
Experts Urge U.S. To Continue Support for Nuclear Fusion Research - tshannon
https://www.scientificamerican.com/article/experts-urge-u-s-to-continue-support-for-nuclear-fusion-research/
======
devy
Nuclear fusion is probably still decades away. But I am going tangent here,
nuclear fission still have great potentials. Scientists from the Oak Ridge
National Laboratory actually helped China to built Molten Salt reactors in the
70s during Nixon administration. [1] And since then thorium based molten salt
Gen IV reactors have been having renewed interests around the global. China
actually tested the whole system feasibility in Giga Watts scale in recent
years. [2]

Nuclear power is vital part of the energy infrastructure to curb worsening
environment due to climate change - it's still considered superior than all
the other green alternative energies in terms of either 24/7 availability (vs.
solar/wind) or massive scale (vs. geothermal) or location restricted (vs.
hydro) or carbon-free (vs. biomass/bio-fuel). China realized that in their
dire request to transition out their entire energy reliance on carbon-based
energies, it's impossible to do without nuclear. Also, newer reactor designs
are much safer and last longer so a lot of the concerns of radioactive waste
have largely been alleviated.

[1]:
[https://news.ycombinator.com/item?id=10229697](https://news.ycombinator.com/item?id=10229697)
(2015)

[2]:
[https://news.ycombinator.com/item?id=17813614](https://news.ycombinator.com/item?id=17813614)
(2018)

~~~
hirundo
> Nuclear fusion is probably still decades away.

I wrote that sentence in a 10th grade report on fusion, in 1977. Disappointing
that it's likely still true four decades later. In another four decades it's
up to you to make this comment.

On the other hand, so much has arrived that I never dreamed of in high school,
though I consumed scifi obsessively. Not sure I'd swap the internet for cheap
fusion energy. But not sure I wouldn't.

~~~
jessriedel
Note that we've never spent as much money as we've _always_ known would be
necessary to achieve useful fusion power, so the oft-repeated idea that it's
been surprisingly technologically difficult is not actually justified by the
historical track record.

> Typically, outsiders cannot comprehend how the massive expenditures never
> manage to yield energy. Typically, insiders cannot comprehend how little is
> being invested in a project that presents such immense technical obstacles
> and also such potential. A graph commonly passed around among the
> insiders—an enduring scrap of twentieth-century budgetary ephemera—depicts
> the 1976 federal plan to build a working thermonuclear reactor. The graph
> tracks various scenarios for attaining fusion energy. The “maximum” effort,
> the most expensive up front, with initial spending as high as nine billion
> dollars a year, was projected to yield a reactor by 1990. The “moderate”
> effort, with spending never exceeding four billion dollars in a year, would
> take fifteen more years. The fusion community might be easy to criticize for
> its many unmet milestones, but for decades the United States has never come
> close to even the moderate effort. In 1977, when the American fusion budget
> was at its peak, government investment in the research, adjusted for
> inflation, was seven hundred million dollars; by 1991, this had fallen by
> more than half. It is now half a billion, not appreciably more than the
> Korean budget.

[http://www.newyorker.com/magazine/2014/03/03/a-star-in-a-
bot...](http://www.newyorker.com/magazine/2014/03/03/a-star-in-a-bottle)

The chart was produced by Energy Research and Development Administration
(ERDA), which was later subsumed into the Department of Energy and presumably
represented the expert wisdom at the time. It can be found, in 1976 dollars,
as figure 1 here:

[http://www.21stcenturysciencetech.com/Articles_2010/Winter_2...](http://www.21stcenturysciencetech.com/Articles_2010/Winter_2009/Who_Killed_Fusion.pdf)

~~~
Apocryphon
If there's any technology more deserving of a modern-day Manhattan Project...

------
aftbit
I suspect we will transition to PV before fusion actually becomes viable. Even
if we had a working net-positive-energy-balance fusion plant today, it would
be incredibly complicated and expensive to build and maintain. The
temperatures and energies involved are simply massive. On the other hand, we
already have a giant self-sustaining fusion reaction happening in our sky. We
can throw down some solid state and increasingly cheap panels to collect that
energy. Regardless, we should continue to invest in fusion, but we should also
invest in PV research, especially into ways to decrease cost and complexity of
manufacturing solar cells.

~~~
scrumbledober
PV just doesn't scale in the same way. There's only so much surface area to
cover in panels. The power density of fusion is so many orders of magnitude
larger that even with cheap reliable solar panels I think there will always be
a use for working fusion

~~~
pfdietz
PV scales fine. Do the math, please. There is far more than enough land onto
which we can put PV farms. And the cost/W for solar (of which the cost of land
is small fraction) is two order of magnitude below current fusion machines.

