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Saving the Samples
08.11.10
View of Shannon Walker as she works to replace a dewar tray filled with samples Tracy Caldwell-Dyson pulls out a dewar tray to fill with samples in the Minus Eighty Laboratory Freezer for ISS. Image credit: NASA
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People who lived through extended power outages know that one of the first concerns is the food in the freezer. Short of eating all the ice cream you can, there is little to do to save perishable items. The International Space Station (ISS) experienced a similar power outage on orbit this week. Only ISS freezers hold science instead of food.

On Saturday, July 31, an ISS system pump failed due to an electrical current spike, shutting down half the ISS cooling system. The crew’s first concern was ensuring a safe and stable environment. Saving the science onboard was a follow-up goal, as the pump failure also impaired the Low Temperature Loop (LTL) in the Japanese Experiment Module (JEM). This meant the ISS crew had to shut down one of the onboard science freezers, the Minus Eighty-Degree Laboratory Freezer for ISS (MELFI).

The ISS perishable experiment samples in danger of thawing included:
  • Nutrition: Studies changes in human physiology during long-term space flight.
  • HydroTropi: Examines a cucumber model plant and changes in root structure and direction of growth due to gravity and other stimuli.
  • SOLO: Studies the mechanisms of fluid and salt retention in the body during space flight.
The ISS crew and NASA Cold Stowage team worked together to save the samples, preventing the loss of scientific knowledge and international investment. John Bartlett, resident Marshall Space Flight Center (MSFC) Payload Operations Director, was on consol in MSFC at the time of the transfers and commented, “Two MELFIs operating on orbit has always been a contingency plan for a failed unit on board.” MELFI 2 was not impacted, as it resides in the U.S. Laboratory and not JEM, so the ground team decided to relocate MELFI 1 samples to MELFI 2.

Instructions to locate and transfer the science in MELFI 1 were sent to the POIC, who called the instructions up to the ISS crew. Mr. Bartlett commended the effort, "I was extremely pleased with the quick response by the MELFI/COLD Team... for them to provide such a well structured, two phased retrieval and stow plan in that short of a time was outstanding!"

The crew performed the transfer in two stages. They used the Double Coldbag (DCB) and two -32 Degrees Celcius Icepac Belts for deep frozen samples. The crew then used a coldbag with +4 Degrees Celcius Ice Bricks to transfer the remaining frozen samples to MELFI 2.

Thanks to the quick actions and teamwork between the ISS crew and ground support, all samples now safely reside in MELFI 2. The crew may not have been working with ice cream in their freezers, but they certainly deserve a celebratory ice cream social with their teammates when they return home to Earth!
by Jessica Nimon
NASA's Johnson Space Center