PSSST... I think you meant to say "NASA has been launching RTGs for some time now". SRGs are a newer and more efficient design that have shown promise, but could cause errors in instrumentation due to slight vibrations. SRGs have not yet flown.
Probably the main reason NASA went solar instead of nuclear on this mission was weight.
RTGs get ~75W per 2.5 pounds of plutonium. Considering how heavy the batteries are that the rover is carrying, I seriously doubt that weight was the deciding factor.
Do they launch it over a section of the ocean that's devoid of tide and current?
Hardly. NASA wants those RTGs back so they can reuse them on the next mission!
Actually, the black box would be too heavy to be carried by tides. It sinks to the bottom instead. Pretty normal for materials with atomic numbers above 90.
You prove my point again. What benefit? The Sojourner is a test rover with very minimal capabilities. Why keep it running for years?
You're having a really tough time her, aren't you? The benefit is having a functional and transmitting device on Mars for the years between Mars missions. The risks are that a black box could fall into the ocean and a diver would have to pick it up later. Now, let's do your equation.
We'll set the odds of a failed launch at about 1 in 4 or 0.25. The consequences are some inconvenience, so we'll set it to 5. The benefits are a robot that will keep running for as long as we want to pay attention to it. We'll assign that as 100.
100 - (0.25 * 5) = 98.75
That looks like a good equation to me. Let's say that the RTG is completely unshielded. We'll be launching over the ocean, so no one will get killed if it drops. But it does add a minor amount of contamination. So we'll bump the risks to a 30.
100 - (0.25 * 30) = 92.5
Things are still looking good for RTGs.
Hate to break it to you, but your arguments are pathetic. There's little to no risk. Unless you can show a situation where HUMAN BEINGS die (even one), you're going to have a hard time proving your case.
Why can't you just flap the solar panels to try and shake off the excess dust? I mean, maybe you could drive it around in circles in a shallow crater and make everything go wiggly.
Because Sprit doesn't move that fast. The rover is programmed to move 20 cm at a time before stopping to recheck its bearings. Even if they could override it, the scientists wouldn't want to take the chance of flipping or damaging the rover. If the rover gets in a tight spot, there's nobody there to flip it back over.
As for scientists wanting more stuff, they always want more stuff.:) But they usually aren't the ones that have to pay for it, beyond finding someone to give them a bigger grant (which is non-trivial, granted).
True, but this is a rather sensical addition. You're spending $400 million on a probe. Doesn't it make sense to try and get the longest life out of it possible? And the weight of the RTG wouldn't be much different from all the solar panels and batteries the thing is carrying now.
The plain and simple truth is that NASA avoids anything even remotely nuclear whenever possible. While one can't blame them since they need public support, it does tend to stop any technological progress.
Did you know that "destroys the entire earth" is a hyperbole to show that even minimal odds of great consequence can equal great risk?
Let me rephrase for you. There is a zero point zero zero zero chance that an RTG will destroy the earth, or even cause more damage than your gas tank exploding. Actually, zero point zero zero is rounding a bit. If you were willing to add a few billion more zeros, the uncertainty principle would say that the possibility exists of your plutonium (or gas tank for that matter) could start a super-massive blackhole that would suck in the earth, moon, and sun.
Hmmm... Okay, you can run and scream about the dangers of a super-massive blackhole now. While you're at it, warn people that the food they eat might be putting out minor amounts of radiation. Or that their backyard is full of the same materials used in nuclear weapons. Even better, warn the world about the dangers of Dihydrogen Monoxide. That shit is dangerous.:-P
Did you know that tons of uranium burn up in the atmosphere each year? A large portion of meteorites have uranium content. As for plutonium's toxicity, it's no more toxic than the stuff in your LiON or NiCad battery. You deal with chemicals every day that could kill you if inhaled or ingested (the later of which is not a danger with plutonium).
Still, rockets contain all kinds of poisons. That's why NASA launches them over the ocean. In the case of a rocket failure, just about every component in the craft is doing more ecological damage than the RTG which is safely stored in a black box.
And while we're at it, let's discuss the consequences as well. A one-in-a-million chance is small, but if it destroys the entire earth, it's probably too risky to offset almost any benefit.
