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# Solar Sail PowerPoint PPT Presentation

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.

Solar Sail

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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

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

Time (years)

### 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

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

• The blanks will be filled in soon

• 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??