So at neptune an corrected that would take a day, now takes 90000 days or 246 years! You are already past the Ort cloud before your even though 2% of the maneuver, Oh and the sun is still getting dimmer! At the Ort cloud the force is 600 million times less.
The error specified in TFA was 1,000,000 km at 2500 AU. Course correction required to recover from that error is about 1 m/sec. Which can be corrected quite nicely at about the orbit of Neptune by a "burn" that takes about four hours, based on your 90000x smaller acceleration. So if we started the "burn as we reached Neptune's orbit, we'd cover about five times the distance from Earth to Luna during the "burn".
I fail to see the issue. Yes, the acceleration continues to decrease. But it never decreases to zero, so your deltaV is still essentially infinite.
I think you are so dazzled by the tiny numbers involved in measuring acceleration of a lightsail in the deep dark that you're overlooking completely that the numbers attached to the hypothetical course correction are also very tiny numbers.
But wouldn't this trial be a separate as SCO v. Novell (or vice versa? who can even remember anymore...) with a new discovery phase?
No, discovery is over in the Novell case as well. Remember this was an appeal of a summary judgement, rendered after discovery. So, no, there's no new discovery phase.
And who's to say that they won't show some while(1) polling loop and claim infringement. We already know the courts don't give a fuck about the actual technical details in these cases...
Well, that would be sort of illegal. They are not allowed to present ANY evidence that has not already been shown to the opposing parties, as of the end of discovery. They haven't shown any evidence that Linux infringes Unix, therefore they may not show any such evidence in either of these trials.
And note that the trial judge for SCO vs. IBM and SCO vs Novell is the same guy. He's already seen ALL the evidence that can legally be presented in either case. And his rulings indicate that none of it has impressed him....
In the meantime everyone who uses or sells Linux stuff that isn't a giant like Novell is stuck in the crosshairs.
Not hardly. SCO hasn't proved it owns the Copyright.
It also has failed to prove that ANY Unix code is in Linux - remember, discovery is over in SCO vs IBM, where they alleged that very thing. And they didn't manage to come up with any infringing code.
Wouldn't conservation of energy still apply? You'd expend all the energy needed to lift the mass of "one standard rocket ship" out of Earth, land it on the moon, then expend even more energy getting it off the surface of the moon. How is that better than lifting "one standard rocket ship" directly off the Earth? (Yes, I admit there might be scale effects where we don't have a large efficient rocket capable of lifting said mass in one go.)
You build one "standard rocket" on Earth, which is capable of going to the moon.
You fill it with fuel, and send it off to the moon. It arrives with empty tanks.
Now, at this point, you have one "standard rocket" sans fuel, sitting on the moon. The rocket had to have had around 15 km/sec deltaV when it started, which was just about enough to go to the moon and land there.
You refuel it from fuel made on the moon. Now you have a rocket with 15 km/sec deltaV sitting on the moon.
Hmm, how far can you go with that...tough one. Allow for 5 km/sec to be blown on the landing wherever we're going to land. It probably won't be that much, since we'll probably use aerobraking to some extent, but let's be generous. 10 km/sec left.
We launch from the moon, on an orbit that'll pass within 500 km of the Earth's surface, where we'll make a second burn to send us outbound....
The rocket leaves the vicinity of Earth at somewhat more than solar escape speed.
In other words, such a "standard rocket", if refueled on the moon from fuel made on the moon, and relaunched, can go basically anywhere in the Solar System. It can do it relatively quickly (relative to what we can currently launch - we're not talking hundreds of km/sec here). Jupiter in a year, Mars in a few weeks, that sort of thing....
The government isn't going to hand out half a dozen contracts for space launch service, exactly in the same way it doesn't for any other service it purchases. The government isn't going to buy half a dozen boosters with near identical performance the same way it doesn't buy anything else from half a dozen companies.
In both cases it hands out *one* contract to *one* vendor or contractor - who then has the government by the balls. Exceptions to this are rare.
Oddly enough, NASA already has contracts (plural) with two different contractors to deliver supplies to the ISS.
