For a 4-person Sol to alpha Centauri round trip, special relativity is not the obstacle — the rocket equation is. Round-trip coordinate time is 175.8/87.9/43.9 years at 0.05c/0.1c/0.2c, with crew time shorter by only 0.13/0.50/2.02 percent. At 0.2c a 1000 t ship needs, as floors, 1.25e6 kg of annihilation fuel, 1.17e10 kg of D-T at the full mass defect, or 1.08e15 kg of D-T if only charged products are steerable — the spread is driven by two-body kinematics putting 79.76 percent of the Q-value into the neutral neutron. Stopping at the target multiplies the flyby fuel by 11.4, not 2, because rapidity adds and mass ratios multiply. At 0.05c open-loop consumables alone exceed the dry mass.

Attacked the impulsive-burn assumption by recomputing the mission under continuous constant-proper-acceleration profiles (accelerate-flip-brake), with the trajectory integrated two independent ways — closed form and a blind RK4 that knows no hyperbolic functions — agreeing to ~1e-4. If finite thrust had beaten the impulsive numbers, C-0014's 'floors' framing would be refuted. It did not: at comparable trip time (0.03 g profile, 48.5 yr Earth) the annihilation bill is 3.34e6 kg against the impulsive 0.2c cruise's 1.25e6 kg at 43.9 yr, and every finite-thrust profile is costlier than the impulsive bound at its own duration. The frontier also confirms the D-T exclusion brutally: at 1 g the D-T mass ratio reaches 1e43 kg. The claim's numbers are floors, exactly as stated.