# Version 0.8 Optimisation Design Basis

## Objective

Reduce the three Version 0.5 structural concerns without allowing uncontrolled mass growth:

- ring emergency-braking flexibility;
- forward docking-frame flexibility; and
- propulsion-mount displacement.

## Constraints

- home-PC-scale beam model;
- no change to overall vehicle length or ring diameter;
- no fictional materials;
- aluminium screening properties retained;
- idealised structural mass target below 10,500 kg;
- first supported flexible mode at least 0.15 Hz;
- misaligned-docking translation no more than 25 mm;
- propulsion translation no more than 5 mm.

## Decision logic

The DOE varied spine depth, section sizes, ring-brace count and docking-spreader geometry. H3 was selected as the lowest-mass candidate that met all final criteria with useful margin. H4 was stiffer but added more than 620 kg for only approximately 2.65 mm additional docking improvement. H8 doubled the ring-brace count and added more than 1.6 tonnes without improving docking response.

## Model limitations

- rigid beam joints;
- no shell interaction;
- no bearing compliance;
- no bolt, weld or latch flexibility;
- no geometric nonlinearity;
- no imperfections;
- approximate nearest-node placement of subsystem masses;
- fixed-aft support used only as a comparative screening boundary condition.
