stepExternal( qV, qA, del ) {
		// other inertial equations are 'p += (Vf+Vi)/2' which adds the delta in velocity over 2...which is (sort of) the 1/2A...

		qV.r.addDel( qA.r, 0.5*del ); // add 1/2 A T  rotation
		qV.v.add( qA.v, 0.5*del ); // add 1/2 A T  rotation applied to acceleration vector

		q.v.addDel( qV.v, del ); // add inertial velocity  (vt + 1/2At^2)
		q.r.addDel( qV.r, del ); // add inertial spin      (vt + 1/2At^2)
	        
		return this;
	}
// del is the amount of time (1.0 default)
del is the amount of time (1.0 default)
del is the amount of time ( 1 . 0 default )
stepExternal( qV, qA, del ) {
		qV.r.addDel( qA.r, 0.5*del ); 
		qV.v.add( qA.v, 0.5*del );  applied to acceleration vector
		q.v.addDel( qV.v, del ); 
		q.r.addDel( qV.r, del ); 
		return this;
	}
stepExternal ( qV , qA , del ) { qV . r . addDel ( qA . r , 0.5 * del ) ; qV . v . add ( qA . v , 0.5 * del ) ; q . v . addDel ( qV . v , del ) ; q . r . addDel ( qV . r , del ) ; return this ; }
del is the amount of time (1.0 default)
del is the amount of time ( 1 . 0 default )
// other inertial equations are 'p += (Vf+Vi)/2' which adds the delta in velocity over 2...which is (sort of) the 1/2A... // add 1/2 A T  rotation // add 1/2 A T  rotation applied to acceleration vector // add inertial velocity  (vt + 1/2At^2) // add inertial spin      (vt + 1/2At^2)