I suspect you're absolutely correct. Killing your orbital velocity on rockets alone is almost as hard as getting there in the first place. In fact, if you take the weight of the Apollo heat shields and the amount of delta-v they provide during reentry, you find they get an Isp of around 7000s -- compared to numbers in the range of 260-450 for bipropellant rockets. Heat shields are so vastly superior for the problem that you'd be insane not to use them.
Your choices are rockets, parachutes, wings and landing gear, or a variety of weird and exotic options (like deploying helicopter blades; see the Roton concepts). There are a variety of reasons to prefer rockets to parachutes (and vice versa). The rockets are likely somewhat heavier than the parachutes and their deployment system, but I suspect the weight difference is small enough that the decision would likely be made on the basis of operational advantages (like being able to do a landing on solid ground instead of the ocean easily).
The American space program seems to be of the opinion that everything should be as light weight and efficient as possible, without regard to other criteria. The Russians, on the other hand, have a long history of being willing to build larger, heavier, less efficient rockets in order to make operations easier. Personally, I think the Russian approach is better -- the correct figure of merit to optimize is not liftoff weight, but cost. If you can develop, build, and/or operate more cheaply by spending more weight on the problem, that's a win in my book.
Hmm... To me, it sounded like they were trying to make a "solve my problem" wizard that actually solved problems with the computer. Because last I checked, there wasn't one of those. And if there was, and it actually worked... that would be really useful.
All a NIC can tell you is that the bits are getting through "well enough." It doesn't tell you anything about how much attenuation, noise, skew, reflection, etc your cable is producing. In general, if it works with no errors, you don't care about the other details. However, if you want to know how much margin you have (is it likely to stop working if I put this power cable nearby?), you need real test data that a NIC can't give you.
For my own use, I'm willing to track down the occasional weird cable fault and replace the cable. But if I was being paid to do it, I'd just buy the cable and not worry about it -- I get paid too much for any other choice to make sense.
Actually, you don't have to make it handle the full range. If you only handle the 30V-100V range, thanks to E=CV^2 you're not using the last 9% of the energy, meaning you get to use 91% of the capacity. More realistically, you could design your power electronics to provide full motor power at 30V, but keep working at reduced output power (they're mostly limited by max voltage and max current, so at 15V they can provide half the max power as at 30V). Then, when your car's battery gauge starts showing E, your car keeps running but you can't get as much acceleration from it.
Trading off peak acceleration in the bottom 9% capacity for cheaper and more efficient power electronics makes a great deal of sense to me. A 3:1 input voltage range is at the high end for normal DC-DC converters, but it's hardly unheard of. If there was a reason to, you could make it handle a wider range than that, but I suspect in practice a trade like this will be made.
(FYI: EEStor's capacitors actually run at a rather high voltage, like 3500V peak, but the issues stay exactly the same.)
You need more oxygen than it does. Really, an oxygen detector isn't that expensive. Neither is overkill ventilation. And for small experiments, you just ignore the problem -- at a kilogram per cubic meter (roughly), you'd have to boil off more than a liter of the stuff to cause a problem as long as you're not working in a well-sealed closet.
Suckered? Not particularly. I knew Obama wasn't perfect when I voted for him. I knew Hollywood and copyright issues in general was one where I wouldn't like him much. I also believed (and still do) the the other options weren't particularly better on this front. This really isn't a partisan issue, despite people on both the D and R sides of the aisle pretending it is.
Angry? Certainly. This is a bad policy (well, technically so far it only appears to foreshadow such). Copyright in our country is badly broken, and things that will make it worse make me angry, like many slashdotters.
Disappointed? Yes, somewhat. I had hoped things would be better than this. I didn't expect them to, and there was no rational basis for that hope. But if you stop hoping for a better future, then very quickly you'll stop working for it. And once you stop working for a better future, you're in deep trouble indeed. So I had hope that things will improve, and I was disappointed. I still have hope that things will improve.
