Thorium vehicle will run 100 years on 8 grams of fuel

[PamW]

41. Look at momentum per unit energy

longship,

For a material; momentum p = mv ( product of mass and velocity ), while energy is 1/2 mv^2 ( one-half mass times velocity squared ).

For photons; the relation is E = pc ( Energy = momentum time c ).

So compute the amount of momentum ( which is what you want ) per unit energy ( which is what you pay for ).

For a material; p/E = (mv) / (1/2 mv^2 ) = 2/v

For photons; p/E = p / (pc) = 1 / c

Since 2/v is always greater than 1/c for v < c; you get more momentum per unit energy with material than you get with photons.

PamW