Subsystem Build & Test
Team Vision for Subsystem Level Build & Test PhaseDuring this phase, the team wanted to complete individual subsystem development. The electrical engineering team will complete PCB design in order to complete a review from professors and to request a quote from board manufacturing companies. The bulkhead team will complete CNC preparation and possibly CNC the bulkheads by the next review. At the very least the bulkheads will have a CAM program approved by the Construct director. The vacuum barrier team will be completing heat sealing, adhesive sealing, and load testing on the vacuum barrier material and ergonomic devices. The testing rig team will begin preliminary plans to build the testing rig for the final crew-lock. The team expects to further investigation of the components bought for their subsystems and complete preliminary testing on the components as necessary.
Problem TrackingThe Problem Tracking sheet can be downloaded in the Design Review Materials Section at the bottom of this page.
Change ManagementThe Change Management workbook can be downloaded in the Design Review Materials Section at the bottom of this page.
The changes detailed below were driven by the problems listed in the Problem Tracking document above.
The major design update which was made during this phase was the change from solid bulkheads to machined bulkheads with vinyl film sandwiched in between. An airtight zipper is also added to the EV bulkhead for PCB maintenance and for a simulated EVA hatch. This was done to accomplish the following:
- Reduces overall bulkhead weight
- Changes vacuum barrier interface from gasketing on MDF to heat sealing on airtight vinyl film
- Allows for views of the inside of the crew-lock and ergonomics
- Airtight zipper can be secured to vinyl film as a maintenance access and as a simulated EVA hatch
- Allows for usage of bolting rather than wood screw fastening
- Allows for attachment (sandwiching) of the vinyl film side panels
- Vinyl film allows for attachment of sewn handles
- Is a more aesthetically pleasing design
Below is an image of an exploded view of the EVA Bulkhead side. The layers are named from bottom left to top right: EVA Outer Bulkhead, Vinyl Layer, EVA Inner Bulkhead.
Below is an image showing the vinyl wrapping into the EVA bulkhead sandwich towards the IVA bulkhead sandwich.
Testing Flow ChartDue to the interdependence of the Subsystems, the team created a flow hart to illustrate the roadblocks the team has come to for this phase. Most of the testing and building will come together in the next phase.
Test Results SummaryThe Test Results Summary and all the tests in the following section can be downloaded in the Design Review Materials Section at the bottom of this page.
Vacuum Barrier TestingVacuum Barrier Material testing was one of the most important parts of this phase. The ability of the material to heat seal to itself and the vinyl parts of the bulkheads, the material's ability to work with the glue which the team has on hand, and the vacuum barrier material's strength are all important factors for the Crew-Lock's successful delivery and function.
Below are the results for the 3 sets of tests done on the Vacuum barrier Material.
Navigational Aids TestingThe Handles Test was meant to look at the strength of the bond between the handle and the vacuum barrier material, as well as the strength of the handle itself. Matty performed a stitch and glue pattern that created a handle acceptable for the theoretical 1/4th scale astronaut who will be using them as navigational aids on the Crew-Lock.
Electrical Components TestingThis phase mainly focused on the design and confirmation of the PCB, thus the testing done on the electrical side was limited to individual components that could be supplied with power.
LED Lighting TestThe Crew-Lock LEDs were tested to confirm the pins (12V and ground) and to confirm that they can be lit. The test went through several iterations where voltage was varied to see the LED response to the changes. The results can be seen below.
Pump TestingThe Crew-Lock pump was tested to confirm that it was indeed functional. The pump was hooked up to a car's 12V port and turned on. The video can be seen by following the link seen here: 12V Pump Test Video
Risk Management ChangesThe full Risk Management workbook and the Problem Tracking sheet can be downloaded the Design Review Materials Section at the bottom of this page.
Risk Management Changes
BulkheadsDuring this phase, the bulkhead team consulted multiple sources for better clarification on what material and fabrication method should be used to complete the bulkheads. After this consultation, the team ultimately decided to stick with Temple-Inland UltraStock Select Medium Density Fiberboard (MDF) due to:
- 20% Cheaper Price (compared to other hardwood panels)
- Superior Surface Finish (150 grit finish w/ laminate)
- Superior Machinability (Better density uniformity compared to other hardwood panels)
- Environmentally Friendly and Safer for Humans (Reduced Formaldehyde Emissions)
- Accepts many types of paint, laminate, and veneer
- Low warp and high straightness standards (± 1/64")
In addition, the design changes no longer requires the MDF to have an air-tight, wood-epoxy finish. The vinyl and vacuum barrier material will be the air-tight interfaces, thus freeing the design restraint placed on the wood material.
