Not quite the same as divers. AIUI, cognitive impairment while diving is a result of nitrogen narcosis (at extreme depths I believe helium behaves similarly). Cognitive impairment at altitude is from oxygen deprivation. Results are similar, but the mechanism is different. They share the common feature that it's very difficult to notice until your abilities return.
Yes, rather a lot like the Saturn V. Possibly that large, possibly not, depending on the mission details. Or maybe like the Falcon 1 / Falcon 9...
Note that if you use a technology that's not so expensive and is actually reliable, a lot of the motivation for distinct cargo and crew vehicles goes away.
As YAAE, I think it looks silly for several reasons. The first and most important one: you can't actually test fire the engine you're going to trust your life to! You can inspect it, and you can test the process, but you can't test the actual article. Furthermore, the propellant grain is susceptible to handling damage and manufacturing defects, so there is reason to want to test it. There are cases where solids in proximity to humans are reasonable -- small solid motors for ballistic parachutes, for example. Or signal flares. In those cases, you can reasonably test two or three orders of magnitude more devices than will be tested for Ares (mostly because they're smaller). The other cases where solids are better is where readily storable propellants are required, like for most missiles. That doesn't apply here. (There are plenty of other reasons as well, but I won't bother going into them.)
The mistake that leads to thinking solids are a good choice is comparing them to the SSME and other engines like it as if that was the only alternative. It's not. The best design to compare it to is probably LOX/Kerosene running at a modest chamber pressure, with a pump feed (gas generator cycle) where the pump and its drive system are heavier than they could be, but simpler in design and with more margin (and hence more reliable and cheaper). It doesn't need to be a turbopump -- piston machinery works too. For a large system, though, the turbopump is probably enough lighter to be better, but it should really have more resemblance to industrial turbomachinery than conventional rocket machinery. Yes, that won't hit the maximum possible Isp or mass ratio for the stage. But that isn't as important on a first stage (or really, anywhere you'd consider using a large solid -- even the low-performance LOX/Kero rocket will beat the solid). What is important are things like design cost, manufacturing cost, and reliability.
If you need a convenient size, that's what the prefixes are for. A MJ is as conveniently sized as a kWhr. Whr is more convenient in some applications for calculating energy used over time, so it's a reasonable thing to use there.
Miles per gallon is a silly set of units to use. Metric units would be nice, but have little practical benefit for most usage cases (unless we were to switch to selling liters of gas and marking roads in km, but that's unlikely). The problem is that miles per gallon is backward. It should be gallons per mile (or 100 miles something similar for convenient scale). Why? Distance is the independent variable, not the dependent one. You might want to know how many gallons you'll use on a 200 mile trip, but it's unlikely you want to know how far a trip you can go on with the 8 gallons left in your tank. Furthermore, it's not convenient for comparing operating costs either. You drive your car a certain number of miles per month, not a certain number of gallons. If I want to compare three cars that get 20, 30, and 40 mpg, the cost savings between the first two is bigger than between the last two -- despite the same change in the number. Basically, every time you use mpg, you have to do a division -- not the hallmark of a convenient unit.
The FSF does not need to pursue such damages. Given that their goal is to make a point while not scaring away potential FOSS users, I would imagine they would seek damages that were neither trivial nor crippling. Damages appropriate to what Cisco actually did, unlike evil record companies and their ilk.
If there is a question near the top that is like yours, you're more likely to see it and not submit a duplicate. If all the duplicates of your question are already modded to oblivion, and you don't see them, you're more likely to submit it because you think it hasn't been asked and needs to be. I would therefore expect a disproportionate number of nutjob questions -- and that therefore the number of questions on a subject should not be taken as an indication about the relative numbers of people interested. Besides, that's what the votes are for...
But stop and think how stupid the average person is, and then realize half of them are stupider than that.
I'm not sure which is worse: the stupid people who are completely ignorant, or the smart people who think they know it all and act, unknowingly, half-cocked at best.
Well, given that average person thinks they're above average, why can't we have both?
No, that doesn't place the files under the GPL. The only way something can become GPLed is if the copyright owner willfully uses the license. It may, however, mean that those works are derived works and cannot be distributed under an incompatible license without violating Cisco's obligations under the GPL. If that is the case, Cisco would need to cease distribution of the files in question (or fix the licensing problem, by applying a compatible license).
But make no mistake: Cisco will not be obligated to release anything under the GPL. They always have the option to simply cease distribution of the works in question entirely. Which one is easier for them may be in question, but that's entirely their decision.
