Either this takes more power for the light than you get from the power plant, or you have a perpetual motion machine.
The Sun is not a perpetual source of energy, but for all intents and purposes on our scale, it is a good approximation of it.
And if your light source (sunlight?) actually does provide more power than the plant produces, why bother with coal?
You have a point. It would be better to use solar power as far as greenhouse effect is concerned. (Overall, I believe nuclear might be cleaner because building solar cells and covering the landscape with them isn't too environment-friendly either.)
However, in our case, it's too late; the coal (and oil, and whatever) has already been burned. We have to take that carbon back, or let Mother Nature take care of that, but stop emitting more of it...
Just incorporate a suicide gene or two and that's it, they'll all die on command.
However, once they have scrubbed all that extra CO2 from the atmosphere and they're all dead, what do we do with them? Burn them, bury them? They'll be decomposed one way or the other. What do they become then, especially all the carbon they've been storing all that time? Eventually CO2. Oh, wait...
All right, maybe I'm a little pessimistic; after all, that's how oil formed in the first place (with plants instead of bacteria), isn't it? Still, better not make mistakes when the time comes to get rid of them.
So costly that NASA literally couldn't build a spare, so this is only a one shot deal.
<rant>
It is not particularly uncommon in this program.
Was there a backup to the Service module which delayed the program two years? (The ICM could have been, sort-of, but was never built.) This led to the first two modules, Zarya and Unity, exceeding their 500-day lifetime in orbit; what would have happened if they had failed?
And what about the space shuttle? More than thirty shuttle flights are required to build the station; at a 1/450 estimated failure rate, according to the Aerospace Safety Advisory Panel, there is a 7-odd percent chance of another Challenger before it is completed - and the tight schedule surely is not going to help. If that happens, how does the program survive, with the Russians almost too broke to produce enough Soyuz even for the normal operation of the ISS?
That said, who won't be happy to learn that, according to NASA Watch, the Destiny lab's software wasn't even validated before launch? Or that there is a catch-22 with its avionics (computers and stuff need cooling to operate, but they need to be up to start the cooler systems)...
There is another issue: the project also depends on hundreds of hours of EVA (spacewalking), which the US lacks experience at. I don't have a reference handy, but IIRC one of the proposals to replace the space station Freedom program had been dismissed as too risky because it required way too much EVA time, and that was still less than what the ISS needs.
There is always the argument that the space program is indeed risky, but the prize is worth the game. I would agree with this, if the prize was space colonization, or at least common access to space. But this is not what NASA is after; see the jaundiced view they have about the Tito flight to ISS (set up by MirCorp and the Russians). According to the Space Frontier Foundation, "
NASA is clueless about how to efficiently and fairly run this facility. They're not interested in anything but their own budget, people and programs." Space science, then? A manned facility is not really adapted to that (life support systems, people bouncing around, degrade the quality of microgravity) except for studying the effect of weightlessness on the astronauts themselves, which has already been done well enough on Mir.
There is an article from the Economist about the "waste of space" the ISS is.
</rant>
And yet, I crave for more coverage of the ISS operation, more pictures of the beautiful thing they are building up there... I was at my window a few minutes ago as the ISS was passing overhead (cloudy sky, didn't see anything but I tried), and I'm following the EVA thanks to the Spaceflight now live coverage. I can't help dreaming about that 2001 double wheel giant station, and what moved me most in recent years was reading old newspapers from around july20th, 1969. Go figure...
Wouldn't all these titles and hierarchical dependences vary with the company itself? Isn't one free to have a company with Central Evacuation Organisators reporting directly to the Commander of Individual Offices? Or, to be more serious, why can't they decide whether CIO/CTOs should report to the COO or directly to the CEO?
Suddenly my potential audience goes from "90% of all Web-enabled systems" to "whoever's left that didn't disable the plugin"... sheesh.
