P18101: CubeSat Solar Sail

Integrated System Build & Test

Table of Contents

Team Vision for Integrated System Build & Test Phase

Tasks Accomplished:

Machined Components Assembly

Part of the work completed this phase was continuing to receive and assemble the machined components of the deployment mechanism. As these part were received they were checked for tolerancing accuracy and assembled together and their fit checked within the assembled CubeSat frame. All of the machined components were then assembled so the deployment mechanism could be tested accurately. For this to happen, holes had to be put into the test booms for a screw and nut to be tightened and hold the booms in. This was done using a drill and increasing the hole diameter until the desired size was achieved.
All Machined Components Assembled

All Machined Components Assembled

Booms Inside Machined Components with Sensors

Booms Inside Machined Components with Sensors

Deployment Testing

During this phase the deployment of the sails from the CubeSat was investigated. The sails were folded and placed within their storage location within the frame. However, before testing the sail deployment, first the deployment of the booms by the motor was checked. There were numerous issues which arose during this, resulting in an inability to extend and retract the booms consistently. After numerous changes to the components, the details of which are located in the problem tracking section and document, the booms were able to be extended and retracted by the motor. Due to the difficulty the motor had with the booms, the sail extension was first tested by hand, with the sail ripping before being deployed due to excessive force being required to deploy it. The opening in the frame it was being pulled through was then widened and another manual test conducted, but the force is still far to great for the motor to deploy the sails.
Boom Deployment Test with Motor

Boom Deployment Test with Motor

Manual Sail Deployment Test with Machined Frame

Manual Sail Deployment Test with Machined Frame

Deployed Sail from CubeSat

Deployed Sail from CubeSat

Test Results Summary

The full test plan and result document can be seen here.

Lacing Cord Durability

The area between the marks was tested.

The area between the marks was tested.

One concern with the design of the deployment mechanism was that the attachment material for the sail to the CubeSat rubs across metal edges of the frame. There was concern that this would cause damage to the material, potentially resulting in cutting it, leading to an inability to extend or retract the sail. The material selected for this, lacing cord, was chosen for its strength and durability to mitigate this concern. This was tested by pulling a test section of lacing cord across one of these Edges with a force of around 50 Newtons, significantly higher than will be expected in the actual deployment. In addition, the edge being used for testing was not filed down, so it was sharper than will be expected on the actual deployment. The lacing cord was abraded against this edge 1,000 times to test that the abrasion would not cut the cord. This is more than will occur during the desired mission life. Despite the conservative conditions of this experiment, only minor fraying and abrasion occurred. Even less abrasion damage can realistically be expected, meaning that the lacing cord being damaged from abrasion is not a concern.

Integrated System Weight Test

Once all metal components were manufactured, final booms and sails were constructed, and all electronic components could be integrated into the system, everything was weighed using a scale. With all of these components, the system came out to 1.65 kg, plus or minus five grams. From here, the system should only get lighter, as wires will be trimmed to appropriate lengths once testing is complete and the longer wires are no longer required for ease of testing. This means that the entire design will not only be below the CubeSat regulation mass of 2.66 kg, but will be below the team's ideal value of 2.00 kg as well.

Electronics Cold Test

Although we could not replicate the extreme cold of space travel, we wanted to ensure that our electronic components could endure the coldest environment available to us. The motor and the sensors were placed in a residential freezer overnight. They were tested the following morning and proved to still be functional.

Risk and Problem Tracking

Risk Management

Risk Assessment

Risk Assessment

Problem Tracking

Geneva Cam Rotation

An issue that came up during this phase was an inability to properly rotate the geneva cam assembly. There were two potential causes that were identified which could be causing this. The first of these was a slight issue with the tolerances on the components. The geneva cam grooves were slightly too shallow, causing the pin rotating the cam to get stuck in the deepest part of the groove. To fix this, the grooves were filed out slightly to make them deeper. The other issue was the moon piece was getting stuck against the cam. This was likely because the holes in the base plate were slightly too close together. To correct this, the moon piece was slightly reduced in diameter.

While reducing the diameter of the Geneva moon on a lathe partially solved the issue of components rubbing together, it was ultimately determined that the diameter of the central hole in the Geneva moon (and the disk it is attached to) was too large, allowing the components to move too much about the axis of the motor shaft, so these parts were re-machined. Following this rework, some material was taken off the diameter and height of the moon using a lathe to ensure previous issues would not happen again, and the Geneva cam began to function as intended a majority of the time. In addition to the work done specifically on the Geneva moon, various other components were hand-sanded using needle files and sandpaper to clear up minor interferences that did not require heavy machinery to fix.

Sail Corner Reinforcement

To pull the sail out for deployment loops of lacing cord were required to attach to the booms. These were originally put through holes that were made in the sail material, but the material easily ripped. The first attempt to correct this was to reinforce the corners with the metalized mylar tape and to then put a hole through that. The idea was that the tape would make the corner more resistant to tearing. However, the tape still tore. Duct tape was then used to reinforce the corners instead, and although then the corners still tore under high enough force, they could withstand enough to be extended by the booms.

Mounting Plate Machining

While a majority of parts were manufactured to tolerance and issues arose from the specified tolerances being too tight, the metal outer mount required some rework due to some internal filleted edges being larger than the required dimensions. This kept the inner mount from being able to fit inside the outer mount. These rounds were machined down to the correct, smaller radius, and after some minor filing to improve ease of motion, the gyroscopic mounting plate was able to be completely assembled and inserted into the frame, functioning exactly as designed.

These processes can be seen in the problem tracking document here.

Functional Demo Materials

Plans for next phase

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