Appendixes



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 51
Future Biotechnology Research on the International Space Station Appendixes

OCR for page 51
Future Biotechnology Research on the International Space Station This page in the original is blank.

OCR for page 51
Future Biotechnology Research on the International Space Station A Hardware Available or in Development and Schedule for Biotechnology Research on the International Space Station Research equipment on the ISS will be housed in racks, as it was on the space shuttle. For the ISS, there are two kinds of racks: EXPRESS (Expedite the Processing of Experiments to Space Station) racks and ISPR (International Standard Payload Rack). ISPRs are the basic housing within the various modules (U.S., Japanese, Russian, etc.) that make up the ISS. ISPRs can then be fitted with specialized racks designed to support specific projects or research areas; the planned Biotechnology Facility (BTF) is one such rack. Alternatively, the EXPRESS racks, which are generic experiment support structures, can be fitted into the ISPR. The EXPRESS rack has subsystems for providing experiments with necessary resources such as power, water, vacuum, and gases. The standard EXPRESS rack holds eight middeck locker equivalents (MLEs) and two drawers (for storage). MLEs are the standard unit for hardware volume on the space shuttle and the ISS, and even within customized racks, such as the BTF, experimental hardware will still consist of modular MLE units. Each MLE is 20 by 16 by 11 in., and the modular equipment that fits in the MLE can weigh approximately 60 to 70 lb. The racks are located within the cylindrical modules that make up the ISS; the hardware described below under development by NASA is all currently scheduled to be placed in the Japanese Experiment Module. HARDWARE FOR PROTEIN CRYSTAL GROWTH IN SPACE Basic Apparatus to House Protein Crystal Growth Hardware Thermal Enclosure System (TES) and Single Locker Thermal Enclosure System (STES). The TES (which takes up two MLEs) and the STES (which takes up one MLE) are refrigeration and incubation modules whose internal volume temperature can be controlled to any set temperature between 4°C and 40°C. The stability of the set temperature is ±0.5°C for the STES and ±0.2°C for the TES. The thermal control is accomplished by the conduction of heat in or out of the internal enclosure through a side wall. Science hardware for biotechnology investigations can be flown inside the TES or the STES, and both systems were used to transport and house space crystallization devices during previous spaceflights. Science hardware currently flown within the TES/STES includes the DCAM, PCAM, VDAs, OPCGA, and DCPCG (see below for descriptions), as well as any new experiments requiring thermal control. Biotechnology Ambient Generic (BAG). The BAG terminology is used to describe any flight of DCAM, PCAM, or VDA-2 hardware as stowage items subject to ambient Orbiter or ISS conditions rather than the thermally controlled environment of a TES or STES. The functionality of the DCAM, PCAM, and VDA-2 hardware is identical to its functionality when flown in an enclosure. However, the number of DCAM trays, PCAM cylinders, or VDA-2 trays flown may vary owing to differences in the ambient stowage volume. A temperature data logger is flown in conjunction with any BAG payload.

