The Problem
In a Mars dome, the sun is not a distant star; it is a furnace. Night brings absolute zero. Day brings scorching heat. Aluminum 6061-T6 and Copper expand at different rates. To weld them rigidly is to invite fracture.
We do not fix cracks. We design for the gap.
The Constants
Material A
Al 6061-T6
α = 23.1 µm/(m·°C)
Material B
Cu (Pure)
α = 16.5 µm/(m·°C)
Scenario: 2-meter span, ΔT = 70°C
Differential Expansion: 0.924 mm
This is not a margin of error. This is the required clearance.
Differential Expansion: 0.924 mm
This is not a margin of error. This is the required clearance.
The Solution
A floating bushing assembly. No rigid welds across the interface. The aluminum frame floats inside the copper sleeve, lubricated with vacuum-grade graphite paste.
Fig 1: Human calibration of the joint interface. The hand knows the tolerance better than the caliper.