|Luna Mk1, Mk 2 and Mk 3 (l. to r.)|
The second change between the Mk 1 and Mk 2 was adding additional armor to the stern. Ramming was considered unlikely but useful as a threat when boarding suspicious ships in orbit. The reality was the Luna had no landing gear and was often called on the refuel from icy bodies. In that case tit was expedient to smack the ground and break it up before loading ice int a hopper installed that could be set up in the emergency lock at the stern.
As you can see the added armor proved such a good idea that the engineers kept adding to it. It made soft landing somewhat academic provided the crew was strapped in.
The Luna's Ram was of a transparent variety of metasite. It was further reinforced with a concave tip. The metasite was as clear as frosted glass and a searchlight was installed to further illuminate the landing area. t helped keep stupid people from being squished.
Luna has four main airlocks ... technically. One lock is the standard people passer. You get in you vacuum gear and it cycles you through. Another lock usually has a magnetic grapple thrower mounted. The third lock has deluxe spacesuits mounted against the inner wall. You enter them by climbing through a small port into the suit. The last lock is usually not a lock at all. On most ships it is a simple tool locker opening to the outside. Vacuum sleeves and gloves let personnel onboard help spacesuited personnel. A tiny lock mounted on the inner wall lets tools and parts be passed out of the ship quickly. In practice all these can be converted back into standard airlocks within an hour.
One of the later modifications of the Luna was to the guns. The rocket ammunition used liquid fuel pumped into the barrel to fire rounds initially. The rounds then ignited their main motors a safe distance from the hull. The storage of this liquid fuel and barrel corrosion caused maintenance problems and eventually magnetic accelerators replaced the fuel system.
The viewing ports above and below the guns are specially treated sections of hull rendered transparent and polarized against glare. They are part of the rest of the hull and nearly as strong. In practice it sacrifices very little to safety and crews like seeing what is around them. In later ships there is an argument whether to even include transparent sections. Another proposal is to have the transparent sections also function as data screens highlight important feature or allowing video conversations.
Next up, the engines!