http://apcnasa3ozl2j74htizuzba5b6nhugbg2qze2nrz43siunkct555fpid.onion
Finally, matter-antimatter annihilation with electrons and anti-electrons (positrons) has an energy density of 9x10 16 J/kg, but the annihilation products are high-energy gamma rays which are essentially useless for propulsion because they can not be directed to produce useful thrust.