Team Vision for Systems Level Design PhaseDuring the Systems Level Design phase, our team’s goal was narrow down the scope of the project, functionally decompose the aspects of the crew-lock, generate, critique, and select a concept for the crew-lock. Parallel to these goals, the Problem Statement, Engineering and Customer Requirements, Risk Assessment, and Master Schedule have been changed or updated. In order to accomplish these tasks, the team began by reading through 10+ NASA and Department of Defense technical papers (2000+ pages of material) on previously designed rigid and deployable crew-locks and air-locks. Using this information, a Detailed Benchmark Table was created in order to refine the Customer and Engineering Requirements, and to guide both the team and the customer on how the project should proceed. Next, using two functional decomposition techniques, Function Decomposition Tree and Transformation Diagram, a Morphological Table was developed using team-generated solutions to sub-functions the crew-lock should be able to perform. After this step, feasibility analysis were done to find out whether certain aspects of the project and the project deliverables would be possible for the team to accomplish. Using the Morphological Table and the feasibility analysis, concepts were generated and populated onto a Pugh Chart for concept critiquing, and down-selection. Once the concept was selected, a preliminary Functional Test Plan was developed.
Functional DecompositionBelow are two methods of functional decomposition for the deployable crew-lock. The first is function tree that decomposes the overall function and sub-functions of the crew-lock into smaller systems or components that the team must consider. The second document is a transformation diagram that outlines the flows of inputs like information, energy, and forces, and the outputs after a transformation through a subsystem or interaction between the user and the system. Both the Tree and Transformation Diagram can be downloaded the Design Review Materials Section at the bottom of this page.
Detailed BenchmarkingBelow is a detailed benchmarking table that compiles information from deployable and non-deployable air and crew lock concepts. The technical papers which are referenced in this table are listed in the section named Related Standards and Technical Papers. The Detailed Benchmarking table can be downloaded in the Design Review Materials Section at the bottom of this page.
Related Standards and Technical PapersAll listed standards and technical paper links can be found on the Tabulated Sources tab in the Engineering Requirements Excel workbook. The Engineering Requirements can be downloaded in the Design Review Materials Section at the bottom of this page.
Listed below are relevant standards that will be applied to various aspects of this crew-lock design.
- NASA, NTSS, SPP-30256:001 – EVA Standard Interface Control Document Revision F
- NASA, NTSS, HDBK-6064 – Spacecraft Polymers Atomic Oxygen Durability Handbook
- NASA, NTSS, STD-5001B – Structural Design and Test Factors of Safety for Spaceflight Hardware
- NASA, NTSS, STD-3000/T – International Space Station Flight Crew Integration Standards
- NASA, NTSS, ASTM E595 – Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment
- NASA, NTSS, MIL-STD-454 – Standard General Requirements for Electronic Equipment
- NASA, NTSS, SSP 52051 V1 – User Electric Power Specifications and Standards Volume 1: 120 V DC Loads
- NASA, NTSS, SSP-52051 V2 – User Electronic Power Requirements Volume 2: Multi-Segment, Portable, 28 V DC Equipment
- NASA, NTSS, SSP 41004 PT1, REV H – Common Berthing Mechanism to Pressurized Elements Interface Control
Listed below are relevant technical papers that will be applied to various aspects of this crew-lock design.
- Department of Defense, Expandable Airlock Experiment (D021) and the Skylab Mission (1972)
- NASA, Design and Construction of an Expandable Airlock (1968)
- NASA, Clemson University, Honeywell Corporation, Breadboard Development of the Advanced Inflatable Airlock System for EVA (2003)
- NASA, EVA-EXP-0031 – Extravehicular Activity (EVA) and Alternative Ingress/Egress Methods Document (2018)
- NASA, Bigelow Aerospace, SSP-57239 – Bigelow Expandable Activity Module (BEAM) to International Space Station (ISS) Interface Control Document (2012)
Customer and Engineering Requirement ChangesDue to the detailed benchmarking obtained from the Technical Papers and Standards, and some talks with the customer, some of the Customer and Engineering Requirements have been either removed, modified, or changed. Below are the summary of changes for the Customer and Engineering Requirements tables.The full Customer Requirements and Engineering Requirements files can be downloaded in the Design Review Materials Section at the bottom of this page.
