Comment by dwwoelfel | Hacker News Reader

Comment by dwwoelfel | Hacker News Reader

Parent Full thread

At the end of the video you linked, she accuses the author of The Star Builders of "only briefly mention[ing] the total energy gain and never giv[ing] a number".

I had just started the book when I watched her video, and I counted four separate times where he did mention total energy gain. In one chapter (pg. 142 in my kindle edition), he quotes from a source who lays out the distinction she claims people in fusion research want you to be confused about:

Like First Light Fusion, Tokamak Energy is much more interested in power production than energy breakeven. "Achieving a of one is a scientific goal," Jonathan Carling continues, "but it's nowhere near enough to produce commercial energy, which requires a Q [in the region] of tens." As mentioned previously, Q is the ratio of fusion power out to heating power in. His strong view is that unless other star builders have a credible plan to get to factors of twenty or thirty more power out than they put in, then they're in the science game and not the fusion energy game.

This video by the Improbable Matter channel has a good response to Dr. Hossenfelder's general remarks: https://www.youtube.com/watch?v=KtqC8W0_Ups

I don't think your quote from the book conflicts with Dr. Hossenfelder's criticisms at all. The quote vaguely says "Q = 1 is a scientific goal", then describes Qplasma (and calls it Q): "Q is the ratio of fusion power out to heating power in" (that sounds like Qplasma to me.)

The source in the book is basically saying "Q[plasma] needs to be twenty or thirty times higher than it is to get more _power_ out than you put in", but there's already a term for that: Qtotal. Hossenfelder's claim was that the book never mentions Qtotal and continues the misleading technique of using Qplasma as if it's an indicator of power production (and saying it needs to be 20-30x), rather than using a much more clear term Qtotal to describe "total" energy out vs energy in.

The response video you linked is even worse: They "correct" Dr. Hossenfelder by showing papers that spout Qplasma numbers as just "Q" and talk about how ITER achieves a Q=10. But that's not in contradiction at all with Dr. Hossenfelder; her qualm is how misleading it is to talk about "Q > 1" as if it's producing useful energy when you actually mean "Qplasma > 1" (which does not produce useful energy.)

The response video then goes on to talk about how useful Qplasma is, but that doesn't matter to Dr. Hossenfelder's point, which is that it is unethical to go around touting "We're going to get 10x the energy out that we put in" when you're just referring to Qplasma=10. That's all her video said, and the response is attacking a straw man.

Reply on news.ycombinator.com