Scientists made a "nuclear foam" fuel as light as air that could actually get us into deep space in a hurry.
arXiv · March 18, 2026 · 2603.15673
The Takeaway
Traditional nuclear fuels are heavy and trap energy as heat, but this graphene-based sponge is so sparse it allows powerful atomic fragments to shoot out directly. This design could enable 'fission fragment' rockets that are far more efficient and faster than anything currently possible, potentially opening up the outer solar system.
From the abstract
Graphene hydrogels were created and loaded with uranyl nitrate or thorium nitrate and freeze-dried to produce graphene aerogel nuclear fuels. These aerogels had densities between 0.018-0.035 g/cm3 and consisted of ~7.3 +- 0.5% uranium/thorium by mass. The ultra-low density of the aerogels allows for high energy ions to escape the fuel particles without depositing all their energy as heat, as is typical in nuclear fuels. Their measured alpha activity was ~16 pCi/mg, which could be enhanced up to