Proposed traction kite

I’m designing a traction kite for a cruising boat. The kite will be a rigid glider (USA: sailplane) on a dyneema tether about 1km long.
I envisage sensors and servos on the glider, a computer, and a radio link to the boat. The computer in the boat will do higher levels of control, and connect to the glider and the boat’s steering autopilot.
I’d like to know whether I can use ArduPlane to control the glider. As is, or with changes.
I’m aware of some issues that may stand in the way. And there may well be others.

  1. The tether in normal use will be always taut, so the position of the glider is a 2-dimensional problem (azimuth & elevation) rather than a 3-dimensional problem. The glider is constrained to be on the surface of a sphere, more or less, though there will be sag and stretch in the tether.
  2. The list of types of vehicles covered by ArduPilot includes no tethered vehicles. See Vehicle Types Supported by ArduPilot — Plane documentation
  3. The tether tension will have a major impact on the motion of the glider. Will I need to feed the tension data into ArduPlane? If so, how? Or does Arduplane simply work from sensors (GPS, compass, barometer, IMU, etc) to estimate position and orientation?
  4. The direction of the tether is a good source of orientation information for the glider, similar to the earth’s magnetic field. I’m guessing it should feed into a modified EKF function.

I know there are also significant issues regarding launch and retrieval of the glider, but I don’t want to address those yet.
I can see there may be significant changes that I’d need to make to ArduPlane to get this concept working. Can anybody give me some idea how big these changes would need to be?
(I’m a retired software developer, so I’m not afraid of attempting a bit of work in this direction)
Thanks in advance - Geoff Draper

This is probably relevant:

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Thank you peterbarker! I’ve skimmed this thesis and it is indeed relevant. It presents a tethered glider using Ardupilot. I’m not yet clear how much the writer had to modify Ardupilot for his project. Hopefully more reading will illuminate. Perhaps I can obtain a copy of his code changes. The thesis also presents some aerodynamic calculations that will be useful. The project concerns power generation using the tether pull to turn a generator, so it is not so different from a traction kite. However I think I’d use a different system for launch and retrieval - his quadrotor VTOL scheme would cause a lot of drag in normal flight, and may not be so good landing on a boat. Conclusion? Yes Ardupilot can do my job. Thank you.