Just because a fossil looks similar does not mean it hasn't evolved. Most evolution happens on the molecular scale, if you looked at the genomes I guarantee they would be different.
Videos are a worthless communication medium when the intent is the transfer propositional (rather than visual) information. I can't scan a video the way I can scan text, it's hard to pick out when questions are being asked without watching the entire thing, I can't control the rate of information dispersal, etc. etc.
There is no reason for this to be a video, or for it to be in two parts for that matter. Oh wait, there is, but only for your corporate overlords: money.
I agree. I want to read skim something in 15 seconds to see if I want to commit to reading in detail, not waste 10 minutes of my life on a video.
Why is NASA wasting our money and boosting russias economy instead of doing this which would save massive amounts of money that could be spent otherways and would boost our local US economy by having the money re-enter circulation here.
Because if the astronauts die everyone has a bad day
When a certain drug, whose active ingredients were asprin and something else, had its patents about to run out the maker "invented" a new durg that was the same except that the replaced asprin with aceteminophen. Patented that. and then withdrew the original from the market.
Aspirin is acetylsalicylic acid or 2-(acetyloxy)benzoic acid. Acetaminophen is N-(4-hydroxyphenyl)ethanamide. It's an entirely different chemical. They didn't "invent" a new drug - they actually did invent a new drug.
And as you note, the two have different effects. Acetaminophen can be particularly bad for livers in high doses.
And finally, your timeline is off. The patents on aspirin expired in 1917. Acetaminophen was released in 1956. Aspirin was widely available at that time, with many different manufacturers competing.
lol I have never seen a post dismantled like that... nice job!
Thermodynamics has nothing to do with photovoltaic.
There is no physical (as in laws of physic) limit that prevents a photovoltaic cell to be 100% efficient.
Why are americans so obsessed with 'laws of thermodynamic' and have no clue about them?
Read the article. It's not for photovoltaics, it's for thermophotovoltaics.
Actually, solar thermal uses heat engines to convert the heat into useful work.
The sun is like a black body (5800K). The absorber will also be a black body, but at a much lower temperature (probably ~1000K). The "absorber" will actually emit some IR light due its blackbody radiation. But not much. So effectively almost all of the energy will be absorbed, and a minimal amount re-radiated back into space. But the heat has to be converted into useful work. At that point, there is a relevant Carnot efficiency, which is what I spoke of.
Let me know if you have more basic physics questions!
limits the thermodynamic performance of heat engines to n=1-T_ambient/T_solar ~=1-293K/1000K=70%. Now there are going to be losses converting hot liquid into useful work (electrical energy), so actually probably around 30% efficiency will be achievable. High performance photovoltaics can reach 40% efficiency, and therefore this article is highly misleading.
If they generate so much heat that cooling them is critical, why dont they keep making power with it? Like pebble bed reactors or some type of thermal electric gen..?
Because it is much more difficult to extract useful work from low temperature waste heat than from high temperature waste heat. See the second law of thermodynamics for details (eg Carnot efficiency).
The low pressure environment in the tube should help since it would be 'repressurizing' the tube.
250kg of steam at 25 bars has a TNT equivalent of 25kg. That's a big boom! http://www.youtube.com/watch?v=GiSzi8bWozE I wouldn't want to be in the same tube as that when it goes off... hopefully the boiler system is designed properly.
Either way, seems like a technical obstacle to feasibility.
I'd say no, there are published standards for that type of pressure vessel. As for leaks thermal power stations often have "blowdown vessels" for when you want to dump everything out of a boiler really quickly.
there is no blast radius when you're in an enclosed tube...
OK, so this blow-down boiler has to be either at the back or the front... if it inbetween passenger cabins then it will kill everyone if you vent it. But yes, in theory you can store compressed steam. That's all fine and dandy until there is a rupture. Then you have a boiler that explodes inside of an enclosed tube with people in it, and can expand in one dimension. That is a much different disaster scenario than a boiler in a train that can expand into 3 dimensions. The "blast radius" is undefined in an enclosed tube.
It cools as it expands, and it's just water. It's easy to vent somewhere harmless.
Uhh...
250kg of steam at 550K will take up a huge volume, and thus a huge length of tube. In other words: you have to be careful to prevent it from entering the passenger cabin. Not impossible, but still requires some thought to prevent high pressure steam from entering the passenger cabin.
Its right there you the link. page 18. Water reservoir p = 101kPa, T =293K, m = 290kg. That is, a normal water tank under atmospheric pressure. Sucks if there is a leak though.
Yes, I am talking about page 18. You are referring to the water tank. After passing through the intercoolers, the steam is 557K (vapor phase). I am talking about the steam output. How do you store that? As high-pressure steam? If so, won't a leak kill everyone? If it's low pressure, won't the volume be enormous? Either way, seems like a technical obstacle to feasibility.
What steam storage? The article seemed to say that air would be forced through skis at the bottom of the pods by an air compressor and thrust would be provided by magnets.
What about the steam storage? Would it be under pressure? If so, isn't that dangerous in case of a leak? If not wouldn't the tanks need to be gigantic? Also, what about friction of air between the inlet and the nozzle expander?
Slashdot Mirror
Just because a fossil looks similar does not mean it hasn't evolved. Most evolution happens on the molecular scale, if you looked at the genomes I guarantee they would be different.
I would go nuts spending 2 hours doing a 10 mile trip each direction every day.
