Ripstop Nylon is a textile used in preventing a catastrophic tear. Let's take your pants as an example. A light weight fabric, nylon can tear easily on that splinter in the seat of your chair. A simple snag can tear a small hole in your pants. Now, If we were to try and use this fabric under stress, say bending over, it can fail catistrophically- tearing it until it hits a seam. This is a bad thing when it happens to your pants, but a potentially fatal one if it happens in your parachute. To prevent this, thicker fibers are interleaved with the normal ones like so:
--I||||||I--
==I======I==
--I||||||I--
--I||||||I--
--I||||||I--
--I||||||I--
==I======I==
--I||||||I--
where I and = are the stronger
fibers, and - and | are the normal ones.
These grids are spaced at whatever interval is best for the application. In a kite they are often in a 1/4" grid. On a parachute, they are tighter, say a 1/8" grid. This prevents the tear from spreading beyond the first unsevered strong fiber. Example:
|--|--|--|
|--|xxxxx|
|--|--|--|
where | and - are the strong fibers, and x is the rupture. Saving you from a
parachuting death or the equally fatal exposure of
your tattered and holey undergarments to the world.
This is just a stopgap measure, as the strong fibers will eventually break under stress and the rupture will spread... but much much slower than if it weren't there.