I still refuse to belive JIT's have ever approached -O3 performance, but am willing to concede that a well written VM app can perform acceptibly.
I agree with you! But it is getting harder to show we are right. The other day I wrote the following code in c:
#include
int fib(int x) {
if (x == 1 || x == 2) return 1;
return (fib(x-1) + fib(x-2));
}
int main(int argc, char *argv[]) {
int x = 43;
int r;
r = fib(x);
printf("Fibonacci(%d) = %d\n", x, r);
}
I then ported it to Java, and found that it was actually FASTER in Java (for -O0, -O1, -O2, and -O3). I used Linux on x86 (C3) as well as Mac OS X on G4.
I know, I few years ago, Java would have been MUCH slower. I can imagine Java being as fast as C for such a simple example (if java starts to quickly complile to native), but how can it come out 10-20% faster?
Should I use my C-compiler better (using more than just an -ON flag)? Is Java doing something nasty that makes it faster (like implementing recursion in an imperative way)?
I do not beleive that Java replaces my inferior fibonacci implementation with its own fast one - in that case java would have been very fast.
Maybe its just me, but I think the USENIX letter would be more convincing if it in some way countered SCOs claim.
This letter is like: "Ohh, the world is such a nice place with OSS, and OSS itself it not illegal or wrong". That argument is not very good IF Linux in fact does not stand on legally acceptable ground and contains lots of SCO proprietary code.
I realise that USENIX does not know the answer, but they could at least have mentioned that there are reasons to believe that SCOs copyright claims are wrong.
I personally much prefer OSS, but I do not support piracy or theft.
Of course, SCOs letter to congress primarily dealt with the economic effects etc of OSS, thus it was natural for USENIX to do the same. But SCO repeatedly mentioned that SCO property is in Linux. USENIX should have said that they support Linux as long as it is legally acceptable, and that they belive it is (and SCO is full of shit).
Subsequent investigation has shown this was not the result of any breach of Microsoft's corporate network or internal security, nor is it related to Microsoft's Shared Source Initiative or its Government Security Program
First I want to make clear: I think in theory you are completely right (and my arguments make no real sense). What I wrote in my posts I have actually observed (and it kind of surprised me as well). I have not observed it thousands of times though, it could be an exception.
Just out of curiosity, you dont live in a socialistic country, do you?
In Sweden, the laws and regulations for employment are so complex (and very socialistic also) that most things that should be common sense in reality are just plain wrong.
Assume your implication is correct, and it is obvious that the virus writer must have been some Linux-warrior. Then it would make sense for anyone who wants to discredit Linux to write such a virus.
Thus, SCO, M$ or someone else who dislikes Linux could have written it.
I didnt mean "overqualified is as bad as underqualified" in general. But when considering a person (among many others) the employer does not necessarily choose the most qualified one - he might rather pick the one with exactly the right qualifications, for various reasons.
Also, I replied to someone saying that "If he does not get a job I will never get a job". It is not like everybody stands in a queue, and the smartest people stand first in that queue.
I do have an IT-related job in Sweden, and occationally we actually employ new people.
We (my company, I dont personally recruit people) are not looking for the most brilliant and ambitious people out there. We employ those who have exactly the right level of skills. Sounds strange, but when the times changes, if you have employed over-qualified people they will demand higher salaries, more interesting duties, and maybe they will leave nevertheless. Being overqualified is as bad as being underqualified.
Unfortunately, these days companies are not working with new cool upstart projects that they need smart entrepreneurs and geeks for - they rather work with streamlining their (organisational) processes, and maintanance.
Also, they dont want to really employ someone (if they do, they see it as a strategic decision). The rather hire a consultant or "Manpower"-guy. (This might primarily be true for Sweden).
I am not saying erasing merits from your CV will increase your chances, but the fact that someone else with more skills do not get a job does not automatically imply you wont.
Work experience is always valuable though (unless perhaps you are 55+).
www.pppl.gov/ncsx/Scientificconf/ 2000_01_21_TOKI/Toki.pdf...that might give you a hint.