Well, sorry about that, but I'll answer the same thing I told the WWW designer who wanted my university's website to depend on JavaScript (ironically, there was some ShockWave Flash too):
I, as a person who browses the Web, don't know you. I can't know you're not "hostile"; if your site depends on a security hole in my browser, I'll bitch and go elsewhere, that's all. You have to adapt, not I, I'm afraid...
There have been a lot of comments, totally justified IMO, about how this new Celeron is still completely underpowered and overpriced in comparison to AMD's Duron and even Athlon CPUs.
However, what about the power consumption of these babies? If I'm not mistaken, the Celeron has had some success with laptop manufacturers due to its lower requirements (read: longer battery lifetime), right? Now, does anybody know how the Duron compares in this respect?
I'm not really an expert at that, but since the Duron is an Athlon Thunderbird with "only" 64kB of L2 cache (but the full 128kB of the L1 cache), the closest would be Athlon/K7.
Follow the link "Print this article" at the bottom of the page if you have JavaScript enabled, or simply replace the "showdoc" by "printarticle", as in this link.
If my network connection is down, how do I work offline?
If focus is put on protecting the data itself as opposed to its storage location, what happens when some secret service first succeeds in quantum computers or whatever device capable of decrypting anything our current cryptographic technology can produce?
Isn't this more of a server concern? I mean, even if my system was "compromised" (the official-sounding wording in the FAQ) why would I truly care?
Section5.2 of the FAQ covers this. Kind of. Do you want to explain to the police that you didn't know about the warez and child porn on your hard drive?
All-in-all, would I even need security if there wasn't the internet? If the machine was just sitting in my room and the only thing that could "attack it" is a 12-year old brother with a misladen hockey stick? Probably not.
Less so, maybe, does your 12-year-old brother never swap Word documents or games with friends? But then who would want to disseminate viruses and trojans, they serve no purpose, right?
It looks like a good document about Linux security, but I thought the questions that were really asked often in comp.os.linux.security were of the kind:
I can't telnet to my machine as root!
Process belonging to `nobody', have I been cracked?
I did read that in experiments, the Ion Drive could top out about 39,000 miles an hour. What that translates to in F/P thrust I have no idea.
There is no direct relationship between thrust and top speed, it depends how long you can thrust; in the case of ion drives, it can mean months or years.
A better way to apprehend things is the rocket equation: if u is the exhaust speed and m0 and m1 the mass of the spacecraft respectively empty and fueled, then an ideal rocket in a vacuum in a weightless environment can change your speed of:
Deltav=u.ln(m1/m0).
And the tests have not been fully performed in a weightless environment where the maximum potetial momentum can be reached.
Wait, what about Deep Space1? The thing is now on the other side of the solar system, has visited a comet last year, and is on its way to a second, I think. And it has totaled almost two years of thrusting, weeks or months at a time!
As for traveling at lightspeed, surely it is a step ahead of chemical propulsion, but we still have a long way before we can even approach even fractional lightspeed! Try looking at the rocket equation above; an ion drive typically accelerates its exhaust up to 10-20km/s (compared to less than 5km/s for chemical rockets). To reach a thousandth of lightspeed, in the best case, you'll need over three million times as much fuel as the mass of your spacecraft, which includes the fuel tank, of course. Quite a challenge...
What's this? Would that be Plutonium ion degeneration powering all of the RTG's
That's a Radioisotope Thermoelectric Generator. It is a device that produces electricity by using the heat which the radioactive decay of the plutonium inside yields. It is used as a power source for the instruments and electronics aboard the spacecraft.
An ion drive, on the other hand, is a propulsion system in which propellant is ionized (that is, the atoms or molecules gain or lose electrons), thus becoming electrically charged so that it can be accelerated at high speed and expelled from the spacecraft. The exhaust speed being much higher than for conventional chemical rockets, the engine is far more efficient. The drawback is that the rate of propellant ionization can't be very high, so the thrust is extremely weak.