OCR for page 51
Future Biotechnology Research on the International Space Station Protein Crystal Growth Hardware Protein Crystallization Apparatus for Microgravity (PCAM). The PCAM is a cylinder with a series of nine Lexan trays positioned between interleaving actuator plates. Turning the actuator knob several revolutions to a fixed stop activates or deactivates all of the Lexan trays simultaneously. Each of the trays contains seven vapor-equilibrium chambers. In the center of each chamber is a pedestal with a depression on top that can contain up to 40 µl of premixed protein sample solution and precipitate solution. The pedestal is surrounded by a reservoir of absorbent material. The protein solution is isolated from the reservoir prior to activation and after deactivation by an elastomer. Each tray is similar to a ChrysChem apparatus, and PCAM operation is based on the principle of vapor diffusion. The PCAM allows rapid refurbishment of the hardware and experiments in the event of launch scrub turnarounds. Operations require a minimum of crew involvement and skill, and it can be operated as handheld or adapted for automation. The PCAM's disposable interface allows individual investigators to take crystals undisturbed to their respective labs for postflight analysis. The EcoRI-DNA crystals were obtained using this device. Each PCAM cylinder contains 63 individual experiments, and up to six PCAM cylinders are flown in an STES for a total of 378 chambers per MLE. PCAM was developed at New Century Pharmaceuticals (Carter et al., 1999b). Currently, work is under way on an upgrade for PCAM. Planned improvements include an increased number of samples per volume (to approximately 960 per MLE) and automated activation and deactivation of the crystallization phase. The upgraded hardware is in the early definition phase. Diffusion-Controlled Protein Crystallization Apparatus for Microgravity (DCAM). DCAM is composed of a central housing with two reservoir chambers separated by an exchangeable gel plug of varying proportions. Each chamber is sealed by an end cap. One chamber includes a standard proportional microdialysis button, which contains the protein solution. The other reservoir chamber houses the precipitating agent, which, over time, diffuses through the gel plug. The DCAM is essentially activated when it is loaded on the ground, so no crew resources are required for activation or deactivation. DCAM operation is based on the principle of liquid-liquid diffusion. DCAM was designed for long-duration protein crystallization on the Mir space station, and the equilibration profiles are extremely stable and reliable over several months. Nucleosome core particle crystals, grown to 4 mm, were crystallized in DCAM during a 4-month mission on Mir. DCAMs are flown in tray assemblies with 27 DCAMs per tray and up to three trays per STES. This results in a total of 81 samples per MLE. DCAM was developed at New Century Pharmaceuticals (Carter et al., 1999a). Currently, work is under way on an upgrade for DCAM. Planned improvements include a larger number of samples per volume (to approximately 200 per MLE) and more crystallization options: vapor diffusion, bulk, and dialysis. The upgraded hardware is in the early definition phase. Enhanced Gaseous Nitrogen Dewar (EGN). Because the EGN is an ambient stowage experiment, it is not housed in the thermally controlled environment of an STES. The hardware consists of a liquid nitrogen dewar and aluminum insert tube, sealed Tygon capillary sample tubes, sample bundles, and an electronic temperature monitoring system. The dewar vessel consists of two flasks with the inner space evacuated to create a thermal vacuum insulation. The inner flask contains a calcium silicate absorbent, at the center of which is a cylindrical container. The dewar insert, sample bundles, and protein sample batches are placed inside this cylinder. Liquid nitrogen is poured into the inner flask and is absorbed by the calcium silicate. Approximately 7 days after the EGN and its samples have been assembled, all the liquid nitrogen boils off, the sample proteins thaw, and protein crystal growth commences and continues inside the individual Tygon tubes for the duration of the mission. No activation or deactivation by the crew is required, and the samples are returned to the investigator immediately after landing. The EGN is the size of an MLE, and the insert that contains the sample material is 11.4 inches long by 2.95 inches in diameter. The following numbers of samples per MLE are possible, assuming that all samples are of the same size:

OCR for page 51
