
Ground control bids farewell to Philae comet lander - ComputerGuru
http://www.bbc.co.uk/news/science-environment-35559503
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abpavel
When I asked the team live on Google Hangout chat why they didn't use RTG, for
a mission where solar power is a risky bet, their answer was that there were
too many political obstructions to getting any reasonable amount of fissile
material on-board. I'm certain RTG would greatly increase the chances of
mission success, given the reactors proven reliability and capacity, just like
they serve our Voyagers.

~~~
metafunctor
I appreciate that science cannot operate in isolation of the rest of the
world, what with all the economic and political realities and such. However,
learning that politics was the reason to use an inferior power source for
Philae makes me sad.

Can anyone shed more light on what type of political problems would using RTG
create? Something about weapons grade plutonium, perhaps? Or this being an
European project, and we cannot possibly source the materials from the US? Or
(and I hope this is not it) green “solar good, nuclear bad” dogma?

~~~
david-given
My understanding is that it's primarily a safety issue: these long-duration
missions tend to have to get delta-V boosts by slingshotting around the Earth.
(Rosetta did this _three times_. And a slingshot around Mars once.) While the
RTG capsule is robust enough to survive a launch failure intact, it's _not_
robust enough to survive reentry at interplanetary speeds if the slingshot
goes wrong. It's not like we don't have tonnes of vapourised plutonium in the
atmosphere anyway, but that's no excuse for adding more.

Plus, the kind of plutonium that goes into an RTG is fabulously expensive, not
just because it doesn't occur in nature and has to be made via transmutation,
but because it makes handling so much more complicated.

They'll have done the cost-benefit analysis and decided it simply wasn't worth
it.

(Also, RTGs are _big_ and _heavy_. New Horizons, which is a really small
spacecraft, has a 50kg RTG. Philae only massed 21kg.)

~~~
imglorp
There's probably plenty of human risk transporting it to the launcher, as
well, such as a road accident or having it be stolen.

~~~
ars
> such as a road accident

No, not really. They are pretty safe - you can hold one in your hand without a
problem (barring a burn - they get hot).

A road accident would do nothing harmful at all.

> having it be stolen

That strikes me as pretty unlikely - they don't exactly drive on public roads.

~~~
barkingcat
Nuclear missiles, fissile material, reactor cores, etc are transported on
public roads - where else would they go? We haven't invented transporters yet
so transportation is still roads, rail, sea, air - these things don't just
magically appear at the launch site or at the power station. Someone needed to
drive the semi that gets it there.

There is absolutely a chance of fissile materials being stolen in transport -
that's why there's multiple levels of security and multilateral treaties with
most countries around the world about this kind of issue.

[http://www.patriotnetdaily.com/wp-
content/uploads/2015/11/Nu...](http://www.patriotnetdaily.com/wp-
content/uploads/2015/11/Nuke-rear-ender-Feds-armored-vehicle-collides-into-
truck-with-missile.jpg)

~~~
ars
I meant the road from the assembly plant to the launch platform.

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eponeponepon
I think we'd probably all long since accepted that was the inevitable end for
Philae. Although it's a little bit sad that they didn't get the perfect
landing and imagery they were after, the whole project's just been staggering
- even if the interpretation that they 'aimed for the first landing on a comet
but got the first two instead' became so widespread as to be a gag, it doesn't
make it any less true...

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AstroJetson
Philae was a great mission. Flying into space, linking up with a comet, then
landing a probe is the stuff of science fiction. 60 hours of data really
pushed the science forward quite a bit. I'm missing why people think it wasn't
a success.

~~~
jsprogrammer
They are probably judging it by its mission goals and whether or not they were
completed successfully.

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nashashmi
I want to see a comparison between what we learned and what we were trying to
learn. That is how we can see if this mission was a success.

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mietek
Seems like a fine day to watch “Ambition” once again — a short film created in
collaboration with ESA to celebrate the Rosetta mission.

[https://vimeo.com/109903713](https://vimeo.com/109903713)

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xlayn
First than nothing, traveling around space following a comet and landing...
it's a marvel of engineering.

On the other hand a technical discussion on the "nuclear vs solar" powering of
Philae would be interesting.

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akavel
Does anybody know of any decent _layman-oriented_ summary of the _successful_
measurements performed by Philae & Rosetta? And any interesting and/or
surprising findings and conclusions? After quick googling I've found this:
[http://www.esa.int/Our_Activities/Space_Science/Rosetta/Scie...](http://www.esa.int/Our_Activities/Space_Science/Rosetta/Science_on_the_surface_of_a_comet)
from July 2015 (e.g.: _" [CONSERT] results show that the small lobe of the
comet is consistent with a very loosely compacted (porosity 75–85%) mixture of
dust and ice (dust-to-ice ratio 0.4–2.6 by volume) that is fairly homogeneous
on the scale of tens of metres"_) but I'd be interested in more, more recent,
and with more explanations and details.

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sidcool
This is just the beginning. The lessons learnt from the mission will be
invaluable

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manarth
Haven't they ever seen Robot Wars? Everyone knows you need a flipper to get
yourself upright again.

~~~
ccrush
And a substantial gravity well. Don't forget that. It's quite important.

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mikerichards
All that dust has now covered up the 'a' and 'e' on the lander. One day Phil
will come back looking for the creator.

