Max,

I'll presume that this all sits in a uniform magnetic field.

With the switch open you charge the two ends of the tether, the small capacitance of the end objects means that the potential tracks the generator's output. You will see some leakage - it is in a partial vacuum after all.

A vanishing transverse motion is applied to each half of the tether - as there is a short-lived and transient current flow as the two effective capacitors charge up.

So a tiny torque is applied since the currents travel in opposite directions.

When one closes the switch the currents are reversed and an opposite torque is applied.

You have invented a very inefficient magnetorquer.

It would be far more efficient if you closed the circuit, and had high currents rather than high voltage in many dozens of turns of wire.

Or am I misconstruing the purpose of this device?

James,

this device is meant to increase or decrease the orbital velocity of a spacecraft by passing an electric current in a given direction through a wire conductor. The current electrodynamic tethers https://en.wikipedia.org/wiki/Electrodynamic_tether require a space plasma to enable electrons flow from one end of the tether and out on the other side.

I don't think any torque is generated by this system for example when an electric current is flowing from the negative to the positive end of the tether when the switch  is closed.

Max,

A vanishingly small current flows - as there is no return path.

Your diagram has a single wire extending from a source of potential difference - how does current flow in such a circuit, except for the minute 'displacement' current needed to charge the (effective) capacitors at either ends of the wires?

Thank you James,

I missed something vital in the diagram, there have to be two wires.

Max,

Feel free to draw them on. More exactly, there has to be a current loop in order for a uniform magnetic field to generate a torque.

James,

I have made the change in the diagram. I don't want to get a torque I want on closing the switch electric current flows through the tether and changes the orbital velocity of the spacecraft.

Max,

You have made a slightly-more efficient magnetorquer. You have a current loop in a (presumably) constant magnetic field (the strength or uniformity of which are not shown).

Schoolboy physics tell you that you have made a motor that will slowly rotate. If you increased the area of the loop that crosses the magnetic field, and switched out the voltage source for a beefy current source, then you would have higher efficiency.

If you are seeking to change the orbital speed of the craft, you could use this to spin up a two-part spacecraft, and then cut the tether when you've reached a high enough speed of revolution.

But as drawn, you certainly won't change the motion of the barycentre in a uniform field.