Future Biotechnology Research on the International Space Station Sample Size (µl) Number of Samples Source of Estimate 10-20 10,000 Calculation 170 1,000 Calculation 600 150-180 Actual flight data The EGN is based on previous flight experience with a similar piece of hardware known as the gaseous nitrogen dewar. Both were developed at the University of California at Irvine, and the EGN is in fabrication for flight in 2000. Second-Generation Vapor Diffusion Apparatus (VDA-2). The VDA-2 is based on a triple-barreled syringe system designed to mix protein solutions and precipitants in microgravity. Each barrel of syringe can be loaded with up to 30 µl of solution. The experiment is initiated by deployment of the solutions onto the tips of the syringe assemblies to form drops and deactivated by moving the drops back into the syringes. Absorbent reservoir material containing approximately 1 ml of precipitant solution surrounds the drop in each chamber. Mixing of the drops is achieved by moving the droplet solutions into and out of the third syringe barrel. The VDA-2 is activated on orbit by a crew member, who operates a mechanism that injects and mixes solutions in all growth chambers simultaneously; the crew member then deactivates the entire VDA-2 before leaving orbit. Upon deactivation, the drop containing the crystal is drawn back into the syringe and the end of the syringe is plugged for subsequent recovery and delivery to the investigator. The advantage of using VDA-2 is that the solutions are mixed in microgravity and the starting point of the drop need not be in the soluble range. Up to four VDA-2 trays may be flown in an STES, for a total of 80 experiments per MLE. A commercial version of this system includes more samples (128) but does not allow for photography in orbit. VDA-2 was developed at the University of Alabama at Birmingham (DeLucas et al., 1989). Protein Crystallization Facility. This equipment is used for batch processing of proteins whose solubility depends on temperature. Sample bottles in this device range from 50 to 500 ml, and four sample bottles can be accommodated in one STES. A temperature gradient along the linear axis of the cylinder can be manipulated by controlling the temperature of one end. Another version of this device includes laser light scattering to detect nucleation so that the temperature can be controlled manually. This version can contain two sample bottles. The hardware was developed at the University of Alabama at Birmingham. Devices in Fabrication for in Situ Observation of Crystallization on Orbit Interferometer for Protein Crystal Growth. This system employs a Michleson-Morley phase-shift interferometer to produce images showing density changes in solution as a protein crystal forms. The system comprises three major systems—an interferometer, six fluid assemblies with test cells, and a flight data system. The crystal growth cells are made of optical-grade glass: cells are 1 mm thick and contain 250 µl of solution. Each fluid handling system is a self-contained plastic assembly enclosing two pairs of 4-ml supply syringes (one containing protein solution and one containing precipitant solution), a waste receptacle, and a test cell, as well as mechanisms to inject fluids and to position the test cell. The crew operates the fluid system with a hand crank that depresses the syringe pistons. Six of these assemblies now exist, but any number can be reproduced. The flight data system includes a 486-based laptop computer and has video recording capability. It was originally designed to perform an experiment in the Mir glovebox and was developed at the University of California at Irvine. Observable Protein Crystal Growth Apparatus (OPCGA). This equipment is designed to observe the formation of nutrient concentration depletion zones in the vicinity of growing crystals using a fused optics, phase shift Mach-Zehnder interferometer. The crystals are formed in 96 growth cells, each of which represents an individual liquid-

OCR for page 51
Future Biotechnology Research on the International Space Station liquid diffusion crystallization experiment. The cells are mounted on rails in sets of four surrounding a central shaft carrying opposing optical systems, each of which consists of a phase shift interferometer with a field of view 4 mm by 4 mm. The optical systems will resolve an index of refraction of 1.7 × 10−5through a 1 mm optical path. The resolution will be 15 µ. A black and white camera to make a video of the growing crystal is also available. The optical system will also contain a polarization microscope with a 4 mm by 4 mm field of view and a 1:1 magnification. The polarization microscope uses a diode for backlighting the growth cell. A color camera is included for time-lapse video. A VCR will record the video microscopy data. It is hoped that this device will produce data that can be used to compare the properties and kinetics of formation of concentration gradients in mother liquids for protein crystal growth in microgravity and in conventional laboratory environments. The OPCGA contains 96 growth cells flown within a TES, resulting in 48 samples per MLE. The OPCGA was developed at the University of California at Irvine (McPherson et al., 1999) and is in fabrication for flight in 2002. Dynamically Controlled Protein Crystal Growth (DCPCG). The