Measurements of electrical breakdown in the vicinity of a sounding rocket differentially charged to 10 kV

During the initial period of high voltage biasing of the SPEAR-3 sounding rocket payload, it was observed that electrical breakdown occurred in the gas surrounding the rocket. The breakdown occurred almost all the way to apogee of 289 km on the upleg, but did not recur on the downleg until the payload reached an altitude of 100 km. It is suggested that this behavior can be attributed to payload outgassing on the upleg leading to abnormally high gas pressure near the payload skin. Consideration of a modified Paschen discharge process with varying pressure along the discharge path was found to be consistent with the results.     

Monitoring power supply current and using a neural network routineto diagnose circuit faults

As a circuit is tested, the current drawn from a power supply can vary as different functions are invoked by the test. The current draw can be plotted against time, showing a characteristic trace for the test performed. Sensors in the ATS power supply can be used to monitor the current flow during test execution. Defective components can be classified using a Neural Network according to the pattern of variation from the “trace” of a good card. This can be performed as a background function, with the network gaining in accuracy over time. This paper discusses the Neural Network Routine for diagnosing circuit faults using monitored power supply current     

Weapons System Open Architecture - a bridge between "embedded" and "off-board"

A demonstration program is described: Weapons System Open Architecture (WSOA) - funded jointly by the Air Force Research Laboratory (AFRL), DARPA, and the Open Systems Joint Task Force (OSJTF). WSOA provides an open systems "bridge" between legacy embedded mission systems and off-board C3I sources and systems. This "bridge" is used to support Internet-like connectivity between command and attack nodes. The foundation of this bridge is the creation of a Common Object Request Broker Architecture (CORBA) layer over Link 16. In addition, application of quality of service techniques and resource management technologies will ensure the timely exchange and processing of mission critical information by both attack and command nodes in even the most time-sensitive situations.     

Enhanced space integrated GPS/INS (SIGI)

Safe, reliable, and low cost space-based navigation is being provided with embedded INS/GPS systems such as the space integrated GPS/INS (SIGI). The SIGI is being used for various space vehicle applications such as launch vehicles, orbital vehicles, and re-entry vehicles. This paper describes current space vehicle navigation capabilities. The SIGI is being enhanced to provide additions to these existing capabilities with such items as higher processing and a commercial-off-the-shelf operating system. This will allow hosting of various software applications such as advanced navigation functions, flight control, guidance and vehicle management algorithms. The SIGI can host redundancy management functions by incorporating a cross channel data link card (CCDL) using a high speed firewire bus. The SIGI can then be used as a redundancy management platform which has application to current space vehicle avionics topologies incorporating distributed processing architectures     

Radiation measurements aboard NASA ER-2 high altitude aircraft with the Liulin-4J portable spectrometer.

The risks to aircrew health posed by prolonged exposure to low levels of ionizing radiation at aircraft altitudes have recently received renewed attention. Civil and military aircraft currently on the drawing board are expected to operate at higher altitudes (>12 km) and fly longer ranges than do existing aircraft, thereby exposing their crews to higher levels of ionizing radiation, for longer periods of time. We are currently carrying out dosimetric measurements of the ionizing radiation environment at approximately 20 km altitude using portable Si detectors aboard NASA's two ER-2 high altitude research aircraft. The instruments, Liulin-4J, have been extensively calibrated at several particle accelerators. With these instruments, we can measure not only absorbed dose, but also variation of the absorbed dose as a function of time. We report radiation dose measurements as function of time, altitude, and latitude for several ER-2 missions.     

Atmospheric dynamics in the "Laboratory Biosphere" with wheat and sweet potato crops.

