Re:First things first
on
GPS on Mars?
·
· Score: 1
I would imagine so, probably (IANA orbital mechanic, though I did skim through "Fundamentals of Astrodynamics") - I don't think it would be a lot of use as a positioning system though because from the Moon you'd only be able to see two or maybe three satellites from any position. The ping time to them would be huge as well, I don't know if that would matter.
Long-distance navigation on the moon isn't a trivial problem, especially since the distance to the horizon is so short... but modern gyroscopes can probably handle it.
Good analogy? No it isn't because none of those things are remotely realistic for cars. As an analogy, it's stretched further than Goatse!
Re:First things first
on
GPS on Mars?
·
· Score: 4, Informative
We can't put GPS satellites (or any other permanent satellite) around the Moon. Its mass is too unevenly distributed, and the gravitational field too warped, to have any permanent stable orbits. Anything put into orbit will crash after a few hundred orbits, without manual correction with rockets.
Stay out of the tightly-focused beam, and you'll be fine. If you don't actually catch enough to cook you there and then, it can't hurt you - radar operators used to commonly stand in front of the dishes on cold days to warm up. It's only resistive heating.
Actually, the beamed power is not tricky at all. It is easy to do using microwaves, which can be produced efficiently with magnetrons (evidence is in your microwave oven) and converted back into electricity using rectennas.
A rectenna is basically an array of tiny antennas and diodes which rectify the microwaves back to DC. They have been around since the '60s and can operate at up to 80% efficiency (record is 84% efficiency for 30kW of power).
In 1964 William C. Brown succeeded in demonstrating a microwave-powered helicopter! (Sorry, I was unable to find any pictures). You can find more interesting info on this google search.
You have to wonder how things will work out if this is carried through to its logical conclusion - all menial/unskilled jobs, and a lot of skilled ones, are replaced by robots that can do the job more efficiently. A lot of people are now out of work, or make-work positions for them have to be created. I think in these circumstances, a communist or socialist system begins to look good because now fewer people have to work and the benefits can be enjoyed by everyone. OTOH I don't think we're at this stage yet, nor will we be for some time.
Not necessarily. If the satellites are in geostationary orbit, which is likely because you'd want them to "hover" over the receiving antennae, they can extend a significant distance out past the Earth's sillhouette. Geostationary orbit has a diameter of about 84300km while the Earth is only 12800km wide.
That said, these satellites are still pretty implausible, as is the idea that heat pollution is a major worry. I think it would pale in comparison to the varying amount of sunlight absorbed by the Earth due to changing cloud cover.
Amusing that your name is "Fulcrum"... you can get quite a moment from holding a heavy mass at the end of an extended arm. Admittedly, less so for a child. Myself, I can barely lift 3kg like that - I just tried. I consider myself moderately fit.
True up to a point - but the new BOINC client comes with a different screensaver that is much cooler. Pretty good incentive to upgrade, as well as the fact that it seems to burn through data units about twice as fast on my computer.
I'm pretty sure the NEAs are called that because they have orbits relatively close to Earth's, rather than out past Mars. This doesn't mean that the asteroid itself is near Earth for very long - it might pass within a couple of million km once a "year", but at that distance you won't have much luck at getting pretty pictures. The Earth would look the size of the moon in the sky.
I agree it would be hella cool. But the view? Out where the asteroids are, you're so far from Earth that it would look similar to how Venus looks from here. A blue dot, brighter than the stars probably. When you wake up every "morning" all you'd see are stars, not too different to how the night sky looks from Earth. Perhaps a few more of them. Either way I think the view would get boring quickly.
Re:At least it's not a "For Dummies" book
on
Linux for Non-Geeks
·
· Score: 1
Thanks for the explanation:)
Re:At least it's not a "For Dummies" book
on
Linux for Non-Geeks
·
· Score: 1
This curious "dummy" is confused about how that relates to the parent comment... could you explain?
Untrue. High voltage does not melt wires. Heating effects are caused by high currents, which you aren't going to get from something that can produce this kind of voltage in a portable device.
What? Technology didn't help win the war in Iraq? Are you serious? Whether or not the war was just is debatable, but it wouldn't have been anywhere NEAR as clean and precise without GPS and laser-guided bombs etc etc.
Electrolysis takes fairly large amoutns of energy, yes - enough to break the covalent O-H chemical bonds in the water molecules. But the amount of energy you can get by nuclear fusion of the hydrogen released is far far far more, say 100,000 times more, even considering that you can only use about 1 in 6000 atoms of hydrogen.
This doesn't break any laws of physics - you are slowly using up the deuterium from the sea but there really is a shitload of it. The difficulties lie in engineering a reactor to do the nuclear fusion efficiently, because it also requires a lot of energy to contain the hydrogen plasma and stop it pushing itself apart. But again, if you can do it right then the energy released by fusion can more than outweigh that used to contain the plasma.