DCPCG system uses controlled dehydration or temperature as function of time to grow crystals in orbit. There are three components of the DCPCG: a V-locker, a T-locker, and a C-locker. In the V-locker, a closed loop dry nitrogen gas system controls the rate of water evaporation from protein solutions held at a constant temperature of 22±0.5°C. In the T-locker, thermal fluctuation induces supersaturation of sample solutions and subsequent crystallization. The T-locker provides temperature control to sample growth chambers in the range of 4°C to 50°C, with a temperature control ramp rate of 1.0°C per min. at the low and high limits of the temperature range. In both the V- and T-lockers, there are at least 30 sample chambers, 10 of which are “control” chambers that interface with a laser light scattering system to detect sample aggregation. Each sample chamber will hold 40 to 200 µl of sample solution. A video subsystem is incorporated as an integral link for near-real-time experiment evaluation. Both the V- and T-lockers interface with the C-locker to provide external communications, video capture, and data storage. A version of this system will soon be available commercially for growing crystals in laboratories on Earth. The DCPCG contains at least 60 sample chambers and occupies a total of three MLEs, resulting in at least 20 samples per MLE. The DCPCG was developed at the University of Alabama at Birmingham and is in fabrication for flight in 2000. Devices in Early Definition Phase for in Situ Observation of Crystallization on Orbit Microscope Laser Light Scattering Apparatus. This device is being designed to permit scientists to determine the size and relative concentration of protein molecules attaching onto a crystal's surface. To do so, the device will use multi-angle dynamic laser light scattering and fluorescence recovery after photobleaching diagnostic techniques. Although the number of cells to be examined has not yet been determined, temperature control of each cell is postulated to be 0.1°C between 0° and 60°C. Cooling of 0.6°C per hour is anticipated. This hardware is being developed at the Naval Research Laboratory and is in the early definition phase. Glovebox-size Interferometer. This glovebox-sized instrument will be specifically designed to study improvement of crystal quality through imposed changes in the transport conditions in the solution. Six cells with individual temperature controls to 0.01°C will be used. The cells will be capable of fixed position crystal seeding, and an automatic phase-shifting interferometer (operated from the ground) will be available for in situ surface characterization for each cell. In addition, a high-resolution digital camera will image the crystal. The intent is to resolve and study single growth steps and follow the details of step bunching. This device is being developed at University of Alabama at Huntsville and is in the early definition phase. X-ray Crystallography Facility This facility has been designed and is in fabrication at the Center for Macromolecular Crystallography at the University of Alabama at Birmingham. There are several components; two full racks (16 MLEs) are currently reserved for this facility, which is separate from the planned BTF on the ISS.

OCR for page 51
Future Biotechnology Research on the International Space Station High-Density Protein Crystal Growth (HDPCG) Unit. This equipment contains 168 individually molded six-packs, each of which has six wells in which vapor diffusion experiments can be performed. Each well of the six-pack can hold 49 µl of protein solution and 500 µl of reservoir solution. The six-packs can be removed from the HDPCG for observation in the visualization unit (see below) or sampling in the CPPI (see below). In the current configuration, the HDPCG cannot be reloaded on orbit. Future plans call for adding on-orbit reloading capabilities, as well as the option of running liquid-liquid diffusion experiments. The unit occupies one MLE and fits 1,008 samples in that volume. Video Command and Monitoring System. This unit provides an imaging system of still pictures with 12× magnification (not actual video) for samples in the six-packs of the HDPCG. The crystallization results can be visualized either during or after a period of crystal growth, and the resulting images may be used to select appropriate candidates for mounting or freezing in the CPPI (see below). This unit occupies one MLE and will be located near the HDPCG. Crystal Preparation Prime Item (CPPI). This unit is designed to remove crystals from the HDPCG six-packs and mount them on hair loops for cryopreservation or hair loops inside a capillary, unfrozen. The temperature inside the CPPI can be controlled and maintained between +4°C and +30°C. The robotic arm used for all manipulations was developed under a cooperative agreement between MicroDexterity Systems and NASA's Jet Propulsion Laboratory and was originally designed with eye surgery in mind. The