4 ms·

MIT's SPARC has been many times in HN, can anyone knowledgeable tell how does Helion's approach differ from SPARC? Which is supposed to be completed 2025.

dosshell 5y ago
SPARC is a tokamak with state of the art magnets. Helion uses Field-reversed configuration [0]. [0] https://en.wikipedia.org/wiki/Field-reversed_configuration https://en.wikipedia.org/wiki/Field-reversed_configuration
hobscoop 5y ago
SPARC is very important, but it's a physics demonstration facility, not a reactor. Its not going to generate any electricity. CFS (SPARC's parent company) will use SPARC to demonstrate that their magnet technology and plasma physics can be scaled to a reactor -- I think they're aiming for 2030 or 2035 to 'put electrons on the grid' with their 'ARC' reactor. SPARC stands for 'smallest possible ARC'. Compared to CFS's approach, Helion's approach is different in two or three key ways. First, it's a different fusion reaction, which has important engineering consequences. The reaction that Helion wants to use generates fewer damaging neutrons, which makes the rest of the reactor easier to engineer and eliminates several tricky subsystems. Second, it's a different geometry, which does not require huge powerful steady-state superconducting magnets. However, it does require very fast magnets. It's a pulsed machine (they would fire several shots per second; each shot lasts on the order a milliseconds if I recall). So it requires more pulsed power systems and the components may need a different kind of high-repetition lifecycle testing. Third, they want to use a 'direct energy conversion' scheme, which means eliminating the need for gas turbines (i.e. steam turbines) coupled to generators. This is important since the heat exchangers and turbines make up very roughly half the cost of a traditional power plant, so this would allow the electricity price to be lower by about a factor of two!
apendleton 5y ago
Shorter version of my response to a different comment: CFS's approach builds on more mature theoretical foundations; it's basically ITER but with new magnets using technology that has arisen since ITER was conceived. It has a decently high probability of working, but will have practical/operational challenges that some more moonshot-y approaches would avoid (neutron damage to the reactor housing, having to breed tritium, complicated cooling systems, making electricity by boiling water). That's at one end of a spectrum, and as you move away from that, you get to things that involve more unknowns in terms of theory, but, were they to succeed, would avoid many of these challenges. Helion's proposed technology is towards the other, more moonshot-y end of that spectrum, using a less-well-established reactor design that's higher-risk/uncertainty, but should it work, would avoid tritium, wouldn't involve high neutron flux, and wouldn't require steam turbines.

dosshell 5y ago

SPARC is a tokamak with state of the art magnets. Helion uses Field-reversed configuration [0]. [0] https://en.wikipedia.org/wiki/Field-reversed_configuration https://en.wikipedia.org/wiki/Field-reversed_configuration

hobscoop 5y ago

SPARC is very important, but it's a physics demonstration facility, not a reactor. Its not going to generate any electricity. CFS (SPARC's parent company) will use SPARC to demonstrate that their magnet technology and plasma physics can be scaled to a reactor -- I think they're aiming for 2030 or 2035 to 'put electrons on the grid' with their 'ARC' reactor. SPARC stands for 'smallest possible ARC'. Compared to CFS's approach, Helion's approach is different in two or three key ways. First, it's a different fusion reaction, which has important engineering consequences. The reaction that Helion wants to use generates fewer damaging neutrons, which makes the rest of the reactor easier to engineer and eliminates several tricky subsystems. Second, it's a different geometry, which does not require huge powerful steady-state superconducting magnets. However, it does require very fast magnets. It's a pulsed machine (they would fire several shots per second; each shot lasts on the order a milliseconds if I recall). So it requires more pulsed power systems and the components may need a different kind of high-repetition lifecycle testing. Third, they want to use a 'direct energy conversion' scheme, which means eliminating the need for gas turbines (i.e. steam turbines) coupled to generators. This is important since the heat exchangers and turbines make up very roughly half the cost of a traditional power plant, so this would allow the electricity price to be lower by about a factor of two!

apendleton 5y ago

Shorter version of my response to a different comment: CFS's approach builds on more mature theoretical foundations; it's basically ITER but with new magnets using technology that has arisen since ITER was conceived. It has a decently high probability of working, but will have practical/operational challenges that some more moonshot-y approaches would avoid (neutron damage to the reactor housing, having to breed tritium, complicated cooling systems, making electricity by boiling water). That's at one end of a spectrum, and as you move away from that, you get to things that involve more unknowns in terms of theory, but, were they to succeed, would avoid many of these challenges. Helion's proposed technology is towards the other, more moonshot-y end of that spectrum, using a less-well-established reactor design that's higher-risk/uncertainty, but should it work, would avoid tritium, wouldn't involve high neutron flux, and wouldn't require steam turbines.