How does R&D work?

[jgf1123]

So this is something that's confused me for a while: how does R&D work? It's clear that it follows the exponential progression

max R&D - new reliability = f(skills) (max R&D - current reliability)

where f(skills) a function of the SET skills between 0 and 1 (0 = reliability rises to max R&D instantly, 1 = no progress). If there's a single SET, then

f(skill) = 1 - k * skill

Depending on which of the 4 positions the SET personnel occupies, the k scalar changes. What I haven't figured out yet are:

1) How does RDDifficultyFactor and the 4 RDLevelMaxAmount factor into this.
2) How do the skills combine if more than one SET is assigned.

[jgf1123]

So I figured it out. The game takes a weighted sum of the 4 skills:

f(skill) = 1 - (k1*skill1 + k2*skill2 + k3*skill3 + k4*skill4)

Easy to research components have weights like (0.25, 0.18, 0.12, 0.04) for Explorer 1. The Saturn V in comparison is (0.05, 0.04, 0.02, 0.01), or about 5 times longer to develop. I'm still not sure how to get these weights out of the XML files, so I've been calculating them from sampled data.