Since one of them is SpaceX, which is busily developing the Dragon capsule for launch atop its Falcon 9, it's quite likely it'll be one of the contractors providing crew services to NASA by and by.
Note, by the by, that Falcon 9 is capable of lofting a Soyuz as soon as someone cares enough to design and build an adapter to fit a 2.25m diameter Soyuz onto a 3.6m diameter Falcon 9. Which means that even if Dragon is a complete flop, they can still get into the manned launch business by buying Soyuz capsules from whatever Russian company makes them.
First arrivals are technically immigrants, yes, but usually get the benefit of aboriginal status.
You are assuming that modern Native Americans were "first arrivals", rather than, say, the descendants of the third wave that wiped out or conquered the previous two waves. A shaky assumption at best.
The fact that the North American governments are silly enough to give "special" status to some people who claim to have been here first doesn't make someone who came here by way of Siberia less an immigrant than someone who came here by way of Ireland.
Personally, I'm tired of the distinction. We conquered the Amerinds. Before that, they conquered each other. There is little, if any, evidence that any particular group of Amerinds were the "first arrivals" in any particular place.
Actually, unless DNA shows you have Native American blood, you're all bleedin' immigrants.
Actually, even if you have Native American blood, you're an immigrant. Or do you somehow think that immigrating from Siberia 10,000+ years ago makes you less an immigrant?
Hint: humans didn't evolve in the Americas, hence any human in the Americas came from elsewhere, and would qualify as an immigrant to America.
Start looking at the numbers (over a million undocumented, uninsured and entirely legal US citizens live homeless in the New York subway system, and most cities don't bother to try and estimate any more).
Citation?
Somehow I doubt that one person in eight in New York City is living homeless in the New York subways, but I'm sure you'll be able to prove me wrong by providing the source of your information...
The last time major healthcare reform happened in the US was over 40 years ago.
That would be when we introduced free publicly funded health-care for the poor, right? The ones who seem to be having problems with third world diseases now?
When Clinton was President, we drew down our Army to 12 active divisions (one of the reasons the Guard has had to spend so much time in Iraq) and 12 Carrier groups. The post-WW2 military budget cuts that set the stage for the Korean War's opening moves.
Those aren't the only examples, just the most significant since WW2.
In other words, people vote against national defense all the time, often successfully.
No money = unable to get help if no government healthcare.
It's really that simple.
Which is probably why we've had Medicaid in place for longer than most/.'ers have been alive. The poor (those primarily affected by these problems) have had government health-care for most, if not all, of their lives
Well, half the voters don't even believe in public health. If the carriers of an epidemic are deemed unworthy of health care, the free market solution is to wait until everybody gets it, then treat those with money.
Hmm, this problem primarily affects the poor. The poor are already covered by public health-care (Medicaid) and have been so for decades, so I don't see how this is relevant.
Other than as an indictment of public health-care, since the problem has arisen since the introduction of public health-care for the poor.
Note, by the way, that passing Obama's version of public health-care would have little, if any, affect on this problem, since the current health-cre reform bills would do little, if anything, to bring more doctors to the out of the way parts of the USA where these issues seem to be appearing.
It makes perfect sense once you realize a few things:
First, slaves aren't the only ones who need intimidating -- other Jaffa could use a little intimidation, also.
And second, do you really want to say that the weapons given to you by your god aren't actually good weapons, only good firework shows? Seems that if a god makes it clear that he needs to impress people, he's admitting some failing as a god.
And third, do you really want to give your flunkies weapons that can be used effectively against YOU? Nah, you give them some PoS that looks good, sounds good, but doesn't really work terribly well.
Then when they complain about how hard it is to hit someone with the damn things, you tell them it's because they can't shoot worth a shit, and to spend more time at the range....
I think the 3.8% figure of repeat business is a good indicator that a lot of people agree.
I note that the current summary states the opposite of what your summary states - that only 3.8% of people would NOT buy an xBox 360 because of the failure rate. Which is correct?
Plenty of energy - not so much to spare once you account for propulsion, hotel loads, steam for the catapults, etc...
