Nuclear engine on the other hand is in a state where very high velocity, very high energy mechanical events are going on as the propellant is being transfered and accellerated through it.
Actually, there's very little mechanical effect going on inside the engine. The fuel is pumped by the turbo-pumps and pressured out the other end. In between, it gets heated to a plasma state. The worst case scenario is that the nuclear fuel or plasma loses magnetic containment and melts through the materials of the rocket. There's nowhere in the engine for enough pressure to build up for an explosion.
And since the reactor is already in the melt-down state the hot and very highly radioactive fuel will be just perfect to disperse with maximum impact.
To be precise, it's hot gas/plasma. If fully dispersed, it won't add a significant amount of uranium to the surface of the Earth. In fact, the background radiation levels wouldn't even change. (Coal plants put out more radioactive uranium in one day than exists in the engines.) The most likely design is something along the lines of an engine that would be built so that if containment were lost, the gasses would come in contact with a black box container (say, a depleted uranium shell that itself is surrounded by lead) and would cool before penetrating its container. Once the black box hits water, the gases will have no chance of maintaining a hot enough state to eat through the container.
BTW, take a look for at your current disposition for a moment. You've stopped yelling, stopped complaining about things glowing in the dark, and are finally focused on how to make the engines safe. Persistence changes people's minds more than anything else. (Or maybe I read Green Eggs and Ham to my kids one too many times.);-)
*chuckle* Thanks for that light look at space craft design. I'll try to address the most important ones:
1. As I said before, these Microdrives are surprisingly resilient. Still, the drives should be deactivated and heads parked until takeoff is complete. Certifying that this will work would add expense, but you could pay IBM or an independent firm to do this. Worst case, you can switch back to "proven" Compact Flash without any major impact on development (same form factor). The only downside is that you may have less disk than you had hoped for.
2. You're pointing to power concerns. As I said, 10 pounds of plutonium would do it. My solution to handling the environmental whiners is to keep sending up RTGs until they get used to the idea.
3. Shielding in silicon is exactly what I'm *not* looking for in this design. I'm thinking a sealed lead case. Yes, that will add a few kilograms, but not much more. Some weight will also be saved on not using the "hardened" components. Even better would be lead layered with some of that new plastic shielding. That would help reduce the weight.
4. Don't be looking for new uses for the extra computing and storage power. The point of overspecing the machine is so that errors like the one on Spirit don't happen. It also allows for defective areas of the hardware to be turned off without impacting the overall power of the machine.
5. Part of my point was that QNX would have been a better choice from the get-go. VxWorks is not what I would tend to think of as my first choice for such a mission. My idea is to make a cheap machine that tolerates failure. "Cheaper, better, faster." After all, that's the thinking of computer languages like Java. Very simply, "Software and hardware are too complex. Thus software should adapt against failure instead of trying to eliminate all failure during development." Besides, NASA bought or used the built-in solution for most of the drivers they used. No reason why you can't buy similar drivers for QNX.
6. I figure my design would add probably about 60 pounds to the design. I'm not a rocket scientist, but I think that can be accounted for when fueling the rocket.
7. I'm not looking to prove these components to the same degree that previous missions have. "Cheaper, better, faster", remember? When 90% of your cost is certifying your parts for situations that may never happen, how is that cheaper or faster? Thus you're stuck with underspeced hardware that proved itself before the general populace even used the Internet. How is that better?
8. RTGs are heaters unto themselves. Also, the processor will provide a certain amount of heat. Since it's sealed in its radiation hardened case along with the microdrive, the heat will actually build up. Thankfully, we decided to use lead (or at least some lead) which will act as a cooling surface. Thus the inside of the case will stay warm during operation.
I'm not saying that I'm way better than NASA at this, but I do have a bit of a different viewpoint than they do. Perhaps my ideas wouldn't work. Or maybe they would. Either way, it's not a bad choice for investigation. NASA has to be looking to develop technologies that will allow an eventual colony in space. One way to help that happen is if we can look at ways of making off the shelf components workable in space.
Anyone see that AOL optimized commercial that was crossed with American Chopper? There was an AOL optimizer sitting on one of their benches that was putting out a loud throbbing noise. (Looked a lot like the TNG warp core.) The big guy with the handle bar mustache was shouting something at the guys, but no one could hear it. Cracked me up.:-)
I want a 400 watt RTG to power my computer! Completely silent, and doesn't need to be plugged in! So, It gets a little hot. Who cares if the cat gets burned for sitting on my computer? Serves her right. Just got to keep it secret from the feds! They don't seem to like the idea of consumers and plutonium. (Go figure)
I do that as well. Usually I tell people that the whole thing would be engineered like RTGs. A couple of RTGs have dropped into the ocean, all intact. One was even reused. I explain how modern reactors can't blow up. I even explain how a nuclear engine is already in melt-down mode so it can't possibly enter a "prompt-critical" stage.
It's when some people get pushier (as with yourself) that I have to explain that it isn't as dangerous as they think. You'd be surprised how many people say, "But let's assume the one in a billion trillion chance that the RTG container fails". I even had one guy claim that a failed RTG would destroy the entire planet! He quickly backed off saying that it was a hyperbole for his argument. Suffice it to say, he got skewered by many more people than myself. And some weren't as nice as I am.
