Superior is a big lake, but I doubt that it is either big or deep enough to exhibit the kind of wave phenomena these researchers are investigating. Smaller waves piling up when they hit shallower water or coming from different directions (created by converging winds) would be sufficient to explain the sinking.
FWIW I was travelling recently and saw some posters which appeared to be made from underwater photos of the resting place of the Fitz. Sobering.
To be blunt, what you think is immaterial unless you are able to finance the construction of a skyhook.
I'll stipulate to that.
What you think about reusable private spacecraft flying 3 people to 100 km and back is also immaterial unless you are able to finance their construction, too. You may note that it looks to be accomplished by not one but at least two ventures this year.
You have no idea how much mass would be needed to construct your 55 ton skyhook, no idea what structure the skyhook itself should take, no idea how spectra behaves in the presence of monatomic oxygen, no idea how vunerable it is to micrometeorite impact, no idea how much mass needs to be added to make it conduct electricity (so that you can boost it as you proposed eatlier)...
55 tons is the total mass, skyhook, counterweight, everything. The spent upper stage of the rocket used to loft it could be part of the 55 tons. Ditto payload shrouds if not jettisoned. If you were willing to have the skyhook be double-ended you could shrink the total to about 37 tons (note that I took the maximum cross section area, multiplied by the density and total length and tripled it; the most you would actually require is double, but I wanted to leave a fudge factor).
Others have already researched this.
Probably not well. It will likely need a protective coating and have to be replaced on a schedule. If you can loft material sufficient to make a new one on a regular basis this should not be a problem.
Others have addressed the micrometeoroid issue. There are open braided designs which allow redundancy in the load paths so that a severed fiber does not affect the overall integrity.
Aluminum and gold coatings appear to be good for conductivity, and they also appear to do an excellent job of protecting Kapton films against monatomic oxygen.
Of course, you could always fly a sub-scale test mission to see how the stuff works. OSC is still selling Pegasus launches for a few million bucks, isn't it?
And now to finance your private enterprise access to space you propose bringing in the russians.
The Russians don't have any money, they have rockets and launch services for sale. They have even been selling tourist trips to the ISS, or haven't you noticed? I'm sure that you could get them to put 55 tons into orbit if you had money, and this hotelier's fortune appears more than sufficient.
TSS's failure showed that there is a world of difference between what is theoretically possible & what is practical. To go from one to the other takes time & money.
Did anything I said say otherwise? And did you notice that there is one very interested party who has the time and money? I don't see how you could miss it, he was the subject of TFA.
I asked you: "Do you honestly think that we will have a functional skyhook before private access to orbital space becomes reality?"
We already have private access to space, purchasable from the Russians and perhaps the Chinese. What we can do is to use this to bootstrap another technology that has the potential to cut the cost of access to something that a hotelier could accept as a cost of doing business.
Misgivings about your/. login name aside....
My login name is word-play on the title of a song. By the time I made this account, all the good ones were taken.
... I don't think that you're a troll, just muuuch too optimistic on what ressources are needed for a working skyhook. There is just too much to do, to[sic] many unknowns.
And I think you're much too pessimistic (and sloppy with your grammar). Any such project is going to
Until a functional skyhook is built, 100KM gives no more access to orbital space than does living on a mountain.
It looks to me like you could put up a functional skyhook with one launch of a heavy-lift rocket; you might need as little as 55 tons to get started.
I suppose you think that Dupont is able to deliver wherever you specify?
Anywhere on earth, yes. I figure that I could manage the fabrication and transport from there, and someone like the Russians could loft it.
Tethers _May_ be able to reboost using electricity.
The TSS failed because of an arc between the imperfectly-insulated wire in the tether and the metal framework of the reel system. This would not be an issue with a skyhook operating in free space, and the physics go back to Maxwell's equations. Do you have any solid objections or are you saying that the inevitability of engineering glitches makes the idea impossible?
I had a chance to do some calculus yesterday, and got some useful answers.
Ignoring tidal forces (which will be much smaller than centripetal accelerations and can thus be disregarded for a quickie analysis), the acceleration at any point on a rotating skyhook is equal to ^2r. Each unit of mass of the skyhook increases the weight pulling against the center by an amount proportional to the acceleration, so I got this equation (where T is tension, A is the cross-sectional area, a is acceleration, S is working strength, omega is angular velocity, rho is density and r is radius):
dT = rho Aa dr<p> = rho (T/S) omega^2r dr (1)<p> dT/T = (rho omega^2/S)r dr (2)<p> ln T = (rho omega^2/2S) r^2 + C (3)
This yields the tension ratio (and thus the area ratio) between any two radii. Note that the log of the tension ratio is proportional to omega^2r^2, meaning it is proportional to the tip speed squared. It is also inversely proportional to the working strength of the skyhook's material.
