What Would Have Happened If Philae Were Nuclear Powered? 523
StartsWithABang writes After successfully landing on a comet with all 10 instruments intact, but failing to deploy its thrusters and harpoons to anchor onto the surface, Philae bounced, coming to rest in an area with woefully insufficient sunlight to keep it alive. After exhausting its primary battery, it went into hibernation, most likely never to wake again. We'll always be left to wonder what might have been if it had functioned optimally, and given us years of data rather than just 60 hours worth. The thing is, it wouldn't have needed to function optimally to give us years of data, if only it were better designed in one particular aspect: powered by Plutonium-238 instead of by solar panels.
I'm quite surprised it wasn't (Score:2)
I had the mistaken belief that all space probes / landers were nuke-powered.
Re:I'm quite surprised it wasn't (Score:5, Informative)
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This was a NASA project?
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As will the people who it risks landing on if it doesn't escape orbit for some reason.
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If an out-of-control rocket falls on my head, whether it was carrying a little plutonium or a solar panel isn't going to be high on my list of concerns.
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not a reactor. Other info (Score:4, Insightful)
> we don't want plutonium-powered reactors
Fyi space probes don't reactors. Like the tritium I keep next to my bed, and the isotope in your smoke alarm, it just sits there slowing releasing a little energy. Carrots are the same.
For more fun facts that might interest an environmentally concious person , check out one of Patrick Moore's articles about nuclear energy vs the status quo.
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Rosetta/Philae returned to Earth three times for gravity boosts. Each time it was going at speeds which would guarantee its destruction if it hit the deeper parts of the atmosphere. Had this happened and Philae had carried an RTG, it would have been the end of ESA due to the public outcry, and NASA would likely be in public relations trouble too.
There are places for RTGs, but Rosetta was not it. Philae may have died prematurely, but ESA is alive to try again.
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I think it's got more to do with people not wanting chunks of plutonium raining down should something go wrong.
And when the engineers explain that due to the design it's virtually impossible that would ever happen, *then* is when the hysteria gets blamed for the outsiders getting panicky anyway.
This "hippie" isn't worried. (Score:5, Insightful)
we don't want plutonium-powered reactors on an exploding rocket
Back up a bit, who's the "we"?
I recall seeing testing footage for the RTG in the Cassini probe, among other things the tests involved a large artillery gun and a steel wall a few feet thick. Cassini was particularly controversial because it made a 'sling shot' flyby of earth at a much greater speed than escape velocity. From the tests I saw in the doco decades ago the worst thing that could possibly happen with an RTG is that it falls from the sky directly onto someone's head. Far from being anti-nuke, I'm actually interested the idea of "pebble bed" reactors (materials research is what's needed there). I'm also in favour of "full life cycle" nuclear power as practised in some parts of the EU. I don't know of a -science based- environmentalist/hippie/greenie who thinks otherwise. I've held these views since the early 90's, I'm not alone either, James Lovelock and some other influential greenies expressed similar opinions in the early 2000's
I speak to you today as a scientist and as the originator of Gaia Theory, the earth's system science which describes a self regulating planet which keeps its temperature and its chemical composition always favourable for life. I care deeply about the natural world, but as a scientist I consider that the earth has now reached a state profoundly dangerous to all of us and to our civilisation. And this view is shared by scientists around the world. Unfortunately, governments, especially in Europe, appear to listen less to scientists than they do to Green political parties and to Green lobbies. Now, I am a green myself, so I know that these greens are well intentioned, but they understand people a lot better than they understand the earth, and consequently they recommend inappropriate remedies and action. Lovelock 2005 [jameslovelock.org].
Disclaimer: According to my parents I became a Hippie back in 1976. Like any other social group, "Hippies" in general are reasonable people if you stop insulting them and feeding them on bullshit.
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I had the mistaken belief that all space probes / landers were nuke-powered.
Plutonium-238 is not weapon grade... So it would never have been "nuke-powered".
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Re:But ... But ... But ... (Score:5, Insightful)
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The precaution principle doesn't apply to nuclear reactors. Their pros and cons are well understood. The fact we are running old reactors is easy to blame on hippies but it's not the hippies who failed to build them. They're an easy scape-goat. Why do you really think we're left with old dangerous reactors, any one of which might cause a nuclear accident, making the public even more wary of nuclear power? Who gains from us sticking with fossil fuels? It's not a small minority of tree huggers. It's th
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The fact we are running old reactors is easy to blame on hippies but it's not the hippies who failed to build them.