~~~
jacknews
Then there's the ocean.

~~~
Terr_
I'm imagining the solitary life of a caretaker living in a little ship that
travels the canals between acres of floating cross-linked solar panels, fixing
wiring and washing off salt deposits.

Poetically, it would be a tale of isolation out in the middle of the Pacific,
but I suppose you'd need to stay close enough to shore that you can transmit
the power using wires, unless it's batched up in chemical storage.

~~~
fyfy18
If you perform electrolysis of sea water the main products given off would be
hydrogen and bleach, both of which could be piped or shipped (if you filled an
oil tanker with hydrogen, would it be lighter than air?) back to shore.
Although a leak of bleach into the ocean may not be very good, it's probably
no worse than the damage done from oil.

------
jillesvangurp
A lot of people are saying fusion is still decades away. That might very well
be true but it might be centuries away unless we change the way we fund the
research. Nuclear fission and fusion research are still happening but there's
no sense of urgency at this point and it's not a very popular topic with
politicians given the issues with reactors invented half a century a go. Back
in those days there was a real sense of urgency and no cost were spared to get
things done. Kennedy says go to the moon. Ten years later it's done. The fear
of the Russians getting there first drove the US to do amazing things.

This stuff doesn't happen by itself and will need a lot of investments and
planning to get it done. At this point a reasonable question to ask is whether
the US will be the one that makes the breakthrough here. They are not the only
ones working on this and arguably it's not a big priority in the US to be
working on this at all. What happens when e.g. China gets there first? They
are working on this as well and they seem to be getting some results. They are
also planning to go to the moon pretty soon. And a lot of the clean energy
tech we use comes from them as well.

------
ohiovr
Just because deuterium is cheap doesn’t mean Fusion energy plants will be
anywhere near economically competitive with conventional power sources even
most renewables. Many of the presumed benefits such as waste control are not
as rosey as most people believe.

It is clear now that plant scaling with known methods are entirely dependent
on magnetic field strength. More powerful magnets will mean more hope for
tokamaks.

Entirely new designs are probably not what the doctors are ordering because
nothing of the sort is anything close to a surefire success in the wings.

So many concepts have come and gone. Tokamak was the closest they ever got.
Look at the plant schematics. Its like building a furnace from a humongous
collection of delicate swiss watches.

~~~
pfdietz
Even with powerful magnets, the power density of a fusion reactor is limited
by what the first wall can withstand, and will always suck compared to fission
reactors. There's little hope a fusion reactor will be able to compete with
fission, never mind the technologies that are beating fission.

What high fields might do is allow use to make small, uncompetitive fusion
reactors, instead of large, uncompetitive fusion reactors.

~~~
ohiovr
Correct and 17 tesla magnets are already hugely powerful. Its a tremendous
amount of structural stress. If it quenches it can explode!

------
zachrose
At the risk of inciting a flame war that I might not be able to understand, is
there any way to characterize current fusion projects against each other? For
example, what can be said about the promise of ITER vs Wendelstein 7-x?

Part of me realizes that there’s no such thing as a “failed” scientific
experiment and that diversity of approaches is good. The other part of me
thinks that a public and competitive spectacle would also be good.

~~~
dukoid
ITER will be an actual tokamak fusion reactor producing energy. Wendelstein
7-X is a plasma containment experiment based on the stellarator design. There
will be no fusion.

Technology for magnetic enclosure was advanced significantly by both. In this
regard, they profit from each other.

Tokamak reactors require a pulsed operation mode. There is no way to sustain
fusion for longer time.

The Stellarators design allows continuous operation, putting less stress on
the structure. The calculation of the winded enclosure structure is quite
complex and it has only become possible to design and implement with
sufficient precision recently.

If I'd have to "bet" on a design, it would be Stellarator. If you understand
German, listen to this podcast. You won't regret it:
[https://alternativlos.org/36/](https://alternativlos.org/36/)

~~~
DennisP
People keep saying Wendelstein won't do fusion but that's not the case.
_Currently_ the 7-X isn't doing fusion because they're using hydrogen. But
they plan to use deuterium later, just like all the other fusion research
reactors, and they'll get fusion reactions when they do. There's really no
reason not to; you get more data and it's easy. People fuse deuterium in their
garages with home-built fusors.

~~~
sterlind
Exactly! AFAICT, the trickiest unknown is maintaining plasma stability and not
degrading the insides (and then, breaking even on power while doing so.)
Wendelstein seems to be on track to steady-state operation; they've held
plasma for 100s, and their graphite shielding seems to be delivering cleaner
plasma streams.

The design for the 7-X wasn't feasible until supercomputers got powerful
enough. We know how to run those simulations; fusion should get more practical
as computers get faster.

------
timwaagh
I all for research into potentially valuable tech. but we have to consider the
fast-falling cost of renewable energy. by the time fusion gets realized at
scale, we might not need it anymore.