I'm sure an asteroid that was pelted by the exhaust from a nuke rocket would have very detectable levels of those isotopes.
*Groan* Uranium is COMMON in asteroids. My engines would use no more than a few tens of pounds of uranium. Worst case, we'll say it uses a few hundred pounds. How is the particulate matter being exhausted by my engines anywhere near the TONS of uranium contained in many asteroids? In fact, most Uranium on Earth is from the tons that burn up in the atmosphere every year.
As for point #4, you do change things by existing, but you can try to be intelligent about HOW you change things. If I lived on an island with only 20 coconut trees I would not burn them for light and warmth. I'd burn any other wood I could find even if it was inferior to palm trees.
But if you lived on an island with hundreds of thousands of palm trees, would you really feel bad about burning a few for a fire? Remember, a ship will burn/expel *pounds* of uranium. (Much of which will be some other substance after use.) How does that compare to the BILLIONS OF TONS in the solar system?
Also, natural uranium fires probably didn't spew crap into the air like a nuke blast, most of what was burning probably stayed in the ground.
The "crap spewed" doesn't stay in the air very long. Uranium is too heavy. Carbon dating was messed up from radiation pulses. Nothing more, nothing less. I'm sorry that makes life harder for geologists, but that's an unfortunate part of life. How many archeological digs were made harder by robbers, tourists, curious natives, etc, who had all previously wandered the area? It's a fact of life. Space geologists are going to have to get used to the fact that engines will alter things slightly. Possibly, many of them won't care since it's so little. The ones who do, will have to figure out how to work around it.
And that is why I'm out here posting. Joe and Jane Public think "atomic blast, radiation, and mutants that glow in the dark" when they hear the word "nuclear". I'm trying to change that. Slashdot may not be the best place to start, but it does address a large number of intelligent people who work in fields other than nuclear physics. And on occasion, a physicist or two will drop by to help. If I can change middle-class thinking, than the thinking of extremists won't matter.
Way to make your case. You linked to an article with the following conclusion:
In its review of studies conducted both in areas close to the accident and those further away, UNSCEAR (2000) concluded that no increase in adverse pregnancy outcome could be linked to radiation exposures from the Chernobyl accident.
Next time try reading farther than the setup of the article.
I happen to have a link of my own. Chernobyl wasn't the prettiest picture, but it wasn't as bad as many claim or would like to think. Most people want to project the horror of a nuclear blast on Chernobyl. That's just ridiculous. Chernobyl was no worse than any other industrial accident. Chemical spills here in the US have done more damage and killed more people than that!
Oh, and the evacuation and topsoil removal were safety precautions. The study I linked to points out that Norway has a higher natural background radiation level than Chernobyl does today.
What are you going to do, haul it over there in tankers?
Something like that, yeah. Any colonization effort would have to get some supplies from Earth (at least initially). Most plans call for a small fleet of automated cargo ships. Later on, nitrates could possibly be mined from asteroids.
There is no way to distinguish a natural U235 atom from one emmitted by a nuclear rocket. They are precisely identical.
1. It simply isn't enough to make a difference to the ecology of the solar system. (It takes DAYS for light from the sun to reach the outer parts of the solar system.)
2. Some engines don't even emit Uranium. Most of the engines currently developed fall into this category.
3. Radioisotopes can be tracked by the engine exhaust vectors. Any minute amounts in the exhaust vector can be discounted.
4. You're changing things by existing. Are we supposed to stop breathing because we're having a butterfly effect on the weather? Scientists are going to have to sort things out as best as they can.
You do know how plentiful Carbon 14 is on earth don't you? But the amount relative to Carbon 12 is what is important for dating which is why when the amount changes you can no longer use the radioactive decay rate of Carbon 14 to date things.
That has ZERO to do with space engines. The extra radiation pulses from nuclear blasts increased the rate of decay due to spontaneous fission. As a result, an already highly inaccurate and unstable dating method was made that much more inaccurate. It's not like the prehistoric uranium fission fires screwed that up at all. Nooo.
So, if a little bitty nuclear explosion screws up carbon dating inside the radiation belts, who in the world would try to use it in space, where every solar flare changes the rate of decay?!
A hi-altitude explosion over the ocean + wind from the east... Seriously, if something goes wrong with that thing, the point of greatest stress, and thus the most likely source of a catastrofic failure with something like a nuclear engine is at the very core of the reactor!. So we are talking a spectactular hi-altitude BOOM with lots and lots of fine radio-active particles and nice glo-clowd with fallout marching in unpredictable weather controlled direction.
You watch way too much Sci-Fi. A Nuclear engine can't go "boom". Some older style reactors could because they were under pressure (a boiler explosion). A GCNR rocket is already melted (actually gaseous) so it can't melt down and it's designed to exhaust the various gasses that are kept under pressure (otherwise it wouldn't go anywhere). The worst case from the engine is that containment is breeched and the back of the rocket melts off.
Even if you try to launch with wind blowing east, these things can float for days as the Chernobyl excercise proved conclusively.
No, it hasn't. Winds did carry some of the radioisotopes, but the largest problem was not radiation, or people breathing the stuff. The biggest problem was radioactive iodine in the well water. The radio-iodine replaced the normal iodine in newborns. About 14 people have died from thyroid cancer to date (thats all the post Chernobyl deaths BTW), the rest were treated. Thankfully, this problem doesn't occur anywhere else. In the US, we've been fortifying our salt with iodine for 50+ years to prevent this very problem. If you have enough normal iodine in your system, your body will ignore the radioactive stuff.
