I prefer the A380 to the 747, because I find the 747s hump ugly. However, the 747 blends its cockpit windows very smoothly with the shape of the nose, which the A380 doesn't. Also the A380 just looks too short for the height of its fuselage.
The A340 and 787 both look great, in my opinion. I haven't seen an A350 in the flesh yet, so can't comment on that.
The fundamental problem for the A380 is that twin jets are cheaper to operate than quad jets. The 777 may not carry as many passengers, but it has lower cost per passenger-kilometre than the A380, or indeed the 747 (which isn't so different in size than the 777.)
I have seen this stated many times. However, I don't really understand why. For example, this article states "those newer, more reliable [twin jet] engines have also been bigger and more efficient" but doesn't say why jet engine companies aren't also making more reliable and efficient engines for quad jets, if it is all down to newness.
I've looked online for an answer, but generally I just find speculation from people who seem no more knowledgeable than myself.
I can give an argument why quad jets should be cheaper. A plane needs to have sufficient thrust to take off and climb out after a single engine failure at the worst time (just after it is too late to abort take off.) If we call this thrust T, then a twin jet needs each engine to be capable of producing T, so it provides 2T thrust. For a quad jet, after a failure it needs T, so each of the remaining engines needs 1/3T, hence when fully operational it need only provide 4/3 T thrust. So a twin jet must be much more over provisioned than a quad.
Speculations I've seen include that four engines are extra complexity (but those big twin engines need a lot of extra complexity to be so big), extra maintenance costs, that engines disrupt lift, so you need bigger wings (and more weight) to make up the losses of having two extra engines, that with engines further outboard you need more structural strength in the wings (hence more cost and weight.)
I'm not saying these reasons are wrong, just that nobody I've seen making those arguments has convinced me they know what they're talking about. In replies, if you have expertise, or are citing someone with expertise, please make this clear.
I've met two ways of dealing with this. Mixed member proportional representation has some elected representatives tied to a specific electorate, and others are 'at large' and whose party affiliation makes the assembly's overall makeup proportional. Germany and New Zealand do this.
You can have each electorate elect multiple representatives, by some form of proportional representation. Canberra does this, having five electorates each electing five members.
There are bound to be other methods I haven't yet met.
Boundaries have to be somewhere, having close neighbours be in different districts isn't avoidable if you have cities too populous to fit in one district.
However your Google Maps example is pretty funny, and is a great example of lousy urban planning.
My plan (not that anyone listens to me): There is one primary for all candidates, of whatever affiliation. That primary selects about 3 to 5 candidates for the main election. In the main election, those 3 to 5 candidates are voted for by some form of preferential voting.
This would * Tend to elect moderates, whose political views are near the median of the electorate * Give a good chance to candidates with political positions which do not align with the two party orthodoxies (e.g. a fiscally conservative environmentalist, or an evangelical who favours more state support for health care of the poor.) * Keeps the advantages of preferential voting, but keeps the number of (post primary) candidates small enough for the electorate to understand the policies of all candidates
The primary system and partisan divide in US politics has expunged centrists from the legislatures, when it is those centrists who would do the best job, able to judge each issue on its merits rather than slavishly following extreme party lines.
From the CBC article: "The classified intelligence satellite, built by Northrop Grumman Corp, failed to separate from the second stage of the Falcon 9 rocket and is assumed to have broken up or plunged into the sea, said the two officials, who spoke on condition of anonymity."
This doesn't make sense. Stage 2 goes all the way to orbit (accepting SpaceX's assertion that Falcon worked entirely as planned). It only 'plunges into the sea' if they deliberately make a deorbit burn. (I assume that they do normally make a deorbit burn sometime after separation, to avoid making space junk, but launch coverage never talks about this part and at best only follows stage 2 up to payload separation, so I have no confirmation of this.) If the satellite failed to separate, they would delay the stage 2 deorbit burn while they tried to troubleshoot. If that failed, depending on the nature of the satellite, they might try to operate it with reduced capability while still attached to stage 2.