At routine cruise, you use less than 30% of the power available from your nuclear power plant. Alas, while a nuclear carrier can run for years at flank speed, its escorts can't, so it usually runs at speeds convenient to said escorts.
Why call it the "Oort Cloud" if there's nothing in it? My view is that such solar sails would be first used for Kuiper Belt targets and the heliopause (the latter not needing trajectory accuracy aside from making sure the probe heads away from the Sun). Later as we discover targets in the Oort cloud to investigate, probes could be sent out in this way. It's also good for interstellar missions. These velocities provide a good first stage boost. Accurate trajectories might greatly reduce the propellant consumed to correct the trajectory to another star.
Nobody ever said there was nothing in the Oort Cloud. But we're not going to be sending a lightsail out to the Oort Cloud to do more than fly past an Oort Cloud object really fast. Like 500+ km/sec fast.
And no, it's not particularly useful for interstellar missions. We're still talking about 2000+ years to make an interstellar jump. Note that the deltaV we're talking about for this lightsail is higher (but not much higher) than a similar amount of reaction mass being pushed out of a VASIMR or ion drive that we can build right now. In other words, by the time we get ready for interstellar trips at any reasonable speed (~10% c), this particular technology will be essentially useless.
Also, let us consider that hypothetical interstellar trip, and the inaccuracy of this proposed system. We have an expected error of 1 Gm in 2500 AU. Alphacent is about 270000 AU away. So this vehicle would be about 110 Gm off course by the time it reached Alphacent, absent relativistic corrections to its course. 110 Gm is rather less than one AU (150 Gm), so I doubt seriously we'll be really hard put to call that a trajectory requiring massive course corrections.
Again, remember that the relativistic effects only apply during the first very small part of the acceleration of the lightsail. By the time the lightsail reaches one AU from Sol, we'll be back to flat enough space that Newtonian approximations will suffice. And that leaves us (hypothetically) 2499 AU to make a 1 m/s course correction to get back in the groove.
Note that if we had a conventional rocket onboard to make such corrections, it would require about 100 grams of reaction mass to make the required correction. And that's the worst possible case - letting the lightsail do the work is a trivial two-week correction done anywhere out to 100 AU....
You don't have unlimited ability to maneuver unfortunately. Thrust goes down with 1/r2 from the sun. So once you are out past Jupiter you have almost all of your momentum vector fixed, and no thrust left to change it (thrust is down by a factor of 2500). Gravity maneuver would be about the only thing that would work after that. Even then, you are moving really fast and that on its own reduces the ability to maneuver.
Let's see. No reaction mass required for acceleration. Sounds unlimited to me. Yah, the acceleration is piss-poor out there in the deep dark, but the acceleration isn't going away until and unless the sail is shredded.
I do have to quibble with the notion of 'essentially unlimited ability to maneuver', however. The amount of thrust available decreases with increasing distance from the sun. (Indeed, it falls off as the inverse square of the distance.) If our hypothetical sail starts off at 0.1 AU from the sun for maximum thrust, its acceleration will be down to 1% of its original value as it crosses the Earth's orbit, and less than 0.04% when it crosses Jupiter's orbit. At Pluto's orbit, the probe will be able to call on less than a hundred-thousandth the amount of sunlight it saw when it started. In other words, errors in course selection which take place early will accumulate for the longest, and will be most apparent when the least thrust is available for correction.
Thirty year trip. The relativistic elements of the orbit will be non-issues by the time the lightsail is one AU from the sun.
Assume we take another year after that time to decide on a course-change. We have twenty-nine more years to change the orbit.
Assume further that the orbit really is off course by 1 Gm at a distance of 2500 AU. That means deltaV required to get back into design groove is about 1 m/sec. At one millionth of a gravity acceleration, that "burn" will take around two weeks.
great idea. now if only we could fix the moon in place, so that the dark side is always pointing towards the probe...
Even if we could, why bother? One laser at any point on the Moon can fire at the lightsail half the time. At the low accelerations possible out in the deep dark, it'll take considerably more than a month in all likelihood, so the "burn" will take place in two or more parts over several months (or years).
