Our proposal for fast-cycling actuator materials using cold gas sprayed copper on NiTi shape memory alloys has been selected for the ESA Open Space Innovation Platform (OSIP) Proposal Phase. The full proposal deadline is March 13, 2026.
Why this matters
Shape memory alloys deliver excellent force density, but they actuate too slowly for most space mechanisms. Standard NiTi tops out around 1-10 Hz. The bottleneck is thermal: NiTi has high electrical resistivity (~80 μΩ·cm) which makes Joule heating inefficient, and vacuum eliminates convective cooling entirely — you're left with radiation only.
Space applications like fast steering mirrors for laser communications, lubricant-free orbital robotics, and active micro-vibration damping all need 50-100 Hz actuation. Getting there requires fundamentally changing how heat moves in and out of the material.
The approach
The project coats structured NiTi substrates with 50-500 μm of copper using Cold Gas Spray (CGS) deposition. CGS operates below 200°C, bonding copper to NiTi through mechanical interlocking and adiabatic shear instability without forming the brittle Cu-Ti intermetallics that kill electroplated and thermal-sprayed coatings after a few thousand cycles.
Three mechanisms work together:
- Skin effect heating — High-frequency AC (100 kHz) forces current through the conductive copper layer instead of the resistive NiTi core, enabling rapid uniform heating
- Radiative cooling — CGS creates highly textured surfaces with emissivity ~0.30 (vs 0.02 for polished copper), increasing radiative cooling power 5-10x in vacuum
- Solid-state bonding — No intermetallics means the coating can survive the 4-8% transformation strains that NiTi undergoes during actuation
The gap in the literature
The thermal cycling durability of CGS copper on NiTi under extreme transformation strains is completely uncharacterized. Published work covers CGS copper on steel and aluminium substrates, but nobody has tested what happens when the substrate itself is deforming 4-8% every cycle. This project will systematically map the failure modes across different substrate preparations and coating thicknesses.
The target: 10,000 thermal cycles in vacuum (10⁻³ Pa) with zero coating delamination.
What's next
The ESA OSIP proposal phase runs through March 2026. If funded, the project advances NiTiCu actuators from TRL 2 to TRL 5 — from laboratory proof-of-concept to component validation in a representative environment.