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Comment by Razengan | Hacker News Reader

It's an scary thought: It may not be that intelligent life is so rare in this universe, but rather that it is very rare for intelligent life to sustain itself for long enough to colonize the galaxy..

For all that we've learned and have built, we still don't have a Plan B. No foreseeable alternative to this planet if it goes belly up, one way or the other.

What's worse, we're still not over our politics and economics and artificial borders; all the things that keep us rooted here and actually headed backwards into primitivity.

Even if Elon Musk or some other zillionaire launches a successful extraterrestrial habitation program, sooner or later it will fall prey to the same old national interests from back home.

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> For all that we've learned and have built, we still don't have a Plan B. No foreseeable alternative to this planet if it goes belly up, one way or the other.

It's not like it's easy either. Sending massive amounts of stuff in space requires a lot of energy, and terraforming would require even more massive investments if we were to settle on any other planet even close to us.

Which is exactly one of the most compelling reasons to speed up fusion research. Near unlimited power changes everything.

What barriers prevent us from realizing "near unlimited power generation" from fusion? What haven't we figured out yet? Are there any "hard limits" imposed by physics in the way of energy-surplus fusion (analogous to the constant "c" for information propagation rate?)?

Well, one gets only so much energy out of every reaction. But this is such an absurd amount of energy that it's hardly the technological bottleneck. The nuclear physics of fusion is the easy part.

To get a burning fusion reaction, you need to satisfy the Lawson criteria [1], which can be seen as a constraint on the "confinement time", into which goes all the plasma physics. Empirically and theoretically, the most important factor in maximizing the confinement time is the strength of the magnetic field. We can just about able to create magnets that are strong enough, but they aren't strong enough structurally: the force they exert on the plasma is enough to break the magnets themselves.

From what I've seen and heard, the two most important bottlenecks are structural strength of strong (superconducting) magnets, and the robustness of blanket material to neutron bombardment.

[1] https://en.wikipedia.org/wiki/Lawson_criterion

The fact that fusion is not ready yet might be a good thing. We still don't realize how precious our remaining fossil fuel reserves are, and we'd probably squander the energy that fusion provides.

I've always said that fusion won't save us from the coming global energy crisis, because it's coming too soon. Maybe that's good; we'll learn to appreciate it when we have it.

Maybe we can look into exotic sources like lightning, even if it may not be as conventionally usable according to our current understanding.

Say, send up baskets of some materials in a balloon into storm clouds, have the immense burst of power in lighting strikes fuse them together into some form of fuel that we can then tap for energy.

I think you are being downvoted because lightning has very high power but very low total energy, and is way too unpredictable (apart from a few special places) even if it did have enough energy to be useful.

Yes, that's why I offered that maybe we could think out of the box to harness it in an indirect manner. Considering how it forms fulgurite [1], what if we used to form something that can be "burned" for energy?

I find it hard to believe that this awesome force cannot have any applications for man.

[1]: https://en.wikipedia.org/wiki/Fulgurite

> I find it hard to believe that this awesome force cannot have any applications for man.

The thing is, it's not that awesome, especially compared to the amount of energy consumed by humanity. Lightning is just another manifestation of solar energy. A tiny fraction of it, at that.

So the awesomeness comes from the power[0], measured in watts. We like power, as evidenced by our (humanity's) building ever-larger power plants, but what we really need is lots of bulk energy[1]. Energy is the integral of power over time, measured in joules. Think of power as how concentrated energy is into a small amount of time.

Lightning bolts may deliver up to 10GW of power, but the total energy is still only ~1GJ (based on a bit of searching[2][3]; I'll note that some "napkin math" estimates by some bloggers drastically overestimate the duration of an average lightning strike). According to [3], "all the lightning in the entire world could only power 8% of US households. At best." You also have to consider how incredibly expensive it would be to build a lightning rod and capacitor bank at every single possible lightning strike site.

So even if lightning's awesome power can melt a few rocks, it still can't run our cars or heat our homes, because there's not enough energy.

[0] https://en.wikipedia.org/wiki/Power_(physics)

[1] https://en.wikipedia.org/wiki/Energy

[2] http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightnin...

[3] http://www.realclearscience.com/blog/2012/05/could-we-harnes...

> I've always said that fusion won't save us from the coming global energy crisis, because it's coming too soon. Maybe that's good; we'll learn to appreciate it when we have it.

If we survive it. If the crisis hits so hard the technological civilization collapses, we ain't rebuilding it any time soon. All the easily accessible high-density energy sources are long gone.

You don't need "massive" amounts of stuff to start a colony on Mars. We could have a small one for tens of billions of dollors and a pretty big one for a few hundred billion dollars. That is not very much money in the big scheme of things, but political priorities are not on space flight.

If we can't avoid ruining a planet we evolved to live on, do we really deserve a plan B?

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