*cough* *choke* *gag*
I can't believe I've got another one of you people. We're not even talking about a nuclear pile/reactor! We're talking about stuff similar to what's in your BACKYARD!
Did you know that plutonium gives off Alpha radiation?
Did you know that Alpha radiation is not in any way shape or form dangerous unless lodged inside your body?
Did you know that Alpha radiation can be shielded by a sheet of paper?
Did you know that dead skin cells are thicker than a sheet of paper?
Did you know that plutonium can burn?
Did you know that when plutonium burns, it forms Plutonium Oxide?
Did you know that Plutonium burning is no more dangerous than magnesium burning? In fact the results are very similar.
Did you know that you have been brainwashed into thinking that nuclear power can destroy the world?
Did you know that if every Hydrogen, Neutron, and Atomic bomb were detonated, it wouldn't even penetrate the earth's crust?
Did you know that nuclear reactors exist that put out only about 6 MegaWatts? In comparison, the smallest coal plants puts out about 30 megawatts.
Did you know that the laws of physics say that 6 megawatts of destructive force is the same whether it's 6 megawatts of coal, nuclear, oil, or dynamite power?
Did you know that more radiation is put out by a single coal burning plant than all the nuclear plants in the US? (Coal contains uranium)
Did you know that the average home consumes about 13 megawatts hours of power per year?
Did you know that Chernobyl has 4 nuclear reactors, three of which continued to operate after the disaster?
Did you know that Russia TRIED to get Chernobyl to blow in order to perform safety tests?
Did you know that only 40 people on site died in Chernobyl?
Did you know that Chernobyl was a stolen US design that was decommissioned in favor of safer designs?
Did you know that Russia did very little to clean up the waste that was expelled and as a result killed about 200 more people through inaction?
Don't take the environmentalists at face value. Do some research for yourself. Oh, and the odds of the RTG not surviving are about the same as the black box in an airplane not surviving.
That's probably because I keep bringing them up.;-)
More seriously, it's because of the renewed interest in space. Serious space exploration requires energy. The only way to get that much energy is nuclear. All other solutions consist of stopgap solutions such as firing rockets like ballistic missiles and hoping they *eventually* hit the target and pointing solar cells at the sun to get power. The problems with both of these solutions are numerous and well known. The problems with nuclear solutions are simply irrational fears.
I was thinking something like an auto-oxider. You know, get a little of the fuel to mix and it will self ignite and blow the whole thing to kingdom come. Much more effective way of proving my point than giving him a more inert fuel.:-)
Um, since when is the ocean void of life? (i.e. "unpopulated") Oh, I get it. You value human life more than any other.
Now that you mention it, yes I do. If I have to choose between saving a human's life and saving an animal, it will be the human. That's not to say that I won't save an animal if possible.
As for RTGs, they won't hurt anything in the water. The RTGs we've retrieved from failed launches were intact and did not contaminate the area. One that was retrieved was in such good shape that it was actually reused on a future mission.
BTW, even if the RTG were released, it wouldn't affect the surrounding life to any significant degree. i.e. The underwater volcanos spew more radioactive material than the few solid pound of plutonium in an RTG.
That is pretty impressive if it turns out to be true.
It is. In fact, the US has only burned up one RTG and it was intentional. Russia is responsible for most of the contamination brought about by RTGs. Still, not a single death has yet been linked with Russia's carelessness.
But I suppose skeptics will say that just because past explosions have not exposed it does not mean that future explosions won't either.
What can you do? Skeptics won't accept anything but zero risk. And zero risk is simply impossible. There's risk I could trip and break my neck. Therefore we should have safer dirt! *sigh*
Nasa understandably just does not want to deal with the politics of radiation if there are "close enough" alternatives.
Unfortunately, there is no "close enough" substitute for nuclear power solutions. Solar panels are only effective as far out as Mars. Beyond that, they are useless. They also don't produce a steady stream of power like RTGs do and are sensitive to the weather.
And if we want to bring launch solutions into this discussion, there's no current launch solution that can get anywhere close to a 6 million pound rocket with 2 million pounds of cargo. Even the Space Shuttle, with its massive lifting power, has to operate within barely acceptable safety limits to meet the weight requirements of liftoff.
