Kerbomax Mainsail

[Psycix]

Modeling it in great detail may indeed take too many polygons.

Let's look at the LV-T30:

Above the nozzle you can see a central can that covers most of the plumbing, but it does have the required size and shape for a combustion chamber and the like.

The "exhaust pipe" on the side tells us it uses a gas-generator cycle to power the turbopumps. (the main alternative to a gas-generator cycle is the staged combustion cycle)

If we compare it to a real-life one, for example, the Merlin1D, we can see that the proportions are realistic. The massive amount of plumbing and electronics above the engine can be ignored, they would be impossible to model and are better off stuck in the cylindrical top part like they did on the LV-T30.

Merlin engine picture.

In the subject of staged-combustion cycle, an example would be the NK-33, as you can see, the exhaust pipe is gone, and the russians went with a rather simple yet robust stack of turbines in an assembly parallel to the combustion chamber. The space shuttle main engine, or "SSME" is also a staged-combustion design, with all the stuff wrapped around the combustion chamber in a more complicated way.

I think the Skipper and Mainsail engines can be compared to these:

As you can see, there is a big volume in the top half of the engines that accommodates all of these parts, while providing a low-poly solution. They are then made visually pleasing by having some pipes run around to add detail.

Personally I love how the mailsail has got a fuel line running down to the nozzle for regenerative cooling (although I hate how yellow it is), it is a small detail that shows the presence of a part as seen on real rocket engines.

Aaaanyway, I think I'm getting carried away here, I hope you find this an interesting read.

The message I'm trying to convey here: I think it is possible to make relatively low-poly models that satisfy all realistic aspects. Although the enthusiasts like me might enjoy seeing a high-poly turbine housing, a simple cylinder that shows "it is there" should be sufficient: it shows that the modeler put thought into it and the engine is realistically possible.

I hope I'm not pushing my opinions, you're a modder with no obligations to me at all so I think the way you welcome feedback is amazing! May this inspire you to make many more awesome parts!

[Camacha]

I fully agree. Basing the models and properties on real world engines does not only add to the immersion of the game, it also encourages learning more about how real rocket engines work and why. Exactly what KSP does (and I believe intends to do). I really feels right to be able to see that a rocket should have a higher ISP based on its design.