P16102: RIT-SPEX Structure
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Problem Definition

Table of Contents

Project Definition

RIT’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.

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Project Goals and Key Deliverables

Through the course of this project, we will:

Stakeholders

  1. RIT Space Exploration Research Group - Scientists
    • Dr. Dorin Patru
    • Power Segment of Satellite Development Segment
    • RIT SPEX
  2. Launch Services Provider
    • Typically a private company with their own set of standards
    • Integrates and launches the final vehicle
  3. Launch Provider
    • Responsible Governmental Agency
    • Provides the commands, orbital elements and flight path

Project Summary

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Use Cases

Typically, we found three types of users:

General Use Scenario

This use case scenario will deal with a relatively simple deployment from a PPOD hosted on the avionics ring of a launch vehicle.
Traditional Use Case

Traditional Use Case

High Tumble Use Scenario

In 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.
High Tumble Use Case

High Tumble Use Case

Note of Use Cases

In 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 Chart

This 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.
BAT Chart

BAT Chart

Customer Requirements (Needs)

Customer Requirements (Sep 10, 2015)

Customer Requirements (Sep 10, 2015)

Customer Interviews

Date Subject Interview Questions Notes Audio
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)

First Draft of Engineering Requirements (Sep 9, 2015)

First Draft of Engineering Requirements (Sep 9, 2015)

Updated ER (October 29th)

Updated ER (October 29th)

House of Quality

House of Quality (September 10th, 2015)

House of Quality (September 10th, 2015)

Updated House of Quality (October 29th, 2015)

Updated House of Quality (October 29th, 2015)

Benchmarking

Engineering Requirement Benchmark Benchmarker
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
ER5-Inertia Change
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

Constraints

Customer Constraints

Flight Ready Constraints

Flight ready constraints per CubeSat Launch Initiative. Reference-NASA document LSP-REQ-317.01 Revision B:

Strength Qualification Requirements. Ref:LSP-REQ-317.01 (Sep 2, 2015)

Strength Qualification Requirements. Ref:LSP-REQ-317.01 (Sep 2, 2015)

Concerns and Risks

The risk assessment can be found here.

Risk Outlines

Risk Outlines

Plans for next phase

The next phase focuses on a few major items:

Phase II Project Plan

Phase II Project Plan


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