Table of Contents
Team Vision for Detailed Design Phase
What did your team plan to do during this phase?
- Finish the mechanical design
- Finalize the electrical design
- Order parts next semester
- Make test plans
What did your team actually accomplish during this phase?Our team successfully met all milestones. See the document below for a finalized revised MSDI schedule detailing all tasking and milestones met.
Drawings, Schematics, Flow Charts, Simulations
Selected Electrical Components
- Power will be stored at 3.3-4.2
- Panasonic NCR18650B 3400 mAh battery
- For simplicity of design, many compnents have been
sourced as modules.
- These components are also easily sourced individually, so the design could easily be implemented on a single PCB.
- A carrier PCB has been designed to carry these breakout board.
- The power/driver board will be pin compatible with the selected microcontroller.
- Battery charger is the SparkFun Adjustable LiPo
Charger based on MCP73831
- 12V - Pololu U3V12F12 Step up Voltage Regulator
- Boost converters to get the desired 5V and 12V lines
- 5V - Pololu U3V12F5 Step up Voltage Regulator
- 12V - Pololu U3V12F12 Step up Voltage Regulator
- Power multiplexer to select battery or solar
- Pololu breakout for TPS2113A Texas Instruments Power Multiplexer
Below is the schematic diagram for connections to be made between the listed breakout boards, as well as motor drivers.
The efficiency of the 5V boost converter at 3.3V input from the battery will be approximately 87% with a current draw of 100-200 mA. This current draw would represent the 5V line at its approximate maximum draw.
The 12V line will be used exclusively for driving the deployment motor. The use of this line will be very sparse and will only occur with a fully charger lithium ion battery, which will have a voltage of approximately 4.2 volts. Extrapolating the efficiency data below for a 4.2 volt input, the converter will have an efficiency of approximately 80% at a maximum current draw of 350 mA, which will be sufficient to drive the deployment motor. This efficiency should be considered an acceptable loss, due to the short duration of the deployment of the sail as compared to the length of the mission.
Final Mechanical Design
Sail DeploymentThe below images show the boom system, made of tape measures, that will deploy the solar sail. The yellow part shows the approximate size of the full booms spooled on the center holder. From there, the center holder will rotate to push the booms outwards. The second picture shows the plate that is in place to protect the geartrain from potential sagging of the booms as they unfurl. The third picture is the worm gear drive that replaced the geneva cam that was put in place by the previous team that had worked on this.
Spring Hinge Assembly
Solar Panel Hinge Test
Solar Panel Deployment
Bill of Material (BOM)The updated Bill of Materials can be seen below. All parts on the BOM have been ordered and will be ready for test and assembly next semester.
Mass and Center of Gravity
According to cubesat regulations the maximum mass of a 3U cubesat is 4.0kg. According to cubesat regulations the center of gravity must be within 2cm of the geometric center in the x and y direction and within 7cm in the z direction.
First the mass and the center of gravity will be found in simulation. In the CAD model we have, material properties will need to be applied, then Solidworks will be able to give us the total mass and the center of gravity.
After the cubesat is built we will weigh the cubesat to find the mass. We will also test the center of gravity. To test it we can use a table edge method. This method involves placing the cubesat flat on a table. It is then pushed slowly over the edge in its x,y,or z direction until the cubesat starts to tilt at which point we will make a mark on it. We will repeat this for the x, y, and z direction of the cubesat. Where the 3 tipping points meet is the center of gravity. While doing this we will be careful to not drop the cubesat off the edge of the table.
VibrationsWe will complete vibrations testing to simulate launch conditions. Testing recommended by NASA include random vibrations on each 3 axis and sinusoidal testing on each 3 axis.
We talked to the packaging science department to use their vibrations table but they can only produce up to 300Hz when we need over 1000Hz. Dr. Ghoneim in the Mechanical Engineering Department also has a vibrations table and it can produce larger frequencies in the range we require. We plan to test at 1000Hz.
In order to test run conditions in a cold environment, we plan on conducting a thermal test using dry ice. Low earth orbit's temperature varies depends on if you measure the temperature in the sun or in the shade. The average temperature is about 10 degrees Celsius but it can get down to minus 100 degrees Celsius in the shade.
We will put the mostly assembled cubesat in a bin and then pack it with dry ice which reaches -78.5 degrees Celsius. We will then run the electrical components to test if they will work in the extreme temperatures.
It is also a requirement to test it at high temperatures. We will put the cubesat in the oven at 70 degrees Celsius to test high temperatures.
Nichrome Wire Testing
We plan to use Nichrome wire to cut fishing line to release the solar panel flaps. This idea came from a previous senior design team that was creating a cubesat that deployed its solar panels using the same method and can be seen here. They verified that this method will work but we will do some simple tests to confirm it works and see how long it takes to cut the fishing line.
We will also also check to see if it will cut multiple fishing lines stands at once and the time that would take. Multiple fishing lines in tandem would be stronger than one stand of fishing line so if the nichrome can still cut the fishing line in a reasonable time we would probably use multiple lines.
Risk AssessmentAn updated risk assessment can be seen below
Here is a link to the live document.
Design Review MaterialsPlease select the link below for the detailed design review agenda.
Plans for next phaseSee the document below for our preliminary projected MSDII schedule.
- Test Spring Model Hinge Assembly
- Detail Drawings
- Machine Parts
- Test New Deployment Geartrain
- Assemble CubeSat
- Conduct Mass Test
- Conduct Vibrations test
- Conduct Thermal test
- Help Assemble cubesat
- Keep Edge Updated
- Manage the Risks
- Prototype Complete Power System
- Finalize PCB Design
- Integrate Microcontroller Board Into Power Design
- Integrate Connectors for all Desired Sensors
- Compile Red-lined System Architecture
- Test and Design Documentation
- Operations Guide
- Solar Panel Documentation
- Create Configuration Base for Micro Controller
- Create Pin Mapping for All Peripheral Sensors and Power Systems
- Create Design Support Page with low Level System Details
- Create Main Control Loop
- Develop/Integrate BSP (Board Support Package)