Development of the Bioreactor systems proposed for use in the Space Station depended on understanding the fluid dynamics of such systems in microgravity. This equipment test permitted the comparison of actual microgravity particle trajectories in the rotating vessel, with calculated trajectories, thus providing data required to improve or modify the systems.
Data was logged into the internal system memory of the apparatus. Data interpretation and evaluation was performed by the JSC Biotechnology Laboratory to determine the extent to which the objective of the test was achieved.
Test conditions/activities required:
Two preflight hardware training sessions were held to orient the crewmembers with the equipment.
The total crew time inflight was 50 minutes. As soon as possible on flight day (FD) 1, the crewmember connected a cable to orbiter power, turned on power, and recorded mission elapsed time (MET) and FD. There were four tests of 6 to 12 hours in length. The first three tests were followed by a stabilization period of no less than 2 hours. A longer stabilization period was permitted as dictated by the timeline. At the end of the stabilization periods, the crewmember changed the video tape and restarted the test. At completion of the fourth test, the video tape was removed from the camera, stowed, orbiter power cable disconnected, and MET recorded.
Crewmembers were debriefed on their experiences regarding the experiment.
The flight data verified that the optimal operating conditions were obtained by sequences 1 and 2. In sequence 1, the outer wall was rotating at 2 repetitions per minute (rpm) and the inner wall was rotating at 6 rpm. The video showed that on startup the beads were congregated at the outer wall. After about an hour, the small beads (1000 microns) were trapped by the flow field in the left half of the vessel and were well distributed from inner wall to the outer wall. The medium beads (3000 microns) were uniformly distributed in both halves of the vessel. The large beads (5000 microns) were positioned near the end caps and closer to the inner wall. In sequence 2, the rotation rate was the same as sequence 1; however, a perfusion rate of 20 ccs per minute was established. The small and medium beads were closer to the inner wall and large beads moved farther away from the end caps. This distribution showed that when particles hit the end cap, only 1000 micron particles could be moved away by the fluid circulation. The 3000 and 5000 microns particles were too heavy to be moved away by the fluid's inward circulation and stayed near the surface of the inner spin cylinder. When the perfusion loop had been turned on, the particles were brought in toward the inner wall except for the 5000 microns particles being moved outward by a stronger circulation force.
Experiment sequences with the inner cylinder rotated faster than the outer cylinder showed that the centrifugal force was too strong to be curved and all the particles moved to the outer wall eventually. Sequences with the outer cylinder rotated faster than the inner cylinder showed that they did form a circulation, but the flow field was too turbulent to achieve the quiescent state required for cell culture.
The particle trajectories from the DSO 316 data were in agreement with numerical predictions developed on a Cray super computer. There were no problems associated with the performance of the equipment during the required sequence runs. The flight experiment provided data which will help advance the Bioreactor design.
Ingram M, Techy GB, Saroufeem R, Yazan O, Narayan KS, Goodwin TJ, Spaulding GF. Three-dimensional growth patterns of various human tumor cell lines in simulated microgravity of a NASA bioreactor. In Vitro Cell Dev Biol Anim. 1997 Jun;33(6):459-66.