<6 hours of sleep each 24 hour period but the 6 hours does not have to be consecutive.

Hell, I've worked far worse schedules than that. At OTS, we got less than 6 hours a sleep per day for 3 straight months. When I worked rotating shifts, I had a schedule that was far worse than that for 17 months. It was the equivalent of getting in a plane every other day and going 1/3rd of the way around the Earth. I called it "perpetual jetlag." We called them "double-backs", such as getting off of a mid shift at 0800 and having to be back at work for a swing shift at 1600 the same day. We worked 6 shifts in 5 days, then had 2 days off.

Funny thing, since working that schedule, I've never been bothered with jet lag.