robot, referred to as the OM3™, has six degrees of freedom within a work volume of 400 cc. It has a resolution of 10 µ and repeatability of 25 µ in terms of positioning. At any given time, the CPPI has room for two cartridges, each holding two HDPCG six-packs, 12 hair loops or capillaries, and 9 pipette tips. Using these tools, the robot can remove crystals from a well and mount a crystal in about 5 minutes. In the future, this process will be speeded up to about 1.5 minutes, and the actual exposure of liquids to the controlled environment will be about 30 seconds. After the loop mount of the crystal, the loop and crystal are presented to a cold volume and pushed rapidly through the −183°C nitrogen gas to simulate the flow of cold nitrogen gas from a cold stream. Then, the frozen crystal is transferred to an insulated thermal mass for transfer to the X-ray diffraction system or stored in the 24-position storage freezer, also located in the CPPI. Capillary mounts bypass the freezer. Crystals stored in the storage freezer may be transferred later to the MELFI (see below). X-ray Diffraction System. The diffraction system is divided into three parts: the goniometer, the detector, and the X-ray generator. The goniometer is a three-circle type with χ fixed at 45°. The detector is currently configured to move such that crystal to detector distance is between 60 and 200 mm and the swing angle (2θ) is ±45°. The current SMART 2K CCD detector has a 135-mm diameter imaging area with a 1.9:1 fiber optic taper for reducing the image from the phosphor to the CCD. The pixel to pixel resolution is 48 µ unbinned in the 2048 mode. The highest resolution data the detector could collect at 80 mm detector distance and swung to 45° would be 1.1 Å. The Bruker rule of thumb for low-divergence X-ray beams is that the longest unit cell is equal to the detector distance divided by 0.6. This implies a 133 Å unit cell at an 80 mm detector distance and a 333 Å unit cell at a 200 mm detector distance. Plans for future improvements include using a 6K single chip CCD detector system currently under development by Bruker and redesigning the goniostat to allow the crystal to detector distance to expand to 300 mm (which would enable the system to achieve a 500 Å unit cell). The X-ray source is a Microsource system, manufactured by Bede Scientific. It is designed to be a low-power, intense X-ray source (Arndt et al., 1990, 1998a, b). The Microsource is powered at 40 kV and 0.6 mAmps or 24 W of power. It currently is about 1/3 to 1/2 as intense as the Yale/MSC type mirrors on a 5 kW Rigaku rotating anode generator. This source is stationary following fine adjustment. The X-ray diffraction system can handle crystals between 0.1 mm and about 2 mm, and the crystal can be translated ±5 mm in the x, y, and z directions and can be rotated about φ and Ω a full 360°. Cryocooler System. This system employs a molecular sieve system to separate nitrogen from the air within the space station for cooling using a Stirling type cooler (capable of a 25-W heat lift at −183°C). Flow rates are currently about 3.5 to 4 liters per minute at the crystal, for both the cold and outer flows. Temperatures at the

OCR for page 51
Future Biotechnology Research on the International Space Station crystal position have been measured at −183°C. A new nozzle developed by Hakon Hope, which uses a heater element to produce a warm outer flow from the inner cold flow, is being tested. Experiment Control. The status and operation of the various components of the XCF (the HDPCG, the visualization unit, the CPPI, and the X-ray diffraction system) on the ISS can be monitored on the ground through a Payload Operations Control Center. Current plans call for these centralized control capabilities to be situated at the Center for Macromolecular Crystallography at the University of Alabama at Birmingham. Relevant Support Equipment The apparatus listed here is not a part of the BTF or the XCF but is scheduled to be located elsewhere on the ISS. Like crew time for experimental activities, use of support equipment will be shared by many research projects on the ISS. Minus Eighty Degree Laboratory Freezer for ISS (MELFI). This unit will provide cooling down and storage for reagents, samples, and perishable materials in four dewars with independently selectable temperatures of −80°C, −26°C, and +4°C during on-orbit ISS operations. It will also be used to transport samples to and from the ISS in a low-temperature controlled environment. The total capacity of MELFI is 300 liters; the system occupies a full rack. MELFI is currently in development by the European Space Agency; delivery is due late in 2000. Cryofreezer System. This unit is designed to provide ultrarapid freezing and storage capacity for 3 liters of research specimens at −183°C. It is also under development by the European Space Agency for delivery in 2004. Middeck Glovebox. This unit provides an enclosed space for experiment manipulation and