(I was just googling on "stellarator design", try that, it will give you many matches).
But if you just want something world-related to play with, this mission is as follows (this will require some physics knowledge;)
The plasma consists of charged particles only. These particles are very hot. If the hit the wall of the reactor two bad things will happen:
1) the molecules in the wall will heat up and potentially leave the wall and go into the plasma. You definately do not want metal-ions in the plasma (as those generate extreme radiation when heated to plasma, they will chill the plasma and destroy it).
2) that part of the plasma, hitting the wall, will be lost.
Ions can be trapped within a magnetic field. Think about a pipe-like reactor with a homogenous magnetic field going parallell with the pipe. The plasma particles in the pipe can freely move from one end of the pipe to the other, but the magnetic field will stop the plasma from getting to the walls (the particles will move in small circles around the magnetic field lines). This was the ideal case - the particles close to the walls might actually get to the walls.
No plasma will hit the walls and we can have a nice encapsulated fusion going on.
Questions:
1) How do we produce such a magnetic field
2) What happens in the end of the pipe?
The answer to 1) is that you can put spools around the pipe generating a homogenous magnetic field in the pipes direction.
The answer to 2) is more tricky. The best thing anyone has come up with is "bend the pipe to a ring". Now comes a tricky physical implication (depending on your knowledge of physics). Bending the magnetic field to a ring will cause the magnetic "pressure" to be in-homogenous: stronger closer to the center of the ring (not the center of the pipe), and weaker far out from the center of the ring. Essentially this causes the plasma to "drift out" (and be destroyed in seconds).
In a tokamak you put a strong current in the plasma (the current parallell to the magnetic field). This current will cause a new magnetic field "twisting" the resulting magnetic field. So, a particle that finds itself far from the center of the reactor will follow its magnetic field line and after a while it will find itself close to the reactor center. Problem is - you cant sustain such a current for long time.
In a stellarator you design the spools to generate an inhomogenous twisting magnetic field in the first place. Then you need no current, and the reactor can burn for a long time:)
If you take a look on the pictures in the.pdf that I referenced, you get an impression of what it could look like.
The typical dimensions of a stellarator could be R=4m r=0.5m current in spools=30kA pressure inside reactor=1 Atmosphere temperature inside reactor=10-100 MK
Point is, there are many physical phenomenas that complicate things...
Solving the plasma behaviour in a fusion reactor is much like doing a weather-simulation. You want to contruct the reactor in a way that the wind blows the same all the time;) Ordinary weather does not have to wory about electrical currents, magnetic fields, etc etc
Taking a class or two in plasma physics should get you introduced;)
(I just studied a course in Fusion Physics with focus on environmental effects)
Basically fusion is not that hard. The problem in a fusion reactor is that the plasma cools off very quickly (seconds). If we let:
EO = energy outflow (cooling of plasma)
EF = energy produced by fusion reaction
EI = energy input (external heating)
then the following equations can be set up:
1) EO 0, the above equations 1 & 2 are hard to maintain. Why? Because hot plasma is cooled down by the reactor walls (+ other kinds of cooling).
Simply put, EO (cooling) is an area dependent function. EF (energy from fusion) is a volume dependent function. Thus, if you just build a large enough reactor, you can increase the EF/EO rating as much as you wish. However, a larger reactor costs more.
If we build a big reactor (r=20m) it would produce net energy output. It would NOT be commersially usable.
The ITER or Not-ITER discussion is about whether a large expensive test reactor would be worth its investment, or if the money rather should be used for base reasearch and computer simualtions.
There are two fundamentally different fusion reactors, the "tokamak", and the "stellarator" (IIRC). You want a magnetic field inside the reactor that keeps the plasma away from the walls. In the conseptually easier tokamak, that magnetic field is caused by letting a large (Mega Amp) current flow through the plasma. This current is produced in the plasma using the same concept as a AC voltage-transformer (the plasma is considered one of the spools). However, this means that the current in the "other" spool needs to increase linearly in order to maintain constant plasma current. In reality, this limits the time the reactor can operate to a few seconds (then you lose the plasma and need to restart).
