The numbers don't look very promising for this kind of device.
Let's assume you have a 12-meter by 5-meter "kite" and it's moving out with the tide.
And let's assume the tide is a huge one, like 10 meters.
Also let's be generous and assume the kite can sequester an average of one meter of depth of water.
That's 60 cubic meters of water, falling 10 meters, twice a day.
Jut for fun, switching back to English units, about 60 tons falling 63 feet per day.
or 120,000 pounds falling 63 feet per day. That's about 87 ft-lbs/sec, or about 110 watts. Wholesale electricity is going for about 3 cents a kilowatt-hour, so this kite is at best making.33 cents an hour.
I don't think you can build deploy, and operate, and pay for a kite that size on that kind of income. Just the interest lone has to be more than that.
>et's do it over and over again until we actually get there, then.
You just don't get it. There are basic thermodynamic limits. They've been pushing these limits hard at a cost of billions a year, and not making any progress for the last 40 years.
>There are many examples of affordable microturbines already.
Links needed. I haven't seen any for under $30,000 or under $900 / HP and none with the efficiencies you claim. A lot of the efficiency numbers quoted assume you're using the waste heat to heat hot water, like in a hot-tub showroom, and very much unlike in a vehicle.
Nobody is able to afford a car engine that costs $900 per horsepower wholesale and has efficiency in the mid 20's.
> Microturbines have the potential to easily be twice as efficient as ICEs.
Citation needed, and I don't mean the Chevy model.
Gas turbines have been under development now for 120 years. Efficiency flat-lined about 40 years ago, as the basic Carnot temperature and heat-exchange limits were hit. The only way to bump up efficiency would be to up the hot-section temperatures, and they're already running those within 25 degrees of the melting point of the very best alloys.
The efficiencies you allude to are the pi-in-the-sky, in the laboratory, cost and maintenance are no object, open-loop, fixed-speed, optimum temp conditions. In the real world, turbines have less than optimal clearances, less than perfect balancing, temperature restrictions, temperature versus life restrictions, have to operate in closed-loop cycles, with variable and unpredictable power demands, and over bumpy roads and subject to dust, dirt, crosswinds across the intake, and abrupt accelerations, not to mention cost restrictions. Your basic high-tech turbine has a cost in the high tens of thousands-- never practical in a vehicle that has to leave the factory costing less than $10,000 and able to go 100,000 miles.
> Depending on the process used electrolysis can have an efficiency rating of 30%-60%.
Citations needed. One has to differentiate among the THEORETICAL electron-volt efficiencies, and actual efficiencies. The numbers you gave are the theoretical ones.
>Nuclear reactors are much better than 20% efficient.
A ground-based nuke plant with unlimited weight and space and maintenance and unlimited heat-sinks to a cold river, yes those, when running, and watched over by hundreds of humans, yes, they can hit 30%. I was thinking more like a nuke that could be lifted by a Saturn V, dialled down in temperature and flux for safety, longer life without any maintenance, and to work with a heat-sink loftable by another few Saturn V's. You'd be lucky to get 20% from that. I'll even give you a break and assume no need for another 50 Saturns V's to lift the minimal shielding needed to keep humans within a few hundred miles of the place. I'll even spot you any maintenance requirements.
>As the asteroids are heated, different materials will "cook off".
Sorry, I added to the confusion. I was alluding to the improbability of making a solar disassociator-- the thingy that splits the water. It has to run white-hot to split water.
You're talking about a solar cooker, in order to heat the asteroid and drive off the water. Totally different thingie, and I wonder how you'd ever collect the water? Hmmm....
>You are completely and totally wrong. Internal combustion engines used in automobiles top out around 25% efficiency. Electric motors used in cars top out around 95% efficient, and they're even over 90% efficient when acting as a generator (during regenerative braking.)