No, but they raised the costs high enough that it was no longer economically viable. The environmentalist movement is directly responsible for global warming due to blocking the switch from coal to nuclear power.
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How many incidents/fatalities has the fossil fuel industry caused in its lifetime?
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No, it's the solar wind turbines that are killing them. We should be burning good old-fashioned Space Coal instead.
Re:I'm quite surprised it wasn't (Score:5, Insightful)
Er you mean logical and obviously superior?
It would be superior, but not logical. Using a nuke would have doubled the cost of the mission, due to handling costs and higher payload mass. Since the ESA has a fixed budget, doubling the cost means half as many missions. Rather than a few expensive "superior" probes, it is better to launch more missions, and live with the fact that some of them will fail.
Re:I'm quite surprised it wasn't (Score:5, Insightful)
I was ignorantly assuming that they'd do everything they could to insure the accomplishment of the mission. I realize how foolish I was now.
Yes, that is a very foolish assumption. Even if they spent a quadrillion euros, they still could not do everything to ensure success. Real life involves tradeoffs. Most people learn this by the time they are adults.
Re:I'm quite surprised it wasn't (Score:5, Informative)
I was ignorantly assuming that they'd do everything they could to insure the accomplishment of the mission. I realize how foolish I was now.
Yes, that is a very foolish assumption. Even if they spent a quadrillion euros, they still could not do everything to ensure success. Real life involves tradeoffs. Most people learn this by the time they are adults.
Precisely, no plan in the history of planning has survived contact with reality undamaged. He should brush up on the concept of diminishing returns [wikipedia.org] which is basically what you are talking about. There are other interesting places to visit and blowing your budget on one mission is dumb.
Re:Nuclear Power has Dangers (Score:5, Informative)
The first is that if something goes wrong on takeoff you risk what is effectively a 'dirty bomb' going off somewhere in the Earth's atmosphere which is not good.
Its not nearly as bad as you think. The biggest impact of a dirty bomb in a city would be psychological.
In the atmosphere, less important.
had better make sure that the craft does not return for Earth for a few billion years otherwise, again, it is like a dirty bomb going off in the atmosphere.
Uh, nuh. Pu238 half-life is 88 years. Here is the most basic clue about radioactivity: radiation intensity is inversely related to halflife. If it has a billion-year half-life, it is barely radioactive at all. A dirty bomb needs something with lots of radiation, and so a short half-life.
Re:Nuclear Power has Dangers (Score:5, Informative)
Except that you are missing the fact that a nuclear battery [slashdot.org] is not the same think like a nuclear reactor. You can build a nuclear battery with something around a cup full of material, whereas a nuclear reactor needs a significant larger amount of material. Also it is funny how you mention Fukushima, the health effects in this incident where rather minor [wikipedia.org]. There are chemical industrial accidents with significant higher casualty rates than that. If you mentioned Chernobyl you may have had a point, but not with Fukushima.
Re:Nuclear Power has Dangers (Score:5, Informative)
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Re:I'm quite surprised it wasn't (Score:5, Informative)
Re:I'm quite surprised it wasn't (Score:5, Informative)
About 8% in 10 years; planners need to know about it, but that's hardly a big concern.
Given the many missions they've been used on successfully, that doesn't seem to be a major problem. And if you're willing to fold out big solar panels, you obviously have the budget for heat sinks.
They are by far the best known battery technology for robotic space exploration, satellites, and probes.
Re:I'm quite surprised it wasn't (Score:5, Informative)
Philae does not have fold out solar panels. It is covered with panels but nothing to fold out. So not mass budget there.
The whole thing has a mass of about 100kg. There is not much to spare in it.
Re:I'm quite surprised it wasn't (Score:5, Informative)
I was speaking generically, since the parent made a generic point. Let's look at Philae in particular. The probe gets about 32W peak at 3AU. Insolation (W/m2) is roughly 1300W at 1 AU outside the atmosphere. At 3 AU, it's about 150 W. At 20% efficiency, in order to get roughly 30W, the probe needs to have a minimum 1 m2 facing the sun. But since only about 1/3-1/4 of the probe is exposed to sunlight when plastering the panels to the probe's body, there are about 3m2 surface area. That's also what we get from its dimension (about 1m x 1m x 0.8m). A 32W RTG would generate about 600W of waste heat, something that is easy to radiate over 3m2 into space, assuming reasonable operating temperatures for the probe (and actually, a smaller RTG is sufficient).
