Main Bus Switching Unit (MBSU) 3 Failure: This morning, a critical bus loss occurred on MBSU 3 that brought down loads on channels 3A and 3B. Major impacts included KU-band, Alpha Magnetic Spectrometer (AMS), Control Moment Gyro (CMG)-3 and Space Station Remote Manipulator System (SSRMS) redundancy. Troubleshooting was not successful and teams are assessing the possibility of a power supply failure. A Flight Investigation Team (FIT) is meeting this afternoon to discuss a forward plan. Console teams are working through jumpering plans and alternate power strings to maintain key loads. KU-band communication has been regained. AMS swapped loads to channel 4A and has resumed nominal operations.

Remote Power Control Module (RPCM) Z14B_B Remote Power Controller (RPC) 12 Trip: In response to the MBSU 3 failure and loss of operational power to Control Moment Gyro (CMG)-3, teams attempted to close RPCM Z14B_B RPC 12 to provide survival heater power to CMG 3. Upon closure attempt, the RPC tripped open. This is a Type V external RPCM and is susceptible to hybrid Field Effect Transistor (FET) issues. Teams are working within thermal clocks and discussing mitigation plans.

Fiber Optic Production: Crewmembers performed the Fiber Optic Production setup. Physical Optics Corporation’s (POC’s) Fiber Optic Production investigation creates optical fibers with high commercial value aboard the International Space Station (ISS) using a blend of zirconium, barium, lanthanum, sodium, and aluminum called ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF). Fiber Optic Production operates within the Microgravity Science Glovebox (MSG). Extensive theoretical studies along with a limited number of experimental studies suggest that ZBLAN optical fibers produced in microgravity should exhibit far superior qualities to those produced on Earth. The resulting optical fiber from Fiber Optic Production is expected to help verify these studies and guide further engineering efforts to manufacture high value optical fiber in large volume aboard the ISS.

SlingShot: The crew installed a data cable inside Cygnus in support of the Slingshot deployable system. SlingShot is a small satellite deployment system that fits inside the Cygnus spacecraft’s Passive Common Berthing Mechanism (PCBM). SlingShot can accommodate up to 18 satellites that are deployed post Cygnus unberth.

Cryo Chiller: The crew stowed the Cryo Chiller tools into the Cryo Chiller facility. Cryo Chiller is a single Expedite the Processing of Experiments to Space Station (EXPRESS) locker replacement unit that provides rapid freezing capability in support of biological sciences, as well as temperature-controlled transfer to/from the ISS on visiting vehicles.

The ISS Experience: A crewmember performed an ISS Experience Log recording today. The ISS Experience creates a virtual reality film documenting daily life aboard the ISS. The 8 to 10 minute videos created from footage taken during the six-month investigation cover different aspects of crew life, execution of science aboard the station, and the international partnerships involved. The ISS Experience uses a Z-CAM V1 Pro Cinematic Virtual Reality (VR) 360-degree camera with nine 190° fisheye lenses.

Thermal Amine System: Thermal Amine Scrubber passed its leak checks over the weekend and rack and locker power were applied this morning. Verification of proper connection to the Adlink Mini-PC and activation steps have been delayed due to the MBSU failure this morning. Thermal Amine System tests a method to remove carbon dioxide (CO2) from air aboard the International Space Station, using actively heated and cooled amine beds. Controlling CO2 levels on the station reduces the likelihood of crewmembers experiencing symptoms of CO2 buildup, which include fatigue, headache, breathing difficulties, strained eyes, and itchy skin. The system includes elements that reduce loss of water vapor, and recover CO2 for use in electrolysis to produce oxygen.