BTW, Hiroshima and Nagasaki are not glowing in the dark right now. In fact, they were rebuilt shortly after they were bombed. I understand your name is "IgnoramusMaximus", but a little research would go a long way toward learning about how little damage nuclear power has actually done.
It looks like it's basically a large plotter. This is the simplest form of printer, except that pens or wax is traditionally used instead of spray cans.
It's not putting out Uranuim, Thorium, Plutonium or other heavy elements.
You do know how plentiful those are in our solar system, don't you? We have entire asteroids made of the stuff. Anything exhausted by nuclear rockets would be much "hotter" and easy to identify. Not to mention that there wouldn't be much of it. Some engines (e.g. GCNR) don't even exhaust any of those radioisotopes.
Surprisingly, no. From everything I've heard about these drives so far, making them smaller has made them more reliable. It seems that they're able to take quite a bit of shock. At least as much as a normal flash drive.
Of course, triple redundant drives (notice that's the only component I went triple redundant on) would allow you to switch off any that were damaged.
Yes 5 pounds of plutonium exploded over Florida would be more likely to kill thousands than millions, but so did 9/11, and you see what big a deal that was.
Actually, it would be likely to kill far fewer. Plutonium doesn't float very well. Even Chernobyl has so far claimed only 14 lives from thyroid cancer (radioactive Iodine). Plutonium was not one of the biggest concerns. Oh, and a simple explosion isn't enough force to aerosolize plutonium. Russia even burned up some plutonium over Canada and the smallest piece was the size of a grain of sand. Granted, I wouldn't want to get hit on the head with it, but breathing it wasn't a problem.
I imagine thetemperatures involved in the rover (both in flight and on the ground) are higher than allowed by IBM microdrives.
I'm going to assume you mean lower, not higher. The operating temperature of micro-drives are 0 to 65C. The non-operating temp is -40 to 65C. Thus we need to keep the drive above freezing during operation. That's not really a problem though. Since I'm talking about a sealed computer case for shielding, the heat from processor operation alone, should keep the device nice and toasty.
Some of the ones I've seen will go higher than 55C, but I haven't yet seen one that can operate below freezing. Nor have I seen one that can be stored below -20C.
Perhaps someone has a link to flash that can operate at extreme temperatures?
I imagine they hired computer engineers for the parts that required computer engineers, and software engineers for the parts that required software engineers. The scientists would be the guys responsible for supplying requirements to the engineering group.
These are not the same software/hardware engineers you find on the open market. Most of them are scientists or the type who work in scientific fields. They address the problem differently than you or I. That's probably a positive thing for space craft design, but for the "cheaper, better, faster" mantra, you need a very different type of engineering.
Considering that you're sitting next to a massive nuclear furnace that's putting out 5 hundred billion times anything even the largest nuclear rocket could put out, I'd say you're full of it.
The sun has already done radiological damage. Deal with it.
As I said, Nitrates would have to be introduced to the soil. I'm still wondering if microbes wouldn't be able to extract nitrates from deeper soils, but we don't yet have a soil analysis that would support that idea.
They hired scientists, not computer engineers. Most scientists have the smarts to learn computer programming and can build off the shelf hardware (there's a big satellite equipment market that makes space-reliable stuff). However, they're not computer professionals. For what they paid for this little rover, I can think of a radiation hardened design with far more redundancy and capacity than they have in the rover.
For example, why didn't they consider IBM micro-drives? Those existed years ago when they started this project. They could have had a RAID array of three of them. Radiation hardening is still a problem, but that could be better solved by shielding the entire core computer instead of bothering with individual components.
Similarly, I would have used two computing units in a cluster. Yes, your specs would have to go up. My preference would have been an ARM processor, half a gig of RAM (possibly two 512 DIMMs per board that will act as redundant memory), a RAID array of 3 micro-drives (a Gig or larger per if I could get it) and redundant I/O ports via ethernet and XBand wireless. The whole rig would run QNX instead of VxWorks.
The only problem with my setup is power. The poor little craft wouldn't have any left to run its engines! No problem! Go for an RTG power source. About 10 pounds of plutonium dioxide should provide more power than the craft will ever need, for longer than the engines will last. Since the computer would be a sealed and shielded unit, it could possibly last as long as the RTG itself. It could keep attempting to collect and transmit data until either all the sensors fail, or the antenna goes.
Do you know how much more that would increase the mass of the space craft?
Yes. Does 6 million pounds sound large enough for you? How about 8 million tons? It's possible to launch 6 million pounds with a GCNR craft. Once in LEO, the same engines can give even better performance (since they don't have to work against air resistance). Orion (this needs quite a bit of development) could give us an 8 million TON craft for space travel. Even if you go with NERVA, you have 2-4 times the thrust of today's engines. GCNR gives you 6-20 times the thrust.
How about the fact that the g forces created when accelerating to approx 20,000 kph would KILL any humans on board? Robot don't have that problem, so they can get there much faster!
Let's say we accelerate at the speed of 5g's. Let's do the math...