A stellarator uses a very complex set of spools around the reactor to create constant magnetic field inside the reactor. "Very complex" means "not yet practically solved". Actually, its primarily a computational task.
How Ironic. The region codes where created to "make it possible to release a title on different occations". Now the core problem is that movies are in fact released on different occations in different parts of the world.
I was doing c/c++ development on the following platforms simultaneously:
- Mac OS X
- SGI Irix
- Solaris Sparc
- Linux x86
- Linux PPC
My experience was that you can get pretty much anything through the gcc x86 compiler and also run it successfully. When you move along to another platform you get Bus Error or Segmentation Faults all over the place, at runtime (the PPC is really picky).
Using different platforms simultaneously really helped improve code quality.
I usually code in linux/x86, but I do not consider my code tested and bugfree before it runs well on Mac OS X as well.
for example: Bush & CO is on the wrong track. Nuclear reactors should not be put in airplanes;)
Is it possible to "produce" hydrocarbons from CO2 and water in a good way (ie, efficiently and unexpensive)?
Solar power in the deserts could be used to produce significant amount of energy. The geothermical resources on Iceland are HUGE (2% of the easily available sources would produce enough energy for Sweden - problem is that a single DC cable from Iceland to Europe mainland costs more than the Iceland GNP). If they could produce gasoline...
Nuclear waste and radioactive pollution is bad, but it frightens me far less than resistant germs, climate change and genetically homogenous crops.
How many people have died from the Chernobyl catastrophy? Recently I heard that 1500 persons die every year in Sweden (population of 9M) from Ozone (created by combustion engines and trams). How many children die in Poland and Eastern Europe from pollution caused by coal power plants? How many people die in China due to coal-related polution. I do not know, but I think it is a safe guess to say that we could have a major nuclear catastrophy yearly and still be better of than we are with coal and oil.
In Sweden where I live the government has closed down a fully functional and state-of-the-art 800MW nuclear reactor, and instead we import nuclear power from Latvia (those plants are closer to our capital than the closed one, and approximately 1000 times more dangerous than ours) and coal power from Poland. There are people equally stupid to Bush over here, I promise you.
I too prefer the energy sources you mention, but I also prefer nuclear power to coal and oil.
In like 20 years the power production in China will increase by a factor of 5. Most of this will come from coal. It just remains to see if the poisonous effects will be unacceptable before the climates effects are.
And most interesting of all... will I be moderated offtopic this deep in a thread.
What you say is that travelling in a fully loaded big airliner costs about the same amount of energy (per mile per passenger) as travelling by car. (Could be a factor 2 or 5 in either direction depending on details, but whatever)
Can you suggest a less efficient way of transporting 450 persons from NY to SF, than each of them driving their own car?
Thus, from an energy point of view, flight is as inefficient as it gets. What makes it look descent is that it is a mass-transit. Try comparing it to travelling by high-speed train.
But of course I really appreciate that commersial flight is available for me whenever I want to get somewhere.
I know that burning hydrogen in the atmosphere is not good (it produces nitrogen gases, NO2, NO3, or whatever - I have not studied chemistry in english).
All cars today use a catalysator (hope that is the correct word in english) that takes care of NO2, NO3, SO2 etc. I suppose the same (or equivalent) technology could be used for a hydrogen engine - although that would not allow a jet engine (but a combustion engine can power an airplane as well).
Also, you can use a "fuel cell" that will produce only water and electricity - however I guess they are not really suitable for powering airplanes yet.
I definately agree with you - people fly when they need to travel far and fast. Being able to travel fast is one of the coolest thing with our society today. I live in Europe and have been in the US several times. I can get a return ticket for NY for maybe 400 dollars from Europe. Amazing.
Affordable flight is something we really want in the future. However, the environmental issues need to be addressed.
When it comes to flight generating water in the atmosphere, that is really beyond my knowledge. However, hydrogen gas contains more energy (per molecule and per mass) than kerosene, and both produce water when burned. My qualified guess is that less water is produced if you get the same amount of energy from burning hydrogen than from kerosene.
