P16102: RIT-SPEX Structure
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

Based on the understanding of the project developed in the problem definition phase, this page details the process used to come to an overall systems design.

Functional Decomposition

Updated Functional Decomposition

Above is the functional decomposition of what is necessary for the deliverable of P16102 to actually do. Elements outlined in red were further developed through the morphological chart

The first type of major functions dealt with Constraining the Subsystems within the structure of the CubeSat. This really dealt with housing the internal circuitry and also stowing the solar panels during transit, integration and launch.

The second type of major functions dealt with increasing solar energy or increasing the area time effects. Of this, deploying the array was the most decomposed about the unfolding, extending and maintaining the structure, and following the sun was included at the first revision due to the original customer requirement.

Finally, the last set of requirements and functions identified were focused on meeting launch requirements. With this, P16102's deliverable would need to meet the cost needs, CSLI requirements and space environment requirements to be successful at the prototype stage.

This discussion started the process of reviewing engineering and customer requirements.

Updated ER (September 26th)

Updated ER (September 26th)


FD/ER Map

FD/ER Map

Concept Selection

Morphological Chart

Morph Chart (9/23/15)

Morph Chart (9/23/15)

Morph Chart PDF

Concept Down-select

During analysis, we identified that consistently the two driving choices were methods of pivot and methods of folding. From this, all other decisions made would be affected from that decision and nearly everything else identified on the pugh chart could be easily adapted. By choosing this from these two decisions outwards, we reduced the size of the trade-space very quickly and efficiently.

Down-selecting from 13 folding and 10 pivoting concepts to seven to prototype

Down-selecting from 13 folding and 10 pivoting concepts to seven to prototype

Due to the fact that may of the other functional requirements could be accomplished by interchangeable subsystems, the concept selection process for the overall system was focused primarily on the folding structure of the CubeSat. Many separate concepts were developed during the brainstorming phase, however the following seven were chosen for to move on to the pugh chart:

Name Image
Single Pivot 2x1 (click for animation) public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Single_Articulating_Gif.gif
Fan Fold (click for animation) public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Fan.gif
Cross 4X1+ public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Cross.jpg
Exploded 2x1 public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Exploded.JPG
2 Panels w/ Axel 2x2 (click for animation) public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Double_Articulating_Gif.gif
Single Stationary 2x1 public/Systems%20Level%20Design%20Documents/Concept%20Pictures/Stationary2by1.jpg
Snake public/Systems%20Level%20Design%20Documents/Concept%20Pictures/snake.jpg

These concepts were chosen because they span a wide variety of deployment possibilities, as well as a broad range of complexity.

Selection Criteria

To differentiate between each of the concepts, several metrics were chosen as selection criteria. These metrics were then weighted based largely on their relationships with key customer requirements using the house of quality.
Selection Criteria (9/23/15)

Selection Criteria (9/23/15)

Feasibility: Prototyping, Analysis, Simulation

Before evaluating each of the selected concepts, some basic engineering analysis was performed to ensure that each of the designs would be feasible.

Radiation Temperature

To this point, we have been operating under the assumption that the CubeSat will experience a temperature range from -40 to 40 degrees Celsius, based on knowledge of previous CubeSat experiences. Since our design will incorporate deployable solar panels, however, it will allow for more exposure to solar radiation relative to the area on the CubeSat that will radiate out heat. This may cause our CubeSat to absorb more heat than it can radiate and go above the predicted 40 degrees Celsius threshold. To determine if this is a real possibility, a theoretical model was created using reasonable material properties and a worst case scenario where the CubeSat reaches thermal equilibrium with the maximum area exposed to the sun. This analysis yielded the result that none of our design concepts would push the CubeSat temperature above 33 degrees Celsius, comfortably within the 40 degree limit. With this in mind, we do not have to limit our designs on the basis of radiative ability.