At some point, we have to conclude that we are good. Gasoline is likely the best energy source for cars, and will continue to stay that way. Other sources have been tried (electricity was the first) but gasoline took precedence because it was cheap and efficient, and I don't see any reason to change that.
C should, in many ways, be thought of as a somewhat easier to read and portable assembly language. It doesn't hide much of anything from you, for better or for worse. Given the number of students who seem to manage to get rather far in their computing career without actually understanding what a pointer is, teaching a very low-level language first or very early has its merits.
That said, my personal choice would be either a functional programming language or a carefully chosen assembly language -- probably MIPS on an embedded processor. I'd prefer C to things like C++ or Java, though.
Now, I happen to agree that these networks should remain separate, with the best barriers between them we can manage
So don't call me naive/disingenuous;) We agree for Pete's sake!
The same reasons that make it useful to move data back and forth make it useful to do so in a low-latency and automated fashion. Which makes it useful to connect them to a network... "No reason" is not an accurate description of the situation.
It seems my choice of words was unfortunate; I seem to have neglected the possibility of unfortunate word choice. My apologies.
There is no reason to have that kind of equipment connected to a public network. Period.
People say that all the time, but it's simply not true. Coordinating a variety of utilities and their major consumers makes sense. Having the wind farm aware of the local weather predictions, the hydro plant aware of the seasonal rainfall expectations, and the nearby aluminum refinery aware of both of their likely outputs has real value. Your options are then to either build some alternate network and then move data on and off it in some kludgey fashion that isn't 100% secure (there's no rule that says you can't hide a buffer overflow in the weather report that's about to be delivered via USB drive...), or to acknowledge the value and cost of connecting it all to the Internet and accept both the risks and rewards.
Now, I happen to agree that these networks should remain separate, with the best barriers between them we can manage. I think the risks outweigh the rewards, and not by a trivial amount. But pretending the rewards are nonexistent is either naive or disingenuous.
If you're going to talk about nuclear engines, there are far more interesting ones. The nuclear salt-water rocket is particularly impressive -- Zubrin's original reference design had liftoff thrust on par with a Saturn V (it doesn't scale to far below that). And forget SSTO performance; it had the delta V for a single-stage Jupiter mission. Both ways. Of course, it too has the radioactive exhaust problem. Fortunately, the Isp is high enough that the exhaust exceeds solar escape velocity. As long as you don't aim it at a planet, there's no problem.
But, all the truly high performance nuclear designs require a launch from LEO or higher -- the NSWR, Orion, GCNR, Fission-fragment rockets. For now, I think the most likely solution for surface to LEO is chemical rockets. It might eventually be a space elevator, but I would be shocked if that occurred within even 50 years. (Give me space-elevator class building materials, and I'll give you a low-maintenance pressure-fed SSTO with reasonable payload.)
The only meaningful energy efficiency definition for this comparison is to compare the amount of energy you start with in the form of propellant or electricity to the amount that ends up in the payload. Otherwise the comparison is rather meaningless.
While the payload ends up with the same energy, in the case of the elevator a substantial portion of that energy came from the Earth's rotation, not the electricity you use to power the car. Specifically, the whole 3km/s orbital velocity. That orbital energy is still small compared to the energy to climb the gravity well, but it's a noticeable help to the elevator's overall efficiency. If you want a high-speed escape trajectory, you can pass 100% efficiency referenced to the electrical supply, even with less than ideal motors. (Obviously not if you count the Earth's rotational energy, but that's free (or at least properly accounted in the capital cost of the elevator)).
For the near and medium term, I'm not at all convinced that the energy savings from the space elevator matter. I've seen no evidence that they're easier to build and operate than rockets; until the energy cost of either is a noticeable fraction of the total cost, it doesn't really matter.
Of course, I suppose I'm biased, considering I'm a rocket engineer...
The Coriolis force in question accounts for all the sideways delta-v the payload receives -- about 2.5 km/s. Given a good rocket, you'd be spending half your elevator car mass on rocket propellant (Isp = 350s, ie a vacuum optimized nozzle burning LOX/Methane or similar). The elevator is much more interesting if you can make use of that Coriolis force.