What's REALLY interesting is if you look at the ISP of various rockets:
and there is a small chance that one could burst from launch errors...
The odds that one would burst are about as close to zero as they get. The RTG itself is sealed inside a "black box" type of shielding. The stuff is strong enough to survive reentry from orbit! An explosion of the rocket wouldn't even phase it (as past launch failures have shown).
...end up polluting a populated area.
Actually, that's why NASA launches over the ocean. If something does fail, it falls into an unpopulated area (i.e. miles of water).
I agree that the risk is tiny, but it does exist.
You have a greater chance of getting cancer from your cell phone battery.
Noboby sane claims they explode into mushroom clouds.
You'll love this guy. He still hasn't taken me up on my "nuclear challenge". I wonder why?;-)
And, "nuke" power cells are not politically popular due to possible launch crash risks.
While I generally agree with the rest of what you say, please don't call RTGs "nukes". They're simply heavy metals that emit some radiation and really don't post a threat to anyone. Heck, you've probably got similar materials in your backyard. But we're *never* going to convince people otherwise if we don't stop calling them "nukes".
Wild-ass guess, but the wiper mechanism would probably get jammed by dust just about the time if could be useful in cleaning off the solar cells.
Seriously, even the scientists on the project wanted an RTG in the thing. They could have driven it around for *years* if they had. Instead, they got solar panels which (due to dust) have an expected lifetime of about 1/2 a year. Stupid environmentalism...
Also, the plutonium doesn't have to be inside you, you just need to be exposed to the gamma radiation released from it to give you cancer.
External plutonium particles are not a serious source of gamma radiation. Unless you're standing directly on top of a reasonably large chunk of plutonium, you're unlikely to get any higher dosage than you would from cosmic gamma rays or building materials such as granite.
However, just because meteriods that release radioactive material into the atmosphere are naturally occuring doesn't mean they are harmless. Natural sources of radiation can give you cancer just as easy as man-made ones
What's your point? Radiation is a fact of life. You're exposed to plenty of it just by living. The trick is that your body is capable of repairing the damage caused by minor amounts of it (up to 100 REMs IIRC). Beyond that threshold, the radiation begins to damage more than your body can detect and repair. Thus cancerous cells may set in. Still, you'd have a hard time getting more than 100 REMs even from 10 pounds of unshielded plutonium. The radiation falls off at the same rate as light (dosage is inversely proportional to the distance).
Another interesting property is that standard building materials appear to be quite good at containing radiation. So much so, that homes and apartments exist where the radiation present inside is *significantly higher* than radiation present outside. A relative of mine actually has an apartment like this in Russia. There are also well known Uranium deposits here in the US that we built cities on top of. (Oops.) Many homes in those areas exhibit this sort of behavior. In fact, your own backyard probably has a nice deposit of Uranium.
I understood that plutonium and other fissile materials give off neutrons as well, which makes other chemical elements turn into radioactive isotopes.
Only when they fission. Plutonium and other radioisotopes do tend to spontaneously fission. But it isn't very often, and there is very few (count 'em on one hand) neutrons released. You'd have to build a nuclear pile with a proper moderator for slowing neutrons to get any serious amount of neutron radiation going. Overall, you probably won't get a higher dose of neutron radiation from plutonium than you would from the uranium in your backyard.
How do you know? Of all the people that have contracted cancer how do you know which one's were cause by radiation from plutonium, or by-products?
The only "by-products" of radioisotopes are stable metals of a lower element number. These are all over the place and won't affect you any more than the hundreds of thousands of batteries disposed every year. As for the radioactive plutonium itself, this stuff is EXTREMELY radioactive. You can get cancer from a small particle embedded in your system. However, that small particle still puts out enough radiation to be detectable on a geiger counter or medical tracing equipment.
In other words, we would have heard of at least one instance where someone got cancer and they found it was due to plutonium.
Meteriods are made of "light" elements, such as iron.
A wise man once said, "'Tis better to be silent and be thought a fool, than to open one's mouth and remove all doubt."