Why on Earth (sorry, space) would you want to accelerate at 5Gs? Constant acceleration at 1/4 G would be sufficient to get to Mars in months. No need to light off a firecracker under your ass.
No, nuclear propulsion is NOWHERE NEAR sophisticated enough to do this, why do you think they use HYDROGEN!?
This makes no sense. They use Hydrogen because it's a very common gas, with a lot of energy to expend. GCNR and NERVA can actually use quite a few other types of fuels (e.g. oxygen, xenon, nitrogen, etc.). There's research going on to find which fuel is the most efficient.
The more exotic propulsions don't even bother with hydrogen. Nuclear Salt Rockets use a Uranium salt water solution as propellant. Orion uses atomic bombs. (Okay, so if they used H-Bombs, they would have to use some hydrogen.)
What do you think happens in a rocket? Perfect sailing? You think a reactor will run perfectly fine while it's being shaken around by acceleration and turbulance?
Are we talking launch or space travel? In the former, the reactor is going to have to be built to withstand vibrations. This is nothing new. Carriers and submarines already have to take precautions against the reactors being shaken. In the later, there's no vibration, because there's no turbulence. No air, remember? And the engines are a bit more sophisticated. The gases are heated until they become plasma, then are exhausted out the rear at a high velocity. Most of the plasma will stay in containment, so there really isn't much vibration produced by this method. (I'm assuming GCNR or NERVA. Orion and Nuclear Salt will vibrate plenty, but they have no reactors to speak of.)
SPINNING craft? How much larger do you want them?
I'll take "6 million pounds or larger" for 300, Alex.
With current technology it is NOT POSSIBLE to SAFELY send people to Mars. It'll be done soon enough (10-15 years perhaps) but right now, you are very wrong.
Anyone who's done the research, knows that we have the technology. The greatest thing holding us back, is the fear of nuclear power. There's no other method to produce megawatts of power from tens of pounds of fuel. Nuclear can do it, we just have to embrace it.
We have the engines to make it possible. What more do you want?
Yes, a nuclear engine is more difficult to protect against. However, that's why NASA launches over the ocean. The Space Shuttle already burns all kinds of fuels that are highly toxic to breath. Not to mention the variety of dangerous chemicals used in its construction. The trick is that by launching over the ocean, an engine failure will result in it dropping into an area uninhabited by humans. Once in the ocean, it will either stay in one piece and decay over the next few years to a half-century, or it will get so dispersed as to not cause any significant increase in the background radiation.
Now plutonium as a safe substance to eat? well maybe today, or next month, but that same piece will decay, and the left over bits or new matter will then decay to something else which will give up badass gamma rays after 9 years.
It's "safe" to eat, because your body can't digest it. It just passes through and give you the radioactive shits. My favorite link on the subject is the most infuriating to environmentalists.
There are a lot more ideas for Nuclear powered craft than Orion. NERVA and GCNR engines are Nuclear Thermal Engines. i.e. They heat up gasses such as hydrogen until they reach a plasma state. At that point, the matter is in such an excited state that it is exhausted at high speeds, thus providing thrust.
Nuclear Electric Engines are basically Ion drives powered by a nuclear reactor.
Nuclear Salt Rockets contain a highly fissible Uranium salt solution. It's normally stored within a tank that prevents fission, then is pumped to an exhaust port where it is allowed to fission and produce thrust. This is a little safer than Orion since it deals with a controlled burn like chemical rockets, instead of trying to ride a big ass explosion.
That kind of frightens me, to be perfectly honest. I really think we need to rethink this.
I could just see the early discussions about rockets: "Let me get this straight. You want to burn gunpowder through a hollow tube? And someone's going to ride this thing? That sounds a bit scary to me."
Slashdot poster AKAImBatman has boldly declared that if corn can be grown on Mars, that humans can survive there. No need to research this issue further, lets just start sending cord up there to plant.
My dear Mr. Coward. Research all you want, but corn is probably our best chance for growing food stuffs. Let's take an inventory of what we need:
Power: Check. Nuclear Reactors would work well. Air: Check. Can be cracked from CO2, or cracked from water. Water: Check. We know it exists at both poles, possibly even as a permafrost. Shelter: Check. We can engineer structures or dig caves.
So what do we do about food? Well, we have to grow something. Corn has been shown to be a robust plant that can grow under a variety of conditions. It can be eaten straight, prepared as meal, used as flour for bread, and given to cattle for feed.
So, what do we need to grow corn? Well we need various nutrients in the soil. So far, soil analysis says that Nitrates and Microbes are the missing factors. Both can be introduced to the soil.
Corn needs CO2. No problem there. We just need to keep the corn under a pressurized bubble. An inflatable tarp will do. No need for a fancy dome. Some oxygen will be needed, but we already have ways of providing for that.
So what do you think I'm missing here? Do you think we should grow potatoes first? Or carrots? None of those put an end to the world hunger that existed in the middle ages. Corn did. All the early American settlers lived off of corn. And if it was good enough for them, why can't it be good enough for us?
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Nuclear engine on the other hand is in a state where very high velocity, very high energy mechanical events are going on as the propellant is being transfered and accellerated through it.
;-)
Actually, there's very little mechanical effect going on inside the engine. The fuel is pumped by the turbo-pumps and pressured out the other end. In between, it gets heated to a plasma state. The worst case scenario is that the nuclear fuel or plasma loses magnetic containment and melts through the materials of the rocket. There's nowhere in the engine for enough pressure to build up for an explosion.
