Space Grant Consortium - University of Wisconsin - Green Bay

• CAD models of thermal hardware, including Vishay-Dale wire-wound resistor
survival heaters and Honeywell 706S thermal switches, were created; and
• Material for various critical design review presentations was created.
Remarks on Project Results
Integration and Test
Two major challenges were encountered when assisting with the preparations for the thermalvacuum
and vibration testing. These challenges are outlined below.
Vibration
A fixture is required in order to fix the PMD instrument to the vibration test apparatus. This
fixture took the shape of a thick plate with numerous hole patterns through which test hardware
and PMD fasteners will be applied. As outlined in the previous progress report, the first iteration
of this plate was returned from the vendor with numerous errors. Primarily, the hole pattern that
allowed for a bolted interface between the test hardware and the test fixture was found to be
partially misaligned in such a way that properly bolting down the plate was impossible. More
minor issues with the plate involved a missing counterbore on one hole and an irregular
counterbore on another. In addition, an issue with the design arose in that the counterbores were
not large enough in general to fit the washers that were required.
In order to rectify this, the manufacturing engineer that was acting as liaison between the vendor
and PMD was contacted. The problems with the current plate were explained and the existing
work was compared to the provided mechanical drawing. A new drawing was created that
included an updated, larger counterbore diameter with tolerances assigned to prevent a smaller
hole from being drilled. The updated drawing was then forwarded on to the vendor, who had
previously agreed to replace the part at minimal cost to PMD. The following Monday, the new
fixture arrived and was fit checked against the vibration test equipment. No issues were found
and the fixture will be stored until it is needed to support dynamics testing.
Thermal-Vacuum Testing
Preparation for thermal-vacuum testing proved to be more challenging than previously thought.
The difficultly with both running thermal analysis and writing thermal test plans was
significantly underestimated in the initial work project for the summer. In addition, undefined
thermal test requirements in the NuSTAR environmental requirements document (to which PMD
must adhere) delayed developing the test plan and invalidated a significant amount of the draft
test procedure. Coupled with pressure from pending critical design reviews, this resulted in a
significant delay that preventing some analyses from being completed.
PMD Kinematics Model
The PMD kinematics model, while mostly a successful endeavor, encountered problems with
numerical stability in the point accelerations to body accelerations calculations. The model used
a technique developed by Dr. Jorge Angeles in a paper entitled “Computation of Rigid-Body
Angular Acceleration From Point-Acceleration Measurements” [1]. A detailed analysis was
conducted of the instability and compared to the technique developed in the paper. It was found
that the technique was properly implemented in MATLAB and the source of the stability was the
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