# Rocket acceleration after lauch and during flight

1. Jul 24, 2007

### MIA6

I know mostly that a rocket has acceleration when it is being launched, but does it still keep acceleration when it continues to fly? because my teacher said when this rocket goes up, the speed is decelerating due to gravity. Does this situation only for the rocket that doesn't have acceleration meanwhile, or to the rocket that still keeps acceleration,but i think if a rocket has an acceleration, then it won't be slowed down by gravity.. Hope you can help me out, thanks.

2. Jul 24, 2007

### mathman

It depends on how the fuel supply is handles. A simple rocket will keep accelerating until it runs out of fuel. Then gravity takes over.

3. Jul 24, 2007

### olgranpappy

Once the fuel is spent the accleration (neglecting air resistence and curvature of earth) must be 9.8 m/s^2 directed downward.

4. Jul 24, 2007

### G01

When a rocket is going out of the atmosphere, let's say, it's burning fuel is causing a bigger upward acceleration, than gravity's downward acceleration. So, the rocket has a net upward acceleration.

After the fuel is spent, the only acceleration will be gravity's, and gravity will start to slow it down. If the rocket reached a velocity greater than or equal to what is called the escape velocity, gravity will not be able to pull it back to the planet. Gravity will still slow it down, it just won't be able to make the rocket reverse direction.

5. Jul 24, 2007

### Danger

As everyone has already stated, the rocket will have a positive acceleration for as long as the engine force exceeds 1g. Below that power, a negative acceleration is in effect. (This is assuming an Earth-based launch.)
Some confusion arises in non-scientists sometimes because not everyone realizes that slowing down is also an acceleration, or that a change of direction at constant speed also is.

6. Jul 24, 2007

### MIA6

when a rocket wants to return to the land, does it also have acceleration when it returns? it may be probably bigger than 9.81

7. Jul 24, 2007

### Cyrus

Due to friction, its going to be less than 9.81. The air will slow down the rocket and heat it up. It might come in very fast at Mach 10, but thats velocity, not acceleration. Its going to slow down slower than 9.81 m/s/s.