One that galls me is "noone". And the thing is that like "alot" it could actually be just a typo, not hitting the space bar hard enough. That's something I've done myself, and when I do I piss myself off!
Oddly enough, for all that I'm a grammar Nazi in real life (tm), things like "noone" and "alot" don't bother me. I see them (mostly correctly) as typos. And I don't hold typos against someone, since everyone does them from time to time.
They're/there/their errors, on the other hand, causes me to think "ignorant bastard", and tune out the message - if they can't spell something that obvious correctly, odds are they won't have anything to say that's worth the fraction of my lifespan required to read it.
2) Efficiency - getting the correct path to start with means you'll get there sooner. Perhaps a LOT sooner, because making course corrections might have the effect of slowing down spacecraft some, and even if you don't have to slow down the craft, making course corrections implies you are not taking the most optimal route. But, hey, what's a few extra AU between friends? Oh yeah, that's right, it's the difference between getting the craft to the correct place, and having it shoot by a few hundred million kilometers off to the side. I'm sure no one will mind if that multi-billion dollar space mission gets lost in space having missed it's objective.
Umm, no. Getting the correct path doesn't actually make you more likely to get there sooner, much less a lot sooner. You're just as likely to be going too fast as too slow, so you may get there sooner with a bad course than with a good course.
What's a few extra AU between friends? At the distances that obtain in the Oort Cloud, it's rounding error. Even if we were talking a few extra AU (remember, the number mentioned in the article was 1/150th of an AU.
Unless we have some specific target in the Oort Cloud that we aim for at the beginning of the trip, with no course-corrections, this is pretty much meaningless.
And with essentially unlimited ability to maneuver, course-corrections aren't going to be an issue, really.
If the original author died without any children or a spouse it becomes even more difficult to determine who should have the rights. Personally I think if no-one can say for sure who owns the work, then the world should be in the public domain.
Too easy for a publisher to move your work into the Public Domain that way. Which is good for them, not so good for your heirs.
And while you may not approve of a man's heirs making money from his work years after his death, I somehow doubt you'd approve of a publisher doing it either.
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The error specified in TFA was 1,000,000 km at 2500 AU. Course correction required to recover from that error is about 1 m/sec. Which can be corrected quite nicely at about the orbit of Neptune by a "burn" that takes about four hours, based on your 90000x smaller acceleration. So if we started the "burn as we reached Neptune's orbit, we'd cover about five times the distance from Earth to Luna during the "burn".
I fail to see the issue. Yes, the acceleration continues to decrease. But it never decreases to zero, so your deltaV is still essentially infinite.
I think you are so dazzled by the tiny numbers involved in measuring acceleration of a lightsail in the deep dark that you're overlooking completely that the numbers attached to the hypothetical course correction are also very tiny numbers.
No, discovery is over in the Novell case as well. Remember this was an appeal of a summary judgement, rendered after discovery. So, no, there's no new discovery phase.
Well, that would be sort of illegal. They are not allowed to present ANY evidence that has not already been shown to the opposing parties, as of the end of discovery. They haven't shown any evidence that Linux infringes Unix, therefore they may not show any such evidence in either of these trials.
And note that the trial judge for SCO vs. IBM and SCO vs Novell is the same guy. He's already seen ALL the evidence that can legally be presented in either case. And his rulings indicate that none of it has impressed him....
Not hardly. SCO hasn't proved it owns the Copyright.
It also has failed to prove that ANY Unix code is in Linux - remember, discovery is over in SCO vs IBM, where they alleged that very thing. And they didn't manage to come up with any infringing code.
You build one "standard rocket" on Earth, which is capable of going to the moon.
You fill it with fuel, and send it off to the moon. It arrives with empty tanks.
Now, at this point, you have one "standard rocket" sans fuel, sitting on the moon. The rocket had to have had around 15 km/sec deltaV when it started, which was just about enough to go to the moon and land there.
You refuel it from fuel made on the moon. Now you have a rocket with 15 km/sec deltaV sitting on the moon.
