Prototyping lightweight composite LOX and IPA tanks for LV4.
The good: the current PSAS CF airframe technology seems to offer fantastic tank factors if they can be used as propellant tanks, even given extremely conservative mass growth assumptions. This could give us the mass ratios to get LV4 above the von Karman line. Early conceptual design analysis for LV4 suggests that 280x700 mm modules are optimal.
The bad: Composites are hard... -Lack of established design criteria for composite tanks -Galvanic corrosion of composites in contact with metals -Composites degrade under extreme temperatures -Composites degrade in the presence of mositure -Difficult to detect defective adhesive bonds in composite structures -Difficult to maintain hermetic seals -Difficult to incorperate cutouts -Significant problems with CTE mismatch when sued in conjunction with metallic structures