This is an experiment I have wanted to do for a few years now but don't have the necessary equipment. GR tells us if you have identical objects with the same weight exactly when they are at the same temperature, then when one object is heated, it will weigh more. This is because the gravitational force depends on the stress energy tensor in general relativity. The stress energy tensor 00 component is the total energy of the body, which includes the rest mass plus the kinetic energy of the object. Temperature differences mean that there is a different amount of kinetic energy in the motion of the atoms of the two bodies. Therefore, if you were to use a motor to spin a massive disk at high speeds while applying heat energy on one side of the fixture (by laser or friction) and remove heat on the other (by laser cooling or some sort of radiator if possible), would this create a force in the perpendicular direction to where the heat is applied since it would effectively be creating an inertia differential which would cause higher acceleration reaction force on the hot side compared to the cold and be equal to the force of the motor required to counter this and keep the disk at a constant speed? Obviously this force if any would be extremely small and difficult to measure but, if it could be scaled up, would be a method of electric propulsion. I can’t find any record of anyone attempting this experiment but it seems like if you had access to laser cooling and extremely sensitive force measurements it would be worth a try.