Hmm, how far can you go with that...tough one. Allow for 5 km/sec to be blown on the landing wherever we're going to land. It probably won't be that much, since we'll probably use aerobraking to some extent, but let's be generous. 10 km/sec left.
We launch from the moon, on an orbit that'll pass within 500 km of the Earth's surface, where we'll make a second burn to send us outbound....
The rocket leaves the vicinity of Earth at somewhat more than solar escape speed.
In other words, such a "standard rocket", if refueled on the moon from fuel made on the moon, and relaunched, can go basically anywhere in the Solar System. It can do it relatively quickly (relative to what we can currently launch - we're not talking hundreds of km/sec here). Jupiter in a year, Mars in a few weeks, that sort of thing....
No. Both of them have a specified total mass of supplies to deliver over a specified timeframe.
For instance, SpaceX is required to deliver a minimum of 20000 kg of supplies on a total of 12 flights between 2009 and 2016.
Orbital has a similar contract (20000 kg between 2009 and 2016), but the number of flights being paid for is different.
Oddly enough, NASA already has contracts (plural) with two different contractors to deliver supplies to the ISS.
Since one of them is SpaceX, which is busily developing the Dragon capsule for launch atop its Falcon 9, it's quite likely it'll be one of the contractors providing crew services to NASA by and by.
Note, by the by, that Falcon 9 is capable of lofting a Soyuz as soon as someone cares enough to design and build an adapter to fit a 2.25m diameter Soyuz onto a 3.6m diameter Falcon 9. Which means that even if Dragon is a complete flop, they can still get into the manned launch business by buying Soyuz capsules from whatever Russian company makes them.
You are assuming that modern Native Americans were "first arrivals", rather than, say, the descendants of the third wave that wiped out or conquered the previous two waves. A shaky assumption at best.
The fact that the North American governments are silly enough to give "special" status to some people who claim to have been here first doesn't make someone who came here by way of Siberia less an immigrant than someone who came here by way of Ireland.
Personally, I'm tired of the distinction. We conquered the Amerinds. Before that, they conquered each other. There is little, if any, evidence that any particular group of Amerinds were the "first arrivals" in any particular place.
Get over it.
Actually, even if you have Native American blood, you're an immigrant. Or do you somehow think that immigrating from Siberia 10,000+ years ago makes you less an immigrant?
Hint: humans didn't evolve in the Americas, hence any human in the Americas came from elsewhere, and would qualify as an immigrant to America.
Citation?
Somehow I doubt that one person in eight in New York City is living homeless in the New York subways, but I'm sure you'll be able to prove me wrong by providing the source of your information...
That would be when we introduced free publicly funded health-care for the poor, right? The ones who seem to be having problems with third world diseases now?
F-22.
When Clinton was President, we drew down our Army to 12 active divisions (one of the reasons the Guard has had to spend so much time in Iraq) and 12 Carrier groups. The post-WW2 military budget cuts that set the stage for the Korean War's opening moves.
Those aren't the only examples, just the most significant since WW2.
In other words, people vote against national defense all the time, often successfully.
Which is probably why we've had Medicaid in place for longer than most /.'ers have been alive. The poor (those primarily affected by these problems) have had government health-care for most, if not all, of their lives
Hmm, this problem primarily affects the poor. The poor are already covered by public health-care (Medicaid) and have been so for decades, so I don't see how this is relevant.
Other than as an indictment of public health-care, since the problem has arisen since the introduction of public health-care for the poor.
Note, by the way, that passing Obama's version of public health-care would have little, if any, affect on this problem, since the current health-cre reform bills would do little, if anything, to bring more doctors to the out of the way parts of the USA where these issues seem to be appearing.
Relative speed. The direction of motion is irrelevant, only the magnitude.
And third, do you really want to give your flunkies weapons that can be used effectively against YOU? Nah, you give them some PoS that looks good, sounds good, but doesn't really work terribly well.
Then when they complain about how hard it is to hit someone with the damn things, you tell them it's because they can't shoot worth a shit, and to spend more time at the range....
