Wednesday, August 24, 2016

Bringing "Balance" to the ISS

The Z1 truss was the first latticework structure added to the ISS.  This component provides a number of station functions, including attitude control via a redundant set of control moment gyroscopes (CMGs), two plasma contactors to neutralize static electric buildup on the station's surfaces,  a Ku-Band space-to-ground antenna (SGANT), an S-Band antenna support assembly (SASA), Manual Berthing Mechanism (MBM) ring used to temporarily "park" PMAs during the station assembly sequenceand various electrical and cooling system assemblies to support  integration of solar power and ammonia-based heat dissipation systems added by future ISS assembly missions. The truss also provided a temporary mount for the P6 truss , delivered during STS-97, which provided early solar power capability to the station.

The Z1 truss and a third pressurized mating adapter (PMA-3)  were launched aboard STS-92 on October 11, 2000.  The components arrived at the station aboard Space Shuttle Discovery on October 13 and were added to the station configuration during a series of four EVAs that occurred between October 15 and 18.

The parts for this step in the build consists of three parts pages and a 14 page instruction manual.  Two of the parts pages are part of the for-purchase AXM combo kit #1 (Z1 truss, PMA-3). The third parts page (S-Band antenna with cover) is part of the STS-92 shuttle kit graciously provided by AXM upon my request.

I started the build by cutting out the main Z1 assembly box and removing the MBM ring and CMG interior areas.

Next, I cut off all joiner tabs and lapped them to achieve a flush fit on all seams.

I then cut out and layered the inner section of the MBM ring to achieve depth and assembled the Z1 main body "cube".

I then moved to the top area of the truss, again applying layering to achieve depth and inserting magnets at the four Rocketdyne Truss Attachment System (RTAS) attachment points to accomodate future magnetic attachment of the P6 truss.  I added a fifth magnet at the center forward point on the top to provide a display hang point for the mated Z1 and Unity components.

Next, I assembled the plasma contactors and DC-to-DC Converter Unit-Heat Pipes (DDCU-HP).

I then affixed the top and bottom sections to the Z1 "cube" and then placed the plasma contactors and DDCU-HPs at prescibed points.

I then built the lower section of the P6 truss, building out the feet with magnets to ensure proper alignment of the P6 base to the Z1 RTAS locations.

Next, I turned my attention to building the 4 CMGs and thermal blanket.  Cutting these parts out was a bit tedious due to the numerous curves.

 I then cut out and affixed the trunnion pins and scuff plates.  I used sections of a paper clip for the actual pins.

I then assembled the CMGs, adding a nub to the top of each (using a small section of bamboo skewer) to add realism.  The assembled CMGs were then glued into the proper locations on the aft side of the Z1 "cube".  I consulted various photos of the truss to ensure that the CMGs were inserted at the proper orientation into the cutout areas.

Next, I asssembled the Ku-Band SGANT dish and boom.  I fabricated a nub at the prescribed mount point on the zenith plane to accomodate simple attachment of the antenna boom.

Next, I turned my attention to the fluid line cable tray.  I glued together the front and back sections and then layered key sections cutout from another printout of the parts to obtain depth.  I applied 28-gauge coated wire to add realism.

I assembled covered and uncovered versions of the S-Band Antenna Support Assembly (SASA).  The covered assembly is used initially, replaced by the uncovered version that was placed at the top of the P6 truss during STS-97.

During my studies of various Z1 photos, I learned that a second Ku-Band antenna was added to the Z1 truss during STS-132.  I decided to add a magnet at the prescribed point, which required me to remove the upper right CMG so that the magnet could be glued at the inside zenith area.  I affixed the magnet and re-glued the CMG.

I then assembled PMA-3, following the same process that was used during my prior builds of PMA-1 and PMA-2.

My test fit of the magnetic attachment of the Z1 truss to Unity's zenith docking port identified a need for additional connection force.  I decided to add a magnet at the center of each docking port.  I cut out the porthole cover or each port, inserted a magnet the the center of each cutout, and affixed a cutout of each porthole cover over each magnet to hide it.  I also added a circular cover to the bottom of the Z1 truss with a magnet glued to the backside.  

The additional magnet pair provided the necessary additional force to ensure a snug bond between the Z1 and Unity components.

I then transported the component to my office, where I mated the Z1 and Unity to the other station components.

Now, onto the next component, Soyuz TM-31, which brought the first IIS expedition crew to the station in early November, 2000.  Stay tuned!


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  2. Congrats! The use of magnets was a great idea. This is fabulous!