Slide rules, AND Sci-calculators.
Maybe a few computer programs as well.
*shrugs*
I'm not really a sci-type, so trying to crunch numbers makes my head hurt.
;-)
See: Me not knowing that they can produce more than a few strands of nanotube cable.
I hope this isn't too frightening, but I don't mess with the numbers too much, other than some rudimentary calculations.
I know there are formulas, and places where such things can be looked up, so I just go with the vision part of it.
It seems pretty obvious to me, that every objection raised to the idea of a skystalk on Earth, was dealt with to some extent by moving it to Mars.
The way I see it, a space elevator on Mars would make it an economic powerhouse in the growing system of occupied space.