Spectra(tm) fiber is already up to an ultimate tensile strength of 3.5 GPa at a density of 0.97 (970 kg/m^3). Assuming that tomorrow's nanotube-reinforced Spectra will permit a fiber at this same strength/density ratio for its working strength and fudging the density to 1.0, I get the following for the taper ratio:
ln( A/A0 ) = (4.281e-3)^2*1000*1.55e6^2/7e9 = 6.290, or A/A0 = 540. If the cross-section required to support 5 tons of spacecraft at 3 G acceleration at the outer tip is (150 kN / 7 Gpa) = 0.0000214 m^2 = 21.4 mm^2, the cross-section at the center would be 116 cm^2. This is a square less than 11 cm across.
Mass of the total skyhook depends on the distance to the counterweight, but I'll just guesstimate it as 3 times the mass of the center cross-section extended all the way to the tip. This amounts to 3 *.0116 m^2 * 1.55e6 m * 1 ton/m^3 = 53940 tons. That's one hell of a long way from gigatons.
It's also a lot of mass to put up with rockets. However, nothing says you have to start so big. Mass of the skyhook is proportional to its weight capacity and in roughly inverse proportion to its tip acceleration (which determines the length). If you put up a bootstrap skyhook capable of handling 50 kg payloads and with a tip acceleration of 15 G, it would need a mass of roughly 275 tons; for 20 kg payloads and 30 G, 55 tons. Lofting payloads to such a skyhook would be amazingly cheap; you wouldn't need aircraft, you could use guns. Once you were in a position to send payloads to the skyhook you could send up spools of fiber to make it thicker and expand its carrying capacity.
Last is the issue of reboost. Putting 20 kg of mass into orbit at ~7500 m/sec and raising it by 155 km against 1 G takes 562.5+30.4=592.9 MJ or 164.7 KWH. If you have 5 solar arrays a la Deep Space One which put out 2 KW apiece, you'd need about 16 hours of sunlight to reboost after each payload (ignoring losses). More power capacity means a greater payload rate. If you can keep adding solar cells, you can increase the lift rate proportional to your power. If you can get to 6 payloads/day you'd be lifting 120 kg/day or enough to build another skyhook in less than 1.5 years. From there, the increase is exponential.
The information I have comes mostly from several books I read, mostly from the anti-nuclear power side, I admit. But I think that, with the amount of money going on in the nuclear energy business, A LOT of information is kept hidden by the (nuclear) powers-that-be (pun intended). So, if even half of everything I have read would be true, I still would not go for nuclear.
In what little research I've done on the claims of anti-nuclear activists, I have found that most of them are full of blatant falsehoods; their reasoning from the truths that they use is often fallacious. The amount of money in the nuclear business isn't what it's cracked up to be, either. Most of the information you need to evaluate the truth of the various claims is found in nuclear physics references (CRC Handbook of Chemistry and Physics is where I get most of mine). How do you hide a fact of physics? More to the point, if you censored the data used for teaching the nuclear scientists and engineers who produce the hardware, how could you hide the conspiracy?
I'd agree with you that half would be a pretty hard case to beat, but in my estimation the truth value is more like 2%, and another 5% which happens to be based on fact but applies to 1940's-era weapons production and has nothing at all to do with commercial nuclear electric power. The rest is made up.
Remember, you have to take into account the WHOLE process, from ore-in-the-ground to thousands of years lifethreatening waste. The useful phase where energy is generated is practically zero in that perspective.
Nuclear is the alternative to coal. How long does a bit of coal take to burn compared to how long it laid in the ground? How long will the CO2 be in the atmosphere? (I've heard figured up to 200 years, which is about six half-lives of the longest-lived of the really nasty isotopes in fission products. It would not be at all difficult to ensure foolproof isolation of all fission products for longer than the age of the pyramids in Egypt. In that time any danger from strontium-90 or cesium-137 would be gone, and all you would have remaining is the long-lived isotopes which last so long because they are only weakly radioactive.)
Remember, you have to take into account the WHOLE process, from ore-in-the-ground to thousands of years lifethreatening waste.
All you have to look at on the input end is the cost of yellowcake. That price incorporates all the energy inputs and everything else, and it looks like it is downright cheap.
