A freighter really shouldn't have 15% of its mass dedicated to armor

[ericthered]

Huh, some interesting decisions here:

I'm not sure why you're using a fusion torch instead of a fusion rocket. the rocket has 4x the delta-v. Do you need the speed?

I'm surprised to find out that using water is cheaper than hydrogen, but the math holds up. Even counting transport costs, water is half the dv for 1/50th of the price, and you only decrease cargo space by 25%, so it makes sense. And you probably don't even need pure water: melted ice from an icy moon like Europa will work.

I'm sad to see you drop the FTL "emerging at rest" mechanism. I was having a lot of fun with it.

A freighter really shouldn't have 15% of its mass dedicated to armor, but spaceships always buts it in, so I can see not rocking the boat.

[vicky_molokh]

Originally Posted by ericthered

A freighter really shouldn't have 15% of its mass dedicated to armor, but spaceships always buts it in, so I can see not rocking the boat.

If you build a ship from, say, Control Room, Fuel Tank, Engine, and the rest filled with Cargo Holds, what are the Cargo Hold walls made of given their price and mass?

[ericthered]

Originally Posted by vicky_molokh

If you build a ship from, say, Control Room, Fuel Tank, Engine, and the rest filled with Cargo Holds, what are the Cargo Hold walls made of given their price and mass?

They're not. Cargo is strapped onto the ship, in an open frame style. You see that in a fair amount of art, and it generally rings more hard science fiction and less space opera when you see it. Though I will admit that for that you usually want some large piece of scaffolding to hang things on.

Of course, what I usually do when I build ships is use three subsystems of armor.

[vicky_molokh]

Originally Posted by ericthered

They're not. Cargo is strapped onto the ship, in an open frame style. You see that in a fair amount of art, and it generally rings more hard science fiction and less space opera when you see it. Though I will admit that for that you usually want some large piece of scaffolding to hang things on.

That clashes with the rules on cargo hold doors, pressurisation etc.

[ericthered]

Originally Posted by vicky_molokh

That clashes with the rules on cargo hold doors, pressurisation etc.

Where might those be found? Also, this might be derailing the thread. Shall we take it to a new one?

[vicky_molokh]

Originally Posted by ericthered

Where might those be found? Also, this might be derailing the thread. Shall we take it to a new one?

SS1:42 mentions that for smaller ships "If [...] a cargo bay door is opened, the entirespacecraft is affected", while larger ships are compartmentalised into three or twenty sections depending on size. The next page talks about what size are the cargo bay doors and in what situations that can be relevant and how. Those doors have dDR based on the hull (armour) of the section.

[Fred Brackin]

Originally Posted by vicky_molokh

If you build a ship from, say, Control Room, Fuel Tank, Engine, and the rest filled with Cargo Holds, what are the Cargo Hold walls made of given their price and mass?

Exterior walls are DR (not dDR)2 sheet metal. Half as thick as modern automobile sheet metal. Interior walls could be the same for components without intrinsic mass of their own such as Cargo Holds.

Lack of real exterior walls is acceptable for a ship that never enters atmosphere or otherwise experiences stress. But if you start looking at TL6-8 ocean freighters you'll find that their hulls are made of (at least) half an inch of mild steel (c. DR 25). If you built these ships in Spaceships you'd find that listed under "Armor" even f it's not intended to protect from attack.

[thrash]

Originally Posted by ericthered

Cargo is strapped onto the ship, in an open frame style.

Open frame armor is a thing (SS7, p. 21). I would expect that designs with no armor systems still have a few DR of hull -- just not enough to register on a dDR scale. Cargo strapped to the outside would be carried on external clamps, I would think.

Micrometeorite and radiation shielding is still important on a freighter, especially one with significant delta-V and a need to routinely traverse the Van Allen belts.

[YankeeGamer]

Use the rules for smaller systems (GURPS Spaceships 7) and you have enough armor to give adequate structural strength and pressure integrity. 1/3 DR is sufficient for most space going craft. I would be disinclined to even allow a ship with less than that, if it had any significant acceleration at all--.1 G or more--or would ever land anywhere.

[ericthered]

Originally Posted by vicky_molokh

SS1:42 mentions that for smaller ships "If [...] a cargo bay door is opened, the entirespacecraft is affected", while larger ships are compartmentalised into three or twenty sections depending on size. The next page talks about what size are the cargo bay doors and in what situations that can be relevant and how. Those doors have dDR based on the hull (armour) of the section.

Wow, that's a pretty restrictive section. I'm used to spaceships being a bit more flexible than that, as we often use it to build all sorts of things. It appears that the rules would imply not only that armor is part of the cargo rules, but that on small ships cargo is part of the main hold.

Once you're SM 10 or larger, you have more leeway to say "I just strap it on", as it says it has doors separate from the cargo system.