Vessels with concave elements and systems including the same

A multi-walled storage tank, comprising:

• a pressure vessel comprising an inner volume surrounded by an inner shell, wherein the inner shell comprises at least one concave surface;
• an outer shell surrounding the inner shell;
• a vacuum chamber between the inner shell and the outer shell;
• and
• at least one structural coupling between the inner shell and the outer shell at one or more vertices of the multi-walled storage tank, wherein the at least one structural coupling is configured to partially or fully cancel out deforming forces experienced by the multi-walled storage tank.

A multi-walled storage tank, comprising:

• a pressure vessel comprising an inner volume surrounded by an inner shell;
• an outer shell surrounding the inner shell, wherein the outer shell comprises at least one concave surface;
• a vacuum chamber between the inner shell and the outer shell;
• and
• a container surrounding the outer shell, wherein the container is configured to support the outer shell at one or more corners of the outer shell, and wherein the multi-walled storage tank is configured to receive and store one or more aircraft systems or components in a space between the outer shell and the container.