Uh, you forgot about the other parts of the electricy-delivery cycle:: Power plants: 35%. Distribution system: 90%. Rectifiers/chargers: 90%. Battery charging: 80%. By the time you multiply those out, you're down to about 18% efficiency, not all that different than a IC engine.
>Correct me if I am wrong, but cooling systems should be far superior in space, too, or not?
Not.
There is nothing there to conduct or convect the heat away, such as the running water that we use to cool power plants down here.
All you're left with is the option to radiate it away, for which you require huge amounts of surface area of highly heat-conductive material. The deployment of several square miles of unobtanium is left as an exercise for the reader.
Hows about the issues involved in building a a target that can stand the white-hot temperatures needed to dissassociate water, and keep it from melting down and reacting with the oxygen, sulphates, borates, and other contaminants. White hot steel does not last long in the presence of pure oxygen and sulfates.
>..solar radiation, which costs you nothing, and the interesting parts of which can be gathered with a large mylar-bag mirror.
Yep, in superficial theory at least. The tricky bits involve shaping the mirror to the required accuracy, aiming it, and building a a target that can stand the white-hot temperatures needed to dissassociate water, and keep it from melting down and reacting with the oxygen, sulphates, borates, and other contaminants. White hot steel does not last long in the presence of pure oxygen and sulfates.
Your basic laws of physics limit this to a mostly laughable concept.
You can't make "fuel" out of water, not without the addition of about 9 times the energy you'd get by just using the original energy.
For example, to break up water into Hydrogen and Oxygen, you can use electrolysis, which is only about 11% efficient, so you need 10 units of electricity to make one unit of H and O. On an asteroid, you're gonna have to get the electricity from a nuclear reactor/turbine system, which itself is only going to be about 20% efficient (and you're going to need a few acres of heat-sink to condense the working fluid). So we're up to throwing away 49 units of energy to make one unit of H and O rocket fuel. Or you're going to need a very large and complex solar collector with super-complex metallurgy to generate a high enough heat to disassociate the water. And then there's the extra energy needed to compress and liquefy the fuels. Plus there's the not so small problem of anode poisoning and mineral clogging. The water up there is probably going to be heavily contaminated with typical asteroid junk like sulphates and phosphates. Those will poison the electrolysis anodes and clog up the solar disassociator toote-suite.
The whole idea is really, really, far out, with a negligible efficiency at best and dismal chance of success.
Any chance you could take a stab at reading what you've written and see if it makes a lick of sense?
Perhaps in some corner of Lesser Crapville the slang "rolled over" and the other random combination of letters have some discernible meaning, but how about writing for the rest of humankind?
BEfore we wet our pants in excitement, let's remember:
* The Hubble passed a slew of design reviews too. * Even so, it went up with many, many flaws, including: * Electronics not shielded well enough to handle the South Atlantic Anomaly. * Gyroscopes not qualified for the temperature cycles and SAA. * Solar panels that oilcan buckle when going from sunlight to shade. * Solar panel mount that does not go through the center of mass of the scope, so oilcan buckling causes the whole thing to oscillate. * Unbalanced and uncushioned light cap that likewise shakes the whole thing when it's operated.
Although the new scope will have been checked against that list of problems, without major overhaul of the management structure, it's likely the same thing will happen this time.
That should be "its" competitors. And it's unlikely they'd flex their muscles much in the direction of stifling the companies that use the ARM design. More likely: Apple wants to extend ARM in directions that the current ARM management is balking at.
There are bazillions of combinatorial tests that your average stresser program does not do, and cannot foresee that it needs doing.
There's a whole lot more than the basic instruction set that needs to be tested for.
For instance all the superscalar stuff -- pipeline loading, serializing, register interlocks, register renaming, stack register lookahead, jump prediction, cache prediction, cache-snooping, cross-core interlocks-- all things that require a certain complex SET of carefully primed and timed instructions to test.
Not to mention the extra MMX, SSE, SSE2, SSE3, and later instructions.
Your basic CPU heater program is not going to test for these, at least not intentionally, and not often.