Solomon, if I remember correctly. From Proverbs (one of my favorite books). In fact, Solomon also states, "Yea, if thou criest after knowledge, and liftest up thy voice for understanding;... Then shalt thou understand the fear of the LORD, and find the knowledge of God."
I have done quite a bit of research into the subject of Nuclear Physics. Unfortunately, I'm only human and I *will* make mistakes. But I do my best to learn from those mistakes and gain new knowledge.
"It is as sport to a fool to do mischief: but a man of understanding hath wisdom."
DAMN STRAIGHT! We already know the thing is safe and that it can fly. Why do we have to convince the tree huggers? Build the thing and launch it. We can ask for forgiveness later (when there's nothing they can do about it).
Because you can hit a black-box recorder with your shoe for hours, and it won't explode and take the whole state with you.
How do you people come up with this stuff? "Explode and take the whole state with you"? From kicking it with your SHOE? You'll have to forgive me, but I can't believe ANYONE would make that statement!
Ok, Nuclear Physics 101. First and foremost: Fissionable materials are not inherently unstable. In fact, Uranium and Radon are naturally occurring substances that a lot of people live on top of. Now you get a "nuclear pile" when you put a lot of material together. The nuclear material spontaneously fissions on occasion (no, I'm not making this up) producing fast moving and slow moving neutrons. The slow moving neutrons will tend to hit other atoms. If a hit occurs just right, it will cause other material to fission. Heavy materials work best for this as their sheer mass makes them easier to crack.
BTW, there isn't usually enough slow neutrons to produce a nuclear "critical" reaction (i.e. produce any amount of power or heat). Water is usually used to slow down fast neutrons and produce more fissions. With enough fissions, a reactor can get a stable "critical" reaction going. Today's reactors are built to evaporate the water if the reaction gets too hot. Thus a melt-down stops itself. Older reactors kept everything under pressure, so if the reaction got out of hand, you'd end up with a BOILER EXPLOSION. That's right, let me repeat myself, a BOILER EXPLOSION. Those aren't great, but they hardly take out a large area.
As an example, Chernobyl killed 40 people on site. That's it. The remaining 3 reactors at Chernobyl kept running for decades. (Which they shouldn't have, but that's another problem.)
Now, a nuclear bomb is carefully designed to produce what's called a "super-critical" reaction. A super-critical reaction is only obtainable by very careful manipulation of the fissibles. Atomic bombs have shaped charges that force all the neutrons inward and (hopefully) cause most of the material to fission all at once. That produces enough force to take out about a city. For a really BIG explosion, special reflectors and materials are used. First an atomic blast is contained within a tiny bomb. Nearly all the energy is reflected inward by a uranium shell. That much force in a confined space (at a temperature about as hot as the Sun) then forces hydrogen atoms together into a material we call Tritium. The result of this is much more energy than the original blast. Enough to take out a small state or country.
Now, let's take the nuclear challenge. I'll give you a black box of rocket fuel to kick around. I'll take a black box nuclear reactor to kick around. Whoever survives the longest wins. Want to take me up on it?
I notice that you omit to mention the SNAP satellite that *didn't* have a safe RTG - it burned up, releasing it's plutonium into the atmosphere
That's because it was designed to do that. Early thinking was that the plutonium could be burned in the atmosphere with no major ecological effects. (Considering the number of radioactive meteors that burn up, they were probably right.) Later on there was a push for "safe" radioisotopes that wouldn't "pollute" the eco-system. So NASA changed the design to make them indestructible. As for Communist Russia, they really didn't care who got killed or hurt. Thus the incident where they burned up a bunch of plutonium over Canada. Still, no one died there either.
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NASA has been launching SRGs for some time now.
PSSST... I think you meant to say "NASA has been launching RTGs for some time now". SRGs are a newer and more efficient design that have shown promise, but could cause errors in instrumentation due to slight vibrations. SRGs have not yet flown.
Probably the main reason NASA went solar instead of nuclear on this mission was weight.
RTGs get ~75W per 2.5 pounds of plutonium. Considering how heavy the batteries are that the rover is carrying, I seriously doubt that weight was the deciding factor.
Do they launch it over a section of the ocean that's devoid of tide and current?
Hardly. NASA wants those RTGs back so they can reuse them on the next mission!
