but there's still an originating central tracker for the MPAA to go after.
Absolutely no way could the MPAA go after the "kenosisp2p" DNS server. Otherwise all DNS servers are committing copyright infringement. When you feed "ftp://www.moviewarezsite.com/pub/MPAA_Movie_Here. avi" into a program, it does the exact same thing as this.
The MPAA could not go after the DNS server that resolves "www.moviewarezsite.com" (yah, good luck!) - but they could go after the holder of the IP address that it resolves to.
The problem now is that the MPAA still can't go after kenosisp2p, but the holder of the IP address that it resolves to changes quite often. They might end up going after those people, but they could get someone who's in another country, or has no money, or has only traded one movie ever, or has a hacked computer. Not a good legal strategy.
I'm not saying that they wouldn't try going after kenosisp2p. They might. But if they do, they'll almost definitely lose. They probably will lose going after BitTorrent trackers as well, but there's some argument there as there's hash information being passed around.
They did have an oxygen problem and had to correct it by adding pure oxygen to the environment when oxygen levels dropped too low, though.
The mission was to have humans live in a sealed environment. They unsealed it. Therefore, didn't the mission end early, whether or not they claim it did?
iirc rumble is a sony innovation if you can call it that
You don't recall correctly.
The N64's Rumble Pak was the original rumble accessory for a console system, released in 1997. Hence the reason we call it "rumble", not "shock" - as in, "dual shock", which was Sony's name for it. The dualshock controller didn't come out until almost a year later.
What word did I use from Stat 101? PSF (point spread function) is from astronomy. It's what a high-statistics point source looks like on a CCD.
All the other words and ideas are just from error propagation. That's from my undergrad physics lab.
But in reality, you have no idea what models were used to calculate the estimates
It's on the page. 99% of the uncertainty is within 3 sigma. No extended tails, which means it falls off fast enough that you can say that yes, the solution is pulling towards "Earth collision."
Why do I need a Ph.D. in statistics to know statistics? Do I need a Ph. D. in EE to know electronics? Dear God, do I need a Ph. D. in comp sci to know computer science? Yes, I might not know many very esoteric bits of info in statistics, but I certainly know the statistics in my own freaking field.
Did you read the first post?
Did you see the part where I mentioned that it depends on the PSF (point spread function) of the telescope? How is it guessing? I know how telescopes work. I know how you convolve that into an orbit solution, so I know what the error is going to roughly look like. Amazingly enough, when you take a bunch of errors and mung them together a bunch, you get something that looks Gaussian.
The only way the original post's statement would be true is if the resultant error from the PSFs convoluted into the orbit solutions ends up falling off slower than the area shrinks. There's virtually no way that's true. Most PSFs are approximately Gaussian. They certainly fall off faster than 1/x-ish (the solutions are typically highly constrained in 1D, so the available phase space drops as 1/x as the spread decreases).
Anyway, read the bloody definitions on the page. 99% of the uncertainty is contained within 3 sigma. That means it's at least (very, very crudely) approximately Gaussian. Even a flat distribution spread across 3 sigma which drops to 0 afterwards is "approximately" Gaussian - there are no extended tails. Plus if you could've seen the previous data, you'd notice that the solution is pulling closer to Earth. Which implies that the increased chance is not solely from the decrease in area.
That's not necessarily true. It depends on the characteristics of the error.
If the errors are Gaussian, if the nominal trajectory (i.e. "it misses the Earth by X+/-Y km") is accurate, but imprecise (that is, X is correct, but Y is large compared to X) then the probability of impact will decrease as the precision is improved (i.e. as Y decreases) because the "Earth impact" possibility moves farther out on the fringes of the observation, and the area doesn't shrink fast enough to compensate for this.
Of course, if the errors are flat (all solutions are equally likely - actually, if the PSF falls off slower than the area shrinks) then you're correct. I'm pretty sure that they're Gaussian, or approximately Gaussian, though. So the only way the probability could be increasing is if the nominal trajectory's impact parameter is decreasing - that is, closer impact.
I don't know why anyone would put system-wide configuration data anywhere else but in/etc. I mean, I've been working around *nix for going on fourteen years now, and that was always supposed to be the place.