Regretful? No. I don't want to be an Obama apologist: he's making a mistake here. Please, take him to task for it. Write angry letters, shout from the rooftops, and get us a decent copyright policy. I'm with you on that one. But please don't act like I was an idiot for voting for an imperfect candidate, or pretending that for some reason I have to either support or oppose everything he does as a single block. I'm capable of agreeing with him on some things and disagreeing on others, and I've basically gotten the candidate I thought I voted for, for better *and* for worse.
Actually, vanadium redox *can't* be improved to that point. Take the molecular weight of the relevant ions and the reaction potential, and that will give you how many electrons at how many volts a kilogram of the relevant chemicals can produce, which is just a units conversion away from joules or watt-hours per kg. Add even a modest allowance for stuff to dissolve those ions in and acidify the solution, and it doesn't stand up to LiIon for capacity.
However, capacity per kg isn't the only metric of interest -- cost and ease of refueling / recharging are both quite relevant. The lack of aging problems with the electrolyte is also useful. I suspect vanadium redox will never see widespread use outside of stationary load-leveling applications, but there's no guarantee of that.
The other major tech to watch, of course, is EEStor's capacitors. They claim energy densities similar to current LiIon tech with a number of improved capabilities, but last I heard still hadn't (publicly) demonstrated a working prototype.
Hawks notes that long-distance running is now extremely rare, and "where it exists, it is supported by very sophisticated cultural adaptations, including tracking, water storage and staged transport of meat back to home bases.
Often true, but not always. Both KDE and Gnome have substantial followings, and there are a number of less common but still far from obscure desktops as well (like XFCE, my personal choice). Even in the browser realm, Konqueror is rather far from dead. XFree86 was forked quite successfully after a variety of problems.
Certainly in general FOSS converges to a single program for large things, but I don't think that's always true. I couldn't begin to identify the dynamics that make that convergence occur or not occur.
Yes, it should. It makes the units work out nicely. Assuming we mean an iPod Classic in audio mode, conversion factors are 80mW / iPod and 250 Dollars / iPod. So at $2.35/W, this plant has a cost efficiency of about 0.00074 (lower is better; since both units are now iPods, we can cancel!).
Legal blindness refers to being unable to read the top letter on the chart *with corrective lenses*. That definition is a lot stricter than most people realize.
We don't know how to build a reference mass that is accurate to even 10 ppm over a century. You're asking for a mass that is accurate to (about) 0.05 ppm over 100 centuries if you want the clock to be accurate to a single day at the end of those 100 centuries. Furthermore, you want it to be built not from a high-stability noble metal alloy, but from a radioactive, reactive gas. And you want to maintain this stability without even doing the best job you know how of isolating it from its environment, but instead to have it communicate in a defined manner.
In short, I think radioactive decay is a problematic method of measuring time -- even for less chemically active isotopes and non-mass-based measurement techniques.
When it breaks, we fix it. Hopefully the only maintenance it needs before the 10,000 year mark is regular winding, but it's certainly possible it will need repair. Looking far into the future without the realization that things can go wrong is naive. Realizing that our plans won't work out exactly does not mean we shouldn't make them, and the law of unintended consequences does not mean we can avoid considering the consequences of our actions.
The weights descend over the course of a year, and then the clock needs to be wound. This is not a device meant to be left alone; it is supposed to last 10,000 years while being cared for.
Reading the amount of radioactivity in a sample to a precision of even 1 day in 3.6 million is nontrivial. Doing it with a device that will survive 3.6 million days while being exposed to said radiation is even more so.
Building a clock that lasts 3.6 million days is not a project for a single day, let alone the five minutes spent on a slashdot comment.
Perhaps if more people stopped to consider the future that far in advance, our odds would improve. And perhaps the mere existence of such a clock would encourage a few to do so.
That's why one of the design considerations is avoiding valuable materials. This is nontrivial -- materials with good corrosion and wear resistance tend to be pricey. Obviously the clock won't be made of anything as low value as stone, but it is a consideration.
Slashdot Mirror
No, it's to Pandemic (or its sequel, Pandemic 2, which is the better game).
I suspect you're absolutely correct. Killing your orbital velocity on rockets alone is almost as hard as getting there in the first place. In fact, if you take the weight of the Apollo heat shields and the amount of delta-v they provide during reentry, you find they get an Isp of around 7000s -- compared to numbers in the range of 260-450 for bipropellant rockets. Heat shields are so vastly superior for the problem that you'd be insane not to use them.
