Jet force

The recoil propulsion or reaction drive is a practical application of Newton's 3rd axiom. The driven object, such as a rocket is accelerated by the recoil with the same force to the front, with the drive medium is ejected backwards.

In space, the recoil drive is the only way to accelerate a spaceship off of massive celestial bodies and strong radiation sources.

Physical background

According to the Newton's 3rd axiom ( action = reaction, also called " reaction principle " or " interaction principle"), are two masses that exert a force on each other accelerated. Thus, for both masses ( after completion of the force ), velocity. According to the definition of the pulse

Result for this case the following relations of the pulses to each other:

(This is for example when the impulse of a rocket combustion products is discharged and the resulting opposite pulse of the missile )

It should be noted that to generate these pulses a defined energy must be available which can perform the corresponding acceleration work. Has a mass a pulse, it has a kinetic energy.

In calculating the proportionate amount of energy applies:

In a continuous process results in the following, known as Rocket Equation, mathematical relationship:

Or also:

Where is equal to the relative speed of the mass support for the actual working load. It should be noted that when this process continues, the support mass decreases continuously and finally only the effective mass with their terminal velocity ( relative to the starting point ) remains.

A stunning effect is established at a ratio of. From this point on the rocket and the ejected mass of their support from a remaining at the starting point of the rocket observer moved in the same direction but at different speeds.

Recoilless actuators which operate on the basis of fluids

Outflow

In the rebound chamber, the pressure ( ) is higher than the ambient pressure (). The medium present in the chamber occurs due to the pressure difference at a certain speed () of the nozzle. Of importance is also the density () of the effluent.

Of gases is to be noted that the density () depends on the pressure and the temperature. This can be ( approximately ) by the thermal equation of state of ideal gases

By conversion after

Calculate.

Since gas density is proportional to pressure, an increase in the extrusion speed can be achieved only by an increase in temperature.

Throughput

Corresponding to the cross-section ( ) of the nozzle, the density ( ) of the exiting fluid and the exit velocity () can be determined which is often also referred to as a mass flow rate ().

Thrust

The thrust () generated can be calculated by multiplying the flow rate ( ) and the exit velocity () of the medium.

Or by replacing

And

We obtain the mass-independent relationship

Required engine power

This does not mean the power ( ), with such a power plant, a mass move ( accelerate ) would, but to generate the power which is required by the respective pushing force.

Or you found this service () on the given flow rate ().

To generate the same thrust in a hypothetical photons drive engine performance would be significantly higher than a conventional chemical rocket engine.

Net power

The actual recoil from such a drive actionable performance ( ) is obtained by changing the formula for the acceleration work:

Here are the initial velocity and the final velocity of the acceleration process dar.

Applications

• Rocket engine