# How does hovering and constant climbing differ?

• B
• day_nite
In summary, the conversation discusses the differences between two scenarios involving a drone that is moving upwards in the y-direction. In both scenarios, the drone needs to reach a net force of 0 and balance forces in order to hover or continue moving at a constant velocity. The key difference between the two scenarios is that in scenario #1, the drone decelerates from a certain velocity to 0 before hovering, while in scenario #2, the drone continues moving at a constant velocity without any change. The conversation also touches on the concept of drag and its impact on battery life for the drone.
day_nite
Hi, quick basic question.

Alright let's say I have a little drone with rotors that only allow the drone to move up and down (in the y-direction). I need help differentiating between these two situations:
1.) I want the drone to start on the ground, accelerate upwards (to a certain velocity), then hover.
2.) I want the drone to start on the ground, accelerate upwards (to a certain velocity), then continue moving upwards at that constant velocity.

Now, simple Newtonian Physics would tell me that in either of these situations, the lift force will have to be greater than the force of gravity to accelerate the drone upwards. Also in both situations, a balance of forces is needed to hover and move with constant velocity. The problem I'm having is that I don't know how to make the drone hover vs continue upwards with constant velocity. I get that I accelerate up, then (once reaching my certain velocity) match F,lift and F,gravity but I don't now if that's supposed to make me hover or continue moving up with constant velocity.

How would I differentiate/achieve both situations?

day_nite said:
1.) I want the drone to start on the ground, accelerate upwards (to a certain velocity), then hover.
2.) I want the drone to start on the ground, accelerate upwards (to a certain velocity), then continue moving upwards at that constant velocity.

There is a difference between these two scenarios: they are identical up to a point, and then scenario #1 does something different (whereas scenario #2 keeps doing the same thing). Can you see what that is?

(Note: it helps if you imagine that you have to move upwards at the constant velocity for a short time after reaching it, in both scenarios.)

Well both involve reaching a net force of 0, that is for certain. I am not 100% certain if I can see the difference, but if I had to guess; Id say in scenario 1 the drone would decelerate (from the "certain velocity" to 0), so that the velocity (momentarily) reaches 0, then apply the F,lift to equal F,gravity which results in it hovering. On the other hand, scenario 2 would involve just instantaneously applying a net force of 0 (f,lift=f,gravity) to continue moving the drone upwards at constant velocity.

Right?

day_nite said:
in scenario 1 the drone would decelerate (from the "certain velocity" to 0), so that the velocity (momentarily) reaches 0, then apply the F,lift to equal F,gravity which results in it hovering

How would you make the drone decelerate? Or, taking a step back: what are the forces on the drone while it is moving upward at a constant velocity? (Note that "constant velocity" means its acceleration is zero.

day_nite said:
scenario 2 would involve just instantaneously applying a net force of 0 (f,lift=f,gravity) to continue moving the drone upwards at constant velocity.

"Instantaneously applying"? If you're just continuing to move the drone upwards at constant velocity, then what had to change?

To achieve this drone deceleration, I would decrease F,lift such that it what less than F,gravity. Thus there would be a net downwards force and a decreasing change in the velocity . Then once velocity decreases to 0, I would increase f,lift such that it is equal to f,gravity so that net forces = 0.

F,lift>mg (Drone up - a>0)
F,lift<mg (drone slows down - a<0)
F,lift=mg (Drone hover - a=0)

in scenario 2, F,lift is initially greater then F,gravity which results in the drone accelerating upwards. Then once I want the drone to continues upwards at constant velocity, I would decrease F,lift such that it equals F,gravity. which means no acceleration or change in velocity.

When i said "instantaneously apply net force of 0, i meant that F,lift would decrease to equal F,gravity

F,lift>mg (Drone up - a>0)
F,lift=mg (Drone up at const vel - a=0)

I hope this is right.

day_nite said:
I hope this is right.

Yes, you've got it.

day_nite said:
match F,lift and F,gravity
If you are concerned with battery life, wouldn't you need to consider the drag factor too? This is not an abstract problem of an ideal ride in an ideal elevator. Moving through the air (upwards) involves work so the vertical force would need to be greater than the weight force alone. Whether or not this is relevant in practice would depend on the actual climb rate.

sophiecentaur said:
If you are concerned with battery life, wouldn't you need to consider the drag factor too? This is not an abstract problem of an ideal ride in an ideal elevator. Moving through the air (upwards) involves work so the vertical force would need to be greater than the weight force alone.
Induced drag is a problem even for hovering. The wing span is not infinite, so there will be an induced down-draft.

jbriggs444 said:
Induced drag is a problem even for hovering. The wing span is not infinite, so there will be an induced down-draft.
Now you mention it, it's hardly surprising is it? So are we real or ideal in this thread? (Question for the OP, I think)

## 1. How do hovering and constant climbing differ in terms of energy use?

Hovering requires a constant expenditure of energy to maintain altitude, while constant climbing uses a burst of energy to gain altitude and then expends less energy to maintain the new altitude.

## 2. What are the differences in aerodynamics between hovering and constant climbing?

Hovering requires a balance of upward thrust and downward force, while constant climbing relies more on forward thrust and lift to gain altitude.

## 3. How do hovering and constant climbing differ in terms of flight control?

Hovering requires precise control of thrust and lift to maintain a stable position, while constant climbing relies more on controlling speed and angle of ascent.

## 4. What are the advantages and disadvantages of hovering compared to constant climbing?

The advantage of hovering is the ability to stay in a specific location for extended periods of time, but it requires more energy and is less efficient than constant climbing which allows for faster and more efficient movement.

## 5. How do hovering and constant climbing differ in terms of their applications?

Hovering is commonly used in helicopters and drones for surveillance and precision landing, while constant climbing is used in aircraft for take-off and gaining altitude quickly.

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