In fact those numbers generalize: no matter how large or small you scale this, radiating heat from an RTG is going to require less surface area than getting the same amount of power from solar cells.
And there doesn't need to be. Philae contains a 1000Wh disposable battery, a 140Wh rechargeable battery, and 32W-peak solar cells. The 1000Wh battery is intended to discharge 60h at an average of 16W. That tells you that pretty much the entire electrical system could be replaced with a 16W RTG (and a small rechargeable battery or supercapacitor for peak loads if needed).
At typical RTG efficiencies of 3-5W / kg, that means you're somewhere around 3-5kg for an RTG capable of powering the entire probe for a few decades (that includes maybe 100-200g Pu238), generating about 150W of waste heat.
The conclusion is that an RTG would likely have been technically superior to the current power design in pretty much every respect: weight, surface area, reliability, simplicity. The only reasons for not using an RTG are cost and politics (and the cost part itself is largely due to politics too).
Re:I'm quite surprised it wasn't (Score:5, Informative)
The entire system is designed to operate in peak loads much of the time with long idle periods between, you can't downsize the battery that much.
And RTGs are heavy compared to their output in the inner solar system. A SNAP-19 fits the generation bill (30 watts at beginning of life) but that's 12 kilograms, which is almost certainly heavier than the solar panels.
But the real reasion is, what others have mentioned, cost. And no, it's not a case of "the cost part itself is largely due to politics", it's that plutonium-238 is simply expensive, period. You're talking a product only produced in a few parts of the world from a raw material (neptunium-237) that's only extracted in a few parts of the world in very small quantities from a raw material (nuclear fuel rods) that's already very expensive and difficult to transport. The neptunium takes years to accumulate in its reactor and must be handled with extreme safety protocols during the extraction, and properly secured against misuse. It then must be irradiated for long periods of time, converting it one atomic collision at a time to plutonium 238 using a tremendous amount of energy. Only then can the plutonium be extracted - and once again, you're talking the need for extreme safety protocols during the process, and proper security. None of that is "politics", it's simply the way it is plus very rational handling procedures.
That's the problem, you can't get U238 anymore. (Score:5, Informative)
Basically the US has exhausted its meager supply. And the few supplies existing elsewhere are being jealously hoarded.
There's ways to MAKE more, and improve nuclear power at the same time. But nobody wants to talk about it.
Because nukes = bombs. M'kaaay?
Re:That's the problem, you can't get U238 anymore. (Score:5, Interesting)
This is one of my primary goals in life. Get nuclear more accepted in the US, then start building Thorium reactors across the country.
Soon
Re:That's the problem, you can't get U238 anymore. (Score:5, Insightful)
Re:That's the problem, you can't get U238 anymore. (Score:5, Interesting)
This is one of my primary goals in life. Get nuclear more accepted in the US, then start building Thorium reactors across the country.
Glad to hear it! If we love our children, there really is nothing quite as important.
For every 1000kg of U-233 bred with thorium in a LFTR, ~15kg of Pu-238 is produced. Here is Kirk Sorensen discussing the waste stream of a two-fluid LFTR [youtube.com] and a series of slides [thoriumene...liance.com].
So every 1 gigawatt LFTR reactor would produce the necessary amount of Pu-238 to fuel ~3 Voyager-class (4.5kg) space probes, every year. Beyond Voyager's simple purpose and its 400 watt electronics package, think of what our space probes could do with more energy. Locomotion, drilling, small maneuvering adjustments or a steady acceleration using ion thrusters [wikipedia.org].
For more, see my letters on energy:
To The Honorable James M. Inhofe, United States Senate [scribd.com]
To whom it may concern, Halliburton Corporate [scribd.com]
and the the collected rants of the Trix Rabbit of Thorium [slashdot.org].
Re:That's the problem, you can't get U238 anymore. (Score:5, Interesting)
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Right .... (Score:4, Insightful)
If it was nuclear powered, then it would have been much heavier and would require a much longer mission and use something more than single-use devices. The entire scope of the mission would have to change!
The primary batteries were for the main mission, The solar panels were "extras". So, nothing much would have been gained if this was nuclear powered device and nothing else changed.
