a_ring ai artificial_gravity asteroid_impact_of_2184 burn coilgun drone_system e electrical_power enceladus_prime exhaust_velocity fission flying hardpoint interlunar kinetic_ammo_storage main_engine mass_driver mining nuclear_thermal_rocket ore_chunks overcooling overheating phage-class_station propellant propellant_economy propellant_tank railgun rcs_thruster reactor ringdive ringroids skyscraper_layout space_station spaceship spaceworthy specific_impulse the_rings thermal_power thrust turbine