I'll admit: I've used conventional engines in my designs before. I've even produced freighters with the same slowness. Have even experimented with one-hold freighters. My favorite is the "combo cargo-colonizer". It hold one hold of cargo and one cyro/passenger compartment: Meant solely to provide initial infrastructure and colonists for a colony.
Sounds like a fun scenario. Note that ships is really advanced for 1956.
I'll admit that apollo 11 didnt travel at 50km/s, but 8000 tons is actually much heavier than a fully loaded saturn V by almost 3 times, also in the grand scheme of things 10 years early isn't so bad for the russian version of the apollo program.
Now let me present the successor to conventional ICBM bases.
Missile Complex - II class ICBM Launch Base 6,200 tons 977 Crew 600 BP TCS 124 TH 0 EM 0
Armour 5-30 Sensors 1/40 Damage Control Rating 0 PPV 90
Magazine 360
PDC Size 30 Missile Launcher (3) Missile Size 30 Rate of Fire 450
Missile Fire Control FC15-R100 (1) Range 15.0m km Resolution 100
ICBM Drone (12) Speed: 3,300 km/s End: 75m Range: 14.9m km WH: 0 Size: 30 TH: 5 / 3 / 1
Active Search Sensor MR20-R100 (1) GPS 4000 Range 20.0m km Resolution 100
Missile to hit chances are vs targets moving at 3000 km/s, 5000 km/s and 10,000 km/s
This design is classed as a Planetary Defence Centre and can be pre-fabricated in 3 sections
You'll notice right away the oddly named ICBM Drone, it's nothing more than a conventional ICBM shoved into a Conventionally engined drone, that top speed of 3,300 km/s is actually ridiculous considering i haven't researched any reactors or even nuclear thermal engines yet.
Sadly i'm not sure how to sue space master to get some targets into the system to test these against, but i'm sure they're quite worthless for anything but flavour(maybe i'll get some disabled targets in the future i can test them against).