How can I "force" my body to go to sleep? Total suffering...

I work in television. And I work both shifts, either have to be at the station at 4 in the morning, for the first news broadcast at 5, and get off at 1 in the afternoon, OR 3pm to midnight. The second shift is not a problem, but I can’t make my body go to sleep at around 7 or 8 at night to get up at 2:30 am. I sleep for may be an hour – and then I suffer all morning/day long at work. I have HUGE responsibility at work, requires high concentration and attention. We basically make tv happen, and if I’m not alert (which I rarely am), then something will go wrong. So far I’ve been lucky, but I literally fall asleep infront of the prompter. Anyone else works swing shifts? How do you fall asleep when you’re “suppose” to?