Nuclear powered spacecraft are only really needed outside Jupiter's orbit. Or perhaps on landers designed to operate for extended period of time with a reliable power supply. For the rest, the extra weight is something that is not desirable.
Re:Right .... (Score:4, Interesting)
The solar panel were designed to output 32W at 3AU. Assuming the probe can run on that power, that's merely 64g worth of PU-238 (0.5W/g). Though, this is its thermal output. If you consider that Seebeck generators have a 10% efficiency, you could get 32W electrical out of 640g of PU-238. Let's account for the 10 years trip, so let's make it 1kg.
I'm pretty sure the solar panel and batteries are heavier... And the wonderful thing ? You can power the probe continuously !
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1kg of fuel, but you forgot the head to electricity conversion system which is rather large and heavy. Keep in mind that the whole device is about the size of a domestic washing machine, and funnily enough that's also about the same size as a typical space borne RTG.
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The weight of the actual plutonium isotope is but a small fraction of the weight of the finished RTG. There's the thermocouple wires, the iridium cladding, the graphite casing, the metallic casing, etc. No one has made an RTG with just 10s of watts of output since the 1970s, but those designs weighe
Hindsight is 20:20 (Score:5, Funny)
And if that comet then hit earth, do you know what a huge catastrophe that would have caused?
Then we would be saying 'ah but couldn't they just use solar power?'
Re:Hindsight is 20:20 (Score:5, Funny)
A nuclear powered comet? NIMBY!
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If you're being sarcastic: Point taken.
If you're being serious: That might cause a political catastrophe 'cos of the "scary fallout"*. But I doubt it would cause a nuclear catastrophe, 'cos I don't think a chain reaction can be triggered in a small amount of fuel grade plutonium by merely hitting ground (even if it is at high speed).
* It's not actually fallout per se, because it's not a consequence of a nuclear reaction, but a chemical reaction (fire). But it would be a scattering of radioactive particl
The Great Big Rock (Score:5, Informative)
And if that comet then hit earth, do you know what a huge catastrophe that would have caused?
Then we would be saying 'ah but couldn't they just use solar power?'
The mass of the Churyumov---Gerasimenko comet is roughly 1 x 10^13kg. Should it ever fall to earth, I wouldn't expect the dispersal of U-238 from an aging Rosetta-class probe to be my biggest concern.
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With a RTG, it couldn't have got to the comet. (Score:2, Informative)
It's a question of weight. No matter how you build them, nuclear Radioisotope Thermal Generators are heavy. This mission was heavily mass-constrained. What they wanted it to do was at the limit of what the rockets were capable of.
Add a several-hundred-kilogram RTG to to mix, and the 'rocket equation' kills you. You just cannot get the probe to the comet. Solar panels were the only option.
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The SNAP-9A RTGs put out over 500 watts of power - about 16 times what the solar panels on Philae would produce at the time it intercepted the comet.
Those RTGs weighed only about 25 pounds each - much less than a set of solar panels + batteries. That power increase would have allowed a lot of extra options (such as a higher quality datalink) for about the same overall weight.
A SNAP-3B RTG could have put out about 50 watts - a bonus of about 50% power - and weighed less than FIVE pounds.
Re:With a RTG, it couldn't have got to the comet. (Score:5, Interesting)
No matter how you build them, nuclear Radioisotope Thermal Generators are heavy.
That's totally inaccurate. I went into details about this a couple days ago when Philae was discussed here. In that case someone said that because it took 10 years to arrive at the comet, an RTG couldn't have been used. I'll just copy/paste my other post since it already covers your statement.
The lander only uses 32 watts of power. The MMRTG used in Curiosity provides 125 watts of power initially, and 100 watts after 14 years. The mass of that specific RTG (the MMRTG, 45kg) would be too great for use in Philae, but then it also produces 3 times more energy than needed (even after 14 years). RTGs have been made in many sizes for many different applications, so it would simply have been a matter of designing an RTG that produces 40-45 watts of power after 10 years.
However, one of the main uses of the 32 watts of power required by Philae is just to keep the batteries warm so they don't fail. RTGs produce more "waste" heat than they do electricity. For example, the MMRTG used in the Curiosity rover produces 2 kW of heat, of which 125 W is converted to electricity. The extra heat is used to keep the various temperature-sensitive parts of the rover nice and warm so they don't fail. With Philae, a good portion of the 32 watts of the solar power it requires is just to keep the battery warm. So if an RTG were used, it wouldn't even need to produce 32 watts of electricity since it can keep the lander warm directly.
