Lubrication in Space ppt

7/27/2019 Lubrication in Space ppt

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INTRODUCTION

The lubrication of moving mechanical parts in the environment ofspace presents problems not ordinarily encountered in conventionaloperating conditions on earth.

The special effects to be considered include those of weightlessness,radiation, temperature extremes, meteoroids and prolonged exposureto high vacuum.

From a practical viewpoint, the high vacuum provides the mostinteresting challenges in designing bearing systems & also

fundamental obstacle to the application of conventional designs,lubricants, and techniques.

The future space missions will involve advanced mechanical movingcomponents, space mechanisms that will need wear protection andlubrication, the Tribology practices used in space today are primarily

based on a technology more than 20 years old.


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With increasing demands and expanding operatingenvironments of spacecraft mechanisms, new lubricants

and additives are always under development. Since tribological failure is a leading cause of spacecraft

mechanism malfunctions, new lubricants must undergoextensive ground based testing to ensure they will meet

stringent mission requirements. In the past, lubricant selection has been based on

heritage, or actual flight experience. In early space flight,this approach worked well because of short mission lives

and minimal duty cycles. However, with todays longer missions and improved

components, new lubricant properties must be wellunderstood to ensure they will perform properly with the

system and the environment.


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Mechanisms


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Structure of tribological system


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Growth of tribology requirements with

advances in space


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Hydrodynamic, EHL, Mixed, and Boundary Lubrication: When selecting a lubricant for a mechanism component, many factors must

be considered. One of the most fundamental criteria is the mechanismsoperating regime

(boundary, mixed, or EHL), which

guides proper lubricant and additive

selection.

Depending on the third body type and

thickness, several different lubrication

regimes can be identified

and are depicted in the Stribeck curve.

It is plotted based on a

dimensionless parameter, ZN/P.

The Stribeck curve plots friction

coefficient as a function of

viscosity (Z), velocity (N), and

load (P).


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Re-lubrication Mechanisms

Because lubricant loss or degradation is a commonreason for space mechanism failure, mechanism re-lubrication methods have been examined. Since it isimpossible to service most spacecraft after launch, in-situ and remote relubrication systems have beenexplored to extend mission lives.

A newer re-lubrication concept is a small, in-situ,remotely controlled, lubricant reservoir. With thisconcept, the device is remotely activated wheneverthere is need for lubrication.


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Deployment sequence for a

spacecraft solar array


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CONCLUSION The above article has given an overview of the

current state of art tribology, some current andfuture perceived space lubrication problemareas, and some potential new LubricatingTechnologies.

The above article has also given an overview ofthe various Technologies used in lubrication ofthe space mechanisms, different type oflubricants, methods used in testing of lubricants,new lubricants to be used in future, re-lubrication technology etc.


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Thank you!

Lubrication in Space ppt

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