Hydrogen is the most potent energy-bearer available (per mass), nuclear power excluded. Hydrogen should only be considered an energy carrier, not an energy source.
What energy source will be used to produce hydrogen gas I do not know - but my guess and recommendation is some kind of nuclear reaction. Discussing environmental aspects of nuclear power is one of my favorites, but i find i fairly off-topic here;) Let me here if you want my opinion.
What you say is that if I take a flight from NY to SF in a full commercial airplane my share of the fuel consumption is about the same as if I had traveled the same distance alone in a modern car. This is probably quite correct - I have heard it before.
The point is, 200 persons driving in their own cars, coast to coast, is inefficient (compared to train or bus). Actually, it is as inefficient you can get it. To reach the same (in)efficiency for flight you need fully loaded planes.
Flight is a mass-transit and should be compared to other mass-transits.
If flight fuel were to be taxed in the same way we tax cars, no commercial airlines would exist.
What fuels are we supposed to use for civil flight in 50 years?
Today, the commersial airlines do not pay any environmental fees whatsoever on their fuel (correct me if I am wrong - I would like to be).
The energy cost for travel by flight is much higher than for other transport methods.
I guess that especially super/hyper-sonic flight will not be considered before the environmental issues (noise, not the least) are completely resolved.
In 50 years, I hope we have airplanes fueled by hydrogen produced in nuclear facilities.
Slashdot Mirror
Interesting point of view! That C is a tool for generating assembly code rather than a a tool only for building applications.
Keeping that in mind when thinking of Cs shortcomings (compared to perl, python, C# or Java) forgives a lot.
I agree with you! But it is getting harder to show we are right. The other day I wrote the following code in c:
#include
int fib(int x) {
if (x == 1 || x == 2) return 1;
return (fib(x-1) + fib(x-2));
}
int main(int argc, char *argv[]) {
int x = 43;
int r;
r = fib(x);
printf("Fibonacci(%d) = %d\n", x, r);
}
I then ported it to Java, and found that it was actually FASTER in Java (for -O0, -O1, -O2, and -O3). I used Linux on x86 (C3) as well as Mac OS X on G4.
longrow gt% time ./fib
Fibonacci(43) = 433494437
21.140u 0.010s 0:21.31 99.2% 0+0k 0+0io 0pf+0w
longrow gt% time java fib
Fibbonacci(43) = 433494437
18.370u 0.080s 0:18.79 98.1% 0+0k 0+14io 0pf+0w
I know, I few years ago, Java would have been MUCH slower. I can imagine Java being as fast as C for such a simple example (if java starts to quickly complile to native), but how can it come out 10-20% faster?
Should I use my C-compiler better (using more than just an -ON flag)? Is Java doing something nasty that makes it faster (like implementing recursion in an imperative way)? I do not beleive that Java replaces my inferior fibonacci implementation with its own fast one - in that case java would have been very fast.
For my needs and preferences, Java is "free enough". Anyone who ever has turned Java down in favor of something else, because it is not free?
The SCO share is now well below $13. It hasnt been this low since august.
Seems like time is running out for our friends in Utah.
Maybe its just me, but I think the USENIX letter would be more convincing if it in some way countered SCOs claim.
This letter is like: "Ohh, the world is such a nice place with OSS, and OSS itself it not illegal or wrong". That argument is not very good IF Linux in fact does not stand on legally acceptable ground and contains lots of SCO proprietary code.
I realise that USENIX does not know the answer, but they could at least have mentioned that there are reasons to believe that SCOs copyright claims are wrong.
I personally much prefer OSS, but I do not support piracy or theft.
Of course, SCOs letter to congress primarily dealt with the economic effects etc of OSS, thus it was natural for USENIX to do the same. But SCO repeatedly mentioned that SCO property is in Linux. USENIX should have said that they support Linux as long as it is legally acceptable, and that they belive it is (and SCO is full of shit).
How did it leak?
I think Compaq was bought by some printer manufacturer...
C: The language combining the power of assembly with the portability of assembler.
But thats not only dry, its also false.
