Um, nothing can do better than carnot efficiency, even with cogeneration... unless you are talking about heating water as useful energy or something.
Cogeneration can mean that, but it normally (well, for some values of normally) means that the waste heat from one carnot based cycle is used on another one.
Oh, and I notice that for some reason you do not include combined cycle plants? OK, if you throw out half the energy, then yes it would not be that efficient.
My recommendation: Do not throw out half the energy.
The particular one I had in mind was in a physical document, not online. Remember, that for space use you will spend enough to use top of the line parts no matter what method you choose. Online, the best I could find was in this link:
It has a micro-turbine generator available that is 80% efficient. (I don't know where that came from, the highest I had ever heard of was 70%)
As for the rest, we have never made any near a century life atomic batteries, and we have never tried to make a generator from this technology. It seems silly to argue about which would be better - at this point almost certaintly you would use an atomic battery, the other is not developed yet (R is done, D is not).
I'm just saying that working on this is a good idea!
The total mass issue is a problem only for small spacecraft (basically you are assuming that fuel is a low proportion of mass, I am assuming a high proportion). We are both right for different assumptions.
As for Carnot efficiency and such, I kept my post rather vague on that point intentionally. There are devices that achieve near carnot efficiency, and such devices tend to be low power as well. In your example you mention a steam generator - I think we both agree that it is unlikely that a steam generator would be launched. (However top of the line steam power plants are near 70% efficient, and so even that sort of goes against your point).
The breakeven point is dead on, but I never said the technology would work as is. I was really saying that the technology shows a lot of promise, even if it doesn't seem likely to provide high power levels (or even work at room temperature).
Your small nuclear generator design is interesting, but nuclear fuel tends not to last too well. Typically years, not decades.
Well, yes - but you could go further with this than an RTG (For the same mass, more energy available). It is true that the low temperatures would limit energy output, but one problem is keeping the spacecraft warm (well, near freezing actually). This could help with that, and provide a few watts of power. The radiator would be the spacecraft itself. Even at the fourth power, your spacecraft will be radiating on the order of 100 watts at 250-300 K. (Your example of 150 K is rather extreme - at that temperature you would get nearly 50% thermal efficiency - which means you would have to be ignoring other trade-offs)
To a certain extent, I think that they need to have work before they can complain about working conditions. That's what is missing in all this - the fact is that Indians that used to be in danger of starving to death trying to find a job are no longer in danger.
After the basic necessities of life are met, the masses will start complaining about working conditions. As long as people die from lack of food, no one will complain. So your actions, however nobly intended, probably have the wrong result...
Well, the term "cold fusion", if taken literally, can never be applied to any form of fusion we have imagined. On an atomic scale, the energy of a single atom is its "heat", and the 1 Mev or so required is extremely hot!
Personally, I think it is fair to call anything that has an average chamber temperature below 100 C "cold fusion", because it is cold enough to make apparatus design safe and easy.
Remember, cold is a relative term. Compared to a standard fusion reactor, the center of the sun is "cold".
That is such a moronic response! (Sorry, I really get sick of hearing things like that!)
What you mean is that you cannot think of an application. I can think of several, some of which would probably work almost as is. For example, it could be used to heat interstellar probes above 4 K - you have to take all your energy with you because interstellar space has no energy sources available. It works best in the cold - perfect for some applications.
Please, please do not assume that there are no applications just because you can't think of any!
Sorry, this just drives me nuts! I'll be quiet now...
What you say is true, but less true is deep space. Out beyond Jupiter or so, there is very little energy available. Everything is very low temperature, and radiation cooling very quickly gets you to extremely cold temperatures (40 K is reasonable, as I remember).
Something like this could work as a Mr. Fusion for deep space probes - it sounds like a perfect match. Deep Space probes typically don't even need that much power!
No, I said it right - they beat the theoretical maximum. (Of course, that just means that the theory doesn't account for everything, but even so no other engine has ever come close to that!)
The real problem is that in order to do that, they made an engine that really is not reusable. The engine has to be completely ripped down and refurbished between flights - thats why everything costs so much. The engine also is started via a magic process with hundreds of steps - so in orbit restart (or restart without hours of prep for that matter) are impossible.
The opposite is true of most of its predesesors. The RL-10 can be restarted as many times as necessary, and can run for hours with multiple restarts with no maintainence. (The X10 never had to do maintainence on its engines during the whole life of the program!)
Everyone now tries to make a shuttle engine copy - and they normally end up exploding (see Japan's J4 (I think)). Simple is good, people!
This is not really true, in order to change your orbit 90 degrees you need about 0.5 v change (or so, I forget the exact number).
Essentially, you first change the orbit from circular to extremely eliptical. Then you change directions when you are farthest from Earth. The you circularize the orbit. It works because the energy required to change directions is a lot less when you are at the extreme edge of an elliptic orbit, because you are so much slower.