And since the reactor is already in the melt-down state the hot and very highly radioactive fuel will be just perfect to disperse with maximum impact.
To be precise, it's hot gas/plasma. If fully dispersed, it won't add a significant amount of uranium to the surface of the Earth. In fact, the background radiation levels wouldn't even change. (Coal plants put out more radioactive uranium in one day than exists in the engines.) The most likely design is something along the lines of an engine that would be built so that if containment were lost, the gasses would come in contact with a black box container (say, a depleted uranium shell that itself is surrounded by lead) and would cool before penetrating its container. Once the black box hits water, the gases will have no chance of maintaining a hot enough state to eat through the container.
BTW, take a look for at your current disposition for a moment. You've stopped yelling, stopped complaining about things glowing in the dark, and are finally focused on how to make the engines safe. Persistence changes people's minds more than anything else. (Or maybe I read Green Eggs and Ham to my kids one too many times.)
*chuckle* Thanks for that light look at space craft design. I'll try to address the most important ones:
1. As I said before, these Microdrives are surprisingly resilient. Still, the drives should be deactivated and heads parked until takeoff is complete. Certifying that this will work would add expense, but you could pay IBM or an independent firm to do this. Worst case, you can switch back to "proven" Compact Flash without any major impact on development (same form factor). The only downside is that you may have less disk than you had hoped for.
2. You're pointing to power concerns. As I said, 10 pounds of plutonium would do it. My solution to handling the environmental whiners is to keep sending up RTGs until they get used to the idea.
3. Shielding in silicon is exactly what I'm *not* looking for in this design. I'm thinking a sealed lead case. Yes, that will add a few kilograms, but not much more. Some weight will also be saved on not using the "hardened" components. Even better would be lead layered with some of that new plastic shielding. That would help reduce the weight.
4. Don't be looking for new uses for the extra computing and storage power. The point of overspecing the machine is so that errors like the one on Spirit don't happen. It also allows for defective areas of the hardware to be turned off without impacting the overall power of the machine.
5. Part of my point was that QNX would have been a better choice from the get-go. VxWorks is not what I would tend to think of as my first choice for such a mission. My idea is to make a cheap machine that tolerates failure. "Cheaper, better, faster." After all, that's the thinking of computer languages like Java. Very simply, "Software and hardware are too complex. Thus software should adapt against failure instead of trying to eliminate all failure during development." Besides, NASA bought or used the built-in solution for most of the drivers they used. No reason why you can't buy similar drivers for QNX.
6. I figure my design would add probably about 60 pounds to the design. I'm not a rocket scientist, but I think that can be accounted for when fueling the rocket.
7. I'm not looking to prove these components to the same degree that previous missions have. "Cheaper, better, faster", remember? When 90% of your cost is certifying your parts for situations that may never happen, how is that cheaper or faster? Thus you're stuck with underspeced hardware that proved itself before the general populace even used the Internet. How is that better?
8. RTGs are heaters unto themselves. Also, the processor will provide a certain amount of heat. Since it's sealed in its radiation hardened case along with the microdrive, the heat will actually build up. Thankfully, we decided to use lead (or at least some lead) which will act as a cooling surface. Thus the inside of the case will stay warm during operation.
I'm not saying that I'm way better than NASA at this, but I do have a bit of a different viewpoint than they do. Perhaps my ideas wouldn't work. Or maybe they would. Either way, it's not a bad choice for investigation. NASA has to be looking to develop technologies that will allow an eventual colony in space. One way to help that happen is if we can look at ways of making off the shelf components workable in space.
Anyone see that AOL optimized commercial that was crossed with American Chopper? There was an AOL optimizer sitting on one of their benches that was putting out a loud throbbing noise. (Looked a lot like the TNG warp core.) The big guy with the handle bar mustache was shouting something at the guys, but no one could hear it. Cracked me up. :-)
I want a 400 watt RTG to power my computer! Completely silent, and doesn't need to be plugged in! So, It gets a little hot. Who cares if the cat gets burned for sitting on my computer? Serves her right. Just got to keep it secret from the feds! They don't seem to like the idea of consumers and plutonium. (Go figure)
I do that as well. Usually I tell people that the whole thing would be engineered like RTGs. A couple of RTGs have dropped into the ocean, all intact. One was even reused. I explain how modern reactors can't blow up. I even explain how a nuclear engine is already in melt-down mode so it can't possibly enter a "prompt-critical" stage.
It's when some people get pushier (as with yourself) that I have to explain that it isn't as dangerous as they think. You'd be surprised how many people say, "But let's assume the one in a billion trillion chance that the RTG container fails". I even had one guy claim that a failed RTG would destroy the entire planet! He quickly backed off saying that it was a hyperbole for his argument. Suffice it to say, he got skewered by many more people than myself. And some weren't as nice as I am.
I'm sure an asteroid that was pelted by the exhaust from a nuke rocket would have very detectable levels of those isotopes.
*Groan* Uranium is COMMON in asteroids. My engines would use no more than a few tens of pounds of uranium. Worst case, we'll say it uses a few hundred pounds. How is the particulate matter being exhausted by my engines anywhere near the TONS of uranium contained in many asteroids? In fact, most Uranium on Earth is from the tons that burn up in the atmosphere every year.
