If we can get unit-costs on those pellets down, that sounds like a great starting point for high-speed spacecraft propulsion.

Not in the Expanse "pellets explode and produce electricity" way but in the Project Orion "explode nuclear bombs behind a shock absorber and ride the shockwave" way [1]. Just that this allows you to build much smaller and more manageable spacecraft (important since you probably still want to reach orbit with more traditional propulsion)

1: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...