[gwd]

Falling asleep quickly when you're tired I think is something that can be trained; I probably learned it in boot camp, where most days we got only 6 hours of sleep, unless you had watch duty, in which case you got 5 hours; and near the end there was a week where we only got 4 hours. Your body just learns to grab whatever sleep it can.

Re taking short naps: When I was at university, if I needed a power nap, I'd set the timer on my watch for 7 minutes and set it on my forehead; then I'd normally do two of these in a row (so 14 minutes of nap total). Once I got used to it, 1) as soon as I closed my eyes I'd start dreaming 2) I'd frequently have the experience of slowly coming to consciousness seconds before the alarm went off.

But that only works if you're only moderately tired. If you're really sleep deprived, there's nothing you can do but actually take a longer rest.