P19101: CubeSat Solar Sail
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

Fabrication

We have been machining the cubesat for the past several weeks. The sheet metal was cut on the waterjet. The other parts were manufatured using the lathe and end mill.
Using the vertical mill

Using the vertical mill

The worm gear assembly was fabricated first. We bought all the gears, pinion and worm, but the mounting systems had to be made.

Worm Gear Subsystem

Worm Gear Subsystem

The bottom of the cubesat has a complex hinge arrangement. This hinge arrange will deploy the solar panels.

Bottom Hinge Assembly

Bottom Hinge Assembly

Bottom Hinge Assembly

Bottom Hinge Assembly

Below is the most recent version of the deployment system.

Bottom Hinge Assembly

Bottom Hinge Assembly

Test Results Summary

Deployment Testing

Initial Deployment Test

During our first trial of deployment using just the full sized booms we found some problems. The booms initially started unwinding but then they expanded and got stuck inside of the cubesat. The motor then started winding the booms back up in the opposite direction. This can be seen in the picture below.
Booms Binding Backwards

Booms Binding Backwards

Balloons

We planned to use balloons to keep the booms from falling while testing the deployment to simulate the lack of gravity but after testing a balloon and weighing the tape measures. We calculated that you would need two balloons per foot of tape measure. Since this would cause us to need almost 100 balloons we had to change our method of boom stabilization.
Balloon test

Balloon test

Deployment with Shorter Booms

We tested our deployment with shorter booms. The 37 inches booms did not extend. We finally got the deployment working with the booms that last years team used. The picture of them unfurling can be seen in the picture below. These booms are about a 20 inches long. Since these booms are very short they are able to expand a lot and do not rub against each other as much which could be a reason these booms will actually expand. We want much longer booms in this cubesat in order to have bigger sails.
Short Booms Unfurling

Short Booms Unfurling

Using Guides

For better deployment we tried adding guides into the deployment system that will help keep the tape measure rolled tight and help guide the tape measure out their intended exit. Our guides still caused the booms to jam. We also hot glued them in and the force would build up and the guides would break off at the hot glue. We would hold the guides in place after they would break but we still didn't notice much progress with the booms expanding.
First guide System tested

First guide System tested

Double Sided Tape Test

We next tested the booms using double sided tape. We wanted to know if it would have an easier time expanding if the booms were held together at the center. So double sided tape was applied between the booms starting about a foot from the ends of the tape measure that would exit the cubesat. The booms started extending from the cubesat better than any previous efforts. There was a problem once the tape got out to the opening though. One piece got stuck to the cubesat and started causing the booms to bind backward. We are going to look into a center piece which will hold the tape measure together and not involve tape.

Metal Plate Addition

After the tape test we decided to use a metal plate to try and keep the tape measure roll contained. We attached a rough machined "circular" plate to the top of our spool which will spin with the cup.

Metal Plate

Metal Plate

The plate did helped the tape measure unroll. We hadn't been able to get the half boom deployed at all before and using this method we were able to deploy it all the way.

Fully Extended Half Size Booms

Fully Extended Half Size Booms

Since this worked we have designed a new spidle that will have a plate on the top and the bottom, similar to a spool of thread. It was tested with the half size booms successfully. Going forward we will test with the full size booms and eventually with the sails attached.

Spool Deployment Design

Spool Deployment Design

Nichrome Testing

To insure the nichrome wire will cut our fishing line we ran some tests.Various strands of nichrome wire were used to cut the fishing line using 12 volts from a power supply. 1 nichrome wire by its self did not cut our fishing line right away. It melted the fishing line a bit but we want the fishing line cute fairly quickly. Using two strands of nichrome wire the fishing line cut when pressing the nichrome and the fishing line together which can be seen here.