>Saying the plane is a "disaster waiting to happen" is wrong, stupid, and yes, an insult to the designers for implying they'd make something that some random/.er can see in two seconds is going to be brought out of the air by rain.
I'm sure the designers did not intentionally make something so un-airworthy-- they're just constrained by the very low power available. You can't change the basic amount of power available, so you have to compromise on everything else. The wing is going to have to be long and huge, both for solar collection area and to get a low wing-loading, good glide ratio and low stall speed. It's going to have to be built as lightly as possible, which means it can't stand much stress. Planes that are certified have to be capable of +3 and -1G stress, but one suspects this plane has much narrower margins. That makes the plane much more susceptible to damage from turbulence and limits its maneuverability.
With a low landing speed and long wings, it's going to be in deep doo-doo when landing in a cross-wind. Your really maneuverable planes are limited to crosswinds on the order of 25% of landing speed. This plane is NOT very maneuverable, and cannot be banked very much on approach due to its long wings. That probably limits it to a cross-wind component of maybe 10%. With its low landing speed, that means anything over 4MPH is going to be a HUGE problem.
I'm sure the designers did the best they could within the power and weight limits. But still the best you're gonna get is not going to ever be certifiable as an airplane.
>15hp continuous is not 15hp peak. It has batteries.
Yep, and it's going to need them for situations like takeoff, climb, rain, downdrafts, clouds, night, or icing.
But that means the rest of the time it has *less* than 15hp to work with if it's going to use some of its sun power to recharge the batteries. No free lunch.
I don't see any reason for the vituperation. I did not attack the designers, I just mentioned some obvious facts to compensate for people's superficial understanding of flying objects. Slashdot tends to be a bit too gee-whizzy in its enthusiasms. I think there's room and need for a little factual balance.
Wonderful, as a concept. But horrible as a vehicle.
Do the math. 60 meter wingspan times maybe 4 meter wing width gives you 240 square meters of solar cell area. You get about 150 watts per square meter with the sun at right angles and no clouds. That's about 48 horsepower at best. Now integrate that for a whole day and night and you have about 15 horsepower continuous.
A 15 horsepower plane is a really, really unsafe and miserable vehicle. It's just an underpowered and fragile disaster waiting to happen. Even a light rain is going to bring it down.
I wish he pilot well and hope their parachute works.
The article suggests the battery can put out 4 megawatts for 8 hours. So that's 32,000 kilowatt-hours. My electricity here costs about 7 cents a kWh, so that BOB can hold almost $225 worth of electricity. At a cost of many millions, that does not sound like very economical power per kWh!
For example, your basic Honda generator can run for two thousand hours, putting out 1,500 watts, before the little putt-putt engine needs an overhaul. So that's about 3,000 kilowatt-hours for $400. Let's assume the power fails ten times a year, so you'd wear out 10 Honda generators per failure (avg), at a cost of $4000 per, or $40,000 per year. By comparison BOB's cost of financing in itself is going to be at least $3 million a year, not to mention maintenance.
So these poor sods are paying about 75 times as much as they should.
( Not to mention that generators are much more economical in larger sizes )
Slashdot Mirror
The numbers don't look very promising for this kind of device.
Let's assume you have a 12-meter by 5-meter "kite" and it's moving out with the tide.
And let's assume the tide is a huge one, like 10 meters.
Also let's be generous and assume the kite can sequester an average of one meter of depth of water.
That's 60 cubic meters of water, falling 10 meters, twice a day.
Jut for fun, switching back to English units, about 60 tons falling 63 feet per day.
or 120,000 pounds falling 63 feet per day. That's about 87 ft-lbs/sec, or about 110 watts. .33 cents an hour.
Wholesale electricity is going for about 3 cents a kilowatt-hour, so this kite is at best making
I don't think you can build deploy, and operate, and pay for a kite that size on that kind of income.
Just the interest lone has to be more than that.
>et's do it over and over again until we actually get there, then.