Remote Power Control Module (RPCM) S01A_B Remote Power Controller (RPC) 2 Trip: On Sunday, RPCM S01A_B, RPC 2 tripped. This trip removed power from RPCM S31A_A and its downstream loads which include the S3-1 Multiplexer/Demutliplexer (MDM), Starboard (Stbd) Solar Alpha Rotary Joint (SARJ) Rotary Joint Motor Controller (RJMC) 1, S3 Aft Wireless Video System (WVS) External Transceiver Assembly (WETA), Stbd SARJ RJMC 2 Heaters, S3-1 Payload Attach System (PAS) 1 Umbilical Mechanism Assembly (UMA), and the S3 PAS 4 UMA. S3-2 MDM assumed bus control and the SARJ was recovered and is in autotrack. No overcurrent was seen in the latched Direct Current to Direct Current Converter Unit (DDCU) 50Hz data. RPCM S01A B is a type VI RPCM, which is not susceptible to hybrid Field Effect Transistor (FET) issues. A FIT held today recommends loading RPCMs S01A_B and S31A_A with the 1kHz firmware and reclosure of RPCM S01A_B, RPC 2 and repower of downstream loads.

Oxygen Generation Assembly (OGA) Filter Screen Repair: The crew noted during a weekly housekeeping activity that the OGA intake screen was broken. After reviewing downlinked images taken by the crew, it was determined the upper left corner of the front screen was pushed inward, allowing for a partial by-pass of the screen through a corner gap. Today the crew repaired this damage by prying the corner forward and applying aluminum tape over the edges.

Node 3 (N3) Charcoal HEPA Integrated Particle Scrubber (CHIPS) Filter Install: The crew removed four existing bacteria filters in N3, cleaned two area smoke detectors, and replaced the filters with the new CHIPS filters that were delivered on Cygnus. By adding charcoal to the filter system, experts hope to scrub volatile siloxanes from the air before they can affect other ISS systems. Installing these filters on ISS is a key objective for NASA’s exploration vehicle programs because data collected after the install will determine how charcoal affects the life of the Water Processor Assembly (WPA) and other downstream hardware. N2 filters were replaced last week.

Cargo Operations Conference: In preparation for SpX-17 arrival, currently scheduled on May 4, the crew participated in a conference with ground teams today to discuss the cargo transfer plan.

Public Affairs Office (PAO) Live Event: Today Nick and Christina participated in a live PAO event with NASA Administrator Jim Bridenstine, Associate Administrator Bill Gerstenmaier, and Deputy Associate Administrator Steve Clarke. This event was geared toward college students. NASA has partnered with American Institute for Aeronautics and Astronautics (AIAA), Students for the Exploration and Development of Space (SEDS) and NASA STEM’s Space Grant Consortia to bring students together so they can learn more about the lunar exploration plans and how they fit into the picture. This event hopes to engage college students as they determine majors and make plans to enter the work force.

Completed Task List Activities:

Saturday Housekeeping printouts replace



Sunday CSA Space Food video P/TV red helium swap SABL-1 hard drive swap



Ground Activities:

All activities are complete unless otherwise noted.



MBSU Troubleshooting

3B1 Battery Capacity Test [Aborted]

Look Ahead:

Tuesday, 04/30 (GMT 120):

Payloads:

Behavioral Core Measures (NASA)

ISS Experience recording and H/W relocate (NASA)

Food Acceptability (NASA)

Kidney Cells CO2 Control Swap (NASA)

Actiwatch Plus chk (NASA)

VEGGIE OBT (NASA)

Fiber Optics Production Sample Exchange (NASA)

Spaceborne Computer removal (NASA)

Z-Book setup for ER8 (NASA)

SABL-3 CO2 Install (NASA)

Astrobee review and crew conf and Fly around (NASA)

CIR/ACE sample photo (NASA)

Systems:

Dragon ROBoT OBT

Emergency mask stow

Wednesday, 05/01 (GMT 121):

Payloads:

Life Science Glovebox-crew restraint install and Work Volume deploy(ESA)

Rodent Research-12 Mass Measurement setup (NASA)

Systems:

Crew off duty

Today’s Planned Activities:

All activities are complete unless otherwise noted.

