gas turbine thrust direction

My crystal ball says:

Google Newton's laws. For every action there is an equal and opposite reaction. Air in gets added energy= air out at higher velocity.

How do space ships fly? There's no air for the hot gasses to push against, so it must be magic!

By Newtons Third Law of Motion, every inertial system is in a State of dynamic balance of all the forces acting on the system. Hence, the force of the air flow, F_a, must be in a balance with the force acting on the turbine, F_t, but in the opposite direction, so that the sum of the forces must equal zero, F_a + F_t = F_a + (-F_a) = 0.

By this reasoning the thrust direction can not change suddenly, until and after the direction of the airflow has changed.

In a gas turbine (at least that I was associated with) there are two tilting pad thrust bearings

the main one supports the thrust direction upstream.

The second (much less in capacity) the opposite face of the rotor collar.

The air is entering the compressor inlet, so obviously the thrust (reaction) at the moment is bacwards - this is when the main thrust bearing supports it- initial compresson. Else the load will be transmitted either to the Aux gear Box bearings or the Load gear box bearings.

But see when the GT is charged after it has reached the critical compresson ratio.

Now the condition is more balanced. Though the compressor back thrust still exist, the turbina stage now tries to compensate and the nett thrust is due to the turbine where power is 25% or so more than that consumed by compressor (it is as I remember 1:4 - ie for each MW nett output 4 MWs are generated in turbine, out of which 3 are taken away by compressor - but in case of further question, that is not important since the compressor whatever it takes, gives back in turbine stage in a closed system)

But due to the angles in the turbine stage (nozzles and buckets) being impulse type, the effect of the thrust is reduced. nett thrust still being upstream.

1. Newton's Third Law of Motion: For every action there is an equal and opposite reaction.
2. The aircraft will move in the direction opposite to the change of direction of thrust. http://en.wikipedia.org/wiki/Thrust_vectoring

I think the trust force generated in Gas Turbine use for Aircraft/plane will be different with Gas Turbine for indunstrial (Power Generation). How about You & Other's ? Thankx.

As mentioned above the nett thrust is upstream in power gen

For air crafts, since the reducer in thrust ( ie the turbine stage) will be non existant, the nett thrust may be much more , in upstream.