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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.
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.
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, possibly to the point of not including a lander. Not only that, you need to oversize the RTG so that when 10 years of zooming around the solar system are up, that it still has enough juice to do the work you want.
The people who designed Rosetta/Philae are rocket scientists, and I am not second guessing their choices. What they have already achieved is phenomenal, and the science has only just started.
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. . . . 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 power is impractical for legitimate engineering and economic reasons that go far beyond simple public fear. If I am wrong, someone please correct me with good evidence.
This is only because of precaution-principle aficionados, gaia loving, "activists" who objected to both the building of new, safer, reactors and reactor design research.
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.
How do you plan on doing that? Like, do you have milestones and action items?
"First they came for the slanderers and i said nothing."
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.
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
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.
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.
> 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.
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.
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.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.