On the subject of "life threatening waste", have you looked at the criteria that the government is using to determine if a disposal site is good enough or not? Over hundreds of thousands of years some of these isotopes might migrate a few miles, and if someone drinks the groundwater from that area they might have their risk of cancer go up a few percent. People who drink water from outside that area would never be affected. (The only reason people would be drinking water there is if civilization collapses and people forget how to make radiation detectors; the carrying capacity of Nevada desert in the absence of modern infrastructure such as aqueducts isn't all that high.) This is supposed to rule out the use of a technology that keeps all of the carcinogenic arsenic from coal out of the air, not to mention the mercury emissions. On the balance, I do not think that the anti-nukes are interested in public health.
Everything you've just claimed is either flat-out wrong or highly debatable.
BTW, the amount of energy used to produce uranium fuel takes about 90% of a reactor's lifetime to win back...
It takes perhaps 120,000 SWU(Separation Work Units) to produce one fuel-load for a typical 1000 MWe LWR. Gaseous diffusion requires roughly 2.5 MWH (2500 KWH) to produce one SWU, so the total fuel load would require approximately 300 GWH of electricity to separate it. That amounts to about 12.5 days of reactor output, for a load of fuel which will last roughly 2 years.
Gas centrifuges require about 50 KWh per SWU, giving an electric consumption of about 6 GWH per fuel load. That's 4 load's worth of fuel for a day's reactor output; put another way, one reactor working 300 days per year could produce fuel for 2400 reactors.
And CO2? Same story: in the pre-energy-generating phase is at least as much CO2 released as a coal plant would have for the same amount of energy.
Assuming 24 million BTU/ton of coal and 10,200 BTU/KWH heat rate, a 1 GW coal plant would have to burn 425 tons/hour of coal to get the required 1.02e10 BTU/hour of heat. That's 10,200 tons of coal per day, or over 3.6 million tons of coal per year. A pile of coal that big would completely cover a 1 GW nuclear plant; there is no way that construction of the plant would require more energy or release more CO2 than is in so much coal.
You're either a knowing participant or a willing dupe in a disinformation campaign. If the latter, reconsider your information sources; if the former, please jump off the nearest object more than 20 meters tall (the world doesn't need any more liars).
... until a rotating skyhook is built, SS1's ability to theoretically connect to it is just an irrelevant factoid, right?
Nope. At the point that it repeatably flies to 100-110 km, it is a proven technology and thus a potential off-the-shelf building block.
Do you honestly think that we will have a functional skyhook before private access to orbital space becomes reality?
You've got it backwards. We'll need access to space to put the skyhook into orbit. What it will do is drastically lower the cost of bulk access and allow round trips to be much cheaper than current technology (and even future rocket technology) would ever allow.
Where do you propose that the materials for the skyhook come from?
E.I. DuPont? Honeywell International? That page on Spectra claims tensile strengths upwards of 3 GPa and density less than 1, which ought to let me calculate a taper ratio and mass when I get a chance to sit down and do a little calculus. Watch for another reply.
A perennial problem for rotating skyhooks is that the up/down traffic neeeds to be balanced.
Not strictly; you have to reboost to replace lost energy and angular momentum. One advantage of using a skyhook for this is that you can run an electric current through it and push against Earth's magnetic field; by unbalancing the current in different parts of the skyhook you can also control the spin and trade rotational energy for center-of-mass orbital velocity.
If all you are trying to do is reclaim the energy and angular momentum, it doesn't matter if the product comes down inside the delivery craft or not. You could probably drop a load of aerogel from 100 km without any heat shielding at all and it should be just fine, though I would want to wrap it in plastic to keep dirt off it.
Space Ship One has sufficient speed and altitude capability to connect to a rotating skyhook. A rotating skyhook with some extra capabilities (like being able to climb from the end down toward the center) would create a way to go from the cycloid motion of the skyhook's end to a transfer orbit for the space station (or you attach the space station to the skyhook, at the cost of interrupting your zero-G when the CG shifts due to loading and unloading cargo craft). To go back down to earth, you just reverse the process.
A skyhook with a center-of-mass eastward orbital speed of 16,000 MPH picking up a craft at a eastward speed of 900 MPH and accelerating the end at 3 G would have to extend (r = v^2/a -> r = (15100*.44704)^2/29.4 = 1550 km = 963 miles from the CG. This is a big task, but hardly impossible. I wish I had time to work the required taper and mass but I've got real work to do today.:(
There are some things you just can't do on Earth, such as the production of transparent aerogels without the blue tint. Then there are things that you don't want to do on Earth, such as research on extremely dangerous organisms.
I look at Space Ship One as a sufficient advance for certain kinds of space manufacturing; in a cargo configuration it could launch to the top of its arc and meet with the end of a rotating skyhook (the materials science will make rotating skyhooks feasible much sooner than synchronous skyhooks). The skyhook carries it around and into orbit, where cargo is exchanged for product. On the next trip around the spaceplane is dropped at ~65 miles up and finally completes the other half of its trajectory, while the skyhook reclaims the energy and angular momentum that it loaned to the cargo craft.
