There's simply no feasible defense in sending a miner on the outer space. Just imagine its components be removed due to high-speed orbit, or causing the miner to fall from whatever vessel it is, amonh many other reasons.
Forget the components, power, maintenance anything else.
The first step is to throw the damn thing out there

The cheapest way to send something to low orbit is via the Falcon 9 program, which they claim can go as low as 1700$/kg.
One s9 cost weights a bit over 4kg, that would mean 6800$ or...enough to run it at
17 cents per kWh for 4 years.
Not to mention that the miner would be stuck their indefinitely. Not great when new technology comes around.
Now if we change the Low Orbit Bitcoin Mining Farm into the Asic Planetary Cluster Bombing Battleship.

2. In space, low temperatures, which greatly facilitates the cooling of the system.
Since you talked about "orbital" facilities, do you know that the temperature varies on the low earth orbit varies from -100C to +120C ?