Would it be unethical to send rapists and serail killers to another dimension or planet?

I always wondered if we humans had the Technology to send people or things to other dimensions or planets would it be ethical to use this type of technology to send dangerous criminals like rapists, Serial killers and war criminals to these places to intend them to live their for an eternity and never let them leave the planet or dimension kinda like for the phantom zone in the Superman comics.