~~~
Lev1a
Fusion (once realized): steady energy regardless of weather conditions, from
maybe a few installations per country

Renewables (solar, wind): dependent on weather conditions, would thus require
battery farms for backup during wind-still nights or days with overcast etc.

In my mind the ideal future scenario is a compromise between both solutions:

Have fusion always on and provide a base level of energy production sufficient
for need plus a few percent. Then have renewables lower the target for energy
production through fusion when available. Then we would not need giant battery
farms and renewables would get used to the best of their ability/availability
while not restricting energy consumption due to them not being available 24/7.

Maybe even leave a select few coal/fission plants available but powered down
as a sort of UPS for the energy infrastructure, just in case fusion is N/A and
renewables aren't enough to cover the need.

------
dicroce
We should be funding the shit out of Fusion and molten salt fission reactors.
We're gonna also need to build shitloads of carbon scrubbers and water
desalinization plants.

~~~
neolefty
If our goal is basic research, sure, fusion is great.

But if our goal is to achieve carbon neutrality ASAP, we can't count on fusion
to help because we don't know _when_ it will start working. On the other hand,
renewables + battery leveling are here today and ready for intensive
investment.

Yes, let's do both. But I don't believe fusion research will provide a short-
term alternative to CO2-emitting power sources. I think it's fine with to
spend 1000x on conventional renewables compared to fusion. We can employ an
absolute army of technicians and factory workers _today_ to build out
renewable generation infrastructure, while fusion gets a steady research
budget for post-docs, career physicists, materials engineers, etc.

~~~
jcranberry
What about fission reactors?

------
AcerbicZero
I have no idea if nuclear fusion is feasible in the near future, or what kind
of timeline is required, but I don't see any downside to spending money on
projects like this. Pure scientific pursuits seem to be fund able at
relatively low prices, with massive upsides and no obvious downsides, other
than the opportunity cost of the money being spent.

~~~
pfdietz
Fusion absolutely will not be feasible in the near future. We don't even have
the materials that would be needed to build them. In any other field of
engineering, lack of materials is a showstopper, and new material development
is always painful and slow. And if you examine any of the designs with a
skeptical eye none of them seem promising, and all involve lots of handwaving.

~~~
dwaltrip
You are saying that ITER will fail?

~~~
pfdietz
ITER cannot lead to an economically competitive reactor, even if it achieves
every one of its stated operational goals. It's a massive dead end waste of
money.

~~~
dwaltrip
Although I happen to disagree, that is a different, more reasonable critique
than your original comment.

~~~
pfdietz
My original comment is entirely reasonable. Fusion faces generic obstacles
that are likely unsolvable, and certainly unsolvable in the near term.

Consider the problem of tritium breeding. Fusion reactors have to make their
own tritium -- T from fission reactors would be far too expensive -- but
tritium breeding blankets cannot be tested without a working fusion reactor.
And the requirements for the breeding blankets are seriously constraining.
They must achieve some neutron multiplication (from (n,2n) reactions of
energetic fusion neutrons) to offset losses, not lose too many neutrons to
penetrates/parasitic capture, and be able to give up the produced tritium
fairly quickly. And there are very strict limits on how much tritium can be
lost to permeation into reactor materials (or lost from the reactor exhaust,
since ~99% of the injected tritium doesn't fuse).

No one knows how to do this, or if it can be done economically, or even if it
can be done at all. And I repeat: testing it is going to require a working
fusion reactor! This circular dependency in development will be painful to run
around, and won't happen quickly.

Then there's the matter of materials that can withstand prolonged exposure to
fusion neutrons. These materials have not been developed, in part because this
again requires something close to a working fusion reactor (at least,
something with Q at least ~0.1), and much painful rebuilding as that reactor,
built with less adequate materials, destroys itself over time. This material
development will not be fast, so we will not have working, practicl fusion
reactors soon.

Even when all that is solved, the fundamental problem of fusion -- low
volumetric power density -- remains. That alone seems insurmountable. When you
see a fusion reactor design, ask what this power density is. For ITER, it's
0.05 MW/m^3. For ARC or Lockheed's design, it's around 0.5 MW/m^3. These are
very bad compared to fission reactors.

A final point: the complexity of the irradiated part of a fusion reactor (the
part that's too radioactive for hands-on maintenance) will be MUCH higher than
that of the similar part of a fission reactor. Reliability is going to be an
enormous problem. Making fusion reactors reliable enough for them to be
practically interesting, even if all other problems were solved, will take
much experience and time.

------
DrNuke
Fusion is a materials science problem and materials informatics (machine
learning methods for improving properties and / or devising new alloys) will
help immensely once a new generation of digital-native scientists comes into
the working force. Fusion might not become economically viable for a long time
yet, though, so investments could very probably be moved elsewhere sooner than
later. Healthcare for aging populations in the West and a new space race from
China come quickly to my mind as powerful “distractions” from ITER part II, in
the case part I ignition goes well by 2030. Smaller, more efficient reactors
would not solve the energy problem even if they go successfully past the
laboratory stage, in that being out of question imho.