From here "...it is known that the Zuma payload was not processed in any of SpaceX’s payload processing facilities." This appears to imply that if there was a problem with separation, it is Northrop Grumman’s fault rather than SpaceX's.
I've seen in SpaceX launch coverage crowds of SpaceX employee spectators crowded around the glass walled SpaceX launch control room. I guess that for a classified launch that area would be out of bounds, to avoid uncleared people seeing satellite separation, so they must spectate from somewhere else for these missions.
That is what I was wondering. I'm betting the answer is "no". When you have very limited source material, and the correct translation of the source material is probably long lists of items like "3rd year, Nowhereville, 5 bushels wheat" I doubt this approach would get you anywhere.
In every case which I am aware of, (hieroglyphs, Linear B, Mayan) decypherment of ancient scripts required that a close relative of the script language was known to the decypherers. (If anyone has counter examples, I'd love to know about them.) If the language of the script is completely extinct, we may never be able to decypher it.
From GEMSA's cease and desist letter "... to write you in relation to the defamatory, false and malicious slander which you and Electronic Frontier Foundation made concerning our client..."
(In passing, I find it curious that they say "to write you" rather than "to write to you". Previously I've only seen the former construction from Americans, but this is an Australian law firm.)
I can think of two extra features you'd like your trailer to have with one of these: cameras which talk to the tractor, and regenerative breaking. Some sort of trailer camera standard would be great whether the tractor is electric or ICE. If you're towing a standard trailer, do you need extra airbrake hardware, or does the trailer contain all of that?
Assuming you can get it there and you can build a really good road for it, it should go way faster than 250 on Mars, as there is much less air resistance, which is the main limiting factor for speed. However you'll die at the first corner because it will have the same momentum but only 1/3 the gravitational downforce (and little opportunity to use aerodynamic downforce) so it would look like a fish, move like a fish, steer like a cow.
My criterion was world-dominant nations, and world domination tends to require expansion. I'm pacifist, so if you want to make a list of countries which achieved great influence without expansionism, I'd be happy to receive it.
20th C USA and 21st C China are (so far) not so much into expanding their borders, although they are into projecting military and economic power to influence other parts of the world to their advantage. (The non-expansionism is recent: 19th C USA was very much into expanding its borders, and 20th C China nabbed Tibet.)
I'm not sure I agree with your classification of Qin as non-expansionist.
The 20th century was dominated by the USA. The 19th century was dominated by the United Kingdom. It looks rather likely (as demonstrated by this story) that the 21st century will be dominated by China. Can we find other nice clean examples? I suggest: 16th century Spain (on the back of New World gold and silver)
Anything earlier than this is well short of global impact, due to lack of communications (particularly between the Americas and the rest of the world) 13th century Mongolia 8th century expansion of Islam 1st century BCE Rome 2nd century BCE Qin 3rd century BCE Macedonia
Until you start up the reactor, you just have uranium fuel (half life about 1 billion years), not lots of nasty highly radioactive stuff. If it fails on launch and the fuel is not contained you only have chemical heavy metal toxicity to worry about. I expect they can do a good job of containing the fuel in any case.
Once the reactor starts up, you are safely in orbit. The biggest danger would be on return from Mars to Earth orbit. You'd certainly want to design these things not to ever attempt reentry. It would take a lot going wrong to cause accidental reentry.
I'd want there to be a high quality risk assessment, but I think it wouldn't be hard to reduce the risk of atmospheric contamination to very low levels.
So if I happen to have a couple of charm or bottom Lambda bosons, I can do something clever to collide them and I can get energy. Alternatively, I could just wait about 10^-12 seconds until they decay of their own accord, and I can get energy.
It got past the Nature reviewers, so I suppose there must be some point, but I'm not seeing it.
