Northrop Grumman Tackles Certification Hurdles for Single-Piece 3D Printed Tanks

Northrop Grumman is exploring the use of additive manufacturing to produce critical flight hardware, such as propellant tanks, as single pieces rather than assemblies of forged and welded components. Andrew Thompson, Manager of Northrop Grumman’s Additive Manufacturing CoE, highlighted this development, noting the potential for significant cost and lead time reductions.

The company successfully printed a demonstration propellant tank using directed energy deposition (DED) with titanium Ti-64, drawing on data from the GAMAT program. This printed version achieved approximately a 50% reduction in lead time and a 30% decrease in cost compared to traditional methods. The integrated design incorporates hard points directly into the tank wall and a feed tube that also serves as a locating point for propulsion line welding.

Despite the manufacturing efficiencies, certifying these single-piece tanks for spaceflight presents a significant hurdle, primarily concerning non-destructive evaluation (NDE). "A single piece tank becomes relatively difficult to inspect," Thompson stated, emphasizing the need for next-generation NDE techniques to ensure the integrity of these pressure vessels for orbital applications.

This challenge is analogous to issues encountered with 3D printed honeycomb panels. While additive manufacturing reduced costs by about 90% and topology optimization further improved stiffness or mass, the aluminum alloy AlSi10Mg used warped significantly during heat treatment. Northrop's solution involves a new alloy, CP1, which offers improved thermal and electrical conductivity and bypasses the problematic quench step, although its performance is still under evaluation.