Why metals in space can stick together on their own
In the conditions of outer space vacuum, metal parts can spontaneously bond together without heating due to the destruction of their protective oxide layer. This phenomenon poses serious challenges for spacecraft and requires special protective measures.
Ingenium
In the vacuum of space, two metallic objects pressed together can spontaneously fuse without the need for heating. This phenomenon occurs due to the absence of oxygen, which leads to the destruction of the protective oxide layer on the surface of metals. As a result, free electrons instantly move between the parts, bonding them into a single whole.
The Mechanism of Cold Welding in Space
On Earth, metal surfaces are covered by an extremely thin oxide film that forms upon contact with oxygen and acts as an insulating barrier. In space, where there is no air, this layer does not regenerate, and the extreme conditions further contribute to the breakdown of any remaining film. On a microscopic level, metal surfaces resemble tiny mountain ridges. When parts are compressed or vibrated, their microscopic protrusions deform, completely destroying the protective layer. Additionally, solar and ionizing radiation in orbit removes residual oxides, leaving metal atoms exposed and ready to bond.
Gold and platinum are especially prone to this type of adhesion, as they hardly form oxide films even on Earth. Gold’s softness allows it to perfectly conform to the shape of any surface and quickly adhere to it.
Impact on Space Technology
For aerospace engineers, cold welding poses a serious challenge, potentially causing hatches to jam, deployable structures to lock up, or fasteners to seize. One notable example of this phenomenon’s consequences was the Galileo spacecraft, launched to Jupiter in 1989. Vibrations during launch and the loss of lubricant led to the destruction of the protective layer on the antenna components, causing them to weld together in the vacuum and preventing the antenna from fully deploying in 1991.
Methods to Prevent Cold Welding
Various methods are used to protect equipment from spontaneous bonding:
- Anodizing to create a durable artificial oxide layer.
- Applying dry lubricants, such as molybdenum disulfide, to moving parts.
- Combining dissimilar metals with different crystal structures, which hinders the easy movement of electrons between them.
Before launch, all equipment undergoes testing on vibration stands and in vacuum chambers, since intense friction can trigger cold welding even under laboratory conditions on Earth.