I note that the current summary states the opposite of what your summary states - that only 3.8% of people would NOT buy an xBox 360 because of the failure rate. Which is correct?
At routine cruise, you use less than 30% of the power available from your nuclear power plant. Alas, while a nuclear carrier can run for years at flank speed, its escorts can't, so it usually runs at speeds convenient to said escorts.
Nobody ever said there was nothing in the Oort Cloud. But we're not going to be sending a lightsail out to the Oort Cloud to do more than fly past an Oort Cloud object really fast. Like 500+ km/sec fast.
And no, it's not particularly useful for interstellar missions. We're still talking about 2000+ years to make an interstellar jump. Note that the deltaV we're talking about for this lightsail is higher (but not much higher) than a similar amount of reaction mass being pushed out of a VASIMR or ion drive that we can build right now. In other words, by the time we get ready for interstellar trips at any reasonable speed (~10% c), this particular technology will be essentially useless.
Also, let us consider that hypothetical interstellar trip, and the inaccuracy of this proposed system. We have an expected error of 1 Gm in 2500 AU. Alphacent is about 270000 AU away. So this vehicle would be about 110 Gm off course by the time it reached Alphacent, absent relativistic corrections to its course. 110 Gm is rather less than one AU (150 Gm), so I doubt seriously we'll be really hard put to call that a trajectory requiring massive course corrections.
Again, remember that the relativistic effects only apply during the first very small part of the acceleration of the lightsail. By the time the lightsail reaches one AU from Sol, we'll be back to flat enough space that Newtonian approximations will suffice. And that leaves us (hypothetically) 2499 AU to make a 1 m/s course correction to get back in the groove.
Note that if we had a conventional rocket onboard to make such corrections, it would require about 100 grams of reaction mass to make the required correction. And that's the worst possible case - letting the lightsail do the work is a trivial two-week correction done anywhere out to 100 AU....
Let's see. No reaction mass required for acceleration. Sounds unlimited to me. Yah, the acceleration is piss-poor out there in the deep dark, but the acceleration isn't going away until and unless the sail is shredded.
Thirty year trip. The relativistic elements of the orbit will be non-issues by the time the lightsail is one AU from the sun.
Assume we take another year after that time to decide on a course-change. We have twenty-nine more years to change the orbit.
Assume further that the orbit really is off course by 1 Gm at a distance of 2500 AU. That means deltaV required to get back into design groove is about 1 m/sec. At one millionth of a gravity acceleration, that "burn" will take around two weeks.
In other words, the problem is trivial.
Even if we could, why bother? One laser at any point on the Moon can fire at the lightsail half the time. At the low accelerations possible out in the deep dark, it'll take considerably more than a month in all likelihood, so the "burn" will take place in two or more parts over several months (or years).
Oddly enough, for all that I'm a grammar Nazi in real life (tm), things like "noone" and "alot" don't bother me. I see them (mostly correctly) as typos. And I don't hold typos against someone, since everyone does them from time to time.
They're/there/their errors, on the other hand, causes me to think "ignorant bastard", and tune out the message - if they can't spell something that obvious correctly, odds are they won't have anything to say that's worth the fraction of my lifespan required to read it.
Umm, no. Getting the correct path doesn't actually make you more likely to get there sooner, much less a lot sooner. You're just as likely to be going too fast as too slow, so you may get there sooner with a bad course than with a good course.
What's a few extra AU between friends? At the distances that obtain in the Oort Cloud, it's rounding error. Even if we were talking a few extra AU (remember, the number mentioned in the article was 1/150th of an AU.
Unless we have some specific target in the Oort Cloud that we aim for at the beginning of the trip, with no course-corrections, this is pretty much meaningless.
And with essentially unlimited ability to maneuver, course-corrections aren't going to be an issue, really.
Too easy for a publisher to move your work into the Public Domain that way. Which is good for them, not so good for your heirs.
And while you may not approve of a man's heirs making money from his work years after his death, I somehow doubt you'd approve of a publisher doing it either.