I have not had a chance to calculate the profit potential of a kilogram of aerogel, but if a Rutan-style spaceplane can carry sub-orbital cargo for $50/kg and a skyhook-supported factory can process it for less than 10 times that, it looks to me like the material for a super-insulating window would be a rather small part of the overall cost. You would not have to worry about transporting fuel because your skyhook is only loaning energy and momentum, and you can use electrodynamic systems to push yourself against Earth's magnetic field without any need for reaction mass (you may need some gas to run plasma contactors but that is minimal).
Re:Loss of expertise is only one element
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I would say that the potental ASW threat is real. Can you think of a better way to put a commando team "state terrorists" ashore than a sub. Look at North Korea. How about putting ashore bio or chemical agents?
Could I do this with a WWII-style diesel/electric sub? Probably. Could I do this with a modern version thereof, powered by off-the-shelf fuel cells burning fuel with liquid oxygen and able to stay underwater for a week? Almost certainly. Do I need a modern nuclear hunter-killer sub or SLBM sub for this? No, they are too big for the job.
I don't see any need for submarines except to help contain the imperialist ambitions of China, and we already have enough for that.
After WWI people thought that subs where useless. The same thing happened right after WWII. The first post war sub was not built until 1949.
(You mean "were" [rhymes with "sure"], not "where" [rhymes with "air"].)
Hostilities began on the Korean peninsula in 1950. It was the Cold War, and communist imperialists were at work throughout Asia. Our enemies now are very different, and the same weapons cannot be used to fight them. Of what use is a submarine against a terrorist hiding in Kuala Lumpur or the Phillipines?
Also as long as we depend on SLBMs we will want to have SSNs to protect them and to train our ASW crews.
SLBMs are only of use against nations. How many SLBM carriers do we need to protect against the national threats of today? Seems to me that one would suffice to protect against both China and N. Korea. That would argue for keeping three active.
Not to mention there value as Sigint platforms, special OPs, and Cruise missle platforms.
(You mean "their" value.) Submarines aren't useful for SIGINT unless they are surfaced (unless you mean tapping undersea cables, which requires a specialized boat) and they would appear to be much more expensive per cruise-missile launch than a surface vessel. The kind of threats we've been dealing with of late have been terrorists, who have little capability of tracking ships at sea let alone threatening them; the hiding capacity of the SLCM carrier appears to be wasted in today's environment.
Plus do not forget that India is trying to build an SSN as is Brazil.
Since when were those nations hostile to us? (India is trying to counterbalance China, which helps us.) Is there any prospect of either of them becoming remotely equal to the USN in submarine capability, even if we reduce our activity to maintenance level? Seems to me that neither one of them has the money or technology, even if they had the will. The money we're spending on replacement of perfectly good submarines just to keep the production lines going would appear to be better spent on ways to identify and deport Islamic fanatics, and on energy initiatives to reduce the need for oil and help de-fund the Saudi prosyletization of Wahhabism.
With that kind of storage and power capabilities, the car could be very useful as a self-portable, silent and pollution-free power supply. It wouldn't be able to move itself very far, but even a mile is plenty for many important applications.
Terrorism exist because of anger, distrust, and a sense of hopelessness and/or exploitation.
Oh, bull. The West Bank and Gaza were enjoying a rapidly rising standard of living and unprecedented freedoms under Israeli rule. (Yes, more freedoms than under Egyptian and Jordanian rule.) Then the PA "leadership" was installed, and things went to hell.
The pilots (brains) of the 9/11 hijackers were all upper-class people. They were neither hopeless nor exploited, and they took advantage of a country that did NOT distrust them... to attempt to murder more than ten thousand of its citizens and decapitate its government. (That last was attempted by similarly-motivated terrorists in India with some measure of success.)
The perpetrators are rarely any of the things you claim. What they are is fanatic, tutored in hate in madrassas and by "educational" television which extols murder and "martyrdom" as virtues.
But its neither easy or convenient to think like this - in a capitalist society, some would even consider it heresy. It's time consuming - don't think that declaring a Palestinian state would make Osama retire tomorrow. It demands a greater understanding of foreign culture, idealogy, and history...
Ooh, irony. The first part of understanding the purveyors of terror is to take them at their own word about their beliefs, because belief is what drives them. The first part of the fight in the information war on terror is to learn what people believe and keep the fanatics the hell away from civilization, because civilized societies simply cannot be protected well enough from enemies within.
