Wouldn't you want to run tests in multiple orientations to cancel Earth fields anyway? Similar to how you would run a Michaelson-Morley interferometer experiment.
The torsion balance introduces fixed biases, and can be operated only in XY plane. So in theory you're right, in practice it's not possible.
Not canceling earth's magnetic field (an easy thing to do) when measuring microNewtons at high currents is just very poor experimental practice. Unprofessional. Amateur.
You could but that may be a bit complicated to set up, while Helmholtz coils are dead easy to make and install. It's just a frame, copper wires, 3 power supplies, a magnetometer and a PC (even an Arduino could drive it).
"The motion of the beam is damped by a pair of aluminum plates attached to the beam that move in the magnetic field of an array of small neodymium-boron magnets. The power circuit was extensively shielded to insure that stray fields did not compromise the results."
Be careful here. Magnetorquers do exactly what the name says - they create torque, which manifests as rotation around a point. If a device demonstrates linear force, it's likely to be a different effect (electrodynamic), which currently requires a rather long tether to work [1].
Right, or we can just link to the physical law itself: - Lorentz force - the force on a current carrying wire. No need for a long wire. It's in the range of micro-Newtons for few Amps, for 10cm, at earth magnetic field:
"When a wire carrying an electric current is placed in a magnetic field, each of the moving charges, which comprise the current, experiences the Lorentz force, and together they can create a macroscopic force on the wire (sometimes called the Laplace force)."
I’ve never understood this position with the EMdrive and similar technologies; wouldn’t magnetic propulsion revolutionize low-earth-orbit travel, or whatever the ceiling is for pushing against Earth’s magnetic field?
I find it quite hard to believe that this obvious question wasn't challenged by anyone. To me it is like questioning if any of the people involved prior to publishing this news are capable of solving 1+1.
It's basic. I don't think of the relevant people as idiots.