~~~
pfdietz
Distractions from ITER would be welcome. The power density of ITER is ~0.05
MW/m^3, some 400x worse than the power density of an LWR reactor vessel (and
2000x worse than the power density of the LWR core inside that reactor
vessel). It's a project where research money goes to die, and new materials
are not going to help that.

~~~
DrNuke
Power density is irrelevant for fusion, though: you will never exhaust fusion
“fuel” on planet Earth. It will never be an efficiency problem, like it is for
fission aka uranium.

~~~
pfdietz
No, power density is very important, since it directly affects how expensive
fusion reactors will be. The cost of a machine is a function of its complexity
and size; fusion reactors will be both much larger and much more complex than
fission reactors of the same power output.

~~~
DrNuke
Possibly yes but, even the case, the US, the UK, Japan and France would switch
to fusion immediately, if feasible, to get rid of fission and its waste.
Renewables & nuclear are the perfect mix to contain greenhouse gases
emissions, that’s why the debate is so hot.

~~~
pfdietz
No, nuclear and renewables do not mix well at all. Intermittent low cost
sources of power shoot nuclear's baseload business case in the gut. The
reactors cannot sell power at high enough price enough of the time to make
sense.

~~~
DrNuke
You know, it is renewables to lose, apart of local places blessed by any sort
of competitive advantage (water, silicon, etc.). However, I am not here for
politics and you simply cannot beat nuclear by numbers, though.

~~~
pfdietz
Nuclear is being beaten by the numbers as we speak. That's why renewables are
being installed worldwide and, with a few exceptions, reactors are not.

------
chiefalchemist
> A fusion power plant, it estimated, “could use only 5 kilograms [11 pounds]
> of hydrogen to generate the energy equivalent of 18,750 tons of coal, 56,000
> barrels of oil or 755 acres of solar panels.”

Translation: The coal industry, the oil industry, and the solar industry do
__not__ benefit from fusion. Using history as a reference, it's fairly safe to
presume they will use their influence to sway any decisions in their best
interest.

------
b_tterc_p
I get that fusion can theoretically transform vast quantities of stuff into
useful energy. Can anyone comment on how scalable it would be if proven
viable? Can it be built on a large scale profitably? Can it be built to serve
remote locations off major grids? Can we ship it in reasonably sized space
ships and use it to build bases elsewhere? Can we write off low energy costs
to just churn on some sort of climate saving terraformer?

~~~
scrumbledober
Fusion scales incredibly well. For a given working reactor design, efficiency
increases with size. I think viable working fusion would lead to a more
interconnected grid because of this as opposed to smallscale fusion reactors
being deployed in semi-remote areas. On the other hand truly difficult to
reach places would be perfect for fusion as once it's built it takes very
little fuel to run.

~~~
pfdietz
Fusion reactor economics get worse as you make them bigger (assuming the
smaller one works at all). That's because their power output is limited by
what the first wall can withstand. By the square/cube law, their power/volume
must decline as they are made larger.

------
sien
The full report can be read at :

[https://www.nap.edu/read/25331/chapter/1](https://www.nap.edu/read/25331/chapter/1)

------
jacknews
Is terrestrial fusion even desirable, I understand it will not use the same
"clean" reaction as stellar fusion (deuterium-tritium or D-D vs ordinary
hydrogen).

Can someone with more knowledge comment on whether this report is accurate?
[https://thebulletin.org/2017/04/fusion-reactors-not-what-
the...](https://thebulletin.org/2017/04/fusion-reactors-not-what-theyre-
cracked-up-to-be/)

To me it seems to annul the entire enterprise (other than as a pure research
project) if true?

~~~
ajross
Stellar fusion isn't really clean in the way you imagine; there are lots of
reactions in the star core that produce free neutrons, they just get
reabsorbed by something else because they can't realistically exit the system
like they can in a tiny reactor.

Nor is it realistically achievable, anyway. Fusing products out of bare
protons just isn't productive enough at achievable temperatures.

