The speed @bscholl got this into the store is just one small example of why Iโm confident weโll be able to buy tickets to fly on Overture very soon. Onward @boomsupersonic! ๐ฆ ๐บ๐ธโ๏ธ๐ช๐ป
Happy 250th anniversary to the greatest country on Earth that is built on some of the most important ideas in human history: the individual rights of life, liberty and the pursuit of happiness.
Celebrate this revolutionary thought today and the ongoing pursuit of it!
@peterrhague Fusion-based drives target a similar Isp vs. specific power space and we have the fuel available at scale today and easy to store it. I think this is the natural stepping stone towards antimatter propulsion long term.
My point above was just that an ignited plasma isnโt needed, but youโre right many designs required burning plasmas. The threshold for burning plasma for D-T fusion is a plasma gain Qp = 5 because of the 20/80 split of the fusion yield between alpha particles and neutrons. So, at Qp = 5 the alpha power is the same as the input power and above 5 the alpha power is dominating.
Commonwealth Fusion Systems is building SPARC in MA that should access up to Qp ~ 10 within the next few years, well before ITER even hits first plasma. Even if they underperform by a factor of 2 they still would succeed in producing a burning plasma state. After that theyโre planning to build ARC in Virginia, and have already applied for a grid interconnect for 400 MW.
All other points engineering challenges are definitely true. Even with high gain demonstrated, the next step is the hard work in making it into a power plant that someone wants to buy. But, Iโm pretty confident weโll see pilot plants over the next 5-10 years for multiple concepts and then pushing to FOAKs.
Fun times ahead.
Ignition actually isnโt required for many fusion approaches, but is a typical goal in inertial confinement fusion.
In magnetic confinement approaches, you need sufficiently high plasma gain to reach a desired engineering gain. But most designs arenโt pursuing true โignition,โ meaning plasma gain Qp ~ Pfusion/Pin goes to infinity since the input power Pin goes to zero. Tokamaks are targeting high plasma gain (Qp > 10) and burning plasma conditions (Qp > 5 for DT fuel), but typically not โignitedโ conditions.
The approach within MFE with close to true ignition potential are stellarators, but is not required for a successful power plant.
Helion in particular is pursuing a relatively low plasma gain design point using D-He3 fusion fuel confined by a magnetically compressed FRCs. Since they are leaning strongly into direct energy recovery instead of pushing everything through a thermal cycle, itโs possible to get engineering gain with a lower plasma gain.
Check out this open access article for a deep dive on power balance in fusion systems: https://t.co/EilhHUQ2Qg