observation for work in the several disciplines to be studied on ISS, including protein crystallization, fluid physics, combustion, and material science. Various modes of air circulation and pressurization are possible. Multipurpose filters are used to remove particles, liquids, and reaction gases from the circulated air. The glovebox, which occupies two MLEs, has a working volume of 35 liters and a door opening of 20.3 by 19.4 cm for sample and hardware transfer. Up to 60 W of 24, 12, and 5 V of direct current power is available for instruments to be used inside the glovebox. HARDWARE FOR CELL SCIENCE IN SPACE Cell and Tissue Culture Hardware in Development for ISS Biotechnology Temperature Controller (BTC). This unit is designed to provide refrigeration on-orbit as well as the capability of preserving and incubating multiple cell cultures simultaneously. The cell culture bags are transparent to allow visualization of the samples by light microscopy. While the BTC does not have the capability of automated medium exchange, the cultures can be fed using special needleless “penetration” connectors on the bags that provide for multiple aseptic connections. The BTC can be used as one large chamber or reconfigured into 2, 3, or 4 chambers with separate environmental controls (temperatures can range from 4°C to 40°C in 1°C increments). The unit occupies one MLE and can contain up to 120 7-ml culture bags, which are Teflon sample modules containing media and cells. This unit is in development at NASA, and its first flight is scheduled for late 2001. The BTC, with its combined refrigeration and incubation capabilities, was designed based on lessons learned from NASA's Biotechnology Specimen Temperature Controller (BSTC) and Biotechnology Refrigerator (BTR), which have been flown both for short-term space shuttle trips and for long-term experiments on Mir. Cell Culture Unit (CCU). This unit is a modular cassette-style bioreactor that can accommodate multiple cell culture chambers (see Figure 2.2). The CCU provides control of temperature (between 4°C and 39°C) and pH (between 3.5 and 8.5) and allows for continual feeding and waste medium harvest from perfused stationary

OCR for page 51
Future Biotechnology Research on the International Space Station cultures (Searby et al., 1998). Mixing occurs via medium recirculation. The CCU also provides automated sample collection and injection and high-quality video microscopy. Individual perfused culture chambers can be replaced on orbit. Specimens are loaded in chambers on the ground; inoculation and subculture can occur in space. Bubbles must be manually prevented from accumulating in the chambers. The CCU can accommodate from 8 large (30 ml) to 24 small (3 ml) samples and the associated support and observation equipment within 2.5 MLEs. This piece of hardware is under development by Payload Systems, Inc., in conjunction with the Massachusetts Institute of Technology for the Life Sciences Division of NASA and is scheduled for its first flight in 2002. The cell science program within the Microgravity Research Division is funding early development work on the Perfused Stationary Culture System, which is supposed to be a small-volume (5 to 50 ml), multivessel system for on-orbit cell culture and tissue engineering investigations. This system is in the early stages of development, has planned goals and capabilities similar to those of the CCU, and may not be developed if the CCU proves to be successful. Rotating-Wall Perfused System (RWPS). This unit houses a single 125-ml rotating-wall perfused vessel in a controlled environment along with associated equipment for medium infusion/perfusion, temperature control, gas exchange, and independent rotation. Unlike ground-based rotating-wall bioreactors, in which laminar flow is set up to randomize the force vectors and to minimize the shear stress, the space-based vessels have rotating walls in order to produce Couette flow, which augments mass transport. Observation and video recording are possible through a large window in the front of the unit. The RWPS can be inoculated on the ground just before launch or on orbit, but once the RWPS is powered and the experiment initiated, it remains powered throughout the increment until landing. Cell and media samples can be removed on orbit through sample ports located on the side and front panels. The RWPS occupies one MLE and supports one cell or tissue sample. It is scheduled for its first flight late in 2000. The RWPS is an updated version of NASA's Engineering Development Unit (EDU), which has housed rotating-wall vessel experiments on the space shuttle and on Mir (see Figure 2.3). Cell Science Support Equipment Sensor and Control Technologies. NASA sensor research by on-site contractors focuses on fluid sensors that will enable physiological control of the cell/tissue culture media environment. Sensors for pH and glucose, as well as a pH control system, are at advanced stages of development. In