Spacecraft bearings need lubricant at their rolling contacts, but lubricant that leaves the contact can migrate toward sensitive surfaces. Surface creep and evaporation are different processes. A non-contact labyrinth seal makes the route more difficult without rubbing against the shaft.
In the 2025 vacuum-rig experiment, the SHORT, LONG and STEP geometries measured lubricant mass-loss rates of 4.35, 3.41 and 2.73 mg/h. In that setup, STEP measured about 37% less mass loss than SHORT. These are results for one laboratory configuration—not a bearing-life guarantee or a flight result. ESA’s May 2026 report described a 3U CubeSat validation planned for late 2027; that was a plan, not a completed flight test.
Study credit: Josef Pouzar, David Kostal, Lars-Göran Westerberg and Ivan Krupka, ESMATS 2025. NASA’s cited mechanism standard applies within its stated scope.
Chapters:
00:00 Title / Chapter 01 — A moving shaft, a vanishing film
01:38 The bearing carries a load through a small contact
02:47 Vacuum changes where molecules can travel
04:15 Lubricant loss has two destinations
05:46 Engineers choose the lubricant for the job
07:13 A barrier and a reservoir do different jobs
08:35 A non-contact barrier protects without touching
09:46 Why a stepped path changes the route
11:05 The vacuum rig weighs what leaves
12:40 Three shapes, three measured rates
14:07 Other test conditions change the picture
16:17 Qualification is about the whole mechanism
17:49 From the laboratory toward orbit
18:44 Keep the lubricant useful
Sources and further reading:
https://www.esa.int/Enabling_Support/Preparing_for_the_Future/Discovery_and_Preparation/Keeping_Space_Mechanisms_Lubricated
https://standards.nasa.gov/standard/NASA/NASA-STD-5017
https://standards.nasa.gov/sites/default/files/standards/NASA/B/2022-12-06-NASA-STD-5017B-Approved.pdf
https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Science_of_friction_keeping_things_moving_in_space
https://www.esmats.eu/esmatspapers/pastpapers/pdfs/2025/pouzar.pdf
https://doi.org/10.1016/j.vacuum.2025.114434
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