A less sinister and conspiratorial reason might simply be that, now that the launch complex isn't seeing a shuttle launch every couple of months, there's a good bit of downtime to do the cleanup without interfering with launch operations.
Unfortunately, the speed with which it gets there is only a small amount of the total energy you need to expend to get something from the Earth to the Moon. The Apollo craft (Command/Service Module + Lunar Excursion Module) together weighed about 45,000 kilos, and it took a Saturn V to get it there. The first two stages of the Saturn V could get about 100,000 kg to LEO. About half of that was the Apollo craft, and the other half was the third stage that boosted Apollo from LEO into a lunar transfer.
The ISS is over 400,000 kilos, about 9 times as massive as Apollo. So (ballparking here) you'd need the equivalent of 4-5 Saturn V, or a few dozen Delta-IV / Ariane-5, rockets to get enough propellant to LEO to subsequently boost the station to the moon. Maybe we'll have more options as we near 2020 (e.g., Falcon Heavy), but that is only to get the fuel up to the station. Once you get the propellant up there, you'd need to have mechanisms for attaching the rocket(s) to the station, ganging the fuel tanks together, balancing the mass amongst them, etc.
And once you got it kicked off to the Moon, what would you do with it? The ISS isn't really designed to operate outside of LEO. Radiation will be a problem for both the station and its occupants.
Isn't a social network non-private by definition? There are plenty of ways to meet and communicate with people that are somewhat private and anonymous, but a social network (on the internet or in meatspace) is not one of them.
And what happens when a drive goes bad at 3 am? I understand these are mostly mirroring content to be closer to the user, so all you'd get is increased latency when the data isn't more closely available, but who is going to want to have some maintenance tech over to their basement a couple times a year to replace a dead hard drive or blade server?
And how do you handle liability? If a pipe bursts and floods the place, who eats the loss for the equipment (or whose insurance company more likely)? What about a break-in?
An alternate approach might be to have a medium-sized data center, where all the hardware is inside a dedicated building and tended to by the usual acolytes, and have the waste heat serve as an input to a heating district of several nearby buildings. Unfortunately, 40-50 C heat is especially low grade from a building systems standpoint, so even this idea may not fly.
I started wondering if the radioactive decay in the RTGs would have resulted in a significant loss of mass, and if that could have any effect. I am sure that JPL and others have looked at it in detail, and would have accounted for it if it were significant. Still, I was curious...
It's a bit tough to estimate, because the power output of the RTGs has diminished over the years, and I'm not interested in doing integrals this early in the morning. Their electrical output at launch was about 155 W, meaning that the heat output was probably more than 1 kW. Because it's an easy number to work with, let's estimate using 1 kW average thermal output over the mission life:
As a lovely demonstration of just how big a number the speed of light is, using E=mc^2 equates that energy to a whopping 13 micrograms.
So, yes, they have lost measurable mass. But, no, it is probably insignificant to the orbital mechanics at work. The rest of Pioneer weighed over 250 kg at launch. It probably picked up more than 13 ug in dust and solar wind.
I think that the 60% figure is not efficiency in the sense of Solar Power In / Electrical Power Out, or some sort of Carnot efficiency like is usually applied to a nuclear power plant. I think they mean that the output of all the turbines at peak is 200 MW, but because the sun doesn't shine all day, every day of the year, their average utilization of that peak output is 60%.
The tower is rated for 200 MW, with an estimated utilization of 60%. So the average power output is about 120 MW.
Wholesale electricity prices in the United States are 40-100 $ / MWhr. This should be able to provide most of its power during peak usage, which is great from a business model. Plus they can command a bit of a premium from the California ISO because it is renewable, and California has a 33% renewable mandate. Let's assume 60 $/MWhr.
In each year there are 24 * 365 = 8760 hours. So the company's annual revenue should be in the ballpark of $65 M/yr.
The estimated cost to build the thing is $750M, and their estimated payback period is 11 years. That doesn't quite jive with the numbers I've come up with, and doesn't take into account net-present-value calculations, financing costs, operating expenses, etc. But, even so, you should certainly be able to pay for the thing over its many-decades-long lifetime.