The catapult is not even remotely the same as a launch loop. In the case of the catapult, all the energy is delivered from the power supply to the payload at once, and over a very short distance. A launch loop uses its power supply to maintain a loop of masses flying from one end to the other, and adds only minimal energy to each one on each pass. The payload then couples into this giant flywheel. This spreads the load on the power supply out, and also lets the payload take a *much* longer time to accelerate. Try launching a person to orbital velocity in a cannon. The launch loop also solves the problem of how to build something that long and that high, without magical materials.
In short, the only real relationship between the two is that they both use a linear electric motor. The closes relative to a launch loop is probably a Space Fountain. For that one, look to Robert L. Forward instead of Heinlein.
Earth's gravity is substantially weaker at GSO. GSO altitude is large compared to the Earth's radius.
Space elevators *do* lower the energy that is supplied by the launch system.In a space elevator, the energy for the sideways motion comes from the rotation of the Earth (hence the Coriolis forces on the elevator mentioned in the summary). For GSO, that's less than the energy spent climbing up the gravity well, but it's still not trivial.
For escape trajectories, the elevator looks even more attractive -- once you pass GSO, the ride becomes free, and you gain energy from the dynamics of the system without spending any propellant / electricity / whatever. Time it carefully, and you just "fall" off the end of the cable on the right trajectory.
All of that said, rockets aren't *that* inefficient. For LEO, they can be 10% efficient or better (slightly worse for GSO). That's not great, but there are no proposed methods of getting energy to the elevator car that are all that efficient either, especially when you count electricity generation losses. Given the disparity in capital costs, and the fact that in neither case is the energy cost a noticeable fraction of the budget, I suspect rockets will win out for some time to come...
My google-fu is apparently weak today. I'm having trouble coming up with sources on the matter that aren't obviously biased one way or the other. The ones that seem to give the question a fair treatment tend to put the addictiveness of the two drugs at similar levels. The NY Times article is fairly comprehensive; despite the headline claim that nicotine is more addictive, the body of the article suggests that the two are fairly comparable. Exactly what constitutes "more addictive" is so hard to pin down (and so variable person to person) that a definitive answer seems unlikely and not very meaningful; suffice it to say, the two are comparable.
Slashdot Mirror
Not quite the same as divers. AIUI, cognitive impairment while diving is a result of nitrogen narcosis (at extreme depths I believe helium behaves similarly). Cognitive impairment at altitude is from oxygen deprivation. Results are similar, but the mechanism is different. They share the common feature that it's very difficult to notice until your abilities return.
Yes, rather a lot like the Saturn V. Possibly that large, possibly not, depending on the mission details. Or maybe like the Falcon 1 / Falcon 9...
Note that if you use a technology that's not so expensive and is actually reliable, a lot of the motivation for distinct cargo and crew vehicles goes away.
As YAAE, I think it looks silly for several reasons. The first and most important one: you can't actually test fire the engine you're going to trust your life to! You can inspect it, and you can test the process, but you can't test the actual article. Furthermore, the propellant grain is susceptible to handling damage and manufacturing defects, so there is reason to want to test it. There are cases where solids in proximity to humans are reasonable -- small solid motors for ballistic parachutes, for example. Or signal flares. In those cases, you can reasonably test two or three orders of magnitude more devices than will be tested for Ares (mostly because they're smaller). The other cases where solids are better is where readily storable propellants are required, like for most missiles. That doesn't apply here. (There are plenty of other reasons as well, but I won't bother going into them.)
The mistake that leads to thinking solids are a good choice is comparing them to the SSME and other engines like it as if that was the only alternative. It's not. The best design to compare it to is probably LOX/Kerosene running at a modest chamber pressure, with a pump feed (gas generator cycle) where the pump and its drive system are heavier than they could be, but simpler in design and with more margin (and hence more reliable and cheaper). It doesn't need to be a turbopump -- piston machinery works too. For a large system, though, the turbopump is probably enough lighter to be better, but it should really have more resemblance to industrial turbomachinery than conventional rocket machinery. Yes, that won't hit the maximum possible Isp or mass ratio for the stage. But that isn't as important on a first stage (or really, anywhere you'd consider using a large solid -- even the low-performance LOX/Kero rocket will beat the solid). What is important are things like design cost, manufacturing cost, and reliability.
Yep, everyone else has it right. I found it a little odd when driving in Europe, simply because it was unfamiliar, but even so the math was easier.
If you need a convenient size, that's what the prefixes are for. A MJ is as conveniently sized as a kWhr. Whr is more convenient in some applications for calculating energy used over time, so it's a reasonable thing to use there.
