TL;DR
An endgame super-valuable resource which decays very quickly, can only be harvested in space, and spawns more frequently for high-speed vessels.What ?
Exotic particles would be a space-only resource which decays very quickly - lost if not used within seconds of harvest, so there's no feasible way to harvest them on one ship and use them on another. Their spawn rate would be correlated with the speed of the harvesting ship, so faster vessels could get more of them.To justify their use, Exotic Particles would be incredibly valuable to industry. The specific uses aren't important to the core idea, but some options are:
Advanced Beacons
Advanced Beacons would be a tier-2 beacon which could only be built on space platforms, are capable of broadcasting productivity/quality bonuses, and require a steady supply of EPs to run.
Advanced Labs
Advanced Labs would be tier-3 (or 2, I don't like the biolab
) laboratories, which would also be space-only and require EPs as fuel. Advanced Labs would have adjacency bonuses to efficiency (progress/science pack), but adjacency penalties to power consumption, making it an ever-increasing challenge to field bigger, faster and more power-hungry ship designsTransmutation
EPs could be an ingredient to recipes which create rare (i.e., normally limited) resources out of common ones - i.e., turn iron into titanium, etc.
Quantum Intermediates
Quantum Intermediates would be alternatives to existing intermediate products, with much cheaper recipes but rapidly-spoiling results - everything from raw materials to final products would need to be done on the same space platform, as things would spoil too quickly to be sent to a planet. Each quantum intermediate recipe would also call for EPs.
Why ?
I think it would be a cool endgame challenge to try to really maximize what you can fit on a space platform while still making it go very quickly.The ideas above - especially the advanced beacon and quantum intermediates - are intended to incentivize putting large and complex setups onto a space platform, then trying to make that platform go as fast as possible. I think this would be a fun and open-ended challenge for the extreme late game, creating bonuses for designs that can't be replicated by just copy-and-pasting more times.
Bonus: Deep Nebula
As a further addition to the above, have a space "region" which is not actually tied to a planet - you can go *towards* it, and the mix of asteroids you encounter will change the closer you get, but there is no actually reachable point. The further into the nebula your space platform goes, the richer local space will be in EPs, and potentially other resources making it possible for your craft to be more self-sufficient. However, the deeper regions of space would also be more dangerous.This would add another dimension to the "Fast space industry", making the bonuses even better if you can make ships that are largely self-sufficient, and can do as much as possible before needing to return to a planet for fresh raw materials.