contrast, sensors to measure oxygen and carbon dioxide concentrations are in the early stages of development. Sensors will be installed within cell and tissue culture hardware in order to assist in data collection and remote operation. Gas Supply Module. This unit is designed to provide nitrogen, carbon dioxide, and other gases to experiments in the RWPS and the BTC. A completed version of this equipment has been flown on Mir, and the revised version, which is 0.5 MLEs, is scheduled for its first flight in 2002. Experiment Control System. This unit is intended to serve as the standarized control system for biotechnology investigations. It must be able to interface with experiment-specific hardware (e.g., the RWPS) as well as general support systems (e.g. the Gas Supply Module). Tasks include data acquisition and archiving, experiment control, and communication with the ground and the rack systems (e.g., power supply). The Experiment Control System occupies half of an MLE. Hydrodynamic Focusing Bioreactor (HFB). This bioreactor is a variation on the standard rotating-wall vessel central to the EDU and the planned RWPS. The HFB was designed to control the directional movement and removal of air bubbles from the bioreactor vessel on orbit without degrading the low-shear culture environment or the tissue assemblies. The HFB produces a low-shear fluid environment, while a variable hydrofocusing force is used to control the movement, location, and removal of suspended cells, tissue aggregates, and air bubbles from the reactor. A space version of this hardware is currently in the design and testing phase.

OCR for page 51
Future Biotechnology Research on the International Space Station General Support Equipment Relevant to Cell Science Research The apparatus listed here is not a part of the BTF but is scheduled to be located elsewhere on the ISS. Like crew time for experimental activities, use of support equipment will be shared by many research projects on the ISS. Minus Eighty Degree Laboratory Freezer for ISS (MELFI). This unit will provide cooling down and storage for reagents, samples, and perishable materials in four dewars with independently selectable temperatures of −80°C, −26°C, and +4°C during on-orbit ISS operations. It will also be used to transport samples to and from the ISS in a low-temperature controlled environment. The total capacity of MELFI is 300 liters; the system occupies a full rack. MELFI is currently in development by the European Space Agency; delivery is due late in 2000. Cryofreezer System. This unit is designed to provide ultrarapid freezing and storage capacity for 3 liters of research specimens at −183°C. It is also under development by the European Space Agency; delivery is due in 2004. Water and Air Delivery Systems. These systems are in the early stages of development. A water sterilization and filtration system is planned to allow shuttle and ISS water to be purified and used for media preparation (rehydration/dilution) for cell culture. An air purification system would allow the use of shuttle and ISS cabin air to aerate cell culture medium through a separately housed oxygenator. Such air would be enriched with up to 10% carbon dioxide. Incubator. This is a controlled environmental chamber for growing cell and tissue cultures. Its available capacity is 18.7 liters and the temperature range is 4°C to 38°C. It operates within the Life Sciences Glove Box or the Centrifuge Rotor. The glove box provides an enclosed space for experiment manipulation and observation for life sciences research on the ISS. Its volume is 500 liters, it can accommodate two habitats, and two crew members can conduct scientific procedures simultaneously. It is scheduled for launch in 2001. The Centrifuge Rotor is a 2.5-m centrifuge designed to provide a simulated gravity environment from 0.01 to 2.00 times Earth's gravity. The habitat volume available within the centrifuge is approximately 0.18 m³. Currently, the planned launch date for the centrifuge is 2004. Analytical Equipment A variety of analytical equipment is scheduled to be available on ISS. Some instruments, such as the cameras, will be easily transportable throughout the ISS; others, such as the microscopes, will be operated within the glove boxes, and still others will be located within their own modules. Current plans call for the microscopes to be linked to digital cameras. Cameras. One commercial off-the-shelf (COTS) digital still camera, two COTS film still cameras, and a COTS camcorder for the general-purpose videotaping of experiments. Dissecting Microscope. This instrument allows for microscope-aided inspection and manipulation of specimens within the confines of a glove box. Magnification range is 4 to 120×. Compound Microscope. This is a standard benchtop microscope with magnification up to 1000× and Kohler illumination to support phase-contrast microscopy for cellular and subcellular observations. It will use halogen, mercury, or xenon light sources.