Your choices are rockets, parachutes, wings and landing gear, or a variety of weird and exotic options (like deploying helicopter blades; see the Roton concepts). There are a variety of reasons to prefer rockets to parachutes (and vice versa). The rockets are likely somewhat heavier than the parachutes and their deployment system, but I suspect the weight difference is small enough that the decision would likely be made on the basis of operational advantages (like being able to do a landing on solid ground instead of the ocean easily).
The American space program seems to be of the opinion that everything should be as light weight and efficient as possible, without regard to other criteria. The Russians, on the other hand, have a long history of being willing to build larger, heavier, less efficient rockets in order to make operations easier. Personally, I think the Russian approach is better -- the correct figure of merit to optimize is not liftoff weight, but cost. If you can develop, build, and/or operate more cheaply by spending more weight on the problem, that's a win in my book.
Hmm... To me, it sounded like they were trying to make a "solve my problem" wizard that actually solved problems with the computer. Because last I checked, there wasn't one of those. And if there was, and it actually worked... that would be really useful.
All a NIC can tell you is that the bits are getting through "well enough." It doesn't tell you anything about how much attenuation, noise, skew, reflection, etc your cable is producing. In general, if it works with no errors, you don't care about the other details. However, if you want to know how much margin you have (is it likely to stop working if I put this power cable nearby?), you need real test data that a NIC can't give you.
For my own use, I'm willing to track down the occasional weird cable fault and replace the cable. But if I was being paid to do it, I'd just buy the cable and not worry about it -- I get paid too much for any other choice to make sense.
Actually, you don't have to make it handle the full range. If you only handle the 30V-100V range, thanks to E=CV^2 you're not using the last 9% of the energy, meaning you get to use 91% of the capacity. More realistically, you could design your power electronics to provide full motor power at 30V, but keep working at reduced output power (they're mostly limited by max voltage and max current, so at 15V they can provide half the max power as at 30V). Then, when your car's battery gauge starts showing E, your car keeps running but you can't get as much acceleration from it.
Trading off peak acceleration in the bottom 9% capacity for cheaper and more efficient power electronics makes a great deal of sense to me. A 3:1 input voltage range is at the high end for normal DC-DC converters, but it's hardly unheard of. If there was a reason to, you could make it handle a wider range than that, but I suspect in practice a trade like this will be made.
(FYI: EEStor's capacitors actually run at a rather high voltage, like 3500V peak, but the issues stay exactly the same.)
You need more oxygen than it does. Really, an oxygen detector isn't that expensive. Neither is overkill ventilation. And for small experiments, you just ignore the problem -- at a kilogram per cubic meter (roughly), you'd have to boil off more than a liter of the stuff to cause a problem as long as you're not working in a well-sealed closet.
Suckered? Not particularly. I knew Obama wasn't perfect when I voted for him. I knew Hollywood and copyright issues in general was one where I wouldn't like him much. I also believed (and still do) the the other options weren't particularly better on this front. This really isn't a partisan issue, despite people on both the D and R sides of the aisle pretending it is.
Angry? Certainly. This is a bad policy (well, technically so far it only appears to foreshadow such). Copyright in our country is badly broken, and things that will make it worse make me angry, like many slashdotters.
Disappointed? Yes, somewhat. I had hoped things would be better than this. I didn't expect them to, and there was no rational basis for that hope. But if you stop hoping for a better future, then very quickly you'll stop working for it. And once you stop working for a better future, you're in deep trouble indeed. So I had hope that things will improve, and I was disappointed. I still have hope that things will improve.
Regretful? No. I don't want to be an Obama apologist: he's making a mistake here. Please, take him to task for it. Write angry letters, shout from the rooftops, and get us a decent copyright policy. I'm with you on that one. But please don't act like I was an idiot for voting for an imperfect candidate, or pretending that for some reason I have to either support or oppose everything he does as a single block. I'm capable of agreeing with him on some things and disagreeing on others, and I've basically gotten the candidate I thought I voted for, for better *and* for worse.
