Project DefinitionRIT’s new Space Exploration (SPEX) group was created last year with the goal of bringing RIT into the field of CubeSat construction and experimentation. CubeSats are small vehicles used by industry, government, and universities to enable small scale experimentation with space systems. Electrical power for these systems is generally provided by solar panels and are restricted by the surface area of the vehicle. CubeSat deployable solar arrays are available for purchase, however they are too expensive to be of use to RIT SPEX.
The objective of this project is to create a first generation, deployable solar array for use in 1U sized CubeSats for RIT SPEX to support future development. The system must be capable of integrating with a general CubeSat bus while supplying the necessary power to CubeSat subsystems for both the pre-deployed start-up phase and mission phase. It must also be capable of reliably deploying after enduring the launch conditions described in the CubeSat Launch Initiative and P-POD User’s Guides. Lastly the system should be inexpensive to manufacture in comparison to similar systems.
Project Goals and Key DeliverablesThrough the course of this project, we will:
- Create a lightweight CubeSat frame
- Build a deployable structure to increase photovoltaic cell surface area
- Minimize cost for RIT SPEX
- Provide documentation so RIT SPEX can understand, modify, and reproduce the design
- RIT Space Exploration Research Group -
- Dr. Dorin Patru
- Power Segment of Satellite Development Segment
- RIT SPEX
Launch Services Provider
- Typically a private company with their own set of standards
- Integrates and launches the final vehicle
- Responsible Governmental Agency
- Provides the commands, orbital elements and flight path
Use CasesTypically, we found three types of users:
- Scientists who perform experiments and manage the satellite
- Launch Providers who build and integrate the vehicle and rocket
- Services Providers who launch the rocket and send commands
General Use ScenarioThis use case scenario will deal with a relatively simple deployment from a PPOD hosted on the avionics ring of a launch vehicle.
High Tumble Use ScenarioIn some instances, CubeSats deployed from a PPOD might have a high rate of tumble, in which it would be optimal for a vehicle to detumble and then deploy, a process that could take multiple orbits to complete. In this case, the vehicle has to both detumble and charge before deployment. Extended the solar cells during a high tumble situation could case vibration problems, high torque or add to the already chaotic motion of the vehicle.
Note of Use CasesIn both of the above examples, they only focus on deployment from the launch vehicle, which is a very typical example. However, other launches can occur from the ISS, where the PPODs are taken to the ISS by a commercial resupply vehicle and launched on the end of a robotic arm. This use case would only differ from the ones above slightly where the PPODS are deployed by astronauts rather than the launch provider.
BAT ChartThis is an overview of the scenario/steps that a typical CubeSat will go through to enter low earth orbit (LEO). Depending on the launch vehicle the deployment steps may vary, along with the vibrating acoustic loads during launch.
Customer Requirements (Needs)
|8/27/15||Dr. Patru||8-27-15 Interview Questions||8-27-15 Interview Notes||1 2 3 4 5 6 7 8 9 10|
|09/03/2015||Dr. Patru||N/A||9-03-15 Interview Notes||N/A|
Engineering Requirements (Metrics & Specifications)
House of Quality
|ER1-Undeployed PV Area||100 cm^2||CubeSat Standard/Customer|
|ER2-Deployed PV Area||101 cm^2||Customer|
|ER3-Survives Thermal Cycling||Pass/fail||CubeSat Standard|
|ER4-System Mass||200-300 gram||Customer Requirement/ClydeSpace|
|ER6-PPOD-CubeSat Clearance||1 mm||CubeSat Standard|
|ER7-Time from Command to Deploy||2-8 Seconds||Clydespace, Various Research Documents|
|ER8-Operating Temperature||25-35 DegC||Customer Requirement|
|ER9-Volume Fraction of Structure||0.3 - 0.5||ClydeSpace, Customer Requirement|
|ER10-Solar Angle Domain||180-360 deg||Academic Research|
|ER11-Deployed Vibration Amplitude||Power Spectrum Pass/Fail||CubeSat Standard|
|ER12-Deployed Vibration Frequency||Power Spectrum Pass/Fail||CubeSat Standard|
|ER13-Change in COM||10-50 mm||Customer Requirement|
|ER14-Cost||$100-$500||Customer Requirement/ClydeSpace ($5,000-$13,000)|
|ER15-Time to Remove PCB Blank||10-60 seconds||Customer Requirement|
|ER16-Undeployed Vibration Amplitude||Power Spectrum Pass/Fail||CubeSat Standard|
|ER17-Undeployed Vibration Frequency||Power Spectrum Pass/Fail||CubeSat Standard|
|ER18-Survivable Angular Acceleration||10 deg/s/day||Notional CubeSatPro ADCS Package|
|ER19-Survivable Angular Rotation||2 deg/s||Notional CubeSatPro ADCS Package|
|ER20-Analog PVV Material Density||2.33||ClydeSpace|
|ER21-Full Documentation of Package||ClydeSpace/Customer Requirement|
Lessons Learned-From all of this benchmarking, we've discovered that there are a variety of ways to test these engineering requirements and many of them are very broad in terms of success or passing and failing. We will need to develop and study multiple techniques that we've identified to be able to assess these properties of the final system.
