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What Would Have Happened If Philae Were Nuclear Powered?
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.
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...
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.
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
Aw come on! How many of us haven't dreamed of building our own breeder reactor in the back yard during our youth to earn a Boy Scout merit badge.
"A person is smart. People are dumb, panicky dangerous animals and you know it." - K
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 !
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.
Better known as 318230.
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.
The team fully expects Philae to get more light early next year. http://www.cbc.ca/news/technol...
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 and a series of slides.
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.
For more, see my letters on energy:
To The Honorable James M. Inhofe, United States Senate
To whom it may concern, Halliburton Corporate
and the the collected rants of the Trix Rabbit of Thorium.
<blink>down the rabbit hole</blink>
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.
moox. for a new generation.
So, let me see if I understand this... You have a device that needs 32 watts of electricity to operate. You're proposing we power it with an RTG, which are typically only 3% efficient at heat conversion. So that RTG has to produce at least 1.1kW of heat. You're telling me that you want to land a 1.1kW heat source on a body whose surface measures below -70C, and whose surface is made of frozen ammonia, water, methanol, carbon dioxide, and methane. Anyone see the problem here?
... what size RTG do you want to stick on it?
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 the same group that gains from global warming denial. The same group that gains from wars in the Middle East. Do you need a hint? Yeah, let's scapegoat each other, particularly lets scapegoat anybody who cares about the future of the planet. Don't want those people listened to, or we might start taking this "not using so much oil" thing seriously someday.