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
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.
Brittany Waletzko - ATT
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3. Brittany Waletzko - ATT
Propellant Mass
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
Brittany Waletzko - ATT
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4. Brittany Waletzko - ATT
Questions?
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5. Brittany Waletzko - ATT
Backup Information
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
Brittany Waletzko - ATT
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9. Output (in Newtons, Kilograms)
“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
“Environmentalpropmass” :
mm_cyl_month =
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
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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.
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Rocket Research Corporation. "Final Report for Monopropellant Hydrazine
Thruster System," <
de Weck, Oliver L. "Attitude Determination and Control." Massachusetts
Institute of Technology, 2001.
NASA. “Unmanned Space Project Management: Surveyor and Lunar Orbiter, SP-4901.” <
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