Yah, but that's not what he's alluding to. What about/etc/thisapp/thisapp.conf instead of/etc/thisapp.conf (which pollutes/etc rather quickly)?
Hence, make it all configurable. Then you don't have to worry.
Not to be toooo nitpicky, but technically ye old "Upper Canada" is the modern southern Ontario
Definitely meant Northern Canada. "up" is north, "down" is south, "over" is west, "out" is east.:)
Didn't know there was a colloquial difference. I was thinking sparsely populated Northern Territories and whatever else the other area spun off from it was.
As in, the area where subsistence hunting is still practiced, not just possible.
A sufficiently severe catastrophe, whether an asteroid hit or something else, could take out 99% of the human population and still leave some 63 million people....
The question wasn't whether we'd just shrug it off and continue like nothing happened. The question was whether the human race would go extinct. You know, every last member of the species dead? That kind of extinct?
Well, be fair. First off, I have to say you're absolutely right. But in order to make a race extinct, you don't need to kill all of them right away. You just need to make it unlikely for that species to be able to adapt to the changing conditions.
Are humans so generalized now? Our population centers are fairly dense - remove a few cities and a huge percentage of the population goes away. Plus, basic survival skills are no longer necessary for life - most people rely on others to generate food. Remove a large section of the food generating sections of the population, and we might not survive.
However, to be fair, the people that are in the least dense areas (like Alaska, or upper Canada) are the most capable of handling themselves.
That's the main reason I think you're right, but it scares the crap out of me to believe that our species is resilient primarily due to rednecks who can hunt.
It's safer. Maximum distance from the Earth to the Moon is ~385,000 km. Maximum Earth-Mars distance is ~378,000,000 km, or roughly 1000 times that. The lightspeed lag from Earth to the Moon is 1 second. The maximum lag from the Earth to Mars is 1000 times that - or almost 20 minutes.
However, it depends what you mean by terraforming. It's not "terraform-able" - meaning "make it look like Earth" - it can't hold an Earth-like atmosphere for more than a few years - just too small. And it doesn't rotate fast enough to be able to have a normal weather cycle. But most importantly, it doesn't have enough hydrogen for any sort of terraforming in the "make it look like Earth" scale.
That being said, if you mean "make it habitable to humans, with domes included", sure, you can do that. It might need water importation, but that's not too bad (comets!).
Terraforming Luna, which due to its proximity would very possibly be catastrophically affected by any major cataclysm of extra-terrestrial origin affecting Earth, really does not meet this goal.
That'd be one damn big asteroid. What do you plan on hitting Earth with? Jupiter? Nothing that affects Earth and the Moon won't affect Mars as well that I can think of.
The Moon is an excellent "first step" for human habitation, though it does have a few more challenges than Mars (water, mainly).
If it sleeps so you can preserve your game, it wasn't in the deep-discharge regime, because it believed it had usable power left (that it used for sleep mode rather than going hard power-off). That usable power should be used to play, even if it's only a few seconds. A few seconds could be one more frag, after all.
A cutoff to avoid deep-discharge should be a hard power-off, rather than just a force into sleep mode. Most devices that use Li-Ions do have a low-voltage cutoff to prevent batteries from going into deep discharge.
With Wifi, though, putting itself to sleep is quite possibly the worst thing you could imagine, as when it goes to sleep, it breaks the network connection. With Wifi on, you'd want it to stay active as long as it possibly could.
Bitterly disappointed that I couldn't find any more info about the referenced project.
Because said project isn't completed yet, and I'm not really allowed to put info on how the project works yet if that info isn't published (which it isn't).
Old Palms have a serial port. So does just about every other piece of hardware, including the main electronics we use, the Motorola GPS receiver, and the custom-built radio as well.
It's just simple RS232 programming, so it's nothing special. Though I am proud of the GPS interface program. That one could actually be moderately useful for other projects. I should finish it up so that it's more useful...
How is it a format that doesn't travel well? It's thin and narrow --- precisely the format that travels well. The DS, in contrast, is very bulky.
The DS and PSP are virtually exactly the same size. Look at the pictures in the original article comparing the two.