As for point #4, you do change things by existing, but you can try to be intelligent about HOW you change things. If I lived on an island with only 20 coconut trees I would not burn them for light and warmth. I'd burn any other wood I could find even if it was inferior to palm trees.
But if you lived on an island with hundreds of thousands of palm trees, would you really feel bad about burning a few for a fire? Remember, a ship will burn/expel *pounds* of uranium. (Much of which will be some other substance after use.) How does that compare to the BILLIONS OF TONS in the solar system?
Also, natural uranium fires probably didn't spew crap into the air like a nuke blast, most of what was burning probably stayed in the ground.
The "crap spewed" doesn't stay in the air very long. Uranium is too heavy. Carbon dating was messed up from radiation pulses. Nothing more, nothing less. I'm sorry that makes life harder for geologists, but that's an unfortunate part of life. How many archeological digs were made harder by robbers, tourists, curious natives, etc, who had all previously wandered the area? It's a fact of life. Space geologists are going to have to get used to the fact that engines will alter things slightly. Possibly, many of them won't care since it's so little. The ones who do, will have to figure out how to work around it.
And that is why I'm out here posting. Joe and Jane Public think "atomic blast, radiation, and mutants that glow in the dark" when they hear the word "nuclear". I'm trying to change that. Slashdot may not be the best place to start, but it does address a large number of intelligent people who work in fields other than nuclear physics. And on occasion, a physicist or two will drop by to help. If I can change middle-class thinking, than the thinking of extremists won't matter.
Way to make your case. You linked to an article with the following conclusion:
In its review of studies conducted both in areas close to the accident and those further away, UNSCEAR (2000) concluded that no increase in adverse pregnancy outcome could be linked to radiation exposures from the Chernobyl accident.
Next time try reading farther than the setup of the article.
I happen to have a link of my own. Chernobyl wasn't the prettiest picture, but it wasn't as bad as many claim or would like to think. Most people want to project the horror of a nuclear blast on Chernobyl. That's just ridiculous. Chernobyl was no worse than any other industrial accident. Chemical spills here in the US have done more damage and killed more people than that!
Oh, and the evacuation and topsoil removal were safety precautions. The study I linked to points out that Norway has a higher natural background radiation level than Chernobyl does today.
What are you going to do, haul it over there in tankers?
Something like that, yeah. Any colonization effort would have to get some supplies from Earth (at least initially). Most plans call for a small fleet of automated cargo ships. Later on, nitrates could possibly be mined from asteroids.
Um, wouldn't that be why I was talking about a radiation hardened *case* instead of radiation hardened *components*?
* AKAImBatman smacks Anonymous Coward along the backside of his head.
There is no way to distinguish a natural U235 atom from one emmitted by a nuclear rocket. They are precisely identical.
1. It simply isn't enough to make a difference to the ecology of the solar system. (It takes DAYS for light from the sun to reach the outer parts of the solar system.)
2. Some engines don't even emit Uranium. Most of the engines currently developed fall into this category.
3. Radioisotopes can be tracked by the engine exhaust vectors. Any minute amounts in the exhaust vector can be discounted.
4. You're changing things by existing. Are we supposed to stop breathing because we're having a butterfly effect on the weather? Scientists are going to have to sort things out as best as they can.
You do know how plentiful Carbon 14 is on earth don't you? But the amount relative to Carbon 12 is what is important for dating which is why when the amount changes you can no longer use the radioactive decay rate of Carbon 14 to date things.
That has ZERO to do with space engines. The extra radiation pulses from nuclear blasts increased the rate of decay due to spontaneous fission. As a result, an already highly inaccurate and unstable dating method was made that much more inaccurate. It's not like the prehistoric uranium fission fires screwed that up at all. Nooo.
So, if a little bitty nuclear explosion screws up carbon dating inside the radiation belts, who in the world would try to use it in space, where every solar flare changes the rate of decay?!
A hi-altitude explosion over the ocean + wind from the east... Seriously, if something goes wrong with that thing, the point of greatest stress, and thus the most likely source of a catastrofic failure with something like a nuclear engine is at the very core of the reactor!. So we are talking a spectactular hi-altitude BOOM with lots and lots of fine radio-active particles and nice glo-clowd with fallout marching in unpredictable weather controlled direction.
You watch way too much Sci-Fi. A Nuclear engine can't go "boom". Some older style reactors could because they were under pressure (a boiler explosion). A GCNR rocket is already melted (actually gaseous) so it can't melt down and it's designed to exhaust the various gasses that are kept under pressure (otherwise it wouldn't go anywhere). The worst case from the engine is that containment is breeched and the back of the rocket melts off.
Even if you try to launch with wind blowing east, these things can float for days as the Chernobyl excercise proved conclusively.
No, it hasn't. Winds did carry some of the radioisotopes, but the largest problem was not radiation, or people breathing the stuff. The biggest problem was radioactive iodine in the well water. The radio-iodine replaced the normal iodine in newborns. About 14 people have died from thyroid cancer to date (thats all the post Chernobyl deaths BTW), the rest were treated. Thankfully, this problem doesn't occur anywhere else. In the US, we've been fortifying our salt with iodine for 50+ years to prevent this very problem. If you have enough normal iodine in your system, your body will ignore the radioactive stuff.