You just don't get it. There are basic thermodynamic limits. They've been pushing these limits hard at a cost of billions a year, and not making any progress for the last 40 years.
>There are many examples of affordable microturbines already.
Links needed. I haven't seen any for under $30,000 or under $900 / HP and none with the efficiencies you claim. A lot of the efficiency numbers quoted assume you're using the waste heat to heat hot water, like in a hot-tub showroom, and very much unlike in a vehicle.
Nobody is able to afford a car engine that costs $900 per horsepower wholesale and has efficiency in the mid 20's.
> Microturbines have the potential to easily be twice as efficient as ICEs.
Citation needed, and I don't mean the Chevy model.
Gas turbines have been under development now for 120 years. Efficiency flat-lined about 40 years ago, as the basic Carnot temperature and heat-exchange limits were hit. The only way to bump up efficiency would be to up the hot-section temperatures, and they're already running those within 25 degrees of the melting point of the very best alloys.
The efficiencies you allude to are the pi-in-the-sky, in the laboratory, cost and maintenance are no object, open-loop, fixed-speed, optimum temp conditions. In the real world, turbines have less than optimal clearances, less than perfect balancing, temperature restrictions, temperature versus life restrictions, have to operate in closed-loop cycles, with variable and unpredictable power demands, and over bumpy roads and subject to dust, dirt, crosswinds across the intake, and abrupt accelerations, not to mention cost restrictions. Your basic high-tech turbine has a cost in the high tens of thousands-- never practical in a vehicle that has to leave the factory costing less than $10,000 and able to go 100,000 miles.
> Depending on the process used electrolysis can have an efficiency rating of 30%-60%.
Citations needed. One has to differentiate among the THEORETICAL electron-volt efficiencies, and actual efficiencies. The numbers you gave are the theoretical ones.
>Nuclear reactors are much better than 20% efficient.
A ground-based nuke plant with unlimited weight and space and maintenance and unlimited heat-sinks to a cold river, yes those, when running, and watched over by hundreds of humans, yes, they can hit 30%. I was thinking more like a nuke that could be lifted by a Saturn V, dialled down in temperature and flux for safety, longer life without any maintenance, and to work with a heat-sink loftable by another few Saturn V's. You'd be lucky to get 20% from that. I'll even give you a break and assume no need for another 50 Saturns V's to lift the minimal shielding needed to keep humans within a few hundred miles of the place. I'll even spot you any maintenance requirements.
>As the asteroids are heated, different materials will "cook off".
Sorry, I added to the confusion. I was alluding to the improbability of making a solar disassociator-- the thingy that splits the water. It has to run white-hot to split water.
You're talking about a solar cooker, in order to heat the asteroid and drive off the water. Totally different thingie, and I wonder how you'd ever collect the water? Hmmm....
>You are completely and totally wrong. Internal combustion engines used in automobiles top out around 25% efficiency. Electric motors used in cars top out around 95% efficient, and they're even over 90% efficient when acting as a generator (during regenerative braking.)
Uh, you forgot about the other parts of the electricy-delivery cycle:: Power plants: 35%. Distribution system: 90%. Rectifiers/chargers: 90%. Battery charging: 80%. By the time you multiply those out, you're down to about 18% efficiency, not all that different than a IC engine.
>Correct me if I am wrong, but cooling systems should be far superior in space, too, or not?
Not.
There is nothing there to conduct or convect the heat away, such as the running water that we use to cool power plants down here.
All you're left with is the option to radiate it away, for which you require huge amounts of surface area of highly heat-conductive material. The deployment of several square miles of unobtanium is left as an exercise for the reader.
>No complex metallurgy is required.
Hows about the issues involved in building a a target that can stand the white-hot temperatures needed to dissassociate water, and keep it from melting down and reacting with the oxygen, sulphates, borates, and other contaminants. White hot steel does not last long in the presence of pure oxygen and sulfates.
