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Z Machine Makes Progress Toward Nuclear Fusion
sciencehabit writes Scientists are reporting a significant advance in the quest to develop an alternative approach to nuclear fusion. Researchers at Sandia National Laboratories in Albuquerque, New Mexico, using the lab's Z machine, a colossal electric pulse generator capable of producing currents of tens of millions of amperes, say they have detected significant numbers of neutrons — byproducts of fusion reactions — coming from the experiment. This, they say, demonstrates the viability of their approach and marks progress toward the ultimate goal of producing more energy than the fusion device takes in.
In other words they aren't even remotely close to a meaningful breakthrough. Nothing to see here, move along...
Progress is progress and "breakthrough"s only exist in the minds of the people who weren't paying attention to all the incremental steps that created them.
A factor of a hundred here, a factor of a hundred there, and pretty soon you're talking about orders of magnitude.
Blasphemy is a human right. Blasphemophobia kills.
Exactly in fission you are trying to hold the reaction back. That's why it can run away. Think of it like holding a dog against a leash. It the leash breaks the dog is gone.
Fusion is the opposite. It's like trying pull a mule. You can barely get the thing moving.
... A high school student working on a Farnsworth-Hirsch Fusor for their science fair project, capable of accelerating tenths of amperes, detects significant numbers of neutrons-byproducts of fusion reactions-coming from the experiment. This, they say, demonstrates the viability of their approach and marks progress toward the ultimate goal of producing more energy than the fusion device takes in.
Or not.
-- Insert witty one-liner here. --
uh... there's actually no minimum size for a star to collapse from to form a black hole. The only real requirements are that the star reaches the Fe phase at which point nuclear reactions become endothermic and the core collapses, rebounds at the neutron threshold, collides with the plasma outer shell sending that out and imploding with enough force to collapse again - this time beyond the neutron threshold. For a star with a start mass of ~1.4Msol, this would mean the core containing at least 50% of the stellar mass (0.7Msol) collapsing to a neutron sphere no more than 11 miles in diameter. The average mass of a Milky Way black hole is estimated to be 10Msol (or a start mass of 20Msol or thereabouts). The Fe+He phase (also known as the neutrino phase) of stellar evolution is estimated to last somewhere in the region of twenty millionths of a second and produces all the heavier elements in the universe in a supernova explosion. Less massive stars will die less violently, shedding outer layers over time and/or simply cooling. Few if any with masses less than about 0.75Msol will even reach the Fe phase before simply expiring. I do subscribe to the notion that Jupiter is a failed star, particularly given that it does radiate more than it receives from Sol.
Political debates have me rolling my eyes so much I think I got optical whiplash. I should sue. - Foamy The Squirrel
Jupiter radiates more heat than it recieves not because it is a failed star, but because of gravitational contraction and something called differentiation, which is the layering of lighter and hevier elements sorting out (like dressing separating after you shake it).
The notion that Jupiter is radiating excess heat and, therefore, is a failed star is a tempting idea, but it is far from being a star. By an order of magnitude or three.
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