For this specific case: not many hurricanes in Arizona, nor in most every desert.
More generally: site selection and engineering for the weather are surely taken into account before they break ground. The tower is freestanding and attached to the ground - the greenhouse is built around it, not the other way around. Even if the company glosses over stability in inclement weather, it should be caught in the permitting process. And even if it isn't accounted for during permitting, you can bet the insurers and underwriters will want good answers. Even so, this probably isn't ideal technology for, say, coastal Florida.
The National Academy of Engineering had an article a long while ago about the Challenges of Landing on Mars, detailing the various merits of the systems used for Viking, Pathfinder/Spirit/Opportunity, and the upcoming Curiosity. It's a little dry, but it explains with good reasoning why the chosen landing solution is appropriate for Curiosity.
They opted to not use solar panels for this mission for a couple of reasons:
1) This spacecraft is much bigger, and requires more power to get around (solar cell power increases with area, but weight goes up with volume!) They want Curiosity to travel many kilometers during its mission, and mobility is (power) expensive.
2)The science payload is tremendous and has a huge number of capabilities, but also requires a lot of power. The video mentioned a laser that can vaporize rock, for instance.
3) The RTG on this thing should provide reliable and lasting power for at least the length of the rated 2-year mission - and beyond. Recall that the Spirit and Opportunity only originally had a 90-day mission life, in part because they estimated the solar array power would be greatly diminished after that. The RTG on Curiosity should be able to provide 80% of its initial power even after a decade on the surface.
4) In addition to the electrical power, the RTG will provide ample "waste heat" that will be used to keep the interior of the spacecraft warm, so that operations can continue through the Martian winter when sunlight is scarce and temperatures are cold.
In short, they did it because an RTG is a much more abundant and long-lived power source for this size craft. It is similar to the arguments made in favor of nuclear power over photovoltaics on Slashdot. Some more information can be found here and here.
Schindler: There's no way I could have known this before, but there was always something missing. In every business I tried, I can see now it wasn't me that had failed. Something was missing. Even if I'd known what it was, there's nothing I could have done about it, because you can't create this thing. And it makes all the difference in the world between success and failure. Emilie: Luck? Schindler: War.
To be fair, I doubt the average person is aware that a password can include symbols unless they are specifically advised that they are allowable. I know I've been scolded by many computers, web sites, and electronic systems for using symbols in the past so its no wonder that they are rarely used.
I was floored when, just a few months ago, I went to set up online access for a new credit card. The site wouldn't let me do some of my usual substitutions, such as ! for i (or 1, or I, or |), because the site couldn't handle passwords with non-alphanumerics. No symbols? No punctuation? Lowercase letters and numbers only?! I can understand most dolts not using them, but to put artificial restrictions on a savvy user is downright stupid!
I have contacted their website support people, and am shocked, shocked that I haven't heard back or seen a change in their policy. No wonder every one of these banks has been hacked.
And do you think the Instrumentation Laboratory just happened to already have all those guys sitting around doing nothing in particular? No, NASA came along, asked them for a guidance computer, and gave them a lot of money to expand: gather lots more smart people, buy them lots of technology, and make it happen. Without NASA's need or its money, the Instrumentation Laboratory wouldn't have had as many smart people working together developing new and cool things.
And that's just one example. The Apollo program employed hundreds of thousands of people, most of them via contracts to private companies. And what is wrong with that? There isn't anything wrong or misleading about the statement that NASA, in tackling Apollo, brought, recruited, trained, and salaried huge numbers of smart people for a common purpose: and society benefited.
Alright then: self defense. When the russkies (or whoever the hell you want) invade the U.S., are you going to defeat the invading armies by nuking our own country? Or do you just fall back on Mutually Assured Destruction and hope that the other side takes the hint? Military strategy, particularly defensive strategy, cannot be based solely on that.
And while "just have a military for self defense" may work for most nations, it unfortunately isn't so simple for the U.S. Although we are very inconsistent and haphazard about it, we do have a duty to the rest of civilization to throw our weight around to protect others across the globe. Sometimes throwing our weight around involves guys with guns and cruise missiles. You can't combat a Rwandan genocide with nukes.