>..solar radiation, which costs you nothing, and the interesting parts of which can be gathered with a large mylar-bag mirror.
Yep, in superficial theory at least. The tricky bits involve shaping the mirror to the required accuracy, aiming it, and building a a target that can stand the white-hot temperatures needed to dissassociate water, and keep it from melting down and reacting with the oxygen, sulphates, borates, and other contaminants. White hot steel does not last long in the presence of pure oxygen and sulfates.
Your basic laws of physics limit this to a mostly laughable concept.
You can't make "fuel" out of water, not without the addition of about 9 times the energy you'd get by just using the original energy.
For example, to break up water into Hydrogen and Oxygen, you can use electrolysis, which is only about 11% efficient, so you need 10 units of electricity to make one unit of H and O. On an asteroid, you're gonna have to get the electricity from a nuclear reactor/turbine system, which itself is only going to be about 20% efficient (and you're going to need a few acres of heat-sink to condense the working fluid). So we're up to throwing away 49 units of energy to make one unit of H and O rocket fuel. Or you're going to need a very large and complex solar collector with super-complex metallurgy to generate a high enough heat to disassociate the water. And then there's the extra energy needed to compress and liquefy the fuels. Plus there's the not so small problem of anode poisoning and mineral clogging. The water up there is probably going to be heavily contaminated with typical asteroid junk like sulphates and phosphates. Those will poison the electrolysis anodes and clog up the solar disassociator toote-suite.
The whole idea is really, really, far out, with a negligible efficiency at best and dismal chance of success.
Why, at that rate, they'll be able to simultaneously recharge 0.06% of the electric cars in the country!
And with the usual 30 milliamp analog phone line current, it will only take about a dozen years to recharge each car.
When you have a minute, go to YouTube and bring up an old Star Trek episode (not the CBS ones with very loud commercials).
Then turn on Google captions. More fun than a barrel of Rigelian monkeys!
About every third sentence gets a close or exact rendering, but oh, the other two! I should sue them for laugh-muscle strains.
Any chance you could take a stab at reading what you've written and see if it makes a lick of sense?
Perhaps in some corner of Lesser Crapville the slang "rolled over" and the other random combination of letters have some discernible meaning, but how about writing for the rest of humankind?
BEfore we wet our pants in excitement, let's remember:
* The Hubble passed a slew of design reviews too.
* Even so, it went up with many, many flaws, including:
* Electronics not shielded well enough to handle the South Atlantic Anomaly.
* Gyroscopes not qualified for the temperature cycles and SAA.
* Solar panels that oilcan buckle when going from sunlight to shade.
* Solar panel mount that does not go through the center of mass of the scope, so oilcan buckling causes the whole thing to oscillate.
* Unbalanced and uncushioned light cap that likewise shakes the whole thing when it's operated.
Although the new scope will have been checked against that list of problems, without major overhaul of the management structure, it's likely the same thing will happen this time.
That should be "its" competitors. And it's unlikely they'd flex their muscles much in the direction of stifling the companies that use the ARM design.
More likely: Apple wants to extend ARM in directions that the current ARM management is balking at.
There are bazillions of combinatorial tests that your average stresser program does not do, and cannot foresee that it needs doing.
There's a whole lot more than the basic instruction set that needs to be tested for.
For instance all the superscalar stuff -- pipeline loading, serializing, register interlocks, register renaming, stack register lookahead, jump prediction, cache prediction, cache-snooping, cross-core interlocks-- all things that require a certain complex SET of carefully primed and timed instructions to test.
Not to mention the extra MMX, SSE, SSE2, SSE3, and later instructions.
Your basic CPU heater program is not going to test for these, at least not intentionally, and not often.
Ridiculous.
The quantum-cryptography part is almost indubidably used for the preliminary exchange of keys.
The actual data is then sent by normal, non-quantum channels.
