I'm not trying to claim that these particular projects will succeed. I'm just saying that some VCs are in fact funding the sort of high-risk breakthrough physical technologies that the article claims are not being funded.
But a nitpick on LPP: wall engineering isn't really an issue for them since they're attempting boron fusion. Like Helion they're also planning direct conversion, since the output is a pulsed beam of charged particles. I once asked Lerner why they don't start with D-T and he had an argument that their concept actually works better with boron (don't remember why).
Of course wall engineering is going to be a problem with boron fusion. Any very hot plasma will emit photons, and H-11B plasmas will emit them even more than DT plasmas (because the rate of emission increases rapidly with the charge of the nuclei). In fact, a H-11B plasma will normally emit photons faster than it can reheat itself from fusion. LPP makes noise about making tiny knots of plasma that are so dense and ultramagnetized that this doesn't happen -- but as those knots expand, the supposed effects that suppress radiation would die away, and out would pour the photons.
The reactor would only be about 5MW, and the wall of the reactor core can be however far away it needs to be to not get melted by x-rays. It's not like it's surrounded by superconductors or breeding blanket, it's just vacuum containment. Generally it's neutron radiation that's considered difficult to deal with, and there'd be little of that.
And the reactor won't produce net power at all unless they're right that bremsstrahlung will be suppressed long enough by the plasma's magnetic field. If it is, then most of the energy will go into the alpha particle beam.
The reactor is described to be 5 MW average output. But if it's very bursty the instantaneous power will be far higher. Damage to the wall will be determined by heating of the surface by these flashes (and possibly mechanical damage from shocks induced by vaporization in that surface layer). Keeping the instantaneous power low enough to avoid damage could make the reactor unacceptably large.
That is a central problem with fusion: the volumetric power density of fusion reactors sucks. It's not a trivial criticism, it's an economic showstopper.
LPP's concept has other problems, of course, like the aspirational physics of those putative 1000 T plasma knots, and direct conversion by Handwave Engineering.
But a nitpick on LPP: wall engineering isn't really an issue for them since they're attempting boron fusion. Like Helion they're also planning direct conversion, since the output is a pulsed beam of charged particles. I once asked Lerner why they don't start with D-T and he had an argument that their concept actually works better with boron (don't remember why).