have an unfortunate characteristic called the "smoke point." If the F/A mixture is richer than a certain threshold the burn doesn't have time to finish and intermediate combustion products are ejected out the exhaust. This threshold is lean of stoichiometric.
Despite the incomplete combustion, the power continues to increase which is why you sometimes see 18-wheelers spewing smoke. I don't think they are permitted to do this under most countries' emission laws but some truckers seem to have dialed in the extra power themselves.
The exact type of diesel fuel used will affect the smoke point. Generally speaking lower molecular weight hydrocarbons burn faster. I don't know what effect the sulfer content has on the smoke point (diesel is generally made from crappier crude than gasoline which means more sulfur), but reducing it has to be good because it's so malodorous.
There is a subtle issue with this paper which I notice the authors walked right around, whistling. That is, how do we know the majority of the mass of the clusters really *wasn't* in the gas clouds and condensed out during the collision?
As an example, this abstract talks about star formation initiated by ionization and shock fronts. The bullet part of the Bullet Cluster is a shock front thousands of parsecs long. As this shock travelled through the clouds, maybe the gas condensed into stars or proto-stars. These stars might not be completely formed yet nor strongly clustered and might be invisible to us. Maybe that matter remained with the clusters and didn't get swept along with the clouds.
The only thing the paper has to say about this is "...in the course of a cluster collision, galaxies spatially decouple from the plasma." I expect this will have to be looked at further.
In other words, maybe the observed clusters aren't represenative of typical intergalactic space. The hubristic use of the word "PROOF" in the title and closing sentence is unfortunate.
A quick Google, oops I mean a quick search using the web site www.google.com, on the Vancouver Stock Exchange turned up this.
I still remember the time the prof in our numies class talked about rounding down if the trailing digit was 1-4, rounding up if it was 6-9, and randomly choosing up or down if it was 5. We were all thinking...Wha? None of the packages I have used since then (eg NASTRAN) employ such a strategy as far as I know, although it may be buried deep inside the guts somewhere.
But it's always been in the back of my mind, doesn't rounding up on 5 introduce a bias?
A previous moon-related story got me to do some calcs I have been thinking about for a while, to find how large the forward dragging (thrust) force on the moon would have to be to cause the orbit to increase by 3.8 cm a year.
I'm notoriously dicey with complicated algebra, but if I've done it right (assuming a circular orbit) the total (kinetic plus potential) energy of the moon is -.5*G*me*mm*delta(1/r); me, mm masses of earth & moon, r radius of the orbit. The delta can be approximated as -delta(r)/r^2, plugging in values gives a delta energy of 3.84e18 J
Distance travelled in a year is about 3.2e10m so the average thrust would be (force=work/distance) 3.84e18/3.2e10 = 1.2e8 N = 120,000 tonnes.
Another interesting thing is the ratio of this to the primary graviataional force. Fg = 1.9e20N so the ratio is about 5.8e-13. If we think about how far the force vector between the earth and moon is offset to give the calculated thrust, it is only about .22mm (thats 5.8e-13*r). That is, instead of the gravitational force vector passing directly through the center of the moon's orbit, it passes 0.22mm to the leading side due to tidal action. I find that surprisingly small, given that the center of mass of the earth is offset much further (1000's of kms) from the that point and the tidal bulging must be in the meters or 10's of meters.
Good luck with your war, it's going real well I hear.
Pot: "kettle: black."
Dilation & Evacuation becomes Partial Birth AbortionEstate Tax becomes Death Tax
Anti Abortion becomes Pro Choice
Creationist becomes Intelligent Design
Able to Kill Anyone Instantaneously becomes Concealed Carry
Critical Thinking becomes Liberal Bias
Fox News: Liberal Bias: Yeah Right.
I became suspicious when I read the phrase "nano bits of silica". Nano technology my big toe: that's a marketing flourish.
The article mentions that this is a sheer thickening fluid, what they probably mean is shear thickening. That would be a fluid where the coefficient of viscosity increases with increasing strain rates, instead of remaining the classically Newtonian constant. In this case it's probably because the glycol tangles around the silica particles and can't untangle quickly.
While it's quite possible the material can become a semi-solid for the brief duration of a dynamic impact there is no reason to believe, and lots of reasons to not to believe, it becomes a particularly strong solid. In a particulate reinforced composite, which this is in its pseudo-solid state, the matrix (the ethylene glycol) is important to the strength and being a simple organic molecule it's strength must be on the same order of, say, polyethylene.
TFA itself infers this, noting the original idea of using the material itself (in peanut-butter mode) didn't work out. Instead it is employed as the matix in a conventional fiber composite using Kevar or Spectra or something like that as the workhorse.
As in all conventional fiber composites, the fiber bears the load, the matrix supports the fiber. In this case the support, I conjecture, amounts to preventing the fibers from displacing away from the impact point, probably allowing fewer layers of fiber to absorb a given impact energy.
Whle this is innovative and a good idea, it's hardly liquid armour. What I would hope for and maybe expect is better performance against pointy, hard, teflon-coated projectiles of the cop-killer variety which work by nosing the fibers out of the way.