[Bored chemist]

Inertial propulsion is the "graal" everyone try to discover because it can be achieved without any loss of mass.

No it is not.
Because we know it is impossible.
People should not waste time on it.

[Deecart]

What theory says an action can occur with no reaction?

No theory say that.
Is it what you have understand ?
No. I say that if you have a 2 parameter propriety (here space and time) you can have a continuum of the 2 values that have in result the SAME value.

Action have reaction : SAME value (theory is,safe)
BUT : It only apply in this very primitiv way for flat spacetime.

Because we know it is impossible.

What ! You KNOW it is impossible ?
For what reason ?
Because mathematic say so ?
This is not physic, sorry.

So are you saying that Newtons 3rd law of motion is wrong?

Sure it is wrong.
Like every law.
The law depend on the environnment, and there is no environnment (the details) in mathematic (therefore this is not physic... Newton was a MATHEMATICIAN)
Therefore you have to be very carefull before you apply "a law" and you have to consider the "environment" where the law CAN apply.
We know that EVERY law has a limited domain of application.
If not, we already could modelise every phenomenon using only 2 parameters.

[Kryptid]

We know that EVERY law has a limited domain of application.

So what is the limit of the law of conservation of momentum?