So, you see, an RTG and an ion drive are totally different beasts: one produces power, the other consumes power and converts it to thrust. And it is conceivable to use both in a complementary way, as in having an ion thruster powered by an RTG; a very sensible solution for missions to Jupiter and beyond, IMO.
(And my apologies if you found my previous reply overly dry...)
and the atmosphere of Jupiter is predominantly methane gas,
I don't think it is; rather hydrogen, but I could be wrong.
if the two were to come close enough to each other,
Cassini has passed the point of closest approach. 10million kilometers, give or take.
where would be the best place be to view the fireworks from?
What fireworks?
I often wonder how the atmosphere is so stabilized in it's current state, that it maintains such well divided regions of different types of gas clouds. It changes with the day, but the large spots have never moved.
Well, you're not the only one. I think the meteorology of Jupiter is one of the mysteries of planetology. Think of the Great Red Spot, twice as big as Earth, has existed since we are able to point telescopes at planets... Wouldn't it be nice if our cyclones persisted for centuries?
We went to the moon, we got some rocks, we dropped a feather and a bowling ball, then went home. NASA ran away and abandoned the project, what I want to know is why.
Because the goal of the Apollo project, which was to give the finger to the Soviets, had been reached. Nixon needed money for the Vietnam war, and NASA's budget was one that could be cut off. Plus the fact that it was costly compared to the results it yielded, for the very same reason as above.
You might want to read Stephen Baxter's "Voyage", featuring an alternative reality in which the US gets on to Mars after the Apollo flights. With a good demonstration of how the political machinery between NASA, the White House, the militaro-industrial complex, etc., works...
We could easily be taking holidays on the moon, but NASA don't want any more research done into the moon.
It's not that they don't want that; they do want to go back to the Moon, Mars and wherever you give them money to go with! That's the problem, you see, not only are they not really able to get results on the cheap - by their very nature as an administration, IMO - but Congress won't give it anyway, as it is perceived as being expensive, implies a lot of politics, and so on.
I WANNA GO TO THE MOON.
Shall I say "AOL"? Actually, no, I wanna live on the Moon.
As long as it takes for trips to Jupiter and Saturn, I'm beginning to realize that I will never see the day that a human walks on any of either planet's moons
Don't lose all hope yet... Between all those start-ups trying to democratize cheap access to space, growing interest about possible life on Europa, and the ever-growing life expectancy, there might be a little chance?
(39 between them, right?).
About that. Maybe a bit more, some have been discovered recently. And that doesn't account for the rings, of course...
Landing on the moon was great, but that was before my time. No one's walked on Mars yet, so hopefully I'll see that.
AOL.
No one will ever walk on Jupiter, I realize this.
Hot hydrogen balloons, anyone? Saw that in one of Clarke's stories...
Com'on NASA, all I want for Christmas is to hear about some John Smith walking on the moon...
No. What I want for Christmas is to hear about someone settling on the Moon. Alive, of course. And preferably myself.
yeah that moon about 200 million miles away. Talk about a leap for mankind...
About 240,000 actually. Which makes it all the worse... Do you realize that no human has gone farther than a few hundred kilometers from the surface of the Earth for almost 30years?!
What exactly is accomplished with a planet "flyby" anyway?
Better that than nothing. Gives some opportunities for remote observations, and a little push for a longer journey...
Right now, according to this Solar System Simulator image, Cassini is about 630million kilometers away from Saturn
(which amounts to 390million miles, or 4.2AUs).
As for the speed, it also changes all the time, you know, trading kinetic energy for potential energy, Kepler's laws, all that stuff. According to this page, it is moving at about 47,500kilometers an hour, with respect to the Sun, I assume (29,500mph, 13km/s), but it will slow down a lot as it gets farther from Jupiter and the Sun.
Well, according to 2010, we have to wait for the Chinese to claim this convenient refueling station and discover life there. They are currently preparing for a second (unmanned) test flight of their Shenzhou spacecraft, so there's still hope...
As for the pictures, why don't you have a look there?
Funny, 2001 is just about to air on cable TV here...
