Radiation biodosimetry: applications for spaceflight.

The multiparametric dosimetry system that we are developing for medical radiological defense applications could be adapted for spaceflight environments. The system complements the internationally accepted personnel dosimeters and cytogenetic analysis of chromosome aberrations, considered the best means of documenting radiation doses for health records. Our system consists of a portable hematology analyzer, molecular biodosimetry using nucleic acid and antigen-based diagnostic equipment, and a dose assessment management software application. A dry-capillary tube reagent-based centrifuge blood cell counter (QBC Autoread Plus, Becton [correction of Beckon] Dickinson Bioscience) measures peripheral blood lymphocytes and monocytes, which could determine radiation dose based on the kinetics of blood cell depletion. Molecular biomarkers for ionizing radiation exposure (gene expression changes, blood proteins) can be measured in real time using such diagnostic detection technologies as miniaturized nucleic acid sequences and antigen-based biosensors, but they require validation of dose-dependent targets and development of optimized protocols and analysis systems. The Biodosimetry Assessment Tool, a software application, calculates radiation dose based on a patient's physical signs and symptoms and blood cell count analysis. It also annotates location of personnel dosimeters, displays a summary of a patient's dosimetric information to healthcare professionals, and archives the data for further use. These radiation assessment diagnostic technologies can have dual-use applications supporting general medical-related care.     

Ultracapacitors + DC-DC converters in regenerative braking system

An ultracapacitor system for an electric vehicle has been implemented. The device allows higher accelerations and decelerations of the vehicle with minimal loss of energy and minimal degradation of the main battery pack. The system uses a DC-DC power converter, which is connected between the ultracapacitor and the main battery pack. The design has been optimized in weight and size, by using water-cooled heat sinks for the power converter, and an aluminum coil with air core for the smoothing inductance. The ratings of the ultracapacitor are: nominal voltage: 300 Vdc; nominal current: 200 Adc; capacitance: 20 Farads. The amount of energy stored allows us to have 40 kW of power during 20 seconds, which is enough to accelerate the vehicle without the help of the traction batteries. The vehicle uses a brushless DC motor with a nominal power of 32 kW and a peak power of 53 kW. A control system based on a Digital Signal Processor (DSP) manipulates all the aforementioned variables and controls the Pulse Width Modulation (PWM) switching pattern of the converter transistors. The car used for the implementation of this system is a Chevrolet LUV truck.     

Initial closed operation of the CELSS Test Facility Engineering Development Unit.

As part of the NASA Advanced Life Support Flight Program, a Controlled Ecological Life Support System (CELSS) Test Facility Engineering Development Unit has been constructed and is undergoing initial operational testing at NASA Ames Research Center. The Engineering Development Unit (EDU) is a tightly closed, stringently controlled, ground-based testbed which provides a broad range of environmental conditions under which a variety of CELSS higher plant crops can be grown. Although the EDU was developed primarily to provide near-term engineering data and a realistic determination of the subsystem and system requirements necessary for the fabrication of a comparable flight unit, the EDU has also provided a means to evaluate plant crop productivity and physiology under controlled conditions. This paper describes the initial closed operational testing of the EDU, with emphasis on the hardware performance capabilities. Measured performance data during a 28-day closed operation period are compared with the specified functional requirements, and an example of inferring crop growth parameters from the test data is presented. Plans for future science and technology testing are also discussed.     

Next generation digital GPS receiver

The architecture and technology features of the next-generation (NGR) digital GPS (Global Positioning System) receiver manufactured by Collin are described. The project's objective was to develop an advanced GPS receiver chipset with high antijam capabilities. The program, initiated in 1985, has provided the technology for miniature receiver products for both unmanned and manned vehicle applications. A two-channel version of the receiver is in full-scale development for tactical missile applications. A five-channel version is being tested and evaluated as a drop-in replacement for RCVR-3A, the US Department of Defense standard high dynamic receiver. The NGR design started with the digital signal processing architecture developed for the Defense Advanced Research Project Agency (DARPA) hand-held GPS receiver. Enhancements were made to improve the antijam and signal acquisition performance. Producible, qualifiable and cost-effective silicon monolithic microwave integrated circuits and semicustom digital technologies were used to develop the core GPS chipset. A system design approach was established to permit reuse of mature and validated GPS software     

A nickel/hydrogen battery for PV systems

The nickel-hydrogen battery, developed in the early nineteen-seventies as an energy-storage subsystem for commercial communication satellites, is discussed. The advantages offered by nickel-hydrogen batteries, including long life, low maintenance and high reliability, make it very attractive for terrestrial applications such as stand-alone photovoltaic systems. The major drawback to the wider use of the nickel-hydrogen battery is its high initial cost. A 7-kWh battery has been on test since January 1988 using a flat-plate photovoltaic array for charging. The cell, battery design and test methods are briefly described, and the results of cycling and solar tests are presented. It is concluded that the battery is well suited for remote solar applications     

Atmospheric tides between 80 km and 120 km

The structure and variability of tides in the 80 – 120 km height region are reviewed. Particularly emphasised are seasonal-latitudinal variations in the vertical structure of diurnal and semidiurnal winds between 70 – 100 km as measured by meteor and partial reflection drift radars, and tidal temperatures determined by incoherent scatter radars between 100 and 140 km. Variations in tidal structures with longitude, from day to day, and during equinoctial transition periods are also addressed.     

Magnetic reconnection in solar coronal loops

Simulations of the evolution of kink modes in line-tied coronal loops are presented which demonstrate the occurrence of magnetic reconnection in the non-linear stage of the instability. In loops which do not carry a net axial current (and are confined by a potential purely axial field) the reconnection is limited to the initial current-carrying channel and no overall loss of confinement is observed. In loops which carry a net current on the other hand, reconnection progressively involves field lines at greater and greater distances from the axis and even regions where the field was initially potential, leading to a total disruption of the magnetic field topology.     

Effects of air current speed on gas exchange in plant leaves and plant canopies.

To obtain basic data on adequate air circulation to enhance plant growth in a closed plant culture system in a controlled ecological life support system (CELSS), an investigation was made of the effects of the air current speed ranging from 0.01 to 1.0 m s-1 on photosynthesis and transpiration in sweetpotato leaves and photosynthesis in tomato seedlings canopies. The gas exchange rates in leaves and canopies were determined by using a chamber method with an infrared gas analyzer. The net photosynthetic rate and the transpiration rate increased significantly as the air current speeds increased from 0.01 to 0.2 m s-1. The transpiration rate increased gradually at air current speeds ranging from 0.2 to 1.0 m s-1 while the net photosynthetic rate was almost constant at air current speeds ranging from 0.5 to 1.0 m s-1. The increase in the net photosynthetic and transpiration rates were strongly dependent on decreased boundary-layer resistances against gas diffusion. The net photosynthetic rate of the plant canopy was doubled by an increased air current speed from 0.1 to 1.0 m s-1 above the plant canopy. The results demonstrate the importance of air movement around plants for enhancing the gas exchange in the leaf, especially in plant canopies in the CELSS.