Steering a Spaceship using rigidbody

Hello there,

I spent a lot of time trying to figure this out, but I just can't do it, sigh. To show you what I want to do, I draw this little image, only for you folks.

I want to control the spaceship by directly accessing the engines. Meaning, when I put a force on 0, it rotates to the right, a force on 2 to the left and a force on all 3 of them or on 1 only makes it go forward. Sadly, this doesn't really work, and I am wondering what I am doing wrong, this whole rigidbody thing just doesn't work for me and it's kind of frustrating. Enough of me whining, here comes the code (the part that matters):

 function Update(){
 
 if(Input.GetKeyDown("j"))
         raiseEngine(0);
 
     if(Input.GetKeyDown("k"))
         raiseEngine(1);
 
     if(Input.GetKeyDown("l"))
         raiseEngine(2);

     if(enginePower0 != 0){
         dir = engine[0].transform.forward;
 
         rb.constraints = RigidbodyConstraints.FreezeRotationX;
         rb.constraints = RigidbodyConstraints.FreezeRotationZ;
 
         rb.AddForceAtPosition(dir.normalized * enginePower0 * 0.000002, engine[0].transform.position, ForceMode.Force);
 
         rb.constraints = RigidbodyConstraints.None;
     }
 
     if(enginePower1 != 0){
         dir = engine[1].transform.forward;
 
         rb.AddForce(dir.normalized * enginePower1 * 2, ForceMode.Force);
 
         //rb.constraints = RigidbodyConstraints.None;
     }
 
     if(enginePower2 != 0){
         dir = engine[2].transform.forward;
 
         rb.constraints = RigidbodyConstraints.FreezeRotationX;
         rb.constraints = RigidbodyConstraints.FreezeRotationZ;
 
         rb.AddForceAtPosition(dir.normalized * enginePower2 * 0.000002, engine[2].transform.position, ForceMode.Force);
 
         rb.constraints = RigidbodyConstraints.None;
     }
 }
 
 
 function raiseEngine(number: int){
     if(number == 0)
         enginePower0 +=1;
     else if(number == 1)
         enginePower1 += 1;
     else if(number == 2)
         enginePower2 += 1;
 }

The whole rigidbody.constrains thing is done because the ship is rotating in any randomly direction it can.

Any help will be truly appreciated, thank you so much in advance!