Miles per gallon is a silly set of units to use. Metric units would be nice, but have little practical benefit for most usage cases (unless we were to switch to selling liters of gas and marking roads in km, but that's unlikely). The problem is that miles per gallon is backward. It should be gallons per mile (or 100 miles something similar for convenient scale). Why? Distance is the independent variable, not the dependent one. You might want to know how many gallons you'll use on a 200 mile trip, but it's unlikely you want to know how far a trip you can go on with the 8 gallons left in your tank. Furthermore, it's not convenient for comparing operating costs either. You drive your car a certain number of miles per month, not a certain number of gallons. If I want to compare three cars that get 20, 30, and 40 mpg, the cost savings between the first two is bigger than between the last two -- despite the same change in the number. Basically, every time you use mpg, you have to do a division -- not the hallmark of a convenient unit.
It works with neurofeedback, so I suspect so. Whether it created stable or unstable feedback is another question.
They made me take it off before getting in the MRI machine.
The FSF does not need to pursue such damages. Given that their goal is to make a point while not scaring away potential FOSS users, I would imagine they would seek damages that were neither trivial nor crippling. Damages appropriate to what Cisco actually did, unlike evil record companies and their ilk.
That's rather precisely the point I was trying to make in reply to the OP.
If there is a question near the top that is like yours, you're more likely to see it and not submit a duplicate. If all the duplicates of your question are already modded to oblivion, and you don't see them, you're more likely to submit it because you think it hasn't been asked and needs to be. I would therefore expect a disproportionate number of nutjob questions -- and that therefore the number of questions on a subject should not be taken as an indication about the relative numbers of people interested. Besides, that's what the votes are for...
But stop and think how stupid the average person is, and then realize half of them are stupider than that.
I'm not sure which is worse: the stupid people who are completely ignorant, or the smart people who think they know it all and act, unknowingly, half-cocked at best.
Well, given that average person thinks they're above average, why can't we have both?
No, that doesn't place the files under the GPL. The only way something can become GPLed is if the copyright owner willfully uses the license. It may, however, mean that those works are derived works and cannot be distributed under an incompatible license without violating Cisco's obligations under the GPL. If that is the case, Cisco would need to cease distribution of the files in question (or fix the licensing problem, by applying a compatible license).
But make no mistake: Cisco will not be obligated to release anything under the GPL. They always have the option to simply cease distribution of the works in question entirely. Which one is easier for them may be in question, but that's entirely their decision.
Or the 3255 number is a count of users, not all of whom have submitted questions.
At some point, we have to conclude that we are good. Gasoline is likely the best energy source for cars, and will continue to stay that way. Other sources have been tried (electricity was the first) but gasoline took precedence because it was cheap and efficient, and I don't see any reason to change that.
C should, in many ways, be thought of as a somewhat easier to read and portable assembly language. It doesn't hide much of anything from you, for better or for worse. Given the number of students who seem to manage to get rather far in their computing career without actually understanding what a pointer is, teaching a very low-level language first or very early has its merits.
That said, my personal choice would be either a functional programming language or a carefully chosen assembly language -- probably MIPS on an embedded processor. I'd prefer C to things like C++ or Java, though.
What's wrong with Malbolge?
Now, I happen to agree that these networks should remain separate, with the best barriers between them we can manage
So don't call me naive/disingenuous ;) We agree for Pete's sake!
The same reasons that make it useful to move data back and forth make it useful to do so in a low-latency and automated fashion. Which makes it useful to connect them to a network... "No reason" is not an accurate description of the situation.
It seems my choice of words was unfortunate; I seem to have neglected the possibility of unfortunate word choice. My apologies.
There is no reason to have that kind of equipment connected to a public network. Period.
People say that all the time, but it's simply not true. Coordinating a variety of utilities and their major consumers makes sense. Having the wind farm aware of the local weather predictions, the hydro plant aware of the seasonal rainfall expectations, and the nearby aluminum refinery aware of both of their likely outputs has real value. Your options are then to either build some alternate network and then move data on and off it in some kludgey fashion that isn't 100% secure (there's no rule that says you can't hide a buffer overflow in the weather report that's about to be delivered via USB drive...), or to acknowledge the value and cost of connecting it all to the Internet and accept both the risks and rewards.
Now, I happen to agree that these networks should remain separate, with the best barriers between them we can manage. I think the risks outweigh the rewards, and not by a trivial amount. But pretending the rewards are nonexistent is either naive or disingenuous.
