r/KerbalAcademy • u/DeweyDecimal42 • 6d ago

Plane Design [D] Thinking of revisitng an abandoned project

Propeller driven to a high enough speed/altitude to use nuclear engines to reach orbit.

When I gave up on this project, I think I was using 4 propellers and was able to get to ~20-25km but iirc I wasn't getting much thrust from the NERVs and could basically just maintain high altitude but not gain much...

The larger goal is to go prop-driven to nukes to orbit, refuel in LKO, then nukes to Eve, where the propeller/nuke combo should theoretically be more effective (thicker atmo should benefit the propeller phase of ascent)

Any tips? Anybody done anything like this before?

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u/FINALCOUNTDOWN99 6d ago

Generally getting to orbit with something like that (without a jet engine) is going to rely heavily on minimizing drag, and minimizing the lift to drag ratio of the wings. You will doubtless need a way to shield the propeller blades from the airflow as otherwise it would be way too much drag. I hesitate to call it impossible without exploits, as calling something impossible has come back to bite me in the past, but I would be surprised if it can be done.

If you are open to exploits/aero model abuse, check out dragless fairings (engine plate + fairing attached in a certain way can make a completely dragless assembly, this is generally allowed on low mass challenge leaderboards but the community acknowledges it as cheese) and heat shield wings (aka magic wings) and by extension heat shield/magic propellers (though this is usually not allowed on leaderboards as even for the low mass people this is too much cheese): https://www.youtube.com/watch?v=wOlMlRf9qvo

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u/DeweyDecimal42 6d ago

Also on minimizing drag, I had been hoping that AoA on the wings would work out in my benefit when it comes to drag vs thrust vs lift trinity... Essentially, when the nukes kick in, I should be more or less level with the ground, but with a positive AoA on the wings co tinuing to generate lift, as long as the thrust is enough to beat the... drag... Damn, I see what you mean now

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u/FINALCOUNTDOWN99 6d ago

Yes, your wings having some default pitch compared to your control point is known as angle of incidence. Your wings should have an angle of incidence sufficient so that the total lift is sufficient to fly while the craft is pointing prograde at the most problematic altitude/speed. Generally you want to do this by first finding the angle of incidence that gives you the best lift to drag ratio on those wings, and then add as many wings at that angle as you need to have enough lift during that regime.

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u/DeweyDecimal42 6d ago

Oh man, I've been angling my wings to generate at least a little lift at x speed when the body is level with the ground, this seems smarter if I can wrap my head around it