P19127: XHab Deployable Crew Lock Structure
/public/

Systems Design

Table of Contents

Team Vision for Systems Level Design Phase

During 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 Decomposition

Below 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.
Functional Decomposition

Functional Decomposition

Transformation Diagram

Transformation Diagram

Detailed Benchmarking

Below 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.
Detailed Benchmarking Table

Detailed Benchmarking Table

All 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.

  1. NASA, NTSS, SPP-30256:001 – EVA Standard Interface Control Document Revision F
  2. NASA, NTSS, HDBK-6064 – Spacecraft Polymers Atomic Oxygen Durability Handbook
  3. NASA, NTSS, STD-5001B – Structural Design and Test Factors of Safety for Spaceflight Hardware
  4. NASA, NTSS, STD-3000/T – International Space Station Flight Crew Integration Standards
  5. NASA, NTSS, ASTM E595 – Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment
  6. NASA, NTSS, MIL-STD-454 – Standard General Requirements for Electronic Equipment
  7. NASA, NTSS, SSP 52051 V1 – User Electric Power Specifications and Standards Volume 1: 120 V DC Loads
  8. NASA, NTSS, SSP-52051 V2 – User Electronic Power Requirements Volume 2: Multi-Segment, Portable, 28 V DC Equipment
  9. 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.

  1. Department of Defense, Expandable Airlock Experiment (D021) and the Skylab Mission (1972)
  2. NASA, Design and Construction of an Expandable Airlock (1968)
  3. NASA, Clemson University, Honeywell Corporation, Breadboard Development of the Advanced Inflatable Airlock System for EVA (2003)
  4. NASA, EVA-EXP-0031 – Extravehicular Activity (EVA) and Alternative Ingress/Egress Methods Document (2018)
  5. NASA, Bigelow Aerospace, SSP-57239 – Bigelow Expandable Activity Module (BEAM) to International Space Station (ISS) Interface Control Document (2012)

Customer and Engineering Requirement Changes

Due 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.

Customer Requirements - Phase II Removed

Customer Requirements - Phase II Removed

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.

Engineering Requirements - Phase II Removed

Engineering Requirements - Phase II Removed

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.

Engineering Requirements - Phase II Modified

Engineering Requirements - Phase II Modified

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.

Engineering Requirements - Phase II Added

Engineering Requirements - Phase II Added

Morphological Chart

After 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.
Morphological Table

Morphological Table

Feasibility Analysis

The 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.
Structural Stress Analysis

Structural Stress Analysis

Structural Material Coverage Cost Analysis

Structural Material Coverage Cost Analysis

Pressure Sensor Sensitivity and Leak Assessment Analysis

Pressure Sensor Sensitivity and Leak Assessment Analysis

Pressure Sensor Wiring and Min/Max Analysis

Pressure Sensor Wiring and Min/Max Analysis

Rough Project Cost Analysis

Rough Project Cost Analysis

Functional Test Plan

As 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

Mechanical Test Plans

Concept Generation

Below 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 #1

Concept #1

This first concept's main idea was the use of telescoping or threaded, motor-driven rods to push out a deployable frame. The outerwalls and overall structure would be supported by structural supports that lock into place as the rods push the structure outwards.
Concept #2

Concept #2

The second concept's main idea was the use of potential energy from a memory material. The memory material (like memory foam) would be under tension until deployment. This tension would slowly be released during deployment. Pulleys and a motor would be the main driving force for deployment and contraction of the memory material structure.
Concept #3

Concept #3

Similar to concept #2, this concept uses potential energy to deploy. The concept involves a giant spring as the crew-lock structure. The spring would be held under compression when not deployed, and then a controlled release using pulleys and motors would occur during deployment.
Concept #4

Concept #4

Concept #4's main idea involves the recent research and development into space suit ports. This concept is explained further in the Selected Concepts section. The structure itself involves the same deployment method as Concept #1; however, spacesuit ports allow for a smaller overall volume of the structure than a normal crew-lock.
Concept #5

Concept #5

Concept #5's main idea was the use of inflateable tubes that run along the inside of the crew-lock structure. During deployment, these tubes would be pressurized, adding rigidity to the structure and deploying the structure through applied pressurization.
Concept #6

Concept #6

Concept #7

Concept #7

Both Concept #6 and #7 involve the creative use of origami. Concept #6 uses a semi-rigid cube structure that deploys and compresses as the bottom of the structure spins via a large gear. Concept #6 is better-described by looking at the real-life origami version of it below. Concept #7, on the other hand, uses two cams and motors to push sides of a cube together in order to turn a flat geometry into a cubic space. When the cams-motor combination pushes the sides of the geometry outward, the walls are forced upwards creating the crew-lock volume. Concept #7 can also be better described by looking at the real-life origami version of it below.
Concept #6 Origami

Concept #6 Origami

Concept #7 Origami

Concept #7 Origami

Concept Selection

Below 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.
Pugh Chart

Pugh Chart

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.

Selected Concept

Concept #4 - The Selected Concept

Concept #4 - The Selected Concept

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:

- 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.

Concept #4 Origami

Concept #4 Origami

Concept #4 Model for Systems Level Design Review

Concept #4 Model for Systems Level Design Review

Risk Assessment

Below 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.
Phase II Updates to Risk Assessment

Phase II Updates to Risk Assessment

Plans For Next Phase

Below 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.
Condensed Gantt Chart - Phase II

Condensed Gantt Chart - Phase II

Conclusions for this Phase

During 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


Home | Planning & Execution | Imagine RIT

Problem Definition | Systems Design | Preliminary Detailed Design | Detailed Design

Build & Test Prep | Subsystem Build & Test | Integrated System Build & Test | Customer Handoff & Final Project Documentation