BTW, Hiroshima and Nagasaki are not glowing in the dark right now. In fact, they were rebuilt shortly after they were bombed. I understand your name is "IgnoramusMaximus", but a little research would go a long way toward learning about how little damage nuclear power has actually done.
It looks like it's basically a large plotter. This is the simplest form of printer, except that pens or wax is traditionally used instead of spray cans.
It's not putting out Uranuim, Thorium, Plutonium or other heavy elements.
You do know how plentiful those are in our solar system, don't you? We have entire asteroids made of the stuff. Anything exhausted by nuclear rockets would be much "hotter" and easy to identify. Not to mention that there wouldn't be much of it. Some engines (e.g. GCNR) don't even exhaust any of those radioisotopes.
SLAM. Bounce, Bounce, Bounce, Bounce, Roll, Bounce, Roll, Roll, Bounce, Roll, Roll, Roll.
Probably too much shock for the drives.
Surprisingly, no. From everything I've heard about these drives so far, making them smaller has made them more reliable. It seems that they're able to take quite a bit of shock. At least as much as a normal flash drive.
Of course, triple redundant drives (notice that's the only component I went triple redundant on) would allow you to switch off any that were damaged.
Yes 5 pounds of plutonium exploded over Florida would be more likely to kill thousands than millions, but so did 9/11, and you see what big a deal that was.
Actually, it would be likely to kill far fewer. Plutonium doesn't float very well. Even Chernobyl has so far claimed only 14 lives from thyroid cancer (radioactive Iodine). Plutonium was not one of the biggest concerns. Oh, and a simple explosion isn't enough force to aerosolize plutonium. Russia even burned up some plutonium over Canada and the smallest piece was the size of a grain of sand. Granted, I wouldn't want to get hit on the head with it, but breathing it wasn't a problem.
I imagine thetemperatures involved in the rover (both in flight and on the ground) are higher than allowed by IBM microdrives.
I'm going to assume you mean lower, not higher. The operating temperature of micro-drives are 0 to 65C. The non-operating temp is -40 to 65C. Thus we need to keep the drive above freezing during operation. That's not really a problem though. Since I'm talking about a sealed computer case for shielding, the heat from processor operation alone, should keep the device nice and toasty.
Microdrive Specs
Looking at standard flash cards, their operating temperature actually seem to be worse. (0 to 55 C)
Example Flash memory
Some of the ones I've seen will go higher than 55C, but I haven't yet seen one that can operate below freezing. Nor have I seen one that can be stored below -20C.
Perhaps someone has a link to flash that can operate at extreme temperatures?
I imagine they hired computer engineers for the parts that required computer engineers, and software engineers for the parts that required software engineers. The scientists would be the guys responsible for supplying requirements to the engineering group.
These are not the same software/hardware engineers you find on the open market. Most of them are scientists or the type who work in scientific fields. They address the problem differently than you or I. That's probably a positive thing for space craft design, but for the "cheaper, better, faster" mantra, you need a very different type of engineering.
Considering that you're sitting next to a massive nuclear furnace that's putting out 5 hundred billion times anything even the largest nuclear rocket could put out, I'd say you're full of it.
The sun has already done radiological damage. Deal with it.
So what do you think I'm missing here?
Nitrogen.
Nitrates == Nitrogen
As I said, Nitrates would have to be introduced to the soil. I'm still wondering if microbes wouldn't be able to extract nitrates from deeper soils, but we don't yet have a soil analysis that would support that idea.
They hired scientists, not computer engineers. Most scientists have the smarts to learn computer programming and can build off the shelf hardware (there's a big satellite equipment market that makes space-reliable stuff). However, they're not computer professionals. For what they paid for this little rover, I can think of a radiation hardened design with far more redundancy and capacity than they have in the rover.
For example, why didn't they consider IBM micro-drives? Those existed years ago when they started this project. They could have had a RAID array of three of them. Radiation hardening is still a problem, but that could be better solved by shielding the entire core computer instead of bothering with individual components.
Similarly, I would have used two computing units in a cluster. Yes, your specs would have to go up. My preference would have been an ARM processor, half a gig of RAM (possibly two 512 DIMMs per board that will act as redundant memory), a RAID array of 3 micro-drives (a Gig or larger per if I could get it) and redundant I/O ports via ethernet and XBand wireless. The whole rig would run QNX instead of VxWorks.
The only problem with my setup is power. The poor little craft wouldn't have any left to run its engines! No problem! Go for an RTG power source. About 10 pounds of plutonium dioxide should provide more power than the craft will ever need, for longer than the engines will last. Since the computer would be a sealed and shielded unit, it could possibly last as long as the RTG itself. It could keep attempting to collect and transmit data until either all the sensors fail, or the antenna goes.
Do you know how much more that would increase the mass of the space craft?
Yes. Does 6 million pounds sound large enough for you? How about 8 million tons? It's possible to launch 6 million pounds with a GCNR craft. Once in LEO, the same engines can give even better performance (since they don't have to work against air resistance). Orion (this needs quite a bit of development) could give us an 8 million TON craft for space travel. Even if you go with NERVA, you have 2-4 times the thrust of today's engines. GCNR gives you 6-20 times the thrust.