It's even worse than this - all rocket development is done as a funded research project. Research projects that choose the easiest way to do something do not get funded! Research into hard things gets funded - so given the choice between making an existing rocket engine more reliable (easy) and making an existing rocket engine 0.0001% more efficient (hard), they choose efficiency.
By the way, the theoretical maximum efficiency of the space shuttle's engines is about 2% less than the actual - they obviously spent too much time on those engines...
Weirdly enough this is not true - you can build a compressive structure to Geo! It would be insanely expensive, but two things make it possible.
1. Using tension strength as compressive strength - you essentially use "balloons" sitting on top of each other, giving you a compressive strength equal to 1/2 tensile strength.
2. The taper works much better with a tower - most of the structure is at very near zero G, and so only needs to support the very thin low G structure above it. Conversely, a tension structure has to be thickest at the top.
To really understand the impact of #2, a compressive structure will have a HUGE base, but 500 km up will be a thin spike going the rest of the 30,000 km. A tension structure will be a thin thread for the first 500 km, and a thick structure for the rest of the 30,000 km.
Weird yes, but a compressive structure may be easier!
By the way, you are of course presuming that my definition of "me" matches your definition of "me" - which is apparently wrong. I believe I am essentially made up of the software, not the hardware - if you back up my conciousness and restore to a different body I will still consider that "me".
Even if it was a clone, and I was still alive - both "me"s would agree that we were both "me" and therefore had certain rights and obligations to each other.
Yes, it went into that as well. The hero (well, one of them) had sent himself to his death many times for the good of mankind - it even had a little part where the doomed copy contemplated his coming demise as he saw destruction rushing towards him.
Rather interesting, really. Would you be willing to die for a cause, assuming all you would lose was the last few minutes? (Of course, most people have several causes they would die for even without that - family, friends, etc.)
Absolutely! Game theory doesn't endorse anything - it just tries to explain why certain structures exist, endure, and work (for various definitions of "work").
I read an interesting book where they continuously backed up their conciousness onto indestructible recorders, so the only thing that could really "kill" you was if you were driven insane (or in this book, had your conciousness hacked into and taken over)
...this wouldn't be slashdot without your pedantic comment at the end...
Yep, you've got to add in a zinger just to make it conversational!
Game theory covers a lot of ground, but in general when you are discussing socio-economic advantages, you are talking game theory. (Any time you want to know what the best decision for society would be, whenever you want to predict your competitor's move, etc.)
Interesting stuff, really. But I am not really an expert - I just make decisions, I don't pretend to understand them...;-}
The answer is quite simple, really. Everyone is really better off when one person is in charge. In anarchy the wealth is evenly distributed, but the total wealth is far less because no one is willing to do anything. In a structured environment, wealth is created so even if the wealth is distributed unevenly everyone is better off. That is why the system works and is stable - everyone is better off, even the lowest members of society. (If you don't believe that, ask yourself why people don't just quit society and go live in the mountains - it is possible, at least in the US)
As for why the people at the top get more than an even distribution - its because it is hard to get to the top, and society is better off if it motivates people to reach the top. I know everyone says that CEOs are overpaid, etc. but good CEOs are extremely rare - and are therefore workth their weight in gold to society. If, as you seem to believe, it was an easy job then others would compete for the job and the board would tell the CEO "Hey, Joe here can do just as well as you, and he will work for peanuts!" The fact is, once you find a good CEO you don't let him go!
Of course, whining is much easier than studying the game theory that explains all this...
For the first part of your reply, I guess it just comes down to whom you trust more - charities or the government. My experiences led me one way, yours lead you another.
For the latter half, I was more thinking of welfare programs rather than social security. Right now, we have multiple programs - I think that getting rid of them could save a lot of money, and that very few people would stay at earning just $3/hr for very long. Most of our income taxes go towards funding welfare programs, which are really just another form of social security.
Your 0.4% is rather low for a retirement account (sound more like checking or easy-access savings). Normally, the longer you tie up the funds, the better the rate. Standard rates for totally secure investments are normally around 4%, or basically enough to just barely clear inflation. Open market bonds are 7-10%, and the stock market (such as index funds, which are relatively safe over a 40 year window) returns around 15%.
Some things to consider, however are these:
1. Inflation - most people use 3% in their planning.
2. Wages - As you start out, you will be making small bucks. If you save X% of your wages, in 5 years you will probably be making so much more that the amount saved previously doesn't really amount to much... at least that's what has happened to me.
Slashdot Mirror
Um, nothing can do better than carnot efficiency, even with cogeneration... unless you are talking about heating water as useful energy or something.
Cogeneration can mean that, but it normally (well, for some values of normally) means that the waste heat from one carnot based cycle is used on another one.