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The problem goes deeper than what you describe. There is more than enough money in NASA's budget to recreate the Saturn V, but the budget priorities as set by Congress and the institutional culture are so different from what existed during Apollo that the goal is beyond reach despite being easier to do the second time.
NASA has spent tens of billions on a series of programs to develop Shuttle replacements, and all of them have been total fiascoes. This is what appears likely to happen to a super-cool submarine development program; the political priorities will be to feed the best campaign contributors rather than the best technology, and the production of experimental boats will become an end in itself. That's the nature of Leviathan.
Turn the question around. The USA is the preeminent military power on the planet, and there is no hostile force that can deliver more than pinpricks (the bombing of the USS Cole was a tragedy, but to the fighting force of the USN it was negligible). Are submarines of any use to fight our current or foreseeable enemies? If not, it makes sense to let them go the way of the battleship.
For overhaul, you could melt a thermoplastic glue or just cut through a plasma-welded hull. To close up afterwards you'd just reverse the process. I expect that a plasma-welding process would be quite a bit slower than conventional welding and would therefore be more expensive.
The Navy is having a hard time getting any new subs much less one with a new tech hull. Since the fall of the USSR subs have a low priority.
Indeed. Without an enemy armed with ICBMs, SLBMs or a serious navy, submarines don't have many jobs left. A sensible nation would direct resources where they can do more good, and that's what appears to have been done.
You would still have to weld the stuff. It would next to impossible to cast a hull for a sub.
Grind, plasma-cut or EDM-machine notches in the edges for finger joints and glue them together (brazing will work just as well if you won't get crystallization). Another method would be to plasma-spray more of the same alloy into the cold joint and roll smooth between applications; this way the joint would be composed of the same glass as the bulk plate.
If the bulk material has low shatter resistance it might not be a good choice for hulls required to resist impacts, depth charges and other insults.
You could use it the same way we use glass
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To avoid the shattering problem, you could use lots of metal fibers in a matrix of something else (say, resin). This would give you the possibility of an injection-molded steel-fiber composite bicycle frame. (Why you'd use steel instead of glass or carbon, I don't know - but it would be possible.)
I can see the glass issue as a problem for some of the proposed uses, though. To retain its strength it would have to avoid crystallizing; if you used it for beams in a building, you would have to guarantee that a fire could not raise the temperature high enough long enough for the material to begin crystallizing. Once that happens, all your wonderful high-strength properties are ruined and you have to replace all that steel (assuming the building survives).
The old seat designs are nowhere near as good as they ought to be, and retrofitting ought to be mandatory in any event. No one airline would gain a competitive advantage if all of them had to upgrade, and the cost of wiring improvements in the seats themselves would be lost in the noise.
There's a good business in refitting aircraft of all types, from airliners all the way down to single-engine piston planes. There is already wiring to all seats in modern airliners for the sound system; there appears to be no reason that seats with alternative wiring (power instead of audio, and feed audio over lighter cabling using SPDIF or the like) could not be STC'ed[1] and the old wiring channels re-used for power. Replacing the seats would also let the airliners do something about the low crashworthiness of the older styles (they pull loose in impacts which would otherwise be survivable).
[1] Supplemental Type Certification, which is an addendum to the aircraft's original FAA Type Certification. I'm sure that someone installs something requiring an STC into an aircraft in the US several times a day.
The solution for laptops on aircraft is so simple, nobody seems to be smart enough to urge its adoption: Put "power points" (lighter jacks) at all the seats. If you've got 13.8 VDC (with appropriate current limitations) you don't need a fuel cell; you don't even need a battery (though it's a good idea).
Given the huge amount of power it takes just to stay in the air, I can't see a commercial airliner not being able to spare 30 watts per seat for hardware. The weight of wiring might be an issue, but if you run 110 VAC 400 Hz 3 phase down the aircraft and use switching converters at each row of seats that'll be minimal.
... I don't understand why the team doesn't direct effort towards 'enterprise features' rather than Chatzilla.
The developers probably use chat features far more intensively than a calendar. When your charter is "scratch what itches", what's going to get the lion's share of the work?
If enterprise customers want top-flight calendar handling in Mozilla, all they'd have to do is assign some people to work on it or contribute some money to a group doing the job. The calendar might be the last thing keeping them hooked to Microsoft. When you consider what it could save them in Windows licences alone, failing to look there is close to breach of fiduciary duty.
That would be easier to take seriously if there were an existing synthetic pathway which could use such energy, but I believe that the radiation-resistant bugs like Dienococcus Radiourans are not even photosynthetic. The amount of energy recoverable from the radiation is small compared to the chemical energy of the organic solvents, so any bug trying to "eat" the radiation would be seriously out-competed by the bugs chewing on the chemicals.
the high levels of radioactivity might contribute to the formation of some unusual high-energy organics, of which the bacteria could then make use.