PSP: 170 x 74 x 23 (mm) NDS: 147 x 82 x 31 (mm)
The NDS is significantly shorter, but a tiny bit wider and fatter. But if you consider 1/3 of an inch extra in 2 dimensions "very bulky", something's really wrong with you.
TMI did have an explosion - a hydrogen explosion when the core was exposed, water boiled, and the water vapor separated into hydrogen and oxygen.
I didn't actually think that Chernobyl was a meltdown, but maybe I was wrong - TMI was definitely a meltdown. Several presentations have actual depictions of what the core looks like nowadays, and it's really quite frightening - a huge pile of slag.
One of the most frustrating things about the "death of the PDA" is the fact that there was an ancillary benefit for a lot of us: PDAs are extraordinarily useful, cheap, single-purpose interface and logging devices!
In the project that I'm on, I've pushed for (and successfully gotten) Palms used for interfacing to the electronics in the project. They're far, far more useful than laptops for simple interfacing stuff (anything that can be interfaced with RS232, or nowadays USB). Cheaper, more rugged, much more visible in sunlight, and more importantly, far easier to use. Ever try typing on a keyboard in sub-freezing weather with high winds? Uck.
(On a side bad note, do try to keep Palms slightly in the shade. The screens tend to darken significantly with heat from direct sunlight).
and lots, lots more. To be honest, part of the reason that I bought a Palm for my own personal use is that I wanted to support them. A cheap PocketPC device is $150. A cheap Palm is under $100.
Plus, really, who wants to program for a Windows device? Palm even has a Linux programming chain, and a Linux simulator for Palm OS.
You would be charged for piracy. If anyone can play with only 1 cart then people can just download + play Metroid Prime off you any time they want to.
They can only download the multiplayer version.
Besides, people download the multiplayer version from the single player version with normal use. It's hard to claim that downloading it from a different source is piracy, unless the manual specifically mentions it. It'd be hard to say that it was intended to be restricted distribution when there were no restrictions given and the distribution was encouraged.
1) There are _maybe_ 5 entities in existance today (US, China, EU, Russia, India; and the last two are iffy) with the technology to actually even try to mine the moon.
Did you mean that Russia, India are the iffy two? I'd put the EU and India as the iffy two - neither of them (currently) have an independent manned space program.
Downplaying Russia is a little unfair: their "technology" is currently the only technology in use to actually transport people (and supplies!) to the ISS.
Now, if you're talking about economy, that's another thing. But technologically, Russia is at the very least #2, if not #1. Especially if you consider that the US is throwing the Shuttle out in 5 years or so.
Acceleration for a railgun is proportional to the length.
Shorter railgun - lower final velocity. Doesn't help you much. With a space elevator, the acceleration is gradual and the final velocity can be very high.
I haven't seen the calculations for what the tensile strength of the cable material needs to be for the moon
Kevlar'll do for the moon.
On the other hand, ground based electromagnetic acceleration is completely within our current technological grasp.
A lunar space elevator is within our grasp, if you read the article. Building it is pretty much a joke. You just need a heavy lifter rocket and a spool of cable. Maybe a bit of logistics need to be worked out for the anchor station, but that's, again, just a passive structure.
I disagree that building anything complicated on the lunar surface without a significant human presence is within our current grasp. Maybe in several years, but not now. The elevator, however, is much simpler.
This has nothing to do with centrifigal force, like an Earth-based elevator where the counterweight keeps the cable taut.
Sigh. This has everything to do with centrifugal force. It is exactly the same as a terrestrial space elevator. That's why you could build a cable to L4, or L5, even though gravity doesn't appear to balance there at all. It's all about solving the 3 body problem in a rotating frame.
When we talk about a space elevator for Earth, we're talking about building a cable to geosynchronous orbit. At that point, objects orbiting Earth appear to stay above the same point on the Earth's surface because they rotate with the same angular velocity as Earth.
At the L1 point, objects appear to stay at the same point with respect to the Moon because they rotate with the same angular velocity as the Moon. This doesn't happen at the naive calculation that you'd do to get "lunar synchronous orbit" (which is something like half the distance to the Earth) because the Earth is the dominant gravity player in the Earth-Moon system. That's why you have to solve the 3 body problem, whereas for Earth's GEO case, you can ignore the Moon because Earth rotates so fast and Earth is so massive. But centrifugal force does play a role.