The main work on the bulkhead during this phase consisted of modifying the drawings for the bulkheads to conform to the new design changes. These drawings were then brought to the RIT Construct where the director of the area, Michael Buffalin IV, provided machining advice to the team. The Construct also provides a Drawing to Vector Profile to CAM g-code program. This program is attached to the ShopSabre CNC Router 4860. The CAM program outputs a simulation to confirm cutting as well as tool-path G-code and operations orders delineations to the CNC router. The tooling to be used during the machining include:
- 0.25 inch multi-flute end-mill
- 0.3125 inch drill
- 3.4 mm drill
The Operations Orders were decided based on the inside-to-outside principle of CNC machining and feature importance. The safety tabs were decided based on consultation with the Construct. The securing of the bulkhead material will be accomplished through wood-screwing and double-sided tape based on consultation from the Construct. Peck depth, cut depth, feed, speed, and spindle RPM were/will be decided based on consultation with the Construct.
CAM Program OutputsAll G-code tool-paths and vectoring program files can be downloaded the Design Review Materials Section at the bottom of this page.
Deployment SystemsFor the deployment systems design, a CAD drawing was made of the motor bearing support for the purpose of fabrication in the RIT Machine shop. In order to set the job up in the shop, model and drawing files were required. In addition to this, the pair of two threaded metal rods for the motor were cut in half manually to ensure that enough pieces were made to accommodate the amount of motors (three).
Electrical SystemsThe PCB design was completed by the electrical team and approved by the professors from the RIT EE department. Quotes for the boards are as follows:
- Sensors Board
- OSH Park - 3 Boards for $10.90
- PCBWay - 5 Boards for $22.00
- Motor Controller Board*
- OSH Park - 3 Boards for $144.70
- PCBWay - 5 Boards for $62.00
The following are views of the PCB associated with the Sensors suite.This includes the proximity sensor and pressure sensor.
The following are views of the PCB associated with deployment control (motors and threaded rods system).
Testing RigThe bulkhead clamp sub-assembly of the testing was modeled and drawn, as seen below. The purpose of the bulkhead clamp is to ensure a secure connection between each bulkhead and the mount and translational systems of the testing rig. Each of the pieces of the bulkhead clamp will be created out of wood, which was picked up as scrap during the previous phase.
Once the bulkhead machining is complete in the early part of the next phase, the bulkhead clamp can be accurately traced and machined. The scooter will be measured and the clamp will be attached. The scooter's height will be taken into consideration as the clamp for the IVA side is built, so that both bulkheads sit on the same horizontal plane.
BOM and Finance TrackingDuring this phase, components, expenses, and confirmation were tracked on a workbook. The main problem the team had in this area was the lack of funds due to an administrative error. The team was mistakenly allotted $1,000 when we had requested and planned for $1,500.
The BOM workbook and Expense Tracking can be downloaded the Design Review Materials Section at the bottom of this page.
Conclusions for this PhaseThis phase brought about many problems that the team had to face. First, we ran into design and testing problems early on which forced the team to re-think the way the vacuum barrier should be attached to the bulkhead. Second, the team had trouble contacting the right suppliers and fabrication specialists to complete purchasing and fabricating on schedule. Third, the team faced financial woes, as the MSD program mistakenly allotted $1,000 to the team, instead of the $1,500 budget we had requested. These problems led to the lack of deliverables during the Subsystem Build & Test phase review and demos. This puts the team slightly behind schedule and thus more hard work must be done in the coming phase.
Despite the negatives this phase brought, the team has been able to solve two of the three problems mentioned above in time for this phase review. Substantial design changes, for both functionality and aesthetic reasons, were made and approved by the entire team. These design changes made the envisioned final product more acceptable to the team, and more easily manufacturer. The suppliers and fabrication experts were contacted, and all issues were addressed. The finance problem was solved a few days before the Subsystem Build & Test review, allowing the team to turn its focus away from financial woes and back towards fabrication and testing.
Plans for next phaseIn the next phase, Integrated System Build & Test, the team will be focusing mainly on the fabrication and integration of all subsystems. The team anticipates that all subsystems will be complete, and testing can be done to confirm functionality. The schedule shows that the team is not exactly where it wants to be as it heads into this phase; however, with a month's more time, the team should be able to get back on schedule.
For the next phase, the team will complete the following: complete the PCB, complete the bulkheads, complete the vacuum barrier attachment, complete the motor and threaded rod system integration, complete the ergonomics attachments to the entire crew-lock, finish wiring to all components, complete the testing rig, complete testing of the full system, and start on the Technical Paper and Imagine RIT Poster.
The Detailed Gantt Chart and Schedule can be downloaded the Design Review Materials Section at the bottom of this page.
Subsystem Build & Test Phase Review Notes
|Starting Date||Ending Date||Meeting Notes|
|January 2019||February 2019||Design Review Notes - Subsystem Build and Test|
Design Review Materials
- G-code and Vectoring Program Files
- Handle Test Plans
- Vacuum Barrier Material Glue Sealing Test
- Vacuum Barrier Material Heat Sealing Test
- Vacuum Barrier Material Strength Test
- Final Crew-Lock BOM
- Expense Tracking
- Change Management System Sheet
- Problem Tracking
- Risk Management
- Master Schedule
- Phase 6 Presentation