Oh, and I notice that for some reason you do not include combined cycle plants? OK, if you throw out half the energy, then yes it would not be that efficient.
My recommendation: Do not throw out half the energy.
Bull. Show me one...
. asp
The particular one I had in mind was in a physical document, not online. Remember, that for space use you will spend enough to use top of the line parts no matter what method you choose. Online, the best I could find was in this link:
http://www.naturalgas.org/overview/uses_eletrical
It has a micro-turbine generator available that is 80% efficient. (I don't know where that came from, the highest I had ever heard of was 70%)
As for the rest, we have never made any near a century life atomic batteries, and we have never tried to make a generator from this technology. It seems silly to argue about which would be better - at this point almost certaintly you would use an atomic battery, the other is not developed yet (R is done, D is not).
I'm just saying that working on this is a good idea!
The total mass issue is a problem only for small spacecraft (basically you are assuming that fuel is a low proportion of mass, I am assuming a high proportion). We are both right for different assumptions.
As for Carnot efficiency and such, I kept my post rather vague on that point intentionally. There are devices that achieve near carnot efficiency, and such devices tend to be low power as well. In your example you mention a steam generator - I think we both agree that it is unlikely that a steam generator would be launched. (However top of the line steam power plants are near 70% efficient, and so even that sort of goes against your point).
The breakeven point is dead on, but I never said the technology would work as is. I was really saying that the technology shows a lot of promise, even if it doesn't seem likely to provide high power levels (or even work at room temperature).
Your small nuclear generator design is interesting, but nuclear fuel tends not to last too well. Typically years, not decades.
Well, yes - but you could go further with this than an RTG (For the same mass, more energy available). It is true that the low temperatures would limit energy output, but one problem is keeping the spacecraft warm (well, near freezing actually). This could help with that, and provide a few watts of power. The radiator would be the spacecraft itself. Even at the fourth power, your spacecraft will be radiating on the order of 100 watts at 250-300 K. (Your example of 150 K is rather extreme - at that temperature you would get nearly 50% thermal efficiency - which means you would have to be ignoring other trade-offs)
Hey, want to help me build a rocket? All I need is a little cash...
To a certain extent, I think that they need to have work before they can complain about working conditions. That's what is missing in all this - the fact is that Indians that used to be in danger of starving to death trying to find a job are no longer in danger.
After the basic necessities of life are met, the masses will start complaining about working conditions. As long as people die from lack of food, no one will complain. So your actions, however nobly intended, probably have the wrong result...
Well, the term "cold fusion", if taken literally, can never be applied to any form of fusion we have imagined. On an atomic scale, the energy of a single atom is its "heat", and the 1 Mev or so required is extremely hot!
Personally, I think it is fair to call anything that has an average chamber temperature below 100 C "cold fusion", because it is cold enough to make apparatus design safe and easy.
Remember, cold is a relative term. Compared to a standard fusion reactor, the center of the sun is "cold".
That is such a moronic response! (Sorry, I really get sick of hearing things like that!)
What you mean is that you cannot think of an application. I can think of several, some of which would probably work almost as is. For example, it could be used to heat interstellar probes above 4 K - you have to take all your energy with you because interstellar space has no energy sources available. It works best in the cold - perfect for some applications.
Please, please do not assume that there are no applications just because you can't think of any!
Sorry, this just drives me nuts! I'll be quiet now...
The Saint did not explain exactly how the fusion was induced, so it may very well have been sonic.
Good way to go in a movie, by the way - leave the science vague. That way you don't sound as dumb...
What you say is true, but less true is deep space. Out beyond Jupiter or so, there is very little energy available. Everything is very low temperature, and radiation cooling very quickly gets you to extremely cold temperatures (40 K is reasonable, as I remember).
Something like this could work as a Mr. Fusion for deep space probes - it sounds like a perfect match. Deep Space probes typically don't even need that much power!
No, I said it right - they beat the theoretical maximum. (Of course, that just means that the theory doesn't account for everything, but even so no other engine has ever come close to that!)
The real problem is that in order to do that, they made an engine that really is not reusable. The engine has to be completely ripped down and refurbished between flights - thats why everything costs so much. The engine also is started via a magic process with hundreds of steps - so in orbit restart (or restart without hours of prep for that matter) are impossible.
The opposite is true of most of its predesesors. The RL-10 can be restarted as many times as necessary, and can run for hours with multiple restarts with no maintainence. (The X10 never had to do maintainence on its engines during the whole life of the program!)
Everyone now tries to make a shuttle engine copy - and they normally end up exploding (see Japan's J4 (I think)). Simple is good, people!
This is not really true, in order to change your orbit 90 degrees you need about 0.5 v change (or so, I forget the exact number).