As shown below, CR#7 was removed after speaking with the customer. In an effort to refine the scope, integration with NASA modules is no longer required. The customer reiterated that the focus of this project should be on pressure management, human elements, and the deployment method of the crew-lock.
As shown below, ER#'s 4, 8, 9, 10, 17, 18, and 19 were removed after speaking with the customer and considering our own design constraints. In an effort to refine the scope, some safety elements, like the inclusion of fire extinguishers, smoke detectors, Umbilical Cord assemblies, and toolboxes is no longer required. In addition, many technical papers documenting past deployable space structures did not include any of these items during their first-phase analysis, designs, build, and tests. Weight capacity is no longer considered due to the inability to non-destructively test this on the final, scaled structure. Deployment time and Structural Weight are no longer listed as a requirements, but rather as resulting specifications of our design and build process.
As shown below, ER#'s 1, 2, 3, 5, 6, 8, and 19 were modified to more accurately reflect what was read in technical papers and NASA standards. This will help the team guide the design for the deployable crew-lock, based on past and existing deployable and rigid space structures.
As shown below, ER#'s 7, 4, 15, 16, 17, and 18 were added to more accurately reflect what was read in technical papers and NASA standards. This will help the team guide the design for the deployable crew-lock, based on past and existing deployable and rigid space structures.
Morphological ChartAfter the functional decomposition of the crew-lock, the creation of a Morphological Table followed. Below is an organized manner of viewing solutions for subsystems within the crew-lock system. The Morphological Chart can be downloaded in the Design Review Materials Section at the bottom of this page.
Feasibility AnalysisThe following are a series of preliminary, high-level feasibility analysis that the team has done in order to gauge whether the concepts and solutions to functional challenges are feasible. These analysis cannot be downloaded below in the Design Review Materials section at the bottom of the page; however, the images of them can be found in this section. The files can also be found in the Systems Level Design public directory under Feasibility Analysis.
Functional Test PlanAs a way to test specific functions the final design will incorporate, the team devised a plan which will serve as a future guide for function implementation. Various electrical and mechanical functions derived from the engineering requirements and function tree will have to be verified when a structured prototype is completed. Below, a list of these plans are outlined:
Electrical Test Plans
- Probe Vcc pin of each IC, using a multimeter, to check whether the IC is getting the right power required for it to run. For example: - Pressure Sensor (MS5607-02BA03) should have voltage supply of 1.8V to 3.6V.
- If we are using motors, we would do functional characterization of each motor using an oscilloscope to see how much inrush, running and stall currents are being drawn. This would help us include OCP and OCV components.
- Perform continuity checks on circuit board using multimeter to see whether board design (custom PCB) matches initial schematic layout.
- Probe data lines using an oscilloscope to see data transmission rate and make sure it meets our standards set the micro-controller. Sanity checks might be to see whether I2C and SPI have the same bit rate for data transmission as SPI is faster than I2C.
- Based on the micro-controller being used, functional tests can be carried out using code by using prints on terminal or checking register values of the microcontroller in the IDE.
Mechanical Test Plans
- Internal pressure test- air pump will be connected to vessel system and operated to the desired pressure. The system will sit and gauge pressure will be monitored over a set time interval
- Stress test- structure will be pushed to stress limit (within function) and individual components and the overall structure will be analyzed for signs of strain
- Handle test- The stress limits of the handles will be tested through added weights in order to determine the resiliency of the material
Concept GenerationBelow are sketches of designs. Each one has been considered and either directly inputted into the Pugh Chart for concept selection, or combined with other ideas before their input into the Pugh Chart. Each concept has been numbered and will be referenced in later sections on this page based on the number assigned in this section.
Concept SelectionBelow is a Pugh Chart. This chart is a concept downselection method commonly used by engineers during the design process. The datum, which is what the concepts are rated against, is the BEAM module which can be seen in the Detailed Benchmarking Table. The BEAM was used as a datum due to its nature of being a deployable space structure, and also due to it being a very recent, and tested module aboard the ISS. The Pugh Chart can be downloaded in the Design Review Materials Section at the bottom of this page.
