Customer Handoff & Final Project Documentation
Team Vision for Final Demo and Handoff
- We created the team poster
- We wrote the research paper
- We tested deployment with the sails on
- Other final tests were completed
Test Results Summary
All the test documentation can be found here.
Sail DeploymentWe preformed a full sail deployment with the sail attached. The video can be found here. The sail only deployed to about 75% by itself, so it was decided that the top deployment cage had to be redesigned to guide the booms out of the cubesat. This will reduce the risk of the booms unfurling too far inside the cubesat and not being able to overcome friction. The cage has been manufactured and put in place but has not been tested as of the final day to update this page.
In order to get the sail to deploy the last 25% of the way by itself, the deployent cover was redesigned to hold the booms in tighter to the spool.
However, we ran out of time to test this new part. The arm that was previously mentioned to hold the booms in closer is highlighted in green. Just from initial small movement tests, the red circled area might need rework. Without the hole sensors in place, the booms have room to up and outwards, which could cause problems down the line.
Initially the cubesat simulation's weight was found to be 3.045kg. The built cubesat was weighted and found to be 2.533kg. The two masses could be different due to the materials that were applied to the CAD model and the weight of the sails. The cubesat regulation is 4.00kg for 3U cubesats, so our device is well within the regulations, with room for future additional systems to be implemented by future teams.
Center of Gravity
The center of gravity of the the cubesat must be within cubesat regulations. The center of gravity must be within 70mm of the center point of the cubesat in the Y direction and within 20mm of the center point of the of the cubesat in the X and Z direction.
The simulated center of gravity data can be seen in the picture below.
The summarized test results can be seen in the table below. The measurements are taken from the center point of the cubesat. The simulated results did not include the weight of the solar sails which would shift the Y direction center of gravity further upwards towards the measured center of mass.
This design meets cubesats regulations for the center of gravity and has the center of mass shifted upwards, which allows for more weight to be added in the lower half for attitude control and communications.
Flight TestIn order to get an idea of how the cubesat will do in space, we decided to do a preliminary flight test.
ElectronicsThe electrical subsystems that were completed this year were:
- MSP430 Baseboard which incorporates battery charging,
power regulation, kill switches, and a programming
- The first revision of this board has been assembled and handed off.
- A second revision of this board was designed and ordered, however there was no time remaining to assemble these. All parts required are being handed off for the next team to assemble.
- Daughterboard to breakout motor driver, nichrome wire, and plugs for each of the sensors. This board also has a prototype area, available for any small additions.
Note on programming the custom baseboard: Only four lines must be connected in order to program the board. Using the MSP430FR5969 development kit, disconnect the jumpers from the EZ-fet emulator, and connect the TST, RST, VCC and GND to the custom baseboard. Provide a pullup resistor and a capicator to ground on the RST pin.
Future work should include:
- Communication system
- Attitude control system
Each of these systems should most likely require another daughterboard to be designed for each one. Future daughterboards can be designed in Eagle PCB, following the specification described in the Integrated Build & Test. Eagle libraries for the components used can be found in the detailed design on the SVN.
The software for the cubesat is designed as a skeleton which easily allows the addition of new commands and systems in the future. The code was updated recently to add a few additional items before hand-off.
- Sensor ports were updated to be standard GPIO instead of Analogue inputs. This allows for faster and easier sensing of the sensors which are used to check the status of the sail deployment.
- Ground control software was condensed to simplify some of the functionality. Much of the common functionality was also split into separate method calls, to reduce the amount of code which has to be written when a new command is added.
- Timer Module - The timer type A had some low level drivers written for it. These drivers should be used in tandem with the sensors to determine the status of the booms during sail deployment. The timer should also be used as a safety check during essentially all communications within the system to avoid getting stuck waiting at any point in the system.
- WatchDog Timer - A system timer which is used to ensure that any chip level command does not take too long to process. It is possible to use this timer to ensure that long processes such as any attitude control mathematics do not go over a specific amount of time (likely the maximum time before the system requires new movement inputs from the attitude system). Potentially the chip can be reset after storing a count or flag in the FRAM which indicates such a fault has occurred. This allows the determination of how many faults have occurred, and may lead to additional steps to solve any related issues.
Solar Panel SelectionTo recap, the decision was made to not source solar arrays for the CubeSat during this phase of the project. This was due to a lack of funding, or more specifically a lack of time to source proper funding, as well as a few technical uncertainties. To mitigate this decision, an alternative selection study was undertaken to provide the teams of future project phases general knowledge of space grade solar cells, and a specific model recommended for them to source.
Essentially the study elaborates on the fundamental nature of photodiodes, the discrete electrical components that comprise the solar cells many are familiar with. It then delves into the technology of the solar cell itself, and the composition of these cells into arrays appropriate for integration into 3U cubesats, tailored specifically to the team’s current design. The qualitative portion of the study also highlights the critical features of space grade solar cells that differentiate them from traditional terrestrial cells. This includes temperature resistance, radiation resistance, and triple junction technology.
For the analytical alternative selection portion of the study, Boeing’s Spectrolab XTJ Prime cells, and GOMspace’s P110 customizable arrays were rated as the recommended alternatives. Since most of the data was quantifiable, the data points were rated on a scale of 1 to 10, relative to each other data point in the same criteria. For example if the radiation degradation for one alternative was the average across all the alternatives, it would be rated a 5. The weightings were applied to each rating, simply by amplifying it by the average weighting, and then every rating for each alternative was summed to produce an overall rating. The overall rating was the effective metric by which the optimal choice was determined. The complete study can be found here.
The raw data (blue field), individual ratings (green field), and overall ratings (red field) are found in the charts in the interactive spreadsheet found here. The effective criteria weightings can also be found here as well. This spreadsheet served as the back end database for the entire study. If the study is adapted in the future to include additional alternatives outside the current scope, weightings and ratings can be altered, updating the entire spreadsheet. However the ratings are not tied directly to the raw data, the ratings have to processed manually due to restrictions. A comprehensive view of the weightings are also found in the spreadsheet.
Spectrolab is a reputable Boeing company well known in the Aerospace industry. Their solar cell assembly overall rating exceeded all others by roughly 20%.
GOMspace hosts an extremely wide variety of well-tested proven OTS CubeSat components from communication modules to entire chassis. Three of their P110s customized into an array won out as well by roughly 20%.
Risk and Problem Tracking
The Risk Management document has been update through out this semester. This semester due to the issues with deployment, not getting the solar sail to deploy is our highest risk. From the last design review the risk is smaller since we got the deployment working but something could still go wrong. Our updated design should help reduce the risk. Other risks
- Not being able to fold the sail small enough
- Solar panels don't deploy
- Nichrome wire doesn't cut the fishing line
There were no new problems this final handoff but here is the finalized problem tracking document which can also be seen below.
Final Project Documentation
- Our final technical paper can be seen here.
- Our poster for Imagine RIT can be seen here.
- Our final design documents can be found here.
- Final BOM can be found here.
Final BudgetWe started the year with a $1000 budget, and $250 remains as of this hand off. Details can be found in the chart below.
Recommendations for future work
- Modify parts to accommodate kill switches (CAD complete already)
- Communications System
- Attitude Control System
- Larger Sails
- Optimize Sail Folding Method
- Sourcing of Solar Panels
Functional Demo Materials
- The lightning talk video
- Imagine Poster