Looking at the mass and wattage produced, the RTGs ("SNAP-19") in the Pioneer probes would have been just about perfect for Philae. They produce 40 watts of power and weigh 13.6 kg. Philae's current electrical system weighs 12.2 kg, so that's at least in the ballpark. The RTGs on the surface of the moon, as manually placed by Apollo astronauts's would have been a bit heavy at 20 kg. One of those RTGs was still producing 90% of its power after 10 years.
The SNAP-9A used in the Transit 5B-2 navigation satellite launched in 1963 weighed 12.3 kg and produced 25 watts of power. That looks about like a perfect fit for Philae, and I'm sure more efficient thermocouplers are available today that could further reduce the weight.
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They could also have made Rosetta much larger, and possibly have got to its destination much faster, by launching on a Saturn V rather than an Ariane 5.
(Unfortunately, the jumbo-sized booster was unavailable - as was the RTG.)
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Several-hundred-kilogram?
Here's a table of RTGs in space probes: http://en.wikipedia.org/wiki/R... [wikipedia.org]
Almost half of them are under 20kg. One is only 2.1kg.
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Poisoning of Alexander Litvineko [wikipedia.org]
Re:With a RTG, it couldn't have got to the comet. (Score:4, Informative)
That was POLONIUM (Po), not PLUTONIUM (Pu)
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No, it wouldn't. Philae weighted about 100kg. A modern 30W RTG (same as Philae's solar panel output) is about 10kg, less than Philae's solar power-based system. But probably a much smaller RTG would have been sufficient, since you really care about average output over a rotation period.
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It seems there are a LOT of people who think RTGs are similar to nuclear reactors. Their idea seems to be that the RTG is heavy because it must have gamma radiation shielding around it. This is not true. RTGs emit alpha rays and heat, no gamma ray shielding is needed which means RTGs are lighter than solar panels producing equal amount of heat and and electricity.
If Philae Were Nuclear Powered? (Score:2)
Phil would receive excessive Radiation Poisoning.
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It's because humans suck at judging risk. (Score:2)
Gregory Benford had a great column about this [sfsite.com], all the way back in 2000. It also involved a nuclear powered satellite.
It's human nature to react more extremely to new things, especially if they seem "unnatural." This might have been a survival instinct in bygone days, when the hominid who noticed that bush was out of place could take another path and avoid getting eaten by the sabertooth tiger behind it. But like so many such instincts, it translates poorly into the technological era.
Ignorant Article (Score:5, Informative)
The writer of the article didn't do his research. The designers did not expect the instruments to survive the approach to the Sun. So this could not have gone on for years and years.
From: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions "In any case, by March 2015, when the comet is closer to the Sun, it is likely that the lander will become too hot to operate."
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It doesn't work like that, it isn't a chemical fuel you can burn or save. The amount of Pu-238 you need is dictated by your peak power demand. How long it lasts is dictated by nuclear physics (the half life of Pu-238.) You have no control over how fast the plutonium is used up.
Job Offer (Score:5, Funny)
Hi there, I'm Bruce Halberstadt, the chief scientist involved in the Philae lander design. If only we knew of this option when we were designing our lander!
Would you like to come work for us on the next lander? We need more people like you.
We've been hiring all of the top internet commenters for our next project, I think it's going to be spectacular. I can't confirm it just yet, but from recent meetings, it looks like the next project will be a giant robot that searches for extra-terrestrial boobies, with devices on-board to send back relevant cat videos. With your help, maybe we can make this thing nuclear powered.
Bruce Halberstadt
Really? (Score:2, Insightful)
This has been done to death in a variety of places. An RTG was not used for many reasons such as mass and availability, balanced off against the science experiments that both probes carried. Rosetta was always slated to do most of the experiments, and the landing of Philae was always an unpredictable event (I've read that a matching set of harpoons kept on Earth for the last 10 years in a vacuum also failed to fire).
But think about it. Add an RTG, which adds mass, which means less science overall, possib
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When it comes to RTGs vs solar, the basic rule of thumb I've read is that solar is good sunward of the asteroid belt, and RTG is better outward of the belt.
