The universe is an ocean of mysteries. The space science community has been working very hard to solve this massive puzzle. Space exploration missions have played a key role in enhancing our knowledge about planets, comets, space phenomenon’s and theories of birth of universe. NASA, ISRO, ESA and many other space organizations are in a race to be the first one to seek all the answers and become a prime leader in futuristic space travel and space technology. Space programs with or without humans is an expensive deal for any country’s government as it requires a huge sum of money to fund various requirements. The cost of Hubble mission was around 14 Billion Dollars, Curiosity – 2.6 Billion Dollars, ESA’s Rosetta – 1.4 Billion Dollars and ISRO’s Mars Mission costed around 74 Million Dollars. The space agency’s prime focus is on two things 1) Success of mission 2) Increasing the life expectancy of spacecrafts and satellites .
Tribological problems can hinder the performance of many mechanical parts used in spacecraft’s and satellites which can even lead to failure of the whole mission. Galileo Spacecraft launched in the year 1989 conceived a tribological issue when its antenna which was supposed to open fully, opened only half after the launch. The coated antenna alignment pins had suffered loss of lubricant as the dry film lubricant used had actually galled and seized . In August 1989, the scanning platform of Voyager 2 failed due to working out of the lubricant in gear drives. In April 1967, excessive friction in the parachute system resulted in explosion of manual craft ‘Soyuz-1’ .
Bushings, roller and sliding element bearings, extension and retraction mechanisms, slip rings, docking systems, solar array drives, reaction wheels and gyroscopes are some of the major friction sensitive units which are common in space vehicles and satellites and may require lubrication at some point or a continuous lubrication system .
Lubricants used in space are different than used on Earth. The space lubricant has to withstand extreme pressure and temperature, weightlessness/no gravity, no oxygen and many more obstacles. Theses lubricants are tested rigorously in labs to see if they satisfy outer earth environment. Solid lubricants such as Molybdenum Disulphide (MoS2) is generally used for low speed systems like solar array drives, sensors, and antenna scanners. Liquid lubricants such as mineral oils, silicon fluids, esters, synthetic hydrocarbons, perfluoropolyethers (PFPE), silahydrocarbons and ionic liquids are generally used for high speed moving mechanical systems. As a novel approach, high pressure gas films can also be used to lubricate a moving component. Friction and wear resistance is also facilitated by coatings. Normally Titanium Carbide (TiC) and Diamond like Carbon (DLC) coatings are used for coating mechanical parts used in space mechanisms .
Tribometers used for space application are generally vacuum tribometers. These vacuum tribometers allow researchers to perform tests at controlled vacuum conditions and at very low pressure and temperature. Vacuum tribometers generally consists of a vacuum test chamber equipped with a sliding test bench. Depending upon the type of requirement, the setup can be pin-on-disc, pin-on-plate or any other .
With better solutions of tribological problems, the life of mechanical parts can be increased which in turn will promise higher success rate of missions. Also the amount of money spent on maintenance missions to rectify such issues can be saved.
- “The Real Cost Of NASA Missions.” Popular Science. Web. 27 Oct. 2016.
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- Modern Methods of Construction Design. Proceedings of ICMD 2013. Berlin: Springer, 2014. edited by Ladislav Ševĉik, Petr Lepšík, Michal Petrů, I. Mašín, Rudolf Martonka” Section – Vacuum Tribometer Device pg. 598, International Conference of Machine Design Departments. Google books preview only https://tinyurl.com/y9cchbyy
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