How is it possible for military drones to fly for many hours without refueling?
This is a Predator drone, MQ-1. View pictures in App save up to 80% data.
It weighs 500kg empty, has a 105 horsepower rotax engine, 55 feet wingspan and a top speed of 270 kph. Its longest recorded flight was 40 hours 5 minutes, probably by flying very slow and using its big wings to assist like a glider would. Fully loaded with weapons this drone only has a range of 1200km though. So in recon mode it has a camera and nothing else, and can fly for many hours. In attack mode with a few heavy hellfires it would be done after 6 hours. It's so small it fits in a transport box. View pictures in App save up to 80% data. This is an F-15E. View pictures in App save up to 80% data. It has a top speed of close to 3000 kph. 10x more than a Predator. It also has a ferry range of 4800km, or fully loaded 1900km. That's more than a Predator. And an F-15 could fly just as slow as a Predator, it could handle 270 kph without falling from the sky. That would give it a 7 hour flight time.
So an F-15E could fly longer than a Predator. But it doesn't need to. It has a different role. It comes in fast, unloads hell on whatever needs killing that day, and leaves again. A Predator comes in slow to not be detected and shot down, and usually kills one specific target, maybe a single person or one vehicle. That's it.
But then there's the Global Hawk drone. It's called that for a reason. View pictures in App save up to 80% data.
It's basically a massive cruise missile. It has a range of 22,750 km. Half the world. And with a cruising speed of 500kph it can stay in the air for nearly 2 days. It does recon. It doesn't carry weapons.
So it really depends on what you're looking at. An F-15E has longer range than a small drone that literally fits in a box, while a drone nearly the same size can go halfway around the world.
You build things for a special purpose. Sometimes the purpose is to fly for days to take photos, other times it's to kill things with heavy weapons.