2 hours in a car for a bike trip that would take 1... sigh
Videos are a worthless communication medium when the intent is the transfer propositional (rather than visual) information. I can't scan a video the way I can scan text, it's hard to pick out when questions are being asked without watching the entire thing, I can't control the rate of information dispersal, etc. etc.
There is no reason for this to be a video, or for it to be in two parts for that matter. Oh wait, there is, but only for your corporate overlords: money.
I agree. I want to read skim something in 15 seconds to see if I want to commit to reading in detail, not waste 10 minutes of my life on a video.
Why is NASA wasting our money and boosting russias economy instead of doing this which would save massive amounts of money that could be spent otherways and would boost our local US economy by having the money re-enter circulation here.
Because if the astronauts die everyone has a bad day
When a certain drug, whose active ingredients were asprin and something else, had its patents about to run out the maker "invented" a new durg that was the same except that the replaced asprin with aceteminophen. Patented that. and then withdrew the original from the market.
Aspirin is acetylsalicylic acid or 2-(acetyloxy)benzoic acid. Acetaminophen is N-(4-hydroxyphenyl)ethanamide. It's an entirely different chemical. They didn't "invent" a new drug - they actually did invent a new drug.
And as you note, the two have different effects. Acetaminophen can be particularly bad for livers in high doses.
And finally, your timeline is off. The patents on aspirin expired in 1917. Acetaminophen was released in 1956. Aspirin was widely available at that time, with many different manufacturers competing.
lol I have never seen a post dismantled like that... nice job!
65,000 people in the dessert: it's a chocolate moose :D
Now that's a good time.
I was thinking that too. Is it a giant chocolate mousse? Or perhaps a big tub of jello?
Thermodynamics has nothing to do with photovoltaic. There is no physical (as in laws of physic) limit that prevents a photovoltaic cell to be 100% efficient.
Why are americans so obsessed with 'laws of thermodynamic' and have no clue about them?
Read the article. It's not for photovoltaics, it's for thermophotovoltaics.
Actually, solar thermal uses heat engines to convert the heat into useful work. The sun is like a black body (5800K). The absorber will also be a black body, but at a much lower temperature (probably ~1000K). The "absorber" will actually emit some IR light due its blackbody radiation. But not much. So effectively almost all of the energy will be absorbed, and a minimal amount re-radiated back into space. But the heat has to be converted into useful work. At that point, there is a relevant Carnot efficiency, which is what I spoke of. Let me know if you have more basic physics questions!
limits the thermodynamic performance of heat engines to n=1-T_ambient/T_solar ~=1-293K/1000K=70%. Now there are going to be losses converting hot liquid into useful work (electrical energy), so actually probably around 30% efficiency will be achievable. High performance photovoltaics can reach 40% efficiency, and therefore this article is highly misleading.
If they generate so much heat that cooling them is critical, why dont they keep making power with it? Like pebble bed reactors or some type of thermal electric gen..?
Because it is much more difficult to extract useful work from low temperature waste heat than from high temperature waste heat. See the second law of thermodynamics for details (eg Carnot efficiency).
You are welcome :)
I'm glad they don't have the great whites tagged here
The low pressure environment in the tube should help since it would be 'repressurizing' the tube.
250kg of steam at 25 bars has a TNT equivalent of 25kg. That's a big boom! http://www.youtube.com/watch?v=GiSzi8bWozE I wouldn't want to be in the same tube as that when it goes off... hopefully the boiler system is designed properly.
I'd say no, there are published standards for that type of pressure vessel. As for leaks thermal power stations often have "blowdown vessels" for when you want to dump everything out of a boiler really quickly.
there is no blast radius when you're in an enclosed tube...
Why would a steam leak kill everyone?
OK, so this blow-down boiler has to be either at the back or the front... if it inbetween passenger cabins then it will kill everyone if you vent it. But yes, in theory you can store compressed steam. That's all fine and dandy until there is a rupture. Then you have a boiler that explodes inside of an enclosed tube with people in it, and can expand in one dimension. That is a much different disaster scenario than a boiler in a train that can expand into 3 dimensions. The "blast radius" is undefined in an enclosed tube.
It cools as it expands, and it's just water. It's easy to vent somewhere harmless.
Uhh... 250kg of steam at 550K will take up a huge volume, and thus a huge length of tube. In other words: you have to be careful to prevent it from entering the passenger cabin. Not impossible, but still requires some thought to prevent high pressure steam from entering the passenger cabin.
Its right there you the link. page 18. Water reservoir p = 101kPa, T =293K, m = 290kg. That is, a normal water tank under atmospheric pressure. Sucks if there is a leak though.
Yes, I am talking about page 18. You are referring to the water tank. After passing through the intercoolers, the steam is 557K (vapor phase). I am talking about the steam output. How do you store that? As high-pressure steam? If so, won't a leak kill everyone? If it's low pressure, won't the volume be enormous? Either way, seems like a technical obstacle to feasibility.
What steam storage? The article seemed to say that air would be forced through skis at the bottom of the pods by an air compressor and thrust would be provided by magnets.
Oh there are more details here: http://www.spacex.com/sites/spacex/files/hyperloop_alpha-20130812.pdf There is steam storage
What about the steam storage? Would it be under pressure? If so, isn't that dangerous in case of a leak? If not wouldn't the tanks need to be gigantic? Also, what about friction of air between the inlet and the nozzle expander?
http://boblansdorp.blogspot.com/2012/10/microphone-and-speaker-based-sonar.html We used the speakers to make clicks, and the microphone to pick up the sound :)