Just as in every application on planet earth, lubricants play a critical role in space exploration missions. To explore the vastness of space, humankind has built complex machines over the years, many of which have the responsibility to perform for years to come, for some it even means decades. The complexity is only going to increase further as we delve deeper and farther into space away from mother earth. According to a report published by McKinsey, by 2030, the space industry will be valued at $1 Tn and the number of active satellites will triple from the current 4000-5000. These figures only highlight the important role lubricants will be playing for fulfilling our space ambitions.
So, how are these lubricants different from what we use and what are different challenges faced in space?
First thing that comes to our mind is weightlessness. The natural force we take for granted on our mother earth is completely (almost) absent in space. This makes designing machines more complex and use of general pump mechanisms obsolete. To counter this engineers have designed lubricating systems based on property of surface tension
Another challenge faced by engineers is the significantly high evaporation rate of lubricants. The absolute pressure outside Earth’s environment is roughly 10^-13 torr. As there are no air molecules in near-vacuum conditions to push evaporated molecules back into liquid form, the rate of evaporation in space is significantly higher. Normal mineral oil evaporates much faster in space, while specialized lubricants like perfluorinated polyethers are formulated to minimize evaporation.
Once lubricant material is lost in space, it can form clouds around the satellite, potentially condensing on cold surfaces and forming a thin film. Sensitive surfaces on satellites, such as windows, spectrographs, and specialized lenses, can be severely affected by this film formation.
The vacuum of space also creates an unexpected issue: the absence of oxygen as a reactant. On Earth, a surface oxidation film typically plays a critical role in managing friction, wear, and tear. In space, once this initial oxidation film wears away, the friction coefficient tends to increase, and the load-carrying capacity of materials is limited due to the lack of oxygen, which affects the effectiveness of extreme pressure (EP) additives.
As we continue to push the boundaries of space exploration, the challenges of operating in such a harsh and unforgiving environment will only grow. From enabling smooth operations in the vacuum of space to preventing wear and tear on critical components, these specialized lubricants are the unsung heroes that keep our spacecraft and satellites functioning far from Earth. As we look to the future, the ongoing development of advanced lubricants will be key to sustaining our journey into the final frontier.
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