@Paris
No, I said it takes more energy to stay in place, which is different from being still.
I would imagine hovering is more computationally intensive, since it needs to perform continual computer vision analysis from the downward-facing cameras, and make lots of calculations of how to make micro adjustments to the speed of each rotor to keep it fixed in place. All of which comes at the cost of battery life. When you’re flying straight, the drone has far less to worry about.
@Bela
That might be true, although I would think it has to be doing a similar amount of computation to keep it on a straight line and not deviate from the line. There are some really good answers here in the comments that give solid explanations about how the aerodynamics make it last longer when flying at speed.
A common misperception is that an aircraft in motion is not in a state of equilibrium. An aircraft moving in a constant direction at a constant velocity is in a state of equilibrium just like an aircraft that is sitting on the ground. This actually is how Newton’s laws work. Changing the direction is the only exception. For some reason even climbs and descents of a constant rate are still in equilibrium. I’ve never totally understood why that is the case in regard to climbs and descents. I know the answer to answer it on a test, but it still always feels odd to me. Anyways… I think that what the original person you replied to is referring to is that the hovering drone is not in a state of equilibrium - it’s having to make adjustments to stay in a given location. I’m not sure that this is the cause of the reduced battery life as I’m not a physicist or an aeronautical engineer. Just learned that bit above in flight school. But it certainly sounds plausible. If I had to guess the most right answer (as there are probably many factors) - I think what people said regarding dirty air during a hover is probably the biggest impact. I don’t think a drone in motion generates much lift with its body. But again, this part I don’t know. Just wanted to correct that bit about Newton’s laws and try and perhaps clear up what that other fellow said.
It is the same with helicopters. While moving forward, there is some autorotation and additional lift happening at the blades. Also, it probably helps being in fresh air (with less downward wind) while moving compared to being stationary.
Staying in place, over time, induces a toroidal airflow whose inertia reduces lift slightly. At its most extreme, this is known as ‘vortex ring state’. While this occurs to a much lesser degree in quad rotors than helicopters, it still occurs to a small degree, hurting lift while stationary.
You get a fresh flow of new air when in motion; it makes it easier for the propellers to provide lift as opposed to trying to stay stationary over the turbulent air created by the props.
Sky said:
You get a fresh flow of new air when in motion; it makes it easier for the propellers to provide lift as opposed to trying to stay stationary over the turbulent air created by the props.
Really not how rotorcraft fly. Do a search for transition lift.
@Dany
Do you know what propwash is? Do a search for it.
Sky said:
@Dany
Do you know what propwash is? Do a search for it.
Propwash is the air coming off the propeller. What did you think it was? Were you thinking of vortex ring state?
Sky said:
@Dany
Do you know what propwash is? Do a search for it.
Propwash is the air coming off the propeller. What did you think it was? Were you thinking of vortex ring state?
Yes, and said air is what we call ‘dirty’, making the drones motors work slightly harder to maintain a steady hover. Really not that hard to grasp, especially if you understand translational lift.
Think of it by how hard each individual motor is working. To hover, you need to perfectly balance the energy output of all 4 motors. Say, for simple math, they’re all at 50%. How does a drone move forward? It needs to be at an incline. To do this, the front propellers get to dial it down a notch to 40% effort, whereas the back may sustain their current output. Does this help?