~~~
pfdietz
In a star like the Sun there are very few free neutrons produced. There are
non-exploding stars that produce some neutrons, but they are AGB stars where
the core gets hot enough for (alpha,n) reactions to occur.

~~~
ajross
Hm... maybe I'm misremembering, but I swear I saw an analysis that showed
neutron loss from a small (i.e. reactor scale) blob of solar core plasma would
be comparable to what you get from existing power reactions. It's true that
almost all the energy production in the sun happens from reactions that don' t
involve neutrons, but the neutrons are flying around nonetheless (and, in a
reactor, would fly right out of the containment).

~~~
pfdietz
What nuclear reaction in the solar core are you imagining would produce
neutrons?

~~~
ajross
Something endothermic? Are you really asserting that no such reaction exists?
They clearly do, the question is whether the cross sections are high enough.
The list of reactions you find in typical explainers are just the ones
involved in energy production.

And I'm no expert, so I'm not going to be able hand you the evidence here. But
like I said I swear I've read this analysis somewhere, and something about
your tone tells me maybe you are misunderstanding the point.

~~~
pfdietz
The most likely would be 13C(alpha,n)16O, but the rate of this would be very
low at the temperature of the solar core.

You might also point to (alpha,n) reactions on Li, Be, or B. But these should
be slower than (p,alpha) reactions on these elements, which destroy them at
temperatures well below (by a factor of ~3 or more) that of the center of the
sun.

Let's see how far I can push your argument. There will be some 7Li produced by
a side branch of the PP cycle (although it is quickly destroyed). Also, 4He
produced by the various fusion reactions will initially have energies in the
MeV range (~1000 mean thermal energy in the core), so it's possible (alpha,n)
reactions could occur from them as they slow down.

------
beezle
Lets be honest about fusion - Experts urge the US to continue employing them
for another 20 years. And thats coming from someone with a physics background.
The fusion industry (and thats what it really is) has managed to string the
public and policy makers along for 60 years so I guess why stop trying now.
Fusion will never be cheap and won't be clean either.

------
vasili111
If we want to really colonize other planets then we need fusion reactors.

~~~
pfdietz
Why would we need fusion reactors for that? Describe the use case for which
they are essential, and I will then tell you why they aren't.

------
jayalpha
While I agree that there is too little money in Fusion research, I would
recommend building Thorium reactors. Thorium reactors could be in a production
setting, if financed, in less then 5 years.

------
ngcc_hk
“Nuclear fusion is still decade away” ... heard that before. Decade before.

------
pmarreck
A well-built modern fission plant is far safer and more environmentally-
friendly than almost all the other solutions out there save for
solar/wind/geothermal.

Fusion is the holy grail, though, and with good reason. At least with fusion
(as with flight 100+ years ago), we have only to look up during the day to
know it's feasible because it's being demonstrated, live, every day!

~~~
Retra
The sun's fusion is powered by the gravitational attraction of ~10e30 Kg of
matter. That is not even remotely an option on Earth, so there is no evidence
of feasibility about the energy produced by the sun, aside from the fact that
it demonstrates that fusion _as a concept_ makes sense.

~~~
pmarreck
> there is no evidence of feasibility about the energy produced by the sun

Don't the most recent fusion experiments have _almost_ the same energy return
as input? That is "no evidence"?

~~~
Retra
What I said was that there is no evidence that fusion on Earth will work that
can be derived from simply looking up at the sun. Context matters.

------
NoblePublius
This feels like hydrogen fuel cell tech — “something better on the horizon”
that will keep you from investing in the obvious: free energy from the fusion
reactor that already works in the sky. I would put every dollar of public
fusion research money into solar and battery storage. That works now. The only
thing fusion research accomplishes, like HFC, is prolong dependence on carbon
energy.

~~~
starbeast
Funny comparison. If you like batteries, fuel cell tech would be one of the
places you would want to be putting some of your primary research money.

~~~
NoblePublius
There is no naturally occurring source of hydrogen. That’s why you see ads for
HFC from Shell and Chevron. Hydrogen must be made from oil or gas. Salt water
electrolysis doesn’t really work at scale as it requires even more oil and
gas. Even if you do SWE with renewable energy, it’s about 22x less efficient
than putting the electricity in a battery. We have fusion. It’s in the sky. We
don’t need it on earth.

~~~
starbeast
I'm talking about fully reversible fuel cells for grid storage, not a hydrogen
fuels economy. So this kind of thing -
[https://www.energy.gov/sites/prod/files/2014/03/f11/rev_fc_w...](https://www.energy.gov/sites/prod/files/2014/03/f11/rev_fc_wkshp_anderson.pdf)

------
AngryData
I don't think we have a choice. Human activities are currently completely
dependent upon the availability of energy. Right now most of that energy comes
from non-renewable sources and is limited. Our only other choice besides
nuclear technologies is covering large portions of our planet's surface with
solar panels, which in itself might cause problems because they will shade out
plants and change weather and climate patterns as they scale. Traditional
nuclear plants get us quite aways farther, but have their own risks, and still
require absolutely enormous mining fields which isn't ideal. Fusion power
however is the holy grail of energy production. We can go pretty much anywhere
and find plentiful sources for fuel.

Of course this is assuming small fusion reactors will ever actually work, but
we have yet to find a hard limit or insurmountable barriers. We have been
progressing slowly but consistently but the payoff would be world changing,
potentially even galaxy changing int he longer run.

