Technical review of the Laboratory Biosphere closed ecological system facility.

Laboratory Biosphere is a 40 m3 closed life system that commenced operation in May 2002. Light is from 12,000 W of high pressure sodium lamps over planting beds with 5.37 m2 of soil. Water is 100% recycled by collecting condensate from the temperature and humidity control system and mixing with leachate collected from under the planting beds. Atmospheric leakage was estimated during the first closure experiment to be 0.5-1% per day in general plus about 1% for each usage of the airlock door. The first trial run of 94 days was with a soybean crop grown from seeds (May 17, 2002) to harvest (August 14, 2002) plus 5 days of post-harvest closure. The focus of this initial trial was system testing to confirm functionality and identify any necessary modifications or improvements. This paper describes the organizational and physical features of the Laboratory Biosphere.     

Thermionic/AMTEC cascade converter concept for high-efficiencyspace power

This paper presents trade studies that address the use of the thermionic/AMTEC cell-a cascaded, high efficiency, static power conversion concept that appears well-suited to space power applications. Both the thermionic and AMTEC power conversion approaches have been shown to be promising candidates for space power. Thermionics offers system compactness via modest efficiency at high heat rejection temperatures, and AMTEC offers high efficiency at modest heat rejection temperature. From a thermal viewpoint, the two are ideally suited for cascaded power conversion: thermionic heat rejection and AMTEC heat source temperatures are essentially the same. In addition to realizing conversion efficiencies potentially as high as 35-40% such a cascade offers the following perceived benefits: Survivability-capable of operation in the Van Allen belts; Simplicity-static conversion, no moving parts; Long lifetime-no inherent life-limiting mechanisms identified; Technology readiness-Large thermionic database; AMTEC efficiencies of 18% currently being demonstrated, with more growth potential available; and Technology growth-applicable to both solar thermal and reactor-based nuclear space power systems. Mechanical approaches and thermal/electric matching criteria for integrating thermionics and AMTEC into a single conversion device are described. Focusing primarily on solar thermal space power applications, parametric trends are presented to show the performance and cost potential that should be achievable with present-day technology in cascaded thermionic/AMTEC systems     

Dynamical magnetic reconnection in Parker''s coronal heating model

The excitation (flares, ejections, heating, …) of the corona can be understood in terms of the dynamics of the confectively driven magnetized plasma. In particular, anomalous ohmic heating may be a consequence of the formation and rapid dissipation of small-scale magnetic fields in the corona. We have performed numerical simulations of the loop heating model proposed by Parker (1972, 1994), and have studied its dynamics and global power balance in order to assess its viability as a coronal heating candidate, with promising results. Our results suggest the following view of the small-scale dynamics of coronal loops. First of all, photospheric granular motions quasi-statically twist the magnetic field of the corona in a random-walk fashion. In topologically closed structures, the perpendicular magnetic energy increases, causing magnetic shear to build up at the quasi-separatrices of the resulting close-packed magnetic flux tubes. At some point, the boundary driving causes this stressed configuration to cross the threshold of an ideal time-scale MHD instability (possibly magnetic coalescence or resistive tearing) or a point of nonequilibrium and the field lines pinch toward a small-scale sheared configuration. It then becomes energetically favorable for dynamic reconnection to occur, producing narrow current sheets and an Ohmic heating rate sufficient to balance the input Poynting flux.     

GHRS observations of the LISM

The GHRS has obtained high-resolution spectra of interstellar gas toward 19 nearby stars. These excellent data show that the Sun is located inside the Local Interstellar Cloud (LIC) with other warm clouds nearby. I will summarize the physical properties of these clouds and the three-dimensional structure of this warm interstellar gas. There is now clear evidence that the Sun and other late-type stars are surrounded by hydrogen walls in the upwind direction. The D/H ratio probably has a constant value in the LIC, (1.6 ± 0.2) × 10^–5, consistent with the measured values for all LIC lines of sight.     

Dynamics and evolution of the post-flare loops of June 1992

Observations in X-rays (Yohkoh/SXT) and in H of a system of post-flare loops which developed after a flare on 25 June 1992 provide a unique set of data for a study of the relationship between the hot and cool post-flare loops as they evolve. Through a study of the magnetic configuration in which the flare occurred, we are able to reconstruct the true, 3D geometry of the loops. We derive the bulk-flow velocities along the loop as a function of height using Doppler velocities and the results from the loop reconstruction. We also provide a set of relative altitude data. These results are used to check the validity of the reconnection model in the frame of the cooling time needed to cool X-ray loops to H temperature.     

Middle-atmosphere tides: Recent advances in theory and observation

Recent progress in the theoretical and observational investigation of middle atmosphere tides is reviewed. Theoretical advances include development of more realistic thermal excitation and numerical simulation models, investigation of seasonal — latitudinal and longitudinal variations in tidal structures, and the origin and effects of ‘unsteadiness’ in tidal oscillations over periods of days. Recent analyses of middle latitude radar data between 80 Km and 130 Km delineate consistent seasonal phase patterns in this region. Analyses of rocket data show stratosphere and lower mesosphere tides to be characterized by smaller amplitudes, shorter vertical scales, greater unsteadiness, and greater spatial variability than exhibited in the upper mesosphere and above. Results from the first two ATMAP (Atmospheric Tides Middle Atmosphere Program) campaigns are also discussed.     

Development of the Primary Sorption Pump for the SEIS Seismometer of the InSight Mission to Mars

We report on the development of a passive sorption pump, capable of maintaining high-vacuum conditions in the InSight seismometer throughout the duration of any extended mission. The adsorber material is a novel zeolite-loaded aerogel (ZLA) composite, which consists of fine zeolite particles homogeneously dispersed throughout a porous silica network. The outgassing species within the SEIS evacuated container were analyzed and the outgassing rate was estimated by different methods. The results were used to optimize the ZLA composition to adsorb the outgassing constituents, dominated by water, while minimizing the SEIS bakeout constraints. The InSight ZLA composite additionally facilitated substantial CO₂ adsorption capabilities for risk mitigation against external leaks in Mars atmosphere. To comply with the stringent particle requirements, the ZLA getters were packaged in sealed containers, open to the SEIS interior through \(1~\upmu\mbox{m}\)-size pore filters. Results from experimental validation and verification tests of the packaged getters are presented. The pressure forecast based on these data, corroborated by rudimentary in situ pressure measurements, infer SEIS operational pressures not exceeding \(10^{-5}~\mbox{mbar}\) throughout the mission.