The stretched lens array (SLA) [spacecraft solar power]

At IECEC 2001, this team presented a paper on the new stretched lens array (SLA), including its evolution from the successful SCARLET array on the NASA/JPL Deep Space 1 spacecraft. Since that conference, the SLA team has made significant advances in SLA technology, including component-level improvements, array-level optimization, space environment exposure testing, and prototype hardware fabrication and evaluation. This paper describes the evolved version of the SLA, highlighting recent improvements in the lens, solar cell, photovoltaic receiver, rigid panel structure, and complete solar array wing. In addition to excellent durability in the space environment, the near-term SLA will provide outstanding wing-level performance parameters: 180 W/kg specific power; 300 W/m/sup 2/ power density; 300 V operational voltage; 85% savings in cell area (cm/sup 2//W) and cell-related cost ($/W) compared to planar arrays; 9 kW/m/sup 3/ stowed power at launch.     

Optical fiber wavelength division multiplexing

During flight, aircraft avionics transmit and receive RF signals to/from antennas over coaxial cables. As the density and complexity of onboard avionics increases, the electromagnetic interference (EMI) environment degrades proportionately, leading to decreasing signal-to-noise ratios (SNRs) and potential safety concerns. The coaxial cables are inherently lossy, limiting the RF signal bandwidth while adding considerable weight. To overcome these limitations, we have investigated a fiber optic communications link for aircraft that utilizes wavelength division multiplexing (WDM) to support the simultaneous transmission of multiple signals (including RF) over a single optical fiber. Optical fiber has many advantages over coaxial cable, particularly lower loss, greater bandwidth, and immunity to EMI. In this paper, we demonstrate that WDM can be successfully used to transmit multiple RF signals over a single optical fiber with no appreciable signal degradation. We investigate the transmission of FM and AM analog modulated signals, as well as FSK digital modulated signals, over a fiber optic link (FOL) employing WDM. We present measurements of power loss, delay, SNR, carrier-to-noise ratio (CNR), total harmonic distortion (THD), and bit error rate (BER). Our experimental results indicate that WDM is a fiber optic technology suitable for avionics applications.     

Pilot CELSS based on a maltose-excreting Chlorella: concept and overview on the technological developments.

A typical ecosystem is composed of three compartments: photosynthetic producer (anabolizing processes), consumer and decomposer (catabolizing processes). It is still far too much complex, however, to form the basis on which establishing an engineered artificial ecosystem, dedicated to support life (of the consumer) in space. A simpler, two compartments, pilot model to start with has been selected. It is based on a symbiotic Chlorella (strain 241.80), which can be tuned, at low pH, to produce maltose. This feature prevents the accumulation of useless biomass, not readily edible by the consumer. Being excreted, maltose is easily recoverable, and constitutes a direct source of carbon suitable for many consumers. Since they will totally catabolize it back to CO2, the necessity for a decomposer compartment is avoided. The present status of the technological concept designed to support life of small consumers (animals, microorganisms) will be presented, taking into account the space compatibility of the technologies developed.     

Earth applications of closed ecological systems: relevance to the development of sustainability in our global biosphere.

The parallels between the challenges facing bioregenerative life support in artificial closed ecological systems and those in our global biosphere are striking. At the scale of the current global technosphere and expanding human population, it is increasingly obvious that the biosphere can no longer safely buffer and absorb technogenic and anthropogenic pollutants. The loss of biodiversity, reliance on non-renewable natural resources, and conversion of once wild ecosystems for human use with attendant desertification/soil erosion, has led to a shift of consciousness and the widespread call for sustainability of human activities. For researchers working on bioregenerative life support in closed systems, the small volumes and faster cycling times than in the Earth's biosphere make it starkly clear that systems must be designed to ensure renewal of water and atmosphere, nutrient recycling, production of healthy food, and safe environmental methods of maintaining technical systems. The development of technical systems that can be fully integrated and supportive of living systems is a harbinger of new perspectives as well as technologies in the global environment. In addition, closed system bioregenerative life support offers opportunities for public education and consciousness changing of how to live with our global biosphere.     

The accuracy of ionogram-derived N(h) profiles

At the Millstone Hill station the Incoherent Scatter Radar (ISR) and a Digisonde 256 are simultaneously operating. Some characteristic true heights determined by both instruments are compared with each other, possible reasons for observed difference are indicated.     

Decision fusion analysis detects spiral bevel gear damage

A diagnostic tool for detecting damage to spiral bevel gears was developed. Two different monitoring technologies - oil debris analysis and vibration were integrated using data fusion into a health monitoring system for detecting surface fatigue pitting damage on gears. This integrated system showed improved detection and decision-making capabilities as compared to using individual monitoring technologies. This diagnostic tool was evaluated by collecting vibration and oil debris data from fatigue tests performed in the NASA Glenn Spiral Bevel Gear Fatigue Rigs. Data was collected during experiments performed in this test rig when pitting damage occurred. Results show that combining the vibration and oil debris measurement technologies improves the detection of pitting damage on spiral bevel gears.     

A Modification of the Method of Transporting Trajectory

Further development of an approximate method for optimizing a flight with an ideally controlled small thrust is proposed. The method is based on the employment of the transporting trajectory and considered in [1–3]. A detailed analysis of the means of improving the accuracy of this method suggested in [2, 3] is carried out, and the solution is presented in finite form. The proposed approach is applied to the flights making flybys of many celestial bodies. In the case of small bodies the solution is also obtained in finite form. A numerical example is considered confirming the high efficiency of this method.     

Magnifying our world: Why we must extend civilization to the Moon

Since the completion of its original prehistoric migration some 10 000 years ago, humankind has had nowhere else on Earth to go. The Space Age has produced the wherewithal for a new off-Earth human migration to restart, with the Moon as the clear initial destination. As insurance against cataclysmic and human-induced natural disasters, as a means of creating new commercial industrial–financial opportunities at a time of fundamental change in the global economy, and as a way for the USA to regain some international political influence, it should pursue Moon settlement vigorously and soon. However, the developing US space exploration program being designed by NASA for such an undertaking is too narrowly confined to the pursuit of natural-science objectives. There must be fundamental involvement of the private sector and of a much wider range of professionals and federal departments therein.     

The Climate Response to the Astronomical Forcing

Links between climate and Earth’s orbit have been proposed for about 160 years. Two decisive advances towards an astronomical theory of palæoclimates were Milankovitch’s theory of insolation (1941) and independent findings, in 1976, of a double precession frequency peak in marine sediment data and from celestial mechanics calculations. The present chapter reviews three essential elements of any astronomical theory of climate: (1) to calculate the orbital elements, (2) to infer insolation changes from climatic precession, obliquity and eccentricity, and (3) to estimate the impact of these variations on climate. The Louvain-la-Neuve climate-ice sheet model has been an important instrument for confirming the relevance of Milankovitch’s theory, but it also evidences the critical role played by greenhouse gases during periods of low eccentricity. It is recognised today that climatic interactions at the global scale were involved in the processes of glacial inception and deglaciation. Three examples are given, related to the responses of the carbon cycle, hydrological cycle, and the terrestrial biosphere, respectively. The chapter concludes on an outlook on future research directions on this topic.