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Project Name

Solar Sail Project ProposalFebruary 7, 2007

Megan Williams (Team Lead)

Eric BlakeJon BraamRaymond HaremzaMichael HitiKory JenkinsDaniel KaseforthBrian MillerAlex OrdwayCasey ShockmanLucas Veverka

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Objective

To design a solar sail spacecraft with a sun observation objective. The spacecraft will carry a payload of 34 kilograms, and reach a final orbit of 0.48 AU and an inclination of 60 degrees.

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Requirements

Top Level Requirements1. The payload mass is 34 kg 2. The payload average power draw is 24.5

Watts 3. The final orbit should have a semi-major axis

of 0.48 AU and an inclination of 60 deg4. The launch vehicle will provide a hyperbolic

escape velocity of 0.5 km/s. A Delta II 7425 will be used for launch.

5. The structure will fit inside the selected launch vehicle.

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Expectations1. Explain the results of all trade studies.2. Demonstrate that the orbit control law will provide the

desired transfer trajectory3. Demonstrate that the attitude control law will provide

the desired sail orientation4. Demonstrate that the design meets the size and mass

requirements of the launch vehicle. This requires that you present one or more feasible methods for sail stowage and deployment.

5. Demonstrate that the power supply is sufficient for the mission.

6. Demonstrate that the spacecraft and its components will stay within allowable temperature ranges.

7. Demonstrate that the spacecraft can meet all of the pointing requirements simultaneously.

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Major TasksMajor Tasks (per website)1. Develop control laws for semi-major axis change and inclination change. The

outputs of the control law are angles that define the desired sail orientation. 2. Analyze the transfer time for different sail sizes. Choose a baseline size that is

consistent with proposed solar sail missions, and determine the corresponding transfer time.

3. Conduct a trade study between sliding mass and tip-thruster configurations4. Determine the data transfer rate and power requirements for data downlinks to

Earth. Assume 2 downlinks per week to the DSN (Deep Space Network).5. Conduct a trade study between conformal solar arrays and normal-pointing solar

arrays.6. Size the solar array to meet the total power requirements. Is a battery required?7. Prepare a thermal analysis of the solar sail project.8. Choose a configuration and compute the total mass and moment of inertia.

Treat the payload and surrounding systems (power, comm, etc.) as a point mass. Assume uniform distribution for the sail and masts.

9. Design a payload module.10. Complete a design for satellite actuation.11. Design an attitude control law that computes torques based on the angular

errors in sail orientation. Assume rigid body dynamics.

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Team Organization

Megan Williams (Team Lead)

Systems Integration & Manage-

ment

Structural Design

Orbit Control Design

Attitude Control Design

Power, Thermal

& Comm-

unication

Jon Braam

Kory Jenkins

Eric Blake

LucasVeverka

Brian Miller

Alex Ordway

Casey Shockman

Ray Haremza

Michael Hiti

DanielKaseforth

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Task BreakdownMajor Task 1: Develop control law for semi-major axis

change and inclination change to determine solar sail orientation.

• Subtask 1: Model the trajectory of the solar sail using MATLAB/Simulink (Eric Blake)

– Assume 2 Body Force Interaction Sun/Spacecraft • Subtask 2: Control Law (Dan Kaseforth, Lucas Veverka)

– Determine equations that will govern the control law – Output is an acceleration vector to determine sail

orientation • Subtask 3: Test this control law in the simulation (Eric

Blake) • Subtask 4 : Determine navigation system for inputs to

the control law. (Dan Kaseforth, Lucas Veverka)

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Task Breakdown

Major Task 2: Analyze transfer time for different sail sizes to determined optimum sail size. (Eric Blake)

• Subtask 1: Trade study between sail size and transfer time using simulation.

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Task BreakdownMajor Task 3: A trade study will be conducted to determine the best way

to control the solar sail attitude. The two methods considered will be a sliding mass system and tip thrusters. This task should take no more than two weeks.

• Subtask 1: A detailed analysis will be conducted on the sliding mass which will determine the following characteristics of the system (Alex Ordway):

– Power required– Rotation/Force provided– Accuracy– Weight/Volume considerations– Operation within necessary temperature ranges

• Subtask 2: A detailed analysis will be conducted on the tip thrusters which will determine the following characteristics of the system (Brian Miller) :

– Power required– Propellant types– Rotation/Force provided– Weight/Volume considerations– Accuracy– Operation within necessary temperature ranges

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Task Breakdown

Major Task 4: Determine the data transfer rate and power requirements for data downlinks to Earth. Assume 2 downlinks per week to the DSN. (Casey Shockman)

• Subtask 1: Determine communication method (laser, radar, etc.).

