Helium alone isn't sufficient. Assuming there is no tritium in the reactants, the only possible reactions are deuterium-deuterium reactions and these must produce neutrons.
The possible reactions are listed below:
D+D -> T (1.01 MeV) + p (3.02 MeV) (50%) -> He3 (0.82 MeV) + n (2.45 MeV) (50%) <- most abundant fuel -> He4 + about 20 MeV of gamma rays (about 0.0001%; depends somewhat on temperature.)
Note that there is no way to control which of these reactions occurs, so half the fusions should produce neutrons. The other half produce protons which are also relatively easily detected, usually with a kind of silicon diode.
Furthermore if enough fusion is occuring to give a measureable temperature increase then the thing will be really roasting with neutrons and protons. It should make a geiger counter go nuts from activation products alone.
As nice as cold fusion would be, it doesn't work. And wishing it did won't help any.
N.B. I am omitting hydrogen-hydrogen reactions as those take place so slowly that it's not feasible. Also they'd be easy to check for simply by using non-deuterated water or acetone.
The TI-92 can play a lot more than Tetris. Try this doom-like game with a variety of weapons, pretty big levels, a storyline and vehicles! (It works on the TI-89 as well)
Can someone knowledgable please tell me if you only get one sonic boom when the plane first goes supersonic, or if you get a sonic boom everywhere it flies over while at more than Mach 1?
Actually gyroscopes of a sort (usually called "reaction wheels") are very commonly used for attitude control on space probes. I'm not sure if the ones on the ISS are there for reference or control, but it wouldn't surprise me if they were doing control. After all, it can't be that hard to get an attitude reference when you have a honkin' great Earth right outside your window...
Seriously? Is there a reference for that? Because making all electronic products lead-free is a really massive undertaking. I have no idea what they'll do for shielding in CRTs, for a start.
the PCBs in the transformer that go with their power supply
I don't know about your other points, but PCBs (Polychlorinated Biphenyl) are most definitely not used in computer PSU transformers. Back in the 1960s they were used as a flame-retardant additive to oil in big "pole pig" transformers that supply houses or whole streets. When they were found to be carcinogenic (and only mildly so, I might add) use was discontinued and they are absolutely forbidden from being used in any equipment manufactured nowadays. In fact I think it's an offense to even own anything that contains them.
FWIW I've heard second-hand stories of old electric company techs who would literally swim in the stuff. Cancer rates for them weren't significantly higher than the general population.
Actually solder is usually 40% lead, so it's not really a miniscule trace. I'd wager there really is quite a lot of it in motherboards and other circuit boards. I know that in the average CRT there's a kilogram or so, used to shield the user from xrays.
I'm not qualified to say how this can be safely disposed of, or whether it really needs to, but an awful lot of old electronics do end up in public landfills and other locations where they could potentially leach(sp?) into groundwater. It's something worth considering when people are upgrading their electronics and computers annually.
Any water taken from polar ice is effectively melted. This is because it isn't "used up" as such unless you electrolyse it or something - it will sooner or later (probably sooner) find its way back to the sea via rivers or groundwater. Because all the seas are connected the end result will be the sealevel rising just as much as if it had been melted directly from the icecap.
Of course you have to keep in mind that (and I'm pretty sure about this, not certain though, it's hard to wrap your head around) ice from the north pole displaces just as much water when it's ice as when it's water - because it's floating, melting that shouldn't change the level. However melting or mining ice from the south pole will cause the sea level to rise, because it's on land at the moment.
Hope that made some kind of sense, and if I'm wrong about any of it please correct me!
Water is moderately (bad pun) effective at shielding neutrons and would probably be used anyway in order to provide steam to operate turbines. I don't see how n+H could give T, but it might produce some D. However the oxygen would no doubt get activated too and that's not much use to anyone.
I think the plan, for Tokamaks at least, is to use a large blanket of lithium, and "breed" this into tritium for fuel use. In fact (not sure about this) they might use molten lithium as the working fluid instead of water.
Right. But "cold" in the sense of "cold fusion" means explicitly that none of these high temperatures and pressures are used. In the supposed cold fusion of the '80s, it was supposed to occur through some mysterious mechanism when electrolysing heavy water with platinum electrodes. Of course it didn't actually happen and there was no reason it should.
In this case there is a viable mechanism since the bubbles potentially can generate the high instantaneous pressure and energy that is known to be necessary.
D+D is easier than D+T, it requires less energy and the fusion cross-section is larger. You can get excited if you like but even if this news is correct (which would be pretty cool) power plants are many years away.
Also, fusion is not the wonderous clean energy source it's made out to be, because any type of fusion that's realistically possible outside of a star also produces neutrons, which activate the reactor materials leading to significant amounts of radioactive waste. That said, the waste problem is not so severe as with fission plants because generally isotopes with short halflifes are produced.
For more information about fusion in general and amateur efforts in particular - I'm building a tabletop reactor - check out http://www.fusor.net/
Or is it more likely for ejected planetary meteorites to make their way down the Sun's gravity well?
Yes, it's much more likely for meteroites to make it from Mars to Earth than the other way round. Several orders of magnitude more likely. They need much more delta V, although that said a considerable amount is needed just to escape from Mars' gravity well. In other words it is possible but considerably less probable. Whether any microbes would survive an impact of sufficient energy, as well as the long ride through cold vacuum is a different story...
No shit, I'm an atheist! But in your OP you still said "nature" in a way that meant "god":P Even the Gaia hypotheis doesn't allow for a thinking, planning planet/universe. I think it's maybe a little far out, myself, probably geological processes had a bit more to do with it but this isn't sort of thing we know a lot about.