Which would be silly for an organism to depend on, because the fraction of the potential food which is converted to these unusual compounds is such a small part of the total. D. Radiourans was discovered happily chewing on irradiated food in sealed packages (which was completely edible to humans before the bacteria got to it), and it would be more successful eating the run-of-the-mill organic molecules and ignoring the exotic stuff than the reverse. Guess which option would be favored by selection and population dynamics?
Which is not to say that some bug might not eat both, but it's a no-brainer to see what it would start with.
Slashdot Mirror
Chance sightings and measurements of these brief phenomena are one thing, a global census-by-sampling is quite another.
FWIW I was travelling recently and saw some posters which appeared to be made from underwater photos of the resting place of the Fitz. Sobering.
I'll stipulate to that.
What you think about reusable private spacecraft flying 3 people to 100 km and back is also immaterial unless you are able to finance their construction, too. You may note that it looks to be accomplished by not one but at least two ventures this year.
Of course, you could always fly a sub-scale test mission to see how the stuff works. OSC is still selling Pegasus launches for a few million bucks, isn't it?
The Russians don't have any money, they have rockets and launch services for sale. They have even been selling tourist trips to the ISS, or haven't you noticed? I'm sure that you could get them to put 55 tons into orbit if you had money, and this hotelier's fortune appears more than sufficient.
Did anything I said say otherwise? And did you notice that there is one very interested party who has the time and money? I don't see how you could miss it, he was the subject of TFA.
We already have private access to space, purchasable from the Russians and perhaps the Chinese. What we can do is to use this to bootstrap another technology that has the potential to cut the cost of access to something that a hotelier could accept as a cost of doing business.
My login name is word-play on the title of a song. By the time I made this account, all the good ones were taken.
And I think you're much too pessimistic (and sloppy with your grammar). Any such project is going to
Ignoring tidal forces (which will be much smaller than centripetal accelerations and can thus be disregarded for a quickie analysis), the acceleration at any point on a rotating skyhook is equal to ^2r. Each unit of mass of the skyhook increases the weight pulling against the center by an amount proportional to the acceleration, so I got this equation (where T is tension, A is the cross-sectional area, a is acceleration, S is working strength, omega is angular velocity, rho is density and r is radius):
This yields the tension ratio (and thus the area ratio) between any two radii. Note that the log of the tension ratio is proportional to omega^2r^2, meaning it is proportional to the tip speed squared. It is also inversely proportional to the working strength of the skyhook's material.
Spectra(tm) fiber is already up to an ultimate tensile strength of 3.5 GPa at a density of 0.97 (970 kg/m^3). Assuming that tomorrow's nanotube-reinforced Spectra will permit a fiber at this same strength/density ratio for its working strength and fudging the density to 1.0, I get the following for the taper ratio:
ln( A/A0 ) = (4.281e-3)^2*1000*1.55e6^2/7e9 = 6.290, or A/A0 = 540. If the cross-section required to support 5 tons of spacecraft at 3 G acceleration at the outer tip is (150 kN / 7 Gpa) = 0.0000214 m^2 = 21.4 mm^2, the cross-section at the center would be 116 cm^2. This is a square less than 11 cm across.
Mass of the total skyhook depends on the distance to the counterweight, but I'll just guesstimate it as 3 times the mass of the center cross-section extended all the way to the tip. This amounts to 3 * .0116 m^2 * 1.55e6 m * 1 ton/m^3 = 53940 tons. That's one hell of a long way from gigatons.
It's also a lot of mass to put up with rockets. However, nothing says you have to start so big. Mass of the skyhook is proportional to its weight capacity and in roughly inverse proportion to its tip acceleration (which determines the length). If you put up a bootstrap skyhook capable of handling 50 kg payloads and with a tip acceleration of 15 G, it would need a mass of roughly 275 tons; for 20 kg payloads and 30 G, 55 tons. Lofting payloads to such a skyhook would be amazingly cheap; you wouldn't need aircraft, you could use guns. Once you were in a position to send payloads to the skyhook you could send up spools of fiber to make it thicker and expand its carrying capacity.
Last is the issue of reboost. Putting 20 kg of mass into orbit at ~7500 m/sec and raising it by 155 km against 1 G takes 562.5+30.4=592.9 MJ or 164.7 KWH. If you have 5 solar arrays a la Deep Space One which put out 2 KW apiece, you'd need about 16 hours of sunlight to reboost after each payload (ignoring losses). More power capacity means a greater payload rate. If you can keep adding solar cells, you can increase the lift rate proportional to your power. If you can get to 6 payloads/day you'd be lifting 120 kg/day or enough to build another skyhook in less than 1.5 years. From there, the increase is exponential.