If you're going to talk about nuclear engines, there are far more interesting ones. The nuclear salt-water rocket is particularly impressive -- Zubrin's original reference design had liftoff thrust on par with a Saturn V (it doesn't scale to far below that). And forget SSTO performance; it had the delta V for a single-stage Jupiter mission. Both ways. Of course, it too has the radioactive exhaust problem. Fortunately, the Isp is high enough that the exhaust exceeds solar escape velocity. As long as you don't aim it at a planet, there's no problem.
But, all the truly high performance nuclear designs require a launch from LEO or higher -- the NSWR, Orion, GCNR, Fission-fragment rockets. For now, I think the most likely solution for surface to LEO is chemical rockets. It might eventually be a space elevator, but I would be shocked if that occurred within even 50 years. (Give me space-elevator class building materials, and I'll give you a low-maintenance pressure-fed SSTO with reasonable payload.)
The only meaningful energy efficiency definition for this comparison is to compare the amount of energy you start with in the form of propellant or electricity to the amount that ends up in the payload. Otherwise the comparison is rather meaningless.
While the payload ends up with the same energy, in the case of the elevator a substantial portion of that energy came from the Earth's rotation, not the electricity you use to power the car. Specifically, the whole 3km/s orbital velocity. That orbital energy is still small compared to the energy to climb the gravity well, but it's a noticeable help to the elevator's overall efficiency. If you want a high-speed escape trajectory, you can pass 100% efficiency referenced to the electrical supply, even with less than ideal motors. (Obviously not if you count the Earth's rotational energy, but that's free (or at least properly accounted in the capital cost of the elevator)).
For the near and medium term, I'm not at all convinced that the energy savings from the space elevator matter. I've seen no evidence that they're easier to build and operate than rockets; until the energy cost of either is a noticeable fraction of the total cost, it doesn't really matter.
Of course, I suppose I'm biased, considering I'm a rocket engineer...
The Coriolis force in question accounts for all the sideways delta-v the payload receives -- about 2.5 km/s. Given a good rocket, you'd be spending half your elevator car mass on rocket propellant (Isp = 350s, ie a vacuum optimized nozzle burning LOX/Methane or similar). The elevator is much more interesting if you can make use of that Coriolis force.
The catapult is not even remotely the same as a launch loop. In the case of the catapult, all the energy is delivered from the power supply to the payload at once, and over a very short distance. A launch loop uses its power supply to maintain a loop of masses flying from one end to the other, and adds only minimal energy to each one on each pass. The payload then couples into this giant flywheel. This spreads the load on the power supply out, and also lets the payload take a *much* longer time to accelerate. Try launching a person to orbital velocity in a cannon. The launch loop also solves the problem of how to build something that long and that high, without magical materials.
In short, the only real relationship between the two is that they both use a linear electric motor. The closes relative to a launch loop is probably a Space Fountain. For that one, look to Robert L. Forward instead of Heinlein.
Earth's gravity is substantially weaker at GSO. GSO altitude is large compared to the Earth's radius.
Space elevators *do* lower the energy that is supplied by the launch system.In a space elevator, the energy for the sideways motion comes from the rotation of the Earth (hence the Coriolis forces on the elevator mentioned in the summary). For GSO, that's less than the energy spent climbing up the gravity well, but it's still not trivial.
For escape trajectories, the elevator looks even more attractive -- once you pass GSO, the ride becomes free, and you gain energy from the dynamics of the system without spending any propellant / electricity / whatever. Time it carefully, and you just "fall" off the end of the cable on the right trajectory.
All of that said, rockets aren't *that* inefficient. For LEO, they can be 10% efficient or better (slightly worse for GSO). That's not great, but there are no proposed methods of getting energy to the elevator car that are all that efficient either, especially when you count electricity generation losses. Given the disparity in capital costs, and the fact that in neither case is the energy cost a noticeable fraction of the budget, I suspect rockets will win out for some time to come...
You mean this? (Original appears to be here but hidden behind icky flash and with worse presentation.)
Citation needed.
My google-fu is apparently weak today. I'm having trouble coming up with sources on the matter that aren't obviously biased one way or the other. The ones that seem to give the question a fair treatment tend to put the addictiveness of the two drugs at similar levels. The NY Times article is fairly comprehensive; despite the headline claim that nicotine is more addictive, the body of the article suggests that the two are fairly comparable. Exactly what constitutes "more addictive" is so hard to pin down (and so variable person to person) that a definitive answer seems unlikely and not very meaningful; suffice it to say, the two are comparable.