The conversion between exit velocity and Isp is simple Ve=Isp*g
Is that g as in 9.8 ms^-2? Or is it the universal constant of gravitation? Either way I'd be interested if you could tell me how it relates to an ion drive in the middle of space?
Thanks
Henry
Slashdot Mirror
The possible reactions are listed below:
Note that there is no way to control which of these reactions occurs, so half the fusions should produce neutrons. The other half produce protons which are also relatively easily detected, usually with a kind of silicon diode.
Furthermore if enough fusion is occuring to give a measureable temperature increase then the thing will be really roasting with neutrons and protons. It should make a geiger counter go nuts from activation products alone.
As nice as cold fusion would be, it doesn't work. And wishing it did won't help any.
N.B. I am omitting hydrogen-hydrogen reactions as those take place so slowly that it's not feasible. Also they'd be easy to check for simply by using non-deuterated water or acetone.
Well, you should. We can't live on fossil fuels forever.
If you were referring to housecats, lions and tigers not being of the same species then that is correct.
There is no point wasting resources to search for an ark that couldn't have been there. The "great flood" is clearly impossible.
The TI-92 can play a lot more than Tetris. Try this doom-like game with a variety of weapons, pretty big levels, a storyline and vehicles! (It works on the TI-89 as well)
Can someone knowledgable please tell me if you only get one sonic boom when the plane first goes supersonic, or if you get a sonic boom everywhere it flies over while at more than Mach 1?
Actually gyroscopes of a sort (usually called "reaction wheels") are very commonly used for attitude control on space probes. I'm not sure if the ones on the ISS are there for reference or control, but it wouldn't surprise me if they were doing control. After all, it can't be that hard to get an attitude reference when you have a honkin' great Earth right outside your window...
Seriously? Is there a reference for that? Because making all electronic products lead-free is a really massive undertaking. I have no idea what they'll do for shielding in CRTs, for a start.
I don't know about your other points, but PCBs (Polychlorinated Biphenyl) are most definitely not used in computer PSU transformers. Back in the 1960s they were used as a flame-retardant additive to oil in big "pole pig" transformers that supply houses or whole streets. When they were found to be carcinogenic (and only mildly so, I might add) use was discontinued and they are absolutely forbidden from being used in any equipment manufactured nowadays. In fact I think it's an offense to even own anything that contains them.
FWIW I've heard second-hand stories of old electric company techs who would literally swim in the stuff. Cancer rates for them weren't significantly higher than the general population.
I'm not qualified to say how this can be safely disposed of, or whether it really needs to, but an awful lot of old electronics do end up in public landfills and other locations where they could potentially leach(sp?) into groundwater. It's something worth considering when people are upgrading their electronics and computers annually.
Hey, I haven't completed my high school education yet :P But yes, good analogy.
Yeah - It looks like it exactly cancels out. Neat!
This is of course also correct - so a global average temp increase will cause the oceans to swell.
Well I'm neither a dad nor a christian, but I think "Be fruitful and multiply" fulfils that - unless it's referring to tasty mathematicians?
Of course you have to keep in mind that (and I'm pretty sure about this, not certain though, it's hard to wrap your head around) ice from the north pole displaces just as much water when it's ice as when it's water - because it's floating, melting that shouldn't change the level. However melting or mining ice from the south pole will cause the sea level to rise, because it's on land at the moment.
Hope that made some kind of sense, and if I'm wrong about any of it please correct me!
Water is moderately (bad pun) effective at shielding neutrons and would probably be used anyway in order to provide steam to operate turbines. I don't see how n+H could give T, but it might produce some D. However the oxygen would no doubt get activated too and that's not much use to anyone. I think the plan, for Tokamaks at least, is to use a large blanket of lithium, and "breed" this into tritium for fuel use. In fact (not sure about this) they might use molten lithium as the working fluid instead of water.
In this case there is a viable mechanism since the bubbles potentially can generate the high instantaneous pressure and energy that is known to be necessary.
Also, fusion is not the wonderous clean energy source it's made out to be, because any type of fusion that's realistically possible outside of a star also produces neutrons, which activate the reactor materials leading to significant amounts of radioactive waste. That said, the waste problem is not so severe as with fission plants because generally isotopes with short halflifes are produced.
For more information about fusion in general and amateur efforts in particular - I'm building a tabletop reactor - check out http://www.fusor.net/
hehe, fair enough :)
Yes, it's much more likely for meteroites to make it from Mars to Earth than the other way round. Several orders of magnitude more likely. They need much more delta V, although that said a considerable amount is needed just to escape from Mars' gravity well. In other words it is possible but considerably less probable. Whether any microbes would survive an impact of sufficient energy, as well as the long ride through cold vacuum is a different story...
No shit, I'm an atheist! But in your OP you still said "nature" in a way that meant "god" :P Even the Gaia hypotheis doesn't allow for a thinking, planning planet/universe. I think it's maybe a little far out, myself, probably geological processes had a bit more to do with it but this isn't sort of thing we know a lot about.
Don't say "nature" when you mean "god". Nature is not anthropomorphic and doesn't think anything.
In Soviet Russia, they used a pencil.
Bullshit.
Thanks! I've actually had Sutton's book on my to-read list for a while, been interested in learning more about rockets. I'll try and find a copy.
Is that g as in 9.8 ms^-2? Or is it the universal constant of gravitation? Either way I'd be interested if you could tell me how it relates to an ion drive in the middle of space? Thanks Henry