~~~
lutorm
_covering large portions of our planet 's surface with solar panels_

Have you calculated it? If I recall correctly, it's actually not a large
portion at all. It's large in the sense that it would be a large
infrastructure project, but it's not larger than the combined area already
covered by buildings.

~~~
AngryData
That is assuming we keep similar power usages as today, but many of our
largest industries are consuming unaccounted for fossil fuel energy.
Fertilizer for example, fossil fuels are used as a reagent in creating
artificial fertilizer, on top of already huge energy costs. The energy
required to make fertilizer out of the air and water, rather than fossil
fuels, is 100x more at best case. 60% of our total crop yield is the result of
artificial fertilizer. Then look at plastics, how much more energy is required
to create nonfossil fuel hydrocarbon precursors? You can make hydrocarbons
from trees, but it might take an entire tree just to make a few cheap plastic
containers.

Many other industries are also powered by mined and drilled organic fuels and
minerals, but are still fairly limited in availability, at least for such
cheap prices/energy requirements anyways which will rise into the future.

Building solar panels to power our planet today isn't insurmountable, but what
about 20 years from now? 50? 100? Power costs are the limiting factor in many
industrial processes, including farming, steel and aluminum production,
aviation and rocketry, indoor farms, plastics, and nearly every other form of
material synthesis.

Don't get me wrong, im not advocating against solar power in anyway, however I
don't think it is an effective source for powering our largest industrial
processes into the future. Even a small 10 man ceramics shop can draw enough
power that they need to call up the local power companies before they turn
their large furnaces on, I see no reasonable way of storing and supplying
those kind of immense power requirements with solar panels and current storage
technologies in any economical way.

------
dogma1138
Do we even had a model for Fussion that is energy poasitive? The only Fusion
reactors we know to work, work by converting gravitational potential energy
into light/heat through fusion this is how stars operate.

All fusion reactions so far require an external input of energy not only to
start them but often to sustain them and even those which are self sustaining
for a short period of time grind to a halt once you try to extract energy from
the system.

So in all honesty while I’m not by any stretch of the imagination an expert in
fusion physics I can at least understand conservation laws, does any of the
current experiments even relies on a model that is at least proven in
principle to be energy positive?

~~~
theothermkn
Stars simply do not "work by converting gravitational potential energy into
light/heat through fusion." The "light/heat," or energy, that stars produce
comes from the mass defect of the fused atoms. Basically, the binding energy
of He is less than the binding energy of the (net) 4 H atoms that go into the
reaction. It works so well in the sun because of the long confinement times
and the long transit time for energy to get from the center of the the star to
the exterior.

"...while I’m not by any stretch of the imagination an expert in fusion
physics...I can at least understand conservation laws..."

I don't think that you have a firm a grasp on their application as you seem to
suspect, though I agree you don't understand the physics of fusion. Your
reasoning is analogous to neglecting the contribution of smokeless powder to
the performance of a rifle, because a rifle is just "converting" the energy
stored in the hammer spring into energy in the bullet.

That's the best I can do for you. Good luck!

~~~
dogma1138
Again gravity is what maintains the reaction going, without it the gas would
expand and the reaction would stop.

I understand how fusion works, what you neglect is that gravity is what allows
you to counter the nuclear forces to cause protons to fuse in the first place,
and what keeps the entire thing from blowing out.

Hence stars are in constant balance between gravitational collapse and their
outward pressure caused by fusion.

“An interstellar cloud of gas will remain in hydrostatic equilibrium as long
as the kinetic energy of the gas pressure is in balance with the potential
energy of the internal gravitational force. Mathematically this is expressed
using the virial theorem, which states that, to maintain equilibrium, the
gravitational potential energy must equal twice the internal thermal energy.”

On earth we exchange gravitational potential with electromagnetism but we
still need to apply the same force to counter the nuclear forces and the
pressure from the reaction once it starts.

All I want to know is if we have a proven net positive model for this reaction
because so far I haven’t been able to find one.

Because as far as I know the vital theroem stands so it doesn’t matter if it’s
gravitational potential or any other force it still needs to be twice the
thermal energy of the reaction.

But you can continue to downvote without actually addressing anything while
ingoring everything we know about stellar fusion and the fact that is
triggered and constantly maintained by gravitational collapse.

So no I don’t ignore the role of gunpowder in a gun, you ignore the energy
needed to create the gunpowder and cartridge in the first place.

That's the best I can do for you. Good luck!