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Add an RTG, which adds mass
Other considerations aside, it really would not have added appreciable mass. There are existing RTGs producing about the right amount of power (20-30W) with 12 kg masses similar to the ~12 kg mass of Philae's solar system. You can read about them on wikipedia or a bunch of informative comments in this very thread.
I'm no aerospace engineer. . . . (Score:2, Insightful)
. . . . but I'm not sure how viable Plutonium is as a power source. Most of the spacecraft that use it are quite large and heavy and not designed to land themselves (for instance, the Galileo spacecraft was Plutonium-powered while the lander it dropped was not).
Plutonium is one of the densest substances on Earth and I'm guessing the engine you need to turn heat into electricity is none-too lightweight.
My understanding is that radioactive batteries are only used on heavy, long-term missions where solar powe
Problem is... (Score:2)
Problem is NOT the RTG. Problem is the design choice that the lander should anchor during the first contact. The decision that the lander should land and, if necessary, to jump to better place and only then HEAT it's harpoons and melt the surface would save the day. Only minuscule thrusters are needed for it.
Mass (Score:2)
Whilst it is an appropriate use of a nuclear power plant, I'm sure the mass of a nuclear powered probe would have increased the costs and complexity of the launch and landing whilst decreasing the science payload.
I think it would have been far easier just to make sure the harpoons *actually* fired. If it was nuclear powered the probe may have just smashed, instead of bounced, the additional mass. The problem wasn't the power source, it was the landing harpoon. We have never landed on an asteroid before an
Wouldn't that have angered Greenpeace? (Score:2, Troll)
Nuclear power is bad. Exporting radioactive materials to a different country is worse — and a different celestial body is outright horrible.
Solar, on the other hand, is clean and wonderful...
Why can't we here in the US be more like the sophisticated Europe?
Please, don't hate.
RTG (Score:2)
One downside to RTG (Radio-isotope Thermal Generators) is that radioactive elements decay, and this causes the power output to fall off slowly but continuously. And the probe wasn't deployed for 11 years after launch; it's not something that we can activate on deployment. IF the thing had landed properly, in the sunlight, the solar power would have been fine. It's too bad that it couldn't have carried both, but that would have been a hefty weight penalty at launch.
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RTGs only lose about one percent per year (less than that, usually). With the power bonus you get from RTGs (more power per weight when compared to solar panels at that distance from the Sun), you still end up with a large bonus of generated power, even when using the smallest types of RTGs that have been deployed.
A SNAP-3B would have started with about 52 watts, and after twelve years would have about 45 watts of power - compared to the 32 watts worth of solar power available from panels - for a total weig
Heat pollution (Score:4, Insightful)
You're trying to study a temperature-sensitive environment in its natural state. An RTG produces lots of heat. (They are only about 5% efficient, so they produce twenty times as much heat as electrical power.) The presence of the RTG might perturb or destroy the environment you're there to study. I don't have the detailed knowledge to say if this is the case.
Plus the issues others have raised: mass, scarcity of suitable isotopes, and launching highly radioactive material on top of hundreds of tonnes of potentially explosive fuel is something you'd rather avoid if possible.
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This is exactly what I thought.
Then I realized there are situations where that could be beneficial. Maybe expelling some heat from a lander on Mars could reveal something? Maybe focusing heat output could work as a thermal drill on icy environments?
I'm certainly no pro, but I am of the opinion space exploration is fucking awesome.
Philae will wake again (Score:5, Interesting)
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I can no longer tolerate missions that fail on such basic functions, it shows a lack of understanding.
I am curious about your upcoming plans. Are you going to write a sternly worded letter to ESA? Have a hissy fit? Take out a full page ad in The New York Times?
May 2015 (Score:5, Interesting)
Due to several sources closely linked with the Rosetta program, Philae will be getting a whole lot of sun come May 2015 due to the position of the comet as it adjusts it's precession around the sun and moves that particular part of the comet in to near-constant daylight. Expect more news at that point from Philae. You heard it here first, folks.
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Maybe. The problem is that it will have been cold soaked for 7 or so months down to maybe -250 to -350f. I doubt that it was qualified to that, probably more like --100f at the most (least?). The kind of cold we are talking about can destroy just about any electronics.
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PR screwup (Score:5, Insightful)
I get the mission design, and I think most people here get the idea, too. But ESA seems to have missed the boat on the PR and public affairs front.
The demise of the lander after a complete primary mission is being portrayed as a huge failure. As near as I can tell, it did exactly what it was supposed to do for about as long as it was supposed to. Anything beyond that was "if possible".