However, the cable is an extended object. From an orbital mechanics point of view, the cable stays at L1 because it's in orbit at L1. From the lunar surface's point of view, though, the cable stays upright because it's taut under a large amount of tension, caused by centrifugal force and gravity.
And on a terrestrial cable, the counterweight doesn't keep the cable taut. You don't need a counterweight. You just need the center of mass roughly at GEO.
For lunar launches, the Moon's lack of an atmosphere makes mass drivers practical.
Why do people push mass drivers so much?
They're great for weapons, I'd imagine. But the acceleration people usually talk about for reasonable lengths is 10,000 g. I would not want to be the structural engineer designing that.
Since the acceleration on a space elevator is distributed (and part of it comes from stealing angular momentum from the body itself) the stress on the launched body is virtually nothing - arbitrarily low, in fact.
But is it enough to justify building and maintaining the structure?
I don't see how a very long Kevlar cable will require more maintainance than a railgun.
The purpose of a space elevator is to bring something to orbital speed without the inefficiency of a rocket and carrying your own fuel to make such a large delta-V.
That's too much rocket-think. There are other advantages to an elevator. For one, no, or little, structural stress. The acceleration is mild, and so you don't need to design something to absorb huge shocks. Railguns simply can't do that.
Also: how, precisely, is a railgun acceleration system easier than a big spool of Kevlar cable? The railgun is an active launch system. The cable is a passive launch system. Assuming you can deal with the robustness of the cable itself to impacts, etc. (which, of course, you would need to deal with for a railgun acceleration system), an elevator requires far less maintenance.
Sneak a nice big bomb into a satellite/space vehicle/payload, put it on one of the lifts and blow it up part of the way.
If the operators of the cable can't tell that there's a "big bomb" onto one of the payloads, then the Three Stooges have to be operating the cable.
Terrorists haven't snuck bombs onto satellite launches, space shuttle launches, or Soyuz launches. Obviously we have the capability to screen such launches.
And, of course, if an elevator is built, you just send another elevator up using it, and leave it there, spooled.
Destroying something that can be replaced in a few weeks is not attractive.
Slashdot Mirror
but there's still an originating central tracker for the MPAA to go after.
. avi" into a program, it does the exact same thing as this.
Absolutely no way could the MPAA go after the "kenosisp2p" DNS server. Otherwise all DNS servers are committing copyright infringement. When you feed "ftp://www.moviewarezsite.com/pub/MPAA_Movie_Here
The MPAA could not go after the DNS server that resolves "www.moviewarezsite.com" (yah, good luck!) - but they could go after the holder of the IP address that it resolves to.
The problem now is that the MPAA still can't go after kenosisp2p, but the holder of the IP address that it resolves to changes quite often. They might end up going after those people, but they could get someone who's in another country, or has no money, or has only traded one movie ever, or has a hacked computer. Not a good legal strategy.
I'm not saying that they wouldn't try going after kenosisp2p. They might. But if they do, they'll almost definitely lose. They probably will lose going after BitTorrent trackers as well, but there's some argument there as there's hash information being passed around.
I guess hearing opinions you disagree with is just too much to take, isn't it?
If the channel was called Fox Opinions, it'd be fine.
They did have an oxygen problem and had to correct it by adding pure oxygen to the environment when oxygen levels dropped too low, though.
The mission was to have humans live in a sealed environment. They unsealed it. Therefore, didn't the mission end early, whether or not they claim it did?
Is this what you wanted, then?
iirc rumble is a sony innovation if you can call it that
You don't recall correctly.
The N64's Rumble Pak was the original rumble accessory for a console system, released in 1997. Hence the reason we call it "rumble", not "shock" - as in, "dual shock", which was Sony's name for it. The dualshock controller didn't come out until almost a year later.
words and ideas from Stat 101.
What word did I use from Stat 101? PSF (point spread function) is from astronomy. It's what a high-statistics point source looks like on a CCD.
All the other words and ideas are just from error propagation. That's from my undergrad physics lab.
But in reality, you have no idea what models were used to calculate the estimates
It's on the page. 99% of the uncertainty is within 3 sigma. No extended tails, which means it falls off fast enough that you can say that yes, the solution is pulling towards "Earth collision."