Critical Design Challenges
- Compact system capable of deploying and articulating solar panels
- Enough solar panel area to power the mission and must be facilitated both deployed and undeployed
- Ensuring nearly 100% reliability after launch
- Structure must allow for installation of subsystem PCBs
- Minimizing the volume occupied by the undeployed solar array.
- System must be low cost to reproduce
- System must have an overall mass under 300g
- System must have an external volume that fits in a 10cmx10cmx11cm space
- System will employ solar panels as only system for energy generation
- Flight ready prototype by completion of MSD II
- Lifespan must be sufficient to complete all possible mission componenets
- Must comply with constraints from the CubeSat Launch Initiative including compatibility of constraints from 3 of the most common Launch vehicles.
Flight Ready Constraints
Flight ready constraints per CubeSat Launch Initiative. Reference-NASA document LSP-REQ-317.01 Revision B:
- CubeSats shall be no smaller than a 1U (10x10x10cm) form factor.
- CubeSats shall not contain pressurized vessels.
- CubeSat containing nonventable pressure containers are permitted if the satisfy the following requirements: Pressure shall be no more than 1 atmosphere while on Orbit, Pressure container contents shall be not endanger personnel or equipment or create a mishap (accident) if released, Pressure containers shall be structurally qualified in accordance with Table 2 - Strength Qualification Requirements.
- CubeSat shall not contain propulsion systems.
- CubeSats shall not contain radioactive material.
- CubeSats shall not contain any explosive devices.
- CubeSats hazardous material shall conform to AFSPCMAN 91-710, Range Safety User Requirements Manual Volume 3 – Launch Vehicles, Payloads, and Ground Support Systems Requirements.
- CubeSats shall remain powered off from the time of delivery to LV through on orbit deployment.
- CubeSats shall be self-contained, and provide their own power, sequencing, and wiring. CubeSats shall be designed to accommodate ascent venting per Ventable Volume/Area < 2000 inches in accordance with accepted standards such as JPL D-26086, Revision D, Environmental Requirements Document (ERD).
Concerns and Risks
- Budget for creating the system will be very low
- System will undergo heavy vibration at launch. Causing possible damage to the structure and contents insides
- EM Radiation in addition to cosmic winds will cause the solar areas and the CubeSat to heat up which may damage internal components as well as the deployed solar cells
- Deploying and articulating panels will alter the flight dynamics of the CubeSat in potentially dangerous way
- CubeSat is limited in its ability to collect power before the solar arrays are deployed
- Problems in the P-POD due to flaws in our CubeSat, other CubeSats in the same P-POD, or the P-POD itself may prevent our CubeSat from being released into orbit.
- One or more solar arrays may fail to deploy in orbit, severely limiting power supply
- One or more solar arrays may fail to articulate in orbit, making optimization of solar arrays orientation to the sun difficult to impossible
- Conditions in orbit could cause solar panels to become unglued to the structure if all conditions are not properly accounted for
- CubeSat could be impacted by a meteor (micro or otherwise)
- CubeSat will be subject to violent conditions during detumble
The risk assessment can be found here.
Plans for next phase
The next phase focuses on a few major items:
- Concept Development
- Exploring the field and figuring out what we could emulate or what we could develop-Ownership:All
- Tool Development and Industry/Research Benchmarking
- Developing rough analysis tools to predict the usability of the concepts and compare to benchmarks-Ownership: Two Staff
- Identifying community Figures of Merit(FOM) and Benchmarks-Ownership: Two Staff
- Down-selecting to a few concepts
- Selecting 4-6 concepts to further develop based on FOM-Ownership:All
- Analyzing the few concepts-Ownership:All
- Down-selecting to one or two concepts -Ownership:All
- Beginning prototyping-Ownership:All