Looking rationally at '1 hr sleep' it should not be a big problem - not good, no, but manageable. Bear in mind said Captain could be slipping on his silkies about 3 hrs after take-off and taking bunk 'rest' from then on, so a reasonable chance to re-charge the batteries - and 3 crew, of course. Every now and then a few of us will have pre-flight rest like his, and manage it.