Why do I need a Ph.D. in statistics to know statistics? Do I need a Ph. D. in EE to know electronics? Dear God, do I need a Ph. D. in comp sci to know computer science? Yes, I might not know many very esoteric bits of info in statistics, but I certainly know the statistics in my own freaking field.
Did you read the first post?
Did you see the part where I mentioned that it depends on the PSF (point spread function) of the telescope? How is it guessing? I know how telescopes work. I know how you convolve that into an orbit solution, so I know what the error is going to roughly look like. Amazingly enough, when you take a bunch of errors and mung them together a bunch, you get something that looks Gaussian.
The only way the original post's statement would be true is if the resultant error from the PSFs convoluted into the orbit solutions ends up falling off slower than the area shrinks. There's virtually no way that's true. Most PSFs are approximately Gaussian. They certainly fall off faster than 1/x-ish (the solutions are typically highly constrained in 1D, so the available phase space drops as 1/x as the spread decreases).
Anyway, read the bloody definitions on the page. 99% of the uncertainty is contained within 3 sigma. That means it's at least (very, very crudely) approximately Gaussian. Even a flat distribution spread across 3 sigma which drops to 0 afterwards is "approximately" Gaussian - there are no extended tails. Plus if you could've seen the previous data, you'd notice that the solution is pulling closer to Earth. Which implies that the increased chance is not solely from the decrease in area.
That's not necessarily true. It depends on the characteristics of the error.
If the errors are Gaussian, if the nominal trajectory (i.e. "it misses the Earth by X+/-Y km") is accurate, but imprecise (that is, X is correct, but Y is large compared to X) then the probability of impact will decrease as the precision is improved (i.e. as Y decreases) because the "Earth impact" possibility moves farther out on the fringes of the observation, and the area doesn't shrink fast enough to compensate for this.
Of course, if the errors are flat (all solutions are equally likely - actually, if the PSF falls off slower than the area shrinks) then you're correct. I'm pretty sure that they're Gaussian, or approximately Gaussian, though. So the only way the probability could be increasing is if the nominal trajectory's impact parameter is decreasing - that is, closer impact.
I don't know why anyone would put system-wide configuration data anywhere else but in
Yah, but that's not what he's alluding to. What about
Hence, make it all configurable. Then you don't have to worry.
Not to be toooo nitpicky, but technically ye old "Upper Canada" is the modern southern Ontario
Definitely meant Northern Canada. "up" is north, "down" is south, "over" is west, "out" is east.
Didn't know there was a colloquial difference. I was thinking sparsely populated Northern Territories and whatever else the other area spun off from it was.
As in, the area where subsistence hunting is still practiced, not just possible.
A sufficiently severe catastrophe, whether an asteroid hit or something else, could take out 99% of the human population and still leave some 63 million people. ...
The question wasn't whether we'd just shrug it off and continue like nothing happened. The question was whether the human race would go extinct. You know, every last member of the species dead? That kind of extinct?
Well, be fair. First off, I have to say you're absolutely right. But in order to make a race extinct, you don't need to kill all of them right away. You just need to make it unlikely for that species to be able to adapt to the changing conditions.
Are humans so generalized now? Our population centers are fairly dense - remove a few cities and a huge percentage of the population goes away. Plus, basic survival skills are no longer necessary for life - most people rely on others to generate food. Remove a large section of the food generating sections of the population, and we might not survive.
However, to be fair, the people that are in the least dense areas (like Alaska, or upper Canada) are the most capable of handling themselves.
That's the main reason I think you're right, but it scares the crap out of me to believe that our species is resilient primarily due to rednecks who can hunt.
I can't think of a real reason to terraform it.
It's safer. Maximum distance from the Earth to the Moon is ~385,000 km. Maximum Earth-Mars distance is ~378,000,000 km, or roughly 1000 times that. The lightspeed lag from Earth to the Moon is 1 second. The maximum lag from the Earth to Mars is 1000 times that - or almost 20 minutes.
However, it depends what you mean by terraforming. It's not "terraform-able" - meaning "make it look like Earth" - it can't hold an Earth-like atmosphere for more than a few years - just too small. And it doesn't rotate fast enough to be able to have a normal weather cycle. But most importantly, it doesn't have enough hydrogen for any sort of terraforming in the "make it look like Earth" scale.