Temperature Range Feasibility (9/23/15)

Temperature Range Feasibility (9/23/15)

Area Time/Orbit Simulator

This tool simulates a vehicle placed in an orbit around the earth at a given altitude and determines some properties of the orbit, time for the solar panels to hit the sun and gather energy.
Tool Configuration

Tool Configuration

Measured in area time, it measures the rough area of sun CubeSat exposed to the sun at 10 degree increments from the mean anomaly measured at the velocity vector of the Earth. It isn't perfect, but provides a rough estimate of the area and the time that the solar cells are exposed to the sun which is directly proportional to the WeHr generated by the system. Additionally, with the prescribed orbit, it provides information about the energy generated over time and provides a useful graph. Below is a graph generated if two solar panels with a 180 rotation gathered energy at a constant rate.
Solar Incidence Plot of Graph

Solar Incidence Plot of Graph

Mass of Solar Panels

To determine the feasibility of each of the designs, the approximate weight of all of the solar panels must be known, so a remaining mass margin can be calculated for all of the support structure as well as any actuation mechanisms. Based on CubeSat specific solar panels already on the market, the typical mass of a single 10cm face solar panel is in the range of 29-50 grams. [1] [2]
Panel Mass Table

Panel Mass Table

Pugh Charts

Using these selection criteria, pugh charts were generated to chose the most beneficial concept design. Several of the concepts were chosen as a datum, and then compared to each of the remaining systems. Based on the weights assigned to each of the selection criteria, a weighted sum was used to choose the best design.
Exploded 2x1 as Datum (9/23/15)

Exploded 2x1 as Datum (9/23/15)

Weighted Pugh with Scaled Area and Exploded 2x1 as Datum (9/23/15)

Weighted Pugh with Scaled Area and Exploded 2x1 as Datum (9/23/15)

After careful consideration of each concept idea, as well as pugh chart analysis, two similar subsystems showed a strong set of advantages.

The exploded 2x1 and the single stationary systems both outperformed each of the other concepts. The selection criteria that made these solutions stand out were caused primarily by the simplicity of the systems, as well as their low volume and mass.

System Proposal

Selected Concept Deployments

Concept-Explode Deployment (9/23/15)

Concept-Explode Deployment (9/23/15)

Concept-Stationary Deployment (9/23/15)

Concept-Stationary Deployment (9/23/15)

These two final concepts are both characterized by two opposite panels deploying a single face, with three panels on stationary faces. The difference between the two designs is in the integration of the panel in the structure. In the "exploded" concept the deploying panels serve as structural support for the frame during launch, after launch, the two frame panels are separated and deployed. In the "stationary" design, the two deploying panels are attached to the outer faces of the frame, and they deploy while leaving the frame shape unchanged.

The final concept chosen does not include deployed panel articulation. While the articulating version of these systems were able to generate roughly 40% more power, the decision was made to stick with the simpler system in favor of increased reliability, as well as decreased mass and volume. These metrics all strongly affect the final value of the system and are likely more important to overall mission success.

Final System Functional Decomposition

Systems Integration and Functional Decomposition (September 26th)

Systems Integration and Functional Decomposition (September 26th)

Benchmarking

Investigation into possible alternatives to custom design yielded one main manufacturer capable of achieving the customer's objectives. Clyde-Space is a supplier of small and micro spacecraft systems, and is the world's leading CubeSat vendor. [3] Currently Clyde-Space offers both a 1u CubeSat skeleton structure, and also a 1u CubeSat deployable solar array. They are currently priced at $925 for the structure and $5,650 for the deployable array (two full faces). This is out of the customers budget therefore a custom design must be made. Below is both the cubesat structure and deployable panel offered by Clyde-Space. Example of Clyde Space Deployment [4] [5]
Clyde-Space Skeleton Structure (9/23/15)

Clyde-Space Skeleton Structure (9/23/15)

 Example of the 1u Deployed Clyde-Space Solar Array (9/23/15)

Example of the 1u Deployed Clyde-Space Solar Array (9/23/15)

Clyde-Space does not currently offer articulation in a 1u deployable solar array. Researching for possible solutions in academia yielded nothing. Articulation is not currently or has not been done for a 1u CubeSat. CalPoly has constructed a 3u articulating solar array.

