Power requirements for commercial communications spacecraft

Historical data on commercial spacecraft power systems are presented and their power requirements to the growth of satellite communications channel usage are related. Some approaches for estimating future power requirements of this class of spacecraft through the year 2000 are proposed. The key technology drivers in satellite power systems are addressed. Several technological trends in such systems are described, focusing on the most useful areas for research and development of major subsystems, including solar arrays, energy storage, and power electronics equipment

Synchronous orbit power technology needs

The needs are defined for future geosynchronous orbit spacecraft power subsystem components, including power generation, energy storage, and power processing. A review of the rapid expansion of the satellite communications field provides a basis for projection into the future. Three projected models, a mission model, an orbit transfer vehicle model, and a mass model for power subsystem components are used to define power requirements and mass limitations for future spacecraft. Based upon these three models, the power subsystems for a 10 kw, 10 year life, dedicated spacecraft and for a 20 kw, 20 year life, multi-mission platform are analyzed in further detail to establish power density requirements for the generation, storage and processing components of power subsystems as related to orbit transfer vehicle capabilities. Comparison of these requirements to state of the art design values shows that major improvements, by a factor of 2 or more, are needed to accomplish the near term missions. However, with the advent of large transfer vehicles, these requirements are significantly reduced, leaving the long lifetime requirement, associated with reliability and/or refurbishment, as the primary development need. A few technology advances, currently under development, are noted with regard to their impacts on future capability

Directed evolution of synthetic coexistence:A new path towards ecosystem design?

In nature, microorganisms never live alone but rather build interconnected communities, able to perform complex biochemical tasks that are essential to the function of most of earth’s ecosystems. By comparison, the microorganisms we rely on as chassis for synthetic biology lead relatively simple, isolated lives. However, mimicking the natural complexity of microbiomes can help synthetic biologists realize more advanced functionalities; e.g. as shown for the efficient biosynthesis of oxygenated taxanes (precursors of the antitumor agent paclitaxel) in a two-species ecosystem (1)

Moving towards chemical-free agriculture, 37 kb at a time

Domestic crop plants are modern marvels of extensive breed- ing; however, many of their natural defenses against pests and pathogens have been lost. Wild relatives still harbor disease re- sistance genes, but transferring these large sequences into com- plex, polyploid plant genomes calls for advanced genomic engineering technologies. Recently, government researchers in Australia, successfully transferred a 37 kb resistance stack into the genome of a domesticated wheat species such that it is pro- tected against the rapidly evolving wheat leaf rust pathogen Puccinia graminis f. sp. tritici (Pgt) without losing any agronomic feature

A computational walk to the hidden peaks of protein performance

Spiders use them to catch their prey, plants rely on them to fix carbon and mammals need them for eye vision—proteins. Proteins play critical roles in nature, and not surprisingly, synthetic biologists heavily rely on their functional diversity to build new therapeutics (1), catalysts (2) and materials (3). But natural proteins are rarely optimal for their envisioned human uses. They rather need to be engineered to enhance their per- formance. Recently, researchers introduced a machine-learning guided paradigm that can predict which mutations in a pro- tein will enhance function with only 24 functional data sets as input (4). This paradigm could significantly accelerate the engi- neering of improved proteins for medicine, food, agriculture and industrial applications

Self-growing environmentally responsive houses made from agricultural waste and fungal mycelia

Mix the ingredients, pour them into a tin, and ‘bake’ at ambi- ent temperature for 5 days. What sounds like instructions for a ready-made baking mix could soon become a way to grow your own home—or emergency shelter needed after a natural disaster (1)

Synthetic biological toggle circuits that respond within seconds and teach us new biology

Imagine it would take several minutes or even hours for your light bulb to turn on after you hit the switch—not very useful for many daily (and nightly) activities. Light switches are made from the so-called toggle switches; basic and widely used electrical components that provide binary on–off control over electrical circuits, allowing quick decision- making and memory. Synthetic biologists have built analogues genetic toggle switches but until now those only responded in time-ranges of minutes to hours, limiting their use in applica- tions that require real-time action. Mishra et al. have recently built a biological bistable toggle switch in yeast that responds within seconds by mimicking nature’s way of rapid response generation (1). Synthetic biologists envision to control cellular behavior by engineering biology in analogy to electrical circuits. Implement- ing a synthetic biological toggle switch was thus one of the early achievements of the field (2). While, over the last two decades, synthetic biologists have mastered to build toggle switches that respond to various inputs—chemicals, light or temperature—and show high switching robustness (3); one challenge remained: timing

No action without talk? UN peacekeeping, discourse, and institutional self-legitimation

In this article, I argue that much of the discourse observable within the UN constitutes neither unnecessary and unproductive ‘talk’ nor efforts to convince outside audiences of its legitimacy, but actually a form of institutional self-legitimation that is key to its ability to function. Using the case of the UN’s Department of Peacekeeping Operations (DPKO), I show that because the organization has a multifaceted organizational identity, it faces situations where it is forced to choose between multiple but equally appropriate courses of action, and it uses self-legitimation alongside other mechanisms to overcome these tensions. I specify three sets of circumstances in which this occurs, showing how DPKO uses discourse that simplifies and exceptionalizes in a bid to reconcile or downplay these contradictions and reassert a cohesive and legitimate organizational identity internally. This simplification and exceptionalization in turn serve an enabling function, allowing DPKO to continue operating in conditions of complexity by decreasing risk aversion and instilling a deep sense of professional loyalty in staff. At the same time, such discursive processes are costly and may entrench inefficient practices, rendering the effects of self-legitimizing discourse paradoxical: they may enable action, but they reduce the efficiency and effectiveness of that action