Additionally, the mission is being shown as a "lander mission" instead of an orbiter with a small lander tacked on. Rosetta is still doing the mission as intended, and most of the objectives are being met very nicely. I see all sorts of comments in the press (and particularly in the European media and media comments section) as another Beagle "cock-up".
I think it's a very nicely done mission that is working very well. It's a shame that it is not coming across like that.
boggles the mind... (Score:3, Interesting)
Re:Wouldn't it suffer eminent heat death? (Score:5, Informative)
this: http://en.wikipedia.org/wiki/R... [wikipedia.org]
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Doesn't nuclear power work by boiling water? Doesn't it require that steam then turning back to water?
Uh, no.
Do a web search on RTG sometime.
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http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator
"One example is the RTG used by the Voyager probes - 23 years after production, the radioactive material inside the RTG will have decreased in power by 16.6%, i.e. providing 83.4% of its initial output; starting with a capacity of 470 W, after this length of time it would have a capacity of only 392 W. A related (and unexpected) loss of power in the Voyager RTGs is the degrading properties of the bi-metallic thermocouples used to convert ther
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heh... that power could run: my laptop, my netbook, my printer, my database server, and my HTPC, with juice to spare.
Re:Wouldn't it suffer eminent heat death? (Score:4, Interesting)
I wonder where there is a break-even whereby it makes sense to send the mechanical stuff ahead but send the computer part on a smaller, faster shot simply due to the power savings and increased processing capacity gained in what would be the time in between the launches.
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Here on earth our nuclear power comes from fission reactors producing 500-3000 MWt of heat which we in turn attach to a glorified thermal power plant consisting of water moving in a closed loop through pipes and turbines not fundamentally very different than a steam engine. This nuclear power is instead the radioactive decay of a small radioisotope, emitting a mere 500Wt (but with no way to turn it off because no fission is involved) which we in turn attach to a relatively unconventional thermoelectric gen
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RTGs don't need steam. They work using the theroelectric effect - which you can demonstrate using a copper wire wrapped around a steel nail, connect the assembly to a milliammeter and fire a hot (blue) flame at it.
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Now as to that temperature that is only high when compared to the relative temperature that the comet spends much of it's time in, is still rather unimportant. You see, the lander is less than a cubic meter in size. (A cubic meter is 1m x 1m x 1m for those that don't understand volumes.)
Now to snag some dimensions from wikipedia, that comet is comprised of 2 parts, the Large lobe whic
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No, it works by turning atoms into other atoms. What you do with the resulting heat and radiation is up to you. Whether you use it to drive a steam turbine, a Stirling engine or a thermocouple is up to you.
Re:What always concerns me (as an uninformed cowar (Score:5, Informative)
Correct me if I'm wrong, but wouldn't it have been really bad if there had been a boatload of plutonium-238 on the Challenger?
Uh, no.
A boatload of Pu-238 won't explode, and RTGs are designed to stay together even in a launch explosion. If I remember correctly, one RTG was involved in a launch explosion, and it was recovered, refurbished, and used again.
like carrots? (Score:3)
Living creatures are already injesting a lot more radioactive material than few kg of dust in that scenario. If you ever eat carrots, potatos, or other root crops you're injesting far more radioactive material - by several orders of magnitude. Bananas also.
Radiation has been here far longer than humans have. It wasn't scary until The China Syndrome.
Re:What always concerns me (as an uninformed cowar (Score:5, Interesting)
Np, it would not have mattered.
Numerous times RTG-powered spacecraft had their main rocket "explode" or "fail" and the RTGs were just recovered. Early models, packed without any precautions at all, basically contaminated some small area.
http://en.wikipedia.org/wiki/R... [wikipedia.org]
Then again, if you are worried about RTGs contaminating things, you should probably pull all your hair out over the nuclear weapon tests that occurred and all the stockpiled weapons, ready to be deployed at moment's notice. Weapon testing contaminated ALL soil around the world with detectable amounts of plutonium. Amount of the substance in RTGs is negligible by comparison.
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Not the same thing. He's not second-guessing the scientists who designed it, he's second-guessing the Slashdot self-appointed experts.
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some of them might actually be certified experts.
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No, it has nothing to do with that. The Nuclear Test Ban treaty prohibits nuclear bomb tests, it doesn't care about radioactive materials directly.