Essentially, you first change the orbit from circular to extremely eliptical. Then you change directions when you are farthest from Earth. The you circularize the orbit. It works because the energy required to change directions is a lot less when you are at the extreme edge of an elliptic orbit, because you are so much slower.
While true, your car uses a safety factor of at least 10, and normally near 100...
It's even worse than this - all rocket development is done as a funded research project. Research projects that choose the easiest way to do something do not get funded! Research into hard things gets funded - so given the choice between making an existing rocket engine more reliable (easy) and making an existing rocket engine 0.0001% more efficient (hard), they choose efficiency.
By the way, the theoretical maximum efficiency of the space shuttle's engines is about 2% less than the actual - they obviously spent too much time on those engines...
Weirdly enough this is not true - you can build a compressive structure to Geo! It would be insanely expensive, but two things make it possible.
1. Using tension strength as compressive strength - you essentially use "balloons" sitting on top of each other, giving you a compressive strength equal to 1/2 tensile strength.
2. The taper works much better with a tower - most of the structure is at very near zero G, and so only needs to support the very thin low G structure above it. Conversely, a tension structure has to be thickest at the top.
To really understand the impact of #2, a compressive structure will have a HUGE base, but 500 km up will be a thin spike going the rest of the 30,000 km. A tension structure will be a thin thread for the first 500 km, and a thick structure for the rest of the 30,000 km.
Weird yes, but a compressive structure may be easier!
By the way, you are of course presuming that my definition of "me" matches your definition of "me" - which is apparently wrong. I believe I am essentially made up of the software, not the hardware - if you back up my conciousness and restore to a different body I will still consider that "me".
Even if it was a clone, and I was still alive - both "me"s would agree that we were both "me" and therefore had certain rights and obligations to each other.
But then, admittedly, I'm strange!
Yes, it went into that as well. The hero (well, one of them) had sent himself to his death many times for the good of mankind - it even had a little part where the doomed copy contemplated his coming demise as he saw destruction rushing towards him.
Rather interesting, really. Would you be willing to die for a cause, assuming all you would lose was the last few minutes? (Of course, most people have several causes they would die for even without that - family, friends, etc.)
Absolutely! Game theory doesn't endorse anything - it just tries to explain why certain structures exist, endure, and work (for various definitions of "work").
I read an interesting book where they continuously backed up their conciousness onto indestructible recorders, so the only thing that could really "kill" you was if you were driven insane (or in this book, had your conciousness hacked into and taken over)
A crazy lady once said, life without pain has no meaning...
Gentlemen, I am here to bring your life meaning!
...this wouldn't be slashdot without your pedantic comment at the end...
;-}
Yep, you've got to add in a zinger just to make it conversational!
Game theory covers a lot of ground, but in general when you are discussing socio-economic advantages, you are talking game theory. (Any time you want to know what the best decision for society would be, whenever you want to predict your competitor's move, etc.)
Interesting stuff, really. But I am not really an expert - I just make decisions, I don't pretend to understand them...
The answer is quite simple, really. Everyone is really better off when one person is in charge. In anarchy the wealth is evenly distributed, but the total wealth is far less because no one is willing to do anything. In a structured environment, wealth is created so even if the wealth is distributed unevenly everyone is better off. That is why the system works and is stable - everyone is better off, even the lowest members of society. (If you don't believe that, ask yourself why people don't just quit society and go live in the mountains - it is possible, at least in the US)
As for why the people at the top get more than an even distribution - its because it is hard to get to the top, and society is better off if it motivates people to reach the top. I know everyone says that CEOs are overpaid, etc. but good CEOs are extremely rare - and are therefore workth their weight in gold to society. If, as you seem to believe, it was an easy job then others would compete for the job and the board would tell the CEO "Hey, Joe here can do just as well as you, and he will work for peanuts!" The fact is, once you find a good CEO you don't let him go!
Of course, whining is much easier than studying the game theory that explains all this...
For the first part of your reply, I guess it just comes down to whom you trust more - charities or the government. My experiences led me one way, yours lead you another.
For the latter half, I was more thinking of welfare programs rather than social security. Right now, we have multiple programs - I think that getting rid of them could save a lot of money, and that very few people would stay at earning just $3/hr for very long. Most of our income taxes go towards funding welfare programs, which are really just another form of social security.
Your 0.4% is rather low for a retirement account (sound more like checking or easy-access savings). Normally, the longer you tie up the funds, the better the rate. Standard rates for totally secure investments are normally around 4%, or basically enough to just barely clear inflation. Open market bonds are 7-10%, and the stock market (such as index funds, which are relatively safe over a 40 year window) returns around 15%.
Some things to consider, however are these:
1. Inflation - most people use 3% in their planning.
2. Wages - As you start out, you will be making small bucks. If you save X% of your wages, in 5 years you will probably be making so much more that the amount saved previously doesn't really amount to much... at least that's what has happened to me.