I learned quite a bit about nucleosynthesis, but haven't revisited it in decades.
There are three main processes for synthesizing heavy elements. In the s-process (slow), neutrons are absorbed by heavy nuclei slowly enough that the nucleus has time to beta decay, if it is too neutron rich to be stable. The s-process happens in red giant stars, and the products can be released by stellar winds and planetary nebula formation.
In the r-process (rapid), neutrons are added very quickly to heavy nuclei, which absorb as many neutrons as they can and then, once the neutron bombardment ceases, beta decay back to stability. I don't recall whether we knew where the r-process happened when I was studying this, but this result would be r-process.
In the p-process (proton), nuclei grow by having protons added one at a time. This is presumed to happen in supernovae, and p-process nuclei are rare.
Isotopes coming from the s process will have abundances inversely proportional to their neutron cross section, because that cross section determines how quickly they move on. Also, while many isotopes can be produced by several of these processes, some can only be produced by one. My understanding is that these methods indicate that the s process is the predominant source of heavy elements. However this table (pointed out by other/. posters) contradicts my understanding, so possibly my knowledge has become outdated.
Can someone with more recent knowledge comment on how these new results can be reconciled with isotope abundances?
Battery chemistry is a hot topic and pretty much anything that shows promise is being researched by someone somewhere. Ni-Fe Ni-Zn and those results are just for 2016-2017, and I didn't search for synonyms "Nickel", "Iron", "Zinc", "cell" (instead of "battery".)
Slashdot Mirror
For planes of the same size, twins are cheaper than quads. 777s are driving out A380s and 747s, and the A340 died while the A330 lives on.
That was the 787
I prefer the A380 to the 747, because I find the 747s hump ugly. However, the 747 blends its cockpit windows very smoothly with the shape of the nose, which the A380 doesn't. Also the A380 just looks too short for the height of its fuselage.
The A340 and 787 both look great, in my opinion. I haven't seen an A350 in the flesh yet, so can't comment on that.
The fundamental problem for the A380 is that twin jets are cheaper to operate than quad jets. The 777 may not carry as many passengers, but it has lower cost per passenger-kilometre than the A380, or indeed the 747 (which isn't so different in size than the 777.)
I have seen this stated many times. However, I don't really understand why. For example, this article states "those newer, more reliable [twin jet] engines have also been bigger and more efficient" but doesn't say why jet engine companies aren't also making more reliable and efficient engines for quad jets, if it is all down to newness.
I've looked online for an answer, but generally I just find speculation from people who seem no more knowledgeable than myself.
I can give an argument why quad jets should be cheaper. A plane needs to have sufficient thrust to take off and climb out after a single engine failure at the worst time (just after it is too late to abort take off.) If we call this thrust T, then a twin jet needs each engine to be capable of producing T, so it provides 2T thrust. For a quad jet, after a failure it needs T, so each of the remaining engines needs 1/3T, hence when fully operational it need only provide 4/3 T thrust. So a twin jet must be much more over provisioned than a quad.
Speculations I've seen include that four engines are extra complexity (but those big twin engines need a lot of extra complexity to be so big), extra maintenance costs, that engines disrupt lift, so you need bigger wings (and more weight) to make up the losses of having two extra engines, that with engines further outboard you need more structural strength in the wings (hence more cost and weight.)
I'm not saying these reasons are wrong, just that nobody I've seen making those arguments has convinced me they know what they're talking about. In replies, if you have expertise, or are citing someone with expertise, please make this clear.
I've met two ways of dealing with this.
Mixed member proportional representation has some elected representatives tied to a specific electorate, and others are 'at large' and whose party affiliation makes the assembly's overall makeup proportional. Germany and New Zealand do this.
You can have each electorate elect multiple representatives, by some form of proportional representation. Canberra does this, having five electorates each electing five members.
There are bound to be other methods I haven't yet met.