~~~
theothermkn
"...the fact that is triggered and constantly maintained by gravitational
collapse."

What you have written is not a fact. Forces only do work when they act through
a distance. Gravitational potential energy only comes into play during the
ignition of a star. After equilibrium is reached, to the extent that the
star's diameter is "static" potential energy calculations no longer come into
play. No "potential energy" is being "converted" into fusion energy. It's just
not a thing.

"...stars are in constant balance between gravitational collapse and their
outward pressure caused by fusion."

Because of this balance, no work is being done by gravity. That is, no energy
is being released by the force of gravity moving a mass through a distance.

"All I want to know is if we have a proven net positive model for this
reaction because so far I haven’t been able to find one."

It's literally E = mc^2, but it's not "net positive." It's net zero. Matter is
converted into energy. That's it.

"So no I don’t ignore the role of gunpowder in a gun,..."

It's an analogy, and it's straightforward enough that the onus is on you to
work out the pieces a little better than you have. HINT: The "energy needed to
create the gunpowder..." _is_ the binding energy in the various nuclei.

~~~
dogma1138
>Because of this balance, no work is being done by gravity. That is, no energy
is being released by the force of gravity moving a mass through a distance.

I didn’t say it extracts energy from gravity, gravity is constant and it is
what keeps the reaction going.

This balance is dynamic equilibrium, gravity continues to counter the gas and
radiation pressure of the star’s fusion reaction if you remove gravity from
the equation fusion stops because the pressure would cause it to expand until
the reaction stops.

If the reaction slows down then the collapse continues until fusion of heavier
elements can happen, degenerate pressure can counter it or if neither of those
happen you get a black hole.

>It's literally E = mc^2, but it's not "net positive." It's net zero. Matter
is converted into energy. That's it.

I didn’t ask you how much energy any given unit of mass has, I asked you for a
net positive model for a fusion reaction.

We need to invest energy to make fusion happen then we need to invest more
energy to keep the reaction going.

So again I understand where the “excess” energy comes form when two protons
fuse into a neutron, however proton fusion isn’t spontaneous and it requires
you to expand energy to bring them close enough so they could fuse.

Now in say hydrogen plasma you need to overcome a lot of forces to do that,
and more so when the reaction starts since the energy release wants to expand
the plasma outwards what I want is to see a net positive model for this
reaction.

So far I only hear crickets.

~~~
azernik
Might as well ask where the energy comes from the burn wood - each oxidation
has an activation energy which must be paid before the heat from burning is
released.

However, as long as the released energy is greater than the activation energy
(the reaction is _net_ exothermic), some of the excess energy from each
reaction (through heat) goes into powering future reactions. Which is why
physicists talk about "ignition" \- there's a very strong analogy to igniting
a fire with an initial spark of energy.

> So far I only hear crickets.

So far I see lots of people spending a lot of time explaining high school
physics to you. Do at least try to be polite while this is going on.

~~~
dogma1138
Again you seem miss understand I’m not saying that the Sun extracts energy
from gravitational potential but you cannot have stellar fusion without
gravity it’s not part of some initial condition that is then irrelevant it’s a
constant factor.

A good analogy would be walking it’s very easy to do so on earth under
constant gravity but it doesn’t mean that you extract energy form
gravitational potential which is when you stand on the surface of the earth is
for all intents and purposes zero. However if you switch gravity off you
wouldn’t be able to walk.

If we want to simulate gravity in say space there will be an expense to that
in terms of say rotating a drum which means we need to expand some energy to
do so.

Now with fusion it’s exactly the same we need to bring in the elements into a
condition in which fusion can happen and we need to sustain the reaction by
not allowing it to expand and cool.

This requires energy so instead of trying to explain me high school physics
you might want to answer my original question do we have a model which allows
for the extraction of energy form a fusion reaction that does not cool it down
until it stops. And does this model including the confinement energy is energy
positive or not.

I didn’t asked where the energy released form the fusion comes form it’s a
stupid question all energy in the universe came form a single source that is
the Big Bang there is no more or less of it in the universe today than there
was 15 billion years ago.

~~~
theothermkn
Must. Not. Pick. At. Scab...

> Do we even had a model for Fussion that is energy poasitive? The only Fusion
> reactors we know to work, work by converting gravitational potential energy
> into light/heat through fusion this is how stars operate.