That being said, if you mean "make it habitable to humans, with domes included", sure, you can do that. It might need water importation, but that's not too bad (comets!).
Terraforming Luna, which due to its proximity would very possibly be catastrophically affected by any major cataclysm of extra-terrestrial origin affecting Earth, really does not meet this goal.
That'd be one damn big asteroid. What do you plan on hitting Earth with? Jupiter? Nothing that affects Earth and the Moon won't affect Mars as well that I can think of.
The Moon is an excellent "first step" for human habitation, though it does have a few more challenges than Mars (water, mainly).
If it sleeps so you can preserve your game, it wasn't in the deep-discharge regime, because it believed it had usable power left (that it used for sleep mode rather than going hard power-off). That usable power should be used to play, even if it's only a few seconds. A few seconds could be one more frag, after all.
A cutoff to avoid deep-discharge should be a hard power-off, rather than just a force into sleep mode. Most devices that use Li-Ions do have a low-voltage cutoff to prevent batteries from going into deep discharge.
With Wifi, though, putting itself to sleep is quite possibly the worst thing you could imagine, as when it goes to sleep, it breaks the network connection. With Wifi on, you'd want it to stay active as long as it possibly could.
Bitterly disappointed that I couldn't find any more info about the referenced project.
Because said project isn't completed yet, and I'm not really allowed to put info on how the project works yet if that info isn't published (which it isn't).
Old Palms have a serial port. So does just about every other piece of hardware, including the main electronics we use, the Motorola GPS receiver, and the custom-built radio as well.
It's just simple RS232 programming, so it's nothing special. Though I am proud of the GPS interface program. That one could actually be moderately useful for other projects. I should finish it up so that it's more useful...
How is it a format that doesn't travel well? It's thin and narrow --- precisely the format that travels well. The DS, in contrast, is very bulky.
The DS and PSP are virtually exactly the same size. Look at the pictures in the original article comparing the two.
PSP: 170 x 74 x 23 (mm)
NDS: 147 x 82 x 31 (mm)
The NDS is significantly shorter, but a tiny bit wider and fatter. But if you consider 1/3 of an inch extra in 2 dimensions "very bulky", something's really wrong with you.
melted reactor [NO explosion]
TMI did have an explosion - a hydrogen explosion when the core was exposed, water boiled, and the water vapor separated into hydrogen and oxygen.
I didn't actually think that Chernobyl was a meltdown, but maybe I was wrong - TMI was definitely a meltdown. Several presentations have actual depictions of what the core looks like nowadays, and it's really quite frightening - a huge pile of slag.
In the project that I'm on, I've pushed for (and successfully gotten) Palms used for interfacing to the electronics in the project. They're far, far more useful than laptops for simple interfacing stuff (anything that can be interfaced with RS232, or nowadays USB). Cheaper, more rugged, much more visible in sunlight, and more importantly, far easier to use. Ever try typing on a keyboard in sub-freezing weather with high winds? Uck.
(On a side bad note, do try to keep Palms slightly in the shade. The screens tend to darken significantly with heat from direct sunlight).
Palms have been used for
and lots, lots more. To be honest, part of the reason that I bought a Palm for my own personal use is that I wanted to support them. A cheap PocketPC device is $150. A cheap Palm is under $100.
Plus, really, who wants to program for a Windows device? Palm even has a Linux programming chain, and a Linux simulator for Palm OS.
You would be charged for piracy. If anyone can play with only 1 cart then people can just download + play Metroid Prime off you any time they want to.
They can only download the multiplayer version.
Besides, people download the multiplayer version from the single player version with normal use. It's hard to claim that downloading it from a different source is piracy, unless the manual specifically mentions it. It'd be hard to say that it was intended to be restricted distribution when there were no restrictions given and the distribution was encouraged.
1) There are _maybe_ 5 entities in existance today (US, China, EU, Russia, India; and the last two are iffy) with the technology to actually even try to mine the moon.
Did you mean that Russia, India are the iffy two? I'd put the EU and India as the iffy two - neither of them (currently) have an independent manned space program.
