f the NASA emdrive performance of 1.2 millinewtons per kilowatt.
8.3 TeraWatts of power would be needed to provide 10 million newtons of thrust to accelerate a 1000 ton space-craft at 1 gee of acceleration. We have no power source that could generate 8.3 TeraWatts for a 1000 ton spacecraft.
If EMDrive performance increases with the Q-factor as some have theorized, then we could tune the cavity and make it superconducting. If we take the NASA EM-Drives and pump the Q factor to ~30 million, then about 2 GW power is needed for the sustained 1 gee thrust.
Theoretical nuclear fission reactors could power such a spacecraft. Gas-core or magnetic collimator fission-fragment reactor might be work but have been theoretically designed and have very limited experimental development.A fast-spectrum reactor with a thermal output of ~ 6 GW and ~35 % thermal conversion efficiency would be a first pass design to supply the power. Assuming ~100% burn-up the fuel used over 20 years masses 4.2 tons. If the reactor mass was limited to ~200 tons, then it'd need to supply power at 10 kWe/kg of reactor mass, which is very high performance.