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SpaceX’s CRS-21 Cargo Dragon undocks and heads for splashdown, wrapping up a 36-day mission

A Crew Dragon spacecraft loiters near the ISS. Crew and Cargo Dragon 2 are very similar in appearance – with Cargo Dragon only missing two fins and abort motors. Credit: NASA

JAN. 12, 2021–At 9:05 a.m. Eastern this morning, SpaceX’s CRS-21 Cargo Dragon successfully undocked from the International Space Station’s IDA-3 port on the Harmony module, completing the first undocking of a U.S. commercial cargo craft from the station (previous missions berthed), and completing ISS operations for SpaceX’s first Cargo Dragon 2 flight and first CRS-2 flight.

The successful undocking follows a confusing, canceled attempt yesterday (for undocking and splashdown) that was canceled due to weather with just two minutes to go until final undocking operations began. Today’s undocking resulted in the splashdown being pushed back even further, with Dragon coasting 35 hours until final splashdown off the coast of Tampa, FL, which is scheduled for tomorrow at 8:27 p.m. Eastern (Jan. 14, 01:27 UTC).

CRS-21, aside from resupplying the station with food and water, brought up and is bringing down several scientific experiments on the ISS. Cargo Dragon 2 is significantly friendlier to science payloads – containing double the powered locker capability of previous capsules, and capable of splashing down much closer to Kennedy Space Center, with science experiments returning to researchers within four to nine hours at the minimum, reducing the impact of non-microgravity environments on sensitive experiments. Dragon 2 is currently the only vehicle with such capability until Sierra Nevada Corporation’s Dream Chaser, a vertical-launch, horizontal-landing winged spacecraft, comes online most likely early next year.

inside the Dragon spacecraft, filled with cargo
An interior view of the Dragon spacecraft for CRS-21, as experiments and supplies are loaded. Credit: SpaceX

There are five major experiments coming home aboard CRS-21. They are:

  • The Bacterial Adhesion and Corrosion experiment, which identifies bacterial genes used during biofilm growth, along with determining whether these films can corrode stainless steel and whether silver-based disinfectants work on these biofilms. NASA claims that “this investigation could provide insight into better ways to control and remove resistant biofilms, contributing to the success of future long-duration spaceflights.”
  • The Rodent Research-23 experiment, which is returning live mice. The experiment “studies the function of arteries, veins, and lymphatic structures in the eye and changes in the retina before and after spaceflight,” with the end goal being to clarify whether these changes impair visual function.
  • Fiber Optic Production, an experiment aiming to return experimental fiber-optics created in microgravity. These fibers, composed of zirconium, barium, lanthanum, sodium, and aluminum, should “exhibit far superior qualities to those made on Earth,” due to gravity not affecting the process.
  • Cardinal Heart, which studies how changes in gravity affect heart (cardiovascular) cells at the cellular and tissue level using 3D engineered heart tissues, which is a type of tissue chip. According to NASA, “results could provide new understanding of heart problems on Earth, identify new treatments, and support development of screening measures to predict cardiovascular risk prior to spaceflight.”
  • Space Organogenesis, a JAXA experiment that aims to demonstrate the growth of 3D organ buds from human stem cells in order to analyze “changes in gene expression.” NASA claims that the results of the experiment could demonstrate the advantages of microgravity for state-of-the-art developments in regenerative medicine, and may contribute to the technologies needed to create artificial organs.

All of these experiments will heavily benefit from the fast return time for Dragon 2, along with the expanded cargo. Dragon 2’s capability of supporting 12 powered lockers, double that of the previous, along with being considerably more organized, allows for much more science to return. NASA Kennedy’s Research Integration Office utilization flight lead Mary Walsh commented on the matter, saying that “the old capsule was like a cream filled doughnut. You packed everything around the walls, and then in the middle we put a big giant stack of bags. This upgraded cargo Dragon is more like a three-story house. You put stuff in the basement, then you pack that second story, then you go upstairs and pack the third story. So it’s really different from a design perspective.”

As for the fast turnaround times, deputy chief scientist for the ISS program at NASA Johnson, Jennifer Buchli, stated that “This allows us to do different types of science. In the past if you wanted to watch an organism readapt to gravity, the best case was by the time you got it back to the lab from splashdown, you were getting data within 18 hours. However, you start to see gravity readaptation responses within organisms within 13 hours. This quicker return of just a few hours opens up a whole new area of science.”

CRS-21 lifted off from Launch Complex 39A at Cape Canaveral, Florida, on December 6, 2020, arriving at the ISS just 24 hours later and achieving the first autonomous docking of a U.S. commercial cargo resupply spacecraft. Dragon delivered more than 6,400 pounds of hardware, science, and crew supplies. The capsule is scheduled to splash down just over a day from now, at 8:27 p.m. EST, tomorrow. The splashdown will not be broadcast.

For more updates on the CRS-21 end of mission, follow NASA’s official ISS accounts at (@Space_Station) and (@ISS_Research).

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