> All fusion reactions so far require an external input of energy not only to
> start them but often to sustain them and even those which are self
> sustaining for a short period of time grind to a halt once you try to
> extract energy from the system.

That was your original question. It contains, as everyone is aware, your
original statement that stars work by converting gravitational potential
energy into light and/or heat through fusion. This claim is patently
incorrect. It is false. It is misleading. It is a red herring, and a canard.
You seem susceptible to it, for some reason. My only advice is to just set it
down, over there, and don't play with it. The only winning move is not to
play.

> And does this model including the confinement energy is energy positive or
> not.

Sigh. There is no "confinement energy." This is a physics-sounding phrase that
you seem to have coined. Set "confinement energy" down over there next to your
original question. It's poison.

> This requires energy so instead of trying to explain me high school
> physics...

Sigh, again. How much energy, quantified, in the mathematical language of
physics and engineering? How much in comparison to the energy released
quantified, in the mathematical language of physics and engineering? While
these are technical questions, the answer, given by physicists and fusion
researchers since well before ITER, is: "We get way more energy out. Full
stop. Solved problem. Tokamaks work, with a lower size limited by magnet
_technology_ , but not by first law _physics._ (Implicitly, people who
question this at length are cranks.)"

You simply have no basis to go around demanding "a model." If it hit you in
the face, you wouldn't recognize it. You, personally, can't quantify this
"require[d] energy." You, personally, therefore have no reason, other than
obstinance, to think you have some relation between the amount of energy
released from a fusion reaction and the energy necessary to create the
conditions for fusion. None. No other reason. Pure mulishness. The question is
dumb. You are dumber for having asked it, and I am dumber for having read it.
It is contagiously, toxically dumb. Please stop. There is no longer any nice
way to say any of this to you.

And the one thing you need more of is high school physics, not less.

> ...do we have a model which allows for the extraction of energy form [sic] a
> fusion reaction that does not cool it down until it stops[?]

Which fusion reaction? Where? So, you can set a solar panel up to do
"extraction of energy" from the Sun. Experimentally, this has not shut down
fusion in the Sun. So, yes? We have a model? Further, there's no way to _not_
"extract energy" from a fusion reaction, whether or not that "extraction"
shuts it down. You, and I, generally exist at a lower temperature than fusion
reactions. Ergo, we are extracting energy via radiation from every fusion
reaction in the Universe, via heat transfer.

> If we want to simulate gravity in say space there will be an expense to that
> in terms of say rotating a drum which means we need to expand some energy to
> do so.

There's a legitimately beautiful and elegant answer to all this energy
nonsense in that thought experiment. The answer leads to even more beautiful
math about energy, momentum, ground states, and stability. It would be wasted,
here.

I'm going to go have a shower, and maybe a drink. This has been an awful waste
of time.

~~~
dogma1138
>That was your original question. It contains, as everyone is aware, your
original statement that stars work by converting gravitational potential
energy into light and/or heat through fusion. This claim is patently
incorrect. It is false. It is misleading. It is a red herring, and a canard.
You seem susceptible to it, for some reason. My only advice is to just set it
down, over there, and don't play with it. The only winning move is not to
play.

That was a gross simplification but technically correct, without the constant
force of gravity which confines the gas there is no sustainable fusion
reaction in stars.

On earth we replace gravity with magnetic confinement.

>Sigh. There is no "confinement energy." This is a physics-sounding phrase
that you seem to have coined. Set "confinement energy" down over there next to
your original question. It's poison.

If I phrase it as the energy required to maintain the magnetic confinement
field in a fusion reactor in order to maintain the fusion reaction would it be
better? Because now you are arguing semantics.

>Which fusion reaction? Where? So, you can set a solar panel up to do
"extraction of energy" from the Sun. Experimentally, this has not shut down
fusion in the Sun. So, yes? We have a model? Further, there's no way to not
"extract energy" from a fusion reaction, whether or not that "extraction"
shuts it down. You, and I, generally exist at a lower temperature than fusion
reactions. Ergo, we are extracting energy via radiation from every fusion
reaction in the Universe, via heat transfer.

Which is exactly my point the, what confines the nuclear reaction in the sun
is a complex process which involves the inward pull of gravity this is what
prevents the sun from blowing out until it cools down, you constantly keep
ignoring this fact.

On earth we use magnetic fields those magnetic fields require power now I
agree that in a reaction that is an equilibrium there is no work between the
field and the plasma as both of them are opposing and equal but we still need
to power that field if we power it by the excess heat from the fusion reaction
the question is then is there any other excess heat that can be used to
generate electricity in addition to what is required to power the magnetic
field, and this is with a hypothetical 100% efficient model.