We've done a lot of work with computer models since we're no longer willing to test fire any of these weapons, even underground.
It's not that we are unwilling, it's that we have bound ourselves by treaties not to, as is most of the rest of the world. If you can test to verify your models, you can test to develop better weapons, because no outside observer can tell the difference. Then we are right back in the middle of the nuclear arms race.
So any time we need to use military force, all we're left with is to nuke someone, or to talk all hot and bothered about how we're gonna nuke someone? Any time we want to retaliate against a terrorist organization, let alone a nation-state, our only recourse would then be to either 1) nuke any and everything within a 10 mile radius of the target or 2) do nothing and fecklessly whine about it. What the hell good is that?
HAHAHA! If game developers don't fight back against lousy working conditions, domineering managers, horribly long hours on measly salary, unrealistic performance expectations, and changing requirements and deadlines, they sure as hell aren't going to fight back against such a low priority as how microtransactions get abused in gameplay.
"Dammit, they've worked me like a dog! 80 hours a week for months! Whips on my back! Low contrast monitors destroying my eyes! Gruel for every meal! But they'll have to pry the keyboard from my cold dead hands before they ruin the character of this masterpiece with [spit] microtransactions!"
In newer machines, there is sometimes the option for the spindle to be an air-bearing, so that it can hit 10,000 to 50,000 rpm without either 1) exploding or 2) melting.
The externally-driven air bearing was there for experimental control and convenience. In reality the airgap would be established solely by spinning the fan disc.
Air bearings are used in several awful environments. For instance, they are used extensively in high-speed, high-precision CNC mills: an environment filled with metal chips, splashing coolant, smoke fumes, etc.
The prototype device is configured as a static (externally pressurized) thrust bearing. In real-world thermal management applications such an externally pressurized air bearing would be replaced by a hydrodynamic (self-pressurizing) air bearing, which uses a minute fraction of the mechanical power supplied by the brushless motor to generate the required lifting force. For experimental measurements, however, an externally pressurized air bearing is preferable because it allows the air gap distance to be varied systematically, and over a wide dynamic range.
I note the pressure guage next to the device.
This is presumably connected to a large compressor, providing reasonable rates of high pressure air, as you need for air bearings.
The average PC however doesn't actually have this.
Although Figure 10 of the article shows and labels the pressure regulator, gauge, manifolds, etc., those are there to create an air bearing with a well-defined gap that they use for characterization and calibration. In practice, none of that claptrap is necessary: the air layer will be created entirely by the rotation of the fan disc. This is more or less the same as the tiny layer of air that is created under the read/write head of a harddrive.
Slashdot Mirror
A less sinister and conspiratorial reason might simply be that, now that the launch complex isn't seeing a shuttle launch every couple of months, there's a good bit of downtime to do the cleanup without interfering with launch operations.
Real men don't even bother with commas because REAL MEN DON'T SLOW DOWN FOR F&#KING ANYTHING!
Unfortunately, the speed with which it gets there is only a small amount of the total energy you need to expend to get something from the Earth to the Moon. The Apollo craft (Command/Service Module + Lunar Excursion Module) together weighed about 45,000 kilos, and it took a Saturn V to get it there. The first two stages of the Saturn V could get about 100,000 kg to LEO. About half of that was the Apollo craft, and the other half was the third stage that boosted Apollo from LEO into a lunar transfer.
The ISS is over 400,000 kilos, about 9 times as massive as Apollo. So (ballparking here) you'd need the equivalent of 4-5 Saturn V, or a few dozen Delta-IV / Ariane-5, rockets to get enough propellant to LEO to subsequently boost the station to the moon. Maybe we'll have more options as we near 2020 (e.g., Falcon Heavy), but that is only to get the fuel up to the station. Once you get the propellant up there, you'd need to have mechanisms for attaching the rocket(s) to the station, ganging the fuel tanks together, balancing the mass amongst them, etc.
And once you got it kicked off to the Moon, what would you do with it? The ISS isn't really designed to operate outside of LEO. Radiation will be a problem for both the station and its occupants.
