Oh yeah, I forgot lower tier hardware wouldn't necessarily be rendered obsolete as soon the next tier had been unlocked. A tier 1 lander could be reused in the Jovian system, since the moons there are actually lower gravity worlds (except from Io) compared to the Moon. In fact, that's pretty much the case of the entire outer solar system. Titan would be the only unique exception because of its atmosphere. When traveling within a local systems like that, all one could possibly need is just a tier 1 rocket+lander combo. I'd imagine tiers would function like this: - Tier 1 Booster: The cheapest kind of rocket are made of these. Insufficient for full-fledged expeditions through interplanetary space. Capsule: A basic crew pod. For balance reasons I think it should together with a single tier 1 rocket always be capable of taking the player back home. Supposedly its life-support and propulsion just enough for a 1-way trip through interplanetary space (hence why it's not used for interplanetary expeditions). Lander: Can only be used for worlds with no (or minimal) atmosphere. Despite being low tiered it's still very adaptable. -Tier 2 Booster: Offers twice the lifting power. Perhaps its distinct feature would be an aerospike engine? Capsule: Fully capable of interplanetary travels due to more advanced life-support and propulsion system. Lander: A more elaborate lander designed for worlds with a notable atmosphere. Its engine could also be an aerospike. It will float in liquid. -Tier 3 Who knows! I've also been thinking of the GUI, and it's overlapping Not Enough Items GUI elements. But I supposed there's actually no real issues with that, since for example, Tinkers' Construct simply hides NEI's GUI while having the smeltery open. Galacticraft could do the same, potentially. Anyhow, I've been refining the rocket assembly GUI concept, which is now known as Vehicle Assembly: Earlier I suggested the simplicity of a regular tier 1 booster magically splitting into two side boosters if used in the 3rd rocket slot. But for sake of conceptual demonstration of alternatives, I've this time made an actual booster slot to show how it could look like. What they should be fueled on ingame is up to discussion. This concept is also exploring the possibility of a Docking/Spacestation Module. It should be a more comprehensive alternative over the regular "taking an x amount of resources into space". Once deployed it should roughly look something like this: That's right, the player is free to build his spacestation from here. I'm also suggesting docking ports could allow inter-vehicular transfers for a direct boarding of your spacestation. An EVA transfer could still be done if necessary (and possibly have your CSM strapped to the spacestation to prevent it from floating away). I'm not entirely sure about the docking process however. It's also heading to the realm of off-topic, so I'll stop for now.