Boundaries have to be somewhere, having close neighbours be in different districts isn't avoidable if you have cities too populous to fit in one district.
However your Google Maps example is pretty funny, and is a great example of lousy urban planning.
My plan (not that anyone listens to me):
There is one primary for all candidates, of whatever affiliation.
That primary selects about 3 to 5 candidates for the main election.
In the main election, those 3 to 5 candidates are voted for by some form of preferential voting.
This would
* Tend to elect moderates, whose political views are near the median of the electorate
* Give a good chance to candidates with political positions which do not align with the two party orthodoxies (e.g. a fiscally conservative environmentalist, or an evangelical who favours more state support for health care of the poor.)
* Keeps the advantages of preferential voting, but keeps the number of (post primary) candidates small enough for the electorate to understand the policies of all candidates
The primary system and partisan divide in US politics has expunged centrists from the legislatures, when it is those centrists who would do the best job, able to judge each issue on its merits rather than slavishly following extreme party lines.
From the CBC article:
"The classified intelligence satellite, built by Northrop Grumman Corp, failed to separate from the second stage of the Falcon 9 rocket and is assumed to have broken up or plunged into the sea, said the two officials, who spoke on condition of anonymity."
This doesn't make sense. Stage 2 goes all the way to orbit (accepting SpaceX's assertion that Falcon worked entirely as planned). It only 'plunges into the sea' if they deliberately make a deorbit burn. (I assume that they do normally make a deorbit burn sometime after separation, to avoid making space junk, but launch coverage never talks about this part and at best only follows stage 2 up to payload separation, so I have no confirmation of this.) If the satellite failed to separate, they would delay the stage 2 deorbit burn while they tried to troubleshoot. If that failed, depending on the nature of the satellite, they might try to operate it with reduced capability while still attached to stage 2.
From here
"...it is known that the Zuma payload was not processed in any of SpaceX’s payload processing facilities." This appears to imply that if there was a problem with separation, it is Northrop Grumman’s fault rather than SpaceX's.
I've seen in SpaceX launch coverage crowds of SpaceX employee spectators crowded around the glass walled SpaceX launch control room. I guess that for a classified launch that area would be out of bounds, to avoid uncleared people seeing satellite separation, so they must spectate from somewhere else for these missions.
I was wondering about "made up". This could be a fake story intended to get NK running around trying to make countermeasures to a non-existent threat.
Thank you
That is what I was wondering. I'm betting the answer is "no". When you have very limited source material, and the correct translation of the source material is probably long lists of items like "3rd year, Nowhereville, 5 bushels wheat" I doubt this approach would get you anywhere.
In every case which I am aware of, (hieroglyphs, Linear B, Mayan) decypherment of ancient scripts required that a close relative of the script language was known to the decypherers. (If anyone has counter examples, I'd love to know about them.) If the language of the script is completely extinct, we may never be able to decypher it.
(Obviously, there'd still be a cost for the vacuum or whatever is being used to change the pressure of the muscles.)
But if we use up all our vacuum on robot muscles, when future generations look for vacuum they'll find nothing! That would really suck!
From GEMSA's cease and desist letter "... to write you in relation to the defamatory, false and malicious slander which you and Electronic Frontier Foundation made concerning our client..."
There really can only be one response:
"I resent that! Slander is spoken. In print, it's libel."
(In passing, I find it curious that they say "to write you" rather than "to write to you". Previously I've only seen the former construction from Americans, but this is an Australian law firm.)
I can think of two extra features you'd like your trailer to have with one of these: cameras which talk to the tractor, and regenerative breaking. Some sort of trailer camera standard would be great whether the tractor is electric or ICE. If you're towing a standard trailer, do you need extra airbrake hardware, or does the trailer contain all of that?
Assuming you can get it there and you can build a really good road for it, it should go way faster than 250 on Mars, as there is much less air resistance, which is the main limiting factor for speed. However you'll die at the first corner because it will have the same momentum but only 1/3 the gravitational downforce (and little opportunity to use aerodynamic downforce) so it would look like a fish, move like a fish, steer like a cow.