Anyway, I heard the mission had been canceled due to the failure to find a Monolith on the Moon (or settle the Moon, for that matter), manufacture reliable gas-core nuclear fission engines, and AIs. And bug-free software, too, but that would definitely not have stopped them, as we all know.
Jupiter is completely unhabitable! Why invest millions into studying it when we won't find a use in it?
Well, Cassini is currently using Jupiter, to propel it towards Saturn! OK, you'll answer that Saturn is unhabitable too, but:
both Jupiter and Saturn have large, planet-sized moons, which may one day be colonized;
life may exist there or on the moons (subsurface oceans on Europa and possibly Ganymede and Callisto, an atmosphere and hydrocarbons around Titan, not to mention the possibility of "aerial" life in the atmospheres of the gas giants themselves);
the planets are interesting in themselves, for the sake of science; Cassini's worth a few billion dollars, negligible compared to the useless space station's skyrocketing costs;
setting up bases on the Moon and Mars is good too, but we unfortunately lack the political will.
As the article states, Cassini has passed the point of closest approach two days ago. Which means it is currently receding away from Jupiter, past mid-flyby, on its way to Saturn.
Yes, there had been some problems with the maneuvering systems, which had halted observations for a few days, but a lot of science has already been done. Indeed, having two spacecraft in the vicinity of the same planet is quite an opportunity, and had not happened before except in the case of Mars (and the Earth, of course).
Also, AFAIK, this is only the fourth spacecraft in history to perform a Jupiter gravity assist (the first three being Voyager 1 and 2, and Ulysses).
Far too few, IMO. The Discovery doesn't count.
Slashdot Mirror
The Sun is not a perpetual source of energy, but for all intents and purposes on our scale, it is a good approximation of it.
You have a point. It would be better to use solar power as far as greenhouse effect is concerned. (Overall, I believe nuclear might be cleaner because building solar cells and covering the landscape with them isn't too environment-friendly either.)
However, in our case, it's too late; the coal (and oil, and whatever) has already been burned. We have to take that carbon back, or let Mother Nature take care of that, but stop emitting more of it...
However, once they have scrubbed all that extra CO2 from the atmosphere and they're all dead, what do we do with them? Burn them, bury them? They'll be decomposed one way or the other. What do they become then, especially all the carbon they've been storing all that time? Eventually CO2. Oh, wait...
All right, maybe I'm a little pessimistic; after all, that's how oil formed in the first place (with plants instead of bacteria), isn't it? Still, better not make mistakes when the time comes to get rid of them.
Someone has had a bad experience of the Admin Horror Stories kind, rm-rf/ and the like?
<rant>
It is not particularly uncommon in this program. Was there a backup to the Service module which delayed the program two years? (The ICM could have been, sort-of, but was never built.) This led to the first two modules, Zarya and Unity, exceeding their 500-day lifetime in orbit; what would have happened if they had failed?
And what about the space shuttle? More than thirty shuttle flights are required to build the station; at a 1/450 estimated failure rate, according to the Aerospace Safety Advisory Panel, there is a 7-odd percent chance of another Challenger before it is completed - and the tight schedule surely is not going to help. If that happens, how does the program survive, with the Russians almost too broke to produce enough Soyuz even for the normal operation of the ISS?
That said, who won't be happy to learn that, according to NASA Watch, the Destiny lab's software wasn't even validated before launch? Or that there is a catch-22 with its avionics (computers and stuff need cooling to operate, but they need to be up to start the cooler systems)...
There is another issue: the project also depends on hundreds of hours of EVA (spacewalking), which the US lacks experience at. I don't have a reference handy, but IIRC one of the proposals to replace the space station Freedom program had been dismissed as too risky because it required way too much EVA time, and that was still less than what the ISS needs.
