Launching an NTR from an airship on Mars

Another way to get to space from Mars: by using a nuclear thermal rocket. If you were to use the same rocket to get from Earth's atmosphere to LEO, you can also use it in order to get to space from Mars. All of the characteristics for the rocket can match up pretty well with what the requirements are for getting off Mars. You need a way to launch it and I was thinking of using an airship. Radioactivity can be blocked with more shielding than can be used on Earth.