In my world, a scientist and engineer by the name of Guoliang Guan successfully uproots and moves a quarter of a million tons of habitat, industry, miscellaneous chemicals, storage containers, rocketry, life-support, and scientific experiments from all across the western hemisphere of Mars - to the bottom of Valles Marineris in two months. This accomplished with a mixture of dug-out roads, gondola lifts, concrete shoots, and a bachelors degree in Engineering. Due to his extraordinary accomplishments, Diego promotes him to Chief Mover of Stuff ... Arbiter of Transportation.
Now, Guoliang is greatful for his promotion and all, but he considers it to be a real pain in the ass if he's gonna have to create new infrastructure every time he needs to move something from God-knows-where to Not-the-bottom-of-Valles-Marineris. So the thinks, "Why make infrasture at all?", and dabbles in a mobile, vehicle-based transportation system. He starts by thinking of the all-terrainiest vechicle of them all; an airship, and reasons out its practicality in a dome at the top of Marineris.
- a useful lift capacity of 50 tons
- Maximum speed of 180 mph
- Operatable at 4 miles above the Martian surface level
- All requirements must be fufilled in relation to Mars
My Question is:
What modifications in Size (dimensions and volume), Lift gas, Structure, and Propulsion to the design of a normal airship (for this question, consider that base to be the Zeppelin NT or LZ-130 Graf Zeppelin II) would be necessary to met Guan's requirements?
Points for factoring in the Martian Enviroment like sandstorms, air density, etc