Based on the above Pugh Chart, concept #4 is the highest rated base don the criteria our team found most important in judging concepts for the crew-lock. In the Selected Concept section, a more detailed written description of our selected concept can be found.
The final selected concept incorporates a majority of the design from concept #4 in the Pugh chart. The functional outline of this selected concept is as follows:
- The design is based off of a suit-port integrated crew-lock, as previously outlined in the "Concept Generation" section. As this design entails, the astronauts will enter the crew-lock directly into their spacesuits via a small air-tight hatch connecting the equipment-lock and crew-lock. The hatch on the equipment-lock side will then be shut, and a lever is released to seal the inner hatch of the crew-lock.
- The internal pressure of the crew-lock is stated to reach a maximum of 14.7 psi, with depressurization steps lowering that number to 2.0 psi and 0.0 psi, respectively. The aim is to climatize the suited astronauts before departure from the crew-lock and after re-entry.
- The crew-lock will deploy with guidance from up to four support rods placed 90 degrees from each other. These rods will extend outwards via a sliding mechanism which will be either pneumatically or electrically driven, extending out the soft structure overcoat in the process. The internal frame will lock into place and become rigid upon engagement of the sliding rods, similar to the frame of an umbrella. To redeploy, the process will reverse in a related fashion, collapsing the frame and driving the sliding rods into their initial position.
- The user interface of the functionality of the prototype will be controlled with a laptop. Deployment and sensor reading functionality will be managed from this interface for clear display and ease of use for the end user.
- For the astronauts to navigate the crew lock, collapsible handles will be integrated into the internal structure of the walls. These handles will initially be placed in a condensed form, for size constraints of the undeployed crew-lock. Once engaged by the user, these handles will pull out of their condensed form and allow minimal movement around the internal space. Once disengaged, the handle will pull back into its condensed form.
- A summarized list of additional materials is as follows:
- LED lighting for interior guidance
- Air compressor/pump for pressurization and/or pneumatic functionality
- Pressure sensors to monitor internal pressure differentials
Below is an origami representation of the way this concept would deploy and compress, as well as a picture of a model created by Brandon Lau for the Systems Level Design Review.
Risk AssessmentBelow is an summary of changes to the risk management file. The full risk management file can be downloaded in the Design Review Materials Section at the bottom of this page.
Plans For Next PhaseBelow is the Condensed Gantt Chart for Phase II. A more detailed Gantt Chart (named "Master Schedule") with task breakdowns and responsibilities can be downloaded in the Design Review Materials Section at the bottom of this page.
Conclusions for this PhaseDuring this phase, the team was able to accomplish all of the tasks detailed in the Team Vision at the top of this page. The most critical element of this phase was the discovery of multiple technical papers detailing the design, analysis, building, testing and operation of several past crew-lock and air-lock concepts. Using this newly found information, the following detailed documents could be created or modified: Transformation Diagram for system inputs and outputs, Functional Decomposition Tree for system to component tracking, Morphological Table for concepts to accomplish the functions required by the crew-lock, Updated Engineering and Customer Requirements, Feasibility Analysis, Functional Test Plans, and a Concept Generation/Selection Pugh Chart.
From the information above and the documentation created, each team member was able to craft a more feasible concept which was then weighed in the Pugh concept selection. A list of design criteria was outlined during this phase, derived from technical and qualitative properties from past designs, as detailed in the detailed benchmarking. How each member's concept compared to these criteria points determined the overall structure of the chosen design.
This phase gave the team a chance to focus the scope significantly through research and discussions. It also sets up the team for the next phase, where the selected design will undergo a subsystem, or detailed, design phase.
Systems Level Design Phase Review Notes
|Starting Date||Ending Date||Meeting Notes|
|September 2018||October 2018||Design Review Notes - Systems Level Design Phase|
Design Review Materials
- Systems Level Design Presentation
- Detailed Benchmarking Table
- Functional Decomposition Tree
- Transformation Diagram
- Morphological Table
- Pugh Chart
- Customer Requirements
- Engineering Requirements
- Risk Management
- Master Schedule