Article is capped at 18 views/day so can’t see numbers.

But theoretical cap of energy from a would be something like E_kin = (\gamma -1)mc². Witgout knowing anytging about the mission or engine, a 50 kg probe at a velocity of .9 c means an energy requirement of about 1,0e21 J.

Fusion of H2 to H3 yields about 340e9 J/g meaning we need about 300 million kg of fuel at 100% conversion rate, or a third if we manage He3 reaction.

Realistically heating, engine efficiency, deceleration, vibrational damping and such would probably lower efficiency to at most 40% and we end up at 750 million kg of fuel to propel a 50 kg payload.

Seems unfeasible.