I'd agree with you that half would be a pretty hard case to beat, but in my estimation the truth value is more like 2%, and another 5% which happens to be based on fact but applies to 1940's-era weapons production and has nothing at all to do with commercial nuclear electric power. The rest is made up.
Nuclear is the alternative to coal. How long does a bit of coal take to burn compared to how long it laid in the ground? How long will the CO2 be in the atmosphere? (I've heard figured up to 200 years, which is about six half-lives of the longest-lived of the really nasty isotopes in fission products. It would not be at all difficult to ensure foolproof isolation of all fission products for longer than the age of the pyramids in Egypt. In that time any danger from strontium-90 or cesium-137 would be gone, and all you would have remaining is the long-lived isotopes which last so long because they are only weakly radioactive.) All you have to look at on the input end is the cost of yellowcake. That price incorporates all the energy inputs and everything else, and it looks like it is downright cheap.On the subject of "life threatening waste", have you looked at the criteria that the government is using to determine if a disposal site is good enough or not? Over hundreds of thousands of years some of these isotopes might migrate a few miles, and if someone drinks the groundwater from that area they might have their risk of cancer go up a few percent. People who drink water from outside that area would never be affected. (The only reason people would be drinking water there is if civilization collapses and people forget how to make radiation detectors; the carrying capacity of Nevada desert in the absence of modern infrastructure such as aqueducts isn't all that high.) This is supposed to rule out the use of a technology that keeps all of the carcinogenic arsenic from coal out of the air, not to mention the mercury emissions. On the balance, I do not think that the anti-nukes are interested in public health.
Gas centrifuges require about 50 KWh per SWU, giving an electric consumption of about 6 GWH per fuel load. That's 4 load's worth of fuel for a day's reactor output; put another way, one reactor working 300 days per year could produce fuel for 2400 reactors.
Assuming 24 million BTU/ton of coal and 10,200 BTU/KWH heat rate, a 1 GW coal plant would have to burn 425 tons/hour of coal to get the required 1.02e10 BTU/hour of heat. That's 10,200 tons of coal per day, or over 3.6 million tons of coal per year. A pile of coal that big would completely cover a 1 GW nuclear plant; there is no way that construction of the plant would require more energy or release more CO2 than is in so much coal.You're either a knowing participant or a willing dupe in a disinformation campaign. If the latter, reconsider your information sources; if the former, please jump off the nearest object more than 20 meters tall (the world doesn't need any more liars).
If all you are trying to do is reclaim the energy and angular momentum, it doesn't matter if the product comes down inside the delivery craft or not. You could probably drop a load of aerogel from 100 km without any heat shielding at all and it should be just fine, though I would want to wrap it in plastic to keep dirt off it.
A skyhook with a center-of-mass eastward orbital speed of 16,000 MPH picking up a craft at a eastward speed of 900 MPH and accelerating the end at 3 G would have to extend (r = v^2/a -> r = (15100*.44704)^2/29.4 = 1550 km = 963 miles from the CG. This is a big task, but hardly impossible. I wish I had time to work the required taper and mass but I've got real work to do today. :(
I look at Space Ship One as a sufficient advance for certain kinds of space manufacturing; in a cargo configuration it could launch to the top of its arc and meet with the end of a rotating skyhook (the materials science will make rotating skyhooks feasible much sooner than synchronous skyhooks). The skyhook carries it around and into orbit, where cargo is exchanged for product. On the next trip around the spaceplane is dropped at ~65 miles up and finally completes the other half of its trajectory, while the skyhook reclaims the energy and angular momentum that it loaned to the cargo craft.
I have not had a chance to calculate the profit potential of a kilogram of aerogel, but if a Rutan-style spaceplane can carry sub-orbital cargo for $50/kg and a skyhook-supported factory can process it for less than 10 times that, it looks to me like the material for a super-insulating window would be a rather small part of the overall cost. You would not have to worry about transporting fuel because your skyhook is only loaning energy and momentum, and you can use electrodynamic systems to push yourself against Earth's magnetic field without any need for reaction mass (you may need some gas to run plasma contactors but that is minimal).
I don't see any need for submarines except to help contain the imperialist ambitions of China, and we already have enough for that.
(You mean "were" [rhymes with "sure"], not "where" [rhymes with "air"].)Hostilities began on the Korean peninsula in 1950. It was the Cold War, and communist imperialists were at work throughout Asia. Our enemies now are very different, and the same weapons cannot be used to fight them. Of what use is a submarine against a terrorist hiding in Kuala Lumpur or the Phillipines?