There is always the argument that the space program is indeed risky, but the prize is worth the game. I would agree with this, if the prize was space colonization, or at least common access to space. But this is not what NASA is after; see the jaundiced view they have about the Tito flight to ISS (set up by MirCorp and the Russians). According to the Space Frontier Foundation, " NASA is clueless about how to efficiently and fairly run this facility. They're not interested in anything but their own budget, people and programs." Space science, then? A manned facility is not really adapted to that (life support systems, people bouncing around, degrade the quality of microgravity) except for studying the effect of weightlessness on the astronauts themselves, which has already been done well enough on Mir.
There is an article from the Economist about the "waste of space" the ISS is.
</rant>
And yet, I crave for more coverage of the ISS operation, more pictures of the beautiful thing they are building up there... I was at my window a few minutes ago as the ISS was passing overhead (cloudy sky, didn't see anything but I tried), and I'm following the EVA thanks to the Spaceflight now live coverage. I can't help dreaming about that 2001 double wheel giant station, and what moved me most in recent years was reading old newspapers from around july20th, 1969. Go figure...
I guess you'll have to ask them...
Aren't G4 Cubes supposed to cool thanks to a chimney-like mechanism? How does one do that in a vacuum (or use a fan, for that matter)?
So, what's that, Earth to Mars In Two Weeks?
Well, sorry about that, but I'll answer the same thing I told the WWW designer who wanted my university's website to depend on JavaScript (ironically, there was some ShockWave Flash too): I, as a person who browses the Web, don't know you. I can't know you're not "hostile"; if your site depends on a security hole in my browser, I'll bitch and go elsewhere, that's all. You have to adapt, not I, I'm afraid...
However, what about the power consumption of these babies? If I'm not mistaken, the Celeron has had some success with laptop manufacturers due to its lower requirements (read: longer battery lifetime), right? Now, does anybody know how the Duron compares in this respect?
I'm not really an expert at that, but since the Duron is an Athlon Thunderbird with "only" 64kB of L2 cache (but the full 128kB of the L1 cache), the closest would be Athlon/K7.
Follow the link "Print this article" at the bottom of the page if you have JavaScript enabled, or simply replace the "showdoc" by "printarticle", as in this link.
Section5.2 of the FAQ covers this. Kind of. Do you want to explain to the police that you didn't know about the warez and child porn on your hard drive?
Less so, maybe, does your 12-year-old brother never swap Word documents or games with friends? But then who would want to disseminate viruses and trojans, they serve no purpose, right?
No?
There is no direct relationship between thrust and top speed, it depends how long you can thrust; in the case of ion drives, it can mean months or years.
A better way to apprehend things is the rocket equation: if u is the exhaust speed and m0 and m1 the mass of the spacecraft respectively empty and fueled, then an ideal rocket in a vacuum in a weightless environment can change your speed of: Deltav=u.ln(m1/m0).
Wait, what about Deep Space1? The thing is now on the other side of the solar system, has visited a comet last year, and is on its way to a second, I think. And it has totaled almost two years of thrusting, weeks or months at a time!
As for traveling at lightspeed, surely it is a step ahead of chemical propulsion, but we still have a long way before we can even approach even fractional lightspeed! Try looking at the rocket equation above; an ion drive typically accelerates its exhaust up to 10-20km/s (compared to less than 5km/s for chemical rockets). To reach a thousandth of lightspeed, in the best case, you'll need over three million times as much fuel as the mass of your spacecraft, which includes the fuel tank, of course. Quite a challenge...
That's a Radioisotope Thermoelectric Generator. It is a device that produces electricity by using the heat which the radioactive decay of the plutonium inside yields. It is used as a power source for the instruments and electronics aboard the spacecraft.
An ion drive, on the other hand, is a propulsion system in which propellant is ionized (that is, the atoms or molecules gain or lose electrons), thus becoming electrically charged so that it can be accelerated at high speed and expelled from the spacecraft. The exhaust speed being much higher than for conventional chemical rockets, the engine is far more efficient. The drawback is that the rate of propellant ionization can't be very high, so the thrust is extremely weak.
