Back of envelope calculation gives me 5.54 cubic meters of internal volume (work at bottom). I did not consider the height of the titanium interface rings which would give a little more L to the cylindrical volume. I also am treating the space enclosed by each end caps as being 50% of a perfect sphere.
From Composites World article:
> Length, 2,540 mm; outside diameter, 1,676 mm;
> Initial design work indicated that the hull, to be rated for 4,000m depth with a 2.25 safety factor, should be 114 mm thick or 4.5 inches, which OceanGate opted to round up to 5 inches (127 mm) to build in an additional safety margin.
Cylinder ID: 1676 - 127 - 127 = 1422 mm
Cylinder internal volume Cross-Section Area: 1588141.06 mm2
Volume of Cylinder: 1588141.06 x 2540 = 4.03 m3
Volume of a sphere with D = Cylinder ID: 1.51 m3
Total internal volume ~ 5.54 m3