
Research into fusion went down a blind alley; a means of escape may be at hand - JDDunn9
http://www.economist.com/news/science-and-technology/21676752-research-fusion-has-gone-down-blind-alley-means-escape-may-now-be
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guimarin
The problem with Fusion has always been that R&D associated with it has no
bearing on any first order weapons technology. Sure you might be able to put a
reactor on an aircraft carrier, but studying powergeneration from fusion
reactions does not yield higher yield!

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trhway
>The problem with Fusion has always been that R&D associated with it has no
bearing on any first order weapons technology.

actually i think it is quite opposite - the inertial confinement approaches
have from the start been the most promising, and they are relatively easy to
miniaturize - thus paving the way for the neutron weapons without fission
primary. No first-rate power - who already has nuclear weapons and thus has no
real need for new types of neutron weapons - is interested in second-grade
players obtaining such weapons bypassing the need for fission primary, as all
the hurdles related to fission primary is what provides for non-proliferation.

Thus all the government funded research has been only in non-miniaturizable
(as seen decades back) Tokamak and laser confinement. Sandia Z-machine (great
inertial confinement approach) could have been burning DT targets at the end
of 199x, yet they started to do it only 15 years later (at least officially) -
somebody definitely wasn't in a rush :) With tremendous progress in solid
state lasers i kind of curious what fate (ie. government funding) is waiting
for NIF as upgrading its warehouse size 3% efficient lasers to container size
20-50% efficient solid state would obviously be in order. Yet it doesn't seems
it is going to happen - the last monthly NIF's status update was in May 2014
and officially it has stopped ignition experiments and back to material
research (simulating plutonium compression in the nukes)

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Florin_Andrei
> _and they are relatively easy to miniaturize_

Wait, really? How?

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trhway
while it is obviously a sarcasm, it suggests that there is need to point
obvious difference between energy and power and its density. Inertial
confinement schemas don't require large energy, they require huge power and
power density though. I.e. a few joules in a femtosecond impulse concentrated
in a few cubic millimeters volume. Reaching that power and density is just a
pure engineering task, there is no hard physical limits preventing it as there
are for example on the minimal size of tokamak.

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wmil
I'm curious what HN thinks of that last line in the article, about solar.

"More likely, cheap photovoltaic and energy-storage technology will mean that
much of humanity’s energy comes from a different fusion reactor—one 150m
kilometres away, called the sun."

5 billion years of evolution haven't given us solar powered animals that can
run around. It seems like there are some significant hard limits on solar
technology.

Energy storage technology actually makes nuclear much more practical... the
big problem it faces is that it generates very consistent power, but power
demand fluctuates by time of day.

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chrischen
> 5 billion years of evolution haven't given us solar powered animals that can
> run around. It seems like there are some significant hard limits on solar
> technology.

What do you think animals run on? Gasoline? Plants are like batteries, storing
solar energy. Animals, including humans, charge up by consuming these plants.
And for those who don't eat plants, they eat charge up by eating the animals
who charge up on the plants.

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JoeAltmaier
Again, we can call oil 'solar powered' by that means. Of course 'solar
powered' should mean 'directly powered by sunlight captured by the creature
itself'. No animal can do this, because the light X capture efficiency is far
too low.

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chrischen
Oil is considered a non-renewable resource. Plants however are renewable, so
they are fundamentally different.

You can consider the solar->plant->animal cycle to effectively be similar to
using solar panels. Using solar panels directly would be inefficient without
batteries anyways, so the solar->plant->animal cycle is directly analogous to
how we would use solar panels.

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jegutman
Quick google search is about 100 wH per square foot of surface area. I'm just
estimating about 8 square feet of surface area (one sided) for a human.
Assuming 12 hours a day at that rate you get about 9.6 KwH or ~8000 kcal. With
perfect efficiency and a storage system inside the body (which we do have, but
not for light energy) that's probably doable.

Obviously our tissue is much well less adapted to so many hours of sunlight
compared to plants. Also even plants only absorb a relatively small part of
the light spectrum (none of the green light). Also even plants required
compounds from the earth and the air to actually harvest the energy to store
so it's a pretty complicated process to do in an actively moving human.

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gene-h
It appears you are assuming 100% efficiency for conversion of solar energy.
The maximum efficiency possible for solar cells is the carnot efficiency at
86%.

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jegutman
Yea, this was kind of giving an upper bound. Actually that's not very
impressive given that people CAN burn more than 8000 calories in a single day.

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astazangasta
Can anyone who knows about fusion comment on non-plasma containment methods
for producing fusion reactions? In a plasma only a small minority of particles
will have enough energy to produce fusion; this means the vast majority of
collisions will just send your ions pinging out of the magnetic bottle they
are in. This seems a futile, difficult way to get what you want. Surely there
are strategies where only high-energy collisions are likely; what are they?

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drjesusphd
The theory of how collisions make you lose particles, like you describe, is
known as "neoclassical" theory. It's actually quite well-understood[1], and is
what Wendelstein 7X is optimized for.

So while collisions are a major concern in stellerators in this sense, they
are less so in tokamaks, where turbulence is the main limiting factor.

[1] By those smarter than me, that is. It's incredibly complicated.

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asgard1024
Although I think the fusion will eventually happen (and ITER will help), I
wish it wouldn't.

I think having fusion is a danger for our civilization. People will use this
energy for stupid things, like moving mountains; eventually, it will either
heat up the planet or produce huge amount of toxic waste or use up all the
water we will be able to find. It will be like with carbon fuels but order of
magnitude worse.

I would much rather see our civilization to learn to live with the plentiful,
yet on decent timescales sustainable, solar energy.

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jjtheblunt
Where, by using the subjunctive verb "may", they mean "is not".

