The Mass (kg) and the MassPropMass attribute shows 0 (zero) in structural systems in Ship Basic Design.
Solution
For the weight calculation in Ship Basic Design, use "Weight and Center of Gravity".
Ship Basic Design works mainly with SheetBodies, therefore do not have volume nor mass/weight.
The sheet-bodies (and faces) have specific Ship-Attributes like SAW_THICKNESS. These Ship Attributes are used in the function "Weight and Center of Gravity" in Basic Design.
Notes and References
Hardware/Software Configuration
Platform: na
OS: windows
OS Version: 1064
Product: NX
Application: SHIP_DESIGN
Version: V1926
Function: BASIC_DESIGN
Ref: 001-9811087