Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
What did your team plan to do during this phase?
- Start ordering parts
- Design a power conditioner
- Communicate with the team from Dubai
- Design Mechanical systems
What did your team actually accomplish during this phase?
- Test the strength of the tape measure
- Design flap deployment
- Design power system
- Update Risk Assessment
Prototyping, Engineering Analysis, Simulation
Our plan was to test the torque needed to turn the Geneva cam to have the booms deploy but the Geneva cam kept locking up and we couldn't get any usable data. Not being able to get it to work added with the fact that it reduces torque instead of increasing it like the worm gear, led us to the decision to choose to use a worm gear instead of the Geneva cam.
Working with the Dev KitThe CubeSat Development Kit from Pumpkin Space Systems, is a proprietary PCB design, which allows a collection of different processor models to be used with a signal modular motherboard. The processor version which was with the model we worked on was an MSP430F2618. This processor is a radiation hardened model with 116kB of FRAM and 8 kB of SRAM. While this processor is a high end model for a embedded processor, the turn away from this system is related to the Firmware of the motherboard. The Cubsatkit website notes that the kit only one development environment may be used when programming the MSP430 version of the kit. This software is known as CrossWorks for MSP430. However, the version of this software which is noted as running the kit is 1.4 while the most recent release is 3.1, indicating that there is likely a lack of support for more modern versions. In a similar vein, firmware drivers needed to connect to the motherboard is only compatible with older versions of windows (7 and older) meaning that unless a windows 7 system is immediately available, development is much more difficult. In the end, although the capabilities of the kit are enticing, the lack of easily accessible modern system support makes it a less than ideal candidate at this time.
Test Strength of Tape Measure with holes
We tested some tape measures to determine the loss of strength that might occur when putting holes along the length of them. This was done to determine the feasibility of adding holes along the booms as a method for tracking the deployment of the sail. We tested them using a hanging mass set. The masses were put in a hole at the end of a tape measures and the tape measures were slid slowly off the end of a table until the tape measures bent under the weight. The data collected can be seen in the table below. We concluded that the maximum distance in which the tape measures could support themselves didn't change much when holes were added, so putting holes in them should be fine.
Team Discussion and Design
How to deploy solar panels flap
We looked into several ideas on how to deploy the flaps the solar panels are on as can be seen below
- Clock Spring
- Centripetal Force
- Temperature activated material
- Linear Actuators
- Motor and String
Looking at the ideas there were some ideas we could eliminate so of the ideas right off the bat. The temperature reliant system would not be feasible because we don't know how long it will be in space before it needs to deploy. Also its orientation to the sun will effect the temperature on either side of the cubesat. We also could rule out straight springs since there is a maximum spring force amount allowed in cubesats. We ended up choosing the motor and string. For this idea a motor would sit on the one end of the cubesat. When activated the motor will turn and pull on four strings that will pull up the four sides of the cubesat that hold the solar panels. We picked this idea since we can control the speed and it will be easier to implement than some of the other ideas such as the clock spring idea. Also if the idea requires more torque it would be easy to just add a worm gear or another gear arrangement.
Meeting with Dubai TeamWe meet with the Dubai team over video chat and talked about our projects and if there was any way to combine them. We were told they required 2U. We need 3U worth of equipment but i could be possible to combine the power system and micro controller cutting out 1U. This still leaves us a minimum size of 4U. Switching to a 6U now would require us to develop a whole new design.We decided to work on our own indiviual projects for now and maybe in the future they could be combined. A link to the meeting notes can be found here.
Seminar on Remote Sensing ISRO ApplicationsPer the advice of our SME Dr. Kurinec, we attended a lecture by Dr. Kumar, former head of the Indian Space Research Organization (ISRO), on remote sensing applications for developing countries such as India, with emphasis placed on the role on nano-satellites for these applications. The event helped increase project visibility and provide information on missions other countries and universities are undertaking for their nano-satellites.
Grant ApplicationDue to having low fund we decided to apply to the New York Space Grant Consortium. We filled out the form and attached our bill of materials below.
Drawings, Schematics, Flow Charts, Simulations
Power SystemThe power system PCB will consist of several functional blocks:
- Power Generation
- Provided externally 12 Vdc
- Power Conditioning
- Noise suppression on incoming power
- 12V regulation of incoming power
- Charge Controller
- Power Switch (To switch between battery and solar)
- 9V regulation for motors and solenoids
- 5V regulation for logic level systems
- Power Storage
- 3 Cell lithium ion battery pack at 10.8V
- Motor driver circuits
- H-Bridge driver
- Back EMF suppression
- Solenoid driver circuits
- Solenoid driver
- Back EMF suppression
Power SourcingWith Cooperation with SME Prof. Kurinec, the following PV panel assembly shown in the spec sheet has been identified with the following characteristics: -Light-weight -Tin -Shatter resistant -Durable -high-efficiency -GaAs cell -Radical Temperature Resistant -Rad-Hard -PCB Backing Provided
The following is also captured from a NASA study on nano-satellites encompassing the OTS sources of PV cells and assemblies, along with a sampling of respective efficiencies.https://sst-soa.arc.nasa.gov/03-power.
Bill of Material (BOM)
The up to date document can be found here.
High Altitude Balloon
- Probably not necessary, looking to replace with temperature chamber testing for cold temperature testing as well as vacuum chamber testing.
- Moving away from this will allow the tests to occur under conditions which can be monitored and controlled more closely.
- As electrical systems are constructed, must test under low temperature conditions to ensure they are operational in the temperatures of low earth orbit.
- Mechanical systems should be tested to ensure tolerances are such that the system is operational at low temperatures.
Prototype Battery Recharging
- Regulators and a battery charger IC have been selected and samples have been acquired.
- A prototype of some components of the electrical
system will be constructed and tested for the proper
functionality before the schematic is finalized and the
PCBs are ordered.
- Power regulation at all desired voltages
- Battery charging circuit to ensure it is capable of safely charging the Li-ion battery pack
- We plan to do vibrations testing with Dr. Ghoneim, as close to the required vibrations test for launch to ensure that the folding solar panel sides are rigid enough for flight.
Design and Flowcharts
The up to date document can be found here
The following is a more detailed plan of the development life cycle during MSDII.
Risk AssessmentWe updated our risk assessment which can be seen below. Most of the risks are the same the only main difference was the likelihood of the risks. We lowered several likelihoods such as sail getting tangled and not enough torque. Our redesign makes us more confident that we can accomplish these tasks. Our most important risk right now is "Can't get a big enough sail to really generate propulsion." We did decrease the likelihood of this since we are confident we can make a bigger sail than last years group did but it didn't decrease by much and this has very sever consequences.
A link to our current up to date document can be seen here.
Design Review MaterialsInclude links to:
- Notes from review
Plans for next phaseFor the next phase, in three weeks, we plan to finalize our design. All the mechanical and electrical systems will be completely designed. We will also continue to update the Bill of Materials.
- Finish CAD Model
- Detail Drawings to be Manufactured
- Start Machining Parts
- Keep Edge Updated
- Update Risk Assessment
- Update Test Plans
- Prototype power system including battery charging
- Schematic diagram of power system with motor and solenoid drivers
- PCB design compatible with the selected microprocessor
- Red-Lined Design Documentation Integration into Systems Architecture
- Solar Panel Sourcing Technical Analysis
- System Modelling
- Test Documentation Support
- Determine Initial Processor Configuration
- Create Pinout Mapping for Processor
- Integrate Processor with Power Board
- Start Developing Programmatic Flow Design