First I want to make clear: I think in theory you are completely right (and my arguments make no real sense). What I wrote in my posts I have actually observed (and it kind of surprised me as well). I have not observed it thousands of times though, it could be an exception.
Just out of curiosity, you dont live in a socialistic country, do you?
In Sweden, the laws and regulations for employment are so complex (and very socialistic also) that most things that should be common sense in reality are just plain wrong.
Assume your implication is correct, and it is obvious that the virus writer must have been some Linux-warrior. Then it would make sense for anyone who wants to discredit Linux to write such a virus.
Thus, SCO, M$ or someone else who dislikes Linux could have written it.
I didnt mean "overqualified is as bad as underqualified" in general. But when considering a person (among many others) the employer does not necessarily choose the most qualified one - he might rather pick the one with exactly the right qualifications, for various reasons.
Also, I replied to someone saying that "If he does not get a job I will never get a job". It is not like everybody stands in a queue, and the smartest people stand first in that queue.
I do have an IT-related job in Sweden, and occationally we actually employ new people.
We (my company, I dont personally recruit people) are not looking for the most brilliant and ambitious people out there. We employ those who have exactly the right level of skills. Sounds strange, but when the times changes, if you have employed over-qualified people they will demand higher salaries, more interesting duties, and maybe they will leave nevertheless. Being overqualified is as bad as being underqualified.
Unfortunately, these days companies are not working with new cool upstart projects that they need smart entrepreneurs and geeks for - they rather work with streamlining their (organisational) processes, and maintanance.
Also, they dont want to really employ someone (if they do, they see it as a strategic decision). The rather hire a consultant or "Manpower"-guy. (This might primarily be true for Sweden).
I am not saying erasing merits from your CV will increase your chances, but the fact that someone else with more skills do not get a job does not automatically imply you wont.
Work experience is always valuable though (unless perhaps you are 55+).
#uname -a ...but I guess you are a troll...
Take a look at
...that might give you a hint.
;)
:)
.pdf that I referenced, you get an impression of what it could look like.
;) Ordinary weather does not have to wory about electrical currents, magnetic fields, etc etc
;)
www.pppl.gov/ncsx/Scientificconf/ 2000_01_21_TOKI/Toki.pdf
(I was just googling on "stellarator design", try that, it will give you many matches).
But if you just want something world-related to play with, this mission is as follows (this will require some physics knowledge
The plasma consists of charged particles only. These particles are very hot. If the hit the wall of the reactor two bad things will happen:
1) the molecules in the wall will heat up and potentially leave the wall and go into the plasma. You definately do not want metal-ions in the plasma (as those generate extreme radiation when heated to plasma, they will chill the plasma and destroy it).
2) that part of the plasma, hitting the wall, will be lost.
Ions can be trapped within a magnetic field. Think about a pipe-like reactor with a homogenous magnetic field going parallell with the pipe. The plasma particles in the pipe can freely move from one end of the pipe to the other, but the magnetic field will stop the plasma from getting to the walls (the particles will move in small circles around the magnetic field lines). This was the ideal case - the particles close to the walls might actually get to the walls.
So, consider a cross section of the reactor pipe:
Reactor wall | Vacuum | Plasma | Vacuum | Reactor Wall
No plasma will hit the walls and we can have a nice encapsulated fusion going on.
Questions:
1) How do we produce such a magnetic field
2) What happens in the end of the pipe?
The answer to 1) is that you can put spools around the pipe generating a homogenous magnetic field in the pipes direction.
The answer to 2) is more tricky. The best thing anyone has come up with is "bend the pipe to a ring". Now comes a tricky physical implication (depending on your knowledge of physics). Bending the magnetic field to a ring will cause the magnetic "pressure" to be in-homogenous: stronger closer to the center of the ring (not the center of the pipe), and weaker far out from the center of the ring. Essentially this causes the plasma to "drift out" (and be destroyed in seconds).
