Thermal Modeling, Analysis, and Control for ASTUSat

Abstract

Astusat Is The First 3u Cubesat In Ethiopia Under Development By Space Technology Institute Of Adama Science And Technology University Which Have A Technical Mission Of Taking Colored Picture Of The Earth From Low Earth Orbit. The Satellite Will Be Deployed Into Orbit From The International Space Station Which Is Located At An Altitude Of 400 Km. The Satellite Contains Multiple Subsystems, From Those Subsystems Thermal Control Subsystem Is The One Which Maintains All Components Of The Satellite Within Their Operating Temperature Limit During All Mission Phases. The Astusat Program Creates The Opportunity For Graduate Students To Participate On Different Subsystem Designs Of The Satellite. The Aim Of This Thesis Is To Develop Thermal Model, To Perform Thermal Analysis, And To Select The Required Thermal Control System Hardware?�?S So That The Satellite Survives The Space Environment. In The Thesis The Main Mission Parameters Of Astusat And The Current Spacecraft Design Are Presented, In Order To Fix The Boundary Conditions And The Thermal Environment Used For Thermal Modeling And Analysis. In The Document Two Thermal Analysis Were Performed And Presented Based On The Complexity Of The Models. The Preliminary Transient Analysis Is Performed By Developing A Simplified Equation From Energy Balance Equation And Solved Using Euler Explicit Method In Matlab Environment. In The Analysis Two Boundary Conditions Were Identified Which Are Labeled As The Worst Hot And Cold Scenario And The Transient Temperature Of The Satellite Were Predicted At These Conditions. The Results Obtained Reveled That The Satellite Temperature Fluctuates Between 86.6 And 89.3 Oc During Worst Hot Scenario And Between 17.9 And 34.48 Oc During Worst Cold Scenario. The Detail Thermal Modeling And Analysis Is A Finite Element Model Of The Satellite Developed Within Femap Tmg Environment By Including Heat Loads Such As Subsystems Internal Heat Generation And Environmental Thermal Radiations (Infrared, Albedo, Solar Flux). This Model Is Solved And The Transient Temperature Of Satellite Components Are Extracted And Presented. The Results Showed That The Cubesat Can Reach Temperature Between +101.5 And -24.5 Oc For Worst Hot Scenario, And +65.5 And -41.3 Oc For Worst Cold Scenario. These Results Served As A Basis For The Development Of Thermal Control System.The Finite Element Model Has Been Refined With Different Spacecraft Configuration And Solved To Set The Requirements Applicable To The Thermal Control System Of The Satellite. The Results Showed That A Basically Passive Thermal Control Technique Is Sufficient To Maintain Most Spacecraft?�?S Components Within Their Temperature Range When Appropriate Thermal Tapes Or Coatings And Thermal Washers Are Provided. Therefore, The Thermal Modeling Results Obtained In This Thesis Can Easily Be Adjusted To The Actual Input Data, And Design Arrangement Of Payloads And Subsystems To Generate Thermal Performance Of Spacecraft Astusat Which Is Critically Needed Before Conducting Ground Vacuum Chamber Thermal Performance Test Of Astusat At The Laboratory Of Space Technology Institute Of Astu.