Solar Sail

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Solar Sail. Department of Aerospace Engineering and Mechanics AEM 4332W – Spacecraft Design Spring 2007. Team Members. Solar Sailing:. Project Overview. Design Strategy. Trade Study Results. Orbit. Eric Blake Daniel Kaseforth Lucas Veverka. Eric Blake.

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Solar Sail

Department of Aerospace Engineering and Mechanics

AEM 4332W – Spacecraft Design

Spring 2007

Eric Blake

Daniel Kaseforth

Lucas Veverka

Eric Blake

Optimal Trajectory of a Solar Sail: Derivation of Feedback Control Laws

Recall Orbital Mechanics
• The state of a spacecraft can be described by a vector of 6 orbital elements.
• Semi-major axis, a
• Eccentricity, e
• Inclination, i
• Right ascension of the ascending node, Ω
• Argument of perihelion, ω
• True anomaly, f
• Equivalent to 6 Cartesian position and velocity components.
Equations of Motion

= Sail Lightness Number

= Gravitational Parameter

Problem: Minimize Transfer Time

By Inspection:

Transversality:

Solution
• Iterative methods are needed to calculate co-state boundary conditions.
• Initial guess of the co-states must be close to the true value, otherwise the solution will not converge.
• Difficult
• Alternative: Parameter Optimization.
• For given state boundary conditions, maximize each element of the orbital state by an appropriate feedback law.
Orbital Equations of Motion

= Sail Lightness Number

= Gravitational Parameter

Maximizing solar force in an arbitrary direction

Maximize:

Sail pointing for maximum acceleration in the q direction:

Locally Optimal Trajectories
• Example: Use parameter optimization method to derive feedback controller for semi-major axis reduction.
• Equations of motion for a:

Feedback Law:

Use this procedure for all orbital elements

Method of patched local steering laws (LSL’s)
• Initial Conditions: Earth Orbit
• Final Conditions: semi-major axis: 0.48 AU inclination of 60 degrees
Global Optimal Solution
• Although the method of patched LSL’s is not ideal, it is a solution that is close to the optimal solution.
• Example: SPI Comparison of LSL’s and Optimal control.
Conclusion
• Continuous thrust problems are common in spacecraft trajectory planning.
• True global optimal solutions are difficult to calculate.
• Local steering laws can be used effectively to provide a transfer time near that of the global solution.

Lucas Veverka

Temperature

Orbit Implementation

Daniel Kaseforth

Control Law Inputs and Navigation System

Structure

Jon T Braam

Kory Jenkins

Jon T. Braam

Structures Group:

Primary Structural Materials

Design Layout

3-D Model

Graphics

Primary Structural Material

Weight and Volume Constraints

• Delta II : 7400 Series
• Launch into GEO
• 3.0 m Ferring
• Maximum payload mass: 1073 kg
• Maximum payload volume: 22.65 m3
• 2.9 m Ferring
• Maximum payload mass: 1110 kg
• Maximum payload volume: 16.14 m3
Primary Structural Material

Aluminum Alloy Unistrut

• 7075 T6 Aluminum Alloy
• Density
• 2700 kg/m3
• 168.55 lb/ft^3
• Melting Point
• ? Kelvin

Picture of Unistrut

Primary Structural Material
• Density
• Mechanical Properties
• Allowing unistrut design
• Decreased volume
• Thermal Properties
• Capible of taking thermal loads
Design Layout
• Constraints
• Volume
• Thermal consideration
• Magnetic consideration
• Vibration
Design Layout
• Unistrut Design
• Allowing all inside surfaces to be bonded to
• Titanium hardware
• Organization
• Allowing all the pointing requirements to be met with minimal attitude adjustment
Design Layout
• Large Picture of expanded module
3-D Model
• Large picture
3-D Model
• Blah blah blah (make something up)
Graphics
• Kick ass picture
Graphics
• Kick ass picture
• Blah blah blah
Why I deserve an “A”
• Not really any reason but when has that stopped anyone!
Kory Jenkins

Sail Support Structure

Stress Analysis

Materials

Sail Deployment

Brian Miller

Alex Ordway

Brian Miller

Tip Thrusters vs. Slidnig Mass

Attitude Control Simulation

Alex Ordway60 hours worked

Attitude Control Subsystem Component Selection and Analysis

Design Drivers
• Meeting mission pointing requirements
• Meet power requirements
• Meet mass requirements
• Cost
• Miscellaneous Factors
• Sliding Mass vs. Tip Thruster Configuration
• Idea behind sliding mass
• Sliding mass ACS offers
• Low power consumption (24 W)
• Reasonable mass (40 kg)
• Low complexity
• Limitations
• Unknown torque provided until calculations are made
• No roll capability
• Initially decided to use combination of sliding mass and tip thrusters
• Goodrich HD1003 Star Tracker primary
• Bradford Aerospace Sun Sensor secondary
• ACS
• Four 10 kg sliding masses primary
• Driven by four Empire Magnetics CYVX-U21 motors
• Three Honeywell HR14 reaction wheels secondary
• Six Bradford Aero micro thrusters secondary
• Dissipate residual momentum after sail release
• Primary
• Decision to use star tracker
• Accuracy
• Do not need slew rate afforded by other systems
• Goodrich HD1003 star tracker
• 2 arc-sec pitch/yaw accuracy
• 3.85 kg
• 10 W power draw
• -30°C - + 65 °C operational temp. range
• \$1M
• Not Chosen: Terma Space HE-5AS star tracker
• Secondary
• Two Bradford Aerospace sun sensors
• Backup system; performance not as crucial
• Sensor located on opposite sides of craft
• 0.365 kg each
• 0.2 W each
• -80°C - +90°C
ACS
• Sliding mass system
• Why four masses?
• Four Empire Magnetics CYVX-U21 Step Motors
• Cryo/space rated
• 1.5 kg each
• 28 W power draw each
• 200°C
• \$55 K each
• 42.4 N-cm torque
ACS
• Gear matching- load inertia decreases by the gear ratio squared. Show that this system does not need to be geared.
ACS
• Three Honeywell HR14 reaction wheels
• Mission application
• Specifications
• 7.5 kg each
• 66 W power draw each (at full speed)
• -30ºC - +70ºC
• 0.2 N-m torque
• \$200K each
• Not selected
• Honeywell HR04
ACS
• 0.4 kg each
• 4.5 W power draw each
• -30ºC - + 60ºC
• 2000 N thrust
• Supplied through N2 tank
Attitude Control
• Conclusion
• Meets and exceeds mission requirements
• Marriage of simplicity and effectiveness
• Redundancies against the unexpected

Power, Thermal and Communications

Raymond Haremza

Michael HitiCasey Shockman

Raymond Haremza

Thermal Analysis

Solar Intensity and Thermal Environment

Film material

Thermal Properties of Spacecraft Parts

Future Work

Communications

Michael Hiti

Power

Acknowledgements
• Stephanie Thomas
• Professor Joseph Mueller
• Professor Jeff Hammer
• Dr. Williams Garrard
• Kit Ru….
• ?? Who else??