Launch Vehicle Structures: Fairing Material Study & Payload Plate Design

Composite design and structural optimisation across two components of a launch vehicle programme. A fully parametric FEM model was developed to compare monolithic, sandwich, and stiffened-monolithic fairing architectures against buckling safety factor, mass, cost, and manufacturability — giving the client a data-driven basis for architecture selection rather than a single fixed design. In parallel, a payload support plate was designed and validated by FEM with a focus on mass reduction and vibration behaviour under launch loads.

A fully parametric surface model was built covering skin thickness and layup, longitudinal and circumferential reinforcement count/width/thickness/layup, interface corner geometry, nose material and thickness, HDRM count and position, nose separation angle, and overall fairing shape (ogive equation, cylinder and cone heights). This single model could generate any of the three candidate architectures — monolithic, sandwich, or stiffened-monolithic — simply by changing parameter values, avoiding the need to rebuild separate models for each option.

Boundary conditions replicated the real assembly interfaces: encastre at the fairing base, rigid coupling at HDRM tabs, contact without penetration between the two half-fairing tabs, and rigid coupling between the nose and each half-fairing. Pressure loading varied by zone — distinct values for the conical, cylindrical, and ogive sections — and material inputs covered UD and woven carbon prepreg, structural foam core, and aluminium interfaces.

The design criterion was buckling safety factor rather than static stress alone: preliminary analysis showed the buckling condition under pressure governed sizing well before the fairing's dynamic deflection limit. Each architecture was pushed through its own optimisation loop, using a mass-normalised efficiency coefficient (safety factor divided by mass squared) to compare configurations on equal terms. The monolithic solution proved most efficient once stiffened variants were also explored: adding stiffeners to reduce skin mass looked attractive on paper, but consistently reduced usable payload volume, increased aerodynamic loading from the larger resulting envelope, and ultimately produced a heavier fairing once those knock-on effects were included — a finding that shaped the client's final architecture decision.

The payload support plate was addressed as a parallel work package: FEM-driven design and validation targeting reduced mass while keeping the plate's vibration response within the qualification envelope required for launch loads.