TL;DR
Increase the rocket capacity of U238 (but not other uranium items)What?
The current rocket capacity for U238 and U235 is 20, for uranium ore is 200, for uranium fuel cells and nuclear fuel is 10, and for various uranium ammos is 25. (Atomic bombs cannot be flown on rockets). These balance out so that for whatever final product you want, you'll need approximately the same number of shipments whether you're sending intermediate or final products. I suggest increasing the rocket capacity of U238 (to at least 100) so that it's much more efficient to ship U238 than any other options.Why?
Uranium can only be sourced from Nauvis, so it or its derivatives have to be shipped to any platform or other planet to use it. The relatively expensive cost of launching all uranium products disincentivizes using uranium products off of Nauvis. This is especially true of uranium ammo and atomic bombs, which are potentially very useful on surfaces besides Nauvis (nuclear fuel cells last so long that being expensive to ship matters less). Also every planet can make rocket fuel, but the expense of shipping uranium means nuclear fuel is underutilized. Lastly, there's hardly a use-case for centrifuges off Nauvis, which is a shame because they're Nauvis's unique building (and they're just great)!Making U238 cheaper to ship off-world would open up more viable usages of uranium products, but require building infrastructure for it. The simplest case is uranium ammo, which would be easy to produce anywhere that makes red ammo; this could make it viable to use uranium ammo on space platforms, without sacrificing the need to produce the ammo on-site (it could even require much more production on the platform, if switching from yellow ammo).
The other usages of U238 also require U235. If U238 is much cheaper to send to space, it would make Kovarex enrichment in space (or on other planets) the optimal way to get U235 off of Nauvis. To go even further, the rocket capacity of U235 could be decreased to 10 or even 5 for balance. I'd love to have a nuclear fuel cell space platform, covered in centrifuges, supplying my bases with power. Or a promethium science ship that receives shipments of blue circuits and U238 along with its biter eggs, and blasts its way toward the shattered planet with nuclear fire.
As far as believability/lore, it's easy to justify U235 having a much smaller rocket capacity: packing too much into the tight space inside a rocket would cause it to go critical!