Isn't a social network non-private by definition? There are plenty of ways to meet and communicate with people that are somewhat private and anonymous, but a social network (on the internet or in meatspace) is not one of them.
And what happens when a drive goes bad at 3 am? I understand these are mostly mirroring content to be closer to the user, so all you'd get is increased latency when the data isn't more closely available, but who is going to want to have some maintenance tech over to their basement a couple times a year to replace a dead hard drive or blade server?
And how do you handle liability? If a pipe bursts and floods the place, who eats the loss for the equipment (or whose insurance company more likely)? What about a break-in?
An alternate approach might be to have a medium-sized data center, where all the hardware is inside a dedicated building and tended to by the usual acolytes, and have the waste heat serve as an input to a heating district of several nearby buildings. Unfortunately, 40-50 C heat is especially low grade from a building systems standpoint, so even this idea may not fly.
I started wondering if the radioactive decay in the RTGs would have resulted in a significant loss of mass, and if that could have any effect. I am sure that JPL and others have looked at it in detail, and would have accounted for it if it were significant. Still, I was curious...
It's a bit tough to estimate, because the power output of the RTGs has diminished over the years, and I'm not interested in doing integrals this early in the morning. Their electrical output at launch was about 155 W, meaning that the heat output was probably more than 1 kW. Because it's an easy number to work with, let's estimate using 1 kW average thermal output over the mission life:
1 kW * 60 sec/min * 60 min/hr * 24 hr/day * 365.25 day/yr * 39 yr = 1.2e12 Joules
As a lovely demonstration of just how big a number the speed of light is, using E=mc^2 equates that energy to a whopping 13 micrograms.
So, yes, they have lost measurable mass. But, no, it is probably insignificant to the orbital mechanics at work. The rest of Pioneer weighed over 250 kg at launch. It probably picked up more than 13 ug in dust and solar wind.
Perhaps a lesson in history is in order:
The Summary: "Dec. 7 — a day that would live in spaceflight history"
Franklin Delano Roosevelt: "December 7, 1941—a date which will live in infamy"
I think that the 60% figure is not efficiency in the sense of Solar Power In / Electrical Power Out, or some sort of Carnot efficiency like is usually applied to a nuclear power plant. I think they mean that the output of all the turbines at peak is 200 MW, but because the sun doesn't shine all day, every day of the year, their average utilization of that peak output is 60%.
Sigh... I have a pen, anyone have an envelope?
The tower is rated for 200 MW, with an estimated utilization of 60%. So the average power output is about 120 MW.
Wholesale electricity prices in the United States are 40-100 $ / MWhr. This should be able to provide most of its power during peak usage, which is great from a business model. Plus they can command a bit of a premium from the California ISO because it is renewable, and California has a 33% renewable mandate. Let's assume 60 $/MWhr.
In each year there are 24 * 365 = 8760 hours. So the company's annual revenue should be in the ballpark of $65 M/yr.
The estimated cost to build the thing is $750M, and their estimated payback period is 11 years. That doesn't quite jive with the numbers I've come up with, and doesn't take into account net-present-value calculations, financing costs, operating expenses, etc. But, even so, you should certainly be able to pay for the thing over its many-decades-long lifetime.
For this specific case: not many hurricanes in Arizona, nor in most every desert.
More generally: site selection and engineering for the weather are surely taken into account before they break ground. The tower is freestanding and attached to the ground - the greenhouse is built around it, not the other way around. Even if the company glosses over stability in inclement weather, it should be caught in the permitting process. And even if it isn't accounted for during permitting, you can bet the insurers and underwriters will want good answers. Even so, this probably isn't ideal technology for, say, coastal Florida.
The National Academy of Engineering had an article a long while ago about the Challenges of Landing on Mars, detailing the various merits of the systems used for Viking, Pathfinder/Spirit/Opportunity, and the upcoming Curiosity. It's a little dry, but it explains with good reasoning why the chosen landing solution is appropriate for Curiosity.
