Kaiser Compositek / Boeing

Background

Kaiser were tasked with developing a lightweight composite tank for containing rocket propellant.

Problem

The standard composites used in carbon fibre construction or special aluminium were not compatible with the contents. A liner was needed which would not be affected by the fuel.

Solution

It was rapidly established that FEP would be the material of choice because of its inertness. As renowned experts in the field of fluoroplastic fabrications, Holscot were called upon to work with Kaiser to develop a lined carbon fibre solution.

The shape of the tank was dictated by the space available. The resultant design had two dished ends and only one very small outlet. The liner needed to accept an overwrap of carbon fibre so had to have a bondable surface. This could be achieved either by etching the FEP of using the FEP glass backed laminate material. Prototypes were created using both materials. This necessitated developing new techniques to weld the FEP without having the benefit of an internal support. The result can be seen on the photos.

Following on from the work done with this development project, Holscot has been involved in projects looking into designed-for-demise propellant tanks constructed entirely of plastics, featuring an FEP glass backed, or carbon fibre backed, liner fabricated onto a mandrel and overwrapped with GRP or CFRP. The resultant tank not only meets the goal of demisability but also reduces the mass of the tank. The tanks can also be designed to incorporate an FEP diaphragm.