Inertia’s fusion target design models 26 to 43 times gain

The commercial design Inertia has modelled keeps NIF’s hohlraum-and-capsule architecture but swaps NIF’s gold-lined depleted-uranium hohlraum for lead

(Image courtesy of Lawrence Livermore National Laboratory)

Inertia Enterprises has published the physics basis for its fusion target design, the fuel target at the centre of its commercial power plant, in a preprint written with Lawrence Livermore National Laboratory. Simulations anchored to National Ignition Facility experiments project a target gain of 26 to 43 from a 10 MJ laser, with two to four times the ignition margin of NIF against the imperfections a power plant would introduce.

What the fusion target design milestone actually defines

Inertia placed this result first on its Phase I roadmap of ten items. The roadmap defined it as a target gain above 25 and more than 250 MJ per shot, demonstrated through a Virtual NIF Shot run on the design codes LLNL applied to ignition. The company now says it has completed the task, making it the second roadmap item it has announced as done, after the fast fuelling result in August 2026.

The 25x threshold ties to about 250 MW of grid electricity for initial plant operation, and the preprint puts the modelled range at about 26 to 43. Those gains correspond to fusion yields of 265 to 427 MJ, calculated with the HYDRA and LASNEX codes and benchmarked against NIF ignition experiments, with Inertia describing the upper end as the product of early design optimisation. Inertia says the results are being prepared for submission to a peer-reviewed publication.

The modelling ran under Inertia’s partnership with LLNL, announced in April 2026, using what Inertia describes as LLNL’s virtual shot model, which is built on the codes used to design the NIF ignition experiments.

How the fusion target design keeps its margin against imperfection

Larger driver energy and fuel mass underpin the ignition margin, and the preprint reports substantially larger fuel masses than current NIF ignition experiments, a burn fraction of about 40% and a stagnation areal density of about 3 g/cm². Inertia says it deliberately operates further from the ignition cliff than NIF does, which lets the target tolerate imperfections without falling below the ignition threshold.

In Inertia’s modelled case, the commercial design assumes rapidly formed, rougher DT ice, with grooves severe enough to stop a NIF-scale target igniting, yet the larger design still ignites and burns fully. Ablator quality follows the same pattern. Small voids in the high-density carbon ablator can seed jets that mix ablator material into the fuel, but in representative simulations the larger capsule shows virtually no mixing or yield loss.

The August fuelling announcement carries that tolerance into manufacturing, with Inertia and LLNL cutting formation time for the DT layer from several days at NIF to two to three hours. Inertia expects the larger design to allow times below one hour, and LLNL’s Chris Weber said a groove that troubles NIF is acceptable at Inertia’s scale because defects damp in proportion to ice thickness. The company presents both results as following from the same design choice, a larger target that tolerates more imperfection.

The virtual assessment also includes changes intended to lower manufacturing cost, replacing NIF’s gold-lined depleted-uranium hohlraum with lead and modelling a capsule support intended to survive injection. On the laser side, the planned architecture uses thousands of individual beams whose pointing and power balance can be adjusted through the pulse, which the preprint says manages implosion symmetry and laser-plasma interactions.

Mike Dunne, co-founder and CTO, says the calibrated models give exact requirements for targets, laser system and integrated physics design. He says that lets the company trade fabrication speed against component tolerances, drawing on expertise from across industry, and gives a target mass manufacturing programme a known endpoint.

What the laser efficiency cases mean for net power

In Inertia’s model, ten shots per second at the baseline gain of about 26 gives about 290 MWe net at 12% laser efficiency, rising to 450 MWe at 15%, so three points of laser efficiency are worth 160 MWe of net output. At a gain of about 43, the same architecture gives roughly 1.05 GWe net and more than 3.4 GWth of process heat at 12%, or 1.3 GWe and 3.6 GWth at 15%.

Inertia points to diode-pumped solid-state lasers that have recently demonstrated efficiencies above 20%, which it says shows higher efficiencies are within reach. The roadmap’s own worked example assumed an initially 12% efficient laser and roughly 45% thermal-to-electrical conversion, and its laser items cover diode cost, amplifier efficiency at 10 Hz and optics durability.

Where the modelled tolerances get tested

Inertia said in its August fuelling announcement that the exact level of target tolerance will be tested in an early phase of plant commissioning, building from a baseline of targets made to NIF specification. The roadmap describes the remaining Phase I items as measurable engineering and supply chain developments, and Jeff Lawson, co-founder and CEO, said in August that the fuelling result was one of several the company would announce in the coming months.

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