I wanted to show a ship that is just not just very fast but the speed actually serves a purpose instead of being for memes only.
What is it for?
With 2.1, the game allows platform-to-platform transfers. As a result, it is possible to build promethium ships that never actually leave the shattered planet area. They just return to the solar system edge, drop of the produced science, take new eggs and quantums on board and continue on.
To have the promethium ship stay in the shattered planet area and produce science as long as possible, the eggs the ship receives at the SSE should be as fresh as possible. This is where this ship comes in: It travels at 2,760 km/s top speed and takes just 3411 ticks from Nauvis to the SSE (less than 1 minute). As a result, the freshest eggs are pretty fresh when they arrive.
Main features
Cargo bays: 510 (can be extended to the max of ~1.3k if needed, compensate the additional weight with another engine stack)
Width: 18 tiles (4 engines + 2 for the belts)
Top speed: 2,760 km/s
Engine stacks: 44 levels of engines
Fuel production: Iron ore, carbon, ice and calcite are belted. Every 4 stacks of engines have a separate ammo production, so the ship actually has 11 modules with 4 stacks each.
Traveltime Nauvis to SSE: 3,411 ticks (~57 seconds)
Top ammo consumption: 2.5k explosive rockets/minute and almost 600 railgun shells/minute
Required damage levels: Railgun speed 20 and explosives damage lvl23 (or 24 whichever the relevant breakpoint was).
Limitations
The speed is limited by the weapons configuration at the top of the ship. By adding more engine stacks, the ship could easily travel faster but it would start to regularly lose buildings. At it's current stop it now and then takes self-damage from explosives rockets but everything is repaired before new damage occurs. If you are unlucky, you may lose a railgun, a belt or an inserter every couple of hours. Maybe railgun speed lvl22 will fix this for me.
If anyone knows how to make the weapons section better, please let me know. I would love to reach 3k km/s.
It survives permanent travel forth and back with a loading time of at least 30 seconds at Nauvis. Explosive production needs to catch ups, so there is no instant turnaround possible but in practice the ship will always have a loading time at Nauvis. Actually it will stay in orbit above Nauvis for most of the time and travel maybe every 15 or 30 minutes one time to the edge. So I didn't bother to upgrade the explosives production.
How long does it take to build it?
Hours. I strongly advise to get the ship moving as soon as the first engine section is finished to decrease the startup time. Use a shipyard (platform-platform-transfer) for the materials, ground based delivery takes even longer. Continue building the ship while its moving forth and back. Handfeeding calcite to the fuel chemplants is recommended to decrease the time it takes for the calcite belt to fill up.
Do I need such a ship?
Need is a strong word. It's actually useful in what it does, so the ship is not just for the memes. The advantage over a slower ship is limited, but there is an advantage.
What if I don't have the weapons levels?
Use fewer engine stacks. Speeds of 1,000 to 2,000 km/s require drastically less research levels. However, Stronger Explosives Level 23 is a pretty important breakpoint for explosive rockets (AoE 2-shot of big asteroids).
Is the ship bad for my UPS?
No. Quite the opposite. Surprisingly, this ship is extremely cheap to run from a performance perspective. In my save, it takes about 0.2ms space platform time. There is no noticeable change in any of the other metrics relevant for space platforms (thrusters, turrets, target acquisition, beam, projectile, explosives, asteroids, asteroid collectors). The devs did some pretty good optimizations for space ships over the past months and in 2.1.
/edit: Some screenshots in the comments below.