So, you see, an RTG and an ion drive are totally different beasts: one produces power, the other consumes power and converts it to thrust. And it is conceivable to use both in a complementary way, as in having an ion thruster powered by an RTG; a very sensible solution for missions to Jupiter and beyond, IMO.
(And my apologies if you found my previous reply overly dry...)
It is not.
I don't think it is; rather hydrogen, but I could be wrong.
Cassini has passed the point of closest approach. 10million kilometers, give or take.
What fireworks?
Well, you're not the only one. I think the meteorology of Jupiter is one of the mysteries of planetology. Think of the Great Red Spot, twice as big as Earth, has existed since we are able to point telescopes at planets... Wouldn't it be nice if our cyclones persisted for centuries?
Because the goal of the Apollo project, which was to give the finger to the Soviets, had been reached. Nixon needed money for the Vietnam war, and NASA's budget was one that could be cut off. Plus the fact that it was costly compared to the results it yielded, for the very same reason as above.
You might want to read Stephen Baxter's "Voyage", featuring an alternative reality in which the US gets on to Mars after the Apollo flights. With a good demonstration of how the political machinery between NASA, the White House, the militaro-industrial complex, etc., works...
It's not that they don't want that; they do want to go back to the Moon, Mars and wherever you give them money to go with! That's the problem, you see, not only are they not really able to get results on the cheap - by their very nature as an administration, IMO - but Congress won't give it anyway, as it is perceived as being expensive, implies a lot of politics, and so on.
Shall I say "AOL"? Actually, no, I wanna live on the Moon.
Don't lose all hope yet... Between all those start-ups trying to democratize cheap access to space, growing interest about possible life on Europa, and the ever-growing life expectancy, there might be a little chance?
About that. Maybe a bit more, some have been discovered recently. And that doesn't account for the rings, of course...
AOL.
Hot hydrogen balloons, anyone? Saw that in one of Clarke's stories...
No. What I want for Christmas is to hear about someone settling on the Moon. Alive, of course. And preferably myself.
About 240,000 actually. Which makes it all the worse... Do you realize that no human has gone farther than a few hundred kilometers from the surface of the Earth for almost 30years?!
Better that than nothing. Gives some opportunities for remote observations, and a little push for a longer journey...
It changes all the time, of course...
Right now, according to this Solar System Simulator image, Cassini is about 630million kilometers away from Saturn (which amounts to 390million miles, or 4.2AUs).
As for the speed, it also changes all the time, you know, trading kinetic energy for potential energy, Kepler's laws, all that stuff. According to this page, it is moving at about 47,500kilometers an hour, with respect to the Sun, I assume (29,500mph, 13km/s), but it will slow down a lot as it gets farther from Jupiter and the Sun.
Well, according to 2010, we have to wait for the Chinese to claim this convenient refueling station and discover life there. They are currently preparing for a second (unmanned) test flight of their Shenzhou spacecraft, so there's still hope...
As for the pictures, why don't you have a look there?
Anyway, I heard the mission had been canceled due to the failure to find a Monolith on the Moon (or settle the Moon, for that matter), manufacture reliable gas-core nuclear fission engines, and AIs. And bug-free software, too, but that would definitely not have stopped them, as we all know.
Well, Cassini is currently using Jupiter, to propel it towards Saturn! OK, you'll answer that Saturn is unhabitable too, but:
Is that enough?
As the article states, Cassini has passed the point of closest approach two days ago. Which means it is currently receding away from Jupiter, past mid-flyby, on its way to Saturn.
Yes, there had been some problems with the maneuvering systems, which had halted observations for a few days, but a lot of science has already been done. Indeed, having two spacecraft in the vicinity of the same planet is quite an opportunity, and had not happened before except in the case of Mars (and the Earth, of course).
Also, AFAIK, this is only the fourth spacecraft in history to perform a Jupiter gravity assist (the first three being Voyager 1 and 2, and Ulysses). Far too few, IMO. The Discovery doesn't count.
... so that people will no longer complain about the bugs in their spacecraft systems!