3.5 Design, Manufacture and Test of Cryotank Components

As part of the Space Technology Game Changing Development Program (GCDP) composite cryotank technology development (CCTD) contract, the National Aeronautics and Space Administration (NASA) worked with Boeing to design, manufacture, and test two large-scale composite cryotanks. The primary focus of the contract was to demonstrate the potential to reduce overall cost by 25% and weight by 30% on an extended mission 10 m upper stage liquid hydrogen (LH2) tank while maintaining metallic design reliability. The two tanks (2.4 and 5.5 m diameter) were sized to carry launch and flight line loads. They were tested to validate low temperature performance and permeation resistance. These tanks encompassed several challenging design features: (1) one-piece co-cured/co-bonded spherical geometry with integral fluted core skirt, (2) out-of-autoclave (OoA) curing carbon/epoxy (C/E) materials, (3) permeation resistant thin ply hybrid laminate skins, and (4) off-axis slit-tape tow (STT) construction. The tanks were built on 16 and 24 piece collapsible composite tools using robotic automated fiber placement (RAFP). Future spinoff applications include LH2 and liquid oxygen (LOX) tanks for launch vehicles, in-space propulsion systems, on-orbit propellant depots and long duration aircraft. This chapter provides a historical review of the US aerospace industry’s efforts to mature composite cryotanks with specifics on how the CCTD program has been a crucial building block toward this end.