Actually, the black box would be too heavy to be carried by tides. It sinks to the bottom instead. Pretty normal for materials with atomic numbers above 90.
You prove my point again. What benefit? The Sojourner is a test rover with very minimal capabilities. Why keep it running for years?
You're having a really tough time her, aren't you? The benefit is having a functional and transmitting device on Mars for the years between Mars missions. The risks are that a black box could fall into the ocean and a diver would have to pick it up later. Now, let's do your equation.
We'll set the odds of a failed launch at about 1 in 4 or 0.25. The consequences are some inconvenience, so we'll set it to 5. The benefits are a robot that will keep running for as long as we want to pay attention to it. We'll assign that as 100.
100 - (0.25 * 5) = 98.75
That looks like a good equation to me. Let's say that the RTG is completely unshielded. We'll be launching over the ocean, so no one will get killed if it drops. But it does add a minor amount of contamination. So we'll bump the risks to a 30.
100 - (0.25 * 30) = 92.5
Things are still looking good for RTGs.
Hate to break it to you, but your arguments are pathetic. There's little to no risk. Unless you can show a situation where HUMAN BEINGS die (even one), you're going to have a hard time proving your case.
Why can't you just flap the solar panels to try and shake off the excess dust? I mean, maybe you could drive it around in circles in a shallow crater and make everything go wiggly.
:) But they usually aren't the ones that have to pay for it, beyond finding someone to give them a bigger grant (which is non-trivial, granted).
Because Sprit doesn't move that fast. The rover is programmed to move 20 cm at a time before stopping to recheck its bearings. Even if they could override it, the scientists wouldn't want to take the chance of flipping or damaging the rover. If the rover gets in a tight spot, there's nobody there to flip it back over.
As for scientists wanting more stuff, they always want more stuff.
True, but this is a rather sensical addition. You're spending $400 million on a probe. Doesn't it make sense to try and get the longest life out of it possible? And the weight of the RTG wouldn't be much different from all the solar panels and batteries the thing is carrying now.
The plain and simple truth is that NASA avoids anything even remotely nuclear whenever possible. While one can't blame them since they need public support, it does tend to stop any technological progress.
Did you know that "destroys the entire earth" is a hyperbole to show that even minimal odds of great consequence can equal great risk?
:-P
Let me rephrase for you. There is a zero point zero zero zero chance that an RTG will destroy the earth, or even cause more damage than your gas tank exploding. Actually, zero point zero zero is rounding a bit. If you were willing to add a few billion more zeros, the uncertainty principle would say that the possibility exists of your plutonium (or gas tank for that matter) could start a super-massive blackhole that would suck in the earth, moon, and sun.
Hmmm... Okay, you can run and scream about the dangers of a super-massive blackhole now. While you're at it, warn people that the food they eat might be putting out minor amounts of radiation. Or that their backyard is full of the same materials used in nuclear weapons. Even better, warn the world about the dangers of Dihydrogen Monoxide. That shit is dangerous.
BTW, your name isn't Alex is it? Same ICQ handle?
Never mind. Your journal states you're married. The guy I knew wasn't married and has very little chances of doing so until he grows up.
Did you know that tons of uranium burn up in the atmosphere each year? A large portion of meteorites have uranium content. As for plutonium's toxicity, it's no more toxic than the stuff in your LiON or NiCad battery. You deal with chemicals every day that could kill you if inhaled or ingested (the later of which is not a danger with plutonium).
Still, rockets contain all kinds of poisons. That's why NASA launches them over the ocean. In the case of a rocket failure, just about every component in the craft is doing more ecological damage than the RTG which is safely stored in a black box.
BTW, your name isn't Alex is it? Same ICQ handle?
And while we're at it, let's discuss the consequences as well. A one-in-a-million chance is small, but if it destroys the entire earth, it's probably too risky to offset almost any benefit.
*cough* *choke* *gag*
I can't believe I've got another one of you people. We're not even talking about a nuclear pile/reactor! We're talking about stuff similar to what's in your BACKYARD!
Did you know that plutonium gives off Alpha radiation?
Did you know that Alpha radiation is not in any way shape or form dangerous unless lodged inside your body?
