[om42]

Air bearings are expensive and have a very low clearance (talking about tens of microns). The lower clearance raises the issue of safety. If I remember correctly, to get that to be greater than tens of microns you need larger compressors and lower operating pressure inside the tube which increases costs and it tougher to maintain.

If you take a look at the SpaceX Hyperloop competition the teams moved away from using air bearings mostly due to the low clearances and the challenges it brought. Maybe on Mars it could be more realistic.

[aidenn0]

I don't know why I didn't think about the clearance; that's a very good point. Does the low clearance affect maximum roughness and slope of the track as well?

[edit]

Did any of the hyperloop competitors try the addition of a skirt, similar to the UK's old hovertrain?

[edit2]

Googling for "hyperloop skirt" found this article: https://waset.org/publications/10004923/conceptional-design-... which suggests a 2cm clearance, but no clue if that's a reliable source.