>>Consider the sliding pole "escape system" on the Shuttle. It provides a narrow window of opportunity starting at about 50,000 feet. When you get much above 35,000 to 40,000 feet, you need either a pressurized cabin or a pressure suit to keep from passing out. If they decide to attempt an escape, it could begin with opening the hatch above that altitude. The suit helps them stay functional and provides some measure of protection against the wind blast.<<

A little clarification: The escape procedure begins at about 40K ft with hatch jettison, followed by crew bailout from 30K down to (hopefully) 10K. Bailout requires a stable glide and airspeed of 300 kt or lower.

The ACES suit is now a full pressure suit, providing protection even in a full vacuum.

-Kim-