P16102: RIT-SPEX Structure
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

Week 3 Individual Goals

Anthony, System Integrator

Paul, Deployable Mechanism Designer

Rob, Structures Designer

Tristan, Deployable Device Designer

Completed Goals

Anthony, System Integrator

Paul, Deployable Mechanism Designer

Rob, Structures Designer

Tristan, Deployable Device Designer

Assembled Prototype

For this review we printed an entire prototype out of ABS plastic. This prototype lacks thermal, mass and strength properties of the final product. Despite this, we were still able to test assembly and deployment and find necessary design changes.
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Design Updates

Rail Changes (2/23/16)

Rail Changes (2/23/16)

Some changes were made in the design of the rails to account for hardware. Holes were added in the ends to allow assembly of the plunger spring and deployment switch.

Simulation Verification

Vibration

To validate our vibration simulation techniques used in MSD Phase I, we spoke with a subject matter expert from the mechanical engineering department. After reviewing our procedure with Dr. Ghoneim, he agreed that we had accurately represented the launch conditions, assuming our design does not contain any loose parts.

Acoustic vibrations are not a concern for our design due to the fact that the acoustic pressure is minimal, and the materials we used have strong damping characteristics.

How will thermal expansion affect the clearances in our hinge mechanism?

Based on calculations from our nominal hinge size, and Ultem's low thermal expansion coefficient of 65e-6 m/(m C). Even across the entire operating range of the CubeSat from -40 to 40 C, the critical hinge dimensions will change by less than 0.0005" this small change in dimensions will not adversely affect hinge performance.

Ultem High Temperature Performance

Assembly Instructions

The idea is to machine the rails first, assemble the deployable structure on the hub plate and the pre-assemble the hot plate and insert it.

Video of Assembly Process

Procedure for Machining Rails

Rail Machining Reference

Procedure for Printing Ultem Components

Test Results Summary

Test Plan

Table Top Deploy

This test involves deploying a prototype CubeSat in a lab ambient setting. The NiChrome hot knife's ability to cut the restraining line, the springs' ability to deploy the panels and the ability of one hot knife cut to free both panels were all tested. ER5 - Time from command to deploy, is tested.

Test Plan

Table Top Test Plan(2/23/16)

Table Top Test Plan(2/23/16)

Videos of Test

Hot Knife Deployment Test

Hanging Deployment Test

Results

This test was a partial success. The hot knife was able to sever the restraining line. The springs were able to deploy the panels once the restraining line was free. However, the restraining line became stuck in its routing and the second panel did not deploy.

The time from command to deploy was 4 seconds which satisfies ER-5 which requires the deployment to happen 8 seconds after the signal is received.

Takeaways

After this test, we are comfortable with our design of the spring-high system and the hot knife. Modifications to the path of the restraining line will be made to reduce the likelihood of it becoming stuck.

Fit Test

This test involved the checking the CubeSat dimension wise for both clearance and protrusion space. The CubeSat has to fit in the PPOD and abide by other constraints. This test satisfies ER-4 protrusion space, and ER-8 CubeSat clearance.

Test Plan

Fit Test Plan(2/23/16)

Fit Test Plan(2/23/16)

Photos of Test

Fit Test CheckList (2/23/16)

Fit Test CheckList (2/23/16)

Results

Fit Test Results (2/23/16)

Fit Test Results (2/23/16)

Takeaways

Current Design Package

Hub Plate Changes (2/24/16)

Hub Plate Changes (2/24/16)

Upon 3D printing Prototype II, installation of the spring showed drifting off of the lifted tabs. So to ensure that the spring deflection is consistent retaining blocks were added which is shown above.

February 11th Design Revision

February 24th Design Revision

Current Design Weighs 360 grams, with 5 50 gram solar panels attached, indicating a total system mass near 145 grams.

Mass Breakdown Feb 24

Mass Breakdown Feb 24

Ordering Status

Many of our components have been finalized in the past few weeks and all updates to the bill of materials and our status in obtaining them are shown below. Most notably, we have settled on our method of obtaining Ultem. Stratasys has suggested they can print our components for free provided we share our results with them. This assuages our budgetary concerns and gives us more confidence in our ability to print in Ultem in a reasonable time frame.
Updated BOM(2/23/16)

Updated BOM(2/23/16)

Risk and Problem Tracking

Risk Assessment

The new plan to outsource printing to Stratasys reduces the severity of the risk of RIT not being able to print in Ultem. While it would still be good to have Ultem printing in-house for spot fixes and future production, the project can survive without RIT doing the printing.
Updated Risk Assessment(2/21/16)

Updated Risk Assessment(2/21/16)

Problem Tracking

We have made significant strides in mitigating the problems that were facing our project. Most importantly, we have found a source of affordable, high quality Ultem printing in Stratasys. Initial prototype assembly has also allowed us to eliminate concerns we had about aluminum stock being too small and hinge springs being too weak.
Updated Problem Tracking(2/23/16)

Updated Problem Tracking(2/23/16)

Obtaining Ultem

The biggest issue of this phase has been obtaining Ultem with which to print. Our original plan was to order Ultem from Fisher-Unitech but we discovered we are out of their ordering range. Alternatively, we tried to order Ultem from Stratasys but they were reluctant to sell filament directly to us. Due to the importance of obtaining printing material, we have developed several alternatives and backups.

Delrin Printing

During our material selection phase, Delrin was our second choice to print in. Due to the issues that have arisen with Ultem printing, the use of Delrin as a material was reconsidered. Delrin is relatively cheap and easy to purchase, costing only $50 for a 1kg spool of filament. Delrin also has the advantage of having similar physical properties to Ultem so that some testing, and even the final product, could be made of Delrin if absolutely necessary. Despite the similarity in mechanical properties between Delrin and Ultem, if the final product were to be built in Ultem, Delrin tests would not give us as much confidence in the viability of an Ultem CubeSat as if we used the real thing during tests. Dr. Cormier has also expressed reluctance to print in Delrin due to the potential toxicity of the material at high temperatures. Because of these drawbacks, we consider printing in Delrin to be an inferior option. Delrin printing will not be considered again unless we are unable to purchase Ultem from a third party out of state.

Alternate On Campus Print

A Fortus 360MC is apparently in the Golisano College of Computing and Information Sciences. A previous group has printed with Ultem on campus on this printer this is the link to their home page. The group created a device that required the use of Ultem 9085 to 3D print their parts. Documentation would suggest that their is a printer on campus. Previous senior design team (P15611) that printed with Ultem was contacted. Their printing was not done on campus but rather with Caldwell manufacturing which they had a relationship with.

Stratasys Sponsorship

In our search for more Ultem sources, an Ultem distributor recommended us to the Stratasys sponsorship program. He felt that our unique project may be something that Stratasys would be interested in supporting. We have applied to the program and are waiting for a response in the coming days. This would give us the ability to print our Ultem parts for free. In exchange for this service, they would like us to share a report of our project and how Stratasys was able to help us create our parts.

Outsourcing Quotes

Incept3d-$650, 2 Weeks Lead Time

Stratasys-$450, 3 Day to Ship

Resource Plan

Resource Plan(2/10/16)

Resource Plan(2/10/16)

Plans for next phase

MSD Plan(Updated 2/24/16)

MSD Plan(Updated 2/24/16)

Deliverables

ImagineRIT

Application 666 made for our project, Will be working with RIT SPEX to set up COS Hallway for Space Systems. ===

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