Two strands of nichrome

Two strands of nichrome

We will not be able to press the two together in space. We will pull them taunt against each other so there will only be a small amount of force. To test this we made a loop of fishing lines with the nichrome holding it up. Using just gravity the 2 strands of nichrome did not cut the fishing line. Three strands of nichrome wire cut the fishing line when only gravity held the two lines together. The fishing line will also be in an "X" fomartation holing the top of the cubesat closed so we tested if the 3 strands of nichrome would cut two strands of fishing line. This test can be seen here.

"X" formation of fishing line cut

Our overall test results for the nichrome wire can be seen below.

Nichrome test results

Nichrome test results

Electronics

Prototype and Test

Using prototype boards purchased last semester, a prototype of the power system was assembled and tested on a breadboard. This included the power multiplexer, battery charging, and the 5V and 12V boost converters.
Breadboard prototype of power system

Breadboard prototype of power system

PCB Design

Using the successful tests from the breadboard prototype, the schematic of the power system was finalized and a board was designed. This board incorporates the following features:
Schematic of microcontroller pin breakout

Schematic of microcontroller pin breakout

Schematic of Power System

Schematic of Power System

With the schematic diagram complete, a board was laid out. This board was designed to be modular and follow a stackable architecture for subsequent daughter boards. The pin assignments of the standard are found below:

Board Dimension Specification

Board Dimension Specification

This stackable architecture will allow multiple daughter boards to each have access to any digital or analog pin of the microcontroller, as well as any of the three power sources.

Mockup of the baseboard

Mockup of the baseboard

Mockup of the stacking boards

Mockup of the stacking boards

The baseboard has been ordered from oshpark, as well as all components from digikey. The baseboard has the standard connections described above as well as:

Front of PCB

Front of PCB

Back of PCB

Back of PCB

Design Documentation

Interactive Systems Architecture

An effort was undertaken to create a comprehensive design architecture for the sake of quickly referencing any design element in the current project phase, and increasing the ease of analyzing the current design in future phases. Developed on the framework of the functional decomposition created in MSDI, the architecture shown in the captures below organizes each and every component of the cube sat systematically. As components are organized into larger subsystems, diagrams such as electrical schematics, CAD models, or even captures of the prototype are shown to further illustrate the modeled subsystem. The architecture was developed using MATLAB Simulink modelling platform, and is eventually going to be interactive, where the user is able to simulate in real time the effect of ambient temperatures and vibrations on mechanical components, the power flow between electrical subsystem, and all interfacing in between subsystems, all in order to obtain a transient representation on how the cube sat was designed to function. The captures below were taken from just a few levels in the system hierarchy.

System Level

System Level

Subsystem Level

Subsystem Level

Mechanical SS

Mechanical SS

Electrical SS

Electrical SS

Power Supply SSS

Power Supply SSS

The Simulink file is available here.

Code Update

The Majority of the code has been targeted at supporting the future testing for the project. This primarily involves the GPIO, Clock, and ADC settings and basic functions. The code is being stored primarily on the GIT repository which is publicly accessible for download. As certain stages in development are reached, code revisions are going to be posted in the EDGE repository as checkpoint for the code base.

Risk and Problem Tracking

The Risk Management document has been update through out this semster. This semester due to the issues with deployment, not getting the solar sail to deploy is our highest risk. Our updated design should help reduce the risk. Other risks

Since we faced some problems with the deployment we updated the problem tracking document which can also be seen below.

Deployment Problem Tracking

Deployment Problem Tracking

Schedule

The updated schedule for next phase is shown below, along with the projected schedule from the previous phase.
First Phase Schedule

First Phase Schedule

Projected Second Phase Schedule

Projected Second Phase Schedule

Budget

As of 2/22/2019, the project still has $428.73. Click HERE to download the full spreadsheet detailing all purchases so far.

Plans for next phase

For the next phase, in three weeks, we plan to have all the parts machined. The electronics will be assembled as well. This will allow for electrics and deployment testing.

Adam Stock

Brett Saxe

Jarrett Pischera

Kristin Angel

Nathan Lindberg


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