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Propellant Requirements

Propellant Requirements . Attitude Control Thrusters with Low Thrust Orbit Trajectories. Attitude Problem. Main Thruster Offset is the largest source of attitude perturbations. Electric Propulsion uses a constant thrust for the orbit transfer phase.

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Propellant Requirements

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  1. Propellant Requirements Attitude Control Thrusters with Low Thrust Orbit Trajectories [Josh Lukasak] [Attitude Group Lead]

  2. Attitude Problem [Josh Lukasak] [Attitude Group Lead] (1) • Main Thruster Offset is the largest source of attitude perturbations. • Electric Propulsion uses a constant thrust for the orbit transfer phase. • Attitude control thrusters must be used along with reaction wheels. • Assumptions • Cubic craft with 1 meter sides, .5 N thrust, and an engine offset of 5 cm flying a 1 month transfer orbit.

  3. Mass Estimates [Josh Lukasak] [Attitude Group Lead] (2) Using basic kinematics the torque created by offset is 0.025 Nm. If a reaction wheel with a nominal torque of 0.02 Nm is used in the opposite angular direction the total torque is reduced along with the propellant mass. Using these torques the total Monopropellant Hydrazine mass required is 14 kg.

  4. [Josh Lukasak] [Attitude Group Lead] (3) Back Up Slides

  5. Reaction Wheel [Josh Lukasak] [Attitude Group Lead] (4) Vectronic Aerospace Reaction Wheel Type RW-01

  6. Mass Calculations [Josh Lukasak] [Attitude Group Lead] (5) • M=F x r • M is the induced moment • F is the force or thrust • r is the radius from the force to the center of mass • m is the time averaged mass • M is the induced moment • g is the gravitation constant of 9.80665 m/s^2 • Isp is the specific impulse of Monopropellant Hydrazine • L is the distance from the thruster to the center of mass

  7. Sample Calculations [Josh Lukasak] [Attitude Group Lead] (6)

  8. Possibility of Thruster Gimbals [Josh Luksak] [Attitude Group Lead] (7) Thruster Gimbals are a distinct possibility for reducing mass and perhaps cost for attitude control. Essentially the gimbals change the direction of the thrust vector and control the attitude of the spacecraft. NASA research shows that these systems can be as small as 2.6 kg.

  9. References [Josh Lukasak] [Attitude Group Lead] (8) Vectronic Aerospace Reaction Wheel Type RW-01 Vectronic Aerospace 28 January 2009 http://www.vectronic-aerospace.com/html/reaction_wheel.html Steven Oleson, Leon Gefert, Scott Benson, and Michael Patterson Mission Advantages of NEXT: NASA's Evolutionary Xenon Thruster http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211892.pdf. September 2002 Rauschenbakh, Boris, Michael Ovchinnikov, and Susan McKenna-Lawlor. Essential Spaceflight Dynamics and Magnetospherics. Dordrecht, The Netherlands: Kluwer Academic Publishers, 2003.

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