In a tokamak you put a strong current in the plasma (the current parallell to the magnetic field). This current will cause a new magnetic field "twisting" the resulting magnetic field. So, a particle that finds itself far from the center of the reactor will follow its magnetic field line and after a while it will find itself close to the reactor center. Problem is - you cant sustain such a current for long time.
In a stellarator you design the spools to generate an inhomogenous twisting magnetic field in the first place. Then you need no current, and the reactor can burn for a long time
If you take a look on the pictures in the
The typical dimensions of a stellarator could be
R=4m
r=0.5m
current in spools=30kA
pressure inside reactor=1 Atmosphere
temperature inside reactor=10-100 MK
Point is, there are many physical phenomenas that complicate things...
Solving the plasma behaviour in a fusion reactor is much like doing a weather-simulation. You want to contruct the reactor in a way that the wind blows the same all the time
Taking a class or two in plasma physics should get you introduced
(I just studied a course in Fusion Physics with focus on environmental effects)
1) EO < EF + EI
2) EO < EF
1) means that we have a net energy output (assuming 100% efficiency)
2) means that we have a "lit", self sustataining reactor
Basically fusion is not that hard. The problem in a fusion reactor is that the plasma cools off very quickly (seconds). If we let:
EO = energy outflow (cooling of plasma)
EF = energy produced by fusion reaction
EI = energy input (external heating)
then the following equations can be set up:
1) EO 0, the above equations 1 & 2 are hard to maintain. Why? Because hot plasma is cooled down by the reactor walls (+ other kinds of cooling).
Simply put, EO (cooling) is an area dependent function.
EF (energy from fusion) is a volume dependent function.
Thus, if you just build a large enough reactor, you can increase the EF/EO rating as much as you wish. However, a larger reactor costs more.
If we build a big reactor (r=20m) it would produce net energy output. It would NOT be commersially usable.
The ITER or Not-ITER discussion is about whether a large expensive test reactor would be worth its investment, or if the money rather should be used for base reasearch and computer simualtions.
There are two fundamentally different fusion reactors, the "tokamak", and the "stellarator" (IIRC). You want a magnetic field inside the reactor that keeps the plasma away from the walls. In the conseptually easier tokamak, that magnetic field is caused by letting a large (Mega Amp) current flow through the plasma. This current is produced in the plasma using the same concept as a AC voltage-transformer (the plasma is considered one of the spools). However, this means that the current in the "other" spool needs to increase linearly in order to maintain constant plasma current. In reality, this limits the time the reactor can operate to a few seconds (then you lose the plasma and need to restart).
A stellarator uses a very complex set of spools around the reactor to create constant magnetic field inside the reactor. "Very complex" means "not yet practically solved". Actually, its primarily a computational task.
How Ironic. The region codes where created to "make it possible to release a title on different occations". Now the core problem is that movies are in fact released on different occations in different parts of the world.
I was doing c/c++ development on the following platforms simultaneously:
- Mac OS X
- SGI Irix
- Solaris Sparc
- Linux x86
- Linux PPC
My experience was that you can get pretty much anything through the gcc x86 compiler and also run it successfully. When you move along to another platform you get Bus Error or Segmentation Faults all over the place, at runtime (the PPC is really picky).
Using different platforms simultaneously really helped improve code quality.
I usually code in linux/x86, but I do not consider my code tested and bugfree before it runs well on Mac OS X as well.
We agree on a lot of things ;)
;)
for example:
Bush & CO is on the wrong track.
Nuclear reactors should not be put in airplanes
Is it possible to "produce" hydrocarbons from CO2 and water in a good way (ie, efficiently and unexpensive)?
Solar power in the deserts could be used to produce significant amount of energy. The geothermical resources on Iceland are HUGE (2% of the easily available sources would produce enough energy for Sweden - problem is that a single DC cable from Iceland to Europe mainland costs more than the Iceland GNP). If they could produce gasoline...
Nuclear waste and radioactive pollution is bad, but it frightens me far less than resistant germs, climate change and genetically homogenous crops.
