My Space Plane Idea w/ Avionics Breakdown

I have an idea, where I have my model rocket send my payload (space plane) up to 500m high, and then deploy the space plane.

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The Space Plane would have an A-BT engine in it, and would ignite to reach higher speeds after deployment.

After ~5 minutes of gliding around, it would nose dive to a landing location, and would deploy parachutes before landing, and land like the space shuttle. The spaceplane may be remote controlled.

For Avionics, I will have a pi zero 2W in the spaceplane, and a pico in the rocket. The spaceplane's engine will be activated with a delay, so it doesn't burn up the rocket.

But how will I know when to deploy the payload? There will be sensors both on the rocket and on the space plane for altitude, attitude, velocity, etc. Once the velocity starts to slow down, to maybe +10m/s the Fairings would seperate so the spaceplane can coast a little before apogee.

I would control the rocket and the spaceplane through my uconsole.

Remember, this is all ideas/planning. Questions?