Did you know that Alpha radiation can be shielded by a sheet of paper?
Did you know that dead skin cells are thicker than a sheet of paper?
Did you know that plutonium can burn?
Did you know that when plutonium burns, it forms Plutonium Oxide?
Did you know that Plutonium burning is no more dangerous than magnesium burning? In fact the results are very similar.
Did you know that you have been brainwashed into thinking that nuclear power can destroy the world?
Did you know that if every Hydrogen, Neutron, and Atomic bomb were detonated, it wouldn't even penetrate the earth's crust?
Did you know that nuclear reactors exist that put out only about 6 MegaWatts? In comparison, the smallest coal plants puts out about 30 megawatts.
Did you know that the laws of physics say that 6 megawatts of destructive force is the same whether it's 6 megawatts of coal, nuclear, oil, or dynamite power?
Did you know that more radiation is put out by a single coal burning plant than all the nuclear plants in the US? (Coal contains uranium)
Did you know that the average home consumes about 13 megawatts hours of power per year?
Did you know that Chernobyl has 4 nuclear reactors, three of which continued to operate after the disaster?
Did you know that Russia TRIED to get Chernobyl to blow in order to perform safety tests?
Did you know that only 40 people on site died in Chernobyl?
Did you know that Chernobyl was a stolen US design that was decommissioned in favor of safer designs?
Did you know that Russia did very little to clean up the waste that was expelled and as a result killed about 200 more people through inaction?
Don't take the environmentalists at face value. Do some research for yourself. Oh, and the odds of the RTG not surviving are about the same as the black box in an airplane not surviving.
RTG's have been coming up alot on here lately
;-)
That's probably because I keep bringing them up.
More seriously, it's because of the renewed interest in space. Serious space exploration requires energy. The only way to get that much energy is nuclear. All other solutions consist of stopgap solutions such as firing rockets like ballistic missiles and hoping they *eventually* hit the target and pointing solar cells at the sun to get power. The problems with both of these solutions are numerous and well known. The problems with nuclear solutions are simply irrational fears.
What risk?
RTGs are as safe as any other rocket system. If I were you, I'd be more worried about all the chemicals used in the construction of the craft.
I was thinking something like an auto-oxider. You know, get a little of the fuel to mix and it will self ignite and blow the whole thing to kingdom come. Much more effective way of proving my point than giving him a more inert fuel. :-)
Um, since when is the ocean void of life? (i.e. "unpopulated") Oh, I get it. You value human life more than any other.
Now that you mention it, yes I do. If I have to choose between saving a human's life and saving an animal, it will be the human. That's not to say that I won't save an animal if possible.
As for RTGs, they won't hurt anything in the water. The RTGs we've retrieved from failed launches were intact and did not contaminate the area. One that was retrieved was in such good shape that it was actually reused on a future mission.
BTW, even if the RTG were released, it wouldn't affect the surrounding life to any significant degree. i.e. The underwater volcanos spew more radioactive material than the few solid pound of plutonium in an RTG.
That is pretty impressive if it turns out to be true.
It is. In fact, the US has only burned up one RTG and it was intentional. Russia is responsible for most of the contamination brought about by RTGs. Still, not a single death has yet been linked with Russia's carelessness.
But I suppose skeptics will say that just because past explosions have not exposed it does not mean that future explosions won't either.
What can you do? Skeptics won't accept anything but zero risk. And zero risk is simply impossible. There's risk I could trip and break my neck. Therefore we should have safer dirt! *sigh*
Nasa understandably just does not want to deal with the politics of radiation if there are "close enough" alternatives.
Unfortunately, there is no "close enough" substitute for nuclear power solutions. Solar panels are only effective as far out as Mars. Beyond that, they are useless. They also don't produce a steady stream of power like RTGs do and are sensitive to the weather.
And if we want to bring launch solutions into this discussion, there's no current launch solution that can get anywhere close to a 6 million pound rocket with 2 million pounds of cargo. Even the Space Shuttle, with its massive lifting power, has to operate within barely acceptable safety limits to meet the weight requirements of liftoff.