How many people have died from the Chernobyl catastrophy? Recently I heard that 1500 persons die every year in Sweden (population of 9M) from Ozone (created by combustion engines and trams). How many children die in Poland and Eastern Europe from pollution caused by coal power plants? How many people die in China due to coal-related polution. I do not know, but I think it is a safe guess to say that we could have a major nuclear catastrophy yearly and still be better of than we are with coal and oil.
In Sweden where I live the government has closed down a fully functional and state-of-the-art 800MW nuclear reactor, and instead we import nuclear power from Latvia (those plants are closer to our capital than the closed one, and approximately 1000 times more dangerous than ours) and coal power from Poland. There are people equally stupid to Bush over here, I promise you.
I too prefer the energy sources you mention, but I also prefer nuclear power to coal and oil.
In like 20 years the power production in China will increase by a factor of 5. Most of this will come from coal. It just remains to see if the poisonous effects will be unacceptable before the climates effects are.
And most interesting of all... will I be moderated offtopic this deep in a thread.
I guess you are right!
/ si vut/redofnox.html
http://www.mintc.fi/www/sivut/english/ymparisto
Thanks for informing me. Then we need to bring the oxygen with us as well...
What you say is that travelling in a fully loaded big airliner costs about the same amount of energy (per mile per passenger) as travelling by car. (Could be a factor 2 or 5 in either direction depending on details, but whatever)
Can you suggest a less efficient way of transporting 450 persons from NY to SF, than each of them driving their own car?
Thus, from an energy point of view, flight is as inefficient as it gets. What makes it look descent is that it is a mass-transit. Try comparing it to travelling by high-speed train.
But of course I really appreciate that commersial flight is available for me whenever I want to get somewhere.
I know that burning hydrogen in the atmosphere is not good (it produces nitrogen gases, NO2, NO3, or whatever - I have not studied chemistry in english).
All cars today use a catalysator (hope that is the correct word in english) that takes care of NO2, NO3, SO2 etc.
I suppose the same (or equivalent) technology could be used for a hydrogen engine - although that would not allow a jet engine (but a combustion engine can power an airplane as well).
Also, you can use a "fuel cell" that will produce only water and electricity - however I guess they are not really suitable for powering airplanes yet.
I said "In 50 years, I hope"...
I definately agree with you - people fly when they need to travel far and fast. Being able to travel fast is one of the coolest thing with our society today. I live in Europe and have been in the US several times. I can get a return ticket for NY for maybe 400 dollars from Europe. Amazing.
;) Let me here if you want my opinion.
Affordable flight is something we really want in the future. However, the environmental issues need to be addressed.
When it comes to flight generating water in the atmosphere, that is really beyond my knowledge. However, hydrogen gas contains more energy (per molecule and per mass) than kerosene, and both produce water when burned. My qualified guess is that less water is produced if you get the same amount of energy from burning hydrogen than from kerosene.
Hydrogen is the most potent energy-bearer available (per mass), nuclear power excluded. Hydrogen should only be considered an energy carrier, not an energy source.
What energy source will be used to produce hydrogen gas I do not know - but my guess and recommendation is some kind of nuclear reaction. Discussing environmental aspects of nuclear power is one of my favorites, but i find i fairly off-topic here
What you say is that if I take a flight from NY to SF in a full commercial airplane my share of the fuel consumption is about the same as if I had traveled the same distance alone in a modern car. This is probably quite correct - I have heard it before.
The point is, 200 persons driving in their own cars, coast to coast, is inefficient (compared to train or bus). Actually, it is as inefficient you can get it. To reach the same (in)efficiency for flight you need fully loaded planes.
Flight is a mass-transit and should be compared to other mass-transits.
If flight fuel were to be taxed in the same way we tax cars, no commercial airlines would exist.
What fuels are we supposed to use for civil flight in 50 years?
Today, the commersial airlines do not pay any environmental fees whatsoever on their fuel (correct me if I am wrong - I would like to be).
The energy cost for travel by flight is much higher than for other transport methods.
I guess that especially super/hyper-sonic flight will not be considered before the environmental issues (noise, not the least) are completely resolved.
In 50 years, I hope we have airplanes fueled by hydrogen produced in nuclear facilities.