Laboratory Biosphere is a 40-m3 closed life system equipped with 12,000 W of high pressure sodium lamps over planting beds with 5.37 m2 of soil. Atmospheric composition changes due to photosynthetic fixation of carbon dioxide and corresponding production of oxygen or the reverse, respiration, are observed in short timeframes, e.g., hourly. To focus on inherent characteristics of the crop as distinct from its area or the volume of the chamber, we report fixation and respiration rates in mmol h-1 m-2 of planted area. An 85-day crop of USU Apogee wheat under a 16-h lighted/8-h dark regime peaked in fixation rate at about 100 mmol h-1 m-2 approximately 24 days after planting. Light intensity was about 840 micromoles m-2 s-1. Dark respiration peaked at about 31 mmol h-1 m-2 at the same time. Thereafter, both fixation and respiration declined toward zero as harvest time approached. A residual soil respiration rate of about 1.9 mmol h-1 m-2 was observed in the dark closed chamber for 100 days after the harvest. A 126-day crop of Tuskegee TU-82-155 sweet potato behaved quite differently. Under a 680 micromoles m-2 s-1, 18-h lighted/6-h dark regime, fixation during lighted hours rose to a plateau ranging from about 27 to 48 mmol h-1 m-2 after 42 days and dark respiration settled into a range of 12-23 mmol h-1 m-2. These rates continued unabated until the harvest at 126 days, suggesting that tuber biomass production might have continued at about the same rate for some time beyond the harvest time that was exercised in this experiment. In both experiments CO2 levels were allowed to range widely from a few hundred to about 3000 ppm, which permitted observation of fixation rates both at varying CO2 concentrations and at each number of days after planting. This enables plotting the fixation rate as a function of both variables. Understanding the atmospheric dynamics of individual crops will be essential for design and atmospheric management of more complex CELSS which integrate the simultaneous growth of several crops as in a sustainable remote life support system.     

Ultra triple-junction high-efficiency solar cells

Solar cells suitable for the space environment must combine high-efficiency, high energy density, and radiation hardness in a manufacturable design. As improvement in one performance parameter usually results in degradation in one or more of the remaining parameters, careful optimization is required to enhance overall performance. The ultra triple-junction cell developed builds upon the established success of the fully qualified improved triple-junction cell currently in production. In the ultra triple-junction cell configuration, improved robustness and efficiency after radiation exposure augment a cell design expected to deliver 28% beginning-of-life efficiency in production.     

High phosphorylase activity is correlated with increased potato minituber formation and starch content during extended clinorotation.

The major purpose of these experiments were to investigate growth of potato storage organs and starch synthesis in minitubers at slow horizontal clinorotation (2 rpm), which partly mimics microgravity, and a secondary goal was to study the activity and localization of phosphorylase (EC 2.4.1.1) in storage parenchyma under these conditions. Miniplants of Solanum tuberosum L. (cv Adreta) were grown in culture for 30 days for both the vertical control and the horizontal clinorotation. During long-term clinorotation, an acceleration of minituber formation, and an increase of amyloplast number and size in storage parenchyma cells, as well as increased starch content, was observed in the minitubers. The differences among cytochemical reaction intensity, activity of phosphorylase, and carbohydrate content in storage parenchyma cells of minitubers grown in a horizontal clinostat were established by electron-cytochemical and biochemical methods. It is shown that high phosphorylase activity is correlated with increased starch content during extended clinorotation. The results demonstrate the increase in carbohydrate metabolism and possible accelerated growth of storage organs under the influence of microgravity, as mimicked by clinorotation; therefore, clinorotation can be used as a basis for future studies on mechanisms of starch synthesis under microgravity.     

Effects of RF absorbers on measurements of small antennas in smallanechoic chambers

In this work, the influence of resistive absorbers in the vicinity of small antennas was investigated, in order to define a lower limit for the size of a small anechoic chamber for antenna calibration and radiation pattern measurements, with respect to the distance between the antenna under test (AUT) and the RF absorbers lining the walls. Furthermore, the influence of a relatively narrow transmission channel, formed by the absorbers on the side walls between the measurement antenna and the AUT was investigated. It was found by measurements that absorbers with the length of 610 mm do not have a measurable effect on the radiation characteristics of a small antenna at around 1.8 GHz, as long as they are kept more than 100 mm from the AUT, and the transmission channel formed by the absorbers between the antennas is wider than 100 mm