In short, they did it because an RTG is a much more abundant and long-lived power source for this size craft. It is similar to the arguments made in favor of nuclear power over photovoltaics on Slashdot. Some more information can be found here and here.
source
I was floored when, just a few months ago, I went to set up online access for a new credit card. The site wouldn't let me do some of my usual substitutions, such as ! for i (or 1, or I, or |), because the site couldn't handle passwords with non-alphanumerics. No symbols? No punctuation? Lowercase letters and numbers only?! I can understand most dolts not using them, but to put artificial restrictions on a savvy user is downright stupid!
I have contacted their website support people, and am shocked, shocked that I haven't heard back or seen a change in their policy. No wonder every one of these banks has been hacked.
And do you think the Instrumentation Laboratory just happened to already have all those guys sitting around doing nothing in particular? No, NASA came along, asked them for a guidance computer, and gave them a lot of money to expand: gather lots more smart people, buy them lots of technology, and make it happen. Without NASA's need or its money, the Instrumentation Laboratory wouldn't have had as many smart people working together developing new and cool things.
And that's just one example. The Apollo program employed hundreds of thousands of people, most of them via contracts to private companies. And what is wrong with that? There isn't anything wrong or misleading about the statement that NASA, in tackling Apollo, brought, recruited, trained, and salaried huge numbers of smart people for a common purpose: and society benefited.
Alright then: self defense. When the russkies (or whoever the hell you want) invade the U.S., are you going to defeat the invading armies by nuking our own country? Or do you just fall back on Mutually Assured Destruction and hope that the other side takes the hint? Military strategy, particularly defensive strategy, cannot be based solely on that.
And while "just have a military for self defense" may work for most nations, it unfortunately isn't so simple for the U.S. Although we are very inconsistent and haphazard about it, we do have a duty to the rest of civilization to throw our weight around to protect others across the globe. Sometimes throwing our weight around involves guys with guns and cruise missiles. You can't combat a Rwandan genocide with nukes.
It's not that we are unwilling, it's that we have bound ourselves by treaties not to, as is most of the rest of the world. If you can test to verify your models, you can test to develop better weapons, because no outside observer can tell the difference. Then we are right back in the middle of the nuclear arms race.
So any time we need to use military force, all we're left with is to nuke someone, or to talk all hot and bothered about how we're gonna nuke someone? Any time we want to retaliate against a terrorist organization, let alone a nation-state, our only recourse would then be to either 1) nuke any and everything within a 10 mile radius of the target or 2) do nothing and fecklessly whine about it. What the hell good is that?
HAHAHA! If game developers don't fight back against lousy working conditions, domineering managers, horribly long hours on measly salary, unrealistic performance expectations, and changing requirements and deadlines, they sure as hell aren't going to fight back against such a low priority as how microtransactions get abused in gameplay.
"Dammit, they've worked me like a dog! 80 hours a week for months! Whips on my back! Low contrast monitors destroying my eyes! Gruel for every meal! But they'll have to pry the keyboard from my cold dead hands before they ruin the character of this masterpiece with [spit] microtransactions!"
But they'll also need to create a breed of super dogs: the super dogs with super bees in their mouths, so that when they bark they shoot bees at you.
[obscure?]
This is an interesting example. However, I think it fair to say that the headline could be made more generic:
Dangers of [X] in [Country Wired in Civil War, Corruption, Insurgency, and Foreign Occupation]
In newer machines, there is sometimes the option for the spindle to be an air-bearing, so that it can hit 10,000 to 50,000 rpm without either 1) exploding or 2) melting.
Examples: (1), (2)
The externally-driven air bearing was there for experimental control and convenience. In reality the airgap would be established solely by spinning the fan disc.
Air bearings are used in several awful environments. For instance, they are used extensively in high-speed, high-precision CNC mills: an environment filled with metal chips, splashing coolant, smoke fumes, etc.
Although Figure 10 of the article shows and labels the pressure regulator, gauge, manifolds, etc., those are there to create an air bearing with a well-defined gap that they use for characterization and calibration. In practice, none of that claptrap is necessary: the air layer will be created entirely by the rotation of the fan disc. This is more or less the same as the tiny layer of air that is created under the read/write head of a harddrive.