How about the fact that the g forces created when accelerating to approx 20,000 kph would KILL any humans on board? Robot don't have that problem, so they can get there much faster!
Let's say we accelerate at the speed of 5g's. Let's do the math...
Why on Earth (sorry, space) would you want to accelerate at 5Gs? Constant acceleration at 1/4 G would be sufficient to get to Mars in months. No need to light off a firecracker under your ass.
No, nuclear propulsion is NOWHERE NEAR sophisticated enough to do this, why do you think they use HYDROGEN!?
This makes no sense. They use Hydrogen because it's a very common gas, with a lot of energy to expend. GCNR and NERVA can actually use quite a few other types of fuels (e.g. oxygen, xenon, nitrogen, etc.). There's research going on to find which fuel is the most efficient.
The more exotic propulsions don't even bother with hydrogen. Nuclear Salt Rockets use a Uranium salt water solution as propellant. Orion uses atomic bombs. (Okay, so if they used H-Bombs, they would have to use some hydrogen.)
What do you think happens in a rocket? Perfect sailing? You think a reactor will run perfectly fine while it's being shaken around by acceleration and turbulance?
Are we talking launch or space travel? In the former, the reactor is going to have to be built to withstand vibrations. This is nothing new. Carriers and submarines already have to take precautions against the reactors being shaken. In the later, there's no vibration, because there's no turbulence. No air, remember? And the engines are a bit more sophisticated. The gases are heated until they become plasma, then are exhausted out the rear at a high velocity. Most of the plasma will stay in containment, so there really isn't much vibration produced by this method.
(I'm assuming GCNR or NERVA. Orion and Nuclear Salt will vibrate plenty, but they have no reactors to speak of.)
SPINNING craft? How much larger do you want them?
I'll take "6 million pounds or larger" for 300, Alex.
With current technology it is NOT POSSIBLE to SAFELY send people to Mars. It'll be done soon enough (10-15 years perhaps) but right now, you are very wrong.
Anyone who's done the research, knows that we have the technology. The greatest thing holding us back, is the fear of nuclear power. There's no other method to produce megawatts of power from tens of pounds of fuel. Nuclear can do it, we just have to embrace it.
We have the engines to make it possible. What more do you want?
Yes, a nuclear engine is more difficult to protect against. However, that's why NASA launches over the ocean. The Space Shuttle already burns all kinds of fuels that are highly toxic to breath. Not to mention the variety of dangerous chemicals used in its construction. The trick is that by launching over the ocean, an engine failure will result in it dropping into an area uninhabited by humans. Once in the ocean, it will either stay in one piece and decay over the next few years to a half-century, or it will get so dispersed as to not cause any significant increase in the background radiation.
Now plutonium as a safe substance to eat? well maybe today, or next month, but that same piece will decay, and the left over bits or new matter will then decay to something else which will give up badass gamma rays after 9 years.
It's "safe" to eat, because your body can't digest it. It just passes through and give you the radioactive shits. My favorite link on the subject is the most infuriating to environmentalists.
There are a lot more ideas for Nuclear powered craft than Orion. NERVA and GCNR engines are Nuclear Thermal Engines. i.e. They heat up gasses such as hydrogen until they reach a plasma state. At that point, the matter is in such an excited state that it is exhausted at high speeds, thus providing thrust.
Nuclear Electric Engines are basically Ion drives powered by a nuclear reactor.
Nuclear Salt Rockets contain a highly fissible Uranium salt solution. It's normally stored within a tank that prevents fission, then is pumped to an exhaust port where it is allowed to fission and produce thrust. This is a little safer than Orion since it deals with a controlled burn like chemical rockets, instead of trying to ride a big ass explosion.
More Info on Space Propulsion
That kind of frightens me, to be perfectly honest. I really think we need to rethink this.
I could just see the early discussions about rockets: "Let me get this straight. You want to burn gunpowder through a hollow tube? And someone's going to ride this thing? That sounds a bit scary to me."
Slashdot poster AKAImBatman has boldly declared that if corn can be grown on Mars, that humans can survive there. No need to research this issue further, lets just start sending cord up there to plant.
My dear Mr. Coward. Research all you want, but corn is probably our best chance for growing food stuffs. Let's take an inventory of what we need:
Power: Check. Nuclear Reactors would work well.
Air: Check. Can be cracked from CO2, or cracked from water.
Water: Check. We know it exists at both poles, possibly even as a permafrost.
Shelter: Check. We can engineer structures or dig caves.
So what do we do about food? Well, we have to grow something. Corn has been shown to be a robust plant that can grow under a variety of conditions. It can be eaten straight, prepared as meal, used as flour for bread, and given to cattle for feed.
So, what do we need to grow corn? Well we need various nutrients in the soil. So far, soil analysis says that Nitrates and Microbes are the missing factors. Both can be introduced to the soil.
Corn needs CO2. No problem there. We just need to keep the corn under a pressurized bubble. An inflatable tarp will do. No need for a fancy dome. Some oxygen will be needed, but we already have ways of providing for that.
So what do you think I'm missing here? Do you think we should grow potatoes first? Or carrots? None of those put an end to the world hunger that existed in the middle ages. Corn did. All the early American settlers lived off of corn. And if it was good enough for them, why can't it be good enough for us?