Antimatter Fuel Calculator

    How much antimatter would a spacecraft need to reach a given fraction of the speed of light? Uses the relativistic photon-rocket equation.

    Ship Parameters

    kg

    100.00 t

    100% = ideal photon drive (all annihilation energy becomes thrust)

    Antimatter required
    5.28 t

    Plus 5.28 t of ordinary matter

    Mission Breakdown

    Lorentz factor (γ)1.005
    Mass ratio1.11 : 1
    Total launch mass110.55 t
    Total propellant mass10.55 t
    Annihilation energy9.486e+20 J

    Photon-Rocket Equation

    For an ideal photon rocket where antimatter annihilation produces collimated radiation as exhaust, the relativistic mass ratio is:

    minitial / mfinal = √((1 + β) / (1 − β))

    where β = v/c. Reaching just 10% of c requires a mass ratio of about 1.1 — but reaching 90% needs ~4.4, and 99% needs ~14. These ratios assume one-way acceleration only; a brachistochrone (decelerate at destination) squares the ratio.

    Why antimatter?

    Chemical rockets convert ~10⁻⁹ of their mass to energy. Fission converts ~0.1%. Fusion ~0.7%. Matter-antimatter annihilation converts 100% — making it the most energy-dense propellant physics permits.

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