As has already been pointed out, there are other more efficient ways of splitting water into hydrogen and oxygen, which may get you another couple of % efficiency.
Actually fusion isn't the cure-all it's widely touted to be. It produces less radioactive waste than fission, but still a fair amount (although most of it is short half-life stuff). On the other hand, fuel is much easier to get hold of by electrolysing seawater and fractionating off the deuterium.
Slashdot Mirror
Long-distance navigation on the moon isn't a trivial problem, especially since the distance to the horizon is so short... but modern gyroscopes can probably handle it.
Good analogy? No it isn't because none of those things are remotely realistic for cars. As an analogy, it's stretched further than Goatse!
We can't put GPS satellites (or any other permanent satellite) around the Moon. Its mass is too unevenly distributed, and the gravitational field too warped, to have any permanent stable orbits. Anything put into orbit will crash after a few hundred orbits, without manual correction with rockets.
Stay out of the tightly-focused beam, and you'll be fine. If you don't actually catch enough to cook you there and then, it can't hurt you - radar operators used to commonly stand in front of the dishes on cold days to warm up. It's only resistive heating.
A rectenna is basically an array of tiny antennas and diodes which rectify the microwaves back to DC. They have been around since the '60s and can operate at up to 80% efficiency (record is 84% efficiency for 30kW of power).
In 1964 William C. Brown succeeded in demonstrating a microwave-powered helicopter! (Sorry, I was unable to find any pictures). You can find more interesting info on this google search.
You have to wonder how things will work out if this is carried through to its logical conclusion - all menial/unskilled jobs, and a lot of skilled ones, are replaced by robots that can do the job more efficiently. A lot of people are now out of work, or make-work positions for them have to be created. I think in these circumstances, a communist or socialist system begins to look good because now fewer people have to work and the benefits can be enjoyed by everyone. OTOH I don't think we're at this stage yet, nor will we be for some time.
Anyway, I'm off to use the ATM machine.. if only I can remember my PIN number.
That said, these satellites are still pretty implausible, as is the idea that heat pollution is a major worry. I think it would pale in comparison to the varying amount of sunlight absorbed by the Earth due to changing cloud cover.
Correction - the weight I tried to lift was 7kg. You're right, 3kg should be a piece of cake.
Amusing that your name is "Fulcrum"... you can get quite a moment from holding a heavy mass at the end of an extended arm. Admittedly, less so for a child. Myself, I can barely lift 3kg like that - I just tried. I consider myself moderately fit.
True up to a point - but the new BOINC client comes with a different screensaver that is much cooler. Pretty good incentive to upgrade, as well as the fact that it seems to burn through data units about twice as fast on my computer.
Here is a diagram showing the orbit of a typical near-Earth asteroid.
I'm pretty sure the NEAs are called that because they have orbits relatively close to Earth's, rather than out past Mars. This doesn't mean that the asteroid itself is near Earth for very long - it might pass within a couple of million km once a "year", but at that distance you won't have much luck at getting pretty pictures. The Earth would look the size of the moon in the sky.
I agree it would be hella cool. But the view? Out where the asteroids are, you're so far from Earth that it would look similar to how Venus looks from here. A blue dot, brighter than the stars probably. When you wake up every "morning" all you'd see are stars, not too different to how the night sky looks from Earth. Perhaps a few more of them. Either way I think the view would get boring quickly.
Thanks for the explanation :)
This curious "dummy" is confused about how that relates to the parent comment... could you explain?
As usual the Japanese are way ahead of us.
Bollocks. There's no way anything biological the size of a bacterium could possibly think.
Exactly. No matter how low the resistance, only a very low current (microamps, probably) is available from the shocking device.
Untrue. High voltage does not melt wires. Heating effects are caused by high currents, which you aren't going to get from something that can produce this kind of voltage in a portable device.
What? Technology didn't help win the war in Iraq? Are you serious? Whether or not the war was just is debatable, but it wouldn't have been anywhere NEAR as clean and precise without GPS and laser-guided bombs etc etc.
Notice how the submitter was anonymous... I don't think it was the same guy as the sign owner himself.
This doesn't break any laws of physics - you are slowly using up the deuterium from the sea but there really is a shitload of it. The difficulties lie in engineering a reactor to do the nuclear fusion efficiently, because it also requires a lot of energy to contain the hydrogen plasma and stop it pushing itself apart. But again, if you can do it right then the energy released by fusion can more than outweigh that used to contain the plasma.
As has already been pointed out, there are other more efficient ways of splitting water into hydrogen and oxygen, which may get you another couple of % efficiency.
I've always wondered, do they make extra slutty olive oil? Or can you pay extra and get olive oil that's never even seen a man?
Actually fusion isn't the cure-all it's widely touted to be. It produces less radioactive waste than fission, but still a fair amount (although most of it is short half-life stuff). On the other hand, fuel is much easier to get hold of by electrolysing seawater and fractionating off the deuterium.