OCR for page 51
Future Biotechnology Research on the International Space Station Miscellaneous Mini-Payload Integration Center (Mini-PIC). This system is a fairly portable ground-based hardware system that emulates the proposed configuration and capabilities of the BTF rack. It has been developed to enable principal investigators to develop protocols and carry out duplicate control experiments in their own labs. SCHEDULE All dates offered below are approximate and are based on the schedule provided to the Task Group by NASA in the summer of 1999. Phase I (2000 through mid-2003). Biotechnology research on the ISS occurs using instruments that already exist and were used or planned for use on the space shuttle. These instruments will be installed in EXPRESS racks in whatever laboratory modules have been completed. These preexisting pieces of hardware were not designed for long-term flight and often do not fulfill ISS requirements for configuration and resource use, but they will receive waivers to allow continuation of the science program while new hardware is developed and constructed. The performance of hardware during this phase will provide valuable input to the design and development of ISS-specific equipment. Another constraint on scientific work done at this time will be the ongoing construction of the ISS, which will limit both the time crew can be involved in research and the available transport volume on the shuttle. At this point, ISS resources, such as power, will also be limited and may not be reliable. Phase II (mid-2003 through 2005). The boundary between Phase I and II is not a distinct one. Instead, there will be a gradual transition in the type of biotechnology instrumentation flown on the ISS. Phase II instrumentation consists of modular units that have been designed specifically to be used for long-duration (several months or more) experiments on the ISS. These instruments can be expected to have fewer performance risks and to meet ISS hardware requirements. Also, new efficiencies and capabilities should have been added to the equipment. For example, exchanging various sample units within hardware was not vital on a 2-week shuttle mission but would be necessary to maximize the science return from a long-duration flight. Another difference between Phase I and Phase II is that although the ISS will still be under construction, the availability of launch volume and on-orbit resources should increase. Equipment would still be housed in EXPRESS racks, but at that point both the U.S.-provided laboratory module and the Japanese-provided module should be operating. Phase III (2005 and beyond). The transition to Phase III is sharply defined by the installation of the specialized BTF on ISS. This facility will still accept modular hardware of the type used in Phase II, but the facility will provide additional support capabilities designed specifically to enable biotechnology work on ISS. Current plans call for the BTF to provide each experimental module within it with power, gases (such as nitrogen and carbon dioxide), thermal cooling, data acquisition, storage and processing, video and image analysis, data downlink, real-time control, resource allocation, research-grade water, and vacuum exhaust for one modular unit at a time. Also, BTF will have an intelligent power distribution system to allow for efficient management of this scarce resource and to ensure that cuts in power are consistent with the constraints of each payload (i.e., power will be cut first to those payloads that are able to recover from the power outage without a sustained loss in performance). As well as using all of BTF, biotechnology experiments will also continue to operate in EXPRESS racks on ISS, when volume is available.