The signs, + , and,  - , are used throughout mathematics and physics in a number of ways,and with several meanings which are often not carefully checked. The plus or positive sign has its initial use in addition in the sense of increasing a pile, of no particular dimensions, by a certain amount described by [...]

I’ll begin with the design of a modest-sized unit that is about half the size of the often-recommended 20-ton elevator carriage, which is imagined to be able to carry a 17-ton payload up in only a week.  (Which I believe impossible)

First, in order to ascertain the starting speed to drive the elevator all the way [...]

By Sykes criteria, the smallest known planet in the solar system would be Ceres, the largest and most massive object in the asteroid belt. Ceres is less than half the diameter of Pluto.

Sykes, director of the Planetary Science Institute is talking about planets across the universe in general, about Pluto and other small
planets in particular, [...]

Ekranoplan vehicles benefit from the peculiarities of aerodynamics close to a surface.  The proximity of the surface both compresses the air under the wing, giving it more lift, and reduces the drag from the wing, making it more efficient.  This effect increases as the surface gets closer and so is the basis for self-stabilisation in [...]