[6]

Research Articles

Cajun Advanced Picosatellite Experiment

Below is an example of deployment from a 1u CubeSat. It shows the structure as rigid which is required for inside the PPOD but after launch it is not required to be rigid. CAPE2 claims to be the first 1U CubeSat to use deployable solar panels. They custom built the spring hinge and used fishing line running through a resistance coil to deploy the panels. [7]
 CAPE2, a Cajun Picosatellite Experiment (9/23/15)

CAPE2, a Cajun Picosatellite Experiment (9/23/15)

Xatcobeo Spanish CubeSat

A solar array deployment system was designed and simulated by the Xatcobeo project team. The team confounded of students from the University of Vigo and the INTA (Spain National Institute for Aerospace Technology). The solar array deployment was designed and simulated but not built. In the research article it was concluded that more than one panel that unfolds will induce to much mass not allowing for symmetric deployment. However for there simulation they used this double fold to show the strength properties of the spring and deployment mechanism. In the figure below the deployment mechanism is portrayed. [8]
 Xatcobeo Deployment Mechanism (9/25/15)

Xatcobeo Deployment Mechanism (9/25/15)

Planning

Functional Test Planning

To evaluate the success of our design, several tests will be performed both on the physical structure and on computer aided design models to ensure overall system performance.

Advocate Structure

Due to the small size of our group, we will often find ourselves in situations where one person will have to work on multiple areas of the project in order to meet the deliverables of a certain phase. Because of this, no one on the team will rigidly specialize in one area of the project. That being said, we still feel it is important for each section of the project to have someone looking out for it specifically and making sure it progresses as needed. To make sure all parts of the project are “owned” without sacrificing the flexibility our small size mandates, we have developed an advocacy structure. In this structure, each group member is assigned to be an advocate of a portion of the design. The advocate is responsible for making sure the needs of their portion are taken into account but may still work on other portions and receive help on their portion from other members. The team advocacy breakdown is as follows:

Phase III Deliverables

  1. Review SDR Action Items, Update Requirements, and Identify Subsystem Resources
    1. Begin Subsystem Design Layout
      1. Identify All Critical to Performance Interfaces
      2. Analyze Possible Alternative Designs
    2. Begin to Develop a CAD Package with Guides
      1. Follow Labeling Scheme from the Nomenclature Page
    3. Relate All Subsystem Component Specs to Parent Requirements.
  2. Proof of Concept
    1. Analysis and Simulation
      1. Deployment - Simulation
      2. Vibration - Analysis and Simulation
      3. Inertial Concept - Analysis
      4. Thermal Environment - Simulation
    2. Possibly Create a Full Launch Cycle Simulation - Thermal, and Mechanical Stress Simulation
 Project Package Structure

Project Package Structure

Risk Assessment

Risk Outlines

Risk Outlines

The risk assessment was updated based on the determination laid out in concept selection. Specifically the articulation of the solar array.

MSD 1 Deliverable Planning

Project Plan

Project Plan

MSD II Goals

By the end of MSD II, we will have produced a CubeSat structure with at lease one deployable solar panel integrated into the CubeSat, two if possible. The array(s) will have locking and deployment mechanisms. The deployment mechanism will have been tested to demonstrate deployment reliability. The entire structure will have undergone thoroughly documented vibration testing in conjunction with P16103. The CubeSat design will be completely documented with finalized CAD models and a B.O.M. Our plan for the remainder of MSD I supports our ability to complete these deliverables during MSD II.

(individual 3-week plan template for this).

References

  1. Clyde-Space Solar Panel Example, Web, 2015
  2. ISIS Solar Panel Example, Web, 2015
  3. Clyde-Space description, Web, tictoc, 2015
  4. Clyde-Space CubeSat Shop where components can be purchased, Web, tictoc, 2015
  5. Clyde Space Example, Web, tictoc, 2015
  6. Presentation on the constructed articulating array, Web, CalPoly.edu, 2013
  7. Mechanical Design of CAPE2 - the Second CubeSat being designed under the Cajun Advanced Picosatellite Experiment, Web, researchgate.org, By: A. Bajpayee, 2015
  8. Xatcobeo: Small Mechanisms for CubeSat Satellites - Antenna and Solar Array Deployment , Web, researchgate.org, By: J. Plaza, J. Vilan, F. Agelet, J. Mancheno, M. Estevez, C. Fernandez, F. Ares, 2010

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