Trade-off study on deorbiting S/C in near polar orbit

Usual long, flexible, ED tethers kept vertical by the gravity gradient might be less efficient for deorbiting S/C in near-polar orbits than conventional (Hall, Ion) electrical thrusters. A trade-off study on this application is here presented for tethers kept horizontal and perpendicular to the orbital plane. A tether thus oriented must be rigid and short for structural reasons, requiring a non-convex cross section and a power supply as in the case of electrical thrusters. Very recent developments on bare-tether collection theory allow predicting the current collected by an arbitrary cross section. For the horizontal tether, structural considerations on length play the role of ohmic effects in vertical tethers, in determining the optimal contribution of tether mass to the overall deorbiting system. For a given deorbiting-mission impulse, tether-system mass is minimal at some optimal length that increases weakly with the impulse. The horizontal-tether system may beat both the vertical tether and the electrical thruster as regards mass requirements for a narrow length range centered at about 100 m, allowing, however, for a broad mission-impulse range.

Potential Adverse Effects of the Alaska Natural Gas Pipeline on Arctic Caribou and Proposed Mitigation

The Alaska Natural Gas Pipeline (ANGP) is proposed for construction on the North Slope in 2016. It will be aligned through Arctic caribou habitat and evidence shows that caribou are negatively affected by human development. This Capstone identifies potential adverse affects of ANGP on Arctic caribou using interviews from expert caribou biologists and the 1977 Trans-Alaska Pipeline System (TAPS) as a model. Based on a synthesis of the interviews and TAPS analysis, this capstone proposes and examines a set of seventeen conservation measures to be implemented during construction and operation of ANGP to minimize adverse impacts on caribou herds. These conservation measures can be used as a baseline for future developments on the North Slope to promote caribou herd management.

Effects of landscape spatial heterogeneity on dryland restoration success. The combined role of site conditions and reforestation techniques in southeastern Spain

In occidental Europe, Spain is one of countries the most severely affected by desertification (Arnalds & Arsher 2000). Particularly, South-eastern Spain is considered as one of the most threatened areas by desertification in Mediterranean Europe (Vallejo 1997). In 2003, the Valencia Regional Forest Service implemented a restoration demonstration project in this area. The project site is a small catchment (25 ha) located in the Albatera municipality. The catchment is highly heterogeneous, with terraced slopes, south-facing slopes and north-facing slopes. The restoration strategy was based on planting evergreen trees and shrubs which can grow quickly after disturbances, and on field treatments aimed at maximizing water collection (micro-catchments, planting furrows), organic amendment (compost), and conservation (tree shelters, mulching). On south landscape unit, the whole category of restoration treatments was applied: water micro-catchment + Tubex tree shelters + mulching & compost, while on north landscape unit: netting tree shelters + mulching & compost only were applied, while in terrace landscape unit: furrows + netting tree shelters + mulching & compost were applied. Survival and growth of the planted seedlings were used as metrics of restoration success. To assess the effects of the treatments applied for soil conservation, soil loss rates (from 2005 to 2009) were evaluated using the erosion pin method. We conclude that, despite the limiting conditions prevailing on the south unit, this landscape unit showed the highest survival and growth plant rates in the area. The best seedling performances on the south landscape unit were probably due to the highest technical efforts applied, consisting in the water micro-catchment installation and the Tubex plant shelters addition. In addition, soil loss rates followed decreasing trends throughout the assessment period. Soil loss rates were highest on south landscape unit in comparison with the other landscape units, due to the more accentuated relief. North landscape unit and terrace unit showed a net soil mass gain, probably reflecting the trapping of sediments produced by plantation works.

Gazprom's position on the Russian gas market weakening. OSW Commentary No. 70, 2012-02-23

As the difficulties Gazprom has faced in recent years on the European market have multiplied1, so more and more symptoms have appeared which may suggest that the company’s dominant position is deteriorating. The decision made by the Russian government in June 2011 to double the tax Gazprom has to pay on the extraction of gas, which was later approved by parliament, was the first time in many years when the company’s fiscal privileges were withdrawn. The process of Gazprom’s assets being taken over by private companies and business partners from within Vladimir Putin’s closest circle is underway. More and more frequently attempts are being made to challenge the company’s monopoly in areas of key importance for the functioning of the entire gas sector, such as Gazprom’s exclusive right to dispose of the Russian gas transportation system and its exports monopoly. Competition from independent gas producers on the domestic market is growing, and Gazprom is gradually being pushed out of some of that market’s most profitable segments (industrial clients). The emerging tendencies in the Russian gas sector derive from a number of factors – from the situation on the European gas market, through difficulties hampering the development of the sector in Russia itself, to the private interests of the current ruling class and its business partners. The plans for a structural reform of the monopoly (including isolating gas transportation system from Gazprom), presented since 2000 by the Ministry for Economic Development and since 2003 by the Russian Association of Industrialists and Entrepreneurs (RSPP), suggest a direction for the changes necessary to stimulate the sector’s development and improve the efficiency of Gazprom itself. However, the monopolist’s current business model gives the government full control over this strategic enterprise, which is a core of Putin’s concept for developing Russia as a global energy power. Despite Putin’s recent statement that he “does not rule out privatising Gazprom in the future” (made at a meeting with political scientists in Moscow on 6 February this year), any structural reform of Gazprom (and consequently, a weakening of the state’s control over it) seems unlikely in the foreseeable future. Still, the developments on the domestic market – growing pressure from other gas companies (oil corporations and independent producers) and changes on the European market2 – may result in the weakening of Gazprom’s monopoly privileges and a gradual deterioration of its special status within Russia.