SLBMs are only of use against nations. How many SLBM carriers do we need to protect against the national threats of today? Seems to me that one would suffice to protect against both China and N. Korea. That would argue for keeping three active. (You mean "their" value.) Submarines aren't useful for SIGINT unless they are surfaced (unless you mean tapping undersea cables, which requires a specialized boat) and they would appear to be much more expensive per cruise-missile launch than a surface vessel. The kind of threats we've been dealing with of late have been terrorists, who have little capability of tracking ships at sea let alone threatening them; the hiding capacity of the SLCM carrier appears to be wasted in today's environment. Since when were those nations hostile to us? (India is trying to counterbalance China, which helps us.) Is there any prospect of either of them becoming remotely equal to the USN in submarine capability, even if we reduce our activity to maintenance level? Seems to me that neither one of them has the money or technology, even if they had the will. The money we're spending on replacement of perfectly good submarines just to keep the production lines going would appear to be better spent on ways to identify and deport Islamic fanatics, and on energy initiatives to reduce the need for oil and help de-fund the Saudi prosyletization of Wahhabism.With that kind of storage and power capabilities, the car could be very useful as a self-portable, silent and pollution-free power supply. It wouldn't be able to move itself very far, but even a mile is plenty for many important applications.
The pilots (brains) of the 9/11 hijackers were all upper-class people. They were neither hopeless nor exploited, and they took advantage of a country that did NOT distrust them... to attempt to murder more than ten thousand of its citizens and decapitate its government. (That last was attempted by similarly-motivated terrorists in India with some measure of success.)
The perpetrators are rarely any of the things you claim. What they are is fanatic, tutored in hate in madrassas and by "educational" television which extols murder and "martyrdom" as virtues.
Ooh, irony. The first part of understanding the purveyors of terror is to take them at their own word about their beliefs, because belief is what drives them. The first part of the fight in the information war on terror is to learn what people believe and keep the fanatics the hell away from civilization, because civilized societies simply cannot be protected well enough from enemies within.NASA has spent tens of billions on a series of programs to develop Shuttle replacements, and all of them have been total fiascoes. This is what appears likely to happen to a super-cool submarine development program; the political priorities will be to feed the best campaign contributors rather than the best technology, and the production of experimental boats will become an end in itself. That's the nature of Leviathan.
Turn the question around. The USA is the preeminent military power on the planet, and there is no hostile force that can deliver more than pinpricks (the bombing of the USS Cole was a tragedy, but to the fighting force of the USN it was negligible). Are submarines of any use to fight our current or foreseeable enemies? If not, it makes sense to let them go the way of the battleship.
If the bulk material has low shatter resistance it might not be a good choice for hulls required to resist impacts, depth charges and other insults.
I can see the glass issue as a problem for some of the proposed uses, though. To retain its strength it would have to avoid crystallizing; if you used it for beams in a building, you would have to guarantee that a fire could not raise the temperature high enough long enough for the material to begin crystallizing. Once that happens, all your wonderful high-strength properties are ruined and you have to replace all that steel (assuming the building survives).
The old seat designs are nowhere near as good as they ought to be, and retrofitting ought to be mandatory in any event. No one airline would gain a competitive advantage if all of them had to upgrade, and the cost of wiring improvements in the seats themselves would be lost in the noise.
[1] Supplemental Type Certification, which is an addendum to the aircraft's original FAA Type Certification. I'm sure that someone installs something requiring an STC into an aircraft in the US several times a day.
Given the huge amount of power it takes just to stay in the air, I can't see a commercial airliner not being able to spare 30 watts per seat for hardware. The weight of wiring might be an issue, but if you run 110 VAC 400 Hz 3 phase down the aircraft and use switching converters at each row of seats that'll be minimal.
If enterprise customers want top-flight calendar handling in Mozilla, all they'd have to do is assign some people to work on it or contribute some money to a group doing the job. The calendar might be the last thing keeping them hooked to Microsoft. When you consider what it could save them in Windows licences alone, failing to look there is close to breach of fiduciary duty.
Alternately: What does your name smell like?
That would be easier to take seriously if there were an existing synthetic pathway which could use such energy, but I believe that the radiation-resistant bugs like Dienococcus Radiourans are not even photosynthetic. The amount of energy recoverable from the radiation is small compared to the chemical energy of the organic solvents, so any bug trying to "eat" the radiation would be seriously out-competed by the bugs chewing on the chemicals.
Which is not to say that some bug might not eat both, but it's a no-brainer to see what it would start with.