If the drone can get reasonably within the yard on dead reckoning, then let's see.
1. Shield the sides of the drones physically with lexan and the internals with a Faraday shield. The lexan discourages firing at it since penetrating it would usually require large enough ammo to present a "bullets fired up" danger while the Faraday shield should prevent any kind of jamming or EMP attack. Basically, once it's up, good luck getting it down early without some risk of collateral damage.
2. Should be pre-programmed so no control signal at all. If the parameters are set ahead of time and it has a compass and accelerometers, it should be able to steer itself into the prison yard (which tends to be pretty large compared to the drone) with little trouble with just its own reckoning. Plus if it goes one-way, it can't be followed back to its controller.
3. Flying high will beat a vertical net while a spike under the payload should defeat a horizontal net.
4. Agreed, though drone motors don't tend to be all that noisy to begin with. The shields should help deflect any remaining sounds.
5. Not camo: either sky blue for daytime ops or black for night-time. Also, heat-deflecting coats in case the prison uses an IR sensor. Another option is to try to align with the sun so that people can't look up to aim at it.
6. Not going to be effective against a prison that would regard ALL such things as suspect and simply design to country ANY and ALL. What you need isn't numbers but stealth.
Biting the hand that feeds IT
