Can Jet Engines Accelerate a Spacecraft in Empty Space?

In summary, in order for a spacecraft to be accelerated, it requires an external force. This force can be created by ejecting mass from the rocket engine, which follows the principle of conservation of momentum. This is similar to the recoil of a gun, where the projectile is propelled forward and the force is felt backwards. In the case of a rocket engine, the spent fuel is ejected backwards to propel the spacecraft forwards. There are two types of jet reactors, one that uses incoming air and one that uses internal propellant, with the latter being more suitable for use in space. The force of acceleration can also be measured by the mass flow of the ejected gas and its velocity.
  • #1
johncena
131
1
Imagine we are in a spacecraft which is moving with a constant velocity in empty space. If we are not influenced by any gravitational forces, and if we restart the engine, will it be accelerated ?
 
Physics news on Phys.org
  • #2
I would hope so. Without acceleration, how would you be able to control your speed and direction? Without acceleration, it would be difficult to control our satellites. Also, docking with the space station would be a real pain.
 
  • #3
How it can be accelerated without an external force ?
 
  • #4
I don't know. Ask someone at NASA. I just know that you can't change direction or speed without acceleration.
 
  • #5
johncena said:
How it can be accelerated without an external force ?

The rocket itself provides the external force by ejecting mass.
 
  • #6
The rocket-and-exhaust as a closed system will maintain its centre of mass. Exhaust goes left, rocket goes right. CoM remains in place.
 
  • #7
By conservation of momentum. If gas is ejected from the back with a momentum, the ship will feel an increase of the same mometum but to the other direction. And by definition, change in momentum over time is force. Suppose you are in space with some rocks in your pocket, if you throw those rocks backwards, you will start moving forward.
 
  • #8
It's the same principle as firing a gun. The propellant ignites, propelling the projectile down the barrel and sending force back along the weapon and eventually into the person holding it. Hence the "jerk" when you fire a gun.

A rocket engine works on the same principle, but instead of a projectile, it sends the spent fuel backwards to propel itself forwards.
 
  • #9
It s the momentum conservation (or motion quantity p=mv), and the same explanation why gun slide recoil.

The mas of gas that the jet engine blow out, multiplied for its velocity, must be the same of the mass of the space ship, multiplied for the spaceship velocity.
mv=MV

You have two kind of jet reactor, esoreactor (typical planes), where you have that there is also an incoming mass of air, and endoreactor (rocket kind), where all the propellent is inside the rocket and there is no incoming mass. The first can't work in space, as there is no air.

You can also measure the speed force as the mass flow of ejected combusted gas and the gas velocity F=m'*v.
 

FAQ: Can Jet Engines Accelerate a Spacecraft in Empty Space?

1. Can objects accelerate in space?

Yes, objects can accelerate in space. According to Newton's second law of motion, an object will accelerate when a net force is applied to it. In space, there is no air resistance or friction to slow down objects, so they can accelerate for longer periods of time compared to objects on Earth.

2. How is acceleration in space different from acceleration on Earth?

Acceleration in space is different from acceleration on Earth because there is no air resistance or friction in space. This means that objects can accelerate for longer periods of time and reach higher speeds in space compared to on Earth.

3. Do you need fuel to accelerate in space?

Yes, you need fuel to accelerate in space. In order to accelerate, a force must be applied to an object, and in space, this force is typically provided by rockets or thrusters that use fuel to generate thrust. Without fuel, it is not possible to accelerate in space.

4. Can we accelerate to the speed of light in space?

No, it is not possible to accelerate to the speed of light in space. According to Einstein's theory of relativity, the closer an object gets to the speed of light, the more energy is required to accelerate it further. This means it would require an infinite amount of energy to reach the speed of light, which is not possible.

5. Is there a limit to how fast we can accelerate in space?

Yes, there is a limit to how fast we can accelerate in space. This limit is determined by the amount of energy and thrust available. As an object approaches the speed of light, it becomes increasingly difficult to accelerate it further, so there is a practical limit to how fast we can go in space.

Similar threads

Can Sci-Fi Spacecraft Achieve Stable Orbit with Plasma Technology?
Replies
4
Views
1K
I How does an object know how far to move when it's moving?
Replies
7
Views
1K
Parabolic Pressure Distribution in a Jet
Replies
8
Views
2K
I Does a rotating accelerometer moving linearly measure linear velocity?
2
Replies
47
Views
1K
B Understanding Average Velocity in Linear Motion with Constant Acceleration
Replies
1
Views
1K
What is the fastest speed we can travel in space?
Replies
5
Views
2K
I Stuck in understanding Newton's 3 laws
Replies
18
Views
2K
B Does weight affect the acceleration of an object?
Replies
9
Views
1K
Orbital mechanics: is ballistic capture possible without acceleration?
Replies
7
Views
1K
In circular motion - centripetal acceleration is never there
Replies
18
Views
2K

Hot Threads

Recent Insights

Back
Top