Downplaying Russia is a little unfair: their "technology" is currently the only technology in use to actually transport people (and supplies!) to the ISS.
Now, if you're talking about economy, that's another thing. But technologically, Russia is at the very least #2, if not #1. Especially if you consider that the US is throwing the Shuttle out in 5 years or so.
Acceleration for a railgun is proportional to the length.
Shorter railgun - lower final velocity. Doesn't help you much. With a space elevator, the acceleration is gradual and the final velocity can be very high.
I haven't seen the calculations for what the tensile strength of the cable material needs to be for the moon
Kevlar'll do for the moon.
On the other hand, ground based electromagnetic acceleration is completely within our current technological grasp.
A lunar space elevator is within our grasp, if you read the article. Building it is pretty much a joke. You just need a heavy lifter rocket and a spool of cable. Maybe a bit of logistics need to be worked out for the anchor station, but that's, again, just a passive structure.
I disagree that building anything complicated on the lunar surface without a significant human presence is within our current grasp. Maybe in several years, but not now. The elevator, however, is much simpler.
This has nothing to do with centrifigal force, like an Earth-based elevator where the counterweight keeps the cable taut.
Sigh. This has everything to do with centrifugal force. It is exactly the same as a terrestrial space elevator. That's why you could build a cable to L4, or L5, even though gravity doesn't appear to balance there at all. It's all about solving the 3 body problem in a rotating frame.
When we talk about a space elevator for Earth, we're talking about building a cable to geosynchronous orbit. At that point, objects orbiting Earth appear to stay above the same point on the Earth's surface because they rotate with the same angular velocity as Earth.
At the L1 point, objects appear to stay at the same point with respect to the Moon because they rotate with the same angular velocity as the Moon. This doesn't happen at the naive calculation that you'd do to get "lunar synchronous orbit" (which is something like half the distance to the Earth) because the Earth is the dominant gravity player in the Earth-Moon system. That's why you have to solve the 3 body problem, whereas for Earth's GEO case, you can ignore the Moon because Earth rotates so fast and Earth is so massive. But centrifugal force does play a role.
However, the cable is an extended object. From an orbital mechanics point of view, the cable stays at L1 because it's in orbit at L1. From the lunar surface's point of view, though, the cable stays upright because it's taut under a large amount of tension, caused by centrifugal force and gravity.
And on a terrestrial cable, the counterweight doesn't keep the cable taut. You don't need a counterweight. You just need the center of mass roughly at GEO.
For lunar launches, the Moon's lack of an atmosphere makes mass drivers practical.
Why do people push mass drivers so much?
They're great for weapons, I'd imagine. But the acceleration people usually talk about for reasonable lengths is 10,000 g . I would not want to be the structural engineer designing that.
Since the acceleration on a space elevator is distributed (and part of it comes from stealing angular momentum from the body itself) the stress on the launched body is virtually nothing - arbitrarily low, in fact.
But is it enough to justify building and maintaining the structure?
I don't see how a very long Kevlar cable will require more maintainance than a railgun.
The purpose of a space elevator is to bring something to orbital speed without the inefficiency of a rocket and carrying your own fuel to make such a large delta-V.
That's too much rocket-think. There are other advantages to an elevator. For one, no, or little, structural stress. The acceleration is mild, and so you don't need to design something to absorb huge shocks. Railguns simply can't do that.
Also: how, precisely, is a railgun acceleration system easier than a big spool of Kevlar cable? The railgun is an active launch system. The cable is a passive launch system. Assuming you can deal with the robustness of the cable itself to impacts, etc. (which, of course, you would need to deal with for a railgun acceleration system), an elevator requires far less maintenance.
Sneak a nice big bomb into a satellite/space vehicle/payload, put it on one of the lifts and blow it up part of the way.
If the operators of the cable can't tell that there's a "big bomb" onto one of the payloads, then the Three Stooges have to be operating the cable.
Terrorists haven't snuck bombs onto satellite launches, space shuttle launches, or Soyuz launches. Obviously we have the capability to screen such launches.
And, of course, if an elevator is built, you just send another elevator up using it, and leave it there, spooled.
Destroying something that can be replaced in a few weeks is not attractive.
Terrorists have better targets.