What's REALLY interesting is if you look at the ISP of various rockets:
Space Shuttle Boosters: ~250 ISP
Saturn V: ~450 ISP
Nuclear GCNR Rockets: 3000-5000 ISP
Wikipedia has more info.
Well, they *are* radio-active
...end up polluting a populated area.
;-)
But safe enough to hold with gloves...
and there is a small chance that one could burst from launch errors...
The odds that one would burst are about as close to zero as they get. The RTG itself is sealed inside a "black box" type of shielding. The stuff is strong enough to survive reentry from orbit! An explosion of the rocket wouldn't even phase it (as past launch failures have shown).
Actually, that's why NASA launches over the ocean. If something does fail, it falls into an unpopulated area (i.e. miles of water).
I agree that the risk is tiny, but it does exist.
You have a greater chance of getting cancer from your cell phone battery.
Noboby sane claims they explode into mushroom clouds.
You'll love this guy. He still hasn't taken me up on my "nuclear challenge". I wonder why?
And, "nuke" power cells are not politically popular due to possible launch crash risks.
While I generally agree with the rest of what you say, please don't call RTGs "nukes". They're simply heavy metals that emit some radiation and really don't post a threat to anyone. Heck, you've probably got similar materials in your backyard. But we're *never* going to convince people otherwise if we don't stop calling them "nukes".
Dumb question, why no wiper blades?
Wild-ass guess, but the wiper mechanism would probably get jammed by dust just about the time if could be useful in cleaning off the solar cells.
Seriously, even the scientists on the project wanted an RTG in the thing. They could have driven it around for *years* if they had. Instead, they got solar panels which (due to dust) have an expected lifetime of about 1/2 a year. Stupid environmentalism...
If they'd used an SRG or RTG they wouldn't have those problems. Solar cells? Bah. Waste of weight.
Also, the plutonium doesn't have to be inside you, you just need to be exposed to the gamma radiation released from it to give you cancer.
External plutonium particles are not a serious source of gamma radiation. Unless you're standing directly on top of a reasonably large chunk of plutonium, you're unlikely to get any higher dosage than you would from cosmic gamma rays or building materials such as granite.
However, just because meteriods that release radioactive material into the atmosphere are naturally occuring doesn't mean they are harmless. Natural sources of radiation can give you cancer just as easy as man-made ones
What's your point? Radiation is a fact of life. You're exposed to plenty of it just by living. The trick is that your body is capable of repairing the damage caused by minor amounts of it (up to 100 REMs IIRC). Beyond that threshold, the radiation begins to damage more than your body can detect and repair. Thus cancerous cells may set in. Still, you'd have a hard time getting more than 100 REMs even from 10 pounds of unshielded plutonium. The radiation falls off at the same rate as light (dosage is inversely proportional to the distance).
Another interesting property is that standard building materials appear to be quite good at containing radiation. So much so, that homes and apartments exist where the radiation present inside is *significantly higher* than radiation present outside. A relative of mine actually has an apartment like this in Russia. There are also well known Uranium deposits here in the US that we built cities on top of. (Oops.) Many homes in those areas exhibit this sort of behavior. In fact, your own backyard probably has a nice deposit of Uranium.
I understood that plutonium and other fissile materials give off neutrons as well, which makes other chemical elements turn into radioactive isotopes.
Only when they fission. Plutonium and other radioisotopes do tend to spontaneously fission. But it isn't very often, and there is very few (count 'em on one hand) neutrons released. You'd have to build a nuclear pile with a proper moderator for slowing neutrons to get any serious amount of neutron radiation going. Overall, you probably won't get a higher dose of neutron radiation from plutonium than you would from the uranium in your backyard.
How do you know? Of all the people that have contracted cancer how do you know which one's were cause by radiation from plutonium, or by-products?
The only "by-products" of radioisotopes are stable metals of a lower element number. These are all over the place and won't affect you any more than the hundreds of thousands of batteries disposed every year. As for the radioactive plutonium itself, this stuff is EXTREMELY radioactive. You can get cancer from a small particle embedded in your system. However, that small particle still puts out enough radiation to be detectable on a geiger counter or medical tracing equipment.
In other words, we would have heard of at least one instance where someone got cancer and they found it was due to plutonium.
