That's obscenely, unnecessarily long-ranged. Most star systems are only ~4-5 billion kilometers in diameter at most (barring certain sorts of multi-star systems); you've got a range of 54 billion kilometers (and change) on the first stage. I'm honestly curious what sort of tech and efficiency rating you needed for the drive to reach that far.
I'm at... ion drive technology, x0.4 engine power, 0.9 fuel efficiency and 5 MSP, and the base stage has an entire MSP dedicated to fuel. Mind you it takes 7 months to travel that far, but obviously it won't have as far to go if star systems are under 5 billion kilometres. To be honest I knew I had a problem when the math indicated that it had a longer range than... 7 times the orbit of Pluto, but I was expecting a five-stage monstrosity missile to get to those types of ranges, so I thought that I had added a couple extra zeros or something.
Though to be fair to my missiles, my active-sensors are even more obscenely and unnecessarily long-ranged, especially when they can detect a size-1 missile from at least several million kilometres away. Admittedly the sensors have to be 2,500 tons and give off energy like crazy to get that good detection, but at those ranges my sensor ships have more than enough time to turn off their active sensors and flee, especially if I scatter several around the system, so it's more of a one-time investment. I knew that dumping all of my starting RP into active sensor strength was a great idea.
That aside, all of that just to deliver a single slow, inaccurate, STR-4 ASM is a bit much. But I don't see why any of it wouldn't be wrong mathematically.
Given how obscene the range is on the first stage, I'm definitively going to be increasing the overall power of that missile, though given that this current game is centred around goofing with extremely long-ranged missiles than actual feasibility, I'm not too concerned either way. I'm not a very serious Aurora player, if you can't tell.
Your missiles don't seem to have their own sensors. Do you have a 54 billion km missile fire control?
Does a 9 billion one count? Alright, alright, I'll scale it down a bit, but right now it looks like my missile ships are going to be mostly gun, magazine and firing control, with a little bit tacked onto the side for the crew/engineers. Though given the extreme ranges at which I'm using them, colliers ought to replace the magazines a bit. How quickly do ships reload from colliers? If it's a day or something like that I'd need to add more magazines onto my missile ships for when they pop in close enough to the enemy to be detected by the enemy sensors, probably due to a nearby colony or something like that.
EDIT: I'm going to climb up the missile tech tree a bit before redesigning the missiles. If I going to have stupidly large missiles, they might as well be stupidly powerful too.
EDIT2:
Missile Size: 20 MSP (1 HS) Warhead: 40 Armour: 0 Manoeuvre Rating: 30
Speed: 24000 km/s Engine Endurance: 4 minutes Range: 5.5m km
Cost Per Missile: 23.84
Chance to Hit: 1k km/s 720% 3k km/s 240% 5k km/s 144% 10k km/s 72%
Materials Required: 10x Tritanium 13.84x Gallicite Fuel x250
Development Cost for Project: 2384RP
Better design for a destructive missile?