My criterion was world-dominant nations, and world domination tends to require expansion. I'm pacifist, so if you want to make a list of countries which achieved great influence without expansionism, I'd be happy to receive it.
20th C USA and 21st C China are (so far) not so much into expanding their borders, although they are into projecting military and economic power to influence other parts of the world to their advantage. (The non-expansionism is recent: 19th C USA was very much into expanding its borders, and 20th C China nabbed Tibet.)
I'm not sure I agree with your classification of Qin as non-expansionist.
The 20th century was dominated by the USA. The 19th century was dominated by the United Kingdom. It looks rather likely (as demonstrated by this story) that the 21st century will be dominated by China. Can we find other nice clean examples?
I suggest:
16th century Spain (on the back of New World gold and silver)
Anything earlier than this is well short of global impact, due to lack of communications (particularly between the Americas and the rest of the world)
13th century Mongolia
8th century expansion of Islam
1st century BCE Rome
2nd century BCE Qin
3rd century BCE Macedonia
Until you start up the reactor, you just have uranium fuel (half life about 1 billion years), not lots of nasty highly radioactive stuff. If it fails on launch and the fuel is not contained you only have chemical heavy metal toxicity to worry about. I expect they can do a good job of containing the fuel in any case.
Once the reactor starts up, you are safely in orbit. The biggest danger would be on return from Mars to Earth orbit. You'd certainly want to design these things not to ever attempt reentry. It would take a lot going wrong to cause accidental reentry.
I'd want there to be a high quality risk assessment, but I think it wouldn't be hard to reduce the risk of atmospheric contamination to very low levels.
You don't have to use xenon for your ion drive.
They also said that nobody would adopt horses on steam powered pogo sticks as a method of transportation.
So if I happen to have a couple of charm or bottom Lambda bosons, I can do something clever to collide them and I can get energy. Alternatively, I could just wait about 10^-12 seconds until they decay of their own accord, and I can get energy.
It got past the Nature reviewers, so I suppose there must be some point, but I'm not seeing it.
I learned quite a bit about nucleosynthesis, but haven't revisited it in decades.
There are three main processes for synthesizing heavy elements. In the s-process (slow), neutrons are absorbed by heavy nuclei slowly enough that the nucleus has time to beta decay, if it is too neutron rich to be stable. The s-process happens in red giant stars, and the products can be released by stellar winds and planetary nebula formation.
In the r-process (rapid), neutrons are added very quickly to heavy nuclei, which absorb as many neutrons as they can and then, once the neutron bombardment ceases, beta decay back to stability. I don't recall whether we knew where the r-process happened when I was studying this, but this result would be r-process.
In the p-process (proton), nuclei grow by having protons added one at a time. This is presumed to happen in supernovae, and p-process nuclei are rare.
Isotopes coming from the s process will have abundances inversely proportional to their neutron cross section, because that cross section determines how quickly they move on. Also, while many isotopes can be produced by several of these processes, some can only be produced by one. My understanding is that these methods indicate that the s process is the predominant source of heavy elements. However this table (pointed out by other /. posters) contradicts my understanding, so possibly my knowledge has become outdated.
Can someone with more recent knowledge comment on how these new results can be reconciled with isotope abundances?
I thought "I don't believe that crash rate", so I looked it up.
An average of 102 car fatalities per day in USA in 2016.
I'm impressed.
Battery chemistry is a hot topic and pretty much anything that shows promise is being researched by someone somewhere.
Ni-Fe
Ni-Zn
and those results are just for 2016-2017, and I didn't search for synonyms "Nickel", "Iron", "Zinc", "cell" (instead of "battery".)
Somehow I missed knowing that we could do this. It is amazingly cool, and is absolutely a Nobel level advance.