P19101: CubeSat Solar Sail
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

What did your team plan to do during this phase?

What did your team actually accomplish during this phase?

Functional Decomposition

In order to actually understand what we need build we did a function decomposition of the cubesat. We won't be working on all of the functions such as the communication system but we included it to be through and for future senior design projects.

Functions include:

Using the function list we created two different types of charts to show the decomposition. The first image shows the different functions branching down. The lower branching functions explain how you complete the above function.

Functional Decomposition Tree

Functional Decomposition Tree

The second image shows a flowchart of the functions detailing the order of the functions and how they interact with each other. The light blue box shows the processes that the cubesat will do while everything outside of that box is our inputs and outputs.

Functional Decomposition Flow Chart

Functional Decomposition Flow Chart

Benchmarking

We looked into several of the other solar sail cubesat missions. We found out about them though the SPEX team, last year'S team's (P18101) benchmarking table, and google.

Some major differences our project will have with these are funding, time, and man power.

Benchmarking

Benchmarking

Concept Development

Using the functions we developed different parts of the cubesat for which we could have different designs. These parts are listed below.

For power generation we wanted to be able to generate as much as possible so that we would be able to power our systems and any future systems added on. We also had to keep in mind that the solar sail would be out the majority of the time and half of the solar sail would be block from the sun by the solar sail. If there solar panels on both side then the cubesat will always have power but it will make the cubesat more complex.

For the sail deployment mechanism we want enough torque to be able to deploy the booms and the pull the sail out. It also needs to be able to lock so that when the motor is off the booms won't get pushed in somehow.

Currently for sail tracking we have black paint stripes on the the booms that a sensor will count the stripes to monitor how far the booms deploy. We noticed that the paint is already rubbing off so we are worried about how long this mechanism will last. We also don't know how well this mechanism will work i space. The paint might not be space worthy of the sensor might have trouble tracking the black color on the black background of space.

Using these we were able to generate a morphological chart.

Feasibility: Prototyping, Analysis, Simulation

How Much Power Can We Generate

This section is looking into the maximum amount of power that can be generated on the 3U cubesat at a given time. Assuming placement of the solar cells is all on one side of the sail, in order to maximize the power that is able to be generated, the calculations are as follows:

Using this metric the below MATLAB script can approximate the kWh power generation per orbit, taking into account varying solar panel configurations, manual rotations, and orbit duration.

PV_kWh_Estimation.m

Max sail in 1U

This section is looking the amount of sail we can actually fit in 1U. The previous team selected solar sail material that is 0.5 mil thick. By folding it we will assume the crease will cause a a displacement that is half the width of the material.

Width/thickness=0.1m/(1.27+.635)*10^-5m=5249 layers

5249 layers*0.1m*0.1m= 52m^2 area of solar sail

So we estimate that a total of 52 m^2 can be fit into 1 U of the cubesat.

Geneva Cam Torque

The torque calculations for the geneva cam are based on the max torque input from the current motor and the current size for the geneva disc.

public/Photo Gallery/GenevaCalc2.jpgpublic/Photo Gallery/GenevaCalc1.jpg

Input Motor Torque: 8.56 inlb

Geneva Disc Size: .5568 in

Torque Output:

Worm Gear Torque

Will be different for any set of two gears. Based on 75% efficiency, current motor torque, and an inexpensive set of 27:1 ratio gears;

Torque Output = 173 inlb

Torque test on Cubesat

A custom shaft is being machined to test the torque required to deploy the sail using the current geneva cam. This will give us a benchmark to see if we should switch to the worm gear or change the number of lobes on the geneva cam. This will also give us a better idea of whether or not we need a higher torque motor as suggested by the last team.

Sensor Data acquisition

How much data needs to be collected to determine how far the sail has been deployed. Assume:

5m * (10min/m) = 50min to deploy

50min * 60sec/min = 3000 sec to deploy

3000 sec * 8bits/sample * 2samples/sec = 48000bits

48000bits * 4 sensors = 192000 bits/8 = 24000 bytes ~= 23kB

Morphological Chart and Concept Selection

After identifying the key functions of the CubeSat, functional concepts were derived, and are listed in the table below.

Concept Matrix

Concept Matrix

Based on team input,the functional concepts were compiled into system design concepts summarized in the table below.

Concept Summary

Concept Summary

Concept Selection

We will select our concept from the following criteria.

Using these seven criteria we created a pugh chart, which can be seen below. We decided to weigh our criteria as well with 9 being most important and 1 being least. We did this because we thought power generation and torque capabilities were much more important than criteria like complexity. Our pugh chart uses the colors from the morph chart to show the concept being evaluated. We randomly picked one of our concepts to be our datum.

Pugh Chart

Pugh Chart

Two of our concepts came out tied for first place so we made another pugh chart with just those two to compare them against each other. The only difference between these two concepts is the motor deployment mechanism. The one uses a Geneva 5 cam while the other uses a worm gear. The worm gear concept game out on top due to it's higher torque.

Pugh Chart

Pugh Chart

Systems Architecture

The first system image is of the concept for the finished CubeSat that would be needed for launch. The simple block diagram is designed only to illustrate where our portion of the project fits into the overall scheme. This also highlights what is next for a team looking to take on a continuation of this project in the future. Future systems include:

- Communications system (including transceiver and antenna design)

- Attitude control board (including algorithms required to calculate attitude deltas)

- Attitude sensors to create a closed loop attitude system

- Attitude actuator, likely either torque coils or reaction wheels/spinning masses. Used to physically move the satellite based on the Attitude control algorithms.

Functional Decomposition Tree

Functional Decomposition Tree

This second image is a slightly more detailed system design of the elements which will be taken on during this MSD term. It is important to note that this diagram also includes lines indicating the transfer of power/energy (red lines), as well as transfer of data and commands (blue lines). The main functional tasks covered in this diagram are the generation and storage of power, which is then used to deploy the solar sail.

Functional Decomposition Tree

Functional Decomposition Tree

Risk Assessment

The Risk List has been updated thought our the design phase. The current list is as follows:
Risk Assessment

Risk Assessment

Design Review Materials

See the link below for the design review agenda.

DR Agenda

After the meeting we complied a list of comments from the our advisor and customer.

Meeting Notes

Plans for next phase

For the next phase, in three weeks, we plan to start the detailed design of our individual systems. We will take our system level design and further break the systems down into more preliminary designs to move forward with. Each team member has several individual tasks assigned to them, which are listed below.

Adam Stock

Preliminary detailed design for solar panel deployment

Assess solar sail deployment drive methods from those evaluated in the Pugh chart (Geneva Cam vs. Worm Gear)

Develop folding methods for the solar sail to easily deploy

Adapt the current 2U cubesat into a 3U design

Brett Saxe

Research and work on acquiring solar panels for the cubesat

Begin Development of Bill of Materials consistent with detailed designs

Jarrett Pischera

Develop folding methods for the solar sail to easily deploy

Preliminary detailed design of power conditioning electronics

Preliminary detailed design of power storage electronics

Apply for NYS NASA Space Consortium Grants

Kristin Angel

Preliminary detailed design for solar panel deployment

Develop folding methods for the solar sail to easily deploy

Assess solar sail deployment drive methods from those evaluated in the Pugh chart (Geneva Cam vs. Worm Gear)

Adapt the current 2U cubesat into a 3U design

Apply for NYS NASA Space Consortium Grants

Nathan Lindberg

Continue research into the cubesat electronics devkit

Determine if the cubesat devkit will be sufficient to control the craft

Preliminary detailed design of the programming structure for general control of the cubesat


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