Attitude Control Thrusters with Low Thrust Orbit Trajectories Josh Lukasak Attitude Group Lead Attitude Problem Main Thruster Offset is the largest source of attitude perturbations Electric Propulsion uses a constant thrust for the orbit transfer phase ID: 728425
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Slide1
Propellant Requirements
Attitude Control Thrusters with Low Thrust Orbit Trajectories
[Josh Lukasak] [Attitude Group Lead]Slide2
Attitude Problem
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.
[Josh Lukasak] [Attitude Group Lead]
(1)Slide3
Mass Estimates
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.
[Josh Lukasak] [Attitude Group Lead]
(2)Slide4
Back Up Slides
[Josh Lukasak] [Attitude Group Lead]
(3)Slide5
Reaction Wheel
Vectronic Aerospace Reaction Wheel Type RW-01
[Josh Lukasak] [Attitude Group Lead]
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Nominal Torque
20
mNm
Mass
1.8 kg
Power
4 W
Temperature Range
-20
C to 70 CSlide6
Mass Calculations
M=F x rM is the induced momentF 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 momentg 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
[Josh Lukasak] [Attitude Group Lead]
(5)Slide7
Sample Calculations
[Josh Lukasak] [Attitude Group Lead](6)Slide8
Possibility of Thruster Gimbals
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.
[Josh
Luksak
] [Attitude Group Lead]
(7)Slide9
References
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 2002Rauschenbakh, Boris, Michael Ovchinnikov, and Susan McKenna-
Lawlor
.
Essential Spaceflight Dynamics and
Magnetospherics
.
Dordrecht, The Netherlands:
Kluwer
Academic Publishers, 2003.
[Josh Lukasak] [Attitude Group Lead]
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