• Subtask 2: Determine pointing configuration.

• Subtask 3: Determine communication devices on spacecraft.

• Subtask 4: Compute data transfer rate for ½ AU.

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Task Breakdown

Major Task 5: Conduct a trade study between conformal solar array and normal-pointing solar array. (Ray Haremza)

• Subtask 1: Research conformal and normal-pointing solar array.

• Subtask 2: Investigate current solar panel usage at ½ AU.

• Subtask 3: Determine mass and volume contributed by the panels.

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Task Breakdown

Major Task 6: Size the solar array to meet total power requirements. (Mike Hiti)

• Subtask 1: Determine solar panel sizing based on a power draw of 24.5 Watts.

• Subtask 2: Analyze the effects of differing light intensity and how it corresponds to the distance from the sun.

• Subtask 3: Choose solar panel from existing suppliers or manufacturers.

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Task Breakdown

Major Task 7: Analyze the thermal properties of the solar sail spacecraft.

• Subtask 1: Analyze the thermal environment at ½ AU from the Sun to analyze material selection of solar sail and components. (Ray Haremza)

• Subtask 2: Analyze the thermal effects on electronic devices. (Casey Shockman)

• Subtask 3: Perform a thermal analysis of the solar sail housing. (Mike Hiti)

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Task BreakdownMajor Task 8: Choose a configuration and compute the total

mass and moment of inertia.• Subtask 1: Configuration of solar sail support

– Conceptual design of the solar sail support structure and geometry, such as a mast and boom structure. (Jon Braam)

– Detailed design of the support structure or mechanism for maintaining the sail shape. (Jon Braam)

– Structural analysis will be performed on the sail support structure to make sure that it meets all anticipated load requirements. i.e. bending of sail support booms. (Kory Jenkins)

– Zero level sizing based on existing designs and maximum mass, volume limit based on launch vehicle capabilities (Kory Jenkins).

– Refine satellite and sail sizing. (Kory Jenkins and Jon Braam)• Subtask 2: Solid model the solar sail configuration.

– Create solid models of the stowed and deployed sail structure. ( Kory Jenkins)

– Create solid model of stowed and deployed payload structure. ( Jon Braam)

– Calculate moment of inertia from solid model. (Jon Braam and Kory Jenkins)

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Task Breakdown

Major Task 9: Design a payload module.• Subtask 1: Perform a trade study of existing

satellite configurations and select a design for the payload module. (Jon Braam)

• Subtask 2: Detailed layout of payload module configuration. (Jon Braam)

• Subtask 3: Select materials for payload module structure that meet environmental considerations and justify with calculations as needed. (Kory Jenkins)

• Subtask 4: Design a connection between the sail support structure and the payload module. (Jon Braam)

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Task Breakdown

Major Task 10: Complete a design for the satellite actuation.

• Subtask 1: Complete a detailed design of the satellite, sail, and peripherals (i.e. antennae) in stowed configuration. (Jon Braam, Kory Jenkins)

• Subtask 2: Develop a detailed method of deploying the sail and any peripherals needed by other subgroups. (Kory Jenkins, Jon Braam)

• Subtask 3: Design a mechanism for orienting the sail for attitude control. (Jon Braam)

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Task BreakdownMajor Task 11: The attitude control laws will be

calculated and tested. This task will take most of the semester due to required input from other groups. Due to this input the model will have to be continuously updated. (Alex Ordway & Brian Miller)

• Subtask 1: The torques required to overcome errors in the sails orientation will first be calculated.

• Subtask 2: Using the torques computed, the locations of the control devices, and the moments of inertia, the force required can be calculated. These forces will then be used to write the attitude control equations.

• Subtask 3: These equations will then be coded into Matlab and Simulink to ensure they will work.

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Schedule

GANTT CHART

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Questions• Is there a time limit for the attitude adjustment?• Do you think that it sounds reasonable to make the

navigation system a subtask of the control laws task?• Should we spend time looking into other means of

attitude control (besides tip thrusters and sliding mass) or just stick to looking in to those?

• Carbon fiber as a solar sail material (new technology = risky?)

• Do you have suggestions about creating attitude control laws?

• Is it necessary to actuate the sail independently of the satellite payload module? Could we reorient the entire satellite and just move the antenna as needed?