Alarik0

-110 kg. Mass without Kerbals, without cargo: 4533 kg. Mass without Kerbals, with cargo (rules of the challenge): 4598 kg.

Ah, did not know the negative mass thing. Option 1 is out of the question then. You can also do negative fairings (negative radius) which is pretty funny. To me it was like; I obtained the thrust vector offset of the LV-1R with Blender and, having that, it feels weird to find the balance numerically (as it now can be solved analytically). If that makes sense. Sorry for opening the can of worms. Let's see what @Alpaca Z thinks. It's an interesting problem nonetheless. For the sake of discussion: A craft X exists In-game construction methods exist for creating X I say that I created X purely with in-game construction methods The only way to conclude "X was created in-game" is if you trust me (why should you?). Without relying on trust, you can only conclude that X could have been created in-game (i.e. the .craft belongs to the set of crafts that can be created in-game).

As mass gets down, an additional rule might be needed. Let me explain: .craft editing is not forbidden explicitly in the challenge rules (as far as I know). It should not be completely forbidden, as .craft editing is necessary to align the thrust vector with the center of mass of final stages like this Eve one (LV-1R has an arbitrary thrust offset, and the Kerbal in the command seat has an arbitrary mass offset. This is compatible with in-game editor restrictions). I also used .craft editing to find a tight fairing (whilst respecting in-game editor restrictions -- e.g. no less than 0.2 distance units between sections, at least r>0.3 if not capped, etc.). However, when .craft editing, it is possible to circumvent in-game editor restrictions in several ways. There's 3 options: 1. Explicitly allow all .craft editing. As .craft files are perfectly portable between installs, when you download an edited .craft file, it works in a vanilla KSP install. However these files might not be possible to generate within the in-game editor. (This is very cheaty and broken, but would lead to cool new designs that are, again, portable to a clean KSP install). (This results in a set of .craft files that is a superset of in-game generable .craft files). 2. Allow all .craft editing done in such a way that all in-game editor restrictions are respected. (I like this one as it allows a lot of freedom without being cheaty). (This results in a set of .craft files that is equal to the set of in-game generable .craft files). 3. Whitelist the kinds of .craft editing allowed. For instance, allow for part displacement within sensible ranges, part rotation, and fairing construction (such that in-game editor restrictions are respected). (Impossible to enforce since the resulting set of .craft files is equal to the set of in-game generable .craft files -- i.e. indistinguishable from the set described in point 2. However, if we trust each other, this might be fine). A fourth option would be to disallow all forms of .craft editing. However, this is not enforceable as the resulting set is equal to sets described in points 2 and 3. (And would result in retroactive and biased (as unbiased .craft checking is impossible) disqualifications of the challenge).

Mass without Kerbals, without cargo: 4643 kg. Mass without Kerbals, with cargo (rules of the challenge): 4708 kg.