Paying $4000 for a thousand gigabytes is not so bad. Some of us have worked on:
DEC DF-32: 32K 12-bit words for around $5000 (1971)
DEC RKO5- 2.5 megabytes for $10,000 ( 1973 )
Mac HD-20: 20 megabytes for $1000 ( 1985 )
All those were like, 1000x or more per byte. AND WE WERE PERFECTLY HAPPY. (Well, a little cramped on the DF32)
>Saying the plane is a "disaster waiting to happen" is wrong, stupid, and yes, an insult to the designers for implying they'd make something that some random /.er can see in two seconds is going to be brought out of the air by rain.
I'm sure the designers did not intentionally make something so un-airworthy-- they're just constrained by the very low power available. You can't change the basic amount of power available, so you have to compromise on everything else. The wing is going to have to be long and huge, both for solar collection area and to get a low wing-loading, good glide ratio and low stall speed. It's going to have to be built as lightly as possible, which means it can't stand much stress. Planes that are certified have to be capable of +3 and -1G stress, but one suspects this plane has much narrower margins. That makes the plane much more susceptible to damage from turbulence and limits its maneuverability.
With a low landing speed and long wings, it's going to be in deep doo-doo when landing in a cross-wind. Your really maneuverable planes are limited to crosswinds on the order of 25% of landing speed. This plane is NOT very maneuverable, and cannot be banked very much on approach due to its long wings. That probably limits it to a cross-wind component of maybe 10%. With its low landing speed, that means anything over 4MPH is going to be a HUGE problem.
I'm sure the designers did the best they could within the power and weight limits. But still the best you're gonna get is not going to ever be certifiable as an airplane.
>15hp continuous is not 15hp peak. It has batteries.
Yep, and it's going to need them for situations like takeoff, climb, rain, downdrafts, clouds, night, or icing.
But that means the rest of the time it has *less* than 15hp to work with if it's going to use some of its sun power to recharge the batteries. No free lunch.
I don't see any reason for the vituperation. I did not attack the designers, I just mentioned some obvious facts to compensate for people's superficial understanding of flying objects. Slashdot tends to be a bit too gee-whizzy in its enthusiasms. I think there's room and need for a little factual balance.
Wonderful, as a concept. But horrible as a vehicle.
Do the math. 60 meter wingspan times maybe 4 meter wing width gives you 240 square meters of solar cell area.
You get about 150 watts per square meter with the sun at right angles and no clouds. That's about 48 horsepower at best.
Now integrate that for a whole day and night and you have about 15 horsepower continuous.
A 15 horsepower plane is a really, really unsafe and miserable vehicle. It's just an underpowered and fragile disaster waiting to happen.
Even a light rain is going to bring it down.
I wish he pilot well and hope their parachute works.
Let's do the math here.
The article suggests the battery can put out 4 megawatts for 8 hours. So that's 32,000 kilowatt-hours. My electricity here costs about 7 cents a kWh, so that BOB can hold almost $225 worth of electricity. At a cost of many millions, that does not sound like very economical power per kWh!
For example, your basic Honda generator can run for two thousand hours, putting out 1,500 watts, before the little putt-putt engine needs an overhaul. So that's about 3,000 kilowatt-hours for $400. Let's assume the power fails ten times a year, so you'd wear out 10 Honda generators per failure (avg), at a cost of $4000 per, or $40,000 per year. By comparison BOB's cost of financing in itself is going to be at least $3 million a year, not to mention maintenance.
So these poor sods are paying about 75 times as much as they should.
( Not to mention that generators are much more economical in larger sizes )
Nothing to see here...
Moving malloc() to a separate thread does not do a thing for the putative word processor.
They might get some speedup if they take a lousy old malloc() and have one thread hold onto the locks.
But of course the *right* way would be to write a new malloc() that can from the get-go run re-entrantly and not require a bevy of slow locks.
A light in the sky is not going to do any good when people are asleep.
A light in the sky is not going to attract any attention during the day unless it's a goodly fraction of the sun's brightness.