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Impact of Environmental Forces on Attitude Control During Translunar Phase

This study by Brittany Waletzko evaluates the environmental forces affecting attitude control during the translunar phase of spacecraft. It assesses worst-case scenarios for propellant mass budget while considering factors like solar effects and Earth's magnetic field. Using geometries of a right circular cylinder and cube, torque values were analyzed, revealing potential propellant requirements and corrections with reaction wheels. Historical comparisons indicate lower propellant needs than previously assumed. MATLAB scripts detailing environmental forces and propellant mass are included for further insights.

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Impact of Environmental Forces on Attitude Control During Translunar Phase

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  1. Environmental Perturbing Forces & Effect on Attitude Control Brittany Waletzko Translunar Phase Environmental Forces Effect on Propellant Mass Budget Brittany Waletzko - ATT

  2. Environment Affects Control BrittanyWaletzko- ATT Obtain a “worst case” needs assessment for attitude control due to environment during translunar phase Assumed right circular cylinder 3m across x 12m long or cube 1.5m side Many values tentative, based historically Included solar effects, Earth’s magnetic field, spacecraft gas leaks and emitted power, etc. <1>

  3. Propellant Mass BrittanyWaletzko- ATT Sum of torques on order of 1.5x10-3 Nm for cylinder, 1.5x10-5 Nm for cube Even if we could constantly thrust to overcome this for a month, cube would only require 0.3kg propellant For max thruster lifetime, upper bound is 0.006kg propellant for cube Most likely will correct with reaction wheel <2>

  4. Questions? BrittanyWaletzko- ATT <3>

  5. Backup Information BrittanyWaletzko- ATT Many engineering judgments made about logical input values; compare to historical average of about 12 kg propellant for entire attitude control system Based historically (i.e. Spirit-1 and Lunar Surveyor) The forces are treated as magnitude only—the spacecraft should not actually experience the environmental torque reported See attached MATLAB scripts on environmental forces and propellant mass <4>

  6. Brittany Waletzko - ATT <5>

  7. Brittany Waletzko - ATT <6>

  8. Brittany Waletzko - ATT <7>

  9. Output (in Newtons, Kilograms) • “Environmentalpropmass” : • mm_cyl_month= • 30.8571 • mm_cyl_5000 = • 0.0595 • mm_cyl_50000 = • 0.5952 • mm_cube_month= • 0.3086 • mm_cube_5000 = • 5.9524e-004 • mm_cube_50000 = • 0.0060 Brittany Waletzko - ATT “Environmental” : Felec = 1.5231e-005 Fref = 2.8793e-022 Ftherm = 1.9623e-022 Fscrad = 4.0027e-006 Fswind= 5.1750e-009 Fmag = 2.1599e-013 Fexp = 7.9937e-007 Ftotal = 2.0039e-005 <8>

  10. Primary References (also see MATLAB scripts) Longuski and Konig. A Survey of Nongravitational Forces and Space Environmental Torques with Applications to the Galileo Spacecraft.AIAA/AAS Astrodynamics Conference: 9-11 Aug 1982. Rauschenbakh, Boris, Michael Ovchinnikov, and Susan McKenna-Lawlor. Essential Spaceflight Dynamics and Magnetospherics. Dordrecht, The Netherlands: Kluwer Academic Publishers, 2003. Monopropellant Hydrazine Thrusters. Astrium Space Propulsion. 21 Jan 2009. <http://cs.astrium.eads.net/sp/SpacecraftPropulsion/MonopropellantThrusters.html> Rocket Research Corporation. "Final Report for Monopropellant Hydrazine Thruster System," 1965. <http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670030394_1967030394.pdf> de Weck, Oliver L. "Attitude Determination and Control." Massachusetts Institute of Technology, 2001. NASA. “Unmanned Space Project Management: Surveyor and Lunar Orbiter, SP-4901.” < http://history.nasa.gov/SP-4901/table.htm> BrittanyWaletzko- ATT <9>

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