It's amazing how simple and straightforward an idea can sound like in hindsight, but it this actually possible? I've always assumed that it takes more energy t

It's amazing how simple and straightforward an idea can sound like in hindsight, but it this actually possible? I've always assumed that it takes more energy to fly a drone than to charge it. So you wouldn't be able to supply enough energy during flight to charge it. Otherwise why would a drone need 1-2 hours of charge time for a 15 minute flight? How would that 15 minute flight last 1-2 hours of flying to charge the battery fully for another 15 minutes of flight? The numbers don't add up.