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NASA Cell Culture Unit and NASA Contained Sample Handling and Analysis System

NASA's ISS Cell Culture Unit (CCU) is one of several Space Station Biological Research Program habitats intended to provide unprecedented access and capabilities for long duration life science experiments on the International Space Station.  It will be capable of providing a controlled environment for the study of many different types of specimens, including animal, microbial or plant cells, aquatic specimens, and tissue aggregates.  The unit was designed to be operated manually, remotely (ground controlled), or autonomously.  It is designed to be delivered to ISS and returned to earth by the Space Shuttle.  Specimens may be examined during the mission remotely via the video microscopy subsystem, by crewmembers using the Life Sciences Glovebox, or post-mission on Earth.  The facility provides scientists previously impossible opportunities to determine the role of gravity in the life cycle of living organisms, and to understand how cellular organisms and cultures adapt to microgravity over multiple generations.
CCU consists of:

• the Cell Specimen Environment Assembly, which holds up to 18 Cell Specimen Chambers (CSC’s), 3 ml to 30 ml capacity, and provides recirculation of media, additive delivery, and heat and gas exchange for all CSC’s individually;
• the Automated Sampling Module, which permits up to 60 samples to be drawn (or injected) and stored under preprogrammed or ground control;
• the Electronics Assembly, which contains all computer and signal conditioning;
• the Video Microscopy Subsystem, which provides 40x and 200x optical magnification views of the specimen cultures to the crew or video downlink to scientists on the ground;
• the Structural Containment Assembly, which supports all the other assemblies and provides interface mounting with the Shuttle and ISS host systems.

CCU provides a wide range of independently controlled environmental parameters for each CSC loop, for example, media flow rate control ranging from 0.5 to 10 ml/min, pH control from 3.5 to 8.5, etc.  Precisely controlled additive and fixative delivery and culture sampling are likewise independently executed for each CSC loop.

The science evaluation hardware has undergone extensive testing at the Ames Research Center and in Payload Systems’ laboratory; hand-held versions of CCU single-loop prototypes are being evaluated and are supporting research by scientists at Payload Systems, MIT, NASA Ames Research Center, and universities around the USA.  Demonstrated features of the CCU design include a minimal shear, gentle perfusion suspension environment and optimal gas exchange.

SEC’s role in the development of CCU was that of structural design and analysis to meet the stringent loading conditions experienced during take-off, landing and emergency landing while being transported on the Space Shuttle.  The system design had to be mass optimized, meaning that the lightest structure possible had to be developed to be able to perform reliably and safely while being able to carry all of the loads defined by the NASA requirements within the specified performance parameters.

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	CCU Hardware CAD model, designed to fit in a standard Space Shuttle double locker.
	Internal view of CCU design showing (from top to bottom) the fluid handling system, automated sampling module, and cell chamber module as well as the front panel.
	CCU CAD model showing cell chambers on turntable and gas exchangers.
	Cutaway finite element model of the CCU assembly.
	Detail of Finite Element Model of CCU internal structure showing perfusion loop components.
	Results of static analysis for one case of take-off loading conditions.
	Result of modal analysis – natural structural vibration mode for CCU assembly.

NASA’s recent policy changes have resulted in a modification of its project portfolio, which has put the CCU on hold.  The value of the technology developed is, nevertheless, being leveraged in the development of a Contained Sample Handling and Analysis System, intended to receive, handle, store and analyze samples of materials that will eventually be brought back from Mars.

Payload Systems is developing a breadboard prototype of the Controlled Sample Handling and Analysis System (CSHAS), which will form part of the Sample Receiving Facility (SRF) that will be established to accept Martian atmosphere, regolith, and rock cores to be brought to Earth by the Mars Sample Return mission.  The goal of the CSHAS project is to adapt relevant Cell Culture Unit flight system technologies into a system for use on Earth to perform analysis, testing, preparation and other functions in support of defined Mars returned sample handling and analysis protocols.  Our initial CSHAS proposal focused on the development of technology for the biohazard testing and life detection functions of the SRF, but it soon became evident that the overall system architecture had to be considered to ensure that the development was appropriately directed.  Since a set of requirements or system architecture for the SRF did not exist, we began by interpreting the “NASA Draft Test Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth” (document NASA/CP-2002-211842), and extracted a first set of requirements defining the capabilities the overall system would be expected to have and how the biohazard testing and life detection functions would fit into it.

By combining our interpretation of the draft protocol with the results of the feasibility studies conducted previously by others, we were able to conceptualize a system architecture based on modularity principles.  The system modules were defined in accordance with the experimental requirements envisaged in the draft protocol.  The system is based on the same principles used in the semiconductor and pharmaceutical industries, where a materials handling and transport system moves materials and presents them to modules for treatment through a standard set of interfaces.
In the system diagram the modules shown in green comprise the CSHAS.  The technology required to make these work will be developed by creating them anew or transitioning them from CCU technology.  The module shown in dark green, the Materials Transport Module (MTM), is responsible for the movement, management and handling of samples throughout the system.  The MTM will transport materials in standard pods and present them to the modules in the system through standard interfaces, while keeping records of the treatment history and test results of each sample.

To date, we have interpreted the draft protocol and derived an initial set of functional requirements for the CSHAS to define its role in the Mars returned sample handling protocols.  In the context of this role, the applicability of the various CCU technologies has been evaluated and an assessment of feasibility conducted, resulting in a mapping between CCU’s capabilities and CSHAS’s requirements that highlighted the modifications that will have to be made to those elements of CCU that can be translated to CSHAS, as well as indicated those elements that will have to be newly developed, including the Materials Transport Module.  The next tasks to be completed include the modification and design of system elements and ultimately the construction of a breadboard prototype to showcase the concepts.

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	Role of CSHAS within the SRF
	CAD model of modules making up the CSHAS system.
	Envisaged implementation of CSHAS and the Standard Module Interface within the larger SRF.