I rather suspect I'm not the only one.
Actually, vanadium redox *can't* be improved to that point. Take the molecular weight of the relevant ions and the reaction potential, and that will give you how many electrons at how many volts a kilogram of the relevant chemicals can produce, which is just a units conversion away from joules or watt-hours per kg. Add even a modest allowance for stuff to dissolve those ions in and acidify the solution, and it doesn't stand up to LiIon for capacity.
However, capacity per kg isn't the only metric of interest -- cost and ease of refueling / recharging are both quite relevant. The lack of aging problems with the electrolyte is also useful. I suspect vanadium redox will never see widespread use outside of stationary load-leveling applications, but there's no guarantee of that.
The other major tech to watch, of course, is EEStor's capacitors. They claim energy densities similar to current LiIon tech with a number of improved capabilities, but last I heard still hadn't (publicly) demonstrated a working prototype.
They've been doing that for some time. GigE uses a 5-level trellis code, and even 100Mb used 3 signaling levels.
From the link:
Hawks notes that long-distance running is now extremely rare, and "where it exists, it is supported by very sophisticated cultural adaptations, including tracking, water storage and staged transport of meat back to home bases.
Essentially, all models are wrong, but some are useful.
Often true, but not always. Both KDE and Gnome have substantial followings, and there are a number of less common but still far from obscure desktops as well (like XFCE, my personal choice). Even in the browser realm, Konqueror is rather far from dead. XFree86 was forked quite successfully after a variety of problems.
Certainly in general FOSS converges to a single program for large things, but I don't think that's always true. I couldn't begin to identify the dynamics that make that convergence occur or not occur.
Yes, it should. It makes the units work out nicely. Assuming we mean an iPod Classic in audio mode, conversion factors are 80mW / iPod and 250 Dollars / iPod. So at $2.35/W, this plant has a cost efficiency of about 0.00074 (lower is better; since both units are now iPods, we can cancel!).
Legal blindness refers to being unable to read the top letter on the chart *with corrective lenses*. That definition is a lot stricter than most people realize.
And here I thought I had enough trouble with misplacing the tape halfway through wrapping a normal-sized present.
No. Anathem was inspired by this. The Long Now Foundation has been working on this clock for quite some time.
The alloy nickels are made of is copper-nickel, a relative of Monel. True Monel is better, but nickels should last quite a while.
We don't know how to build a reference mass that is accurate to even 10 ppm over a century. You're asking for a mass that is accurate to (about) 0.05 ppm over 100 centuries if you want the clock to be accurate to a single day at the end of those 100 centuries. Furthermore, you want it to be built not from a high-stability noble metal alloy, but from a radioactive, reactive gas. And you want to maintain this stability without even doing the best job you know how of isolating it from its environment, but instead to have it communicate in a defined manner.
In short, I think radioactive decay is a problematic method of measuring time -- even for less chemically active isotopes and non-mass-based measurement techniques.
When it breaks, we fix it. Hopefully the only maintenance it needs before the 10,000 year mark is regular winding, but it's certainly possible it will need repair. Looking far into the future without the realization that things can go wrong is naive. Realizing that our plans won't work out exactly does not mean we shouldn't make them, and the law of unintended consequences does not mean we can avoid considering the consequences of our actions.
The weights descend over the course of a year, and then the clock needs to be wound. This is not a device meant to be left alone; it is supposed to last 10,000 years while being cared for.
Reading the amount of radioactivity in a sample to a precision of even 1 day in 3.6 million is nontrivial. Doing it with a device that will survive 3.6 million days while being exposed to said radiation is even more so.
Building a clock that lasts 3.6 million days is not a project for a single day, let alone the five minutes spent on a slashdot comment.
Perhaps if more people stopped to consider the future that far in advance, our odds would improve. And perhaps the mere existence of such a clock would encourage a few to do so.
That's why one of the design considerations is avoiding valuable materials. This is nontrivial -- materials with good corrosion and wear resistance tend to be pricey. Obviously the clock won't be made of anything as low value as stone, but it is a consideration.
You've never had a co-worker borrow a tool they didn't actually know how to use (but thought they did) and damage something?