Meteriods are made of "light" elements, such as iron.
Whoever told you that was wrong.
All this time has passed, and we still can't think of a more efficient heavy launch vehicle?
Sure we can. It will just get clasified as "evil" by those who oppose high energy. We already have the technology. We just need to use it.
A wise man once said, "'Tis better to be silent and be thought a fool, than to open one's mouth and remove all doubt."
... Then shalt thou understand the fear of the LORD, and find the knowledge of God."
Solomon, if I remember correctly. From Proverbs (one of my favorite books). In fact, Solomon also states, "Yea, if thou criest after knowledge, and liftest up thy voice for understanding;
I have done quite a bit of research into the subject of Nuclear Physics. Unfortunately, I'm only human and I *will* make mistakes. But I do my best to learn from those mistakes and gain new knowledge.
"It is as sport to a fool to do mischief: but a man of understanding hath wisdom."
anybody disturbed that Bush wants to mine the moon?
Ummm... No. How else do you expect people to survive in space? We have to live off the land.
Well sometimes you just have to say "fuck'em."
DAMN STRAIGHT! We already know the thing is safe and that it can fly. Why do we have to convince the tree huggers? Build the thing and launch it. We can ask for forgiveness later (when there's nothing they can do about it).
Because you can hit a black-box recorder with your shoe for hours, and it won't explode and take the whole state with you.
How do you people come up with this stuff? "Explode and take the whole state with you"? From kicking it with your SHOE? You'll have to forgive me, but I can't believe ANYONE would make that statement!
Ok, Nuclear Physics 101. First and foremost: Fissionable materials are not inherently unstable. In fact, Uranium and Radon are naturally occurring substances that a lot of people live on top of. Now you get a "nuclear pile" when you put a lot of material together. The nuclear material spontaneously fissions on occasion (no, I'm not making this up) producing fast moving and slow moving neutrons. The slow moving neutrons will tend to hit other atoms. If a hit occurs just right, it will cause other material to fission. Heavy materials work best for this as their sheer mass makes them easier to crack.
BTW, there isn't usually enough slow neutrons to produce a nuclear "critical" reaction (i.e. produce any amount of power or heat). Water is usually used to slow down fast neutrons and produce more fissions. With enough fissions, a reactor can get a stable "critical" reaction going. Today's reactors are built to evaporate the water if the reaction gets too hot. Thus a melt-down stops itself. Older reactors kept everything under pressure, so if the reaction got out of hand, you'd end up with a BOILER EXPLOSION. That's right, let me repeat myself, a BOILER EXPLOSION. Those aren't great, but they hardly take out a large area.
As an example, Chernobyl killed 40 people on site. That's it. The remaining 3 reactors at Chernobyl kept running for decades. (Which they shouldn't have, but that's another problem.)
Now, a nuclear bomb is carefully designed to produce what's called a "super-critical" reaction. A super-critical reaction is only obtainable by very careful manipulation of the fissibles. Atomic bombs have shaped charges that force all the neutrons inward and (hopefully) cause most of the material to fission all at once. That produces enough force to take out about a city. For a really BIG explosion, special reflectors and materials are used. First an atomic blast is contained within a tiny bomb. Nearly all the energy is reflected inward by a uranium shell. That much force in a confined space (at a temperature about as hot as the Sun) then forces hydrogen atoms together into a material we call Tritium. The result of this is much more energy than the original blast. Enough to take out a small state or country.
Now, let's take the nuclear challenge. I'll give you a black box of rocket fuel to kick around. I'll take a black box nuclear reactor to kick around. Whoever survives the longest wins. Want to take me up on it?
I notice that you omit to mention the SNAP satellite that *didn't* have a safe RTG - it burned up, releasing it's plutonium into the atmosphere
That's because it was designed to do that. Early thinking was that the plutonium could be burned in the atmosphere with no major ecological effects. (Considering the number of radioactive meteors that burn up, they were probably right.) Later on there was a push for "safe" radioisotopes that wouldn't "pollute" the eco-system. So NASA changed the design to make them indestructible. As for Communist Russia, they really didn't care who got killed or hurt. Thus the incident where they burned up a bunch of plutonium over Canada. Still, no one died there either.