Apollo 11 Reloaded: Optimization-based Trajectory Reconstruction

This paper wants to be a tribute to the Apollo 11 mission, that celebrated its 50th anniversary in 2019. By using modern methods based on numerical optimization we reconstruct critical phases of the original mission, and more specifically the ascent of the Saturn V, the translunar injection maneuver that allowed the crew to leave the Earth’s sphere of influence, and the Moon landing sequence, starting from the powered descent initiation. Results were computed by employing pseudospectral methods, and show good agreement with the original post-flight reports released by NASA after the successful completion of the mission

Comparing Notes: Recording and Criticism

This chapter charts the ways in which recording has changed the nature of music criticism. It both provides an overview of the history of recording and music criticism, from the advent of Edison’s Phonograph to the present day, and examines the issues arising from this new technology and the consequent transformation of critical thought and practice

Wider Still and Wider: British Music Criticism since the Second World War

This chapter provides the first historical examination of music criticism in Britain since the Second World War. In the process, it also challenges the simplistic prevailing view of this being a period of decline from a golden age in music criticism

Iconoclasts - a book of dramatists

vii,430 ha

Natural Gas Production and CO2 Sequestration in a Class 2 Hydrate Accumulation: A Numerical Simulation Study

Large amounts of natural gas hydrates have been found in sub-oceanic deposits and beneath permafrost regions. It has the potential to become a major hydrocarbon resource in the near future. Research is needed to evaluate the production possibilities of this new resource. CH4 hydrate dissociation and production is an endothermic process and a production challenge is the reservoir temperature reduction. CO2 is thermodynamically favoured over CH4 in the hydrate form and it has been suggested to use CO2 to prevent cooling by replacement of CH4 hydrates with CO2 hydrates. This technique has three advantages: sequestration of CO2, increased CH4 production and maintaining formation stability. The effect of CO2 injection on the CH4 production from a hydrate reservoir has been investigated by numerical simulations. A sensitivity analysis on the CH4 production has been performed by varying the injection pressure, temperature, reservoir properties, hydrate blockage models, intrinsic kinetic rates for CO2 hydrate formation and numerical parameters. The research has been performed by running numerical simulations using the kinetic simulator STARS from CMG. A 3D homogeneous class 2 hydrate reservoir was constructed with a production well completed in the hydrate zone and an injection well completed in the free water zone, injecting liquid CO2 in the free water zone below the CH4 hydrate zone. The injection and production well pressure were regulated to create CO2 hydrate forming and CH4 hydrate dissociation conditions in the reservoir. The simulation results have shown that when CO2 is injected, the cumulative CH4 production can increase with 50-60 %, while storing significant amounts of CO2 simultaneously. 2 % of the injected CO2 was produced at the production well. CO2 hydrates were formed directly under the CH4 hydrates, supplying the dissociating CH4 hydrates with a low grade heat source. No upward moving front of CO2 was observed. It is concluded that CO2 injection only increases CH4 production when the temperature of the reservoir is too low to support further hydrate dissociation. The highest recovery rates are achieved with low injection pressures. Injection of CO2 in the gas phase is favoured and the intrinsic kinetic formation rate for CO2 hydrates is a major influence on the CH4 production. It is concluded that CO2 injection in a Class 2 hydrate reservoir could increase the CH4 production under certain conditions.Petroleum EngineeringGeotechnologyCivil Engineering and Geoscience